Abstract Background and Aims Drought is widely regarded as a significant abiotic stress restricting the growth of plants via oxidative stress. The ascorbate peroxidase (APX) protein serves a pivotal function in the antioxidant system. However, the function of PagAPX9, a homolog of Arabidopsis thaliana APX1 (AtAPX1), in poplar growth and drought responses remains unclear. Methods In this study, the PagAPX9 gene, which was induced by drought stress and specifically expressed in young leaves and stems, was successfully cloned from the hybrid poplar ‘84K’ (Populus alba × Populus glandulosa) and used to generate PagAPX9 overexpression transgenic poplars (PagAPX9 OE). The morphological characteristics were evaluated and the physiological indicators were explored to explore the mechanism by which PagAPX9 OE plants enhance their drought tolerance. Key Results We found that the PagAPX9 OE lines exhibited promoted high growth and enhanced drought tolerance with better growth performance and fewer wilting symptoms. Physiological analyses showed that PagAPX9 OE had stronger stomatal regulation and higher efficiency in utilizing water, along with enhanced activities of antioxidant enzymes (SOD, POD, CAT) and upregulated expression of antioxidant-related genes. These responses collectively contributed to the maintenance of cellular homeostasis and improved reactive oxygen species (ROS) detoxification under water deficit. Conclusions Our results showed that PagAPX9 enhanced poplar drought resistance via regulating stomatal behavior and ROS scavenging, and identified it as a valuable genetic resource to enhance woody plant drought resilience.
Tian et al. (Fri,) studied this question.