Redirection of Flavonoid Biosynthesis through the Down-Regulation of an Anthocyanidin Glucosyltransferase in Ripening Strawberry Fruit

• DOI: 10.1104/pp.107.114280
• Publication Date: 2008-02-08T01:58:25Z
• Authors: Markus Griesser; Thomas Hoffmann; Mari Luz Bellido; Carlo Rosati; Barbara Fink; Robert Kurtzer; Asaph Aharoni; Juan Muñoz-Blanco; Wilfried Schwab
• Keywords: Anthocyanidins; Pelargonidin; Glucosyltransferases; Chromoplast; Flavonoid Biosynthesis; Plant Physiology; Flavonols; Anthocyanidins

Strawberry (Fragaria x ananassa) fruit contains several anthocyanins that give the ripe fruits their attractive red color. The enzyme catalyzes formation of first stable intermediate in anthocyanin pathway is anthocyanidin-3-O-glucosyltransferase. A putative glycosyltransferase sequence (FaGT1) was cloned from a strawberry cDNA library and recombinant FaGT1 transferred UDP-glucose to anthocyanidins and, lesser extent, flavonols, generating respective 3-O-glucosides. Quantitative polymerase chain reaction revealed transcripts were almost undetectable green fruits, but gene expression increased dramatically both turning fruit, corresponding closely accumulation during ripening. associated negatively regulated by auxin. To elucidate planta function FaGT1, Agrobacterium tumefaciens cells harboring an intron-hairpin construct partial injected into midsized ripening fruits. In about one-third this led significant down-regulation transcript levels corresponded reduced concentrations pigments contrast, epiafzelechin--formed anthocyanidin reductase (ANR) pelargonidin--were identified FaGT1-silenced indicating competition FaANR for common substrate. Thus, represents important branching-point because it channeling flavonoid anthocyanins. These results demonstrate method redirect biosynthesis flavan-3-ol production increase bioactive natural products or modify plant tissues.