Lipidomics-based insights into the physiological mechanism of wheat in response to heat stress.

Lipids are the main components of plant cell biofilms and play a crucial role in plant growth, Understanding the modulation in lipid profiles under heat stress can contribute to understanding the heat tolerance mechanisms in wheat leaves. In the current study, two wheat cultivars with different heat tolerance levels were treated with optimum temperature (OT) and high temperature (HT) at the flowering stage, and the antioxidant enzyme activity in the leaves and the grain yield were determined. Further, lipidomics was studied to determine the changes in lipid composition in the leaves. The heat-tolerant cultivar ZM7698 exhibited higher antioxidant enzyme activity and lower malondialdehyde and H2O2 contents. High-temperature stress led to the remodeling of lipid profile in the two cultivars. The relative proportion of digalactosyl diacylglycerol (DGDG) and phosphatidylinositol (PI) components increased in the heat-tolerant cultivar under high-temperature stress, while it was decreased in the heat-sensitive cultivar. The lipid unsaturation levels of sulfoquinovosyl diacylglycerol (SQDG), monogalactosyl monoacylglycerol (MGMG), and phosphatidic acid (PA) decreased significantly in the heat-tolerant cultivar under high-temperature stress. The increase in unsaturation of monogalactosyl diacylglycerol (MGDG) and phosphatidylethanolamine (PE) in the heat-tolerant cultivar under high-temperature stress was lower than in the heat-sensitive cultivar. In addition, a high sitosterol/stigmasterol (SiE/StE) ratio was observed in heat-tolerant cultivar under high-temperature stress. Taken together, these results revealed that a heat-tolerant cultivar could enhance its ability to resist heat stress by modulating the composition and ratio of the lipid components and decreasing lipid unsaturation levels in wheat.

Metabolite identification in fresh wheat grains of different colors and the influence of heat processing on metabolites via targeted and non-targeted metabolomics.

Phenolic antioxidants are phytochemical components in wheat grains that provide a variety of potential health benefits. The metabolites and antioxidant activity of fresh, mature, and heat-treated, wheat grains with black, blue, purple, and white grain coats were identified by targeted and non-targeted metabolomics. The total phenolic (TPC) and flavonoid contents (TFC) and antioxidant activity (AOA) increased with the darkening of grain color, the general trend being black > purple > blue > white. Purple and black wheat are rich in rutin (3916 µg/kg and 3066 µg/kg, respectively) and peonidin-3-O-glucoside chloride (2595 µg/kg and 1740 µg/kg, respectively), while blue wheat is rich in luteolin (2076 µg/kg). In most cases, TPC, TFC, and AOA had the greatest values in fresh grains and the lowest values in mature grains. Using non-targeted metabolomics, a total of 866 metabolites were identified in the tested fresh wheat grains, 106 flavonoids and 39 phenolic acids. In total, the relative abundance of flavonoids in purple and black wheat was higher than in blue wheat, indicating a higher nutritional value of fresh black and purple grains. After heat processing, the content of most metabolites decreased in heat-treated purple grain, whereas heat treatment significantly increased the content of peonidin-3-O-glucoside chloride (2.27-fold) and cynaroside (12.01-fold). This study clarifies that seed coat color and processing treatments impact the metabolite contents and antioxidant activity of wheat grains, providing valuable information for improving the nutritional quality of food during processing.