A rice seed-specific glycine-rich protein OsDOR1 interacts with GID1 to repress GA signaling and regulates seed dormancy.

Seed dormancy is an important agronomic trait under the control of complex genetic and environmental interactions, which have not been yet comprehensively understood. From the field screening of rice mutant library generated by a Ds transposable element, we identified a pre-harvest sprouting (PHS) mutant dor1. This mutant has a single insertion of Ds element at the second exon of OsDOR1 (LOC_Os03g20770), which encodes a novel seed-specific glycine-rich protein. This gene successfully complemented the PHS phenotype of dor1 mutant and its ectopic expression enhanced seed dormancy. Here, we demonstrated that OsDOR1 protein binds to the GA receptor protein, OsGID1 in rice protoplasts, and interrupts with the formation OsGID1-OsSLR1 complex in yeast cells. Co-expression of OsDOR1 with OsGID1 in rice protoplasts attenuated the GA-dependent degradation of OsSLR1, the key repressor of GA signaling. We showed the endogenous OsSLR1 protein level in the dor1 mutant seeds is significantly lower than that of wild type. The dor1 mutant featured a hypersensitive GA-response of α-amylase gene expression during seed germination. Based on these findings, we suggest that OsDOR1 is a novel negative player of GA signaling operated in the maintenance of seed dormancy. Our findings provide a novel source of PHS resistance.