WRKY transcription factor RrWRKY56 negatively regulates salt and drought stress tolerance by suppressing RrUSP expression in Rosa rugosa

Abiotic stresses, particularly drought and salinity, significantly constrain plant growth and productivity. While many transcription factors modulate stress responses, the regulatory mechanisms of WRKY transcription factors in Rosa species remain poorly understood. In this study, we identified and characterized RrWRKY56, a novel WRKY transcription factor from Rosa rugosa, and investigated its role in regulating stress responses through interaction with the universal stress protein gene RrUSP. Results from yeast one-hybrid and dual-luciferase reporter assays demonstrated that RrWRKY56 directly binds to the RrUSP promoter. Transient overexpression of RrWRKY56 in R. chinensis leaves increased sensitivity to salt and drought stresses, manifested by enhanced leaf damage, decreased activities of antioxidant enzymes (superoxide dismutase and peroxidase), and elevated malondialdehyde levels under stress conditions. Transcriptomic analysis revealed that RrWRKY56 primarily suppressed critical adaptive pathways including carbohydrate metabolism and phytohormone signaling, thereby compromising stress tolerance mechanisms. Conversely, overexpression of RrUSP enhanced stress tolerance by improving antioxidant enzyme activities and reducing oxidative damage. Our findings illustrate that RrWRKY56 functions as a negative regulator while RrUSP acts as a positive regulator of stress tolerance, forming an antagonistic regulatory module that fine-tunes abiotic stress responses in R. rugosa. This study provides valuable genetic resources for stress-resistant breeding and enriches our understanding of plant stress regulatory networks, particularly highlighting the potential for molecular breeding approaches to enhance stress tolerance in Rosa species.