RUI: Sphingolipid Metabolism in Plants

这个项目研究植物中鞘脂合成的各个方面。其目的是从长链碱基形成的角度表征鞘磷脂的合成及其调节；表征修饰鞘糖脂的长链碱基和脂肪酸组成的酶步骤，并研究参与形成主要植物鞘糖脂的葡萄糖神经酰胺的物种之间的代谢相互关系；以及评估葡萄糖神经酰胺的降解和周转。以植物细胞悬浮培养和黑麦幼苗为实验系统。这两个植物系统具有不同的葡萄糖神经酰胺分子种类组成。植物细胞悬浮培养的使用促进了对鞘脂合成调节的体内详细研究，并补充了旨在表征无细胞系统中选定的酶步骤的研究。放射性标记的前体在体外或体内供应，并在分离后通过薄层色谱和高效液相测定鞘磷脂产品中的掺入。在神经鞘脂代谢因发育或对环境因素或生化调节剂的反应而发生改变的条件下，研究调节的各个方面。预计这些研究是植物细胞中的第一个此类研究，将提供关于鞘磷脂代谢的细胞调控的信息。目前的教条认为，植物和动物细胞通过改变其细胞膜的脂类成分来应对温度胁迫。几乎没有实验证据来验证这一假设。这个项目提供了关于一类新发现的脂类的新信息，以及当植物暴露在低温下时，它们的类型和数量是如何变化的。关于植物类脂的基本新信息将会产生。

This project examines aspects of sphingolipid synthesis in plants. The objectives are to characterize sphingolipid synthesis and its regulation at the point of long chain base formation; to characterize the enzymatic steps involved in modifying long chain base and fatty acid components of sphingolipids and investigate the metabolic interrelationships of species involved in the formation of glucosylceramide, the predominant plant sphingolipid; and to assess degradation and turnover of glucosylceramide. Plant cell suspension cultures and rye seedlings are used as experimental systems. These two plant systems have diverse glucosylceramide molecular species compositions. The use of plant cell suspension cultures facilitates detailed in vivo studies of the regulation of sphingolipid synthesis and complements studies aimed at characterizing selected enzymatic steps in cell-free systems. Radiolabeled precursors are supplied in vitro or in vivo and the incorporation into sphingolipid products determined following separation by TLC and HPLC. Aspects of regulation are investigated under conditions in which sphingolipid metabolism is altered as a consequence of development or in response to environmental factors or biochemical regulators. It is anticipated that these studies, the first of their kind in plant cells, will provide information on the cellular regulation of sphingolipid metabolism. Current dogma holds that plant and animal cells respond to temperature stress by altering the lipid composition of their membranes. Very little experimental evidence has been generated to test this hypothesis. This project provides new information on a newly discovered class of lipids and how they change in type and amount when plants are exposed to low temperature. Fundamental new information on plant lipids will result.