A tau class glutathione S-transferase in alfalfa, MsGSTU17, regulates salt tolerance in transgenic Arabidopsis thaliana

High soil salinity negatively affects crop yield, intrinsic quality, and economic profitability. The tau class of glutathione S-transferases (GSTs) is pivotal in plant defense mechanisms against salt stress. In this study, we characterized a salt-responsive tau-class GST gene, designated as MsGSTU17, in Medicago sativa. The MsGSTU17gene was found to be located in the cytoplasm and had high expression levels in both leaves and roots. Compared to the wild-type plants, overexpression of MsGSTU17 in Arabidopsis under salt stress led to increased root length, shoot weight, and survival rate, along with a reduced ion leakage rate. At the same time, the transgenic Arabidopsis lines showed significantly increased expression of genes related to salt stress, including SOS1, SOS2, SOS3, KIN2, RD29A, and HKT1, compared to the wild-type. Additionally, these transgenic plants exhibited an enhanced antioxidant defense system characterized by elevated activities of catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), GST, and glutathione reductase (GR), and higher levels of glutathione (GSH). In summary, our results suggest that overexpressing MsGSTU17 in transgenic plants can mitigate salt-caused damage by scavenging reactive oxygen species and increasing GSH levels via upregulation of GST activity.