Mechanisms of Lipid Import into Chloroplasts

脂质输入叶绿体的机制

• 批准号: 1157231
• 负责人: Christoph Benning
• 金额: $ 74万
• 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: 2012
• 资助国家: 美国
• 起止时间: 2012-05-01 至 2016-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1157231&HistoricalAwards=false
• 关键词: Mechanisms; Lipid; Import; into; Chloroplasts

INTELLECTUAL MERIT The chloroplast is the defining organelle of plant cells. It contains the photosynthetic membrane, which converts sunlight into chemical energy, a process essential to most forms of life on earth. The photosynthetic membrane is not able to make its building blocks, the polar lipid constituents, but relies on lipid precursors assembled at the inner and outer chloroplast envelope membranes and the endoplasmic reticulum (ER), a membrane system outside the chloroplast. Therefore, lipid transfer into the chloroplast and through the envelope membranes to the photosynthetic membranes is essential. Gaining a mechanistic understanding of lipid transfer processes involved in the assembly of the photosynthetic membrane is the long-term goal of this project.The isolation of genetic mutants of the model plant Arabidopsis disrupted in ER-to-chloroplast lipid transfer has enabled first mechanistic studies of the underlying phenomena. The tgd mutants of Arabidopsis are disrupted in chloroplast lipid import and are named for their characteristic phenotype, the accumulation of the oligogalactolipid trigalactosyldiacylglycerol. Availability of these mutants led to the identification of four key proteins (TGD1,2,3,4) involved in the process. TGD1, 2 and 3 resemble components of ATP Binding Cassette (ABC) transporters and are hypothesized to assemble into a complex that facilitates transfer of lipids between the chloroplast envelope membranes and through the inner envelope membrane. The TGD4 protein on the other hand is integrated in the chloroplast outer envelope membrane and is hypothesized to transfer lipids from the ER to the TGD1,2,3 complex. This project will investigate how TGD4 and TGD1,2,3 complexes assemble and form a lipid conduit from the ER through the chloroplast envelope membranes, an essential feature of chloroplast membrane biogenesis.BROADER IMPACTS Mechanisms of interorganelle lipid transfer in any eukaryotic cell are poorly understood but essential to organelle formation. Thus, it is expected that the analysis of chloroplast lipid import will provide mechanistic insights into general lipid transfer phenomena relevant beyond plant cells. The project also provides excellent training opportunities for a postdoctoral researcher, a graduate student, and undergraduate student, who collaborate effectively in a team. Elements of the project are specifically designed for the participation of undergraduate students, and will provide training in basic laboratory techniques in molecular biology and biochemistry and require critical thinking towards proper experimental controls and data analysis. All participants including the undergraduate students present their results in weekly lab meetings, present posters or talks at scientific meetings, and participate in the publication of the results as coauthors. All coauthors actively participate in manuscript writing. Co-mentoring of the graduate and undergraduate students by the postdoctoral researcher provides experience in the management of people and projects. In addition, undergraduate students working on the project participate in a summer training program in Plant Genomics at Michigan State University. This program has successfully recruited a diverse group of students and faculty in the past five years.

叶绿体是植物细胞中起决定作用的细胞器。它含有光合膜，将阳光转化为化学能，这是地球上大多数生命形式所必需的过程。光合作用膜不能制造其构件，即极性脂质成分，而是依赖于组装在叶绿体内外被膜和内质网（ER）（叶绿体外的膜系统）处的脂质前体。因此，脂质进入叶绿体并通过被膜进入光合膜是必需的。本项目的长期目标是从机理上理解光合膜组装过程中的脂质转移过程，分离出在内质网-叶绿体脂质转移过程中受到破坏的模式植物拟南芥的遗传突变体，这使得对潜在现象的第一次机理研究成为可能。 拟南芥的tgd突变体在叶绿体脂质输入中被破坏，并以其特征表型，寡聚半乳糖脂三半乳糖基二酰基甘油的积累而命名。这些突变体的可用性导致鉴定了参与该过程的四个关键蛋白（TGD 1，2，3，4）。TGD 1、2和3类似于ATP结合盒（ABC）转运蛋白的组分，并且被假设组装成促进脂质在叶绿体被膜之间和通过内被膜转移的复合物。另一方面，TGD 4蛋白整合在叶绿体外被膜中，并假设将脂质从ER转移到TGD 1，2，3复合物。本项目将研究TGD 4和TGD 1，2，3复合物如何组装并形成从内质网通过叶绿体被膜的脂质管道，叶绿体膜生物合成的一个重要特征。更广泛的影响在任何真核细胞中的细胞器间脂质转移的机制知之甚少，但对细胞器的形成至关重要。因此，它是预期的叶绿体脂质输入的分析将提供机制的见解一般脂质转移现象相关超越植物细胞。 该项目还为博士后研究人员，研究生和本科生提供了良好的培训机会，他们在团队中有效合作。该项目的内容是专门为本科生的参与而设计的，将提供分子生物学和生物化学基本实验室技术方面的培训，并要求对适当的实验控制和数据分析进行批判性思维。包括本科生在内的所有参与者在每周的实验室会议上展示他们的结果，在科学会议上展示海报或演讲，并作为合著者参与结果的出版。所有合著者都积极参与手稿写作。由博士后研究员共同指导研究生和本科生，提供人员和项目管理方面的经验。此外，从事该项目的本科生还参加了密歇根州立大学的植物基因组学暑期培训项目。在过去的五年里，该计划成功地招募了一批不同的学生和教师。