Discovery of the mechanisms enabling morphological and functional integrity of the plant ER

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In addition to providing commodity materials and fuels, plant cells are an essential source of oxygen and nutrients to humans. Like all eukaryotes, the life of plants depends on the function of specialized structures, known as organelles that populate the subcellular environment. An essential organelle, whose function and morphology are largely conserved across eukaryotes, is the endoplasmic reticulum (ER). This project seeks to understand how the ER establishes and maintains its functional and morphological identity. As the ER is at the core of the cell's biosynthetic machinery, and because significant variation in ER biology exists among eukaryotes, studying the ER within model plant systems provides an essential foundation to improve plants as primary providers of useful biomolecules and to support life on this planet. This project on the Arabidopsis ER will also provide new fundamental knowledge that will influence the study of other organisms that share mechanisms underlying ER biogenesis with plants. In addition, it will provide societal benefits through education of the next generation of scientists, engagement of high-school students and teachers in research, and by communicating discoveries in plant science and their impact on the society through outreach activities.A central question in cell biology is how organelles establish and maintain their identity. Due to its rich, mutable morphology, the ER is a wonderful model to explore this question. The ER adopts an intricate web-like architecture via cytoskeleton-driven remodelling and anchoring of subdomains to the plasma membrane (PM). However, the mechanisms underlying ER shape as well as differentiation and function of ER-PM subdomains are largely unknown, especially in plants. The research will capitalize on the discovery of novel components of the Arabidopsis proteome that control ER morphology and interaction with heterotypic membranes, including the PM. Using a suite of advanced live-cell imaging approaches, functional genomics analyses and mathematical modeling, the project will characterize a novel plant ER shaper, define the molecular composition of the ER subdomains interacting with the PM and determining how such subdomains influence the biosynthesis and deposition of the extracellular matrix. The results will help create a new paradigm of plant ER structure and function. Since ER integrity and function are inextricably linked and the ER presents species-specific features, this research promises to significantly advance basic understanding of plant ER architecture and function, and provide a framework for comparative insights into ER biology among eukaryotes.