Physiological Responses and Expression Changes of Fatty Acid Metabolism–Related Genes in Wheat (Triticum aestivum) Under Cold Stress

Cold stress changes the molecular and physiological responses in wheat genotypes according to their genetic potential and duration of stress. Cold stress (6 °C) has been applied in time series of 9 days (1, 3, 6, and 9 days) and evaluated the morpho-physiological responses and genes involved in fatty acid metabolisms such as desaturases and lipid transfer protein by real-time PCR technique in two cultivars of wheat, including MV-17 (cold-tolerant) and Kuhdasht (cold-sensitive). Results indicated that cold stress had a significant effect on morpho-physiological traits in MV-17 when compared with Kuhdasht. Moreover, cold stress for a long period of time could induce more bioactive compounds like hydrogen peroxide and malondialdehyde in MV-17 cultivar than in Kuhdasht. The contents of proline and glycine betaine as osmoregulators increased during times after cold exposure in both cultivars, but ascorbic acids as an antioxidant significantly increased in MV-17 cultivar during prolonged cold treatments. Meanwhile, fatty acid desaturase and lipid transfer genes are involved in fatty acid biosynthesis and lipid changes and differently expressed in cold stress. The fatty acid desaturase 2 ( FAD2 ) leads to lipid unsaturation and its transcript significantly increased in MV-17 cultivar, but it was non-significant in Kuhdasht cultivar. With prolonged cold exposure, fatty acid desaturase 3 ( FAD3 ) and lipid transfer protein 1 ( LTP1 ) gene expression increased and showed the similar trend in both cultivars, while stearoyl-acyl carrier protein desaturases ( SAD1 ) reached to maximum level after 6 days of cold exposure. We found that MV-17 cultivar could be resistant to cold stress during prolonged exposure to 6 °C by the increase in the contents of osmolytes, antioxidant, and fatty acid desaturases especially FAD2 in comparison with Kuhdasht cultivar.