A Conifer UDP-Sugar Dependent Glycosyltransferase Contributes to Acetophenone Metabolism and Defense against Insects

  • Plant Physiol. 2017 Oct;175(2):641-651. doi: 10.1104/pp.17.00611.
Melissa H Mageroy  1  2 ,  Sharon Jancsik  1 ,  Macaire Man Saint Yuen  1 ,  Michael Fischer  3 ,  Stephen G Withers  1  3 ,  Christian Paetz  4 ,  Bernd Schneider  4 ,  John Mackay  5  6 ,  Joerg Bohlmann  7  8  9
Affiliations
  • 1. Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada.
  • 2. Norwegian Institute for Bioeconomy Research, NO-1430 As, Norway.
  • 3. Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T1Z1, Canada.
  • 4. Max Planck Institute for Chemical Ecology, D-07745 Jena, Germany.
  • 5. Department of Wood and Forest Sciences, Université Laval, Quebec City, Quebec G1V0A6, Canada.
  • 6. Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom.
  • 7. Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada [email protected].
  • 8. Department of Forest Sciences, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada.
  • 9. Department of Botany, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada.
PMID: 28794260 DOI: 10.1104/pp.17.00611
Abstract

Acetophenones are phenolic compounds involved in the resistance of white spruce (Picea glauca) against spruce budworm (Choristoneura fumiferiana), a major forest pest in North America. The acetophenones pungenol and piceol commonly accumulate in spruce foliage in the form of the corresponding glycosides, pungenin and picein. These glycosides appear to be inactive against the insect but can be cleaved by a spruce β-glucosidase, PgβGLU-1, which releases the active aglycons. The reverse glycosylation reaction was hypothesized to involve a family 1 UDP-sugar dependent Glycosyltransferase (UGT) to facilitate acetophenone accumulation in the plant. Metabolite and transcriptome profiling over a developmental time course of white spruce bud burst and shoot growth revealed two UGTs, PgUGT5 and PgUGT5b, that glycosylate pungenol. Recombinant PgUGT5b enzyme produced mostly pungenin, while PgUGT5 produced mostly isopungenin. Both UGTs also were active in vitro on select Flavonoids. However, the context of transcript and metabolite accumulation did not support a biological role in flavonoid metabolism but correlated with the formation of pungenin in growing shoots. Transcript levels of PgUGT5b were higher than those of PgUGT5 in needles across different genotypes of white spruce. These results support a role of PgUGT5b in the biosynthesis of the glycosylated acetophenone pungenin in white spruce.

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