OsERF5 enhances cold tolerance and is associated with GA‑mediated antioxidant defence in rice.

OsERF5, an AP2/ERF transcription factor, positively regulates seedling cold tolerance in rice and is associated with gibberellin signalling and reactive oxygen species homeostasis; its cold‑tolerant haplotype Hap_I provides a valuable genetic resource for breeding cold‑adapted rice in high‑latitude/high‑altitude regions. Low-temperature stress severely limits rice growth and productivity, especially at the seedling stage. Identifying key cold-tolerance genes and dissecting their mechanisms is therefore crucial for breeding improvement. Here, we isolated a cold-sensitive mutant (cs1) from an EMS-mutagenized population of the cold-tolerant japonica line MK1. Genetic analysis indicated that the phenotype is controlled by a single recessive nuclear gene. MutMap mapping localized the causal locus to a region on chromosome 9 containing OsERF5, which encodes an AP2/ERF transcription factor. A nonsynonymous SNP in its AP2 domain causes an alanine-to-serine substitution. OsERF5 is widely expressed and induced by cold, salinity, osmotic stress, and gibberellin (GA). Knockout of OsERF5 reduced seedling cold tolerance, while overexpression or complementation enhanced it, confirming its positive role. Physiological analyses showed that OsERF5 is linked to strengthened, correlated with reduced H₂O₂ and malondialdehyde accumulation under cold stress. Haplotype analysis identified 12 haplotypes, with the cold-tolerant Hap_I predominant in temperate japonica rice. Population genetics evidence indicates that OsERF5 has undergone strong selection during domestication. Our study demonstrates that OsERF5 positively regulates cold tolerance in rice and is associated with the GA‑mediated antioxidant defence system, providing both a genetic resource and a molecular framework for breeding cold‑tolerant varieties.