title: Identification of a Highly Specific Isoflavone 7-O-glucosyltransferase in the soybean (Glycine max (L.) Merr.).
abstract: Isoflavone conjugates [7-O-β-D-glucosides and 7-O-(6″-malonyl-β-D-glucosides) of daidzein and genistein] accumulate in soybean roots and serve as the stored precursors of isoflavones (aglycons), which play very important roles in the rhizobia-mediated nodulation of this plant. Thus far, the isoflavone 7-O-glucosyltransferase (GmIF7GT or GmUGT1) has been biochemically characterized and is believed to be involved in isoflavone conjugate biosynthesis. The soybean genome encodes many other glycosyltransferase homologs (GmUGTs) that are related to GmUGT1; however, their catalytic properties, substrate specificities, and role(s) in isoflavone conjugation are unknown. In this study, nine different GmUGT1-related GmUGT cDNAs were isolated; six of these cDNAs belonged to two distinct phylogenetic subgroups (A and B), and these six were functionally characterized. The results showed that GmUGT4, a representative of subgroup A, encoded a UGT that was highly specific for isoflavones showing kcat and kcat/Km values for daidzein of 5.89 ± 0.65 s(-1) and 2.91 × 10(5) s(-1)M(-1), respectively. Moreover, GmUGT4 was expressed in the roots (mainly in lateral roots) of the 7-day-old seedlings and seeds, both of which contained abundant amounts of isoflavone conjugates. By contrast, GmUGT1 and GmUGT7, which were subgroup B members, encoded enzymes with broad glucosyl-acceptor specificities and were mainly expressed in the aerial portions (cotyledons and hypocotyls) of the seedlings. In the present study, we proposed that the role of isoflavone glucosylation in a soybean plant is assigned to different GmUGT members in an organ/tissue-dependent manner. We also established the functional importance of GmUGT4 in the biosynthesis of isoflavone conjugates in lateral roots that make a major contribution to overall N2 fixation.
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-11, Sendai, Miyagi 980-8579, Japan.
authors.forename: Ayuta
authors.initials: A
authors.lastname: Funaki
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-11, Sendai, Miyagi 980-8579, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Waki
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-11, Sendai, Miyagi 980-8579, Japan Present address: Division of Novel Foods and Immunochemistry, National Institute of Health Sciences, Setagaya, Tokyo 158-8501, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Noguchi
authors.affiliation: Department of Integrative Genomics, Tohoku Medical Megabank Organization, Tohoku University, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8573, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Kawai
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-11, Sendai, Miyagi 980-8579, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamashita
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-11, Sendai, Miyagi 980-8579, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Takahashi
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-11, Sendai, Miyagi 980-8579, Japan nakayama@seika.che.tohoku.ac.jp.
authors.forename: Toru
authors.initials: T
authors.lastname: Nakayama
mesh_terms: D001483:Base Sequence; D018548:Cotyledon / Q000201:enzymology / Q000235:genetics; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005964:Glucosyltransferases / Q000235:genetics* / Q000378:metabolism; D018546:Hypocotyl / Q000201:enzymology / Q000235:genetics; D007529:Isoflavones / Q000378:metabolism*; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000201:enzymology / Q000235:genetics; D036226:Seedlings / Q000201:enzymology / Q000235:genetics; D012639:Seeds / Q000201:enzymology / Q000235:genetics; D017422:Sequence Analysis, DNA; D013025:Glycine max / Q000201:enzymology* / Q000235:genetics
chemical_list: D018076:DNA, Complementary; D018744:DNA, Plant; D007529:Isoflavones; D010940:Plant Proteins; C004742:daidzein; D005964:Glucosyltransferases
keywords: Glucosyltransferase; Glycine max (L.) Merr.; Isoflavone; Lateral roots; Soybean