Abstract
Plant cells initiate nascent microtubules from gamma- tubulin-containing complexes dispersed on existing microtubules. We simultaneously visualized microtubules (by mCherry-TUB6) and microtubule organizing centers (by gamma-tubulin-complex protein 2-GFP) in transgenic Arabidopsis plants. In interphase epidermal cells, we observed three types of microtubule nucleation events; (1) branching nucleation in which nascent microtubules are formed from the side of existing microtubules at an angle of around 40 degrees, (2) intra-bundle nucleation in which a new microtubule is formed parallele to the existing microtubule, resulting in an instantaneous bundle formation, and (3) de novo nucleation in the absence of existing microtubules. GCP2-GFP still remained on the cell cortex when cortical microtubules were depolymerized by microtubule-disrupting drugs, indicating a microtubule independent association of GCPs to the cell cortex. We are currently analyzing the microtubule nucleation events in a katanin mutant which is defectivein microtubule severing. Contributin of microtubule nucleation to microtubule organization will be discussed.
