Interactions

​ Nick Colaian​ni​

Nick Colaian​ni

I had ​the pleasure of interviewing Dr. Pamela Ronald who was recently awarded the 2020 World Agriculture Prize for her ach​ievements in agricultural research and science education. Dr. Ronald is a leader in the research field of plant responses to environmental and pathogen stresses. Additionally, she is an advocate and educator for sustainable food practices and modern crop breeding strategies. She has a fabulous TED talk and has written a book with her husband on modern crop science and organic farming practices titled Tomorrow’s Table: Organic Farming, Genetics and the Future of Food. This Q&A session was designed to learn more about her accomplishments, understand the challenges humanity faces in fo​od production, and the ways science has and continues to address these issues.

1. In your own words, can you provide a brief introduction of your research and interests?

“I have been working on the interaction between plants and microbes for many years. My interest in this research started when I was an undergraduate. My plant physiology professor at Reed College taught me about plant–microbe interactions, and it sparked my interest. Then, while doing my masters at Stanford, Dr. Brian Staskawicz came and gave a talk on his lab’s work, and it left an impression on me. After my Ph.D. work, I decided to work in Dr. Staskawicz’s lab. There I focused on plant–microbe interactions, where I have now spent a bulk of my career.”

At the helm of her own lab, Dr. Ronald and her team identified Xa21, a receptor in rice, using positional cloning. This receptor confers resistance to the devastating Xanthomonas oryzae pv. oryzae pathogen. Almost immediately after publication, “a colleague of mine that I had known for several years, Dr. Dave Mackill, came by my office and asked if I would help him isolate another gene in rice that plays a role in stress tolerance. I was immediately interested.” This gene, Sub1A, turned out to be instrumental for conferring tolerance to submergence. Its discovery led to an, “exciting international project to create flood-tolerant rice varieties for farmers in India and Bangladesh.”

2. Can you go a bit more in-depth about the creation and distribution of Sub1A rice varieties?

“Well this whole process was started by the International Rice Research Institute (IRRI). The mission of IRRI is to help abolish poverty and hunger in regions that depend on rice for most of their calories.

Rice fields in India and Bangladesh were constantly being flooded, resulting in devastating yield losses, so farmers looked to the scientists at IRRI to help. At the time, IRRI had built up a large and diverse rice seed collection, which they used to screen rice varieties for submergence tolerance.

Dave Mackill had worked in South Asia before working at UC Davis and knew how important this work was. Researchers at IRRI had identified a rice variety with tolerance to submergence. Dave then mapped the submergence tolerance (Sub1) trait as a quantitative trait locus (QTL). This was when Dave came to me and asked if we could collaborate on isolation of Sub1 using positional cloning. We were successful and named the key gene Sub1A.

Dave used marker-assisted breeding to introgress Sub1A into commonly used rice varieties. This breeding practice is not considered a genetically modified organism (GMO) and is not regulated. IRRI researchers collaborated with breeders at breeding stations in India and Bangladesh to test the performance of the Sub1 varieties.” Last year, 6 million farmers in India and Bangladesh grew Sub1 rice with an average yield advantage of 60% after flooding.” See this perspective for more information.

​ Dr. Pamela Ronald​

​​3. If you were to make the argument for GMO products to someone against it, what would you tell them?

“Well, I would first try to understand what they were afraid of. The term GMO means something different to everyone. Interestingly, GMO isn’t even used by the FDA because genetically modified organism doesn’t accurately describe any breeding process really. Often, a person who identifies as ‘anti-GMO’ is afraid of large corporations like Monsanto, or they heard that ‘GMOs’ require more chemicals, and they don’t like that. This is why it’s really important to understand the root of each person’s fears of GMOs, so you can narrow the discussion to address individual questions.

When trying to explain to a group of people why modern genetics is useful in agriculture, I think it’s important to give specific examples. That’s the one thing that just changes people’s mind. Two examples I usually give are genetically engineered papaya that are resistant to the deadly Papaya ringspot virus and Bt eggplant in Bangladesh that reduces the need to spray chemical insecticides. Both genetically engineered crop varieties have improved plant yields and the lives farmers.

Now in the world of COVID-19, more people are familiar with viruses and their infective nature. This is a good example, because some people may be interested to know that viruses also infect plants. This allows you to then engage people by using their knowledge about the vaccine for COVID-19 to explain the techniques used by plant scientists to ward off pathogens. Also, something I realized while writing my book was, why would the average American know a lot about farming? And, how much would they actually know about it? This is also a really important thing to keep in mind when talking about GMOs with people. Many people may not understand or know the farming practices used today and what challenges farmers face.”

4. In your point of view, what are some of the toughest challenges facing agriculture right now? And, how might agriculture look in 2040 to address these problems?

“I think problems associated with climate change, like increased flooding, which I’m now more aware of, droughts, and unpredictable insect infestations, like the fall armyworm sweeping through Africa, are going to be tough. There are scientists and modelers trying to predict new infestation events, but it is proving very difficult. The work we do now is similar to what breeders have been doing for 100 years or so, but we now have to work smarter and faster to keep up with all of the changes occurring around the world.

Additionally, we will have to start growing more food, while reducing emissions. This is something that wasn’t really being talked about when I first entered the field. It was more about reducing chemical inputs. So, now we have to also think about enhancing soil fertility, reducing greenhouse gas emissions, and using water more efficiently.

This is seemingly a daunting task; however, Dr. Ronald is optimistic that scientists can work toward solutions. “The field is rapidly advancing, and new technologies are now starting to be developed and tested to address these problems.”

5. In your mind, what are some of the most intriguing questions concerning pattern recognition receptors and their role in plant immunity?

“Well, I think an emerging topic that is still sort of a black box is the relationship between development and immunity. There is great work from Dr. Joanne Chory and others on the SERK receptors that are involved in both immunity and development. When this relationship was discovered years ago it was pretty surprising, and now there are many great examples of the relationship between development and immunity.

I think the other complicated aspect of this area is that immunity has been traditionally thought of as a linear concept—immunogen interacts with receptor, and this induces a linear pathway that results in a response. However, we now know that the responses to immunogens are much more complex than this. For instance, there are receptor complexes and receptors that can double dip into immunity and development. I think trying to sort out the balance and inner workings of this is really fascinating and will be studied for a long time.”

6. For pattern recognition receptors (PRRs) and resistance (R) genes, what needs to be done to increase their use and efficacy against pathogens?

“There are examples where different resistance genes have been stacked [placing multiple R genes into a plant], and this provided additive and, hopefully, more durable resistance. I think some steps to improve the process will be trying to predict how resistant and durable these added genes will be in a crop plant. This involves doing epidemiological studies where you think about the population diversity of the pathogen in the field. This allows you to predict the types of mechanisms the pathogen has to overcome and the methods being placed into plants to confer durable resistance. You really need to know the effector repertoire of a pathogen population and the interactions they have with the receptors of interest. This allows you to answer the question, ‘Are there pathogen strains in the field that can already overcome the R gene(s) or PRR(s) being added?’ There really is no shortcut to the process of engineering durable resistance.

We are still learning a lot about utilizing plant immune components to increase pathogen resistance. For example, being able to introduce many R genes at a single time in a cassette of genes would be a great step forward. Currently, it takes a long time to breed many R genes into a population. If people become more accepting of genetic engineering, this could decrease the time needed to introduce resistance genes into plants, which is exciting.

For a long time, there has been the hypothesis that PRRs that recognize conserved virulence factors or immunogens would be more durable in the field than R genes. However, I don’t think this has been very well validated or tested in the field. One reason may be because much of the research on PRRs, like FLS2, is carried out on non-crops. So there are very few studies that examine if these theories hold up in the field. Even for Xa21, where plants carrying this gene have been grown in the field for years now, there really hasn’t been any thorough epidemiological studies to determine if this resistance is indeed more durable than the resistance provided by other types of resistance genes such as NBS-LRR genes. Researchers have discovered bacterial strains that evade Xa21 in the field; however, to my knowledge it is not known if they become problematic to farmers. So, what does that mean? Does the evolution of the ability to evade Xa21-mediated immunity result in strains that are compromised in virulence somehow? You really can’t determine this unless you do large-scale field trials that look at the pathogen population over time.”