A catalase-mediated redox-epigenetic switch governs rice immunity hijacked by a fungal effector.
Pathogen-induced reactive oxygen species (ROS) act as key signaling molecules in plant immunity, but their integration with epigenetic regulation remains unclear. Here, we identify the rice (Oryza sativa) histone deacetylase OsHDA705 as a redox sensor that coordinates immunity through oxidative post-translational modifications (PTMs). Pathogen-induced ROS oxidizes OsHDA705 at cysteine 256 (C256), blocking its deacylase activity. This oxidation promotes hyperacylation of the transcription factor OsIPA1 and histones, thereby activating defense gene expression. We further show that the catalase OsCATB functions as a redox mediator, reducing oxidized OsHDA705 to restore its deacetylase activity, thereby re-establishing the suppression of immunity. The fungal pathogen Ustilaginoidea virens hijacks this process via the secreted effector UvSE1, which physically interacts with the host catalase OsCATB to boost its ROS-scavenging activity, thereby reducing the oxidation level of OsHDA705. Genetic disruption of the OsCATB-OsHDA705 module enhances broad-spectrum disease resistance. Our findings reveal a pathogen strategy to reprogram the host's redox-epigenetic regulation and establish reversible histone deacetylase oxidation as a molecular switch regulating immune transcription in plants.