Underground Metabolism and Development: Polyacetylene Biosynthesis in Asteraceae Roots

本文主要对菊科植物中主要存在的聚乙炔类脂肪酸衍生物的生理生化特性进行了研究。聚乙炔具有广泛的生物活性（杀线虫、杀真菌和抗病毒），可能在保护植物根系免受土壤病原体侵袭方面发挥重要作用。通过根农杆菌的转化，我们获得了菊科5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。通过前体标记整合、HPLC和GC-MS分析以及无细胞分析，我们提出在根培养中建立聚乙炔生物合成途径。真菌和线虫的生物测定已经开发出来，并将用于监测根培养中产生的聚乙炔的生物活性。用真菌激发子处理可以诱导根培养物中聚乙炔的重新形成。该方法将用于确定聚乙炔生物合成中的限速酶步骤，并测试脂氧合酶的提议参与。虽然根通常在离体培养和“植物”中都是异养生长，但我们发现它们也可以进行光合和光自养生长。我们还将研究光合作用和光自养对根聚乙炔形态的定量和定性影响。* * * / /

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. ***//