Somatic embryogenetic receptor kinase <scp>TaSERL2</scp> regulates heat stress tolerance in wheat by influencing <scp>TaBZR2</scp> protein stability and transcriptional activity

Heat stress is a major factor limiting crop yield, a challenge intensified by climate change. Initial findings indicate that BES1/BZR1 may use heat shock to regulate plant thermal adaptability independently of BIN2-mediated brassinosteroid signalling, although the exact molecular mechanism remains unclear. In this study, we identified TaBZR2, a wheat gene whose expression showed a strong positive correlation with heat stress tolerance, based on transcriptome analysis of heat-tolerant wheat cultivars. Overexpression of TaBZR2 enhanced heat stress tolerance, while RNA interference of TaBZR2 reduced it. Further analysis revealed that TaBZR2 interacts with and is phosphorylated by wheat somatic embryogenesis receptor-like kinase 2 (TaSERL2). Overexpression of TaSERL2 reduced heat stress tolerance by promoting TaBZR2 degradation and inhibiting its regulation of wheat heat stress response genes. However, heat stress reduced the phosphorylation levels of both TaSERL2 and TaBZR2, lessening TaSERL2's inhibitory effect on TaBZR2 and enhancing the stability of TaBZR2. These results reveal that the TaSERL2-TaBZR2 module negatively regulates plant heat stress tolerance. This study expands the current model of heat stress responses and provides evidence for the role of BES1/BZR1 in heat stress regulation independent of brassinosteroid signalling.