Team Shows Increase in Food Mass Through Photorespiratory Bypass in Elevated Temperatures

A team from the University of Illinois has engineered potato to be more resilient to global warming, showing 30% increases in tuber mass under heat wave conditions. This adaptation may provide greater food security for families dependent on potatoes, as these are often the same areas where the changing climate has already affected multiple crop seasons.

"We need to produce crops that can withstand more frequent and intense heat wave events if we are going to meet the population's need for food in regions most at risk from reduced yields due to global warming," said Katherine Meacham-Hensold, scientific project manager for the Realizing Increased Photosynthetic Efficiency (RIPE) at Illinois.

"The 30% increase in tuber mass observed in our field trials shows the promise of improving photosynthesis to enable climate-ready crops."

Meacham-Hensold led this work for RIPE, an international research project that aims to increase global food access to food by developing food crops that turn the sun's energy into food more efficiently.

The challenge

Photorespiration is a photosynthetic process that has been shown to reduce the yield of soybean, rice, and vegetable crops by up to 40%. Photorespiration occurs when Rubisco reacts with an oxygen molecule rather than CO₂, which occurs around 25% of the time under ideal conditions but more frequently in high temperatures.

Plants then have to use a large amount of energy to metabolize the toxic byproduct caused by photorespiration (glycolate). Energy that could have been used for greater growth.

"Photorespiration is a large energy cost for the plant," said Meacham-Hensold. "It takes away from food production as energy is diverted to metabolizing the toxin. Our goal was to reduce the amount of wasted energy by bypassing the plant's original photorespiratory pathway."

Previous RIPE team members had shown that by adding two new genes, glycolate dehydrogenase and malate synthase, to model plants' pathways, they could improve photosynthetic efficiency. The new genetics would metabolize the toxin (glycolate) in the chloroplast, the leaf compartment responsible for photosynthesis, rather than needing to move it through other regions of the cell.

The solution

These energy savings drove growth gains in the model crop, which the current team hoped would translate to increased mass in their food crop. Not only did they see a difference, the benefits, published in Global Change Biology, were tripled under heat wave conditions, which are becoming more frequent and more intense as global warming progresses.

Three weeks into the 2022 field season, while the potatoes were still in their early vegetative growth phase, a heat wave kept temperatures above 95°F (35°C) for four straight days, breaking 100°F (38°C) twice. After a couple of days of reprieve, the temperatures shot up near 100° again.

Rather than withering in the heat, the modified potatoes grew 30% more tubers than the control group potatoes, taking full advantage of their increased thermotolerance of photosynthetic efficiency.

"Another important feature of this study was the demonstration that our genetic engineering of photosynthesis that produced these yield increases had no impact on the nutritional quality of the potato," said Don Ort, Robert Emerson Professor of Plant Biology and Crop Sciences and Deputy Director of the RIPE project.