OsMYBAS1 Coordinates ABA/JA Signaling and ROS Homeostasis for Seedling Cold Tolerance of Rice (Oryza sativa L.).

Abstract

Seedling cold stress is a major abiotic constraint to rice production, and mining elite cold-tolerant genes from wild rice represents a pivotal strategy to enhance cold tolerance in cultivated rice (Oryza sativa L.). Dongxiang wild rice (DXWR, Oryza rufipogon Griff.) is a valuable genetic resource with robust cold tolerance. However, the underlying molecular regulatory mechanisms remain poorly characterized, and the identification of its elite cold-tolerant genes is still limited. In this study, by integrating high-density gene chip, comparative transcriptomic and functional correlation analyses, we identified OsMYBAS1, an R2R3-MYB transcription factor, as a key regulator conferring cold tolerance of DXWR. The Osmybas1 mutants exhibited drastically reduced survival rate under cold stress, accompanied by excessive reactive oxygen species (ROS) accumulation and significant decreases in antioxidant enzyme activity. Comparative transcriptome analysis of the mutants identified 545 cold-induced differentially expressed genes. Functional enrichment analysis indicated that pathways involved in hormone metabolism and signaling were among the most significantly enriched categories, highlighting their key roles in the cold response. Further detection revealed that endogenous abscisic acid (ABA) and jasmonic acid (JA) levels were markedly down-regulated in Osmybas1 mutants after cold treatment, while exogenous ABA or methyl jasmonate (MeJA) application rescued the cold-sensitive phenotype and reversed the abnormal expression of cold-responsive genes. This study suggested that OsMYBAS1 positively regulated seedling cold tolerance by mediating the coordinated modulation of ABA/JA signaling and ROS homeostasis. These findings elucidated an important molecular mechanism underlying DXWR cold tolerance and provided a novel gene target and theoretical foundation for cold-tolerant rice molecular breeding.