The Histone Demethylase IBM1 Positively Regulates Immunity by Control of Defense Gene Expression.

Epigenetic modifications involve complex and sophisticated control over chromatin states and DNA methylation patterns, which are important for stress tolerance in plants. While the identification of epigenetic modulating enzymes keeps growing, such as , for CG methylation; , , for CHH methylation; and , for CHG methylation; the molecular roles of these regulators in specific physiological functions remain obscure. In a mutant screen, we identified as a new player in plant immunity. The mutants were hyper-susceptible to hemi-biotrophic bacteria . Accordingly, bacteria-induced up-regulation of , , and defense markers was abolished in mutants. Consistently, at the chromatin level, these defense marker genes showed enrichment of the inactivation mark, H3K9me2; while the activation mark H3K4me3 was reduced in mutants. Immunoprecipitation of associated chromatin further demonstrated that IBM1 binds directly to the gene body of , , and . Taken together, these data suggest that IBM1 plays a critical role in modulating immunity through direct regulation of defense gene expression. Notably, IBM1 maintains a permissive chromatin environment to ensure proper induction of defense genes under some biotic stress.