Glycosyltransferases from Oat (Avena) Implicated in the Acylation of Avenacins

Amorn Owatworakit, Belinda Townsend, Thomas Louveau, Helen Jenner, Martin Rejzek, Richard K. Hughes, Gerhard Saalbach, Xiaoquan Qi, Saleha Bakht, Abhijeet Deb Roy, Sam T. Mugford, Rebecca Jane Miriam Goss, Robert Andrew Field, Anne Osbourn*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)3696-3704
Number of pages9
JournalJournal of Biological Chemistry
Volume288
Issue number6
Early online date20 Dec 2012
DOIs
Publication statusPublished - 8 Feb 2013

Keywords

  • DISEASE RESISTANCE
  • UGT74F2 GLUCOSYLTRANSFERASE
  • SERINE CARBOXYPEPTIDASE
  • CARBOXYPEPTIDASE-LIKE PROTEIN
  • SALICYLIC-ACID
  • PLANTS
  • EVOLUTION
  • ARABIDOPSIS-THALIANA
  • OXIDOSQUALENE CYCLASES
  • SECONDARY METABOLISM

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