GhWRKY55 as a negative regulator of cotton resistance to Verticillium dahliae via lignin biosynthetic and jasmonic acid signaling pathways

Verticillium wilt, caused by Verticillium dahliae, is a major threat to cotton yield and quality. While the WRKY gene family has been shown to be involved in plant defense against V. dahliae, the underlying mechanisms remain unclear. In this study, we found that Gossypium hirsutum WRKY DNA binding protein 55 (GhWRKY55) negatively regulates cotton defense against V. dahliae. GhWRKY55 expression was suppressed in resistant cotton cultivars following V. dahliae inoculation, and the overexpression of GhWRKY55 in Arabidopsis decreased the resistance to V. dahliae. Silencing of GhWRKY55 enhanced the resistance of susceptible cotton to V. dahliae by increasing salicylic acid (SA) accumulation, decreasing jasmonic acid (JA) levels, and altering lignin content and monomer G/S ratio. Yeast one-hybrid and dual-luciferase assays revealed that GhWRKY55 protein interacts with the promoters of lignin biosynthesis-related gene GhHCT_D10 and JA signaling pathway gene GhPR3_D01–1. Our findings suggest that GhWRKY55 negatively regulates cotton resistance to V. dahliae by affecting lignin biosynthesis and JA signaling pathway. These results provide new insights into the relationship between GhWRKY55, SA/JA, and lignin in defense against V. dahliae.