VvGAMYB Orchestrates Multi-Signaling Networks to Modulate GA-Induced Parthenocarpic Seedless Berry Development in Grapes.

Exogenous gibberellin (GA) efficiently induces seeded grape parthenocarpy and improves berry quality, with VvGAMYB serving as a key response factor. However, the VvGAMYB-mediated regulatory networks underlying this process remain unclear. In this study, GA3 treatment induced ovule abortion in 'Wink' grape, leading to the formation of parthenocarpic seedless berries. Exogenous GA drastically repressed VvGAMYB levels, thereby promoting parthenocarpy in grape ovaries. Through protein interaction screening, we identified 181 predicted VvGAMYB-associated proteins, which include differentially expressed genes related to hormone signaling, sugar metabolism, and transcriptional regulation, and further revealed that GA-induced grape parthenocarpy likely operates through a VvGAMYB-mediated network, coordinating key genes such as VvGID1B (GA signaling), VvRAP2-4 (ETH signaling), VvGAPC2 (glycolysis), and VvMETKs (methylation modification). Among these candidates, VvGAMYB repressed VvMETK2 promoter activity, whereas GA3 treatment weakened this repression, as demonstrated by a dual-luciferase assay in tobacco. Collectively, this study established an integrative framework in which VvGAMYB orchestrates phytohormone crosstalk, sugar metabolism, and epigenetic modification during GA-induced parthenocarpy. Our findings provide significant insights into the molecular network of GA-induced grape parthenocarpy and offer key target genes for the molecular breeding of high-quality seedless grapes.