Genome-Wide Identification and Analysis of HAK/KUP/KT Potassium Transporters Gene Family in Wheat (Triticum aestivum L.)

In plants, the HAK (high-affinity K(+))/KUP (K(+) uptake)/KT (K(+) transporter) family represents a large group of potassium transporters that play important roles in plant growth and environmental adaptation. Although HAK/KUP/KT genes have been extensively investigated in many plant species, they remain uncharacterized in wheat, especially those involved in the response to environmental stresses. In this study, 56 wheat HAK/KUP/KT (hereafter called TaHAKs) genes were identified by a genome-wide search using recently released wheat genomic data. Phylogenetic analysis grouped these genes into four clusters (Ι, II, III, IV), containing 22, 19, 7 and 8 genes, respectively. Chromosomal distribution, gene structure, and conserved motif analyses of the 56 TaHAK genes were subsequently performed. In silico RNA-seq data analysis revealed that TaHAKs from clusters II and III are constitutively expressed in various wheat tissues, while most genes from clusters I and IV have very low expression levels in the examined tissues at different developmental stages. qRT-PCR analysis showed that expression levels of TaHAK genes in wheat seedlings were significantly up- or downregulated when seedlings were exposed to K(+) deficiency, high salinity, or dehydration. Furthermore, we functionally characterized TaHAK1b-2BL and showed that it facilitates K(+) transport in yeast. Collectively, these results provide valuable information for further functional studies of TaHAKs, and contribute to a better understanding of the molecular basis of wheat development and stress tolerance.