S‐Nitrosylation of the histone deacetylase HDA19 stimulates its activity to enhance plant stress tolerance in Arabidopsis

SUMMARY Arabidopsis histone deacetylase HDA19 is required for gene expression programs of a large spectrum of plant developmental and stress‐responsive pathways. How this enzyme senses cellular environment to control its activity remains unclear. In this work, we show that HDA19 is post‐translationally modified by S‐nitrosylation at 4 Cysteine (Cys) residues. HDA19 S‐nitrosylation depends on the cellular nitric oxide level, which is enhanced under oxidative stress. We find that HDA19 is required for cellular redox homeostasis and plant tolerance to oxidative stress, which in turn stimulates its nuclear enrichment, S‐nitrosylation and epigenetic functions including binding to genomic targets, histone deacetylation and gene repression. The Cys137 of the protein is involved in basal and stress‐induced S‐nitrosylation, and is required for HDA19 functions in developmental, stress‐responsive and epigenetic controls. Together, these results indicate that S‐nitrosylation regulates HDA19 activity and is a mechanism of redox‐sensing for chromatin regulation of plant tolerance to stress. Significance Statement The stress‐induced S‐nitrosylation regulates HDA19 activity to deacetylate H3K14 and to repress expression of subsets of genes under stress.