The OsUVR8-OsNAC3-OsERF117 signaling module mediates metabolic acclimation and climate adaptation in rice.

Ultraviolet-B (UV-B; 280 to 315 nanometers) radiation increasingly threatens crop productivity, yet the genetic basis of plant adaptation remains poorly understood. We delineate a UV-B signaling module in rice that links photoreceptor activation to transcriptional reprogramming and metabolic acclimation. The AP2/ERF transcription factor OsERF117 acts as a central regulator, directly activating flavonoid and melatonin biosynthetic genes to drive photoprotective metabolite accumulation and enhance UV-B stress tolerance. Promoter variation in OsERF117 defines 10 haplotypes across 4093 rice accessions, with high-expression haplotypes enriched in high-UV-B regions and correlated with adaptive divergence. OsERF117 is transcriptionally activated by OsNAC3, with a cis-regulatory SNP at an OsNAC3-binding site modulating responsiveness and contributing to subspecies diversification. Genetic and biochemical evidence supports a model in which UV-B-activated OsUVR8 promotes OsNAC3 activity and antagonizes OsCOP1-mediated ubiquitination and degradation in rice. This OsUVR8-OsCOP1-OsNAC3-OsERF117 module reveals how UV-B perception drives regulatory and metabolic diversification, offering targets for breeding UV-B-resilient crops.