title: UGT73C6 and UGT78D1, glycosyltransferases involved in flavonol glycoside biosynthesis in Arabidopsis thaliana.
abstract: Flavonol glycosides constitute one of the most prominent plant natural product classes that accumulate in the model plant Arabidopsis thaliana. To date there are no reports of functionally characterized flavonoid glycosyltransferases in Arabidopsis, despite intensive research efforts aimed at both flavonoids and Arabidopsis. In this study, flavonol glycosyltransferases were considered in a functional genomics approach aimed at revealing genes involved in determining the flavonol-glycoside profile. Candidate glycosyltransferase-encoding genes were selected based on homology to other known flavonoid glycosyltransferases and two T-DNA knockout lines lacking flavonol-3-O-rhamnoside-7-O-rhamnosides (ugt78D1) and quercetin-3-O-rhamnoside-7-O-glucoside (ugt73C6 and ugt78D1) were identified. To confirm the in planta results, cDNAs encoding both UGT78D1 and UGT73C6 were expressed in vitro and analyzed for their qualitative substrate specificity. UGT78D1 catalyzed the transfer of rhamnose from UDP-rhamnose to the 3-OH position of quercetin and kaempferol, whereas UGT73C6 catalyzed the transfer of glucose from UDP-glucose to the 7-OH position of kaempferol-3-O-rhamnoside and quercetin-3-O-rhamnoside, respectively. The present results suggest that UGT78D1 and UGT73C6 should be classified as UDP-rhamnose:flavonol-3-Orhamnosyltransferase and UDP-glucose:flavonol-3-O-glycoside-7-O-glucosyltransferase, respectively.
authors.affiliation: Department of Molecular Biology and Biotechnology, Graduate school of Pharmaceutical Sciences, Chiba University, Core Research for Evolutional Science and Technology of Japan Science and Technology Corporation (JST), Chiba 263-8522, Japan.
authors.forename: Patrik
authors.initials: P
authors.lastname: Jones
authors.forename: Burkhard
authors.initials: B
authors.lastname: Messner
authors.forename: Jun-Ichiro
authors.initials: J
authors.lastname: Nakajima
authors.forename: Anton R
authors.initials: AR
authors.lastname: Schäffner
authors.forename: Kazuki
authors.initials: K
authors.lastname: Saito
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D044948:Flavonols / Q000096:biosynthesis*; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism*; D006027:Glycosides / Q000096:biosynthesis*; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism*; D044949:Kaempferols / Q000378:metabolism; D009154:Mutation; D011794:Quercetin / Q000378:metabolism; D011994:Recombinant Proteins; D012210:Rhamnose / Q000378:metabolism; D013379:Substrate Specificity; D014532:Uridine Diphosphate Glucose / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D018076:DNA, Complementary; D044948:Flavonols; D006027:Glycosides; D044949:Kaempferols; D011994:Recombinant Proteins; C006552:kaempferol; D011794:Quercetin; D016695:Glycosyltransferases; D005964:Glucosyltransferases; C480036:UGT73C6 protein, Arabidopsis; C480037:UGT78D1 protein, Arabidopsis; D005947:Glucose; D012210:Rhamnose; D014532:Uridine Diphosphate Glucose