Insights into membrane lipids modification in barley leaves as an adaptation mechanism to cold stress

Abstract

The membranes of plants are where temperature sensing begins and where freezing injury typically occurs. Barley’s adaptation to and survival after freezing stress is aided by remodelling of its membrane lipid composition. The modifications of individual lipid molecular species in different stress-treated plant species and cultivars can indicate the functions of genes regulating lipid metabolism or signaling. In this study, we employed a membrane lipidomic approach to investigate the response of barley of two cold-tolerant and two cold-sensitive cultivars to freezing temperatures during the barley trefoil stage. A total of 56 predominant lipid compounds changed significantly under freezing stress were identified. Phosphatidic acid (PA), lysophosphatidic acid (LPA) and monogalactosyldiacylglycerol (MGDG) in freezing-tolerant varieties were significantly upregulated under freezing stress, while there was a decrease in freezing-sensitive cultivars. Freezing-tolerant varieties experienced greater changes in lipid composition compared to freezing-sensitive cultivars, which had proportionally smaller changes. In addition, when exposed to short-term cold stress, varieties A and B had lower levels of monoglyceride lipase (MGLL) than varieties C and D. However, under long-term cold stress, the opposite was observed. Additionally, the freezing-tolerant variety A showed a notable increase in the expression of diacylglycerol acyltransferase 1 (DGAT1) after being exposed to 4 °C. Furthermore, SENSITIVE TO FREEZING 2 (SFR2) reached its highest level in all four varieties after being exposed to cold treatment for 48 h. This study indicates that freezing injury in barley leaves is correlated with extensive changes in lipid metabolism and that freezing-tolerant varieties can alleviate freezing injury by membrane lipid remodelling. The study’s outcomes may improve our understanding of barley’s freezing adaptation mechanisms and contribute to breeding for better tolerance.