Underground Metabolism and Development: Polyacetylene Biosynthesis in Asteraceae Roots

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The studies proposed here focus on the physiology and biochemistry of the polyacetylenes, fatty acid derivatives which are present mainly in the roots of Asteraceae. Polyacetylenes show a wide range of biological activities (nematicidal, fungicidal and antiviral), and may play an important role in protecting plant roots against challenge from soil pathogens. By transformation with Agrobacterium rhizogenes, we have obtained "hairy roots" cultures of five genera in the Asteraceae. These fast growing roots have shown stable, long-term production of root polyacetylenes and are therefore an ideal experimental system. Using precursor label incorporation, HPLC and GC-MS analysis, and cell-free assays, we propose to establish the pathway for polyacetylene biosynthesis in root cultures. Fungal and nematodal bioassays have been developed, and will be used to monitor the biological activity of the polyacetylenes produced in rootcultures. The de novo formation of polyacetylenes in root cultures can be induced by treatment with fungal elicitors. This approach will be used to identiy the rate-limiting enzymatic steps in polyacetylene biosynthesis, and test the proposed involvement of lipoxygenase. Although roots normally grow heterotrophically both in isolated culture and "in planta", we have found that they can also be grown photosynthetically and photoautotrophically. We will also study the quantitative and qualitative effects of photosynthesis and photoautotrophy on root polyacetylene patterns. ***//