Magnesium-dependent phosphatase 1 (MDP1) interacts with WRKY 53 and protein phosphatase 2C 80 (PP2C80) to improve salt stress tolerance by scavenging reactive oxygen species in Salix psammophila

The roles of haloacid dehalogenase-like hydrolase (HAD) proteins in plants under salt stress remain largely unexplored. In the present study, we identified and functionally characterized SpsMDP1, a member of the HAD family, from Salix psammophila, which is a shrub adapted to desert environments. SpsMDP1 was strongly upregulated by salt stress. Ectopic expression of SpsMDP1 in Arabidopsis and poplar enhanced salt tolerance, with increased peroxidase activity and less ROS accumulation. Enhanced xylem development was in transgenic poplar plants overexpressing SpsMDP1. Moreover, Y2H, Co-IP, BiFC, and luciferase complementation analyses demonstrated that SpsPP2C80 can interact with SpsMDP1 both in vitro and in vivo. In addition, Y1H, EMSA, and transient expression analysis revealed that SpsWRKY53 is an upstream regulator of SpsMDP1 and can directly bind to the W-box in the promoter region and activate its expression. Both SpsWRKY53 and SpsPP2C80 can increase salt stress tolerance by increasing the activity of antioxidant enzymes. Taken together, in our study we propose a model for the SpsWRKY53–SpsMDP1–SpsPP2C80 module to defend against salt stress by scavenging reactive oxygen species. Our results provide a foundation for better understanding the function of SpsMDP1 in response to salt in S. psammophila and identifying candidate genes for transgenic salt resistance breeding.