Abstract
Plant cells initiate nascent cortical microtubules from gamma-tubulin-containing complexes dispersed on the cell cortex located at the sides of pre-existing microtubules as branching pattern. The minus-ends of new microtubules are usually released from their sites of nucleation and the free microtubules are then transported to new locations by polymer treadmilling. By using live cell imaging, we found that nucleation complexes labeled by GFP-tagged gamma complex proteins transiently stabilize at the cell cortex where a fraction of labeled complexes nucleate nascent microtubules upon association with pre-existing mother microtubules and that severing proteins labeled by GFP-tagged katanin p60 subunits appear at the branching nucleation sites after growth of daughter microtubules was observed and disappeared before, or coincident with, detection of microtubule detachment. These observations suggest that the nucleation complexes are primarily activated upon association with microtubule lattices, and become destabilized in part by katanin activity. We are analyzing the spatiotemporal control of the novel protein that localizes at the nucleation sites.
