A novel OsCRK14-OsRLCK57-MAPK signaling module activates OsbZIP66 to confer drought resistance in rice

Abstract

Drought stress severely limits rice productivity. Understanding of drought-response mechanisms in rice is essential for developing climate-resilient varieties. While cysteine-rich receptor-like kinases (CRKs) are primarily implicated in plant development and immunity, their role in drought response remains poorly understood. In this study, we identified a CRK, OsCRK14, as a key positive regulator of drought resistance in rice. We demonstrated that plasma membrane-localized OsCRK14 phosphorylates the receptor-like cytoplasmic kinase OsRLCK57 under drought stress, leading to activate a mitogen-activated protein kinase (MAPK) cascade (OsMKKK10-OsMKK4-OsMPK6). Activated OsMPK6 directly phosphorylates the abscisic acid-responsive transcription factor OsbZIP66 at conserved Serine-Proline/Threonine-Proline motifs, enhancing its stability and promoting drought-responsive gene expression. Furthermore, we found that natural variations in the OsCRK14 promoter influence its transcript levels due to the altered OsMYB72 binding affinities, which are correlated with drought-resistance differences among rice varieties. Collectively, our study discovers a novel CRK-RLCK-MAPK-bZIP signaling pathway that connects membrane signal sensing to transcriptional regulation in drought response, providing both mechanistic insights and genetic resources for breeding drought-resistant rice.

Keywords: CRK; MAPK cascade; RLCK; drought resistance; phosphorylation; rice.