Abstract

Anthocyanins are critical pigments that determine plant tissue coloration, but the regulatory mechanisms governing their accumulation in red-fleshed grape leaves remain unclear. Using red-leafed (H4) and green-leafed (L) lines derived from a cross of the red-fleshed grape 'Zhongshan Hongyu' with 'Shine Muscat', we show that leaf color variation is directly correlated with differential anthocyanin content. Through expression profiling, we identified VvWRKY44 , a WRKY transcription factor highly expressed in H4. Nuclear localization was observed for VvWRKY44. Transgenic tobacco plants overexpressing VvWRKY44 exhibited both higher anthocyanin levels and enhanced transcript levels of several anthocyanin biosynthetic genes. Mechanistically, VvWRKY44 directly bound and activated the VvF3H promoter. Upstream analysis revealed VvWRKY44 as a direct target of VvMYBA1. Additionally, VvMYB308 antagonized VvWRKY44 through dual mechanisms including transcriptional repression and direct physical interaction. This study elucidates a VvMYBA1-VvWRKY44-VvMYB308 regulatory module governing anthocyanin biosynthesis in the red-fleshed grape leaves.