Biosynthesis and antifungal activity of fungus-induced O-methylated flavonoids in maize |
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Authors: | Christiane Frster Vinzenz Handrick Yezhang Ding Yoko Nakamura Christian Paetz Bernd Schneider Gabriel Castro-Falcn Chambers C Hughes Katrin Luck Sowmya Poosapati Grit Kunert Alisa Huffaker Jonathan Gershenzon Eric A Schmelz Tobias G Kllner |
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Institution: | 1. Department of Biochemistry, Max Planck Institute for Chemical Ecology, Jena D-07745, Germany;2. Section of Cell and Developmental Biology, University of California, San Diego, California 92093-0380, USA;3. Research Group Biosynthesis/NMR, Max Planck Institute for Chemical Ecology, , Jena D-07745, Germany;4. Scripps Institution of Oceanography, University of California, San Diego, California 92093, USA |
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Abstract: | Fungal infection of grasses, including rice (Oryza sativa), sorghum (Sorghum bicolor), and barley (Hordeum vulgare), induces the formation and accumulation of flavonoid phytoalexins. In maize (Zea mays), however, investigators have emphasized benzoxazinoid and terpenoid phytoalexins, and comparatively little is known about flavonoid induction in response to pathogens. Here, we examined fungus-elicited flavonoid metabolism in maize and identified key biosynthetic enzymes involved in the formation of O-methylflavonoids. The predominant end products were identified as two tautomers of a 2-hydroxynaringenin-derived compound termed xilonenin, which significantly inhibited the growth of two maize pathogens, Fusarium graminearum and Fusarium verticillioides. Among the biosynthetic enzymes identified were two O-methyltransferases (OMTs), flavonoid OMT 2 (FOMT2), and FOMT4, which demonstrated distinct regiospecificity on a broad spectrum of flavonoid classes. In addition, a cytochrome P450 monooxygenase (CYP) in the CYP93G subfamily was found to serve as a flavanone 2-hydroxylase providing the substrate for FOMT2-catalyzed formation of xilonenin. In summary, maize produces a diverse blend of O-methylflavonoids with antifungal activity upon attack by a broad range of fungi.Upon fungal infection, maize produces a complex mixture of O-methylated flavonoids, which are biosynthesized by regiospecific O-methyltransferases and that contribute to the blend of defense-related specialized metabolites. |
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