The role of gravity and cell wall in setting up cytoskeleton-based polarity in plant cells
09 / 2007 - 09 / 2010
The cytoskeleton and the cell wall both play key roles in plant cell growth and division, determining and consolidating the plant's final shape and performance (yield). It is known that under microgravity conditions, in vitro tubulin does not self-organize in the ordered patterns observed in 1g. At the same time, microtubules in protoplasts (plant cells without walls) in microgravity fail to organize in parallel arrays, required for proper cell elongation. However, an earlier project performed by us (TUBUL ESA 2006) shows that the cortical array of isolated walled plant cells from a suspension culture is unaffected by microgravity. This result points to a role for the cell wall in structuring the microtubule cytoskeleton. Resolving the involved mechanism is crucial for understanding how crops could be most efficiently propagated during long-term space missions. Although we do know that an intricate crosstalk exists between microtubules in the cell cortex and cellulose microfibrils in the adjacent wall, the exact interrelationship of these polymers is not known. Since microgravity appears to uncouple cell wall formation and cortical microtubule organization, gravity becomes the experimental tool to address the question of the orientation mechanism of cortical microtubules and cellulose microfibrils. How can a cell wall impose direction on cortical microtubules? Our current objective is to study the role of the cellulose microfibrils and the cellulose synthase complexes that produce them, in setting up parallel arrays of cortical microtubules. The outcome of this project will shed light on this interrelationship and thus on plant performance in general.