Knockdown of VvMYBA1 via virus-induced gene silencing decreases anthocyanin biosynthesis in grape berries

Anthocyanin in grapevines, regulated by structural and regulatory genes, determines the colour of grape berries and is a key factor in wine quality. The transgenic approach is a useful strategy for elucidating gene function. However, it is difficult to obtain transgenic fruit trees, including grapevines. Viral vectors offer an effective strategy for overcoming this challenge. In this study, we successfully knocked down the VvMYBA1 gene in 'Red Globe' and 'JiZaoMi' grape berries via virus-induced gene silencing (VIGS) by vacuum infiltration and silencing efficiencies of 73% and 93%, respectively, were obtained relative to the control. Total anthocyanins content was reduced 1.7- and 2.7-times relative to that in the control in 'Red Globe' and 'JiZaoMi' grape berries, respectively. The expression levels of VvUFGT and VvDFR were reduced by 80% and 8% and by 72% and 42% relative to the control in 'Red Globe' and 'JiZaoMi' grape berries, respectively, in the anthocyanin metabolic pathways. Tobacco rattle virus-mediated VIGS was, therefore, successfully established in grape berries. These findings provide direct evidence that VvMYBA1 encodes skin colour in red grape berries and suggest a possible application of VIGS for gene function studies in other fruits.