title: Purification, molecular cloning and functional characterization of flavonoid C-glucosyltransferases from Fagopyrum esculentum M. (buckwheat) cotyledon.
abstract: C-Glycosides are characterized by their C-C bonds in which the anomeric carbon of the sugar moieties is directly bound to the carbon atom of aglycon. C-Glycosides are remarkably stable, as their C-C bonds are resistant to glycosidase or acid hydrolysis. A variety of plant species are known to accumulate C-glycosylflavonoids; however, the genes encoding for enzymes that catalyze C-glycosylation of flavonoids have been identified only from Oryza sativa (rice) and Zea mays (maize), and have not been identified from dicot plants. In this study, we identified the C-glucosyltransferase gene from the dicot plant Fagopyrum esculentum M. (buckwheat). We purified two isozymes from buckwheat seedlings that catalyze C-glucosylation of 2-hydroxyflavanones, which are expressed specifically in the cotyledon during seed germination. Following purification we isolated the cDNA corresponding to each isozyme [FeCGTa (UGT708C1) and FeCGTb (UGT708C2)]. When expressed in Escherichia coli, both proteins demonstrated C-glucosylation activity towards 2-hydroxyflavanones, dihydrochalcone, trihydroxyacetophenones and other related compounds with chemical structures similar to 2',4',6'-trihydroxyacetophenone. Molecular phylogenetic analysis of plant glycosyltransferases shows that flavonoid C-glycosyltransferases form a different clade with other functionally analyzed plant glycosyltransferases.
authors.affiliation: Division of Applied Biology, Faculty of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda, 386-8567, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Nagatomo
authors.forename: Shiori
authors.initials: S
authors.lastname: Usui
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Ito
authors.forename: Akira
authors.initials: A
authors.lastname: Kato
authors.forename: Makoto
authors.initials: M
authors.lastname: Shimosaka
authors.forename: Goro
authors.initials: G
authors.lastname: Taguchi
mesh_terms: D001483:Base Sequence; D003001:Cloning, Molecular; D018548:Cotyledon / Q000201:enzymology / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D019612:Fagopyrum / Q000201:enzymology* / Q000235:genetics; D005419:Flavonoids / Q000378:metabolism*; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D036226:Seedlings / Q000201:enzymology / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D018076:DNA, Complementary; D005419:Flavonoids; D010940:Plant Proteins; D005964:Glucosyltransferases
keywords: 2-hydroxyflavanone; Fagopyrum esculentum; buckwheat; cotyledon; flavonoid C-glucosyltransferase; germination; vitexin