Article

Murata, T. et al. Microtubule-dependent microtubule nucleation based on recruitment of -tubulin in higher plants. Nature Cell Biol. 7, 961-968

The University of Tokushima, Tokusima, Tokushima, Japan
Nature Cell Biology (Impact Factor: 19.68). 11/2005; 7(10):961-8. DOI: 10.1038/ncb1306
Source: PubMed

ABSTRACT

Despite the absence of a conspicuous microtubule-organizing centre, microtubules in plant cells at interphase are present in the cell cortex as a well oriented array. A recent report suggests that microtubule nucleation sites for the array are capable of associating with and dissociating from the cortex. Here, we show that nucleation requires extant cortical microtubules, onto which cytosolic gamma-tubulin is recruited. In both living cells and the cell-free system, microtubules are nucleated as branches on the extant cortical microtubules. The branch points contain gamma-tubulin, which is abundant in the cytoplasm, and microtubule nucleation in the cell-free system is prevented by inhibiting gamma-tubulin function with a specific antibody. When isolated plasma membrane with microtubules is exposed to purified neuro-tubulin, no microtubules are nucleated. However, when the membrane is exposed to a cytosolic extract, gamma-tubulin binds microtubules on the membrane, and after a subsequent incubation in neuro-tubulin, microtubules are nucleated on the pre-existing microtubules. We propose that a cytoplasmic gamma-tubulin complex shuttles between the cytoplasm and the side of a cortical microtubule, and has nucleation activity only when bound to the microtubule.

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    • "By visualizing pericentrin, a major centrosomal protein, Can et al. (2005) demonstrated a dispersion of pericentriolar material in BPA-treated mouse oocytes, that resulted in increased number of centrosomes and multipolar spindles. On the other hand, in dividing cells of angiosperms and gymnosperms , which lack centrosomes, mitotic MTs are considered to be nucleated at pleiomorphic MTOCs, as evidenced by the transposable localization of g-tubulin, an integral component of MTOCs, at different places where the specialized plant MT arrays are organized (Murata et al., 2005; Binarov a et al., 2006; Brown and Lemmon, 2007). Although gymnosperms develop acentriolar spindles as well, several studies have shown that they display special centrosomal properties (Wang et al., 1991; Fowke, 1993; Zachariadis et al., 2004 ). "
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