How Plants Combat Heat Stress and Survive the Hottest Deserts (ft. Dr. Jennifer Johnson & Dr. Karine Prado)
Maria Losito: Welcome to another episode of Interview with a Biologist. I'm your host, Maria Losito, and I'm joined today by Dr. Jennifer Johnson, who is assistant professor of Plant Eco-Physiology in the Department of Ecology and Evolutionary Biology from the University of Kansas, and Doctor Karine Prado, a research specialist in plant biology at Michigan State University. How are you both today?
Jennifer Johnson: I'm delighted to be here with you today, thank you so much for the invitation, Maria.
Karine Prado: Thank you for your interest in our research, and thank you for inviting us to this podcast, it is truly appreciated.
Maria Losito: Of course, thank you very much, I appreciate you taking the time. We'll start with Dr. Johnson and then we'll move to Dr. Prado. In general, would you mind telling us about your research interests?
Jennifer Johnson: Of course, I would say I'm broadly interested in physiological processes and particularly interested in photosynthesis and respiration. I work on projects that range from exploring how these processes work down at the molecular level up to projects that focus on how to monitor their aggregate activity at the scale of the whole planet. I’m most deeply interested in questions that relate to how the Earth's climate impacts photosynthesis and terrestrial plants, and also how photosynthesis feeds back to influence the large-scale functioning of the Earth system.
Maria Losito: Well, I'm excited to dive deeper into that, thank you, and then, Dr. Prado, what do you like to research? What are your interests?
Karine Prado: I'm interested in plant biology and in plant resilience to abiotic stresses and more specifically, I studied the mechanism of damage, tolerance of damage to improve crops in response to rising temperatures.
Maria Losito: Is there a particular crop that you focus on?
Karine Prado: I work with multiple crops, and I have a side project on maize.
Maria Losito: So, Doctor Johnson, as faculty here at KU, can you tell us a little bit about the classes you teach?
Jennifer Johnson: For sure, in the fall of 2025, I teach Biology 414, which is Principles of Ecology, and this semester I'm teaching Biology 606 which is Ecological Plant Physiology.
Maria Losito: For this particular paper, you both worked together, but is there anything in particular that drives you as researchers?
Jennifer Johnson: Well, I would say that overall, my professional pathway has really been shaped by an interest in understanding how the Earth's carbon cycle and climate system work and perhaps equally driven by an interest in contributing to the things that we need to do to make sure to keep the climate's temperature at a point that's safe for society. This relates to physiology because the carbon cycle is really driven by the process of photosynthesis - taking carbon dioxide out of the Earth's atmosphere and trapping it in an organic form, and then the process of respiration, decomposing that organic carbon back into CO2 that's returned to the atmosphere.
Maria Losito: Okay and what about you, Dr. Prado?
Karine Prado: For me key motivators include the desire to contribute new knowledge to the plant biology field, and to make some beneficial impact on society. I dream to find some solutions to feed the global population, expected to reach nearly 10 billion by 2050, and this global population increase will likely require finding solutions to increase food production despite challenging climates, limiting land water scarcity and soil nutrient deprivation.
Maria Losito: That is a great thing to help fight against because we hear about food struggles and food insecurity and with that many people on the planet, I appreciate having scientists like you researching ways to try and stop it.
Before we jump into your paper, I think it would be good for our listener to have a bit of a mental image of the plant that we're going to talk about. I know I'm a bit of a visual learner, so it would help me. Would you mind telling us the common name for the plant, as well as give us a quick description of what it looks like?
Karine Prado: Tidestromia oblongifolia is known as Arizona Honeysweet and is a perennial sub-shrub native to Mohave Desert and Death Valley and this desert plant is exceptionally tolerant and thrives in temperatures above 45°C.
Maria Losito: You recently published, “Photosynthetic Acclimation is a Key Contributor to Exponential Growth of a Desert Plant in Death Valley Summer”, what can you tell us about this research?
Karine Prado: So, heat is one among many stressors that can disturb plant growth. Heat stress is often more damaging than other stresses because it directly attacks fundamental processes like photosynthesis and can cause irreversible sun damage and significant heat loss, especially when extreme temperatures are at sensitive growth stages like flowering and seed production and a lot of regions may be facing issue with rising temperature events.
Our goal is to engineer heat resilient crops to have yield and production less sensitive to rising temperature and heat waves.
Jennifer Johnson: I could add a little bit about the way that Karine and I came to connect. This unusually thermal tolerant plant that brought us together, Tidestromia oblongifolia, that became famous in plant physiology back in the 1970s. Researchers from the Carnegie Institution for Science had built what they called a mobile laboratory for studying photosynthesis of plants in natural environments and they took this system to different kinds of contrasting habitats so that they could study the performance of plants in the places where they actually lived. One of the places where they studied the photosynthetic performance of different plants was in Death Valley, California.
When they went to Death Valley, they discovered that this one particular species had a thermal optimum for photosynthesis that was higher than any other higher plant in the world and in a sense, this was exactly what they had been looking for because Death Valley has a climate that is, hotter than almost anywhere else in the world, it’s the hottest place in the Western Hemisphere. It makes sense that the evolutionary process has selected in that environment for plants that can be successful and that have combinations of traits that allow them to thrive under these extremely challenging conditions, very hot, very dry conditions. At the time that Tidestromia was discovered to have very thermo-tolerant photosynthesis, it was amazing - but it also was not clear exactly why and exactly how the plant managed to do this. In many respects, the tools to answer those questions were just not available, at the time that the researchers originally discovered this plant. Today we have many, many more powerful tools that are available to explore the mechanisms that control the performance of photosynthesis under extreme temperatures. The idea of bringing modern tools to the challenge of understanding thermo-tolerance was really the idea that brought Karine and I together to collaborate on this project.
Maria Losito: So, we have a plant that is extremely heat tolerant, lives in a very, very difficult place for many things to survive. Why is it so important that we research plants with high heat tolerance in these extreme conditions, when most of us are not living under that kind of pressure?
Karine Prado: It's a great candidate to decipher the fundamental molecular mechanisms that confer it resistance and we can think about some impacts, and it can be the transfer of this mechanism into crops to improve their resilience to increasing temperatures.
Maria Losito: Off the top of your head, do you know of any existing crops that have benefited from that kind of genetic modification?
Karine Prado: It is under progress, but so far, they have none. Except for this study, they have no crops using the test mechanisms. That is in progress and we are working on that genetic transfer. For example, one good candidate in Michigan would be sugar beet. Sugar beet is one of the top crops in Michigan, and sugar beet is very sensitive to heat, even a few degrees can be disastrous for the field and yield. In the future, if sugar beets can be trained to tolerate heat stress, we can think just to maintain the yields current here. But so far, I don't think they have any group working just to improve crops with the knowledge based on Tidestromia.
Maria Losito: There's always room for development, so fingers crossed that ends up working with sugar beets. I remember seeing a news story about how grapes originally had a very limited grow zone that ended up shifting more northwards and that they're actually growing grapes in England now because of changes in climate and in temperature. So, it would be interesting to see if the sugar beets, as they became more heat tolerant, if they had shifts in their growth zones too.
Jennifer Johnson: I think that's really right on point: as the Earth's climate continues to warm, a lot of the crops that are currently growing very happily in particular places are likely to be challenged by the warming temperatures.
If you look across all higher plants at the fundamental response of photosynthesis to temperature, you always see, more or less the same general pattern: at very cold temperatures, photosynthesis goes very slowly, and as the temperature begins to warm, photosynthesis starts to go faster and faster and faster. It then will reach maximum speed at some kind of intermediate temperature, which differs depending on the species you're talking about. But from that peak temperature where photosynthesis is optimized, as the temperatures keep going up, photosynthesis starts to decline. And the temperature where that decline starts is variable, but it’s a universal decline that's observed in all higher plants.
The basic concern when we look at the planet's future with a warming climate and an increasing human population is that we run the risk of essentially driving our current crops outside of the temperature range where they can really be maximally productive. So, looking for a deeper understanding of the ways that evolution has solved the high temperature problem in other species and exploring strategies for bringing those evolutionary innovations into the crops that people rely on is a really timely problem. It's relevant to almost every crop that we think about in terms of food or fuel or fiber production.
Maria Losito: Yeah, I know, we're currently seeing coffee beans and chocolate, under some heat, you know, heat stress. So, I'm sure many, many people would be happy to see them better protected against these, these, these rising climate changes. Can you tell us about the methods you use to find your results?
Karine Prado: Tidestromia oblongifolia is not a model plant yet. So, we chose a holistic set of methods to decipher the mechanism underlying in persistence methods include photosynthesis measurement, microscopy, gene expression analysis, and biochemistry.
Maria Losito: When I was skimming through your paper, I saw some photos, I believe, of a lab setup that you were using. Can you tell us a little bit about what that was like?
Karine Prado: Yes, I believe you are talking about several specific growth chambers we made. It's a fantastic, new growth chamber we have at MSU. They can do, at the same time, high temperature operation (47°C) and high light (2200 umol PPFD m-2 s-1). So, it's very challenging to get this kind of chamber with both together without any failure and we are very happy just to get this fantastic chamber where we can mimic exactly what's happened during the day in July and just to get exactly what's happened, Jen modeled the climate in Death Valley, and we got this parameter in the chamber to mimic what's happened in the summer and it was pretty hot, even when you just open the door, it just, you'll feel the bright light and the temperature inside.
Maria Losito: During this study, what kind of findings did you have and what do those findings mean for further research?
Karine Prado: Among the results, we can find rapid growth. And the very condition the plant triple is biomass in just ten days and the extreme heat we have a photosynthetic optimum reaching 45°C. So, it's one of the top described so far and in response to the very conditions, the plant also exhibits similar changes such as relocation of mitochondria to coroplast, and reshaping of chloroplasts to a cup-shaped structure. The plant rewrites also the gene expression, including increasing expression of many photosynthesis gene within just one day, and many are involved in protecting protein, membrane and photosynthetic machinery from damage. And we also discovered that the Death Valley condition could boost the production of the RuBisCO activase. So, it's a key enzyme in the control of RuBisCO, a crucial enzyme for photosynthesis. For the impact of this research, Tidestromia shows the plant has the capacity to adapt to extreme temperatures and this survival method has a lot to teach us, but we can if we can translate this mechanism in crop possibly Tidestromia may be transformative for agriculture facing challenge to grow at present temperatures.
Jennifer Johnson: I might add just a little bit to complement what Korine has described, which is really to emphasize that the combination of different styles of measurements that have been brought together in this project is really unusual. Understanding the response of pretty much any part of biology to temperature involves interactions that start in the genome but are expressed all the way up into phenotype and performance. In the Tidestromia system, we now have characterization of genomic and transcriptomic and metabolomic and phenotypic and physiological observations that are nested and that provide a really unique opportunity to understand thermal adaptation in a holistic way that's really never been possible before. And on the one hand, it's an amazing challenge because there are so many types of measurements to integrate, but it's also a really amazing opportunity that has incredibly powerful potential for being applied to the kinds of social objectives that Karine outlined. Karine, are there any, any of the avenues for future investigation that you would want to comment on?
Karine Prado: Oh, for now we start with this first paper, it was just describing the plant and our way of focusing on specific protein and hopefully for the long term, we try just to transfer this mechanism in crop and just to prove, any protein can be used for just to increase the resilience of this crop. So yes, for now we have different projects and also in this paper we study a lot the leaf, but we have also a lot to learn from roots. So, we are also starting to study the roots now. And they are very exciting results. But also, the root can be resistant to the heat stress.
Maria Losito: That's awesome. I mean, it's so exciting when an avenue of research opens up different pathways. I'm looking forward to hearing about what you get up to in the years to come.
Thank you for joining us today, Drs. Johnson and Prado. I really appreciate you giving us the time and a deeper look into your research. And thank you for listening to Interview with a Biologist. You can check out the show notes for more information about the doctor's research, as well as a link to the research paper discussed in this episode. A full transcript will be available at biology.ku.edu