Discovery of the Mechanisms Enabling the Dynamic Architecture of the Plant ER

真核细胞生物学的核心问题是如何建立和维持细胞器的身份。内质网（ER）是分泌途径的重要细胞器，用于生产各种细胞构建块，以及控制必要的应激和激素信号通路。为了达到最大的效率，内质网采用了一种独特的结构，其特点是由相互连接的膜管和膜片组成的网络形成封闭的多边形。内质网完整性的发现来自于对各种模式生物/系统的研究，如果蝇、酵母和培养的人类细胞。然而，与这些系统相比，内质网在植物谱系中获得了独特的形态和功能特征，这可能与它在脂质合成、叶绿体、细胞间通讯、蛋白质储存和植物特异性激素信号传导方面的重要作用有关。本项目的目的是通过基因突变、活细胞成像和生化方法来研究维持植物内质网完整性的独特调控机制。这些方法已经确定了几个编码内质网完整性和结构关键参与者的基因，包括拟南芥内质网相关的动力蛋白样蛋白RHD3。该项目研究旨在阐明RHD3以及通过突变体筛选发现的其他基因产物在维持植物内质网结构和功能中的机制作用。由于内质网的完整性和功能是两个密不可分的特征，该研究将促进对多细胞生物背景下植物分泌途径中内质网作用的一般理解，并有助于回答真核生物系统中内质网组织和功能差异的基本问题。更广泛的影响植物除了提供材料和燃料外，还是所有动物和人类直接或间接的主要碳和氮来源。植物的分泌途径在将固定碳转化为富含能量的物质，如蛋白质、脂质和复合糖的过程中起着至关重要的作用。这些植物衍生产品不仅对营养很重要，而且有可能被用作可再生燃料、润滑剂、纺织品和建筑材料。由于进化适应的结果，真核生物之间存在着独特的变异，因此研究植物内质网的独特特性非常重要。内质网是细胞重要组成部分的生物合成和生长、发育和逆境反应中必不可少的信号通路的关键细胞器。该项目还将通过为其他植物细胞生物学家提供独特的植物系和结构，扩大对植物细胞科学研究界的影响。这项研究将通过密歇根州立大学和当地社区的多种途径促进教学、研究培训和外展活动。特别是，项目人员将通过让学生和教师参与实验室的研究活动和在学校进行科学报告，继续与学生和教师交流植物科学方面的发现及其对社会的影响。

INTELLECTUAL MERITA central question in eukaryotic cell biology is how the identity of organelles is established and maintained. The endoplasmic reticulum (ER) is an essential organelle of the secretory pathway for the production of a wide variety of the cell's building blocks, as well as for the control of essential stress and hormonal signaling pathways. To achieve maximum efficiency, the ER assumes a unique architecture characterized by a network of interconnected membrane tubules and sheets to form closed polygons. Discoveries in ER integrity are emerging from studies in various model organisms/systems such as fruit flies, yeast and cultured human cells. Compared with these systems, however, the ER has acquired unique morphological and functional features in the plant lineage that are likely linked to its important role in lipid synthesis together with chloroplast, intercellular communication, protein storage and plant-specific hormone signaling. The goal of this project is to investigate the unique regulatory mechanisms that maintain plant ER integrity by using genetic mutants, live cell imaging and biochemical approaches. These approaches have identified several genes that encode critical players involved in ER integrity and architecture including an Arabidopsis ER-associated dynamin-like protein, named RHD3. The project research aims to elucidate the mechanistic role of RHD3, as well as other gene products identified by mutant screens, in maintaining the architecture and functions of the plant ER. Since integrity and function are two inextricably linked features of the ER, the research will advance the general understanding of ER roles in the plant secretory pathway in the context of a multicellular organism and contribute to answering fundamental questions regarding differences in ER organization and function across eukaryotic systems. BROADER IMPACTSPlants are the direct or indirect primary carbon and nitrogen source of all animals and humans, in addition to their role in providing materials and fuels. The secretory pathway of plants plays a fundamental role in the conversion of fixed carbon into energy-rich materials, such as proteins, lipids and complex sugars. These plant-derived products are not only important for nutrition, but have the potential to be used as renewable fuels, lubricants, textiles and building materials. Because unique variations exist among eukaryotes as a result of evolutionary adaptation, it is important to study the unique properties of the plant ER which is the key organelle for the biosynthesis of important building blocks of cells and for essential signaling path-ways in growth, development and stress responses. The project will also broaden the impact of on the plant cell science research community by providing unique plant lines and constructs which will be made available to other plant cell biologists. The research will promote teaching, research training and outreach activities through multiple avenues both at Michigan State University as well as the local community. In particular, project personnel will continue to communicate to students and teachers discoveries in plant science and their impact on the society by engaging students and teachers in research activities in the lab and by performing science presentations at schools.