Abstract
Plant cells lack a centrosome-like microtubule organizer. To illustrate plant microtubule organizing centers we tried to elucidate the function of Arabidopsis thaliana (At) GCP2, component of gamma-tubulin complex (gamma-TuC). AtGCP2 localized as dots along cortical microtubules and at filament branching points. Analyzing null mutants suggested AtGCP2 is essential for viability and gametophyte development. We also obtained a weak gcp2 allele, spiral3 (spr3) which has aberrant cortical microtubule arrays. spr3 mutation impairs interaction with AtGCP2 and another component of gamma-TuC, AtGCP3. In plant cells, cortical microtubules are nucleated as branches on the pre-existing microtubules. The angles of branching in spr3 cells were altered from those in wild-type cells. We also observed differences in minus end microtubule dynamics between the mutant and wild-type cells.
Our results indicate that gamma-TuCs containing AtGCP2 are responsible for microtubule nucleation in plant interphase cells and contribute to the formation and organization of the cortical microtubule arrays.
