Genome-wide identification, phylogeny and expression analyses of group III WRKY genes in cotton (Gossypium hirsutum)

Cotton (Gossypium hirsutum) is an important economic crop, so it is of great significance to analyze its molecular mechanisms of resistance to Verticillium Wilt. The WRKY gene family encodes transcription factors (TFs) involved in plant resistance to biotic and abiotic stress. Here, we identified 17 group III WRKY genes in cotton based on the cotton genome project. The phylogenetic relationship and evolutionary of WRKY Group III TFs in Arabidopsis thaliana and G. hirsutum showed that all the WRKY Group III TFs were divided into two clades. Overall, Group III WRKYs with similar motif patterns showed a tendency to cluster into the same group in the phylogenetic tree. Elements related to jasmonic acid (JA) and salicylic acid (SA) regulation were identified in the promoter region of most WRKY Group III genes. The expression levels of five Group III genes were up-regulated more than two-fold and three genes were down-regulated after Verticillium dahliae Kleb. infection. Moreover, three group III GhWRKY genes with JA or SA regulatory element in the promoter region could be significantly induced by JA or SA, respectively. Subcellular localization and transcriptional activation analysis in yeast showed that Cot_14615 protein localized to the nucleus of mesophyll cells in Nicotiana tabacum and had transcription activation function. Our data on cotton group III WRKY genes can serve as a basis for further studies into their potential function in cotton resistant to Verticillium Wilt.