Genome-wide identification of the TGA transcription factor family in Populus alba × Populus glandulosa and functional validation of PagTGA7b in salt tolerance

• Identified 20 TGA TFs with conserved DOG1 and bZIP domains in 84K poplar. • Promoter and PPI network analyses associate TGA with hormonal and stress responses. • 13 PagTGA genes respond to salt stress, with PagTGA7b strongly induced. • PagTGA7b overexpression enhances salt tolerance in yeast and 84K poplar. TGA transcription factors (TFs) belong to the D subfamily of bZIP TFs, play essential roles in plant responses to various abiotic stresses. Although the TGA family has been characterized in multiple plant species, its characterization in 84K poplar ( Populus alba × Populus glandulosa ) remains unexplored. In this research, we identified 20 TGA TFs in the 84K poplar genome, all containing conserved DOG1 and bZIP domains. Phylogenetic analysis classified the PagTGAs into five clades, with Group II possessing the most members. Collinearity analysis revealed six pairs of gene duplication events on both subgenome A and B, all of which were segmental duplications. Promoter analysis indicated diverse cis‑acting elements related to hormonal and stress responses. In addition, results from PPI networks and KEGG enrichment demonstrated that proteins interacting with PagTGAs are predominantly involved in hormone signaling. Transcriptomic profiling of 84K poplar leaves under salt stress revealed significant expression changes in 13 PagTGA genes. Among these, PagTGA7b was markedly upregulated and selected for functional characterization. Further assays confirmed that PagTGA7b localizes to the nucleus and functions as a transcriptional activator. Heterologous overexpression in yeast significantly improved salt tolerance, while transgenic 84K poplar overexpressing PagTGA7b exhibited enhanced salt resistance, mitigating salt‑induced reductions in photosynthetic performance. Taken together, these results indicate that most TGA family members in 84K poplar contribute to salt stress adaptation, with PagTGA7b identified as a key regulator. This study advances understanding of the TGA family’s evolutionary and functional roles and provides valuable genetic resources for developing salt‑tolerant poplar cultivars.