Dynamic and adaptive membrane lipid remodeling in leaves of sorghum under salt stress

Salt stress limits plant growth and development. In this study, changes in membrane lipids were investigated in leaves of sorghum seedlings subjected to salt stress (150 mmol L−1 NaCl). Galactolipids (DGDG and MGDG) accounted for more than 65% of the total glycerolipids in sorghum leaves. The predominance of C36 molecular species in MGDG suggested that sorghum is an 18:3 plant. Under NaCl treatment, the content of major phospholipids (PC and PE) increased, accompanied by the activation of their metabolism pathways at the transcriptional level. In contrast, the proportion of MGDG and PG dropped drastically, leading to a decreased ratio of plastidic to non-plastidic lipids. An adjustment of glycerolipid pathway between the cytosolic and plastidic compartments was triggered by salt stress, as reflected by the increased conversion of PC to PA, providing precursors for galactolipid synthesis. The elevated DGDG resulted in increased DGDG/MGDG and bilayer/non-bilayer lipid ratios. The double-bond index of PC, PE, and DGDG increased markedly, evidently owing to the increased expression of FAD3 and FAD8. These findings will be helpful for understanding dynamic membrane lipid changes and adaptive lipid remodeling in sorghum response to salt stress.