Histone Deacetylase OsHDA706 Increases Salt Tolerance Via H4K5/K8 Deacetylation of OsPP2C49 in Rice

High salt is a major environmental factor that threatens plant growth and development.Increasing evidence indicates that histone acetylation is involved in plant responses to various abiotic stress;however,the underlying epigenetic regulatory mechanisms remain poorly understood.In this study,we revealed that the histone deacetylase OsHDA706 epigenetically regulates the expression of salt stress response genes in rice（Oryza sativa L.）.OsHDA706 localizes to the nucleus and cytoplasm and OsHDA706 expression is significantly induced under salt stress.Moreover,oshda706 mutants showed a higher sensitivity to salt stress than the wild-type.In vivo and in vitro enzymatic activity assays demonstrated that OsHDA706 specifically regulates the deacetylation of lysines 5 and 8 on histone H4（H4K5and H4K8）.By combining chromatin immunoprecipitation and mRNA sequencing,we identified the clade A protein phosphatase 2C gene,OsPP2C49,which is involved in the salt response as a direct target of H4K5 and H4K8 acetylation.We found that the expression of OsPP2C49 is induced in the oshda706 mutant under salt stress.Furthermore,the knockout of OsPP2C49 enhances plant tolerance to salt stress,while its overexpression has the opposite effect.Taken together,our results indicate that OsHDA706,a histone H4 deacetylase,participates in the salt stress response by regulating the expression of OsPP2C49 via H4K5 and H4K8 deacetylation.