MdKCS2 increased plant drought resistance by regulating wax biosynthesis.

KEY MESSAGE: We found that the apple wax related gene played a role in changing plant epidermal permeability and enhancing plant resistance to drought stress by increasing wax accumulation. The content and composition of epidermal wax in plants are affected by genetic and environmental factors. The KCS gene encodes the β-ketoalionyl-CoA synthetase, which is a rate-limiting enzyme in the synthesis of very-long-chain fatty acids (VLCFAs). In this study, we identified the MdKCS2 gene from apple as a homolog of Arabidopsis AtKCS2. The KCS protein is localized on the endoplasmic reticulum membrane. MdKCS2 exhibited the highest expression in apple pericarp, and was induced by abiotic stresses, such as drought and salt. Transgenic analysis indicated that the MdKCS2 improved the resistance to abiotic stress in apple calli. Ectopic expression of MdKCS2 in Arabidopsis increased the content of wax in leaves and stems, changed the permeability of cuticle of leaves, and enhanced plant drought resistance.