Biology professor Xinnian Dong has received one of the highest honors in science for her work in plant immune systems. She was elected as a member of the National Academy of Sciences in May, joining 105 new members of the Academy chosen from 15 countries. Dong will be inducted at the 150th annual meeting of the Academy in Washington, D.C. next April. The Chronicle’s Andrew Luo spoke with Dong recently about her discoveries in plant immunity and her plans for the future.
The Chronicle: What is the most memorable research project that you have worked on?
Xinnian Dong: One of the most striking experiments that I worked on was the identification of the NPR1 mutant for the nonexpressor of PR genes. When I started this lab, there were only four people in the lab that had a close understanding of this type of research. We had a mutant, and it expressed a group of genes called PR genes. This mutant had a notable phenotype. If you inoculate bacterial pathogens, the wild type—[the most common in a population]—will show a certain level of resistance. But for this NPR mutant, it was highly susceptible to infection and to many different pathogens. This was probably one of the most exciting experiments in my career. When we saw that this mutant is so susceptible to infection, we realized that we found a gene that when mutated would have very dire consequences in a host’s ability to respond to pathogens. For the twenty years I’ve been here at Duke, my lab has focused on the function of this gene.
TC: How have your past studies impacted your career in plant biology?
Xinnian Dong: I studied plasmid replication as a graduate student, using E. coli as a model. The plasmid I studied was called the R plasmid, which is used in drug and antibiotic resistance. Many of the drugs conferred by the plasmid carried a lot of drug resistance genes, and my thesis was on how the plasmid was well-replicated inside of bacteria, so this was part of my dissertation project. The research I conducted helped me later on when I worked with microbial genetics, which is fundamental to molecular biology. Through this project, I gained solid training in microbial and genetics biology. My undergraduate degree was in microbiology, and I did my dissertation work in microgenetics. Afterwards, I did my post doctoral studies at Massachusetts General Hospital in the department of molecular biology. There were three plant labs in that department, with greenhouses located on top of the hospitals. This gave me a close access to plant research.
TC: Why did you decide to switch to plant biology studies?
XD: I wanted to study organisms that were more sophisticated. During my post-doctoral training, microbial genetics was well-developed, and I wanted to get into an area that was not researched as thoroughly. In college, I was very interested with immunology, and I became fascinated with the interactions between organisms, especially pathogen and host interactions. Also, I realized that I did not like working with animals. When we did immunology labs, the animals we worked with sometimes suffered intense allergic reactions, and they suffered quite a bit. This type of work was not something I wanted to do, but I still had a strong interest in host microbial interactions and how hosts respond to pathogens. Because of this initial interest in immunology and microbiology, I decided to move to plants and see how plants respond to pathogen interaction. At that time, there was not very much known about plant immune systems, and it was an open field for research.
TC: You became a member of Duke faculty in 1992. How did being a faculty member at Duke help you in terms of the type of research you have been able to conduct?
XD: Duke is a wonderful place to do research, and I enjoy working with my colleagues in the department. It’s also very convenient that there is a medical school on campus. Most of the time, if I have a question on any area in biology, I can find experts on campus, and I don’t really need to go elsewhere to find help. Also, the Research Triangle has three well-known universities, [the University of North Carolina at Chapel Hill], [North Carolina State University] and Duke. The professors and scientists meet monthly at seminars, so it truly is a wonderful place to do research.
As for me, not only do I have many colleagues who also use plants as their experimental subjects, but there are also people working in the medical field. We can all learn from experts from a wide variety of fields. However, one of the things I like most about working at Duke is the students. I really enjoy chatting with my undergraduates in my microbiology class. They are my inspiration—they always come to class with fresh ideas and are eager to learn. It’s an academically stimulating environment. At the same time, in comparison to big cities, it is much quieter here at Duke. It really lets me concentrate on research.
TC: Your current research focused on plant immunity. What’s your next research focus?
XD: There is a unique aspect of how plants respond to pathogen infections, because plants do not have specialized immune cells like animals do. Humans have white blood cells whose main function is to fight off disease. On the other hand, plants have cells that are polipotent, meaning that the cells have multiple functions. Plants have cells that normally undergo photosynthesis, but when the plant is infected, these same cells have to defend against infection. The question is how plants balance and prioritize their cellular functions.
I think the future for this area is to study the interaction between plant cell responses to other cellular functions. Recently, my lab discovered that plant immunity response is controlled by the circadian clock. The circadian clock not only regulates time and temperature but also regulates immune response genes. For example, fungal pathogens usually come out in the morning. This is because when the sun comes out, there is rapid drying of leaf surface. This is the trigger to the dispersal of fungal spores. We found that there is a peak of expression of plant immune genes at this time, which correlates with the threat of pathogen infection. This is one of the research directions I would like to go in: to study how plant immune response is correlated to other cellular functions. In this case, we are already studying how the circadian cycle regulates plant immune response.