BpMAPK6-mediated phosphorylation of BpDRE1B enhances drought tolerance in Betula platyphylla via activating GST for antioxidant defense.
Drought is a major environmental factor that affects Betula platyphylla (birch) survival and growth and even leads to death in severe cases. However, the genetic components underlying birch drought tolerance are largely unknown. Here, we identified and characterized a DREB gene (BpDRE1B) in birch, and overexpression of BpDRE1B improved the drought tolerance of transgenic birch. Through analysis of the previously reported drought regulatory network of birch, it was found that glutathione metabolism serves as a key pathway underlying BpDRE1B-mediated drought stress responses. Yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation-qPCR (ChIP-qPCR), and dual-luciferase (dual-LUC) assays confirmed that BpDRE1B regulates the expression of BpGSTU8 by binding to its DRE element. Consistently, overexpression of BpGSTU8 (OE-BpGSTU8) was identified to increase the activity of glutathione-S-transferase to clear reactive oxygen species (ROS), thereby enhancing the drought resistance of birch. The protein interaction analysis revealed that BpDRE1B interacts with BpMAPK6, a kinase involved in stress signaling. Moreover, BpMAPK6-mediated phosphorylation of BpDRE1B enhanced its ability to activate BpGSTU8 expression. Collectively, our findings demonstrate that BpDRE1B positively regulates drought tolerance in birch by upregulating BpGSTU8, highlighting its crucial role in drought adaptation and providing a theoretical foundation for breeding drought-resistant birch varieties.