Identification and characterisation of F3GT1 and F3GGT1, two glycosyltransferases responsible for anthocyanin biosynthesis in red‐fleshed kiwifruit (<i>Actinidia chinensis</i>)

<jats:title>Summary</jats:title><jats:p>Much of the diversity of anthocyanins is due to the action of glycosyltransferases, which add sugar moieties to anthocyanidins. We identified two glycosyltransferases, <jats:italic>F3GT1</jats:italic> and <jats:italic>F3GGT1</jats:italic>, from red‐fleshed kiwifruit (<jats:italic>Actinidia chinensis</jats:italic>) that perform sequential glycosylation steps. Red‐fleshed genotypes of kiwifruit accumulate anthocyanins mainly in the form of cyanidin 3‐<jats:italic>O</jats:italic>‐xylo‐galactoside. Genes in the anthocyanin and flavonoid biosynthetic pathway were identified and shown to be expressed in fruit tissue. However, only the expression of the glycosyltransferase <jats:italic>F3GT1</jats:italic> was correlated with anthocyanin accumulation in red tissues. Recombinant enzyme assays <jats:italic>in vitro</jats:italic> and <jats:italic>in vivo</jats:italic> RNA interference (RNAi) demonstrated the role of <jats:italic>F3GT1</jats:italic> in the production of cyanidin 3‐<jats:italic>O</jats:italic>‐galactoside. <jats:italic>F3GGT1</jats:italic> was shown to further glycosylate the sugar moiety of the anthocyanins. This second glycosylation can affect the solubility and stability of the pigments and modify their colour. We show that recombinant <jats:italic>F3GGT1</jats:italic> can catalyse the addition of UDP‐xylose to cyanidin 3‐galactoside. While <jats:italic>F3GGT1</jats:italic> is responsible for the end‐product of the pathway, <jats:italic>F3GT1</jats:italic> is likely to be the key enzyme regulating the accumulation of anthocyanin in red‐fleshed kiwifruit varieties.</jats:p>