Researchers tweak potatoes to thrive in the heat

Climate change may have been a hot potato topic around the dinner table at festive celebrations this year. Now, researchers have developed their own ‘hot potato’ that fares better under climate change: in fact these tubers grow up to 30% larger than normal, during heatwave conditions. 

Key to their discovery is a process called photorespiration, a troublesome feature of plant photosynthesis. Photorespiration occurs when Rubisco, a key enzyme in photosynthesis, reacts with oxygen molecules instead of with carbon dioxide as normal. The Rubisco-O2 fusion generates a toxic byproduct called glycolate that the plant must then work hard to metabolize and clear from its tissues—an energy-intensive process that diverts resources from the carbon fixation needed to power plant growth. In fact, this problem can reduce the amount of carbon that a plant fixes by between 20 and 50%.

The CO2-O2 switcheroo happens about 25% of the time during photosynthesis, but interestingly it increases under warmer conditions because when it’s hot, Rubisco’s affinity for oxygen rises. In the researchers’ eyes, that made photorespiration a priority in the quest for more climate-resilient crops. 

Previous work from the research project that they are part of—an initiative called RIPE that investigates ways to increase the efficiency of photosynthesis for food production—found that two particular genes, glycolate dehydrogenase and malate synthase, could help curb the photorespiration glitch. A function of these two genes is to metabolize the toxic glycolate byproduct right there in the leaf’s chloroplast where photosynthesis takes place—creating a ‘shortcut’ which stops glycolate from spreading into the rest of the cell where it triggers the energy-intensive metabolizing cascade. 

The former research proved that the two genes can be engineered into model tobacco plants. But this new study is the first to experiment with the idea on an edible crop like the potato. 

Testing two types of potatoes—those bred to contain the two genes, and those without—the researchers planted specimens in open fields during two growing seasons, one in 2020, and one in 2022. Over these growing periods the researchers examined the crops’ mass, weight, and nutritional value under changing climate conditions. During at least two points in the study, those conditions included a heatwave that bore down on the young potato crop for almost a week, giving the researchers a chance to test whether these new, vulnerable plants would grow into plants that were as robust as they hoped.

The answer was yes—to a striking degree. Compared to the controls, the heat-exposed potatoes showed increased photosynthetic activity, and more carbon fixation. What’s more, that clearly translated into larger vegetables: across the study site over the two years, the gene-bred potatoes showed a 9 to 30% increase in their biomass. 

Crucially also, when the researchers examined the nutritional content of the plants, they found that this enhanced growth did not affect the tubers’ quality or nutrition. The potatoes showed no changes in total fiber, vitamin C or protein levels compared to the controls.

The findings have successfully taken the previous work into a real-world crop—and the choice of the potato was no accident. Potatoes are the most important non-grain crop in terms of production globally, and are on par with rice and maize in terms of the amount of calories they generate by area of land. The starchy tubers are an essential ingredient for global food security, and the new discovery could provide them with a crucial buffer against climate change. 

The next step is to repeat the study’s findings in multiple locations, and perhaps to test out the idea on other tuber crops like cassava that are foundational for food security in many regions.

“We need to produce crops that can withstand more frequent and intense heatwave events,” the researchers say, adding that they believe their discovery paves a path for “climate-ready crops.”

Ort et, al. “Shortcutting Photorespiration Protects PotatoPhotosynthesis and Tuber Yield Against Heatwave Stress.” Global Change Biology. 2024.

Photo by Andre Morales Kalamar on Unsplash