Phylogenetic analysis and drought-responsive expression profiles of the WRKY transcription factor family in maize

WRKY transcription factors play diverse roles in biotic and abiotic stresses. However, little comprehensive study has been presented about maize WRKY genes in drought stress response. In the present study, the phylogenetic relationships between ZmWRKYs and known WRKYs were analyzed, and it was shown that the gene structure and motif compositions were conserved within a group or a subgroup identified. And then, the expression profiling of ZmWRKY genes based on the global microarray data revealed eight genes responded to drought stress. Additionally, RNA-Seq profiling showed that 58 ZmWRKY genes were induced in drought stress. Real-time quantitative RT-PCR was used to verify the expression patterns of several candidate drought-responsive ZmWRKY genes. The cis-elements analysis of ten candidate ZmWRKY genes showed that the putative promoter of each gene includes at least a drought-responsive MBS element. Furthermore, the protein-protein interaction analyses revealed the intricate co-regulatory and co-expression network, which was consistent with the drought-responsive expression profiles of ZmWRKYs. Thus, these results provide a fundamental clue for cloning functional maize WRKY genes.