Transgenic rice plants carrying RNA interference constructs of AOS (allene oxide synthase) genes show severe male sterility

Male sterility is an important trait for rice breeding programmes based on heterosis. To generate male-sterile plants, we utilized RNAi technology with the promoters for two anther-specific genes, Osc4 and Osg6b, and one for rice allene oxide synthase (OsAOS). AOS catalyzes the biosynthesis of jasmonic acid and plays an important role in anther development. The promoters isolated from Osc4 and Osg6b were introduced into pK7gwiwgL, a promoter-less RNAi Gateway binary vector. Partial DNA fragments of OsAOS1 and OsAOS2 were combined into the Osc4::RNAi and Osg6b::RNAi cassettes by LR recombination. The resulting four RNAi constructs were transformed into rice calli by Agrobacterium. During the reproductive growth stage, 28% of OsAOS1 and 48% of OsAOS2 transgenic plants under the control of the Osg6b promoter exhibited a complete- or severe-sterility phenotype compared with the normal wild type. Here, we report that RNA interference of OsAOS2 with the Osg6b promoter is the most effective system for obtaining engineered genic male sterility in rice.