Unlike humans, plants cannot rely on their skeleton for rigidity. Instead, most of the plant’s cells contribute to maintaining its structure. To do so they are enveloped in a rigid cell wall and have a high internal pressure. When the plant extends and its cells grow, this cell wall must be stretched in a particular direction. This directional growth is enabled by the microfibrils in the cell wall that wrap around the cell in a parallel fashion, effectively forming a corset that defines the growth axis. The established pattern mimics that of the underlying parallel cortical microtubules, rigid thin protein tubes that are located on the inner surface of the cell wall and membrane.
The research addresses the question how the microtubules that seem to ‘crawl’ like worms across the inside of the cell membrane can collectively form the observed array: parallel to each other and perpendicular to the cell’s growth axis. The system has many ingredients, such as the growth and shrinkage speeds of the individual microtubules, but also the prescription for what happens when two microtubules collide. Theoretical and simulation work indicate that the collective alignment of microtubules is triggered primarily by so-called ‘catastrophic collisions’, in which a collision causes a growing microtubule to start shrinking. In addition, simulations show that the cell can determine the orientation of the ‘corset’ by small localized changes in microtubule behavior.
Title thesis: "Biomolecular design elements: cortical microtubules and DNA-coated colloids"