OsPP2C03 positively regulates rice drought stress resistance through a non-canonical ABA pathway

Drought is a major factor limiting rice (Oryza sativa L.) production, making the identification of drought-related genes crucial for enhancing drought resistance in rice breeding. The Protein Phosphatase 2 C (PP2C) family, comprising serine/threonine protein phosphatases, plays critical roles in hormonal signaling pathways that orchestrate plant responses to biotic and abiotic stresses. Here, we identified OsPP2C03 (LOC_Os01g32964), an H-clade PP2C gene, as a drought-tolerance candidate through genome-wide association studies (GWAS). Phenotypic characterization reveals that disruption of OsPP2C03 significantly attenuated drought tolerance in rice. Mechanistic investigations demonstrate that OsPP2C03 modulates abscisic acid (ABA)-mediated signaling pathways by influencing stomatal aperture regulation. We further found that under osmotic stress, OsPP2C03 translocated from the nucleus to the cytoplasm. Yeast one-hybrid and LUC assays reveal OsORR2 functions as an upstream transcriptional regulator of OsPP2C03. Given that it has established the role of OsORR2 in salt stress adaptation, we propose that OsPP2C03 is also involved in osmotic stress-related signaling networks. These findings provide insights for further elucidating the OsPP2C03-mediated mechanisms underlying drought response in rice.