Molecular analysis of herbivore-induced condensed tannin synthesis: cloning and expression of dihydroflavonol reductase from trembling aspen (Populus tremuloides)

Authors

  • Darren J. Peters,

    1. Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9, and
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  • C. Peter Constabel

    Corresponding author
    1. Center for Forest Biology & Biology Department, University of Victoria, PO Box 3020, STN CSC, Victoria, British Columbia, Canada V8W 3N5
      * For correspondence (fax +1 250 721 6611; e-mail cpc@uvic.ca).
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* For correspondence (fax +1 250 721 6611; e-mail cpc@uvic.ca).

Summary

In order to study condensed tannin synthesis and its induction by herbivory, a dihydroflavonol reductase (DFR) cDNA was isolated from trembling aspen (Populus tremuloides). Bacterial overexpression demonstrated that this cDNA encodes a functional DFR enzyme, and Southern analysis revealed that DFR likely is a single-copy gene in the aspen genome. Aspen plants that were mechanically wounded showed a dramatic increase in DFR expression after 24 h in both wounded leaves and unwounded leaves on wounded trees. Feeding by forest tent caterpillar (Malacosoma disstria) and satin moth (Leucoma salicis) larvae, and treatment with methyl jasmonate, all strongly induced DFR expression. DFR enzyme activity was also induced in wounded aspen leaves, and phytochemical assays revealed that condensed tannin concentrations significantly increased in wounded and systemic leaves. The expression of other genes involved in the phenylpropanoid pathway were also induced by wounding. Our findings suggest that the induction of condensed tannins, compounds known to be important for defense against herbivores, is mediated by increased expression of DFR and other phenylpropanoid genes.

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