Overexpression of OsRDCP1, a rice RING domain-containing E3 ubiquitin ligase, increased tolerance to drought stress in rice (Oryza sativa L.)

CaRma1H1 was previously identified as a hot pepper drought-induced RING E3 Ub ligase. We have identified five putative proteins that display a significant sequence identity with CaRma1H1 in the rice genome database (http://signal.salk.edu/cgi-bin/RiceGE). These five rice paralogs possess a single RING motif in their N-terminal regions, consistent with the notion that RING proteins are encoded by a multi-gene family. Therefore, these proteins were named OsRDCPs (Oryza sativa RING domain-containing proteins). Among these paralogs, OsRDCP1 was induced by drought stress, whereas the other OsRDCP members were constitutively expressed, with OsRDCP4 transcripts expressed at the highest level in rice seedlings. osrdcp1 loss-of-function knockout mutant and OsRDCP1-overexpressing transgenic rice plants were developed. Phenotypic analysis showed that wild-type plants and the homozygous osrdcp1 G2 mutant line displayed similar phenotypes under normal growth conditions and in response to drought stress. This may be due to complementation by other OsRDCP paralogs. In contrast, 35S:OsRDCP1 T2 transgenic rice plants exhibited improved tolerance to severe water deficits. Although the physiological function of OsRDCP1 remains unclear, there are several possible mechanisms for its involvement in a subset of physiological responses to counteract dehydration stress in rice plants.

► There are at least five homologous OsRDCP (Oryza sativa RING domain-containing protein) family members, all of which contain a single RING motif in their N-terminal regions in rice plants.
► Among these rice paralogs, OsRDCP1 was induced by drought stress.
► Loss-of-function rice mutant plants (osrdcp1) containing a T-DNA copy integrated into the OsRDCP1 gene and OsRDCP1-overexpressing transgenic rice plants (35S:OsRDCP1) were developed.
► Wild-type plants and the homozygous osrdcp1 G2 mutant line displayed similar phenotypes under normal growth conditions and in response to drought stress.
► OsRDCP1-overexpressing T2 transgenic rice plants exhibited markedly improved tolerance to severe water deficits.