AUTHOR=Chan Ching , Zimmerli Laurent 

TITLE=The Histone Demethylase IBM1 Positively Regulates Arabidopsis Immunity by Control of Defense Gene Expression

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.01587

DOI=10.3389/fpls.2019.01587

ISSN=1664-462X

ABSTRACT=<p>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 <italic>MET1</italic>, for CG methylation; <italic>CMT3</italic>, <italic>DRM2</italic>, <italic>DRM3</italic> for CHH methylation; and <italic>IBM1</italic>, <italic>SUVH4</italic> for CHG methylation; the molecular roles of these regulators in specific physiological functions remain obscure. In a mutant screen, we identified <italic>IBM1</italic> as a new player in plant immunity. The <italic>ibm1</italic> mutants were hyper-susceptible to hemi-biotrophic bacteria <italic>Pseudomonas syringae</italic>. Accordingly, bacteria-induced up-regulation of <italic>PR1</italic>, <italic>PR2</italic>, and <italic>FRK1</italic> defense markers was abolished in <italic>ibm1</italic> 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 <italic>ibm1</italic> mutants. Immunoprecipitation of associated chromatin further demonstrated that IBM1 binds directly to the gene body of <italic>PR1</italic>, <italic>PR2</italic>, and <italic>FRK1</italic>. Taken together, these data suggest that IBM1 plays a critical role in modulating <italic>Arabidopsis</italic> 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.</p>