Localization of translation and non-translated mRNAs; functions, mechanisms and novel compartments

植物和藻类通过光合作用从光中获得生长和繁殖所需的能量。光合作用发生在称为叶绿体的亚细胞器中。我们先前的研究表明，叶绿体含有蛋白质合成和RNA质量控制的隔间。我们正在分析这些隔室，以此作为了解这种细胞器中的生物发生和质量控制的途径，并希望揭示细胞生物学的一般原理。这项研究计划的一个目标是了解叶绿体中构成类囊体囊泡的膜是如何形成的。类囊体囊泡进行光合作用的光驱动反应。我们已经确定了膜被膜上包裹叶绿体的一个特殊区域，在那里产生了类囊体体的蛋白质和叶绿素。我们首次展示了细胞质的核糖体正在合成与叶绿体直接接触的蛋白质。这在大多数其他细胞器中都有表现，但在叶绿体中却没有。对叶绿体被膜这一新的生物起源结构域组成的表征将有助于对类囊体膜的发育起源及其如何从叶绿体被膜产生的长期谜团有新的见解。另一个目标是确定叶绿体中处理RNA质量控制的隔间的特征。RNA是基因传递遗传信息以产生功能蛋白的重要分子。叶绿体有自己的基因组和基因表达系统，因为它们是从一种自由生活的光合作用细菌进化而来的，这种细菌在大约10-20亿年前栖息在原始植物细胞中。此后，叶绿体保留了缩小的基因组和基因表达系统，包括RNA。我们鉴定和研究的结构被称为“叶绿体应激颗粒”，它处理刚刚离开蛋白质合成机器且没有被翻译的RNA。这些叶绿体应激颗粒类似于在所有被研究的真核细胞中发现的应激颗粒，甚至在细菌中也被称为应激颗粒。我们将对叶绿体应激颗粒进行表征，以了解该细胞器如何处理RNA质量控制，并希望为所有生物体中应激颗粒的功能提供一般性的见解。总而言之，这一结果将与加拿大工业生物技术的发展相关，因为几十年来，藻类一直被用于食品工业，并作为环境污染物的生物传感器。正在对藻类进行工程改造，以在工业规模上高效地生产高价值分子；例如，药品、疫苗和食品补充剂。这一潜力的实现将得益于我们关于蛋白质如何在叶绿体中合成的研究结果。这些成果还将有助于掌握农业作物生物技术改良所需的基本知识。

Plants and algae obtain energy for growth and reproduction from light using a process called photosynthesis. Photosynthesis occurs in subcellular organelles called chloroplasts. Our previous research revealed that chloroplasts contain compartments for the synthesis of proteins and RNA quality control. We are analyzing these compartments as an avenue to understand biogenesis and quality control in this organelle and, we hope, reveal general principles of Cell Biology. One goal of this research program is to understand how the membranes that make up thylakoid vesicles within chloroplasts are made. Thylakoid vesicles carry out the light-driven reactions of photosynthesis. We have identified a special region of the membranous envelope that encloses the chloroplast where proteins and chlorophyll of the thylakoids are generated. We show for the first time that the ribosomes of the cell's cytoplasm are synthesizing proteins in direct contact with the chloroplast. This has been show for most other organelles, but not for chloroplasts. Characterization of the composition of this novel biogenic domain of the chloroplast envelope will lead to new insights regarding the long-standing mystery regarding the developmental origins of thylakoid membranes and how they arise from the chloroplast envelope. Another goal is to characterize a compartment within the chloroplast that handles quality control of RNA. RNA is an important molecule in the transfer of genetic information from the gene to generate functional proteins. Chloroplasts have their own genome and gene expression system because they evolved from a free-living photosynthetic bacterium which took up residence in the primordial plant cell some 1-2 billion year ago. Since, chloroplasts have retained a downsized genome and gene expression system, including RNA. We identified and study structures are called "chloroplast stress granules" which handle RNA that has just left the protein synthesis machinery and is not being translated. These chloroplast stress granules are similar to stress granules found in all eukaryotic cells examined and even in bacteria called stress granules. We will characterize chloroplast stress granules to learn about how this organelle handles RNA quality control and, we hope, provide general insights into stress granule functions in all organisms. In summary, the results will be relevant to the development of biotechnologies for Canadian industries because algae are used in the food industry and as biosensors for environmental pollutants for decades. Algae are being engineered to efficiently produce high-value molecules at industrial scales; e.g. pharmaceuticals, vaccines, and food supplements. Realization of this potential will benefit from our research results regarding how proteins are synthesized in chloroplasts. The results will also contribute to the basic knowledge that will be required for the biotechnological improvement of crop plants in agriculture.