ZmWRKY29 Transcriptionally Represses <i>ZmRBOHC</i> to Attenuate ROS Production and Facilitates <i>Gibberella</i> Stalk Rot Susceptibility in Maize

Gibberella stalk rot (GSR), caused by the fungal pathogen Fusarium graminearum, severely threatens maize production. However, the molecular mechanisms underlying maize resistance to GSR remain poorly understood. Here, we have identified ZmWRKY29 as a transcriptional repressor induced by F. graminearum infection, which negatively regulates maize resistance to GSR. Overexpression of ZmWRKY29 significantly compromised GSR resistance with a marked reduction in reactive oxygen species (ROS) production and callose deposition, while its mutation enhanced resistance and elevated ROS accumulation. RNA-seq revealed that the expression levels of two respiratory burst oxidase homologues, ZmRBOHA and ZmRBOHC, were decreased in ZmWRKY29-OE lines following F. graminearum challenge. ZmWRKY29 directly binds to the W-boxes in the promoters of ZmRBOHA and ZmRBOHC to repress their transcription. Moreover, mutation of ZmRBOHC similarly led to increased susceptibility and diminished ROS accumulation, confirming that ZmWRKY29-targeted ZmRBOHC is required for ROS production and GSR resistance. Thus, ZmWRKY29 acts as a susceptibility factor, repressing GSR resistance possibly by inhibiting ZmRBOHC-mediated ROS production. This highlights a pathogen strategy of exploiting host transcriptional machinery to suppress ROS defences and facilitate infection.