Genome-wide identification of WOX genes and their expression patterns under different hormone and abiotic stress treatments in tea plant (Camellia sinensis)

Plant-specific WUSCHEL-related homeobox (WOX) transcription factors regulate plant developmental processes, especially those involved in embryogenesis. However, studies on WOX family genes in tea plants do not exist. In this study, a total of eighteen CsWOX members were identified in the tea plant genome and divided into three clades based on the phylogenetic results; they included ancient, intermediate and modern clades, which reflected the evolutionary history of WOX families. Furthermore, ancient clade members had more gene structural variations than other clade members and had unique conserved motifs. The expression profiles of eight tissues showed that six CsWOX genes were highly expressed in at least four tissues, while other genes were expressed at a very low level or not expressed. Moreover, numerous cold-, drought-, ethylene-, methyl jasmonate (MeJA)-, abscisic acid (ABA)-, and gibberellic acid (GA)-responsive cis-elements were observed in the CsWOX promoter regions, and we subsequently investigated their expression patterns under these treatments. Notably, the ancient clade members may play more active roles than members of the other clades in environmental adaptation in tea plants. Our work provides precise information on CsWOX family genes that will benefit the further understanding of their functional roles in tea plants.