Abstract
Rad51, eukaryotic homologues of RecA, plays key roles in DNA double-strand break (DSB) repair via homologous recombination (HR) as recombinase. We previously reported two rice Rad51 genes (OsRAD51A1 and OsRAD51A2) which were induced by DNA damaging agents. We analyzed the effect of OsRad51 gene expression using transgenic rice plants. Expression of OsRad51A2 promoter::gusA chimeric gene in rice calli and plants was quickly and remarkably up-regulated by DSB inducers such as gamma-ray and bleomycin. Antisense expression of OsRad51A1 cDNA conferred growth retardation at vegetative and reproductive phases in T2 transgenic rice plants. Those T2 transgenic lines also displayed hypersensitivity against gamma-ray irradiation. These results indicated that OsRad51A2 expression is controlled at transcription level by its 5'-upstream sequence containing the possible DNA-damage responsive element, and that lowering OsRad51 transcript levels could raise sensitivity toward DSB inducers by inhibiting formation of HR-machinery sufficient for DSB repair.
