Galactolipid remodeling is involved in drought-induced leaf senescence in maize

Drought triggers leaf senescence, leading to a critical decrease in crop yield. The membrane lipid composition generally undergoes major changes during drought. However, little is known about the role of galactolipid remodeling in the drought-induced senescence response in crops. Here, a comparative study of alterations in galactolipid and fatty acid composition during drought and recovery was carried out using two maize cultivars differing in drought-induced leaf senescence. Under drought condition, the monogalactosyldiacylglycerol (MGDG) content was decreased by 18.3% and 25.9% in the cultivar with retarded leaf senescence and the senescent cultivar, respectively, while digalactosyldiacylglycerol (DGDG) was enhanced by 43.2% and 22.9%. Compared with the senescent cultivar, the DGDG content and the DGDG/MGDG ratio were 29.8% and 20.7% higher in the cultivar with retarded leaf senescence, which also maintained stable chloroplast ultrastructure under drought stress. The expressions of key galactolipid biosynthesis genes in both cultivars were up-regulated by the drought stress. In addition, the expression levels were higher in the cultivar with retarded leaf senescence than that in the senescent cultivar. These results suggests that a profound modification of galactolipid composition with high DGDG content and DGDG/MGDG ratio is associated with the alleviation of leaf senescence in response to drought. The regulation of galactolipid remodeling could be a promising strategy for alleviating the leaf senescence and improving drought adaptation in crops.