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

International audience; Arabidopsis histone deacetylase HDA19 is required for gene expression programs of a largespectrum of plant developmental and stress-responsive pathways. How this enzyme sensescellular environment to control its activity remains unclear. In this work, we show that HDA19is post-translationally modified by S-nitrosylation at 4 Cysteine (Cys) residues. HDA19 S-nitrosylation depends on the cellular nitric oxide (NO) level which is enhanced under oxidativestress. We find that HDA19 is required for cellular redox homeostasis and plant tolerance tooxidative stress which in turn stimulates its nuclear enrichment, S-nitrosylation and epigeneticfunctions including binding to genomic targets, histone deacetylation, and gene repression. TheCys137 of the protein is involved in basal and stress-induced S-nitrosylation and is required forHDA19 functions in developmental, stress-responsive, and epigenetic controls. Together, theseresults indicate that S-nitrosylation regulates HDA19 activity and is a mechanism of redox-sensing for chromatin regulation of plant tolerance to stress.