Two Subunits of the Rpd3 Histone Deacetylase Complex of Cochliobolus heterostrophus Are Essential for Nitrosative Stress Response and Virulence, and Interact With Stress-Response Regulators ChHog1 and ChCrz1.

Southern corn leaf blight (SCLB), caused by Cochliobolus heterostrophus, is a destructive disease in maize-growing areas worldwide. Reactive nitrogen species derived from nitric oxide exhibit antimicrobial activities by interacting with microbial cellular components, leading to nitrosative stress in pathogens. However, the regulatory mechanisms underlying adaptation to nitrosative stress remain largely unexplored in C. heterostrophus. In this study, two components of the Rpd3 histone deacetylase complex, ChPho23 and ChSds3, were identified as being involved in the nitrosative stress response and virulence in C. heterostrophus. ChPho23 and ChSds3 are not only required for vegetative growth and conidiation but are also essential for responding to oxidative stress. ChPho23 and ChSds3 directly interact with ChHog1, and ChHog1 in turn interacts with ChCrz1 to up-regulate the transcription of genes involved in the nitrosative stress response, which enable C. heterostrophus to cope with nitrosative stress. Furthermore, mutants of ΔChhog1 and ΔChcrz1 exhibited significantly reduced virulence on detached maize leaves and increased sensitivity to nitrosative stress. Taken together, these findings indicated that ChPho23 and ChSds3 are crucial for fungal growth, conidiation, nitrosative stress response, and virulence in C. heterostrophus. This knowledge could be applied to the design of strategies that target ChPho23 and ChSds3 for controlling SCLB.