Heat stress severely impairs plant growth and limits crop productivity. GSK3-like family proteins regulate diverse cellular processes, including plant responses to abiotic and biotic stresses. Nevertheless, their specific functions in heat stress responses remain poorly characterized. Here, we demonstrate that the expression of OsSK13 and the protein abundance of OsSK12/13 increase under heat stress in rice. Mutation in both OsSK12/13 compromises thermotolerance at both vegetative and reproductive stages, whereas overexpression of OsSK13 enhances seedling thermotolerance. We further identify that OsSK12/13 physically interact with and phosphorylate the APETALA2/ETHYLENE RESPONSIVE FACTOR (AP2/ERF) transcription factor OsERF60, and phosphorylation by OsSK12/13 enhances the stability of OsERF60. Consistent with its role in this regulatory module, OsERF60 loss-of-function mutants exhibit enhanced thermosensitivity at vegetative and reproductive stages. Expression profiling reveals that induction of heat stress-responsive genes, including OsHsfA2c, is reduced in both the OsSK12/13 double mutant and the OsERF60 mutant. OsERF60 directly binds to the OsHsfA2c promoter and activates its expression. Collectively, our findings uncover the OsSK12/13-OsERF60-OsHsfA2c regulatory module as a key component of the heat stress response in rice and provide mechanistic insights into thermotolerance in plants.
Juan Gao, Zi-Wei Yao, Zhiping Deng et al.· Journal of Integrative Plant...· 0 citations
SUMMARY The ubiquitin‐conjugating enzymes (E2) play critical roles in plant stress responses and development, but their functions in ABA‐mediated seed germination in rice remain largely unknown. We identified two homologous E2 enzymes, OsUBC11 and OsUBC12, which are highly expressed in rice seeds and induced by multiple abiotic stresses including salt, osmotic stress, and ABA treatment. We demonstrated that OsUBC11 and OsUBC12 positively regulate rice seed germination, especially under NaCl and ABA treatment, as the double mutants exhibited delayed germination and hypersensitivity to ABA and salt, while overexpression lines showed accelerated germination and reduced sensitivity. OsUBC11 and OsUBC12 negatively regulate the expression of ABA‐responsive genes, including OsABI3, OsABI5, OsRAB21, and OsLEA3. Protein interaction assays demonstrated that OsUBC11/12 directly interact with OsABI3, a key transcription factor in ABA signaling. OsUBC11/12 possess ubiquitin‐conjugating activity and promote the ubiquitination and subsequent degradation of OsABI3, thereby reducing OsABI3 protein stability. Together, our findings establish that OsUBC11 and OsUBC12 positively regulate seed germination under salt stress by ubiquitinating and destabilizing OsABI3, thus attenuating ABA signaling.
Tian-Ci Xie, Tao Qing, Chuang Yang et al.· The Plant Journal· 0 citations
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