The Arabidopsis RRM domain protein EDM3 mediates race-specific disease resistance by controlling H3K9me2-dependent alternative polyadenylation of RPP7 immune receptor transcripts

The NLR‐receptor RPP7 mediates race‐specific immunity in Arabidopsis. Previous screens for enhanced downy mildew (edm) mutants identified the co‐chaperone SGT1b (EDM1) and the PHD‐finger protein EDM2 as critical regulators of RPP7. Here, we describe a third edm mutant compromised in RPP7 immunity, edm3. EDM3 encodes a nuclear‐localized protein featuring an RNA‐recognition motif. Like EDM2, EDM3 promotes histone H3 lysine 9 dimethylation (H3K9me2) at RPP7. Global profiling of H3K9me2 showed EDM3 to affect this silencing mark at a large set of loci. Importantly, both, EDM3 and EDM2 co‐associate in vivo with H3K9me2‐marked chromatin and transcripts at a critical proximal polyadenyation site of RPP7. Our results highlight the complexity of plant NLR gene regulation and establish a functional and physical link between a histone mark and NLR‐transcript processing.