BcHK71 and BcHK67, Two-Component Histidine Kinases, Regulate Conidial Morphogenesis, Glycerol Synthesis, and Virulence in Botrytis cinerea.

Fungal two-component signaling systems comprise histidine kinases (HKs), phosphotransfer intermediates, and response regulators. HKs are classified into eleven groups based on domain architecture; however, Group XI members in Botrytis cinerea remain uncharacterized. In this study, we investigated the functions of two Group XI histidine kinase genes, BcHK71 and BcHK67, in B. cinerea via gene replacement. Phenotypic analysis revealed that BcHK71 and BcHK67 regulate conidiation, infection structures formation, and glycerol synthesis. Notably, BcHK71 maintained cell wall integrity. Both genes also modulated expression of high osmolarity glycerol mitogen-activated protein kinase (HOG-MARK) signaling pathway components (BcYpd1, BcSkn7, BcBos4), while BcHK67 uniquely upregulated BcBrrg1 and enhanced BcHog1 phosphorylation. Transcriptomics analysis further indicated that BcHK71 and BcHK67 participated in pathways related to carbohydrate and lipid transport, metabolism and secondary metabolite biosynthesis. Disruption of these processes reduced pathogenicity and altered fungicide sensitivity in B. cinerea, with the ΔBcHK71 mutant exhibiting more severe pronounced defects. Collectively, our findings underscore the critical roles of BcHK71 and BcHK67 in fungal development and pathogenicity, highlighting their potential as novel targets for controlling fungal diseases and managing fungicide resistance.