Lipid metabolic changes contribute to heat tolerance in soybean

Authors: NARAYANAN, SRUTHI - Clemson University; ZOONG LWE, ZOLIAN - Clemson University; GANDHI, NITANT - Clemson University; WELTI, RUTH - Kansas State University; FALLEN, BENJAMIN - Clemson University; Smith, James - Rusty; RUSTGI, SACHIN - Clemson University

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2020
Publication Date: 4/4/2020
Citation: Narayanan, S., Zoong Lwe, Z.S., Gandhi, N., Welti, R., Fallen, B., Smith, J.R., Rustgi, S. 2020. Lipid metabolic changes contribute to heat tolerance in soybean. Plants. 9(4):1-17. https://doi.org/10.3390/plants9040457.
DOI: https://doi.org/10.3390/plants9040457

Interpretive Summary: Soybean is one of the most important oilseed crops in the world, as well as an affordable source of protein. Yet, high temperatures (86° F and above) can limit soybean yields. Understanding the mechanisms of heat tolerance will be critical for developing climate-resilient soybean varieties in the future. The objective of this research was to investigate the role of different fats in soybean leaves as a possible mechanism for heat tolerance. Leaf tissues from DS25-1 (heat tolerant) and DT97-4290 (heat susceptible) soybean lines were sampled under heat stress conditions and tested for their levels of saturated, monounsaturated, and polyunsaturated fats. The amounts of polyunsaturated fats decreased and the amounts of saturated and monounsaturated fats increased under heat stress conditions in the heat tolerant line, but not in the heat sensitive line. This suggests that a decrease in polyunsaturated fats in DS25-1 promotes cell membrane stability and heat tolerance in DS25-1. Plant breeders may be able to use the genes that reduce polyunsaturated fats as markers to select new heat tolerant soybean varieties.

Technical Abstract: Heat-induced changes in lipidome and their influence on stress adaptation are not well-defined in plants. We investigated if lipid metabolic changes mediate heat stress responses in soybean. Heat-tolerant (DS25-1) and susceptible (DT97-4290) genotypes were grown at optimal temperatures (OT; 30/20°C) for 15 days. Subsequently, half of the plants were exposed to heat stress (38/28°C) for 11 days, and the rest were kept at OT. Leaf samples were collected for lipid and RNA extractions on the 9th and 11th days of stress, respectively. We observed a decline in the lipid unsaturation level due to a decrease in the polyunsaturated linolenic acid (18:3) content in DS25-1. When examined under OT conditions, DS25-1 and DT97-4290 showed no significant differences in the expression pattern of any of the studied fatty acid desaturase (FAD) genes. However, under heat stress conditions, substantial reductions in the expression levels of the FAD3A and FAD3B genes, which convert 18:2 lipids to 18:3, were observed in DS25-1. Our results suggest that decrease in levels of lipids containing 18:3 acyl chains under heat stress in DS25-1 is a likely consequence of reduced FAD3A and FAD3B expression, and the decrease in 18:3 contributes to DS25-1’s maintenance of membrane functionality and heat tolerance.