Genome-wide identification and expression analysis of the WRKY genes in sugar beet ( Beta vulgaris L.) under alkaline stress

The WRKY transcription factor family plays crucial roles in many aspects of physiological processes and adaption to environment. Although the genes have been widely identified in various plant species, the structure and function of the family in sugar beet ( L.) remains unknown. In the present study, the genes were identified from the sugar beet genome by bioinformatics. A phylogenetic tree was constructed by MEGA7.0. A distribution map of these genes was displayed by MapInspect 1.0. Furthermore, the exon-intron structure and the conserved motifs were predicted by GSDS 2.0 and MEME 5.0.5, respectively. Additionally, the expression levels of nine selected genes in shoots and roots of sugar beet seedlings exposed to alkaline stress were assayed by qRT-PCR. A total of 58 putative genes are identified in the sugar beet genome. The coding sequences of these genes ranged from 558 to 2,307 bp and molecular weights (MWs) varied from 21.3 to 84. The genes are clustered into three major groups I, II, and III, with 11, 40, and seven members, based on the primary amino acid sequences. The number of introns in the genes ranged from 1 to 5, with a majority of (27/58) containing three exons. All the genes have one or two conserved WRKY domains and zinc-finger structure. Moreover, the selected genes showed a variety of expression patterns in shoots and roots of seedlings under various concentrations of NaHCO . Importantly, in shoots and in roots were remarkably up-regulated by alkaline stress. Taken together, our findings extend understandings of the genes family and provide useful information for subsequent research on their functions in sugar beet under alkaline stress.