Mechanisms of Lipid Trafficking between the Endoplasmic Reticulum and the Chloroplast

内质网和叶绿体之间的脂质运输机制

• 批准号: 0741395
• 负责人: Christoph Benning
• 金额: $ 54.68万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-05-01 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0741395&HistoricalAwards=false
• 关键词: Mechanisms; Lipid; Trafficking; between; Endoplasmic

Intellectual Merit: Compartmentation into organelles is a signature trait of all eukaryotic cells and depends on biological membranes containing glycerolipids. Interorganelle lipid trafficking is essential, because different organelles cooperate in the biosynthesis of lipid precursors required for the assembly of specific subcellular membranes. A prominent example is the formation of the photosynthetic thylakoid membranes in plant chloroplasts. Galactoglycerolipids are the most abundant lipid components of these membranes and their biosynthesis serves as a paradigm for the study of lipid transfer from the endoplasmic reticulum (ER) to the chloroplast. Long-term, the genetic and biochemical analysis of this process is expected to provide a mechanistic understanding of interorganelle lipid trafficking phenomena in plants and other organisms. A collection of 25 Arabidopsis mutants is hypothesized to be affected in different aspects of ER-toplastid lipid trafficking. Common to these mutants is a complex, but robust lipid phenotype, the accumulation of oligogalactoglycerolipids giving rise to the trigalactosyldiacylglycerol (tgd) mutant designation. Of the four TGD loci identified at this time, TGD1, TGD2, and TGD3 encode the permease, the substrate-binding protein, and the ATPase subunits of a putative ABC transporter complex in the inner chloroplast envelope membrane. Several lines of indirect evidence suggest that the TGD123 complex mediates the transfer of phosphatidic acid from the outer envelope to the inside of the inner envelope membrane, where it is processed into the diacylglycerol precursor for galactoglycerolipid biosynthesis. The recently identified TGD4 locus encodes a novel cytosolic non-intrinsic membrane protein, which appears to be associated with the ER. It is hypothesized that the TGD4 protein is directly involved in the transfer of lipid precursors from the ER to the outer chloroplast envelope, possibly by mediating the formation of direct contact zones between these two membranes. Three specific aims will be pursued: 1.The biochemical and molecular function of the TGD4 protein will be determined. 2. Uncharacterized tgd loci present in the mutant collection will be mapped and characterized largely by undergraduate students. 3. The working hypothesis for the existence and function of the proposed TGD123 phosphatidic acid transport complex will be tested. Broader Impacts: Aside from the scientific impacts mentioned, appropriate training opportunities will be provided for graduate and undergraduate students, as well as postdoctoral researchers. The continuing mapping of tgd loci under aim 2 involves undergraduate students supervised by senior researchers. Genetic mapping in Arabidopsis is based on mature technology and established procedures. However, it is intellectually challenging and enables the training of novices in fundamental lab skills. The procedures can be divided into small tasks fitting with a student's class schedule. Students participate in weekly lab meetings and give annual presentations on their work at regional meetings and during on-campus events. Undergraduate students are regularly included as coauthors on publications. In addition, the project will participate in a summer training program in Plant Genomics that was recently implemented at MSU (www.plantgenomics.msu.edu).

智力优势：细胞器的区室化是所有真核细胞的标志性特征，并且依赖于含有甘油脂的生物膜。细胞器间的脂质运输是必不可少的，因为不同的细胞器在组装特定亚细胞膜所需的脂质前体的生物合成中合作。一个突出的例子是植物叶绿体中光合作用类囊体膜的形成。半乳糖甘油脂是这些膜中最丰富的脂质成分，它们的生物合成是研究脂质从内质网（ER）转移到叶绿体的范例。从长远来看，这一过程的遗传和生物化学分析，预计将提供一个机械的理解细胞器间的脂质运输现象在植物和其他生物体。假设25个拟南芥突变体的集合在ER-质体脂质运输的不同方面受到影响。这些突变体的共同点是复杂但稳定的脂质表型，寡聚半乳糖甘油脂的积累导致三半乳糖基二酰甘油（tgd）突变体命名。在这个时候确定的四个TGD位点，TGD 1，TGD 2，和TGD 3编码的通透酶，底物结合蛋白，和ATP酶亚基的一个假定的ABC转运复合体的内叶绿体被膜。几条间接证据表明，TGD 123复合物介导磷脂酸从外被膜转移到内被膜内部，在那里它被加工成用于半乳甘油脂生物合成的二酰基甘油前体。最近发现的TGD 4基因座编码一种新的胞质非内在膜蛋白，这似乎是与ER。据推测，TGD 4蛋白直接参与脂质前体从内质网转移到外叶绿体包膜，可能是通过介导这两个膜之间的直接接触区的形成。本研究的主要目的有三：1.研究TGD 4蛋白的生物化学和分子生物学功能。2.突变体中未鉴定的tgd基因座将主要由本科生进行定位和鉴定。3.将检验拟定TGD 123磷脂酸转运复合物的存在和功能的工作假设。更广泛的影响：除了上述科学影响外，还将为研究生和本科生以及博士后研究人员提供适当的培训机会。根据aim 2，继续绘制tgd基因座涉及由资深研究人员指导的本科生。拟南芥遗传作图是基于成熟的技术和既定的程序。然而，它在智力上具有挑战性，并能够培训新手的基本实验室技能。这些程序可以分为适合学生课程表的小任务。学生参加每周的实验室会议，并在区域会议和校园活动期间就他们的工作进行年度演讲。本科生经常被列为出版物的合著者。此外，该项目将参加最近在密歇根州立大学实施的植物基因组学夏季培训计划（www.plantgenomics.msu.edu）。