Dr. Greg Martin

Haesong Kim

Two IS-MPMI members, Dr. Greg Martin and Dr. Blake Meyers, have earned membership in the prestigious U.S. National Academy of Sciences (NAS; http://www.nasonline.org). NAS is a private, nonprofit institution that was established under a congressional charter signed by President Abraham Lincoln in 1863. Currently, it has about 2,400 active members and 500 foreign associates. NAS recognizes achievement in science by election to membership and, with the National Academy of Engineering and the National Academy of Medicine, provides science, engineering, and health policy advice to the federal government and other organizations.

Dr. Blake Meyers

Dr. Blake Meyers is a principal investigator and member at the Donald Danforth Plant Science Center and professor at the University of Missouri-Columbia. Dr. Meyers' group leads development and application of high-throughput DNA sequencing technologies to make fundamental discoveries about the biology of plants, including mechanisms of disease resistance, function and regulation of genomes, epigenetic mechanisms, and regulatory RNA. You can read the InterView with Dr. Meyers conducted by Dr. Ajayi Olaoluwa Oluwafunto in the last issue of Interactions.

Dr. Greg Martin

Dr. Greg Martin is the Boyce Schulze Downey Professor at the Boyce Thompson Institute (BTI) and a professor in the School of Integrative Plant Science (SIPS) at Cornell University. At BTI, researchers in Dr. Martin's lab study the molecular basis of bacterial pathogenesis and the plant immune system. The long-term goal of his research is to use knowledge gained about the molecular basis of plant–pathogen interactions to develop plants with enhanced natural resistance to diseases.

Haesong Kim, Pohang University of Science and Technology, conducted an interview with Dr. Martin.

Q1. Much of your research focuses on Pseudomonas syringae pv. tomato and its recognition in plants. What drew your interest in the Pseudomonas–tomato interaction?

Dr. Martin: I became interested in plant disease resistance while doing research for my master's degree in plant breeding. During that time, I spent a year in Malawi on a USAID-funded project to understand the biological and cultural forces that promoted the incredible genetic diversity seen in bean landraces in that country. As part of my work to study this diversity, I traveled all over the country, visited a lot of farms, and met with many subsistence farmers. That year there was a serious outbreak of halo blight disease on beans caused by Pseudomonas syringae pv. phaseolicola. The disease greatly reduced the bean harvest, and because this crop is a principal source of protein, it exacerbated the malnutrition of the farmers and their families. My interest in understanding plant–microbe interactions evolved from this experience. For my Ph.D. program, I studied the molecular basis of nitrogen fixation in Bradyrhizobium during its symbiosis with soybean. Around that time, it started to become apparent that the experimental resources and methods were becoming available to enable map-based cloning of genes in plants. When I started my postdoc position at Cornell with Steve Tanksley working on tomato, I was naturally drawn to using map-based cloning to go after a bacterial disease resistance locus. The Pto gene, which confers resistance to P. syringae pv. tomato, was known to be simply inherited and made a good target. Once Pto was identified, it opened up many questions about both bacterial pathogenesis and plant immunity, and that's kept me and my lab members busy for many years since!

Kim: It is fascinating to me how your interest in your research started, since I had little chance to travel to other countries to actually experience plant diseases and the threats caused by them. Also, you had been through different fields of plant science before your research on tomato disease resistance. It seems all those experiences contributed to your work in the end. I hope your story motivates people to engage in different work and extend their research field.

Q2. Many young scientists have role models who encourage them to pursue their careers. Did you also have a role model when you were a young scientist? Or, are there any colleagues who inspired you on your current projects?

Dr. Martin: I've been inspired by many people in my life, some of them historical. I grew up within walking distance of Michigan State University, and my brothers and I spent a lot of time in the gardens and woodlots on that campus. An early inspiration for me was Liberty Hyde Bailey, who was an MSU botanist in the early 1900s. For a time, I attended Liberty Hyde Bailey School in East Lansing and grew up hearing stories about his love of plants and his role in establishing and preserving natural areas, including the Cornell Botanic Gardens, which is just a short walk from my office now. I also read about and admired William Beal, another MSU professor, a pioneer in the development of hybrid corn, and the founder of the MSU botanic gardens. Learning about these plant biologists and spending time in the natural areas on the MSU campus sparked my interest in plants. In the early years of my career, I was inspired by many scientists, including Fred Ausubel, Noel Keen, Chris Lamb, Luis Sequeira, Steve Tanksley, Mike Thomashow, and Bud Ryan, all of whom welcomed me into the field and gave me opportunities, advice, and encouragement at key points. I've benefited greatly from and been inspired by my colleagues in the tomato genomics field, including Zhangjun Fei, Jim Giovannoni, Lukas Mueller, Susan Strickler, Joyce Van Eck, and Dani Zamir. By far my greatest inspiration over the past 20 years has been my colleague Alan Collmer here at Cornell. Our first project together involved the sequencing of the P. syringae pv. tomato DC3000 genome and its initial characterization, and then over the years, we collaborated on a series of fun projects focused on the Pseudomonas–tomato interaction. Alan's encyclopedic knowledge of plant-pathogen biology and insights about the field prompted me to extend some of my research to more bacterial-oriented questions. Most recently, I've been inspired by the great work of Jianmin Zhou (who happened to be my first postdoc) and Jijie Chai, whom I was fortunate to collaborate with many years ago when he was just starting to shift his attention to plant immunity. So, yes, I have been and continue to be inspired by a lot of people, and that has both motivated me and I hope made me a better scientist.

Kim: It would be extremely inspiring for you to have such a large number of people as your colleagues and collaborators! It also seems your interaction with those people led to fruitful results. I believe enabling the interactions between people would be one of the reasons why we keep a community like IS-MPMI after all. Community members are often eager to collaborate with people from distinct groups. In this sense, who or which group of scientists do you want to collaborate with in the future?

Dr. Martin: Looking forward, my lab will continue to strengthen our interactions with bioinformaticists since their knowledge and expertise are critical for our plans to use genome-enabled methods to identify novel genes underlying natural variations in plant immunity.

Q3. You have mentored numerous students and postdoctoral researchers during your career. What is your advice to early-career researchers for having successful interactions with their PI?

Dr. Martin: Well, it's very important for there to be clear and agreed upon expectations on the part of both the principal investigator (PI) and the student or postdoc. In my case, over the years I've developed a one-page summary of my general expectations for postdocs and graduate students (which differ slightly). For both, this includes things like keeping up with the literature and acting in a collegial and supportive way with other lab members. For graduate students, I expect them to know and follow the guidelines of their graduate program, have regular meetings with their Ph.D. committee, and strike a good balance of coursework and research. For postdocs, I expect them to start developing a professional network, write the complete first draft of their papers, and attend and participate in at least one meeting per year. A recent trend that I think is great for postdocs, in particular, is to prepare an independent development plan (IDP). This gives them the opportunity to think about a comprehensive framework for what their career goals are and what specifically they want to accomplish in their postdoctoral training period. This document also helps the PI to understand and assist them in achieving these goals.

It's also important to recognize that everyone has their own optimal way of communicating with others. In my group, we have regular lab meetings and also "focus" meetings that involve smaller groups in the lab that are working on a related project. I have one day per week when I offer my lab members the opportunity to meet with me one-on-one for 30 minutes or so. We might use the time for an update on their research, troubleshooting experiments, discussion of a paper, or talking about their professional development. These one-on-one meetings allow both me and my lab members to get to know each other better and to be proactive in addressing any opportunities or problems.

Kim: It is inspiring for me that you try to have clear documentation of expectations and plans, which I believe greatly help both you and your students. It is also inspiring that you respect different ways of communication and afford some time to have "focus" meetings, since I often find it hard to take the time to interact with other people. I believe all the ideas you shared here would be of considerable help to students, postdocs, and PIs.

Q4. Your long history of contributions to plant science research was recently recognized by the National Academy of Sciences. Among your achievements, which would benefit society most?

Dr. Martin: Most of my research has been focused on fundamental questions related to how bacteria infect plants and how the plant immune system inhibits bacterial infection. This kind of work can be viewed as laying the foundation for future applications, many of which we probably can't anticipate now. I suppose my early work on map-based cloning contributed in various ways to the subsequent cloning of many resistance (R) genes and to the use of marker-assisted breeding to track R genes more easily in segregating populations. Currently, we're most excited about the possibility of using certain R genes to confer multiple disease resistance (Mdr). There are a few examples of this in the literature, including the Ptr1 NLR gene that we originally identified as conferring resistance to race 1 strains of P. syringae pv. tomato. The Ptr1 protein detects the activity of the effector AvrRpt2, which occurs in all sequenced race 1 P. syringae pv. tomato strains, so it could be useful, along with Pto, in controlling bacterial speck disease. Homologs of AvrRpt2 occur in other plant pathogens, including Ralstonia solanacearum, and we showed that, in fact, Ptr1 also confers resistance to this pathogen, which causes bacterial wilt, an important disease of tomato. Remarkably, Prof. Kee Hoon Sohn's lab at POSTEC, South Korea, recently discovered that Ptr1 also mediates recognition of a diverse array of other effectors, including AvrB, AvrBsT, AvrRpm1, and HopZ5. In collaboration with Dr. Alex Schultink at Fortiphyte, CA, it was found that Ptr1 also confers resistance to Xanthomonasperforans expressing AvrBsT, which causes bacterial spot disease. So, Ptr1 is an example of what we call an Mdr-NLR that could be broadly useful for controlling bacterial diseases of tomato. Ptr1 was cloned from Solanum lycopersicoides, a distant relative of tomato. In all tomato accessions we have looked at, Ptr1 is a pseudogene. This opens up the possibility of developing transgenic tomatoes expressing Ptr1 or of using CRISPR prime editing to "repair" the pseudogene. It's this sort of translational work that will probably most directly benefit society, since it could lead to decreased use of chemical controls and better management of plant diseases.

Kim: It is sometimes easy to forget how fundamental science contributes to our society. Without addressing questions like you pointed out, it would be impossible to come up with enhanced control of plant diseases. Also, the Ptr1 project is truly inspiring! It is always fun to work with genes harboring great potential for practical use. I hope Ptr1-based crop protection proves to be useful for our society. I also look forward to seeing follow-up studies on Ptr1.

Q5. From the first identification of NLR genes to the solution of the resistosome structure, there have been large improvements in the field of plant immunity. Which directions do you think this field will expand into in the future?

Dr. Martin: This could be the subject of a lengthy review, and in fact, there are several out there on this important topic; it's also addressed by the initiative to come up with and address the top 10 unanswered questions in MPMI. For me, one of the most exciting areas is the increasing use of structural biology approaches to understand how plants recognize pathogens and how that initial event is transmitted to activate the immune system. The discovery of the resistosome structure is a major step forward in this regard and will hopefully lead to new insights into how NLR proteins play a role in the proximal subsequent steps to activate immune signaling. Related to this question is the need to understand how the different aspects of the host immune system inhibit pathogen growth and disease formation. In my own lab, our future focus will be on the use of natural variation in cultivated and wild relatives of tomato and genome-enabled technologies to identify new components of the immune system. We are also interested in using genome editing to generate new variation to assist in the development of disease-resistant tomato varieties.

Kim: As a Ph.D. student, it is always encouraging to be reminded that there are still unanswered questions and that there are labs, including yours, eagerly aiming to answer those questions. I hope our field continues to grow and present more questions for new researchers.

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