Genome-wide analysis of the light-harvesting chlorophyll a/b-binding gene family in apple (Malus domestica) and functional characterization of MdLhcb4.3, which confers tolerance to drought and osmotic stress

In higher plants, the light-harvesting chlorophyll a/b-binding (Lhc) proteins function in multiple processes that are critical to plant growth, development, and abiotic stress response. However, the Lhc gene family has not been well characterized in the important fruit crop, apple (Malus × domestica Borkh.). In this study, we identified 27 Lhc genes in the apple genome. Phylogenetic analysis showed that the Lhc gene family could be classified into three major subfamilies, each of whose members shared similar conserved motifs. Evolutionary analysis indicated that duplicated MdLhc genes were primarily under purifying selection. MdLhcs were expressed at varying levels in all tissues examined and showed different expression patterns under drought stress. The overexpression of MdLhcb4.3 in transgenic Arabidopsis and apple callus enhanced their tolerance to drought and osmotic stress. Taken together, these results demonstrate the important role of Lhc proteins in the regulation of plant resistance to drought and osmotic stress and provide valuable information for further study of Lhc functions in apple.