OsHDA706 mediates the deacetylation of H4K5/K8 of OsPP2C49 in response to salt stress in rice

Salt stress is one of the most adverse environmental factors that threaten plant growth and development. Increasing evidence indicates that histone acetylation is involved in the response to various abiotic stresses. However, the underlying epigenetic regulatory mechanisms in plants remain poorly understood. In this study, we revealed that the histone deacetylase, OsHDA706, epigenetically regulates the expression of salt-stress responsive genes in rice. OsHDA706 is a nuclear and cytoplasmic protein and OsHDA706 expression is significantly induced under salt stress. Moreover, oshda706 mutant showed a higher sensitivity to salt stress than its wild-type. In vivo and in vitro enzymatic activity assays demonstrated that OsHDA706 specifically regulated the deacetylation of H4K5 and H4K8. By combining chromatin immunoprecipitation and RNA sequencing, we identified the clade A protein phosphatase 2C gene, OsPP2C49, which was involved in salt response as a direct target of H4K5 and H4K8 acetylation. We found that the expression of OsPP2C49 was induced in the oshda706 mutant under salt stress. Furthermore, knockout of OsPP2C49 enhanced the plant tolerance to salt stress, but its overexpression had the opposite effect. Taken together, our results indicate that OsHDA706, a histone H4 deacetylase, responds to salt stress by regulating the expression of OsPP2C49 via H4K5 and H4K8 acetylation.