HDA15-Mediated Deacetylation of GPX1 Inhibits Its Nuclear Translocation and Increases Osmotic Stress Sensitivity in Rice

Redox regulation plays an important role in plant stress responses. Our previous study revealed that rice GLUTATHIONE PEROXIDASE 1 (GPX1) acts as a redox sensor and transducer and promotes osmotic stress tolerance by transfer of cytosolic oxidative signals to transcription factor BASIC LEUCINE ZIPPER 68 (bZIP68). However, the mechanisms governing GPX1 activity and nuclear localization remain unclear. Here, we show that osmotic stress increases GPX1 acetylation. Peroxidase activity and subcellular localization assay indicated that the effects of acetylation on GPX1 function are site-specific, as the acetylation of K94 and K121 enhances GPX1 enzymatic activity, whereas the C-terminal K159/K162/K163 cluster is required for its nuclear translocation. Transgenic complementation and physiological assays confirmed that substitution of K159/K162/K163 sites into arginine abolished GPX1-mediated osmotic stress tolerance and the activation of bZIP68 target genes. Furthermore, we discovered that HISTONE DEACETYLASE 15 (HDA15) interacts with and deacetylates GPX1. HDA15-mediated deacetylation reduced enzymatic activity, nuclear translocation and subsequently the interaction with bZIP68 of GPX1. Accordingly, HDA15-overexpressing rice showed greater membrane damage, weaker induction of bZIP68-regulated genes and increased sensitivity to osmotic stress. These results identify HDA15-mediated GPX1 deacetylation as a negative regulatory mechanism that connects redox enzyme activity, protein localization and stress-responsive transcription in rice.