OsYchF1 suppresses OsEF1Bγ-mediated ER detoxification to co-involve the growth-maintenance trade-off in rice.

Abstract

Translation elongation is a fundamental biological process, yet its direct role in stress adaptation remains unclear. In this study, we uncover a novel regulatory axis in rice involving the unconventional G protein OsYchF1, which gates the detoxification activity of the elongation factor 1Bγ (OsEF1Bγ) in the endoplasmic reticulum. OsEF1Bγ is a subunit of the eEF1B complex and possesses an N-terminal glutathione S-transferase (GST) domain. We demonstrate that overexpression of OsEF1Bγ enhances rice tolerance to osmotic and saline stress by lowering malondialdehyde levels, suggesting its role as a positive regulator via GST-mediated detoxification. Conversely, we found that OsYchF1 interacts with OsEF1Bγ across multiple domains. This interaction competitively inhibits the binding of reduced glutathione to OsEF1Bγ by approximately 40-fold, thereby suppressing its GST activity in vitro. Consistently, OsYchF1 knockout mutants phenocopy OsEF1Bγ overexpressors, displaying enhanced stress tolerance, reduced reactive oxygen species accumulation, and increased antioxidant enzyme activities. Furthermore, we show that stress-induced downregulation of OsYchF1 acts as a physiological trigger, releasing this molecular brake to enable rapid activation of OsEF1Bγ-mediated detoxification in response to challenging environments. Collectively, our findings reveal a post-translational mechanism where OsYchF1 serves as a molecular brake on the ER-localized detoxification engine of OsEF1Bγ, fine-tuning abiotic stress adaptation and establishing an unexpected link between the translation machinery and cellular redox homeostasis.