The <scp>OsMPK9</scp> – <scp>OsCDR1</scp> module regulates abiotic stress responses in rice

Rice (Oryza sativa L.), originating from tropical and subtropical regions, is a cold-sensitive and water-demanding crop whose yield and quality are severely compromised by chilling injury or water deficits during growth and development. In this study, we systematically characterized Cold and Drought Resistance 1 (OsCDR1), a nucleus-localized transcription activator belonging to the bZIP transcription factor family. OsCDR1 overexpression enhances rice tolerance to cold and drought stress, whereas knockout mutants of OsCDR1 exhibit reduced resistance to low temperatures and drought conditions. Furthermore, OsCDR1 positively regulates abscisic acid (ABA) signaling in rice, and mediates ABA-regulated drought tolerance responses in rice. Integrated RNA-seq and CUT&Tag analyses demonstrated that OsCDR1 coordinates with ABA-dependent (PIP2;2) and -independent genes (DREB1J). OsCDR1 specifically binds to the G-box cis-element in the promoters of PIP2;2 and DREB1J, thereby activating their transcription and regulating the abiotic stress responses in rice. Protein interaction analysis revealed that OsCDR1 interacts with the kinase OsMPK9 in vivo and in vitro, and a dual-luciferase reporter assay showed that OsMPK9 and OsCDR1 regulate the transcription of DREB1J and PIP2;2 in the same functional pathway. Overexpression of OsMPK9 inhibits ABA responses in rice and reduces cold and drought tolerance. Our findings establish the OsMPK9-OsCDR1 module as a critical hub connecting ABA signaling to abiotic stress resilience, providing new insights for breeding crops.