Systematic identification and functional analysis of potato (Solanum tuberosum L.) bZIP transcription factors and overexpression of potato bZIP transcription factor StbZIP-65 enhances salt tolerance

Basic leucine zipper (bZIP) transcription factors play important roles in numerous growth and developmental processes. Potato (Solanum tuberosum L.) is a worldwide important vegetable crop; nevertheless, no systematic identification or functional analysis of the potato bZIP gene family has been reported. In this research, 65 potato bZIPs distributed on 12 potato chromosomes were identified. According to the topology of Arabidopsis and potato bZIP phylogenetic tree, the bZIPs were classified into thirteen groups, designated as A-K, M, and S, with no potato bZIPs included in groups J and M. The bZIPs from the same group shared a conserved exon-intron structure, intron phase, and motif composition. Eighteen potato bZIPs were involved in segmental duplications, and the duplicated gene pairs were under purifying selection. No tandemly duplicated potato bZIP was found. Each potato bZIP promoter contained at least one kind of stress-responsive or stress-related hormone-responsive element. RNA-seq and qRT-PCR analyses revealed different expression patterns of potato bZIPs under abiotic stresses. The overexpression of StbZIP-65 in Arabidopsis enhanced salt tolerance. The StbZIP-65 protein localized in the nucleus. β-Glucuronidase staining showed that promoter activity of StbZIP-65 was induced by exogenous methyl jasmonate. These results may aid in further functional studies of potato bZIP transcription factors.