Suppression of ZmJAZ12 Expression Modulates Jasmonic Acid and Salicylic Acid Signalling and Enhances Maize Resistance to Southern Corn Rust.

Southern corn rust (SCR), caused by the biotrophic fungus Puccinia polysora, severely threatens maize yield worldwide. In this study, we identified ZmJAZ12, a member of the JASMONATE ZIM-domain (JAZ) protein family, as a negative regulator of SCR resistance in maize. Genome-wide association study (GWAS) and expression analyses revealed that the expression level of ZmJAZ12 was negatively correlated with SCR resistance, and the resistant haplotypes exhibited significantly lower transcript abundance of ZmJAZ12. The ZmJAZ12 overexpression (OE) lines showed enhanced susceptibility to SCR, while ZmJAZ12 knockout mutants generated via CRISPR/Cas9-mediated gene editing were more resistant to SCR. Transcriptomic profiling revealed that downregulation of key genes in the salicylic acid (SA) and jasmonic acid (JA) pathways occurred in the OE lines. ZmJAZ12 interacted with ZmMYC5, a core transcription factor in the JA signalling cascade, forming a regulatory module that regulates hormonal signalling and immune responses. Collectively, these findings reveal that ZmJAZ12 acts as a susceptibility gene, providing evidence for the JA/SA signalling crosstalk mechanism in plant immunity. This study provides a potential genetic target for enhancing disease resistance in maize breeding.