Comparative Lipidomic Analysis Reveals Heat Stress Responses of Two Soybean Genotypes Differing in Temperature Sensitivity

Heat-induced changes in lipidome and their influence on stress adaptation are not well-defined in plants. We investigated if lipid metabolic changes contribute to differences in heat stress responses in a heat-tolerant soybean genotype DS25-1 and a heat-susceptible soybean genotype DT97-4290. Both genotypes were grown at optimal temperatures (OT; 30/20 degrees C) for 15 days. Subsequently, half of the plants were exposed to heat stress (38/28 degrees 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 the Fatty Acid Desaturase (FAD) 2-1A, FAD2-2B, FAD2-2C, FAD3A genes. 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 DS25-10s maintenance of membrane functionality and heat tolerance.