The glycoside hydrolase 7 member VdGH7a regulates Verticillium dahliae pathogenicity and induces host defenses by interacting with GhOLP1

Pathogens secrete multiple enzymes that can degrade the cell wall, thereby weakening the host's cell wall and facilitating the penetration of the pathogen into the plant. In this study, we identified VdGH7a, a glycoside hydrolase family 7 (GH7) cellobiohydrolase from Verticillium dahliae, which exhibited hydrolytic activity against 1,4-β-glucan. Interestingly, we found that VdGH7a induced cell death in Nicotiana benthamiana when signal peptides were present. However, this phenomenon was effectively prevented by the carbohydrate-binding type-1 (CBM1) protein domain. Furthermore, we observed that the knockout of VdGH7a significantly reduced the pathogenicity of V. dahliae to cotton plant, as evidenced by the inability of the knockout mutants to penetrate cellophane membrane. Additionally, these knockout mutants displayed diminished ability to exploit carbon sources, rendering them more susceptible to osmotic and cell wall stresses. Moreover, VdGH7a interacted with an osmotin-like protein (GhOLP1) in cotton through yeast two-hybrid screening, and further confirmed using bi-molecular fluorescence complementation (BiFC) and luciferase complementation imaging (LCI). Furthermore, virus-induced gene silencing technology was employed to silence GhOLP1, causing cotton's salicylic acid (SA) content and resistance to V. dahliae were both reduced, whereas heterologous overexpression of GhOLP1 in Arabidopsis increased both resistance and the expression of genes involved in the SA signaling pathway. Collectively, these findings demonstrate a virulence strategy whereby the secreted protein VdGH7a from V. dahliae interacts with GhOLP1 to stimulate host immunity and play a significant role in plant resistance against V. dahliae.