AP2/ERF Transcription Factor OsERF117 Boosts Thermotolerance in Rice at Seedling Stage by Activating Heat Responsive Genes and Reducing ROS Accumulation

Heat stress serves as a critical adverse environmental factor to severely hinder rice ( Oryza sativa L.) growth and productivity. Unraveling key genetic regulators governing thermotolerance in rice is crucial for molecular breeding of heat-resilient varieties. However, limited useful genetic resources has hindered this breeding progress. Here, through heat screening using a rice mutant library, we identify that a nuclear-localized APETALA2/Ethylene Responsive Factor (AP2/ERF) transcription factor OsERF117 functions as a key modulator in response to high temperatures. Loss-of-function mutant seedlings of OsERF117 exhibit increased heat sensitivity and genetic complementation lines show comparable thermotolerance with wild type, whereas overexpression of OsERF117 enhances thermotolerance without yield penalty, indicating its positive role in heat adaptation. physiological analyses reveal that OsERF117 improves rice heat tolerance by enhancing the antioxidant defense system, reducing reactive oxygen species (ROS) accumulation, thereby alleviating heat-induced oxidative damage. Mechanistically, RNA-seq and protein-DNA interaction analysis illustrate that OsERF117 directly binds to the promoter of OsHsfA2c , OsRab16A and OsCatB , and activates their expressions to response heat stress. Importantly, haplotype analysis identifies three major OsERF117 haplotypes, among which indica haplotype OsERF117 Hap2 represents an elite allele associated with superior heat tolerance. Collectively, our findings unveil the molecular role of OsERF117 in heat stress during seedling stage, offering potential valuable haplotype-specific targets for molecular breeding of heat-tolerant rice varieties.