A Window into the Early Steps in Plastid Evolution

质体进化早期步骤的窗口

• 批准号: 1157627
• 负责人: Arthur Grossman
• 金额: $ 41.85万
• 依托单位: Carnegie Institution of Washington
• 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=1157627&HistoricalAwards=false
• 关键词: Window; into; Early; Steps; Plastid

INTELLECTUAL MERITThe proposed work addresses the question of the way in which the photosynthetic organelle, the chloroplast, evolved. The organism used in these studies is the thecate protist Paulinella chromatophora, which contains what visually resembles a cyanobacterium within its cytoplasm, although this internal "cyanobacterium" is really an organelle called a chromatophore. Even though the chromatophore does not look like a chloroplast, it performs many of the same functions as chloroplasts, capturing sunlight to drive photosynthesis, which provides the protist host cell with energy and carbon backbones for growth. The chromatophore contains its own genome (DNA), like a chloroplast, but the size of this genome is 5-10 times more than what is found in most chloroplasts, but much less than what is found in cyanobacteria. These findings suggest that the chromatophore is an organelle derived from an endosymbiotic cyanobacterium that is in the process of evolving into a chloroplast, and as such it can reveal important information about mechanisms critical for the early events in chloroplast evolution. We recently discovered that a number of proteins important for the function of the chromatophore are synthesized outside of the chromatophore and in the cytoplasm of the host protist cell, and must be transported into the organelle where they function (e.g. PsaE, a protein that functions in photosynthesis). The major specific thrust of our studies is to identify those proteins and to develop an understanding of how they move from the cytoplasm of the host protist into the nascent chloroplast, where they assemble into large functional complexes. BROADER IMPACTSIn a broad sense, this work is critical to our understanding of both the processes by which cellular organelles evolved and the ways in which two organisms can come together and integrate their functions into a highly efficient single organism. The result of this work and the concepts that grow out of those results will have broad intellectual impact in that they will: (1) shed light on early events associated with the transport of proteins into developing organelles; (2) suggest which proteins are most suited (based on their biophysical properties) to enter developing chloroplasts through systems that already exist in the host organism; (3) allow for the identification of proteins that may require more extensive tailoring before they can assume the right conformation to enter organelles (they may have to enter the chloroplast through a more specialized system that develops over evolutionary time); (4) provide a broader understanding of the development of regulatory events that have integrated the synthesis of proteins in the cytoplasm of the cell with those synthesized in the chloroplast; (5) suggest new ways in which proteins can be engineered to get them into specific subcellular compartments, which may be important for aspects of synthetic biology and the tailoring cells to make specific products such as biofuels; (6) train graduate students to perform experiments that test evolutionary concepts using molecular and biochemical tools and techniques; (7) be incorporated into an undergraduate course that is being taught at Stanford University that focuses on the functionality, evolution and regulation of photosynthetic processes ("From Photosynthesis to Biofuels").

智力优势拟议的工作解决的问题，其中光合细胞器，叶绿体，进化的方式。在这些研究中使用的生物体是泡囊原生生物Paulinella chromatophora，它在其细胞质中含有视觉上类似于蓝细菌的东西，尽管这种内部的“蓝细菌”实际上是一种称为色素细胞的细胞器。尽管色素体看起来不像叶绿体，但它执行许多与叶绿体相同的功能，捕获阳光以驱动光合作用，为原生生物宿主细胞提供生长所需的能量和碳骨架。色素细胞含有自己的基因组（DNA），就像叶绿体一样，但这个基因组的大小是大多数叶绿体中发现的5-10倍，但比蓝藻中发现的要小得多。这些研究结果表明，色素细胞是一个细胞器来自内共生蓝藻是在进化成叶绿体的过程中，因此，它可以揭示重要的信息机制的叶绿体进化的早期事件的关键。我们最近发现，一些重要的色素细胞的功能的蛋白质合成的色素细胞外，在宿主原生生物细胞的细胞质中，必须被运送到细胞器，它们的功能（例如PsaE，在光合作用中的蛋白质的功能）。我们研究的主要具体目标是识别这些蛋白质，并了解它们如何从宿主原生生物的细胞质进入新生叶绿体，在那里它们组装成大型功能复合物。更广泛的影响从广义上讲，这项工作对于我们理解细胞器进化的过程以及两种生物体可以走到一起并将其功能整合到一个高效的单一生物体中的方式都至关重要。 这项工作的结果和从这些结果中产生的概念将产生广泛的智力影响，因为它们将：（1）阐明与蛋白质运输到发育中的细胞器相关的早期事件;（2）建议哪些蛋白质最适合（根据其生物物理特性）通过宿主生物体中已经存在的系统进入发育中的叶绿体;（3）允许识别可能需要更广泛剪裁的蛋白质，然后才能呈现正确的构象进入细胞器（它们可能必须通过一个在进化过程中发展起来的更专门的系统进入叶绿体）;（四）提供了一个更广泛的理解，发展的调控事件，整合了蛋白质的合成在细胞质中的细胞与那些合成的，叶绿体;（5）提出新的方法，使蛋白质可以工程化，使他们进入特定的亚细胞区室，这可能是重要的合成生物学和剪裁细胞的方面，使特定的产品，如生物燃料;（6）培训研究生进行实验，测试进化的概念，使用分子和生物化学的工具和技术;（7）纳入斯坦福大学正在教授的本科课程，该课程侧重于光合作用过程的功能、进化和调节（“从光合作用到生物燃料”）。