title: Glycosyltransferases from oat (Avena) implicated in the acylation of avenacins.
abstract: Plants produce a huge array of specialized metabolites that have important functions in defense against biotic and abiotic stresses. Many of these compounds are glycosylated by family 1 glycosyltransferases (GTs). Oats (Avena spp.) make root-derived antimicrobial triterpenes (avenacins) that provide protection against soil-borne diseases. The ability to synthesize avenacins has evolved since the divergence of oats from other cereals and grasses. The major avenacin, A-1, is acylated with N-methylanthranilic acid. Previously, we have cloned and characterized three genes for avenacin synthesis (for the triterpene synthase SAD1, a triterpene-modifying cytochrome P450 SAD2, and the serine carboxypeptidase-like acyl transferase SAD7), which form part of a biosynthetic gene cluster. Here, we identify a fourth member of this gene cluster encoding a GT belonging to clade L of family 1 (UGT74H5), and show that this enzyme is an N-methylanthranilic acid O-glucosyltransferase implicated in the synthesis of avenacin A-1. Two other closely related family 1 GTs (UGT74H6 and UGT74H7) are also expressed in oat roots. One of these (UGT74H6) is able to glucosylate both N-methylanthranilic acid and benzoic acid, whereas the function of the other (UGT74H7) remains unknown. Our investigations indicate that UGT74H5 is likely to be key for the generation of the activated acyl donor used by SAD7 in the synthesis of the major avenacin, A-1, whereas UGT74H6 may contribute to the synthesis of other forms of avenacin that are acylated with benzoic acid.
authors.affiliation: Department of Metabolic Biology, The John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom.
authors.forename: Amorn
authors.initials: A
authors.lastname: Owatworakit
authors.forename: Belinda
authors.initials: B
authors.lastname: Townsend
authors.forename: Thomas
authors.initials: T
authors.lastname: Louveau
authors.forename: Helen
authors.initials: H
authors.lastname: Jenner
authors.forename: Martin
authors.initials: M
authors.lastname: Rejzek
authors.forename: Richard K
authors.initials: RK
authors.lastname: Hughes
authors.forename: Gerhard
authors.initials: G
authors.lastname: Saalbach
authors.forename: Xiaoquan
authors.initials: X
authors.lastname: Qi
authors.forename: Saleha
authors.initials: S
authors.lastname: Bakht
authors.forename: Abhijeet Deb
authors.initials: AD
authors.lastname: Roy
authors.forename: Sam T
authors.initials: ST
authors.lastname: Mugford
authors.forename: Rebecca J M
authors.initials: RJ
authors.lastname: Goss
authors.forename: Robert A
authors.initials: RA
authors.lastname: Field
authors.forename: Anne
authors.initials: A
authors.lastname: Osbourn
mesh_terms: D000215:Acylation / Q000502:physiology; D018554:Avena / Q000201:enzymology* / Q000235:genetics; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D016695:Glycosyltransferases / Q000096:biosynthesis* / Q000235:genetics; D005810:Multigene Family / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000201:enzymology* / Q000235:genetics; D012503:Saponins / Q000235:genetics / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D012503:Saponins; D003577:Cytochrome P-450 Enzyme System; C091460:avenacin A 1; D016695:Glycosyltransferases