Speaker
Description
Polarized growth and division in tip-growing cells require tight coordination between membrane trafficking, in-plane membrane flows, and biochemical patterning. Using Schizosaccharomyces pombe, we combine mathematical and computational modeling with experiments by collaborators to study the physical mechanisms of membrane flows in cell polarity, cytokinesis, and stress adaptation. We developed a continuum hydrodynamic model of the plasma membrane during cell division, treating it as a compressible fluid coupled to cell wall mechanics and osmotic pressure. The model reveals how contractile ring constriction and spatially regulated endo- and exocytosis generate membrane tension and flows, and identifies regimes where trafficking is essential to maintain membrane integrity during division. We also examined how secretion-driven flows during tip growth interact with the Cdc42 polarity system. A stochastic reaction–diffusion model with membrane area conservation, constrained by experimental FRAP measurements and measured rates of endocytosis and exocytosis, shows how membrane flows deplete low-mobility GAPs from regions of growth, enabling robust polarization. Polarization persists even when Cdc42 mobility is reduced, though with broader and weaker activity zones, highlighting the interplay between protein mobility and flow-driven redistribution. Finally, studies of membrane expansion under protoplast hypoosmotic stress show how rapid lipid delivery, including non-vesicular transfer, buffers delays in exocytosis and helps preserve membrane integrity. These results highlight membrane flows as active regulators of pattern formation and mechanical robustness in walled cells.
