Improving Photosynthesis with Amanda Cavanagh

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Episode Transcription:

[ Music ]

Drew Lyon: This episode of the WSU Wheat Beat podcast was recorded on March 22, 2019, during the WSU Plant Science Symposium. The theme of the symposium was foundations for the future, embracing new agricultural technologies. As part of the program, five innovative researchers from across the U.S. and the world agreed to speak about their research. All five researchers also agreed to sit down with me for a few minutes to explain their work, and how it may relate to wheat growers in Eastern Washington.

[ Music ]

Drew Lyon: Welcome back to our special series from the 2019 WSU Plant Science Symposium. My guest today is Amanda Cavanagh. Amanda is a postdoctoral researcher for the RIPE project at the University of Illinois. She earned her Bachelor’s degree in Biology and Chemistry and went on to earn her Doctorate in Biology from the University of New Brunswick. Her research is centered around photosynthesis, the process crop plants use to fix carbon dioxide powered by the energy from the sun. Her goal is to understand and improve plant growth and photosynthetic performance in changing environmental conditions. Hello, Amanda.

Amanda Cavanagh: Hi.

Drew Lyon: So, first off, what is RIPE?

Amanda Cavanagh: RIPE is the name of the project that I’m working on. It stands for Realizing Increased Photosynthetic Efficiency. So it’s a large international project funded in large part by the Bill and Linda Gates Foundation and now with important public money in the US from the Foundation for Food and Agricultural Research as well as UK taxpayers from the Department for International Development.

Drew Lyon: Okay. So it truly is a global effort. [Amanda chuckles] So we all learn about photosynthesis at some time in our education. What’s wrong with photosynthesis that you feel you need to fix it?

Amanda Cavanagh: Right. It’s hard to argue that photosynthesis is doing anything wrong. It’s one of the most important biological reactions on the planet, and it powers all of life on Earth. But what’s good for a plant in the forest is maybe not the same thing that’s great for wheat in the field. And they’re facing very different conditions to the conditions that they evolved to do, and we’ve domesticated many traits into them. But along the way we haven’t really been manipulating or looking at photosynthesis the way that the plants actually get the energy to grow. And it turns out that it’s a little bit inefficient. So of the hundred percent of total radiation energy that a plant gets from the sun or that’s incoming from the sun, photosynthesis has an extremely low conversion efficiency. It fixes less than I think 4% for your best-performing plants. And so it leaves a lot of untapped improvement. And, unlike most of the other determinants of yields in a plant like soybean in the Midwest or wheat, it’s not near its theoretical maximum. So there’s room that we could potentially look at ways that photosynthesis could be more efficient and increase that to then increase yield in a crop.

Drew Lyon: Okay. And you use standard breeding methods, or do you have to use some of this newfangled stuff they have out there?

Amanda Cavanagh: Yeah. So our project right now is using genetic engineering. For example, one of the ways that we found that photosynthesis is quite inefficient comes in the way that plants actually fix carbon dioxide to a sugar during photosynthesis. So there’s one enzyme that does the job, and it was so good at doing the job that, when plants evolved, basically only a few forms of this enzyme took over the world. And as they took over the world photosynthesis was really successful in oxygenating the atmosphere. But to this enzyme carbon dioxide and oxygen look very similar. And about 20 percent of the time in our atmosphere it grabs an oxygen, and it causes what we call photorespiration. And cleaning that up for a plant requires a lot of energy. One of the things that we’ve done is to design completely synthetically a new pathway to deal with cleaning up this mistake. We’ve stuck it in one compartment of the cell where we want all the work to do, and then we try to down-regulate the native pathway. And it sounds probably more complicated than it is, but it’s definitely too complicated for us to get to with breeding. And so for this we take a genetic engineering approach where we borrow genes from other species and we put them into the target model crop that we’ve been working with.

Drew Lyon: Okay. And what’s that model crop?

Amanda Cavanagh: For us right now it’s tobacco. So we harbor no illusions that we’re going to feed the world with tobacco, but tobacco provides a really nice model crop for scientific researchers because it is a crop. It’s grown outside. It produces a closed canopy much like important food crops do, and it has a really short lifecycle. So we can manipulate it, grow it up to seed and plant that seed out and see if we were successful rapidly. And so that gives us a chance to speed things along from, you know, designing things on a computer simulator to getting them in the field and seeing how they actually respond to agricultural conditions within about five years, which was conveniently our funding cycle.

Drew Lyon: Okay.

Amanda Cavanagh: So it’s important to keep that in mind as you are trying to design food security projects that you still have to be able to get the work done in a timely manner.

Drew Lyon: Okay. So you are able to put it in tobacco, and now that you’ve proven this can work you’re going to move into other crops like — soybean.

Amanda Cavanagh: Exactly. So — yes. Like soybean. We’re in the Midwest. The funding from the Foundation for Food and Ag Research is to help us boost that into things that will make a difference to American farmers but also into potato which is a really interesting crop because it stores so much energy below ground. So now we can start to ask questions about how this new photosynthate will be stored on a plant and will it go towards something that we’re actually interested in. So that’s just the sugars. So if a plant produces more sugars, does it go to the part we wanted to eat? We’re betting that it will. But also food crops that are really important for people internationally like cassava and cowpea.

Drew Lyon: Okay. So soybean I believe is a C3 — what we call a C3 plant. Wheat is a C3 plant, and C3 plants aren’t quite as efficient as a C4 plant, something like corn. What’s another good C4 plant? Sunflower.

Amanda Cavanagh: Sorghum.

Drew Lyon: Sorghum. So do you see more promise for this technology in a C3 plant like wheat and soybean than you do in a C4 plant?

Amanda Cavanagh: Absolutely. So the specific project that I’m working on but many of our pipelines are going to be a boost to what we call C3 photosynthesis because they’re all plagued by the same problem which is that oxygen competes with carbon dioxide. And for us the only way to get around the oxygenation problem is to speed up the process that comes afterwards. We have not yet been able to find a version of an enzyme that’s more specific for oxygen. But the beauty of this is that the universality of the problem means that the solution is really applicable to many species and many growers who are going to start facing the same problem. So we have a colleague that’s done modeling on this, and I think across the US the yield penalty just due to photorespiration, just due to the oxygen problem is something like 36 percent across soybean and wheat. He modeled both. If we can reduce that by even 5 percent, it’s trillions of calories that would be available globally.

Drew Lyon: Ah! Very exciting. So how long do you expect it to take to move this technology from where you are today to actually seeing it out on the field in some of these crops?

Amanda Cavanagh: Yeah. We think there’s a bit of a two-step process. And so one of the steps is on our end in getting this moved into food crops with the transformation which is slow going but probably not the right limiting step. We currently have the technologies into potato. We’re moving it into soybean now. I think what will take longer is the regulatory process that will follow. These will be modified organisms, and they will be heavily studied by, of course, the regulating —

Drew Lyon: Agencies.

Amanda Cavanagh: The regulating agencies — thank you — to make sure that they’re safe and that they’re not only safe for human consumption but that they’re safe for the environment and that they’re sustainable.

Drew Lyon: Okay. So as I mentioned earlier we grow a lot of wheat around here. So is wheat in your plans, and how would you see that benefiting wheat perhaps? I can think of some things. I’m curious to see what you think.

Amanda Cavanagh: Yeah. Absolutely. I mean, I think wheat is such a huge commodity worldwide. The fact that this could be a potential benefit to wheat is really exciting to me. Wheat growers face a really similar problem to that of almost all growers around the world right now, and that’s how to maintain year and year yield increases in the face of a changing climate. And so for years we thought that elevated CO2 would get rid of this problem. It would help boost C3 photosynthesis no matter what. But we’re starting to realize that elevated CO2 is not going to come without increases in temperature. And as temperature increases this oxygenation problem gets worse. The enzyme can be fast or it can be specific but it cannot be both. And so as temperatures increase it gets faster, but it will fix more oxygen. And as it fixes more oxygen, a crop like wheat, especially in a maybe a water-stressed environment is going to spend a lot more of its biological energy cleaning up this mess. And so what we hope is that a pathway like this or technology like this will allow people who are going to be starting to face the consequences of climate change to have a little bit more hope.

Drew Lyon: Okay. And your group has found one way of doing this. I assume are other groups looking at other ways of doing it? And do you see much — will there be a lot of different approaches in addressing this issue?

Amanda Cavanagh: Yeah. I think there will be. And so this is one way of doing this. There’s another way that has just been reported in rice that shows us in a food crop which is really exciting to us. It gives us hope that the differences we see in our model species will be translated to actual grain yield. But we have collaborators around the world who are also working specifically on wheat with photosynthesis. So they’re part of the International Wheat Yield Project, which is a big global project, probably bigger than RIPE, based at the — based in Mexico at CIMMYT.

Drew Lyon: Okay.

Amanda Cavanagh: So I think there’s a lot of potential for wheat in the photosynthesis research world and not just in a GMO or from a GMO perspective but also by looking at, you know, cultivar differences or differences with wild relatives and seeing what we can bring in through traditional breeding projects too.

Drew Lyon: I think this is a really interesting field. I think it helps show or demonstrate why basic research is very important as well as applied research. And I think this sounds like it’s trying to bring those two things together for the benefit of all. So very interesting. Thank you for taking some time to share this with us.

Amanda Cavanagh: Thank you very much for having me.

[ Music ]

Drew Lyon: Thanks for joining us and listening to the WSU Wheat Beat podcast. If you like what you hear don’t forget to subscribe and leave a review on iTunes or your favorite podcasting app. If you have questions or topics, you’d like to hear on future episodes please email me at drew.lyon That’s ( You can find us online at and on Facebook and Twitter @WSUSmallGrains. The WSU Wheat Beat podcast is a production of CAHNRS Communications and the College of Agricultural, Human and Natural Resource Sciences at Washington State University. I’m Drew Lyon, we’ll see you next time.

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