Genome-Wide Identification, Molecular Evolution, and Expression Divergence of Aluminum-Activated Malate Transporters in Apples.

Aluminum-activated malate transporters () play an important role in aluminum tolerance, stomatal opening, and fruit acidity in plants. However, the evolutionary pattern of the gene family in apples remains relatively unknown. In this study, a total of 25 genes were identified from the apple reference genome of the "Golden Delicious" doubled-haploid tree (GDDH13). The physiological and biochemical properties, gene structure, and conserved motifs of genes were examined. Chromosome location and gene-duplication analysis indicated that whole-genome duplication/segmental duplication played an important role in the expansion of the gene family. The Ka/Ks ratio of duplicated genes showed that members of this family have undergone strong purifying selection. Through exploration of the phylogenetic relationships, seven subgroups were classified, and higher old gene duplication frequency and significantly different evolutionary rates of the gene families were detected. In addition, the functional divergence of genes occurred during the evolutionary process of species. Furthermore, the functional divergence of genes was confirmed by expression discrepancy and different subcellular localizations. This study provides the foundation to better understand the molecular evolution of genes and further facilitate functional analysis to unravel their exact role in apples.