title: Glucosylation of flavonoids in petals of Petunia hybrida.
abstract: During the biosynthesis of anthocyanins in Petunia hybrida, the 3-hydroxyl group is glucosylated. Their supposed biosynthetic precursors, the dihydroflavonols, are glucosylated at the 7 or 4' positions. The question arose of whether these glucosides or the aglucones act as a substrate in anthocyanin synthesis. Using isolated flower buds of white flowering mutants that were blocked in an earlier step of biosynthesis, it was found that anthocyanin-3-glucosides and dihydroquercetin-7-glucoside were synthesized if dihydroquercetin, dihydroquercetin-7-glucoside, or dihydroquercetin-4'-glucoside were used as precursors in these experiments. Intracellular dihydroquercetin-glucosides were not used as a substrate for anthocyanin synthesis. The results are explained by deglucosylation of dihydroquercetin-glucosides during uptake by isolated flower limbs. Dihydroquercetin-7-glucoside, formed intracellularly, is not available as a precursor for anthocyanins. We conclude that the aglucone form of dihydroquercetin acts as a substrate in anthocyanin biosynthesis.
authors.affiliation: Departments of Genetics and Plantphysiology, Section "Biosynthesis of Flavonoids", University of Amsterdam, Kruislaan 318, NL-1098 SM, Amsterdam, The Netherlands.
authors.forename: A W
authors.initials: AW
authors.lastname: Schram
authors.forename: A W
authors.initials: AW
authors.lastname: Timmerman
authors.forename: P
authors.initials: P
authors.lastname: de Vlaming
authors.forename: L M
authors.initials: LM
authors.lastname: Jonsson
authors.forename: G J
authors.initials: GJ
authors.lastname: Bennink