GhWRKY75 positively regulates GhPR6-5b via binding to a W-box TTGAC (C/T) to orchestrate cotton resistance to Verticillium dahliae

Verticillium dahliae is an important fungal pathogen affecting cotton yield and quality. Therefore, the mining of V. dahlia-resistance genes has important implications and is urgently required. Protease and protease inhibitors play crucial roles in plant defense responses. However, little is known regarding the functions and regulatory mechanisms of the protease inhibitor PR6 gene family. This study conducted a comprehensive analysis of the PR6 gene family within the cotton genome. We performed genome-wide identification and functional characterization of the cotton GhPR6 gene family, which belongs to the potato protease inhibitor I family of inhibitors. Thirty-nine PR6s were identified in Gossypium arboreum, G. raimondii, G. barbadense, and G. hirsutum and were clustered into four groups. Based on the analysis of pathogen-induced and Ghlmm transcriptome data, the key gene for V. dahliae resistance, GhPR6-5b, was identified. Virus-induced gene silencing experiments revealed that cotton was more sensitive to V. dahliae V991 after PR6-5b silencing. The present study established that GhWRKY75 plays an important role in resistance to cotton Verticillium wilt by positively regulating GhPR6-5b expression by directly binding to W-box TTGAC(T/C). Our findings established that GhWRKY75 is a potential candidate for improving cotton resistance to V. dahliae, providing primary information for further investigations and the development of specific strategies to bolster the defense mechanisms of cotton against V. dahliae.