Getting pectins into the plant cell wall: synthesis, secretion and targeting

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The cell wall that surrounds plant cells glues cells together to form tissues and thus is critical for plant growth and development. Further, it allows interaction between plant cells and is the first point of contact between plants and other organisms such as insect pests and disease-causing bacteria. The basic (primary) cell wall of plant cells can be considered a fibre-reinforced gel in which stiff cellulose microfibrils are connected via hemicelluloses, and contained within a gel matrix of pectins. Commercially, plant cell walls are key in products from foods and food supplements to textiles, paper, wood, emulsifiers, adhesives and bioenergy feedstocks.The long term goal of my research program is to understand how plant cell wall components and the proteins that remodel them in response to external and developmental challenges are made within cells and shipped to the cell surface. My goal for this current proposal is to study how components of the pectin gel are made in the cell interior and shipped to where they are needed at certain points along the cell border. Specifically, I intend to investigate:(1) How a novel gene is required for pectin production.(2) Steps along the pathway of pectin shipment from its intracellular ‘factory’ (Golgi apparatus) to the cell surface and how this is controlled by two protein complexes.(3) How pectins are targeted to only certain portions of the cell surface.To investigate these processes, I work with the genetic model plant Arabidopsis thaliana and will focus my studies on the mucilage secreting cells on the surface of its seeds. During seed development, these cells make a very large quantity of pectin that is deposited into a ring-shaped ‘pocket’ at their upper surface, making them an excellent system in which to study pectin production and targeted shipment. To address my questions, I will use a combination of genetics and molecular biology to study gene and protein function, and microscopy to follow events at the cellular and subcellular levels. The research program described will provide new insights into the production and targeted building and remodeling of plant cell walls. This deeper understanding in turn will inform production of plant crops required to meet increasing Canadian and global challenges in agriculture related to climate change and the need for increased bioenergy and bioproduct feedstocks (e.g. plant fibres, adhesives, emulsifiers).