Functional Characterization of GA2ox3 in Rice Osmotic Stress Response and Identification of a Superior Allele for Breeding Applications

Drought is a major abiotic stress limiting rice production worldwide. GA2ox3, a GA 2-oxidase involved in gibberellin deactivation, has been previously linked to growth regulation. Here, we demonstrate that functional disruption of GA2ox3 enhances shoot growth but compromises drought tolerance in rice. CRISPR/Cas9 knockout lines (ga2ox3) showed increased plant height and reduced antioxidant capacity under 20%PEG-induced osmotic stress, evidenced by higher H2O2 and MDA accumulation and decreased POD activity. Moreover, expression analysis revealed that GA2ox3 may be associated with the GA signaling cascade involving OsSLR1, OsBURP3, and OsSUS1. Haplotype analysis based on 627 rice accessions identified two major alleles, Hap1 and Hap2, with Hap1 showing higher GA2ox3 expression and stronger drought resilience. These findings suggest that GA2ox3 positively regulates osmotic stress tolerance, and its natural variation represents promising genetic resources for improving drought adaptation in rice.