Genome-wide identification, expression pattern and genetic variation analysis of gene family in barley reveal the artificial selection of during domestication and improvement.

SWEET (Sugars Will Eventually be Exported Transporter) proteins, an essential class of sugar transporters, are involved in vital biological processes of plant growth and development. To date, systematical analysis of family in barley () has not been reported. In this study, we genome-wide identified 23 genes in barley, which were further clustered into four clades by phylogenetic tree. The members belonging to the same clade showed relatively similar gene structures and conserved protein motifs. Synteny analysis confirmed the tandem and segmental duplications among genes during evolution. Expression profile analysis demonstrated that the patterns of genes varied and the gene neofunctionalization occurred after duplications. Yeast complementary assay and subcellular localization in tobacco leaves suggested that and , highly expressed in seed aleurone and scutellum during germination, respectively, functioned as plasma membrane hexose sugar transporters. Furthermore, genetic variation detection indicated that was under artificial selection pressure during barley domestication and improvement. The obtained results facilitate our comprehensive understanding and further functional investigations of barley gene family, and also provide a potential candidate gene for domestication breeding of barley.