Morphogenesis and mechanics of walled cells

Walled cells, such as those of plant, fungal and bacterial species, need to remodel their wall to establish and change their shape during growth. Using budding yeast (Saccharomyces cerevisiae) as model system, we are currently studying how the mechanics of the cell wall and the intracellular processes in charge of building the wall interplay to shape the cell. We have shown that a genetically-encoded mechanical feedback (working through the Cell Wall Integrity pathway) coordinates cell wall assembly and expansion to stabilize cellular morphogenesis in budding yeast. In the absence of mechanical feedback, cells cannot coordinate cell wall expansion and assembly, leading to cell lysis and death.

Beyond coordinating cell wall assembly and expansion, cells must coordinate cell polarization and morphogenesis. Most theoretical and computational models of cell polarization have been studied in spherical geometries and it has been shown that the spatiotemporal dynamics of relatively simple molecular networks can spontaneously break the symmetry and molecularly polarize the cell. However, as cell shape changes, it is essential that the cell maintains cell polarization at specific locations of the cell surface to guide morphogenetic events. Our work indicates that a mechanical feedback encoded in the Cell Wall Integrity pathway can maintain the polarization cap at the tip of a growing mating projection. This description indicates that such genetically-encoded mechanical feedback can provide important positional information to the molecular machinery in the cell, enabling the coordination of cell polarization and morphogenesis.

In addition, we are on the role of plasma membrane homeostasis and recycling during morphogenesis. Our previous work has shown that localized exocytosis drives membrane tension gradients that cause membrane flows. We are studying the interplay between these membrane flows and protein dynamics in tip growing cells.