H3K27me3-Mediated Epigenetic Silencing of FgHMG1 Enables Fungal Host Immune Evasion.

Histone H3 lysine 27 trimethylation (H3K27me3) is essential for fungal pathogenicity, yet its contribution to pathogen-host interactions remains incompletely understood. Here, we profiled H3K27me3 dynamics in Fusarium graminearum during infection and identified 132 H3K27me3-marked genes (FgHMGs). Among these, FgHMG1 encodes a secreted glycoside hydrolase family 11 (GH11) protein that functions as a pathogen-associated molecular pattern (PAMP), triggering PAMP-triggered immunity (PTI) in Nicotiana benthamiana through the receptor kinases BAK1 and SOBIR1, independently of its enzymatic activity. FgHMG1 also induces reactive oxygen species (ROS) accumulation and upregulation of defence-related genes in wheat plants. Remarkably, FgHMG1 expression is repressed during host invasion by the histone methyltransferase FgKMT6, a homologue of Enhancer of zeste (E(z)) from Drosophila, via H3K27me3 deposition, enabling immune evasion. Loss of FgKMT6 abolishes H3K27me3 enrichment, derepresses FgHMG1, and enhances host immunity, effects largely rescued in ΔFgKMT6-FgHMG1 double mutants. Notably, foliar application of recombinant FgHMG1 protein reduced Fusarium head blight severity in wheat by 35%-50% in 2-year field trials. These findings reveal that fungal pathogens exploit H3K27me3-mediated silencing of immunogenic PAMP genes to evade host recognition and highlight FgHMG1 as a promising candidate for crop protection.