Lipid Metabolism and Photosynthesis in Fatty Acid Mutants ofArabidopsis

叶绿体的酰基脂含有高比例的三烯脂肪酸。由于这一特征在高等植物中普遍存在，因此推测叶绿体膜的脂肪酸组成对维持光合作用功能是重要的。然而，对多不饱和脂肪酸合成的酶学和调控知之甚少，目前还没有一个被接受的模型来确切地说明光合作用是如何依赖于高度不饱和的膜的。本课题组的主要工作是筛选出一系列叶片脂肪酸组成发生特异性变化的拟南芥突变体，为研究植物脂肪代谢和膜脂组成的生理意义提供了新的手段。这项建议描述了对新分离的突变株和通过交叉突变系产生的双突变株的生物化学进行表征的实验。该项目的这一方面将包括分析脂肪酸合成的酶，以及活体标记实验和分析单个脂质和亚细胞部分的脂肪酸组成。最极端的双重突变体不能自养生长，但许多突变只会影响植物在低温下的生长和发育。因此，不同突变体的光合作用将在一系列环境条件下使用非侵入性荧光和光吸收技术进行分析，这些技术可以用于完整的植物。这些实验将提供一个清晰的图景，确切地说明在温带植物通常遇到的不同生长条件下，类囊体脂成分如何影响光合作用。这项工作将导致对脂肪代谢和光合作用的更好的理解，这是修改这些过程以提高植物生产力的重要先决条件。//

The acyl lipids of chloroplasts contain characteristically high proportions of trienoic fatty acids. Because this feature is universal among higher plants, it has been inferred that the fatty acid composition of chloroplast membranes is important for maintaining photosynthetic function. However, the enzymology and regulation of polyunsaturated fatty acid synthesis are poorly understood, and there is at present no accepted model of exactly how photosynthesis might be dependent on a highly unsaturated membrane. The principal investigator has isolated a series of Arabidopsis mutants with specific alterations in leaf fatty acid composition and these have provided a novel means to study both plant lipid metabolism and the physiological significance of membrane lipid composition. This proposal describes experiments to characterize the biochemistry of newly isolated mutants, and of double mutants produced by crossing mutant lines. This aspect of the project will involve assaying enzymes of fatty acid synthesis as well as in vivo labeling experiments and analysis of the fatty acid compositions of individual lipids and subcellular fractions. The most extreme double mutants are unable to grow autotrophically, but many of the mutations only affect growth and development of the plants at low temperatures. For this reason, photosynthesis in the different mutants will be analyzed under a range of environmental conditions using non-invasive fluorescence and light absorption techniques which can be used on intact plants. These experiments would provide a clear picture of exactly how photosynthesis is affected by thylakoid lipid composition under the different growth conditions normally encountered by temperate plants. The improved understanding of lipid metabolism and photosynthesis that will result from the work are important prerequisites to modifying these processes for increase plant productivity. //