Abstract
The inducible metabolites were analyzed in barley leaves inoculated with Bipolaris sorokiniana, the causal agent of spot blotch of barley. HPLC analysis revealed that B. sorokiniana-infected leaves accumulated 4 hydrophilic compounds. They were purified by ODS column chromatography and preparative HPLC. Spectroscopic analyses revealed that they were tyramine (1), 3-(2-aminoethyl)-3-hydroxyindolin-2-one (2), serotonin (3), and 5,5'-dihydroxy-2,4'-bitryptamine (4). Among these, 2 and 4 have not been reported as natural products. They showed antifungal activity in an assay of inhibition of B. sorokiniana conidia germination, suggesting that they play a role in the chemical defense of barley as phytoalexins. The accumulation of 1-4 was examined also in the leaves of rice and foxtail millet. Rice leaves accumulated 2, 3, and 4, whereas foxtail millet leaves accumulated 3 and 4 in response to pathogen attack, suggesting the generality of accumulation of 3 and 4 in the Poaceae species.
Keywords:
Bipolaris sorokiniana; Poaceae; barley; dimer; serotonin.
MeSH terms
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Antifungal Agents / immunology*
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Antifungal Agents / metabolism
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Antifungal Agents / pharmacology
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Chromatography, High Pressure Liquid
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Hordeum / immunology*
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Hordeum / metabolism
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Hordeum / microbiology
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Hydrophobic and Hydrophilic Interactions
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Indoles / immunology
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Indoles / metabolism
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Indoles / pharmacology
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Oryza / immunology
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Oryza / metabolism
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Oryza / microbiology
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Phytoalexins
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Plant Diseases / immunology*
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Plant Diseases / microbiology
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Plant Immunity
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Plant Leaves / immunology
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Plant Leaves / metabolism
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Plant Leaves / microbiology
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Saccharomycetales / drug effects*
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Saccharomycetales / pathogenicity
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Saccharomycetales / physiology
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Serotonin / biosynthesis
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Serotonin / immunology
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Serotonin / pharmacology
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Sesquiterpenes / immunology*
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Sesquiterpenes / metabolism
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Sesquiterpenes / pharmacology
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Setaria Plant / immunology
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Setaria Plant / metabolism
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Setaria Plant / microbiology
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Species Specificity
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Spores, Fungal / drug effects*
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Spores, Fungal / pathogenicity
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Spores, Fungal / physiology
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Tryptamines / biosynthesis
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Tryptamines / immunology
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Tryptamines / pharmacology
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Tyramine / biosynthesis
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Tyramine / immunology
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Tyramine / pharmacology
Substances
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Antifungal Agents
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Indoles
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Sesquiterpenes
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Tryptamines
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Serotonin
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Tyramine
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Phytoalexins