Inoculation With Bacillus Enhances the Drought Tolerance Function of PlGLK1 in Paeonia lactiflora Pall

In plants, GOLDEN2-like (GLK) transcription factors have become the focus of research on drought tolerance mechanisms due to their pivotal role in coordinating photosynthesis, stomatal movement and antioxidant defense. However, the roles of GLK transcription factors in Paeonia lactiflora (P. lactiflora), particularly those associated with Bacillus and drought stress, remain poorly understood. Here, we isolated the GARP family gene PlGLK1 from P. lactiflora. PlGLK1 is a nuclear-localized protein specifically induced by Bacillus and drought stress, and it harbors transcriptional activation activity. Functional studies on herbaceous peony revealed that PlGLK1-overexpressing lines showed significantly elevated catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) activities, proline and soluble sugar contents, wider stomatal aperture, and reduced H₂O₂, O₂ ^- and malondialdehyde (MDA) levels relative to wild-type plants, whereas VIGS lines showed the opposite trends. Importantly, these two pathways, the stomatal regulation pathway and the ROS scavenging pathway, could further enhance drought resistance following Bacillus inoculation. Yeast one-hybrid (Y1H), dual-Luciferase Reporter (Dual-LUC) and electrophoretic mobility shift assays (EMSA) revealed that PlGLK1 modulated the expression of PlWRKY40, a dehydration stress-responsive gene in plants. Our findings suggest that PlGLK1, induced by Bacillus, plays a crucial role in enhancing dehydration stress tolerance in herbaceous peony plants by promoting stomatal closure and enhancing ROS scavenging capacity.