OsRVE1 and OsRVE2 Promote Salinity Tolerance in Rice by Directly Activating OsSAPK5 and Modulating ABA Signalling.

Abstract

Soil salinity severely limits rice productivity, yet the transcriptional mechanisms connecting salt stress with abscisic acid (ABA) signalling remain incompletely understood. Here, we identify the MYB-related transcription factors OsRVE1 and OsRVE2 as positive regulators of salinity tolerance in rice. Both genes were induced by salt and ABA, and simultaneous disruption of OsRVE1 and OsRVE2 caused pronounced salt hypersensitivity, whereas their overexpression enhanced salt tolerance, indicating partially redundant functions. Loss of OsRVE1/2 impaired ion and redox homoeostasis, stomatal regulation, and ABA responsiveness under salinity stress. Transcriptome analysis further revealed broad repression of stress- and ABA-responsive genes in the double mutant. OsRVE1 and OsRVE2 localised to the nucleus and functioned as transcriptional activators. Multiple molecular assays demonstrated that both proteins directly bind to the OsSAPK5 promoter and activate its expression. Importantly, ectopic expression of OsSAPK5 substantially restored salt tolerance in the osrve1; osrve2 mutant. Together, these findings establish an OsRVE1/OsRVE2-OsSAPK5 regulatory module that promotes rice salinity tolerance by reinforcing ABA-dependent stress responses.