Fig. 4.

Generalized anthocyanin biosynthetic pathway (adapted from Holton and Cornish 1995), illustrating the various chemical reactions that DFR can, in principle, catalyze en route to producing red (pelargonidin-based), pink (cyanidin-based), and purple (delphinidin-based) anthocyanin pigments. Enzyme abbreviations: CHS chalcone synthase, CHI chalcone isomerase, F3H flavanone 3-hydroxylase, F3′H flavonoid 3′-hydroxylase, F3′5′H flavonoid 3′,5′-hydroxylase, DFR dihydroflavonol 4-reductase, ANS anthocyanidin synthase, GT UDP-glucose anthocyanidin 3-O-glucosyltransferase, RT UDP-rhamnose anthocyanidin-3-glucoside rhamnosyltransferase