Anja Geitmann (Plant Cell Biology, Université de Montréal, Canada)
Abstract: Plant developmental processes such as growth and the generation of organ shape result from a combination of plant cell growth and differentiation, cell division and cell death. Plant cells differ mechanically from most animal cells by the presence of a cell wall, or extracellular matrix, composed largely of polysaccharides that envelop the protoplast with a more or less stiff shell. The presence of this wall prevents plant cells from motion such as crawling and contraction, characteristics that are common to many animal cells. The wall connects neighbouring cells and hence essentially locks in place the individual cells composing a mature tissue. On the other hand, plant cells are able to grow substantially and this process requires the addition of building material in the form of cell wall polymers and membrane. While new cell wall material is incorporated, the existing material is deformed and stretched mechanically. The force for this deformation is supplied by the turgor pressure but achieving a desired shape requires spatial control of the mechanical properties of the wall. These in turn are regulated by the targeted deposition of soft or rigid wall material and wall modifying enzymes. Intracellular transport mechanisms that ensure the timely and spatially controlled delivery of these substances therefore play a crucial role in plant cell morphogenesis. Both actin arrays and microtubules have distinct functions in the morphogenetic process leading to plant cell differentiation. Various approaches to modeling the cellular expansion process in polarly growing plant cells, and the logistics of the associated intracellular trafficking mechanisms will be presented to illustrate the challenges associated with modeling plant cell morphogenesis.