ChCcp1 and ChCyc1 function as a coordinated redox couple to regulate asexual sporulation, pathogenicity, and oxidative/osmotic stress adaptation in Cochliobolus heterostrophus

BACKGROUND: Cytochrome c peroxidase (Ccp) is a critical enzymatic component in the fungal oxidative stress response and cellular redox homeostasis. However, the biological roles and regulatory mechanism of Ccp in Cochliobolus heterostrophus-a major necrotrophic pathogen responsible for Southern corn leaf blight-remain poorly characterized. RESULTS: In this study, we identified and functionally characterized ChCCP1, the gene encoding Ccp in C. heterostrophus. Targeted gene deletion revealed that ΔChccp1 mutant exhibited significantly reduced conidiation and attenuated virulence on maize leaves, alongside heightened sensitivity to both oxidative and osmotic stress. Protein-protein interaction analyses-including yeast two-hybrid (Y2H) assay and GST pull-down assays-demonstrated a direct physical interaction between ChCcp1 and ChCyc1, a thioredoxin-like protein harboring a conserved peroxiredoxin domain. Subsequent phenotypic and molecular characterization of ΔChcyc1 mutants confirmed that ChCYC1 is similarly essential for conidiation, full virulence, and stress tolerance. Transcriptomic analysis further showed that deletion of either ChCCP1 or ChCYC1 lead to significant downregulation of multiple oxidative stress-responsive genes. Notably, both mutant strains displayed enhanced susceptibility to multiple classes of commercial fungicides. CONCLUSION: Collectively, these findings establish a functional ChCcp1-ChCyc1 protein complex that coordinately regulates developmental processes (conidiation), pathogenicity, abiotic stress adaption, and fungicide resistance in C. heterostrophus. This work advances our mechanism understanding of fungal pathogenesis and identifies a promising dual-target module for developing novel disease management strategies. © 2026 Society of Chemical Industry.