Functional Analysis of PdbERF109 Gene Regulation of Salt Tolerance in Populus davidiana × P. bolleana

ERF family transcription factors are crucial regulators in plants, playing a central role in abiotic stress responses and serving as important targets for stress-tolerant crop breeding. Populus davidiana × P. bolleana, an elite hybrid poplar cultivar artificially selected in northern China, holds significant research value encompassing ecological restoration, economic industries, genetic resource development, and environmental adaptability. This study identified that PdbERF109 expression was significantly upregulated in P. davidiana × P. bolleana response to salt treatment. Furthermore, transgenic poplar lines overexpressing PdbERF109 (OE) were generated. Salt stress assays demonstrated that PdbERF109 overexpression significantly enhanced salt tolerance in transgenic poplar. Compared to wild-type (WT) plants, PdbERF109-OE lines exhibited a significant enhancement in the activities of antioxidant enzymes, with increases of 2.3-fold, 1.2-fold, and 0.5-fold for superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), respectively, while the levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) were markedly reduced by 39.89% and 40.03%, indicating significantly enhanced reactive oxygen species (ROS) scavenging capacity and reduced oxidative damage. Concurrently, PdbERF109 overexpression reduced the natural leaf relative water loss (%). Meanwhile, yeast one-hybrid assays confirmed that the PdbERF109 protein specifically binds to GCC-box and DRE cis-acting elements. This study established PdbERF109 as a positive regulator of salt stress responses, highlighting its potential as a target gene for improving plant tolerance to high salinity, providing a promising candidate gene for the molecular breeding of salt-tolerant crops.