Zhenbiao Yang, UC Riverside, Theoretical and experimental insights into pollen tube tip growth and guidance

Tip growth is an extreme form of intrinsic self-organizing polar growth that generates tubular cells, while its growth axis is controlled by external vectorial cues such as gradients of attractants in growth guidance. Such growth behavior allows tip-growing cells to efficiently explore the environment, invade host cells and target to the destination. Both externally directed and intrinsic tip growth depend on polarized Rho GTPase signaling and exocytosis, suggesting a potential common design principle underlying these processes. Using Arabidopsis pollen tubes as a model system, we are uncovering this design principal by integrating mathematical modeling with experimental approaches. Our studies suggest that at the center of the design principle for intrinsic tip growth is polar exocytosis, which couples the self-organizing ROP1 GTPase feedback loops with the cell wall mechanical properties that maintain the cylindrical cell shape while allowing the apical expansion under internal turgor pressure. I will discuss how this design principle can be tweaked to simulate pollen tube guidance as well as tip growth in other cell types such as fungal hyphae.