Genome-wide identification of BvHAK gene family in sugar beet (Beta vulgaris) and their expression analysis under salt treatments

Abstract

High-affinity K+ transporter (HAK) is one of the most important K+ transporter families in plants and plays an important role in plant K+ uptake and transport. To explore the biological functions and gene expression patterns of the HAK gene family members in sugar beet (Beta vulgaris), physicochemical properties, the gene structure, chromosomal location, phylogenetic evolution, conserved motifs, three-dimensional structure, interaction network, cis-acting elements of promoter of BvHAKs were predicted by bioinformatic analysis, and their expression levels in different tissues of sugar beet under salt stress were analyzed by qRT-PCR. A total of 10 BvHAK genes were identified in the sugar beet genome. They contained 8-10 exons and 7-9 introns. The average number of amino acids was 778.30, the average molecular weight was 88.31 kDa, and the isoelectric point was 5.38-9.41. The BvHAK proteins contained 11-14 transmembrane regions. BvHAK4, -5, -7 and -13 were localized on plasma membrane, while others were localized on tonoplast. Phylogenetic analysis showed that HAK in higher plants can be divided into five clusters, namely cluster Ⅰ, Ⅱ, Ⅲ, Ⅳ, and Ⅴ, among which the members of cluster Ⅱ can be divided into three subclusters, including Ⅱa, Ⅱb, and Ⅱc. The BvHAK gene family members were distributed in cluster Ⅰ-Ⅳ with 1, 6, 1, and 2 members, respectively. The promoter of BvHAK gene family mainly contained stress responsive elements, hormone responsive elements, and growth and development responsive elements. The expression pattern of the BvHAK genes were further analyzed in different tissues of sugar beet upon salt treatment, and found that 50 and 100 mmol/L NaCl significantly induced the expression of the BvHAK genes in both shoots and roots. High salt (150 mmol/L) treatment clearly down-regulated their expression levels in shoots, but not in roots. These results suggested that the BvHAK gene family plays important roles in the response of sugar beet to salt stress.