Cellular Mechanisms Templating Complex Extracellular Structures via Cellulose Scaffolds: the Oikopleura House

Extracellular matrices are a fundamental interface through which cells and organisms interact with their external environment. In some cases very complex 3-dimensional structures are formed and the extracellular matrix of plants is crucial in effecting de velopmental pattern formation. Cellulose scaffolding is often involved in fabricating such structures and unravelling the cellular mechanisms used to template cellulose microfibrils into defined extracellular arrays has recently become an active area of r esearch. Cellulose, the most abundant natural product in the biosphere, with a tensile strength superior to that of steel, is central to the world economy, integral to the production of paper products, textiles, building materials and dietary fibre. Curre ntly, in plants, competing models as to how cells are organized to template the deposition of cellulose microfibrils range from fusion of secretory vesicles containing scaffolding proteins to targeted domains of the plasma membrane, to organization of put ative transmembrane scaffolding proteins along underlying microtubule rails. Though widespread in plants, cellulose synthesis is restricted to precisely one subphylum of animals, the urochordates. We will use the urochordate Oikopleura dioica as a model t o investigate how a monolayer of animal epithelial cells templates cellulose microfibrils into a scaffold for repetitive construction of the complex 3-dimensional extracellular house in which the animal lives. Given the enormous phylogenetic distance betw een plants and urochordates it will be of interest to compare whether convergent mechanisms for templating cellulose microfibrils are employed in both plant and animal cells or to what extent different or specialized gene families have been recruited in e ach case. Understanding these processes in plant and animal cells should conceivably lead to downstream applications in the bioengineering of extracellular macromolecular structures in the biotechnology industry.