The E3 ligase TaGW2L mediates the ubiquitination and degradation of TaHMT1 to negatively regulate salt tolerance in wheat

RING finger E3 ligases are critical in regulating plant growth, development, and environmental responses; however, their role in wheat salt tolerance remains poorly understood. In this study, we identify TaGW2L, a GW2-like RING E3 ubiquitin ligase, as a novel regulator of salt tolerance in wheat. Expression analysis shows that TaGW2L homoeologs are downregulated in response to NaCl and ABA treatments. Overexpression of TaGW2L-7A resulted in a salt-sensitive phenotype, characterized by reduced survival rates, elevated reactive oxygen species (ROS) production, and decreased chlorophyll content under salt stress. Conversely, TaGW2L knockout lines exhibited enhanced salt tolerance, with improved survival rates, higher chlorophyll content, and lower ROS levels compared to wild-type plants. Transcriptome analysis revealed that TaGW2L knockout leads to the upregulation of salt-responsive genes, particularly those involved in ABA and ROS pathways. Ubiquitinome and biochemical analyses demonstrated that TaGW2L negatively regulates salt tolerance by mediating the ubiquitination and degradation of TaHMT1, a positive regulator of salt stress responses. Loss-of-function mutations in TaHMT1-5A impaired salt tolerance in wheat. This study underscores the critical role of the ubiquitin-proteasome system in wheat's salt stress response and offers new insights into potential targets for improving salt tolerance in wheat.