Small G Protein OsRab6a Confers Cold Tolerance by Cooperating With OsRAN2 and Suppressing ABA Signalling in Rice.

Global climate change has increased the frequency of extreme low-temperature events, severely affecting rice production worldwide. Although numerous cold-tolerance genes have been mapped and cloned over the past four decades, the molecular mechanisms governing rice's response to cold stress remain incompletely understood. In this study, we employed an integrated approach combining reverse genetics, biochemical assays, and molecular biology to elucidate the role of OsRab6a, a small GTP-binding protein, in rice cold tolerance. Functional analyses demonstrated that OsRab6a overexpression enhances cold tolerance in transgenic rice, whereas OsRab6a mutants display heightened cold sensitivity at both the bud and seedling stages. Cold stress strongly induced OsRab6a expression, particularly in seedling roots. Mechanistically, OsRab6a physically interacts with OsRAN2, a known cold-resistance protein, under cold stress and acts upstream of OsRAN2 in the cold response pathway. Furthermore, OsRab6a upregulates OsPYL3 to modulate ABA signalling during cold stress. Our findings reveal that OsRab6a is a critical regulator of both cold tolerance and ABA signalling in rice. This study advances the understanding of OsRab6a-mediated cold stress responses and provides a valuable genetic engineering target for improving cold tolerance in rice.