Regulation of fatty acid desaturation in Arabidopsis

该项目的目的是阐明调节膜和储存脂质的不饱和程度的分子机制。我们将通过测量发育阶段和环境条件对最近从拟南芥中分离到的几个编码脂肪酸去饱和酶的基因表达的影响来解决这个问题。在酶的直接激活或失活水平上起作用的调节机制的存在将通过测量转基因植物中脂质组成的影响来检验，这些植物由于克隆的去饱和酶基因的过度表达而含有高于正常水平的去饱和酶活性。细胞内脂质去饱和的空间组织将通过免疫金电镜用抗去饱和酶抗体来定位酶。最后，我们将基于拟南芥突变体的全面收集，尝试通过基于图谱的克隆方法分离其他几种去饱和酶的基因。植物脂肪酸提供了人类饮食中约三分之一的卡路里，并被广泛用于从合成尼龙到化妆品的各种技术产品中。此外，许多植物耐受极端温度的能力被认为是由植物膜的脂肪酸组成控制的。本文提出的实验旨在提供调控植物脂肪酸组成的因素的详细信息。这一信息可能有助于对植物脂肪酸组成进行基因改造，从而生产出具有有利膳食品质、扩大技术用途或增强耐极端温度能力的食用油。

The goal of the project is to elucidate the molecular mechanisms which regulate the degree of unsaturation of membrane and storage lipids. We will address this question by measuring the effect of variation in developmental stage and environmental conditions on the expression of several recently isolated genes encoding fatty acid desaturases from the plant Arabidopsis thaliana. The existence of regulatory mechanisms which act at the level of direct enzyme activation or deactivation will be examined by measuring the effects on lipid composition in transgenic plants which contain higher than normal levels of desaturase activity due to overexpression of cloned desaturase genes. The spatial organization of lipid desaturation within cells will be elucidated using anti-desaturase antibodies to localize the enzymes by immunogold electron microscopy. Finally, we will attempt to isolate genes for several additional desaturases by map-based cloning methods based on the availability of a comprehensive collection of mutants of Arabidopsis. %%% Plant fatty acids provide about one third of the calories in human diets and are also used for a wide variety of technical products raging from synthesis of nylon to cosmetics. In addition, the ability of many plants to withstand exposure to temperature extremes is thought to be controlled by the fatty acid composition of plant membranes. The experiments proposed here are designed to provided detailed information about the factors which regulate plant fatty acid composition. This information may be useful in permitting genetic modification of the fatty acid composition of plants so that they produce edible oils with advantageous dietary qualities, expanded technical uses or enhanced ability to withstand temperature extremes.