title: Molecular analysis of herbivore-induced condensed tannin synthesis: cloning and expression of dihydroflavonol reductase from trembling aspen (Populus tremuloides).
abstract: 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.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Canada T6G 2E9.
authors.forename: Darren J
authors.initials: DJ
authors.lastname: Peters
authors.forename: C Peter
authors.initials: CP
authors.lastname: Constabel
mesh_terms: D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D004790:Enzyme Induction; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D047348:Hydrolyzable Tannins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009036:Moths / Q000502:physiology*; D010935:Plant Diseases / Q000235:genetics / Q000469:parasitology; D032107:Populus / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism / Q000469:parasitology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
chemical_list: D047348:Hydrolyzable Tannins; D000429:Alcohol Oxidoreductases