Abstract: Excessive exposure to high light can lead to photoinhibition, which impairs photosynthetic efficiency and causes oxidative damage in plants, such as sunburn in grapevines. This study investigates the role of resveratrol (Res), a stilbenoid with antioxidant properties, in protecting plants from high light damage. We found that exposure to high light increased reactive oxygen species (ROS) accumulation and induced photoinhibition in grapevine leaves. In response, Res biosynthesis was upregulated, along with an increase in stilbene synthase (VvSTS) expression. Application of exogenous Res alleviated ROS accumulation and improved photosynthetic efficiency. Further analysis revealed that the VvHY5-VvBEE1 regulatory module plays a pivotal role in regulating VvSTS expression under high light conditions. Specifically, VvHY5 activated VvSTS expression, while VvBEE1 repressed it. Transgenic analysis showed that overexpression of VvHY5 enhanced Res production and photoprotection, whereas overexpression of VvBEE1 reduced Res levels and exacerbated light-induced damage. VvHY5 and VvBEE1 competed for binding to the VvSTS promoter, with brassinosteroids (BRs) modulating their interaction. Our findings reveal the interplay between light signaling and brassinosteroid pathways in regulating Res biosynthesis, providing insights for protecting grapevines from sunburn.

Key words: grapevine, high light, resveratrol, VvBEE1, VvHY5