Underground Metabolism and Development: Polyacetylene Biosynthesis in Asteraceae Roots

本文提出的研究重点是主要存在于菊科植物根部的脂肪酸衍生物--聚乙炔的生理和生化。聚乙炔具有广泛的生物活性(杀线虫、杀菌和抗病毒)，在保护植物根系免受土壤病原体侵袭方面发挥着重要作用。通过发根农杆菌转化，获得菊科植物5个属的毛状根培养物。这些快速生长的根显示出稳定、长期的根聚乙炔生产，因此是一个理想的实验系统。利用前体标记掺入、高效液相色谱和GC-MS分析，以及无细胞分析，我们建议建立根培养物中多乙炔生物合成的途径。真菌和线虫的生物测定已经开发出来，并将用于监测在根培养中产生的聚乙炔的生物活性。根培养物中聚乙炔的从头形成可以通过真菌诱导子的处理来诱导。这一方法将被用来识别聚乙炔生物合成中的限速酶步骤，并测试脂肪氧合酶的参与。虽然根通常在隔离培养和植物中异养生长，但我们发现它们也可以在光合作用和光自养条件下生长。我们还将研究光合作用和光自养对根部聚乙炔模式的定量和定性影响。*//

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. ***//