Abstract
Plant cells initiate nascent cortical microtubules from gamma- tubulin-containing complexes dispersed on existing microtubules as branching patterns. Newly formed microtubules are released from the nucleation sites, and then free microtubules are transported on the cell cortex by polymer treadmilling. By using live cell imaging, we found that the nucleation complexes labeled by fluorescently-tagged gamma complex protein 2 (GCP2) or GCP3 transiently associate with cell cortex in a microtubule-independent manner, and a fraction of the complexes immediately nucleate nascent microtubules upon association with previously established mother microtubules. Daughter microtubules are sometimes nucleated parallel to the mother microtubules, thereby generating instantaneous bundles. The GCP2/3-containing complexes are anchored at the basis of branching points until the Katanin-dependent activity severs daughter microtubules at their minus ends or their dynamic plus ends completely depolymerizes. We are analyzing spatiotemporal control of katanin protein that contributes to a microtubule release event.
