Emergence of helical growth in fungal cells from a self-organizing cell wall

Walled cells such as plants, algae and fungi achieve expansive growth using turgor pressure that helps mediate irreversible wall deformation and regulates their shape and volume. The architecture of the cell wall plays a crucial role in this process where a network of microfibrils and tethers (complex polysaccharides and proteins) dynamically mediate the network topology via continuous detachment and reattachment events. A direct consequence of wall architecture, through microfibril re-orientation, is the helical growth of the fungal cells of Phycomyces Blakesleeanus. Powered by turgor pressure and the biochemistry to regulate molecular processes that induce network organization, these cells can control the growth rate and direction of the helix. The relationship between local molecular mechanisms and global emerging behaviors of these cells is still poorly understood. We present a novel approach based in statistical mechanics to model the organization of microfibrils and tethers in the cell wall. The model is then used to predict (a) the longitudinal elongation and rotation rates along the growth zone and (b) the inversion in rotation direction during growth stages in wild-type sporangiophores, and for radial expansion in piloboloid mutants.