Genetic engineering study explored new strategies to combat heat stress in potato crops

By Dr. Chinta SidharthanReviewed by Lexie CornerDec 12 2024

Global food security remains a challenge due to climate change, particularly rising temperatures and frequent heatwaves that threaten the yields of staple crops. Potatoes, a critical non-grain food crop, are highly susceptible to heat stress.

Image Credit: nednapa/Shutterstock.com

In a recent study published in Global Change Biology, researchers investigated the potential of a genetically engineered alternative photorespiratory pathway (AP3) in potatoes to enhance photosynthetic efficiency and thermotolerance. Over multiple growing seasons, they evaluated the impacts of this modification on photosynthetic performance, carbon assimilation, and tuber yields under varying heat conditions.

Background

To support the rapidly growing global population, agriculture must adapt to meet increasing food demand while addressing the challenges posed by climate change. While advances in crop breeding have led to some yield improvements, productivity for major crops is plateauing. Heatwaves driven by climate change also exacerbate yield reductions, particularly in heat-sensitive crops such as potatoes.

Potatoes are an important part of the global caloric intake but require cooler temperatures for optimal growth. Heat stress can reduce tuber formation and overall yields. Photorespiration, a natural but inefficient process in C3 plants such as potatoes, consumes energy and carbon that could otherwise be used for growth, making it a potential target for optimization.

Introducing pathways that bypass photorespiration has shown potential for improving photosynthesis and biomass in model plants. However, the impact of such pathways on enhancing heat tolerance in crop species remains underexplored.

The current study

The present study aimed to implement the AP3 pathway in potatoes to improve photosynthetic efficiency and heat tolerance. The researchers used genetic engineering to introduce the alternative photorespiratory pathway (AP3) in Solanum tuberosum cv. Desiree.

This pathway incorporated enzymes from Chlamydomonas reinhardtii glycolate dehydrogenase and Cucurbita maxima malate synthase, along with RNA interference to suppress a native glycolate transporter in potato plants. Control plants, which underwent the same transformation process but lacked the transgenes, were also included.

Field experiments were conducted over two years at the University of Illinois Energy Farm using a randomized block design. Plants were propagated from tubers or tissue culture to ensure consistent establishment, then acclimated in growth chambers or greenhouses before field transplantation. Researchers monitored plant growth stages, heat stress events, and environmental responses.

Gene expression of the introduced constructs was verified using quantitative reverse transcription polymerase chain reaction (qRT-PCR). Photosynthetic performance was assessed through diurnal carbon dioxide (CO₂) assimilation measurements, light and CO₂ response curves, and intrinsic water-use efficiency.

Using gas chromatography-mass spectrometry, leaf tissues were analyzed for photorespiratory metabolites under heatwave simulations. Tuber yield was measured by hand-harvesting and weighing marketable tubers. Statistical analyses were conducted to compare photosynthetic traits, gene expression, and yield between transgenic and control lines.

The nutritional composition of the tubers was assessed for crude protein, dietary fiber, starch, and mineral content using standard methods. Soil composition and environmental data, including temperature fluctuations and heatwave intensity, were monitored to provide context for the growth conditions.

Major findings

The researchers found that introducing the AP3 pathway significantly improved both potato tuber yield and photosynthetic performance, especially under heat stress. In 2020, the AP3 line showed a 9.5 % increase in tuber mass compared to the controls, although there was no noticeable improvement in photosynthetic capacity. By 2022, however, the AP3-transformed plants demonstrated up to a 30 % increase in tuber mass and a 14 % higher carbon assimilation rate, particularly during heatwaves.

The enhanced photosynthetic capabilities of the AP3 plants were evident during the tuber bulking stages. These plants showed higher maximum carboxylation rates and improved electron transport rates. Notably, during heatwaves, the AP3 lines also had better diurnal CO₂ assimilation, showing they were more resilient to high temperatures.

Afternoon carbon assimilation increased by 18 % to 19 %, which was linked to lower CO₂ compensation points in the transgenic plants. Analysis of photorespiratory metabolites revealed elevated levels of glycolate, glycine, and malate in the leaves, suggesting a functional change in the pathway.

The study also found that the tuber quality remained unaffected by the AP3 modification, with no changes in starch, protein, or sugar levels. There were minor increases in dietary fiber and iron in some transgenic lines, but these differences were not consistent across growing seasons.

Environmental monitoring showed that early-season heatwaves in 2022 helped the AP3 plants display thermotolerance. Under milder conditions, the physiological benefits of AP3 were less noticeable. Overall, the AP3 pathway's ability to maintain photosynthesis and yield under heat stress suggests its potential to help mitigate the impact of climate change on crop production.

Conclusions

The study demonstrated that the AP3 pathway can significantly enhance photosynthetic performance, thermotolerance, and tuber yield in potatoes without compromising nutritional quality. By addressing the photorespiratory inefficiencies, AP3 offers a viable strategy to improve crop resilience in heat-prone regions.

Journal reference

Meacham-Hensold, K., Cavanagh, AP., Sorensen, P., South, PF., Fowler, J., Boyd, R., Jeong, J., Burgess, S., Stutz, S., Dilger, RN., Lee, M., Ferrari, N., Larkin, J., Ort, DR. (2024). Shortcutting Photorespiration Protects Potato Photosynthesis and Tuber Yield Against Heatwave Stress. Global Change Biology. DOI:10.1111/gcb.17595, https://onlinelibrary.wiley.com/doi/10.1111/gcb.17595