defence research studies

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Introduction

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Defence studies is a multi-disciplinary field examining how agents, predominantly states, prepare for, prevent, avoid and/or engage in armed conflict. Where security studies has been broadened and stretched to cover at times the near totality of international and domestic affairs and war studies has come to mean not just operations and tactics but also experiences and outcomes, defence studies remains a coherent area of study primarily aimed at how defence policy changes over time and in relation to stimulating factors such as changes in power, strategy and technology. Largely emanating from the United Kingdom in the twentieth century, the term defence studies goes back to the establishment of the Imperial Defence College in 1927, later named the Royal College for Defence Studies in 1970. Since this point, defence studies has become an intellectual pursuit designed to build our understanding of the convergence of war with other fields that impact the proclivity and intensity of battle. Defence studies help us to see how martial force is understood, built and deployed.

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1st Edition

Research Methods in Defence Studies A Multidisciplinary Overview

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Description

This textbook provides an overview of qualitive and quantitative methods used in different social sciences to investigate defence issues. Recently, defence issues have become of increasing interest to researchers in the social sciences, but they raise specific methodological questions. This volume intends to fill a gap in the literature on defence studies by addressing a number of topics not dealt with sufficiently before. The contributors offer a range of methodological reflections and tools from various social sciences (political science, sociology, geography, history, economics and public law) for researching defence issues. They also address the increasingly important question of data and digitalization. The book introduces the added value of quantitative and qualitative methods, and calls for a cross-fertilization of methods in order to facilitate better research on defence topics and to fully grasp the complexity of defence in the 21st century. This book will be of much interest to students, researchers and practitioners of defence studies, war studies, military studies, and social science research methods in general.

Table of Contents

Delphine Deschaux-Dutard is an Associate Professor in Political Science at the University Grenoble Alpes, France. She is also a researcher at CESICE and Vice-Dean for International Relations at the Faculty of law at the same institution.

Critics' Reviews

'If you still believe the old canard that defence studies are lacking in rigor or merely policy analysis about "bombs and bullets", think again. Delphine Deschaux-Dutard and her contributors pointedly show that this stereotype is not to be taken seriously. They take us on a lively journey through a wide range of indispensable methodological tools, both qualitative and quantitative, to study defence issues rigorously. Research Methods in Defence Studies will be a reference for scholars and students of defence and equally useful to practitioners who need the right methods to grasp the complexity of their rapidly changing profession. The interdisciplinary breath of the book alone is worth the price of admission.' -- Pascal Vennesson, Professor of Political Science, S. Rajaratnam School of International Studies, Nanyang Technological University 'There is now a very rich academic literature in the social sciences on warfare and the armed forces in the early twenty-first century. However, although a diversity of methods have been used by scholars in this field, there has been no systematic attempt to interrogate the methodology of military inquiry. This indispensable and comprehensive volume now fills that gap. It explores in vivid detail a variety of methodologies across the disciplines from geography, law to sociology. It will be required reading for any serious student of military affairs .' -- Professor Anthony King, Chair in War Studies, University of Warwick 'This reviewer would highly recommend this book to anyone in the field of defence studies. It is simple and engaging enough to hold the attention of first-year university students. It is detailed enough to benefit seasoned academicians. Perhaps most useful, it is practical enough to benefit those in the defence industry. '-- Jeremy Lamoreaux, Defence Studies, Vol. 21(3)

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Defense Strategy and Capabilities

The International Security Program and the Arleigh A. Burke Chair in Strategy lead CSIS’s defense strategy portfolio, including the global military balance, asymmetric warfare, and regional conflicts.

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How China Could Quarantine Taiwan: Mapping Out Two Possible Scenarios

There are worrying signs that China is training its forces to be able to conduct a law enforcement–led “quarantine” of Taiwan. This report lays out China’s potential motivations for a quarantine and maps out two plausible scenarios of how it could conduct operations.

Brief by Bonny Lin, Brian Hart, Matthew P. Funaiole, Samantha Lu, and Truly Tinsley — June 5, 2024

Unpacking China’s Naval Buildup

Commentary by Alexander Palmer, Henry H. Carroll, and Nicholas Velazquez — June 5, 2024

Cooperation on Scientific Innovation, Supply Chains, and Geopolitical Risk in Northeast Asia

Report by Seth G. Jones, Park In-kook, Cynthia Cook, John J. Lee, and Gregory Sanders — May 31, 2024

Operations in the Red Sea: Lessons for Surface Warfare

Transcript — May 14, 2024

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Preserving the Free Flow of Commerce in the Red Sea and Beyond: An Update from FIFTH Fleet Commander VADM George Wikoff, USN

CSIS and the U.S. Naval Institute are excited to host VADM George Wikoff, USN, FIFTH Fleet Commander, on August 7, 2024, at 10:00 a.m. for a Maritime Security Dialogue event on preserving the free flow of commerce in the Red Sea and across the globe.

Event — August 7, 2024

CSIS-DAPA 2024: The Potential for Expanding Defense Cooperation within the ROK-U.S. Alliance

Join the CSIS Defense-Industrial Initiatives Group for CSIS-DAPA 2024: The Potential for Expanding Defense Cooperation within the ROK-U.S. Alliance which will feature keynotes from ROK DAPA Minister Seok, JongGun and U.S. ASA(ALT) Hon. Douglas R. Bush.

Event — June 27, 2024

Understanding the Growing Collaboration Between Russia and Iran

This week, Max sat down for a public conversation with Hanna Notte and Jon B. Alterman to discuss how the governments of Russia and Iran have strengthened their political, economic, and security collaboration since the launch of Russia's full-scale invasion of Ukraine in 2022.

Podcast Episode by Max Bergmann, Jon B. Alterman, and Hanna Notte — June 14, 2024

Please join the CSIS International Security Program on Tuesday, June 11 at 12:00 p.m. for a conversation with General Frank McKenzie about his book, The Melting Point: High Command and War in the 21st Century.

Event — June 11, 2024

Already the world's largest navy, the People's Liberation Army Navy is positioned to overtake the U.S. Navy in several indicators of naval power within ten years.

An audio version of “Unpacking China’s Naval Buildup,” a new commentary by CSIS’s Alexander Palmer, Henry Carroll, Nicholas Velazquez. This audio was generated with text-to-speech by Eleven Labs. 

Podcast Episode by Alexander Palmer, Henry H. Carroll, and Nicholas Velazquez — June 5, 2024

Through an analysis of three technology clusters—semiconductors, electronic vehicle batteries, and biotechnology—this report assesses risks and opportunities for the future of United States-Republic of Korea cooperation.

Please join the CSIS International Security Program for a conversation with RADM Fred Pyle, Director, Surface Warfare Division, N96, Office of the Chief of Naval Operations.

Event — May 14, 2024

The CSIS International Security Program hosted RADM Fred Pyle, Director, Surface Warfare Division, N96, Office of the Chief of Naval Operations, for a conversation on operations in the Red and Mediterranean Seas.

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Defence Research and Studies

Share Your Wisdom

Internship on ‘Research Writing’ and ‘Research Presentation’

The objective of this ‘Research Writing Program’ is to foster a spirit of scientific research among students and emerging scholars and mentor them to undertake qualitative research work in International Relations, Military Diplomacy, Maritime Security, Foreign Policy, Strategic and Military Affairs, Social Issues, Defence Technology, Defence Industry and Ethical Values. Certificate will be rendered to the candidate by DRaS and Praghna on successful completion of this program.

In this program, aspirants will be guided to undertake authentic research on topics of their choice and come out with findings in the form of an article associated with his/her research. Opportunities will be provided to them for presenting their paper in a webinar format post-submission of their research paper. Paper will be published on DRaS Web platform or EJSSS journal , on acceptance.

• Online program in ‘Research and Research Writing’
• Students undergoing Graduation, Post-Graduation and PhD can apply for a research internship
• Candidates can continue their program along with their campus program
• The program duration could vary from 30 days to 90 days depending on the depth of learning
• An opportunity to learn and publish research articles/ book reviews/opinions/ research findings
• Built your career as a writer, author and scholar
• Earn your certification from home
• Interns can always aspire to get into the Prime Minister’s scheme for Mentoring Young Authors
• Contact at [email protected] for more details
• Fees at a discount
• Attractive prices for the best articles created during the course
• Will provide a webinar platform to present their paper and findings

Learn from The Best Mentors

Gp Capt (Dr) R Srinivasan VSM(Rtd)

Cmde SL Deshmukh NM (Rtd)

Prof(Dr)(Cdr) Ashok Kumar Dua (Rtd)

Under Graduates

• Duration 30 days
• Book review and short article writing
• A one-day workshop on structure and content.
• Weekly review of progress
• Continuous support and guidance
• Review & Presentation in 3 rd  Week
• Publishing on DRaS Website or EJSSS journal , on acceptance
• Aspirants are to submit sample writing of 250 words & two preferred book titles
• Apply at email [email protected] to join the next batch
• Fees at a discount, Rs 1180 + GST for Indian Students
• Will provide a webinar platform to present the paper

Post Graduates/Mphil/PhD

• Duration 60 to 90 days.
• Research Article & Paper writing
• A two-day workshop on the selection of topic, structure and content.
• Review & Presentation of Article in 3 rd  Week
• Full Paper in the 11 th  Week
• Aspirants are to submit sample writing of 500 words & two preferred subjects and titles
• Fees at a discount, Rs 2950 + GST for Indian Students

Aspirants interested in applying can be associated as Research Assistants to “DRaS Praghna Internship Programs”. No remuneration will be given during the engagement period. DRaS and Praghna jointly conduct this program. Contact [email protected] or [email protected] for further information.

Defence Technology courses during Internship Period/ Semester Break

Defence Research and Studies (DRaS) offers  certified online crash courses  specific to “ Emerging Defence Technology ” round the year for engineers, engineering students and other aspirants. Qualified veterans with adequate professional experience are conducting the sessions. Courses can be imparted to dedicated batches of a specific academia/college during their internship period/ semester break. Click below link for more details. Click below for details.

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Today's research, tomorrow's breakthroughs.

Vannevar Bush stated in his seminal report, Science: the Endless Frontier that:

“Basic research leads to new knowledge. It provides scientific capital. It creates the fund from which the practical applications of knowledge must be drawn. New products and new processes do not appear full-grown. They are founded on new principles and new conceptions, which in turn are painstakingly developed by research in the purest realms of science.”

It is with these concepts in mind, that the Basic Research Office (BRO) approaches its role in oversight and management of DoD’s basic research investments. Additionally, BRO sets scientific priorities aimed toward ensuring DoD is a leader in scientific discovery and identifying new paths for investigation. The office is responsible for setting Department policy for grants, and manages programs including: the Vannevar Bush Faculty Fellowship , the  Minerva Research Initiative , Historically Black Colleges & Universities/Minority Institutions (HBCU/MI) Program ,  as well as a number of pilot programs meant to rethink the Department’s approach to managing and maturing basic research investments.

The Defense Established Program to Stimulate Competitive Research (DEPSCoR)  aims to increase the number of university researchers and improve the capabilities of institutions of higher education in eligible jurisdictions to perform competitive basic research in science & engineering relevant to the DoD mission and reflect national security priorities.

• STIX The Science, Technology, Innovation Exchange (STI X )   was originally piloted in 2017, with the intent of communicating the big ideas, positive social impacts, and disruptive capabilities that have resulted from DoD S&T investments.  The event included a series of lightning (up to 12 minute) talks in fields of science, technology, and STEM, that were presented by DoD personnel and DoD sponsored participants, from across the Department and that span careers from graduate students to senior researchers.

I-Corps @ DoD is a partnership with the National Science Foundation to provide DoD-funded researchers with training from experienced entrepreneurs in how to commercialize their innovations. BRO is also looking to establish bridges that will allow teams who have completed the training to more seamlessly mature innovations into products that may enter DoD programs of record. 

• The Laboratory University Collaboration Initiative (LUCI) The Laboratory University Collaboration Initiative (LUCI)   started in 2016 to identify, and competitively fund, three-year basic research collaborations between leading scientists at the DoD laboratories and the Vannevar Bush fellows at US universities in fields of critical interest to the Department.

The Bilateral Academic Research Initiative (BARI)  focuses on high-risk basic research in science and engineering as a bilateral academic collaboration, and supports  academic teams to combine unique skillsets and approaches and provide rapid advances in scientific areas of mutual potential interest to both countries.

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17 Thesis Defense Questions and How to Answer Them

A thesis defense gives you the chance to show off your thesis work and demonstrate your expertise in your field of study. During this one- to two-hour discussion with the members of your thesis committee, you'll have some control over how you present your research, but your committee will ask you some prodding questions to test your knowledge and preparedness. They will all have read your thesis beforehand, so their questions will relate to your study, topic, methods, data sample, and other aspects.

A good defense requires mastery of the thesis itself, so before you consider the questions you might face,

1. What is your topic, and why did you choose it?

Give a quick summary in just a few sentences on what you've researched. You could certainly go on for hours about your work, but make sure you prepare a way to give a very brief overview of your thesis. Then, give a quick background on your process for choosing this topic.

2. How does your topic contribute to the existing literature? How is it important?

Many researchers identify a need in the field and choose a topic to bridge the gaps that previous literature has failed to cover. For example, previous studies might not have included a certain population, region, or circumstance. Talk about how your thesis enhances the general understanding of the topic to extend the reach beyond what others have found, and then give examples of why the world needs that increased understanding. For instance, a thesis on romaine lettuce crops in desert climates might bring much-needed knowledge to a region that might not have been represented in previous work.

3. What are the key findings of your study?

When reporting your main results, make sure you have a handle on how detailed your committee wants you to be. Give yourself several options by preparing 1) a very general, quick summary of your findings that takes a minute or less, 2) a more detailed rundown of what your study revealed that is 3-5 minutes long, and 3) a 10- to 15-minute synopsis that delves into your results in detail. With each of these responses prepared, you can gauge which one is most appropriate in the moment, based on what your committee asks you and what has already been requested.

4. What type of background research did you do for your study?

Here you'll describe what you did while you were deciding what to study. This usually includes a literary review to determine what previous researchers have already introduced to the field. You also likely had to look into whether your study was going to be possible and what you would need in order to collect the needed data. Did you need info from databases that require permissions or fees?

5. What was your hypothesis, and how did you form it?

Describe the expected results you had for your study and whether your hypothesis came from previous research experience, long-held expectations, or cultural myths.

6. What limitations did you face when writing your text?

It's inevitable — researchers will face roadblocks or limiting factors during their work. This could be a limited population you had access to, like if you had a great method of surveying university students, but you didn't have a way to reach out to other people who weren't attending that school.

7. Why did you choose your particular method for your study?

Different research methods are more fitting to specific studies than others (e.g., qualitative vs. quantitative ), and knowing this, you applied a method that would present your findings most effectively. What factors led you to choose your method?

8. Who formed the sample group of your study, and why did you choose this population?

Many factors go into the selection of a participant group. Perhaps you were motivated to survey women over 50 who experience burnout in the workplace. Did you take extra measures to target this population? Or perhaps you found a sample group that responded more readily to your request for participation, and after hitting dead ends for months, convenience is what shaped your study population. Make sure to present your reasoning in an honest but favorable way.

9. What obstacles or limitations did you encounter while working with your sample?

Outline the process of pursuing respondents for your study and the difficulties you faced in collecting enough quality data for your thesis. Perhaps the decisions you made took shape based on the participants you ended up interviewing.

10. Was there something specific you were expecting to find during your analysis?

Expectations are natural when you set out to explore a topic, especially one you've been dancing around throughout your academic career. This question can refer to your hypotheses , but it can also touch on your personal feelings and expectations about this topic. What did you believe you would find when you dove deeper into the subject? Was that what you actually found, or were you surprised by your results?

11. What did you learn from your study?

Your response to this question can include not only the basic findings of your work (if you haven't covered this already) but also some personal surprises you might have found that veered away from your expectations. Sometimes these details are not included in the thesis, so these details can add some spice to your defense.

12. What are the recommendations from your study?

With connection to the reasons you chose the topic, your results can address the problems your work is solving. Give specifics on how policymakers, professionals in the field, etc., can improve their service with the knowledge your thesis provides.

13. If given the chance, what would you do differently?

Your response to this one can include the limitations you encountered or dead ends you hit that wasted time and funding. Try not to dwell too long on the annoyances of your study, and consider an area of curiosity; for example, discuss an area that piqued your interest during your exploration that would have been exciting to pursue but didn't directly benefit your outlined study.

14. How did you relate your study to the existing theories in the literature?

Your paper likely ties your ideas into those of other researchers, so this could be an easy one to answer. Point out how similar your work is to some and how it contrasts other works of research; both contribute greatly to the overall body of research.

15. What is the future scope of this study?

This one is pretty easy, since most theses include recommendations for future research within the text. That means you already have this one covered, and since you read over your thesis before your defense, it's already fresh in your mind.

16. What do you plan to do professionally after you complete your study?

This is a question directed more to you and your future professional plans. This might align with the research you performed, and if so, you can direct your question back to your research, maybe mentioning the personal motivations you have for pursuing study of that subject.

17. Do you have any questions?

Although your thesis defense feels like an interrogation, and you're the one in the spotlight, it provides an ideal opportunity to gather input from your committee, if you want it. Possible questions you could ask are: What were your impressions when reading my thesis? Do you believe I missed any important steps or details when conducting my work? Where do you see this work going in the future?

Bonus tip: What if you get asked a question to which you don't know the answer? You can spend weeks preparing to defend your thesis, but you might still be caught off guard when you don't know exactly what's coming. You can be ready for this situation by preparing a general strategy. It's okay to admit that your thesis doesn't offer the answers to everything – your committee won't reasonably expect it to do so. What you can do to sound (and feel!) confident and knowledgeable is to refer to a work of literature you have encountered in your research and draw on that work to give an answer. For example, you could respond, "My thesis doesn't directly address your question, but my study of Dr. Leifsen's work provided some interesting insights on that subject…." By preparing a way to address curveball questions, you can maintain your cool and create the impression that you truly are an expert in your field.

After you're done answering the questions your committee presents to you, they will either approve your thesis or suggest changes you should make to your paper. Regardless of the outcome, your confidence in addressing the questions presented to you will communicate to your thesis committee members that you know your stuff. Preparation can ease a lot of anxiety surrounding this event, so use these possible questions to make sure you can present your thesis feeling relaxed, prepared, and confident.

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Call for Papers | "Dissent in World History" | World History Bulletin | Fall/Winter 2024

World History Bulletin is seeking quality research essays, experiential learning case studies, and classroom activities for inclusion in its upcoming Fall/Winter 2024 issue, “ Dissent in World History .” Guest-edited by Barbara J. Falk, Professor in the Department of Defence Studies at the Royal Military College of Canada and Director of Academics at the Canadian Forces College, the issue will explore the question of national and transnational dissent in its broadest sense and across all historical time periods. Falk has written, published and taught about resistance, dissent and dissidence for more than 30 years.

Recent protests on college campuses across the United States over the Israel-Hamas conflict call to mind various examples of dissent throughout modern world history, from independence movements in Africa and the response to suppressive regimes in parts of South America, to revolutions in Cuba and China, dissent against communist and authoritarian governments in Central and Eastern Europe, and civil rights movements in apartheid South Africa and the Southern United States. Yet the genealogy of dissent is deeply embedded as a motive force in world history—from Plato’s critiques of Athenian democracy and the work of the Seven Sages of the Bamboo Grove to the fight against racist carceral systems in the West and the Arab Spring—and is ingrained in and inscribed on the human experience. 

The origins of and responses to theories and practices of dissent raise myriad questions about its nature, the forms dissent can and has taken, who determines/decides what is/is not appropriate in terms of defining or expressing dissent, the motives of actors involved, and the responsibilities of officials to enable or foreclose opportunities for dissent and under what legal or ethical lines of reasoning.

The Bulletin is interested in submissions covering a range of topics related to the theme of dissent in world history, including:

• Origins of Dissent Movements. The social, cultural, political, and/or economic factors which have motivated movements in the past. 
• Dissent Case Studies. The exploration of instances of dissent and their ramifications for local or global history and practice. 
• Globalized Dissent. Examining global responses to regional/local conflicts/conditions.
• Freedom, Dissent, and Suppression. Studying the tensions between a society with institutionalized freedom of expression and state actors/officials who intervene to suppress dissent.
• Authoritarian Learning and Dissent. How contemporary authoritarian states are repurposing techniques of suppression and adopting and adapting new forms of surveillance and control to persecute, prosecute and eliminate dissent.
• Future Dissent. How innovation disrupted the landscape of dissent in the past, and how this might serve as a guide to future dissent movements. 
• Techniques used in the classroom to introduce and explore dissent as part of wider political and sociocultural phenomena. 
• Historiographies of theories and practice concerned with dissent in World History.

World History Bulletin therefore invites contributions to a thematic issue on dissent in world history. We are especially interested in articles that share novel research or historiographical perspectives which explore the origins of dissent movements as part of wider sociocultural and political circumstances and examine discursive elements between dissent and reform (political, social, cultural, and economic); present innovative teaching at all levels that employs techniques related to dissent, revolution, and counterrevolution in world history; or explore the connection between student engagement and world history as a result of coursework related to the theme “dissent in world history.” We also welcome short interviews with designers, artists, writers, and scholars and small roundtables on a book, film, or other work.

Submission Guidelines: Research and pedagogical articles should range between 1,500 and 6,000 words in length, including endnote text. The Bulletin accepts submissions which adhere to the style, format, and documentation requirements as outlined in the most recent edition of the Chicago Manual of Style . The Bulletin uses endnote citations, rather than footnote citations. Text of submissions should be spelled according to American English standard usage (e.g., favorite, rather than favourite). Submissions should be written in past tense, rather than the literary present, and passive voice should be avoided. 

Submission Deadline: November 1, 2024

Essays and questions should be directed to Joseph M. Snyder, Editor-in-Chief of World History Bulletin , at [email protected] .

Joseph M. Snyder

Editor-in-Chief

Human Subjects Office

Medical terms in lay language.

Please use these descriptions in place of medical jargon in consent documents, recruitment materials and other study documents. Note: These terms are not the only acceptable plain language alternatives for these vocabulary words.

This glossary of terms is derived from a list copyrighted by the University of Kentucky, Office of Research Integrity (1990).

For clinical research-specific definitions, see also the Clinical Research Glossary developed by the Multi-Regional Clinical Trials (MRCT) Center of Brigham and Women’s Hospital and Harvard  and the Clinical Data Interchange Standards Consortium (CDISC) .

Alternative Lay Language for Medical Terms for use in Informed Consent Documents

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ABDOMEN/ABDOMINAL body cavity below diaphragm that contains stomach, intestines, liver and other organs ABSORB take up fluids, take in ACIDOSIS condition when blood contains more acid than normal ACUITY clearness, keenness, esp. of vision and airways ACUTE new, recent, sudden, urgent ADENOPATHY swollen lymph nodes (glands) ADJUVANT helpful, assisting, aiding, supportive ADJUVANT TREATMENT added treatment (usually to a standard treatment) ANTIBIOTIC drug that kills bacteria and other germs ANTIMICROBIAL drug that kills bacteria and other germs ANTIRETROVIRAL drug that works against the growth of certain viruses ADVERSE EFFECT side effect, bad reaction, unwanted response ALLERGIC REACTION rash, hives, swelling, trouble breathing AMBULATE/AMBULATION/AMBULATORY walk, able to walk ANAPHYLAXIS serious, potentially life-threatening allergic reaction ANEMIA decreased red blood cells; low red cell blood count ANESTHETIC a drug or agent used to decrease the feeling of pain, or eliminate the feeling of pain by putting you to sleep ANGINA pain resulting from not enough blood flowing to the heart ANGINA PECTORIS pain resulting from not enough blood flowing to the heart ANOREXIA disorder in which person will not eat; lack of appetite ANTECUBITAL related to the inner side of the forearm ANTIBODY protein made in the body in response to foreign substance ANTICONVULSANT drug used to prevent seizures ANTILIPEMIC a drug that lowers fat levels in the blood ANTITUSSIVE a drug used to relieve coughing ARRHYTHMIA abnormal heartbeat; any change from the normal heartbeat ASPIRATION fluid entering the lungs, such as after vomiting ASSAY lab test ASSESS to learn about, measure, evaluate, look at ASTHMA lung disease associated with tightening of air passages, making breathing difficult ASYMPTOMATIC without symptoms AXILLA armpit

BENIGN not malignant, without serious consequences BID twice a day BINDING/BOUND carried by, to make stick together, transported BIOAVAILABILITY the extent to which a drug or other substance becomes available to the body BLOOD PROFILE series of blood tests BOLUS a large amount given all at once BONE MASS the amount of calcium and other minerals in a given amount of bone BRADYARRHYTHMIAS slow, irregular heartbeats BRADYCARDIA slow heartbeat BRONCHOSPASM breathing distress caused by narrowing of the airways

CARCINOGENIC cancer-causing CARCINOMA type of cancer CARDIAC related to the heart CARDIOVERSION return to normal heartbeat by electric shock CATHETER a tube for withdrawing or giving fluids CATHETER a tube placed near the spinal cord and used for anesthesia (indwelling epidural) during surgery CENTRAL NERVOUS SYSTEM (CNS) brain and spinal cord CEREBRAL TRAUMA damage to the brain CESSATION stopping CHD coronary heart disease CHEMOTHERAPY treatment of disease, usually cancer, by chemical agents CHRONIC continuing for a long time, ongoing CLINICAL pertaining to medical care CLINICAL TRIAL an experiment involving human subjects COMA unconscious state COMPLETE RESPONSE total disappearance of disease CONGENITAL present before birth CONJUNCTIVITIS redness and irritation of the thin membrane that covers the eye CONSOLIDATION PHASE treatment phase intended to make a remission permanent (follows induction phase) CONTROLLED TRIAL research study in which the experimental treatment or procedure is compared to a standard (control) treatment or procedure COOPERATIVE GROUP association of multiple institutions to perform clinical trials CORONARY related to the blood vessels that supply the heart, or to the heart itself CT SCAN (CAT) computerized series of x-rays (computerized tomography) CULTURE test for infection, or for organisms that could cause infection CUMULATIVE added together from the beginning CUTANEOUS relating to the skin CVA stroke (cerebrovascular accident)

DERMATOLOGIC pertaining to the skin DIASTOLIC lower number in a blood pressure reading DISTAL toward the end, away from the center of the body DIURETIC "water pill" or drug that causes increase in urination DOPPLER device using sound waves to diagnose or test DOUBLE BLIND study in which neither investigators nor subjects know what drug or treatment the subject is receiving DYSFUNCTION state of improper function DYSPLASIA abnormal cells

ECHOCARDIOGRAM sound wave test of the heart EDEMA excess fluid collecting in tissue EEG electric brain wave tracing (electroencephalogram) EFFICACY effectiveness ELECTROCARDIOGRAM electrical tracing of the heartbeat (ECG or EKG) ELECTROLYTE IMBALANCE an imbalance of minerals in the blood EMESIS vomiting EMPIRIC based on experience ENDOSCOPIC EXAMINATION viewing an  internal part of the body with a lighted tube  ENTERAL by way of the intestines EPIDURAL outside the spinal cord ERADICATE get rid of (such as disease) Page 2 of 7 EVALUATED, ASSESSED examined for a medical condition EXPEDITED REVIEW rapid review of a protocol by the IRB Chair without full committee approval, permitted with certain low-risk research studies EXTERNAL outside the body EXTRAVASATE to leak outside of a planned area, such as out of a blood vessel

FDA U.S. Food and Drug Administration, the branch of federal government that approves new drugs FIBROUS having many fibers, such as scar tissue FIBRILLATION irregular beat of the heart or other muscle

GENERAL ANESTHESIA pain prevention by giving drugs to cause loss of consciousness, as during surgery GESTATIONAL pertaining to pregnancy

HEMATOCRIT amount of red blood cells in the blood HEMATOMA a bruise, a black and blue mark HEMODYNAMIC MEASURING blood flow HEMOLYSIS breakdown in red blood cells HEPARIN LOCK needle placed in the arm with blood thinner to keep the blood from clotting HEPATOMA cancer or tumor of the liver HERITABLE DISEASE can be transmitted to one’s offspring, resulting in damage to future children HISTOPATHOLOGIC pertaining to the disease status of body tissues or cells HOLTER MONITOR a portable machine for recording heart beats HYPERCALCEMIA high blood calcium level HYPERKALEMIA high blood potassium level HYPERNATREMIA high blood sodium level HYPERTENSION high blood pressure HYPOCALCEMIA low blood calcium level HYPOKALEMIA low blood potassium level HYPONATREMIA low blood sodium level HYPOTENSION low blood pressure HYPOXEMIA a decrease of oxygen in the blood HYPOXIA a decrease of oxygen reaching body tissues HYSTERECTOMY surgical removal of the uterus, ovaries (female sex glands), or both uterus and ovaries

IATROGENIC caused by a physician or by treatment IDE investigational device exemption, the license to test an unapproved new medical device IDIOPATHIC of unknown cause IMMUNITY defense against, protection from IMMUNOGLOBIN a protein that makes antibodies IMMUNOSUPPRESSIVE drug which works against the body's immune (protective) response, often used in transplantation and diseases caused by immune system malfunction IMMUNOTHERAPY giving of drugs to help the body's immune (protective) system; usually used to destroy cancer cells IMPAIRED FUNCTION abnormal function IMPLANTED placed in the body IND investigational new drug, the license to test an unapproved new drug INDUCTION PHASE beginning phase or stage of a treatment INDURATION hardening INDWELLING remaining in a given location, such as a catheter INFARCT death of tissue due to lack of blood supply INFECTIOUS DISEASE transmitted from one person to the next INFLAMMATION swelling that is generally painful, red, and warm INFUSION slow injection of a substance into the body, usually into the blood by means of a catheter INGESTION eating; taking by mouth INTERFERON drug which acts against viruses; antiviral agent INTERMITTENT occurring (regularly or irregularly) between two time points; repeatedly stopping, then starting again INTERNAL within the body INTERIOR inside of the body INTRAMUSCULAR into the muscle; within the muscle INTRAPERITONEAL into the abdominal cavity INTRATHECAL into the spinal fluid INTRAVENOUS (IV) through the vein INTRAVESICAL in the bladder INTUBATE the placement of a tube into the airway INVASIVE PROCEDURE puncturing, opening, or cutting the skin INVESTIGATIONAL NEW DRUG (IND) a new drug that has not been approved by the FDA INVESTIGATIONAL METHOD a treatment method which has not been proven to be beneficial or has not been accepted as standard care ISCHEMIA decreased oxygen in a tissue (usually because of decreased blood flow)

LAPAROTOMY surgical procedure in which an incision is made in the abdominal wall to enable a doctor to look at the organs inside LESION wound or injury; a diseased patch of skin LETHARGY sleepiness, tiredness LEUKOPENIA low white blood cell count LIPID fat LIPID CONTENT fat content in the blood LIPID PROFILE (PANEL) fat and cholesterol levels in the blood LOCAL ANESTHESIA creation of insensitivity to pain in a small, local area of the body, usually by injection of numbing drugs LOCALIZED restricted to one area, limited to one area LUMEN the cavity of an organ or tube (e.g., blood vessel) LYMPHANGIOGRAPHY an x-ray of the lymph nodes or tissues after injecting dye into lymph vessels (e.g., in feet) LYMPHOCYTE a type of white blood cell important in immunity (protection) against infection LYMPHOMA a cancer of the lymph nodes (or tissues)

MALAISE a vague feeling of bodily discomfort, feeling badly MALFUNCTION condition in which something is not functioning properly MALIGNANCY cancer or other progressively enlarging and spreading tumor, usually fatal if not successfully treated MEDULLABLASTOMA a type of brain tumor MEGALOBLASTOSIS change in red blood cells METABOLIZE process of breaking down substances in the cells to obtain energy METASTASIS spread of cancer cells from one part of the body to another METRONIDAZOLE drug used to treat infections caused by parasites (invading organisms that take up living in the body) or other causes of anaerobic infection (not requiring oxygen to survive) MI myocardial infarction, heart attack MINIMAL slight MINIMIZE reduce as much as possible Page 4 of 7 MONITOR check on; keep track of; watch carefully MOBILITY ease of movement MORBIDITY undesired result or complication MORTALITY death MOTILITY the ability to move MRI magnetic resonance imaging, diagnostic pictures of the inside of the body, created using magnetic rather than x-ray energy MUCOSA, MUCOUS MEMBRANE moist lining of digestive, respiratory, reproductive, and urinary tracts MYALGIA muscle aches MYOCARDIAL pertaining to the heart muscle MYOCARDIAL INFARCTION heart attack

NASOGASTRIC TUBE placed in the nose, reaching to the stomach NCI the National Cancer Institute NECROSIS death of tissue NEOPLASIA/NEOPLASM tumor, may be benign or malignant NEUROBLASTOMA a cancer of nerve tissue NEUROLOGICAL pertaining to the nervous system NEUTROPENIA decrease in the main part of the white blood cells NIH the National Institutes of Health NONINVASIVE not breaking, cutting, or entering the skin NOSOCOMIAL acquired in the hospital

OCCLUSION closing; blockage; obstruction ONCOLOGY the study of tumors or cancer OPHTHALMIC pertaining to the eye OPTIMAL best, most favorable or desirable ORAL ADMINISTRATION by mouth ORTHOPEDIC pertaining to the bones OSTEOPETROSIS rare bone disorder characterized by dense bone OSTEOPOROSIS softening of the bones OVARIES female sex glands

PARENTERAL given by injection PATENCY condition of being open PATHOGENESIS development of a disease or unhealthy condition PERCUTANEOUS through the skin PERIPHERAL not central PER OS (PO) by mouth PHARMACOKINETICS the study of the way the body absorbs, distributes, and gets rid of a drug PHASE I first phase of study of a new drug in humans to determine action, safety, and proper dosing PHASE II second phase of study of a new drug in humans, intended to gather information about safety and effectiveness of the drug for certain uses PHASE III large-scale studies to confirm and expand information on safety and effectiveness of new drug for certain uses, and to study common side effects PHASE IV studies done after the drug is approved by the FDA, especially to compare it to standard care or to try it for new uses PHLEBITIS irritation or inflammation of the vein PLACEBO an inactive substance; a pill/liquid that contains no medicine PLACEBO EFFECT improvement seen with giving subjects a placebo, though it contains no active drug/treatment PLATELETS small particles in the blood that help with clotting POTENTIAL possible POTENTIATE increase or multiply the effect of a drug or toxin (poison) by giving another drug or toxin at the same time (sometimes an unintentional result) POTENTIATOR an agent that helps another agent work better PRENATAL before birth PROPHYLAXIS a drug given to prevent disease or infection PER OS (PO) by mouth PRN as needed PROGNOSIS outlook, probable outcomes PRONE lying on the stomach PROSPECTIVE STUDY following patients forward in time PROSTHESIS artificial part, most often limbs, such as arms or legs PROTOCOL plan of study PROXIMAL closer to the center of the body, away from the end PULMONARY pertaining to the lungs

QD every day; daily QID four times a day

RADIATION THERAPY x-ray or cobalt treatment RANDOM by chance (like the flip of a coin) RANDOMIZATION chance selection RBC red blood cell RECOMBINANT formation of new combinations of genes RECONSTITUTION putting back together the original parts or elements RECUR happen again REFRACTORY not responding to treatment REGENERATION re-growth of a structure or of lost tissue REGIMEN pattern of giving treatment RELAPSE the return of a disease REMISSION disappearance of evidence of cancer or other disease RENAL pertaining to the kidneys REPLICABLE possible to duplicate RESECT remove or cut out surgically RETROSPECTIVE STUDY looking back over past experience

SARCOMA a type of cancer SEDATIVE a drug to calm or make less anxious SEMINOMA a type of testicular cancer (found in the male sex glands) SEQUENTIALLY in a row, in order SOMNOLENCE sleepiness SPIROMETER an instrument to measure the amount of air taken into and exhaled from the lungs STAGING an evaluation of the extent of the disease STANDARD OF CARE a treatment plan that the majority of the medical community would accept as appropriate STENOSIS narrowing of a duct, tube, or one of the blood vessels in the heart STOMATITIS mouth sores, inflammation of the mouth STRATIFY arrange in groups for analysis of results (e.g., stratify by age, sex, etc.) STUPOR stunned state in which it is difficult to get a response or the attention of the subject SUBCLAVIAN under the collarbone SUBCUTANEOUS under the skin SUPINE lying on the back SUPPORTIVE CARE general medical care aimed at symptoms, not intended to improve or cure underlying disease SYMPTOMATIC having symptoms SYNDROME a condition characterized by a set of symptoms SYSTOLIC top number in blood pressure; pressure during active contraction of the heart

TERATOGENIC capable of causing malformations in a fetus (developing baby still inside the mother’s body) TESTES/TESTICLES male sex glands THROMBOSIS clotting THROMBUS blood clot TID three times a day TITRATION a method for deciding on the strength of a drug or solution; gradually increasing the dose T-LYMPHOCYTES type of white blood cells TOPICAL on the surface TOPICAL ANESTHETIC applied to a certain area of the skin and reducing pain only in the area to which applied TOXICITY side effects or undesirable effects of a drug or treatment TRANSDERMAL through the skin TRANSIENTLY temporarily TRAUMA injury; wound TREADMILL walking machine used to test heart function

UPTAKE absorbing and taking in of a substance by living tissue

VALVULOPLASTY plastic repair of a valve, especially a heart valve VARICES enlarged veins VASOSPASM narrowing of the blood vessels VECTOR a carrier that can transmit disease-causing microorganisms (germs and viruses) VENIPUNCTURE needle stick, blood draw, entering the skin with a needle VERTICAL TRANSMISSION spread of disease

WBC white blood cell

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• Published: 03 July 2024

Effect of silicon spraying on rice photosynthesis and antioxidant defense system on cadmium accumulation

• Hongxing Chen 1 , 2 ,
• Xiaoyun Huang 1 , 2 ,
• Hui Chen 1 , 2 ,
• Song Zhang 1 , 2 ,
• Chengwu Fan 3 ,
• Tianling Fu 2 , 4 ,
• Tengbing He 1 , 2 &
• Zhenran Gao 1 , 2  

Scientific Reports volume  14 , Article number:  15265 ( 2024 ) Cite this article

Metrics details

• Environmental sciences
• Plant sciences

Cadmium (Cd) pollution is a serious threat to food safety and human health. Minimizing Cd uptake and enhancing Cd tolerance in plants are vital to improve crop yield and reduce hazardous effects to humans. In this study, we designed three Cd concentration stress treatments (Cd1: 0.20 mg·kg −1 , Cd2: 0.60 mg·kg −1 , and Cd3: 1.60 mg·kg −1 ) and two foliar silicon (Si) treatments (CK: no spraying of any material, and Si: foliar Si spraying) to conduct pot experiments on soil Cd stress. The results showed that spraying Si on the leaves reduced the Cd content in brown rice by 4.79–42.14%. Si application increased net photosynthetic rate (Pn) by 1.77–4.08%, stomatal conductance (Gs) by 5.27–23.43%, transpiration rate (Tr) by 2.99–20.50% and intercellular carbon dioxide (CO 2 ) concentration (Ci) by 6.55–8.84%. Foliar spraying of Si significantly increased the activities of superoxide dismutase (SOD) and peroxidase (POD) in rice leaves by 9.84–14.09% and 4.69–53.09%, respectively, and reduced the content of malondialdehyde (MDA) by 7.83–48.72%. In summary, foliar Si spraying protects the photosynthesis and antioxidant system of rice canopy leaves, and is an effective method to reduce the Cd content in brown rice.

Introduction

Cadmium (Cd) is a major pollutant affecting the quality of farmland soil, and its biological toxicity is significant 1 . Because of its high solubility and fluidity, the toxic effects of Cd on plants are manifested in various metabolic activities. A large amount of Cd accumulates in plants, leading to a reduction in plant photosynthetic rate, inhibition of plant antioxidant enzyme activity, and suppression of cell division, thereby impacting plant growth 2 , 3 , 4 . Moreover, it enters the human body through the food chain and causes harm 5 . Rice ( Oryza sativa L.) is the main food crop in China and also the main source of food for over 50% of the global population. However, because of soil pollution, the accumulation of Cd in rice has led to “Cd rice” 6 , and long-term consumption of food contaminated by Cd often induces cancer, pain, kidney toxicity and hypertension 7 . Therefore, the monitoring and control of Cd pollution need to be strengthened to ensure human health and food security.

Many measures have been taken to reduce the accumulation of Cd in rice, including soil remediation works, agricultural practices, and phytoremediation 8 . These remediation techniques are complex and often expensive on a site scale 9 . As the most important foreign nutrient organ of rice, leaves can absorb foreign substances and transport nutrients to other organs of rice 10 . Compared with other agronomic control measures, foliar spraying barrier agent has the characteristics of consistent farming time, convenient application, economical and efficient, and has been widely used in farmland production. It has a good effect on improving crop stress resistance, enhancing crop heavy metal tolerance and increasing crop yield 11 .

Silicon (Si) is not only a beneficial element 12 , the application of Si can promote the absorption of nutrients by plants, significantly enhance their biological and abiotic resistance, which is conducive to plant growth, but also reduce the toxic effect of Cd on plants 13 . Research has found that under Cd stress, Si application increased chlorophyll content (SPAD), carotenoid content and photosynthetic rate of maize leaves 14 . The application of exogenous Si reduced the malondialdehyde (MDA) content of cotton, increased the activity of antioxidant enzymes, alleviated the adverse effects of Cd stress on the growth and photosynthetic characteristics of cotton, and improved the quality of cotton 2 . Foliar Si application significantly increased rice yield, reduced the bioavailability of Cd in soil, inhibited the migration and transformation of Cd in soil and plants, slow down the content of Cd in rice, and improved the quality of rice 15 .

The above researches mainly focus on acid soil or hydroponic experiments, but there are few researches on neutral paddy soil in southern China. Therefore, a pot experiment was conducted to study the effects of foliar Si spraying on growth, photosynthetic characteristics and antioxidant system of Cd-stressed rice in southern rice soil. We proposed the following hypothesis: that foliar Si spraying treatment suppresses the migration and transportation of Cd by rice plants, thereby reducing the Cd content in brown rice, increasing rice yield, improving rice light utilization efficiency, and enhancing antioxidant effects, ultimately enhancing the alleviating effect on Cd toxicity. Therefore, this study aimed to: (1) explore the effect and mechanism of foliar Si application on the migration and accumulation of Cd in rice plants; (2) explore the potential and mechanism of foliar Si application on improving rice photosynthesis and stress resistance; and (3) explore the effect and mechanism of foliar Si application on enhancing the antioxidant capacity of rice. The results will provide a valuable reference for reducing the accumulation of Cd in rice, improving its safety as food, and ensuring human health.

Materials and methods

Experimental design.

The experiment was conducted at the Guiyang Comprehensive Experimental Station of the Guizhou Academy of Agricultural Sciences in China from March to October 2021 (106°39′20″E, 26°29′59″N). The pot experiment was conducted under natural sunlight and temperature (from March to October, 2022). The air temperature ranged between 10.5 ± 5.6 and 28.6 ± 2.5 °C. The relative humidity varied from 77 ± 2.8 to 93 ± 0.5%. The basic physical and chemical indicators of soils are shown in Table 1 .

The background value of soil Cd was 0.20 mg·kg −1 , and 0.20 mg·kg −1 was the risk screening value for Cd in the rice fields. The experiment set up three exogenous Cd concentration addition treatments: Cd1 (0), Cd2 (0.20 mg∙kg −1 ), and Cd3 (0.40 mg∙kg −1 ). The rice variety used was “Jingliangyou 534” (Guoshen Rice 20,176,004). Each box was uniformly inserted in four holes as a treatment, with two plants per hole, and each treatment was replicated six times for a total of 18 pots. Before transplanting the rice seedlings, base fertilizer was applied: 450 kg·hm −2 rice-specific compound fertilizer. Tillering fertilizer (urea 120 kg·hm −2 ) was sprayed onto the plants during the tillering stage, and potassium chloride fertilizer (112.5 kg·hm −2 ) was sprayed onto the plants during the booting stage. The soil type was yellow loamy paddy soil. Adding of exogenous Cd to the soil involved mixing Cd chloride (CdCl 2 ) (Shanghai Aladdin biochemical technology Co., Ltd., Shanghai, China) in solution with air-dried soil, injecting water to saturation, and equilibrating for 4–5 weeks. The actual values after addition were Cd1 (0.20 mg·kg −1 ), Cd2 (0.60 mg·kg −1 ), and Cd3 (1.60 mg·kg −1 ). When the rice was mature, the SPAD, Cd content, photosynthetic parameters, and enzyme activity of rice canopy leaves under different Cd concentrations were measured. Two foliar spraying treatments: CK (no spraying of any material) and Si (foliar spraying of Si) were used. In the spraying of “Jianggeling” rice with foliar Si fertilizer (Foshan Ironman Environmental Technology Co., Ltd., Foshan, China), the active ingredients were primarily high-purity SiO 2 sols (Si ≥ 85 g·L −1 , pH = 5.0–7.0) at a concentration of 2.5 g·L −1 . One spray was administered at the jointing stage and one at the heading stage, at 17:00–18:00 p.m.

Measurement of indicators

Determination of cd content.

An inductively coupled plasma optical emission spectrometer (ICP-OES, Thermo Fisher Scientific, Waltham, MA, USA) was used to measure the Cd content 16 . At the maturity stage of rice, we handpicked three robust and evenly developed specimens from every group. Subsequently, these specimens underwent multiple cleansings using faucet water, followed by a deionized water purge. Post-washing, the samples were subjected to a brief heat exposure at 105 °C for half an hour and subsequently desiccated in a heating chamber regulated at 75 °C to achieve a stable mass. Afterward, the samples were methodically segmented into the roots, stems, leaves, husks, and brown rice parts, and were finely pulverized with the assistance of a high-velocity FW-100 grinder (Tianjin Taist Instrument Co., Ltd.). Subsequently, a 200 mg portion of the rice specimen was measured out, and to this, we introduced 5 mL of nitric acid (HNO 3 ). The digestion process for the specimen was carried out with a graphite digestion device at a temperature of 120 °C for a duration of two hours, proceeding until no residual sediment remained within the digestion chamber. The temperature was adjusted to 150 °C to evaporate the acid. The sample was removed and allowed to cool, diluted to a volume of 50 mL in a volumetric flask, filtered, and analyzed via ICP–OES.

Measurement of photosynthetic parameters

Portable photosynthetic apparatus (GFS-3000, Heinz Walz GmbH, Bavaria, Germany) was used to measure the photosynthetic parameters of rice at the heading stage 17 . Between 10:00–11:00 a.m. on a clear, cloudless day, the carbon dioxide (CO 2 ) concentration was set to 400 µ mol·mol −1 , the light intensity was set to 1200 µ mol·m −2 ·s −1 , the air velocity was set to 0.5 L·min −1 , leaf temperature was 25 °C, and relative humidity was set to 70%. We handpicked three robust and evenly developed specimens from every group to measure the net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), and intercellular CO 2 concentration (Ci).

Measurement of fluorescence parameters

A portable fluorometer (Junior-PAM, Heinz Walz GmbH, Bavaria, Germany) was used to measure chlorophyll fluorescence parameters 18 . We selected rice leaves with consistent growth conditions, subjected to fully adapt to darkness for 30 min, and measured the maximum photochemical quantum yield of photosystem II (PS II) of the leaves, maximum photochemical efficiency (Fv/Fm), actual photochemical efficiency (Y(II)), initial fluorescence (Fo), and non-photochemical quenching coefficient (NPQ).

Measurement of MDA and antioxidant enzymes

We cleaned rice leaves with distilled water and weighed 100 mg of fresh rice leaves, ground them into a homogenate using liquid nitrogen in a mortar and pestle, and then transferred the homogenate to a 4 mL centrifuge tube. We added 1 mL of 0.05 mol·L −1 phosphate buffer (pH 7.8) to the tube and fixed the volume to 4 mL. This was mixed well using a vortexer, and was put into a frozen high-speed centrifuge at 4 °C and 10,000 r·min −1 for 10 min, The supernatant was then placed in a refrigerator at 4 °C as a backup. The activities of superoxide dismutase (SOD) and peroxidase (POD) in rice leaves and the MDA content were determined using the nitroblue tetrazolium (NBT) photoreduction method 19 , guaiacol method, and thiobarbituric acid (TBA) method, respectively. All measurements were performed using enzyme activity assay kits from Wuhan PureBiochemical Co., Ltd.

Determination of relative chlorophyll content

We used a portable chlorophyll meter (SPAD-502 Plus, Minolta, Tokyo, Japan) to measure the SPAD value of leaves in situ 20 . When they had been measured, we selected three rice plants with uniform growth conditions and, for each plant, selected an intact leaf and measured the SPAD value at the central position six times, and took the average value as the SPAD value for that point. When taking measurements, we avoided areas with concentrated veins and used appropriate shading to block direct sunlight, to ensure the accuracy of the measurement.

Data processing and analysis

The bioconcentration factor (BCF) of Cd in rice was calculated (1) as 21 :

The transport factor (TF) of Cd in rice was calculated (2) as 22 :

where TF refers to the ratio of heavy metal concentration in part A to that in part B of the rice plant.

Data processing and statistical analysis were carried out using SPSS 24.0 (IBM Corp., Armonk, NY, USA). Single factor analysis of variance (ANOVA) was used to tested the same treatment under different Cd concentrations. The treatment effects at different Cd concentrations were compared by using the least significant different test with the P value < 0.05. The effects with Si treatment and CK treatment were tested by t test. Plots were generated using Origin.

Effect of foliar spraying Si on Cd content in various organs and on rice yield

The impact of foliar spraying Si on the Cd content in various organs and on rice yield are shown in Table 2 .

Under the three Cd concentrations, the Cd content in each organ of rice increased with the increase in Cd concentration. At Cd1 concentration, compared with CK, Si treatment increased the Cd content in roots, leaves, and cobs by 112.99%, 30.00%, and 51.85%, respectively, and reduced the Cd content in husks and brown rice by 29.17% and 40.91%, respectively. At Cd2 concentration, compared with CK, Si treatment significantly increased the Cd content in the stems and cobs by 145.07% and 61.36%, respectively, and significantly decreased the Cd content in husks by 41.67%, respectively. At Cd3 concentration, compared with CK, Si treatment increased the Cd content in leaves and cobs by 26.47% and 62.80%, respectively, and decreased the Cd content in husks and brown rice by 33.90% and 12.57%, respectively. Rice yield decreased with increasing Cd concentration. At the three Cd concentrations, spraying Si on the leaves increased rice yield by 4.18%, 2.36%, and 6.14% compared to CK, respectively. It can be seen that Cd stress will increase the Cd content in various organs and reduce rice yield. In contrast, spraying Si on the leaves can change the accumulation of Cd in various organs, and increase rice yield.

Effect of foliar spraying Si on the accumulation and transport of Cd in rice

The effect of foliar spraying Si on the BCF in various organs are shown in Fig.  1 . The accumulation of Cd in rice showed a trend of root > stem > leaf > brown rice. Under CK treatment, the enrichment coefficients of roots, stems, leaves, and brown rice were 1.65–2.16, 0.18–1.00, 0.28–0.49, and 0.22–0.28, respectively. Compared with CK, under treatments Cd1, Cd2, and Cd3, foliar application of Si enhanced rice BCFroot by 112.91%, 0.41%, and 11.03%; BCFstem by 17.78%, 146.33%, and 1.60%; BCFleaf by 32.25%, 8.18%, and 26.41%; and decreased rice BCFbrown rice by 42.27%, 4.78%, and 12.59%, respectively. It can be seen that foliar application of Si can increase the enrichment coefficients of rice roots and leaves, which decreased the Cd enrichment coefficients of brown rice.

The effect of foliar Si spraying on the BCF of various organs in rice: BCFroot ( a ), BCFstem ( b ), BCFleaf ( c ), BCFbrown rice ( d ). Cd1, Cd2, Cd3: Three Cd concentration stress treatments (Cd1: 0.20 mg·kg −1 , Cd2: 0.60 mg·kg −1 , and Cd3: 1.60 mg·kg −1 ). CK, Si: two spraying treatments (CK: no spraying of any material, Si: foliar Si spraying). Data present the mean ± standard deviation of three replicates. Capital letters indicate significant differences ( p  < 0.05) between CK and Si treatments at the same Cd concentration. Lowercase letters indicate significant differences ( p  < 0.05) between CK or Si treatments at different Cd concentrations.

The effect of foliar spraying Si on the TF in various organs are shown in Fig.  2 . Foliar spraying of Si decreased TFleaf-brown rice, and TFstem-brown rice. Compared with CK, foliar spraying of Si decreased rice TFleaf-brown rice by 57.27%, 11.43%, and 30.90%, and of TFstem-brown rice by 51.44%, 61.15%, and 15.90%. It can be seen that foliar application of Si can decrease the transfer coefficient of rice leaf to brown rice and stem to brown rice, which decreased the Cd content of brown rice.

The effect of foliar Si spraying on the TF of various organs in rice: TFroot-stem ( a ), TFstem-leaf ( b ), TFleaf-brown rice ( c ), TFstem-brown rice ( d ). Cd1, Cd2, Cd3: Three Cd concentration stress treatments (Cd1: 0.20 mg·kg −1 , Cd2: 0.60 mg·kg −1 , and Cd3: 1.60 mg·kg −1 ). CK, Si: two spraying treatments (CK: no spraying of any material, Si: foliar Si spraying). Data present the mean ± standard deviation of three replicates. Capital letters indicate significant differences ( p  < 0.05) between CK and Si treatments at the same Cd concentration. Lowercase letters indicate significant differences ( p  < 0.05) between CK or Si treatments at different Cd concentrations.

Effect of foliar spraying Si on the SPAD values of rice leaves

The effect of foliar spraying Si on the SPAD values of rice leaves are shown in Fig.  3 . The SPAD values of leaves under three Cd concentration treatments all decreased with the increase in Cd concentration. Compared with the control Cd1 treatment, the decrease in Cd2 and Cd3 treatments was 4.31% and 7.22%, respectively. Under the treatment of spraying Si, the decrease in Cd2 and Cd3 treatments was 3.97% and 6.75%, respectively, compared with the treatment Cd1. Foliar spraying of Si resulted in an increase of 2.02–2.53% in SPAD values compared to the control group. Thus it can be seen that Cd reduces the SPAD values of rice leaves, whereas foliar spraying of Si enhances these values.

The effects of foliar Si spraying on the SPAD values of rice leaves. Cd1, Cd2, Cd3: Three Cd concentration stress treatments (Cd1: 0.20 mg·kg −1 , Cd2: 0.60 mg·kg −1 , and Cd3: 1.60 mg·kg −1 ). CK, Si: two spraying treatments (CK: no spraying of any material, Si: foliar Si spraying). Data present the mean ± standard deviation of six replicates. Capital letters indicate significant differences ( p  < 0.05) between CK and Si treatments at the same Cd concentration. Lowercase letters indicate significant differences ( p  < 0.05) between CK or Si treatments at different Cd concentrations.

Effect of foliar spraying Si on photosynthetic parameters of rice leaves

The impact of foliar spraying Si on the photosynthetic parameters of rice leaves are shown in Fig.  4 a–d. As Cd concentration increased, under CK and Si treatment, the Pn, Gs, Tr, and Ci values all decreased. Under CK treatment, compared with Cd1 concentration, the Pn, Gs, Tr, and Ci at Cd2 concentration decreased by 6.68%, 19.97%, 4.65%, and 6.13%, respectively. In contrast, at the concentration of Cd3, the decrease amplitude was 12.86%, 40.54%, 31.88%, and 15.25%, respectively. Compared to CK, foliar spraying Si resulted in a 1.77–4.08% increase in Pn, a 5.27–23.43% increase in Gs, a 2.99–20.50% increase in Tr, and a 6.55–8.84% increase in Ci, respectively. Therefore, Cd diminished the photosynthetic attributes of rice, whereas foliar spraying Si can mitigate the toxic impact of Cd on rice, enhance its the photosynthetic parameters, and foster photosynthesis.

The effects of foliar Si spraying on the photosynthetic parameters of rice leaves: net photosynthetic rate (Pn) ( a ), stomatal conductance (Gs) ( b ), transpiration rate (Tr) (c), intercellular CO 2 concentration (Ci) (d). Cd1, Cd2, Cd3: Three Cd concentration stress treatments (Cd1: 0.20 mg·kg −1 , Cd2: 0.60 mg·kg −1 , and Cd3: 1.60 mg·kg −1 ). CK, Si: two spraying treatments (CK: no spraying of any material, Si: foliar Si spraying). Data present the mean ± standard deviation of three replicates. Capital letters indicate significant differences ( p  < 0.05) between CK and Si treatments at the same Cd concentration. Lowercase letters indicate significant differences ( p  < 0.05) between CK or Si treatments at different Cd concentrations.

Effect of foliar spraying Si on the fluorescence parameters of rice leaves

The influence of foliar spraying Si on the fluorescence parameters of rice leaves are shown in Fig.  5 a–d. where Y(II) and Fv/Fm decreased with increasing Cd concentration, whereas Fo and NPQ increased with increasing Cd concentration. At the three concentrations of Cd1, Cd2, and Cd3, compared to CK, foliar Si spraying resulted in an increase in Y(II) and Fv/Fm by 0.38–5.98% and 1.55–2.78%, respectively, while simultaneously reducing Fo and NPQ by 3.11–9.67% and 7.48–16.47%, respectively. Under Cd stress, foliar application of Si can effectively maintain high photosynthetic characteristics.

The effects of foliar Si spraying on the chlorophyll fluorescence parameters of rice leaves: actual photochemical efficiency: Y (II) ( a ), non photochemical quenching coefficient: (NPQ) ( b ), initial fluorescence (Fo) ( c ), maximum photochemical efficiency (Fv/Fm) ( d ). Cd1, Cd2, Cd3: Three Cd concentration stress treatments (Cd1: 0.20 mg·kg −1 , Cd2: 0.60 mg·kg −1 , and Cd3: 1.60 mg·kg −1 ). CK, Si: two spraying treatments (CK: no spraying of any material, Si: foliar Si spraying). Data present the mean ± standard deviation of three replicates. Capital letters indicate significant differences ( p  < 0.05) between CK and Si treatments at the same Cd concentration. Lowercase letters indicate significant differences ( p  < 0.05) between CK or Si treatments at different Cd concentrations.

Effect of foliar spraying Si on MDA, POD, and SOD content in rice leaves

The impact of foliar spraying Si on the levels of MDA, POD, and SOD activity are shown in Fig.  6 a–c. Under CK treatment, as the concentration of Cd increased, the content of MDA rose, whereas the activities of POD and SOD decreased. Compared to CK, foliar spraying of Si significantly reduced the content of MDA in rice leaves by 7.83–48.72%. Additionally, compared to CK, foliar spraying of Si significantly increased the activities of SOD and POD in rice leaves by 9.84–14.09% and 4.69–53.09%, respectively. It can be seen that foliar Si application can improve the antioxidant enzyme activity of rice leaves.

The effects of foliar Si spraying on MDA, POD and SOD content in rice leaves: malondialdehyde: MDA ( a ), peroxidase: (POD) ( b ), superoxide dismutase (SOD) ( c ). Cd1, Cd2, Cd3: Three Cd concentration stress treatments (Cd1: 0.20 mg·kg −1 , Cd2: 0.60 mg·kg −1 , and Cd3: 1.60 mg·kg −1 ). CK, Si: two spraying treatments (CK: no spraying of any material, Si: foliar Si spraying). Data present the mean ± standard deviation of three replicates. Capital letters indicate significant differences ( p  < 0.05) between CK and Si treatments at the same Cd concentration. Lowercase letters indicate significant differences ( p  < 0.05) between CK or Si treatments at different Cd concentrations.

The excessive accumulation of Cd in plants not only significantly impacts their growth, development, quality, and yield, but also poses a potential threat to human health through the food chain because of its concealed presence within the plants 23 . The half-life of Cd in the human body is up to 30 years and it has a cumulative effect 24 . Excess Cd accumulation in the human body will cause calcification of kidney and bone, metabolic dysfunction, bone pain, hypertension, diabetes, emphysema, and other diseases. It can lead to deoxyribonucleic acid (DNA) oxidative damage and inhibition of the repair path, and induce the generation of cancer cells 25 . Research has shown that Si can effectively reduce the harm of Cd to plants and its inhibitory effect on plant growth, thereby improving the beneficial effects of food safety and human health 26 . In this study, foliar Si application had no significant effect on rice yield, but there was a trend of increasing yield under different soil Cd concentrations (Table 2 ). This is consistent with previous research findings 27 . The application of Si under metal stress can improve plant growth by increasing nutrient elements, SPAD, root volume, organic acid secretion, and histological characteristics 28 , 29 , 30 . Cd was highest in the roots of rice plants (Table 2 ), consistent with previous research findings 31 , 32 . The root system is the first plant organ to sense adversity. Excessive Cd can cause a decrease in the number of roots, a shortening or browning of roots, a decrease in root area, and can affect the division of root tip cells, inducing stress Chromosome aberrations and other factors can significantly reduce the absorption capacity of roots for water and nutrients in the soil 33 . Overall, the high retention of Cd in roots is considered a defense mechanism for plants to alleviate metal stress 27 . The Cd content in brown rice is a major health risk of significant concern 33 . The results showed that Si application could significantly reduce the Cd content in brown rice (Table 2 ) ( P  < 0.05). Under Cd stress in brown rice, Si application significantly reduced the transfer and enrichment coefficients of Cd, and reduced the Cd content 34 . The application of Si on the leaves mainly reduces the accumulation of Cd in brown rice by inhibiting the migration of Cd from the stem to the rice grains (Fig.  1 ). The stem is the main organ that restricts the transport of Cd to rice 35 . The stem nodes of Poaceae plants are the hub for the distribution of mineral elements to different organs, and the upward transport of Cd is significantly restricted at these nodes 36 . The high Cd content in the cell wall of stems and leaves is due to the presence of a large number of negatively charged functional groups in the cell wall 37 . These functional groups are precipitated and complexed with positively charged heavy metal ions, allowing most of the Cd to bind to the cell wall. Rice can alleviate the toxic effects of Cd by combining Cd and Si in the cell wall to alter the redox potential 38 . Combining with Si in the form of negatively charged hemicellulose can inhibit the absorption of Cd by rice cells. Therefore, foliar spraying of Si fertilizer is a feasible method to control Cd accumulation in rice grains, thereby reducing its risk to human health through the food chain.

In higher plants, Cd affects photosynthesis mainly by reducing the SPAD values, causing a decrease in the content of photosynthetic pigments, disrupting the position of matrix layers and grana within chloroplasts, leading to a decrease in the photosynthetic capacity of chloroplasts 39 . Cd can also inhibit the enzymes related to photosynthesis and affect plant growth by altering transpiration, respiration, and stomatal switch, thereby inhibiting crop photosynthesis 40 . This study found that, under Cd stress, the SPAD in rice leaves decreased (Fig.  3 ), this is consistent with the previous studies 39 . On the one hand, this is because Cd accumulates in rice leaves, altering the ultrastructure of chloroplasts, severely damaging the thylakoid membrane and chloroplasts, and leading to a decrease in SPAD 41 . On the other hand, because the peroxidation reaction produces a large amount of hydrogen peroxide (H 2 O 2 ), this enters the chloroplast through the plasma membrane, attacks the chloroplast pigment protein complex, and inhibits the activity of plant chlorophyll ester reductase, and SPAD reduction is caused by factors such as chlorophyll degradation 39 , 42 . The gas exchange parameters (Ci and Tr) are limiting factors for CO 2 diffusion and immobilization, and are related to the activities of CO 2 immobilized enzymes, ribulose diphosphate carboxylase, and oxygenase (RuBisCO) 43 . The toxicity of Cd can be mediated by increasing the carboxylation efficiency of RuBioCO 44 . In this study, the photosynthetic parameters Pn, Gs, Tr, and Ci of rice decreased with increasing Cd concentration (Fig.  4 ). This is consistent with previous reports on Cd inhibiting plant photosynthesis 45 , where low Cd concentrations significantly inhibited plant growth and photosynthesis in rice and mustard 45 , 46 . The inhibition of photosynthesis induced by Cd is usually attributed to the inhibition of key enzyme activities in the Calvin cycle and photosynthetic electron transport chain 47 , and this negative effect can be alleviated through the supply of Si. When Si is sprayed on the leaves, the plant toxicity of Cd is reduced, and the inhibition of Cd on photosynthesis is reduced, thereby improving the performance of photosynthesis. Pn is a determining factor in plant growth 48 . In this study, the increase in Pn value after foliar Si spraying treatment may be attributed to the increase in Gs and Tr, which accelerates the effective carbon assimilation period of rice leaves and thus accelerates the accumulation of photosynthetic products. Therefore, Si can increase the SPAD value of rice leaves and improve photosynthesis 39 .

The changes in chlorophyll fluorescence can reflect biotic or abiotic stress 49 . The decrease in Fv/Fm and Y (II) indicates that the toxicity of Cd inhibits the photoactivation of PSII, which is due to the destruction of antennal pigments, limited electron transfer from PSII to photosystem I (PSI), and disruption of the integrity of the thylakoid membrane structure. The decrease in Fo (Fig.  5 c) means that the potential efficiency of PSII has undergone a negative change, and an decrease in NPQ (Fig.  5 b) indicates an improvement in the efficiency of photochemical reactions. In this experiment, foliar application of Si resulted in more light energy absorbed by rice plants being used for photochemical reactions and energy or carbohydrate synthesis, thereby increasing quantum yield and protecting the photosynthetic system from damage. These findings are also consistent with the results of rice photosynthetic parameters.

Cd does not participate in redox reactions in cells, but can induce the formation of reactive oxygen species (ROS) in plants 50 . Although the increase in ROS synthesis in cells poses a threat to cellular biomolecules, ROS also acts as a signaling molecule, activating stress response and defense-related genes through signaling pathways 51 . In this study, the increase in ROS production level under Cd stress was manifested as an increase in MDA content (Fig.  6 a), a decrease in SPAD (Fig.  3 ), and a decrease in leaf photosynthetic gas exchange (Fig.  4 ). These findings are consistent with previous studies 52 , 53 . In previous research findings, Cd toxicity was found to have a negative impact on various physiological, biochemical, and metabolic processes in plants 2 , 54 . Research has shown that the toxicity of Cd to maize can induce the production of H 2 O 2 and MDA 55 . However, the mediation by Si can reduce the final product of lipid peroxidation, namely the MDA content, which helps to reduce membrane permeability and maintain its integrity 56 . Under Cd toxicity, various enzymatic and non-enzymatic antioxidant defense systems are activated to control the production of ROS. Enzyme antioxidants, including SOD , POD, and catalase (CAT), are another defense system. SOD converts superoxide radicals into H 2 O 2 , which appears in plant tissues as a result of Cd stress. H 2 O 2 is a powerful oxidant that accumulates in plant tissues through SOD channelization reactions. It is blocked by the circulation of ascorbic acid glutathione. In addition to H 2 O 2 , another toxic oxide is heme oxygenase-1 (OH-1), which can react with all large molecules. SOD can prevent the formation of OH-1 in plant tissues 57 . POD can alter ROS levels in plants due to its role in consuming and clearing H 2 O 2 . Unlike SOD, POD has a high affinity for H 2 O 2 . However, POD can convert H 2 O 2 into H 2 O and oxygen (O 2 ) 58 . In this study, Si application significantly increased the activity of POD and SOD (Fig.  6 b and c) ( P  < 0.05). This is consistent with previous research results, which showed that Si application increased SOD activity in wheat and sorghum plants 50 , 54 . Si application increases POD activity in wheat leaves under Cd stress 59 . Similarly , Si treatment reduces the production of ROS and promotes enzymatic and non-enzymatic antioxidants for ROS clearance 60 .

Cd exposure can cause a range of harmful effects on organisms, including humans. Therefore, understanding the mechanisms of Cd uptake, translocation and accumulation in rice is important for strengthening strategies to effectively reduce Cd. In the future, the effect of foliar Si spraying on Cd accumulation at stem nodes and internodes of rice must be further enhanced. It can both efficiently control the transfer of Cd to the critical part of the grain and reduce the Cd contamination of rice in the soil.

This study demonstrated that Cd stress increased the Cd content in rice roots, stems, and leaves, decreased the SPAD of rice leaves and photosynthetic efficiency of rice leaves, inhibited the activities of SOD and POD in rice leaves, increased the MDA content in rice leaves, and inhibited rice growth. After applying Si, the Cd content of brown rice can be reduced, the SPAD of rice leaves can be increased, the photosynthetic characteristics of rice leaves can be improved, the SOD and POD activities of rice leaves can be increased, the MDA content of rice leaves can be reduced, and rice yield can be promoted.

Experimental research and feld studies on plants statement

In the study only cultivated plants were used which are neither endangered nor at risk of extinction. We confrm that their handling was performed in compliance with relevant institution, national and international guidelines and legislation.

Data availability

Data is provided within the manuscript or supplementary information files.

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Acknowledgements

We thank Guizhou University, China for providing the funding and facilities to carry out the experimental work presented in this study.

This study was supported by the National Natural Science Foundation of China (4216070281); Key Laboratory of Molecular Breeding for Grain and Oil Crops in Guizhou Province (Qiankehezhongyindi (2023) 008); Key Laboratory of Functional Agriculture of Guizhou Provincial Higher Education Institutions (Qianjiaoji (2023) 007).

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Hongxing Chen, Xiaoyun Huang, Hui Chen, Song Zhang, Tengbing He & Zhenran Gao

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H.C. (Hongxing Chen) and Z.G. wrote the main manuscript text, X.H. prepared Figs.  1 – 3 , H.C. (Hui Chen) conducted a format analysis, S.Z. and C.F. prepared Figs.  4 – 6 , H.C. (Hongxing Chen), C.F., T.F., T.H. and Z.G. conducted supervision. All authors reviewed the manuscript.

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Chen, H., Huang, X., Chen, H. et al. Effect of silicon spraying on rice photosynthesis and antioxidant defense system on cadmium accumulation. Sci Rep 14 , 15265 (2024). https://doi.org/10.1038/s41598-024-66204-9

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Parkinson’s Research Surges Ahead

by Denis Storey July 2, 2024 at 10:04 AM UTC

Clinical relevance: Parkinson’s research has advanced significantly, with notable discoveries made before the passage of the National Plan to End Parkinson’s Act in late May.

• A study found that individuals over 50 with new-onset anxiety have twice the risk of developing Parkinson’s.
• Researchers identified the GUCY2C receptor as a potential defense against dopamine neuron loss in Parkinson’s patients.
• These findings suggest that targeting GUCY2C could slow Parkinson’s progression and that its levels might serve as an early biomarker for the disease.

Parkinson’s research has been accelerating even before Congress passed the “National Plan to End Parkinson’s Act” in late May. A rare act of unity from a chronically divided legislature.

“As we eagerly await the bill to be signed into law, we applaud members of Congress for their bipartisan support and recognition of one of the most pressing healthcare issues of our day,” Parkinson’s Foundation President and CEO John L. Lehr said in a press release .

Even so, it’s been a busy – and enlightening – summer of research results for anyone living with Parkinson’s.

Study Exposes Link Between Anxiety and Parkinson’s

A paper in the British Journal of General Practice reveals that the risk of developing Parkinson’s is twice as high for those with anxiety .

A team of researchers at the University College of London Institute of Neurology, led by Professor Anette Schrag, combed through the primary care data of nearly 1 million patients in the United Kingdom between 2008 and 2018. Specifically, the researchers sought out the nearly 110,000 patients who developed anxiety after the age of 50. They then compared them to 878,256 matched controls without anxiety.

Subsequently, the study’s authors tracked the presence of the disease’s features, from trouble sleeping to balance impairment, “from the point of their anxiety diagnosis up until one year before the date of a Parkinson’s diagnosis, to help them understand each group’s risk of developing Parkinson’s over time and what their risk factors might be.”

“Anxiety is known to be a feature of the early stages of Parkinson’s disease, but before our study, the prospective risk of Parkinson’s in those over the age of 50 with new-onset anxiety was unknown,” the paper’s co-lead author, Juan Bazo Alvarez, MD explained. “By understanding that anxiety and the mentioned features are linked to a higher risk of developing Parkinson’s disease over the age of 50, we hope that we may be able to detect the condition earlier and help patients get the treatment they need.”

The researchers also confirmed that symptoms such as depression, sleep disturbance, fatigue, cognitive impairment, hypotension, tremor, rigidity, balance impairment, and constipation, are risk factors for anxiety sufferers.

“Anxiety is not as well researched as other early indicators of Parkinson’s disease,” co-lead author and UCL Queen Square Institute of Neurology Professor Anette Schrag added. “Further research should explore how the early occurrence of anxiety relates to other early symptoms and the underlying progression of Parkinson’s in its early stages. This may lead to better treatment of the condition in its earliest stages.”

The Body Already Has A Defense Against Parkinson’s?

More recently, a new study sponsored by the Parkinson’s Foundation appears to have identified the brain receptor GUCY2C as a potential target for mitigating dopamine loss in Parkinson’s patients.

Researchers already knew that the decay of dopamine-producing neurons – vital in movement and mood regulation – is to blame for the development of the degenerative disorder. Mitochondrial dysfunction contributes to this neuronal death.

Related research had shown that GUCY2C, initially found in the gut, is also present in the substantia nigra pars compacta (SNpc).

The new research, led by Scott Waldman, MD, digs deeper into GUCY2C’s role in protecting mitochondria and preventing neuron degeneration in the first place. In Parkinson’s patients, dopamine neurons exhibit an increased number of GUCY2C receptors.

Waldman’s experiments with mice showed that the absence of GUCY2C led to mitochondrial dysfunction, oxidative stress, and cell death in brain areas plagued by Parkinson’s. When exposed to a toxin that induces PD symptoms, mice lacking GUCY2C had higher rates of dopamine neuron death. On the other hand, mice with GUCY2C showed an increased production of the receptor, illustrating its defensive role.

These findings suggest the body’s increase in GUCY2C in those with the disease might be a natural defense against neuronal damage. Targeting GUCY2C or enhancing cGMP levels could be therapeutic strategies to protect dopamine neurons, potentially slowing PD progression.

The study also indicates that GUCY2C levels could serve as an early biomarker for Parkinson’s. While developing GUCY2C-targeted treatments will take time, this research opens new avenues for Parkinson’s therapies.

Further Reading

Blood Test Offers Parkinson’s Early Warning System

How Two Sisters May Change Our Understanding of Parkinson’s Disease

3 Key Updates in Parkinson’s Disease

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Epilepsy, Antiepileptic Drugs, and Adverse Pregnancy Outcomes, 2: Major Congenital Malformations With Antiepileptic Drug Monotherapy

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If you have ever been uncertain about how to evaluate patients with a chronic psychotic illness or struggled over how best to manage treatment-resistant schizophrenia, then this case vignette and discussion should prove useful.

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POLONCARZ ANNOUNCES WORKING GROUP TO STUDY HOW ERIE COUNTY PROVIDES INDIGENT DEFENSE

Working Group to Research, Plan, and lay Groundwork for Creation of 

Erie County Public Defender’s Office 

ERIE COUNTY, NY— As part of his promise to the public made during his 2024 State of the County Address , Erie County Executive Mark C. Poloncarz today announced the members of a working group of local attorneys and judges who will be tasked with analyzing how Erie County currently provides indigent defense and study ways to provide the highest quality criminal defense and Family Court representation through the most cost effective process.

“For decades, Erie County has borne millions of dollars in extra costs associated with defending individuals charged with crimes who cannot afford an attorney. It's a fundamental constitutional right that the county takes very seriously, but this critical work is outsourced to external agencies as no Erie County office currently exists to handle this mandated service,” said Erie County Executive Mark C. Poloncarz. “The establishment of this working group is the first step towards improving the quality of public defense in Erie County, providing much-needed oversight to the indigent defense agencies, and finding efficiencies to save taxpayer dollars. This is a dynamic, diverse and accomplished working group and I thank these respected professionals for volunteering their time and expertise to research ways to improve our system.”

“While subcontracting with the Legal Aid Bureau of Buffalo and the Erie County Bar Association for the provision of indigent defense may have provided a taxpayer value over a public defender’s office in the past, that is no longer obviously the case,” added Erie County Budget Director Mark Cornell.   “Mostly due to the increase in hourly rate for the Assigned Counsel program included in the 2023-24 NYS Budget, the indigent defense program’s cost has nearly doubled over the past two years from $13.1 million in 2022 to $25.8 million in 2024.” 

Working group co-chairs will be the Honorable Susan Eagan, Erie County Court Judge and Supervising Criminal Court Judge for the 8th Judicial District, and former Erie County District Attorney and partner at Lippes Mathias LLP John Flynn .

Members of the working group include:

• Brian Melber, criminal defense attorney and partner at Personius Melber and newly elected Vice President of the Bar Association of Erie County ;
• Joel Daniels, criminal defense attorney;
• James Harrington, criminal defense attorney partner at Harrington & Mahoney;
• Jessica Kulpit, criminal defense attorney;
• Marissa Washington, Support Magistrate in Erie County Family Court and current President of the Women’s Bar Association of the State of New York, WNY Chapter;
• Marianne Mariano, Federal Public Defender for the Western District of New York State; 
• Ayoka Tucker, Family Court Attorney whose primary practice is within Family Law; 
• Hon. Erin Peradotto, NYS Supreme Court justice (retired), partner at Harris Beach; 
• Erie County legislator John Gilmour (9th District), a criminal defense attorney in private practice; and, 
• Erie County legislator Michael Kooshoian (3rd District), a former Assistant District Attorney. 

Also participating in the working group are County Attorney Jeremy Toth, Deputy County Attorney Kristen Walder, and Assistant County Attorney Ifeoluwa Popoola.  Deputy County Attorney Walder is currently responsible for drafting the myriad contracts with legal service providers and Assistant County Attorney Popoola, President of the Minority Bar Association, formerly worked for Legal Aid in Buffalo City Court.

• Open access
• Published: 04 July 2024

Cytological and ultrastructural investigation of pathogen infection pathway and host responses in asparagus stem infected by Phomopsis asparagi

• Liping Sun 1 , 2 ,
• Yange Li 1 ,
• Xiaoting Li 1 ,
• Xinyi Ruan 1 ,
• Yueyan Zhao 1 ,
• Ruidong Wen 1 ,
• Shuaijie Wei 1 ,
• Ning Chen 1 ,
• Yulan Zhang 1 ,
• Shufen Li 1 &
• Wujun Gao   ORCID: orcid.org/0000-0001-8160-7776 1  

Phytopathology Research volume  6 , Article number:  32 ( 2024 ) Cite this article

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Asparagus stem blight, a highly destructive disease in global asparagus cultivation, is caused by the fungus Phomopsis asparagi . However, the underlying mechanisms of the infectious process and pathogenesis of P. asparagi remain poorly understood. This study aims to elucidate the infection event of P. asparagi at the cytological and ultrastructural levels in asparagus stem through a microscopic observation. The host responses were also examined by microscopic observation and fluorescent probe. It revealed that P. asparagi germinated at either the tip or the middle of the conidia to produce short germ tubes on the surfaces of the asparagus stem at 20 h post-inoculation (hpi). The germ tubes penetrated the host cell wall with appressorium-like structures or narrow pegs at 1 day post-inoculation (dpi). At 3 − 5 dpi, a large number of P. asparagi hyphae colonized the epidermal cells. The hyphae were found to grow both intracellularly and intercellularly. The movement of hyphae between cells was facilitated by constricted invasive hyphae pegs. The hyphae exhibited bidirectional intracellular growth, extending and branching along the inner side of the cell wall within the stem cortex and towards the central cylinder. The fungal colonization resulted in cellular damage in plants, which is characterized by plasmolysis, rupture of the cell wall, and disruption of the cytoplasm. At 11 dpi, the fungi penetrated the parenchyma cells, and the fungal pycnidia were formed. At 13 dpi, the fungi penetrated the stem center parenchyma cell, where the conidia were released. In addition, the host defense response was investigated, which revealed a notably reduced germination rate of conidium, the formation of callose analogs, and the reactive oxygen burst. These findings provide unexpected perspectives on the infection process and host response in P. asparagi -plant interaction.

Asparagus ( Asparagus officinalis L.), a perennial and dioecious species with a long lifespan, has been cultivated for over 2500 years and holds significantly economic value. It is widely recognized as the “king of vegetables” in the international market due to its rich nutrition and numerous health benefits, including antioxidant, anti-inflammatory, and anti-hepatotoxic properties (Yang et al. 2020 ). The occurrence of asparagus stem blight caused by Phomopsis asparagi (Sacc), commonly referred to as the “cancer” of asparagus, has a severe impact on both yield and quality (Yang et al. 2012 ). This disease is prevalent in asparagus-producing regions, such as Asia, North America, Africa, Europe, and Southern Australia (Davis 2001 ; McKirdy et al. 2002 ; Elena 2006 ; Yang et al. 2012 ; Iwato et al. 2014 ; Zaw et al. 2017 ; Thao and Dung 2019 ), with more severe epidemics in Asian countries. China is the leading producer of asparagus in the world, but it faces a significant threaten of stem blight now, which is hampering the sustainable development of asparagus production (Zhang and Araki 2017 ). In particular, during the nutritional growth period of asparagus, warm and humid weather is more prone to facilitating the disease outbreak. In worst cases, if the plants were infected at very early stage, the disease would progresses throughout the growing season and would cause yield loss up to 100% (Elena et al. 2006 ).

Previous studies have demonstrated that the causal pathogen responsible for asparagus stem blight is a hemibiotrophic filamentous fungus, which mainly damages young stems with occasional infections on branches and leaves (Uecker and Johnson 1991 ). The initial manifestation of the fungus is the development of small lesions or spots on the surface of the asparagus stem. These lesions progressively expand and produce yellow-brown spindle-shaped spots (Sonoda et al. 1997 ). Pycnidia, usually appearing at the core of a spot, serves as a secondary source of infection. The infected stems often die rapidly, ranking it as a more devastating pathogen over other asparagus diseases. Control measures of this pathogen include the application of fungicide and the implementation of cultivation practices. Yet, the complete eradication of this disease remains challenging (Takeuchi et al. 2018 ). Meanwhile, the potential risk of fungicide resistance evolved in the fungi over time and the increasing environmental pollutions pose limitations on their use. Thus, a more feasible strategy is to breed new asparagus varieties with high disease resistance.

The understanding of P. asparagi’ s infection process is essential for breeding plans and disease managements. Additionally, this research can also help us to understand the interaction mechanisms between P. asparagi and asparagus. Following the development of modern microscopy techniques, the infection process for certain pathogenic fungi has been widely studied, such as Magnaporthe oryzae which causes rice blast, and Fusarium graminearum which is responsible for wheat scab, and Verticillium dahlia kleb, which is the causal agent of Verticillium wilt. The hemibiotrophic fungus M. oryzae , as a model fungus pathogen, has been extensively studied at cytological level. This fungus deploys a penetration peg to pierce the surface of the host plants (Howard and Valent 1996 ; Talbot 2003 ). Once reaching the lumen of the tissues, the penetration peg would expand, forming the slender filamentous primary hypha. The peg serves as a conduit for the transportation of the nucleus and cytoplasmic contents from the spores into the primary hypha. The primary hyphae then undergo differentiation, which finally develops to the thicker and bulbous invasive hyphae. These invasive hyphae proceed and occupy the first invaded cells and then they invade the adjacent cells through plasmodesmata (Kankanala et al. 2007 ).

Upon infection of a pathogen, host cells undergo the formation of mastoid structures, callose deposition, and programmed cell death as a defense mechanism to impede or hinder pathogen invasion (Van Baarlen et al. 2004 ; Yin et al. 2017 ; Fincher 2020 ). In response to pathogen attacks, plants produce pathogenesis-related (PR) proteins, some of which are enzymes that degrade chitin and the (1,3)- and (1,3;1,6)-b-glucans of the fungal cell wall (Roulin et al. 1997 ; Kasprzewska 2003 ). Overexpression of these hydrolytic enzymes proved to be successful in enhancing the resistance of crops (Ali et al. 2018 ; Moosa et al. 2018 ). The oxidative burst represents an early reaction of plant tissues to pathogenic fungi, leading to swift production and release of Reactive Oxygen Species (ROS). These ROS include superoxide (O 2 − ), hydroxyl radical (OH·), and hydrogen peroxide (H 2 O 2 ) (Wojtaszek 1997 ; Bolwell 1999 . Both O 2 − and OH· exhibit high activity with dismutation to H 2 O 2 . H 2 O 2 is relatively stable and can be detected (Wojtaszek 1997 ). ROS has been proposed with antimicrobial properties and to play a role in intercellular communication (Fichman et al. 2023 ).

Previous researches primarily concentrated on the biological characteristics and control measures of P. asparagi . It is largely unknown for the infection pathway and the interaction of P. asparagi with plants.

In this study, we used a combination of microscopy techniques, including confocal laser scanning microscope (CLSM), scanning electron microscopy (SEM), and transmission electron microscope (TEM), to investigate the infection process, infection structures, and cell-to-cell movement of P. asparagi . Furthermore, the host responses, including callose accumulation and H 2 O 2 production and distribution, were also examined using TEM and fluorescent probe method. The findings unravel the pathogeneicity of P. asparagi and may be helpful for the disease control.

Isolation and identification of the causal pathogen

The causal pathogen was isolated from a diseased asparagus stem which exhibited typical symptoms of stem blight (Fig.  1 ). To identify the isolated pathogen, we employed the methods of morphology examination, rDNA ITS analysis, and a pathogenicity test. Initially, the mycelia of this pathogen display a fluffy white shape on the medium and then they turned grayish-white to yellowish-green. Within the black sporodochium, the pycnidia were formed either singly or in aggregates. The aerial hypha with the septum produced a short or long lateral branch. The conidia sizes are 1.8–3.3 μm × 6.0–8.8 μm, oblong or spindle-shaped, unicellular, colorless, with 1 − 2 oil droplets at each end. The ITS regions were PCR-amplified, which produced a fragment approximately 600 bp. A sequence comparison showed that the ITS shared a 99% sequence identity with that of P. asparagi. The pathogenicity was examined by inoculating asparagus stems. The infected stems all displayed typical stem blight symptoms, being consistent with the field disease symptom. These results were consistent with previous reports (Uecker and Johnson 1991 ; Yang et al. 2012 ; Zheng et al. 2015 ), and the pathogen was identified as Phomopsis asparagi (Sacc) (NCBI No: JQ614007.1).

The isolation and identification of the causal pathogen of asparagus stem blight. A diseased stem is cleaned and sterilized, then a sterilized knife is used to cut the stem longitudinally, and take a small area of diseased tissue culturing on potato sucrose agar (PSA) medium, followed by the subculturing purification. The identity of the causal pathogen includes the characteristics in medium and conidia, hyphae morphological, molecular identification, and pathogenicity assay

Infection process  and the appearance of P. asparagi on the asparagus stem surface

The infection process of P. asparagi on asparagus stems was observed at a series of time points by SEM. The results showed that the conidia adhered to the stem surface, and only about 8% of conidia germinated at 20 hpi (Fig.  2 a). Each conidium produced a single or multiple germ tubes from one end, two ends, or the middle of the conidium (Fig.  2 b − d). At 1 dpi, germ tubes invaded the epidermal layer by forming an appressorium with an enlarged tip (Fig.  2 b, c); however, some of them became tapered and invaded the epidermal cells (Fig.  2 d). Most developing germ tubes did not immediately infect host tissues but instead, they developed to runner hyphae. The runner hyphae produced multiple morphological appressorium-like structures, such as bifurcate appressorium (Fig.  2 e − h), foot appressorium (Fig.  2 i), and irregular appressorium (Fig.  2 e). The terminus of the germ tube was swollen and differentiated into spherical appressoria (Fig.  2 e, g). Some had an obvious infection peg at the front of the appressorium (Fig.  2 g), while others did not form an infection peg (Fig.  2 e). Interestingly, P. asparagi may not enter host tissue by stomata as do many other fungi, even when they were in close contact with them (Fig.  1 f). Penetration pores of about 0.5 μm in diameter were visible where hyphae were detached from the surface of the cell wall (Fig.  2 h), indicating that the penetration peg was markedly constricted. The appressorium and hyphae were surrounded by gelatinous materials that may help them adhere to the stem surface (Fig.  2 c, f − h). The runner hyphae grew and branched radially on stem surfaces or grew beneath the epidermis, forming hyphal nets at 3 dpi (Fig.  2 j − l). No hyphal nets were found on the host surface after 5 day of inoculation. At the later stage of the infection (at about 11 dpi), many humps-like sporodochia were observed (Fig.  2 m). Finally, the epidermal layer were ruptured and a large number of conidia were released at around 13 dpi (Fig.  2 n, o), in which the P. asparagi completed its life cycle.

The infection process and appearance of P. asparagi on asparagus stems. a The conidia germinated with a germ tube emerging from one end or middle of the conidium on the asparagus stem at 20 hpi. b A conidium germinated two germ tubes, and one germ tube invaded with an enlarged tip (arrowhead). c A conidium germinated three germ tubes, and one germ tube invaded with an enlarged tip (arrowhead). d The tip of one germ tube tapered and invaded the host cell surface (arrowhead). e , g , h , and i Various infection structures were formed. f The germ tube bypassed the opening stomata. h Penetration pores (arrowheads). j and k The hyphae network at 3 dpi and 5 dpi. l Residual hyphae net (11 dpi). m Sporodochium was formed underneath the epidermis. n and o New conidia were released through a stoma or surface. gc, germinated conidium; gt, germ tubes; rh, runner hyphae; s, stomata; ap, appressorium; sp, sporodochium; c, conidium

The dynamics of fungal colonization in host tissues

In order to reveal the detailed colonization process, typical disease progression was observed. The hyphae inside the host stem were monitored at 1, 2, 3, 5, 7, 9, 11, and 13 dpi via CLSM, using WGA-AF488/PI to show the fungal infection dynamics.

There were no conspicuous symptoms at the inoculation site up to 2 dpi. The microscopic observations revealed that, at 1 dpi, P. asparagi could successfully penetrate asparagus stems, which is consistent with the results of SEM. At 2 dpi, the fungal hyphae grew inside the stem and invaded the adjacent cells. At 3 dpi, small light brown lesions were visible at the inoculation sites, and a large number of P. asparagi hyphae colonized the epidermal cells. At 5 dpi, necrosis was seen at the center of the lesion, and the hyphae suffused the epidermis and sclerenchyma layers, indicating a well-established necrotrophic phase (Fig.  3 a). The statistical analysis showed that the disease indexes were at level 3 or below, and the lesion area was below 60% at 1 − 5 dpi (Fig.  3 b, c). Then, the lesions continued to expand, forming yellowish-brown and spindle-shaped lesions. Notably, majority of the lesions merged at 7 to 9 dpi (Fig.  3 a). The disease indexes reached the highest level 5, and the lesion almost covered the entire stem (Fig.  3 b). Additionally, the fungal hyphae rapidly expanded towards the central medulla (Fig.  3 a − c). At 11 dpi, the stem wilt was visually apparent. The pycnidium formed a papillary orifice and appeared at the central part of the lesions. The hyphae reached the parenchyma cell and grew towards the central cylinder (Fig.  3 a). The ratio of fungi hyphae was up to 80% (Fig.  3 d). At 13 dpi, the stem was completely invaded. Laser confocal imaging showed that P. asparagi reached the stem center parenchyma cells and full-filled the cells with hyphae (Fig.  3 a, d).

The microscopic characterization of hyphae colonization in asparagus stems. a The red box indicates the sampling points on the stems. Fungal cells were stained with WGA-AF488 (green), and the plant cell wall was stained with PI (red). Scale bars : 100 μm. b , c , and d The disease indexes, the ratio of the lesion area, and the ratio of fungal hyphae at eight-time points after fungi inoculation. Data from three biological replicates were analyzed by one-way ANOVA. Different letters indicate statistically significant differences ( P ⩽ 0.01)

P. asparagi  colonize inside of host tissues

To further investigate the P. asparagi colonization and proliferation in host tissues, we used CLSM and SEM to observe transverse sections of P. asparagi -infected stems at 11 dpi. The CLSM results showed that hyphae spread over the whole cortical tissues and parenchyma cells of the stems, whereas only few hyphae were detected in vascular tissues. The pathogen hyphae were observed in the parenchymal tissues (Fig.  4 a). Strikingly, the intercellular hyphae were thick and solid with a diameter of about 3–5 μm, which was similar to that in vitro culture medium and about three times to the diameter of intracellular hyphae (1–2 μm) (Fig.  4 b, c). The hyphae ramified and became swollen when they breached the cell wall (Fig.  4 d). In a longitudinal section at 11 dpi, pathogen hyphae were found expanding beneath the epidermis of host cells, where they formed pycnidia. Importantly, the cells in the epidermis regions were not positive by PI staining, indicating that the hyphae had lost membrane integrity (Fig.  4 e, f), which agrees with their necrotic appearance.

P. asparagi colonization and expansion patterns in host tissues. a Hyphae distribution in the tissue. b Intercellular (solid arrow) and intracellular (dotted arrow) hyphae. c Intracellular hypha branching and morphological changes. d Hypha became swollen upon contacting with the cell wall. e Pycnidium was formed underneath the epidermis. f 3D reconstruction was obtained from 18 optical sections acquired with a z-interval of 1.5 μm

Cell-to-cell movement of  P. asparagi inside the asparagus stem

Through an extensive CLSM observation for cell-to-cell movement of P. asparagi , we observed that the hyphae had a slightly swollen end and experienced extreme constriction during penetration of the cell walls. Once they traversed, the pegs expanded to form the filamentous hyphae in the newly invaded cells with normal size, followed by the rapid proliferation within the cell (Fig.  5 a − d, e − h). The intracellular growth of the hyphae was bidirectional, with growth and ramification along the inner side of the cell wall within the stem cortex, and grew towards the central cylinder (Fig.  5 i, j, k).

P. asparagi proliferation and cell-to-cell movement. a  −  d and e  −  h The dynamic process of invasive hyphae tip swelled and then crossed the cell wall, followed by branching growth. a  −  d and e  −  h were layer scanning photos of the same sites, respectively. Arrows indicate the site of hyphae penetration. i Hyphae constriction during penetration. j 3D reconstruction is obtained from 39 optical sections with a z-interval of 1.5 μm. k A proposed model depicting P. asparagi proliferation and cell-to-cell movement. Scale bars: 10 μm

Host subcellular changes of P. asparagi -infected stems

The TEM observations showed that the healthy cells had normal sub-cellular structure (Fig.  6 a). However, in the infected tissues, the cytoplasm of host cells was coagulated, and the dark deposits were found to surround the hyphal cell walls, resulting in ambiguity of organelles. The cell wall contacting hyphae became darker, probably because of callose-like material deposition, which may restrict the hyphae extension (Fig.  6 b). Additionally, the cytoplasmic matrix of adjacent infected host cells became more electron-dense (Fig.  6 c). The host cell wall close to the hyphae was partially digested (Fig.  6 d). Cell membrane contraction led to plasmolysis, and the electron density of protoplasm was increased (Fig.  6 e). The chloroplasts in the host cell were swollen and less dense (Fig.  6 f). The host cytoplasm and organelles, such as chloroplasts, were degenerated, and mitochondrial cristae were blurry, granulated, locally vacuolized, and multivesicular bodies were formed (Fig.  6 g). The collapse host cells were plasmolysized, which further impaired the cell membrane, leading to the cytoplasm cracking into lumps (Fig.  6 h).

Ultrastructure of the healthy and P. asparagi- infected stems at 3 dpi. a Healthy cells containing intact chloroplasts, mitochondria, nuclei, and large vacuoles. b Callose-like substance were deposited (black arrow) and dark deposits surrounded the hyphae (white arrow). c The cytoplasmic matrix of infected adjacent cells were more electron-dense. d Host cell wall was degraded (black arrow). e Plasmolysis of the infected cells (black arrow). f Chloroplasts were swollen. g Structural variations of chloroplast, mitochondrion, and multivesicular body. h Collapse of the infected host cells. n, nucleus, ch, chloroplasts, mit, mitochondria, v, vacuoles, hy, hyphae, s, septum, miv, multivesicular body. Scale bars: 2 μm

The responses of asparagus to  P. asparagi infection

In the middle and late stages of infection, we used SEM and CLSM to observe the surface and intracellular hyphae of the stem. We found that a large number of conidia on the host surface couldn’t germinate, which eventually shrank and died. Only less than 10% of them were able to successfully germinate after 3 dpi (Fig.  7 a, e). At 5 dpi, almost no hyphae were found on the host surface. Occasionally, a few residual hyphae were surrounded by callose-like substances (Fig.  7 b − d). In the stem center, clear and intact cellular outlines could be stained by PI at 11 dpi (Fig.  7 f), indicating that asparagus stem cells may be alive at this stage even after the extensive proliferation of P. asparagi inside them. By PI staining, we observed a few dead invasive hyphae at this stage. At 13 dpi, the clear and intact cellular outlines of the asparagus stem cortical tissue cells were not able to be seen, where more dead invasive hyphae were also be observed by PI staining (Fig.  7 g).

Observation of defense response in the host stem surface and in tissues. a Conidia cannot germinate that had eventually shrunk on the stem (3 dpi) ( n  = 1000, three independently repeated experiments). b , c , and d Stem surface hyphal were surrounded by the callose-like substances (amorphous material) (11dpi). e Statistics assays of conidia germination rates at 1 and 3 dpi. f The cell wall of stem tissue and a few hyphae were stained by PI at 11 dpi. g The content of the infected epidermic cells was disintegrated by PI staining at 13 dpi. Scale bars: 30 μm

The temporal-spatial accumulation of H 2 O 2 during pathogen infection

During the fungal colonization, intracellular H 2 O 2 production was analyzed using the corresponding fluorescent probes. Compared to the basal level of H 2 O 2 in uninfected stems (Fig.  8 a, d), the penetration of hyphae led to a rapid generation and release of H 2 O 2 in both the epidermis and vascular system after 1 day of inoculation. The accumulation of H 2 O 2 culminated at its peak concentration at 3 dpi, and then decreased markedly (Fig.  8 c, d). At 5 dpi, H 2 O 2 mainly were distributed in the epidermis and vascular bundles. However, at 7 dpi, when hyphae reached the cortex (Fig.  8 b), H 2 O 2 accumulation was seen throughout the parenchyma cells in the entire stem. At 11 dpi and 13 dpi, very little H 2 O 2 was produced in the epidermis and vascular system (Fig.  8 c), less than that at 1dpi (Fig.  8 d).

H 2 O 2 accumulation and location by a time-course observation in the plants infected by P. asparagi . a H 2 O 2 fluorescence images for mock-treated samples. b  P. asparagi colonization in the stem tissues. c H 2 O 2 fluorescence images for infected stems. ROS was stained with H 2 DCF-DA (green fluorescence); Chlorophyll showed red autofluorescence. Fungal cells were stained with WGA-AF488 (green fluorescence), and the plant cell wall was stained with PI (red fluorescence). Scale bars: 100 μm. d Quantification of the H 2 DCF-DA fluorescence intensities in a and c . Data from three biological replicates were analyzed by Student’s t -test. Different letters indicate significant differences ( P ⩽ 0.01)

Pathogenic fungi frequently employ specialized infection structures, such as appressorium or infection cushions, to facilitate their invasion on host plants. For example, the rice blast pathogen M. r. oryzae achieves entry into host cells through mechanical penetration of the cuticle, accomplished by the formation of a dome-shaped and melanized appressorium (Howard and Valent 1996 ). Similarly, F. graminearum , the fusarium head blight (FHB) in cereals, and B. cinerea , the grey mold disease, penetrate plants by means of infection cushions (Mentges et al. 2020 ; Choquer et al. 2021 ). In the present study, the utilization of SEM revealed that P. asparagi mainly exhibited two specialized morphological structures, the appressoria and penetration pegs, which substantially facilitate colonization. Furthermore, the conidia and hyphae of P. asparagi were found to secrete mucilaginous substances on the host surface, potentially contributing to their survival and dispersal. Notably, apart from the penetration pore, no clear damage was observed in these tissues, indicating that it necessitates further investigation for the underlying mechanism in host penetration. Additionally, it was observed that certain pathogen hyphae were capable of invading host tissues through stomata without any discernible morphological alterations (Steinberg 2015 ; Yin et al. 2017 . In our study, we observed fungal penetration exclusively through the epidermis, with rare instances of penetration through the opening stomata, suggesting that stomata do not serve as the primary pathway for infection. This finding aligns with previous research on M. oryzae and Exserohilum turcicum , which suggests that stomata may not contribute to the entry of these pathogens (Minker et al. 2018 ; Kotze et al. 2019 ; Qiu et al. 2019 ).

The macroscopic symptoms observed in asparagus stem after pathogen inoculation are consistent with those observed in the field and previous studies (Yang et al. 2016 ). Symptoms were observed to manifest at 3 − 5 dpi, with a larger area affected at 7 − 9 dpi. The stem displayed withering, and numerous small black pycnidia, which were scattered throughout the affected region within 12 − 14 days. Microscopic examination revealed that the fungal hyphae penetrated the plant surface within 1 day of inoculation, and reached the sclerenchyma sheath cells at 2 dpi. They subsequently formed sporodochia at 7 − 9 dpi. Furthermore, the hyphae exhibited extensive spreading, resulting in severe stem blight at 7 dpi, and conidia were released at 14 − 16 dpi. Prior to 5 dpi, the majority of hyphae were confined to the epidermis. However, during the middle and late stages of infection, there was a rapid expansion of hyphae within the tissue, leading to an acceleration of stem wilting. This result may be attributed to the inhibition of expansion by epidermal cells and the dense sclerenchyma sheath cells.

Through ultrastructural investigations, we found that the infection sites exhibited fungi proliferation and divergence, resulting in rapid dissemination of both inter- and intracellular hyphae. In this study, the inherent haustoria were not observed at the P. asparagi -asparagus stem interface. Haustoria, which are specialized feeding structures formed by biotrophic fungi or oomycetes, serve as a means for these pathogens to acquire nutrients from their hosts (Slusarenko and Schlaich 2003 ; Yi and Valent 2013 ). The mechanism by which the pathogen obtains nutrition from the host remains unclear. Notably, the process of cell-to-cell movement of the hyphae, characterized by initial swelling followed by extreme constriction, bears a resemblance to the formation of an appressorium penetration peg. Both structures exhibit similar diameters when examined by SEM, suggesting that P. asparagi exhibited biotrophic growth by penetrating the epidermal walls and cell-to-cell movement by a flexible invasion peg, which is commonly observed in biotrophic pathogens. These results align with previous studies for rice blast disease and FHB (Kankanala et al. 2007 ; Qiu et al. 2019 ). The swelling structure observed in the hyphal tip is likely a result of cytoplasm accumulation in response to the mechanical resistance of the plant tissue (Eynck et al. 2007 ). However, the mechanism underlying cell-to-cell invasion requires further investigation.

Pathogen secreted effector triggered plant immune responses are typically accompanied by cell death resulting from hypersensitive responses (HR) (Pitsili et al. 2020 ; Yin et al. 2022 ). Localized cell death is employed by plants to impede the dissemination of pathogens, and mitochondria are associated with HR (Lam et al. 2001 ; Ordog et al. 2002 ). In this study, TEM analysis unveiled that a majority of epidermal cells displayed plasmolysis at 3 dpi. Additionally, electron-dense precipitates were observed to accumulate around the cell membrane, accompanied by cell wall collapse or complete disappearance, as well as organelle destruction, particularly the mitochondria. This observation suggests that local cell death within the epidermis could potentially contribute to disease resistance. Furthermore, it is plausible that the cell wall-degrading enzymes produced by these pathogens contribute to the degradation of the host’s cell wall, which facilitated the infected cell death.

The germination time of P. asparagi is consistent with that of the culture medium. However, there is a notable disparity in the germination rate. Some conidia germinate and a few hyphae successfully penetrate the surface of the host stem. This phenomenon may be attributed to the resistance of host stem, which inhibits conidia germination and hyphae invasion. The production of callose-like substance serves as an indication of plant defense responses. The PI staining was observed during later stages of infection, suggesting the death of hyphae. Comparable findings have been reported in wheat coleoptiles infected with F. graminearum , where hyphae vacuolization was also observed (Minker et al. 2018 ), although no vacuolated hyphae were observed in P. asparagi .

Pathogen infection process is heavily influenced by the dynamic fluctuations in ROS (Sang and Macho 2017 ). Our findings demonstrate a notable increase in H 2 O 2 levels during the later stages of infection, commencing at spore germination and persisting until the penetration on the epidermis. Moreover, at 3 dpi, the accumulation of H 2 O 2 is significantly higher, aligning with the manifestation of necrotic symptoms. This heightened presence of H 2 O 2 may be attributed to a hypersensitive response in plants, which restricts the dissemination of pathogens by inducing mitochondrial and chloroplast dysfunction, and ultimately leads to cell death. ROS serves as highly conserved intercellular stress signals, and in vascular plants, long-distance communication occurs via the vascular system (Fichman et al. 2023 ). Additionally, the death of the fungal pathogens can be induced by H 2 O 2 (Qin et al. 2011 ). In the case of P. asparagi infection, elevated levels of H 2 O 2 were observed in the epidermal cells in asparagus stems. The production and concentration of H 2 O 2 in the vascular bundle are particularly higher, and the entry of hyphae into the vascular bundle is rare. These findings indicate that H 2 O 2 primarily contributes to the resistance of P. asparagi infection.

Through the utilization of contemporary microscopy technology, a comprehensive examination of the complete infection process of P. asparagi suggests that it effectively infiltrates asparagus stems by means of appressoria-like structures or narrow pegs. The movement of hyphae between cells is facilitated by the presence of constricted invasive hyphae pegs, which extend along the inner side of the cell wall and towards the central cylinder. The host’s defense mechanisms encompass the production of callose analogs and the initiation of oxidative bursts. These findings provide new insights into the infection process and host response characteristics during interactions between P. asparagi and asparagus, thereby contributing valuable knowledge towards a more comprehensive understanding of P. asparagi pathogenesis.

Plant material

Four-year-old plants of asparagus variety ‘Feicuimingzhu’ were cultivated in pots with a diameter of 50 cm in a greenhouse. The plants were grown under a 14-hour light and 10-hour dark-light cycle, and temperatures rang from 20 to 25℃, with the relative humidity between 40 and 60%, and a light intensity of 60 mE/s/m 2 . When the plants reached a height of 6–8 cm, the stems were used for fungus inoculation.

Fungi isolation and identification

The causal fungus P. asparagi was isolated from a diseased asparagus stem that displayed typical symptoms of stem blight in an asparagus plant. A diseased stem is cleaned and sterilized with 70% ethanol, then a sterilized knife is used to cut the stem longitudinally, and take a small area of diseased tissue culturing on potato sucrose agar (PSA) medium (potato 200 g, sucrose 20 g, agar 18 g, and ddH 2 O 1000 mL), followed by the subculturing purification. The identity of the causal pathogen was primarily confirmed by traditionally morphological identification, including the characteristics in medium and conidia, hyphae morphological and pathogenicity assay. For further identification, the molecular identification by amplifying and sequencing its rDNA internal transcribed spacer (ITS). The target band was purified and sequenced in both directions using fungi amplification universal primers (ITS1: 5’-TCCGTAGGTGAACCTGCGG-3’; ITS4: 5’-TCCTCCGCTTATTGATATGC-3’), and the resulting sequences were blasted with the gene sequence in GeneBank database.

Pathogen inoculation

The isolated P. asparagi was cultured with PSA medium at 25℃ under a 12-hour photoperiod. After 12 − 14 days of incubation, when the pycnidia were produced, the conidia were washed out of the pycnidia using sterile water, which was then filtered through double-layer sterile lens cleaning paper and counted with a hemocytometer under 40 × magnification. The spore suspension for inoculations was adjusted to 1 × 10 7 spores/mL with sterile water.

Asparagus plants were inoculated with spores of P. asparagi with adjusted concentration using the vinyl cotton (VC) method (Sonoda et al. 1997 ) with minor modifications. The basal part of the tender stem was wrapped in 1 cm × 1 cm cotton strips, then 1.0 mL of P. asparagi inoculum was infiltrated gently into the cotton with a Pasteur pipette, and incubated in a growth chamber at 25℃ and 90% humidity for 3 days. Plants treated with sterile distilled water under the same conditions were used as a control. The incubated plants were then transferred to a glasshouse at 25 ± 1℃ under natural daylight. The disease symptoms were observed, and the inoculated stem tissues were harvested at each time point after infection for microscopic observations. The experiments were performed three times independently, and at least three stems were analyzed at each time point.

Observation of stem blight symptoms

The phenotypic alterations in the stem surface after the inoculation with P. asparagi were recorded using photography. The severity of the disease was assessed by employing a grading system based on the proportion of the stem area affected by lesions. 0 = No symptoms, 1 = 1 to 10% covered with lesion, 2 = 11 to 30% covered with lesions, 3 = 31 to 50% covered with lesion, 4 = 50 to 75% blights and 5 = 75 to 100% blights and plants dead.

Scanning electron microscopy observation

To observe the surface structure of fungal colonization and proliferation, we used SEM to observe the stem surface and cross sections of infected asparagus stems. The samples were fixed in a formalin-alcohol-acetic acid (FAA, 90:5:5) solution at 4℃ overnight and dehydrated in an ethanol series (50%, 70%, 80%, 90%, and twice in 100% ethanol) for 25 min per concentration. Then, they were rinsed two times in tert-butanol to replace ethanol and dried for 1–3 h. Finally, the samples were sputter coated with gold particles and observed with an S-3000 N scanning electron microscope (Hitachi, Japan).

Confocal microscopy observation

The samples were hand-cut into 60 μm thick sections and bleached with pure ethanol. They were then incubated in 10% KOH for 2–3 h at 85℃, which were further neutralized with five washing steps using phosphate-buffered saline (PBS) at pH 7.4. Subsequently, the sliced samples were stained with WGA-AF488 (catalog No. W11261, Thermo Fisher Scientific) and propidium iodide (PI) (catalog No. P4170, Sigma-Aldrich) (1 µg/mL PI, 10 µg/mL WGA-AF488; 0.02% Tween-20 in PBS, pH 7.4). Confocal images were taken by a TCS-SP8 confocal microscope (Leica, Germany). WGA-AF 488 was used to stain fungal cell walls as green using excitation at 488 nm and detection at 500–540 nm, and PI was used to stain plant cell walls as red using excitation and emission at 543 nm and 560 − 615 nm, respectively (Redkar et al. 2018 ).

Transmission electron microscope observation

The epidermis from inoculated stems at 3 dpi and mock were prepared using a razor blade to excise approximately 1 mm 3 pieces. These pieces were immediately fixed in 2.5% glutaraldehyde (pH 7.4) for 2 h. The samples were then washed three times with 0.1 M phosphate buffer (pH 7.2) and fixed in 1% osmic acid at 4℃ for 2 h. After washes, the samples were dehydrated in a graded series of ethanol, embedded in Epson-Araldite resin for penetration, and placed in a mold for polymerization. After the semi-thin sections were used for positioning, the ultrathin sections were made and collected. The sections were counterstained with 3% uranyl acetate and 2.7% lead citrate and were observed with a JEM1400 transmission electron microscope (JEOL, Japan).

Reactive oxygen species (ROS) detection

H 2 O 2 production and location were detected in the entire infection cycle using the H 2 DCF-DA staining method (Kaur et al. 2016 ; Zhao et al. 2020 . Transection samples were incubated in 10 µM H 2 DCF-DA (catalog No.4,610,273, Sigma-Aldrich) for 10 min at room temperature, then they were washed three times with 100 mM PBS (pH 7.4) to remove excess H 2 DCF-DA. Fluorescence was detected with a confocal laser scanning microscope (Leica, Germany) using the following settings: 70% power, excitation at 488 nm, and emission at 505 to 530 nm. This experiment was independently repeated at least three times.

Statistical analysis

The disease indexes and ratio of lesion area were quantified by lesion or hyphae growth area to the total area, and H 2 DCF-DA fluorescence intensities were quantified using Image J. Results represent the means of three replicate stems, and the data are presented as means ± standard deviation (SD). Different letters indicate significant differences between the samples at P  < 0.01. Significant differences between groups were determined using independent-samples Student’s t -test and one-way ANOVA with GraphPad software (version 8.0.2).

Availability of data and materials

Data will be made available on request.

Abbreviations

Three dimension

Confocal laser scanning microscope

Days post inoculation

Fusarium head blight

Hydrogen peroxide

Hours post inoculation

Hypersensitive responses

Internal transcribed spacer

Phosphate-buffered saline

Propidium iodide

Reactive oxygen species

Standard deviation

Scanning election microscopy

Transmission election microscope

Vinyl cotton

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Acknowledgements

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This work was supported by grants from the National Natural Science Foundation of China (31970240 and 32170336), the National Science Foundation of Henan Province (222300420053), and the Program for Science & Technology Innovation Talents in the Universities of Henan Province (23HASTIT035).

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College of Life Sciences, Henan Normal University, Xinxiang, 453007, China

Liping Sun, Yange Li, Xiaoting Li, Xinyi Ruan, Yueyan Zhao, Ruidong Wen, Shuaijie Wei, Ning Chen, Yulan Zhang, Shufen Li & Wujun Gao

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LS performed the investigation, writing-original draft, writing-review, and editing. YL, XL, XR, YZ, RW, SW, NC, and YZ performed investigation and formal analysis. SL conducted conceptualization, writing, review, and editing. WG performed conceptualization, writing, review, and editing.

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Correspondence to Shufen Li or Wujun Gao .

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Supplementary Information

Additional file 1: Video S1. P. asparagi pycnidium forming beneath the epidermis.

Additional file 2: Video S2. The proliferation of P. asparagi hyphae in the tissue.

Additional file 3: Video S3. P. asparagi invasive hyphae cell-to-cell movement.

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Sun, L., Li, Y., Li, X. et al. Cytological and ultrastructural investigation of pathogen infection pathway and host responses in asparagus stem infected by Phomopsis asparagi . Phytopathol Res 6 , 32 (2024). https://doi.org/10.1186/s42483-024-00252-x

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Received : 15 January 2024

Accepted : 06 May 2024

Published : 04 July 2024

DOI : https://doi.org/10.1186/s42483-024-00252-x

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• Asparagus stem blight
• Host response
• Infectious process
• Phomopsis asparagi

Phytopathology Research

ISSN: 2524-4167

ORIGINAL RESEARCH article

Occurrence and diversity pattern of crispr-cas systems in acetobacter genus provides insights on adaptive defence mechanisms against to invasive dnas.

• 1 Azarbaijan Shahid Madani University, Tabriz, Iran
• 2 Department of Genomics, Branch for Northwest & West region, Agricultural Biotechnology Research Institute of Iran (ABRII), Agricultural Research, Education and Extension Organization (AREEO), Tabriz, Iran, Agricultural Biotechnology Research Institute of Iran, Karaj, Alborz, Iran

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The Acetobacter genus is primarily known for its significance in acetic acid production and its application in various industrial processes. This study aimed to shed light on the prevalence, diversity, and functional implications of CRISPR-Cas systems in the Acetobacter genus using a genome mining approach. The investigation analyzed the CRISPR-Cas architectures and components of 34 Acetobacter species, as well as the evolutionary strategies employed by these bacteria in response to phage invasion and foreign DNA. Furthermore, phylogenetic analysis based on CAS1 protein sequences was performed to gain insights into the evolutionary relationships among Acetobacter strains, with an emphasis on the potential of this protein for genotyping purposes. The results showed that 15 species had orphan, while20 species had complete CRISPR-Cas systems, resulting in an occurrence rate of 38% for complete systems in Acetobacter strains. The predicted complete CRISPR-Cas systems were categorized into I-C, I-F, I-E, and II-C subtypes, with subtype I-E being the most prevalent in Acetobacter. Additionally, spacer homology analysis revealed against such the dynamic interaction between Acetobacter strains and foreign invasive DNAs, emphasizing the pivotal role of CRISPR-Cas systems in defending against such invasions. Furthermore, the investigation of the secondary structures of CRISPR arrays revealed the conserved patterns within subtypes despite variations in repeat sequences. The exploration of protospacer adjacent motifs (PAMs) identified distinct recognition motifs in the flanking regions of protospacers. In conclusion, this research not only contributes to the growing body of knowledge on CRISPR-Cas systems but also establishes a foundation for future studies on the adaptive defense mechanisms of Acetobacter. The findings provide valuable insights into the intricate interplay between bacteria and phages, with implications for industrial applications and potential biotechnological advancements.

Keywords: Acetobacter, CRISPR-Cas system, diversity, evolution, adaptive defence mechanisms

Received: 17 Dec 2023; Accepted: 02 Jul 2024.

Copyright: © 2024 Ghaffarian and Panahi. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Sara Ghaffarian, Azarbaijan Shahid Madani University, Tabriz, Iran Bahman Panahi, Department of Genomics, Branch for Northwest & West region, Agricultural Biotechnology Research Institute of Iran (ABRII), Agricultural Research, Education and Extension Organization (AREEO), Tabriz, Iran, Agricultural Biotechnology Research Institute of Iran, Karaj, Alborz, Iran

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