OsCBE1, a Substrate Receptor of Cullin4-Based E3 Ubiquitin Ligase, Functions as a Regulator of Abiotic Stress Response and Productivity in Rice

Ubiquitination is an important environmental stress response, and E3 ubiquitin ligases play a major role in the process. T-DNA insertion mutants of rice, , and were identified through the screening of cold stress tolerance at seedling stage. s mutants showed a significantly higher cold stress tolerance in the fresh weight, chlorophyll content, and photosynthetic efficiency than wild type. Molecular prediction showed that ( Cullin4-Based E3 ubiquitin ligase1) encoded a novel substrate receptor of Cullin4-based E3 ubiquitin ligase complex (C4E3). Whereas mutants had fewer panicles and grains than wild type in the paddy field, the overexpression lines of had more panicles and grains, suggesting that is involved in the regulation of both abiotic stress response and development. mutants also showed ABA hypersensitivity during seed germination, suggesting function for the stress response via ABA signaling. In silico analysis of OsCBE1 activity predicted a CCCH-type transcription factor, OsC3H32, as a putative substrate. Co-IP (Co-immunoprecipitation) study showed that OsCBE1 interacts with OsDDB1, an expected binding component of OsCBE1 and OsC3H32. Additionally, expression of , and were negatively related with expression of . These results suggest that functions as a regulator of the abiotic stress response via CCCH as a member of the C4E3.