Experimental manipulation of gamma-tubulin distribution in Arabidopsis using anti-microtubule drugs.

gamma-Tubulin-specific antibodies stain the microtubule (Mt) arrays of Arabidopsis suspension cells in a punctate or patchy manner. During division, staining of kinetochore fibers and the phragmoplast is extensive, except in the vicinity of the plus ends at the metaphase plate and cell plate. gamma-Tubulin localization responds to low levels of colchicine, with staining receding farther toward the minus (pole) ends of kinetochore fibers. At higher drug concentrations, gamma-tubulin also associates with abnormal Mt foci as well as with the surface of the daughter nuclei facing the phragmoplast. During UV-induced recovery from colchicine, gamma-tubulin increases along the presumptive minus ends of mitotic Mts as well as the phragmoplast near the daughter nuclei. With CIPC, immunostaining is concentrated around the centers of focal Mt arrays in multipolar spindles. In the presence of taxol, Mts are more prominent but the mitotic apparatus and phragmoplast are abnormal. As with CIPC, gamma-tubulin is concentrated at focal arrays. Increased punctate staining is also present in interphase arrays, with fluorescent dots often located at the ends of Mts. These results support a preferential association between gamma-tubulin and Mt minus ends, but are also consistent with more general binding along the walls of Mts. Thus, minus ends (and Mt nucleation sites) may be present throughout plant Mt arrays, but gamma-tubulin may also serve another function, such as in structural stabilization.