Identification of Pb-responsive GST transcripts in Salix integra and Pb tolerance of transgenic plants overexpressing SiGSTU55.

The escalating severity of soil Pb pollution has intensified the focus on phytoremediation technologies. The biomass advantages of woody plants offer broader prospects for their application in phytoremediation. Fast-growing woody plant Salix integra exhibit significant potential for remediating Pb pollution. Previous research by our team identified GST gene as the gene with most abundant differential expression transcripts in S. integra responding to Pb stress. Leveraging transcriptomic data of S. integra responding to Pb, we identified 22 Pb-responsive SiGST transcripts. Temporal expression analysis under Pb stress revealed 14 transcripts with significant Pb responsiveness, 8 of which were enriched in the "glutathione metabolism" pathway. Using similarity analysis with proteins from 10 Salicaceae species, we selected the most specific SiGSTU55 protein for further functional validation. Overexpression studies in Arabidopsis thaliana and poplar, along with Pb treatment experiments, demonstrated that SiGSTU55 enhances Pb tolerance in transgenic A. thaliana by stimulating root growth and in transgenic poplar by boosting GST activity, GSH, and PC contents under Pb stress, resulting in significantly greater height growth of transgenic poplar in Pb-containing soil. This study not only identified Pb-responsive SiGSTs in S. integra but also confirmed the capacity of the highly specific SiGSTU55 gene to enhance Pb tolerance in transgenic plants. It offers a reference for research into heavy metal tolerance of GST genes in other plants and establishes a foundation for the application of woody plants in remediating Pb-contaminated soil.