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

National Institute for Basic Biology, Okazaki 444-8585, 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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    • "entro - some . Microtubules also moved outward by dynein - powered sliding , but sliding was not es - sential for aster growth . How microtubules are nucleated away from the centrosome in inter - phase asters is not clear . A logical possibility is that microtubules are nucleated from the sides of preexisting microtubules , as they are in plants ( Murata et al . 2005 ) , via recruitment of g - tubu - lin complexes by Augmin / Haus complexes ( Petry et al . 2013 ) . However , in preliminary ex - periments , immunodepletion of augmin did not block aster growth ( K Ishihara and TJ Mitch - ison , unpubl . ) . We concluded that interphase asters in large egg and blastomere cells likely grow outward as an"
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    ABSTRACT: The first 12 cleavage divisions in Xenopus embryos provide a natural experiment in size scaling, as cell radius decreases ∼16-fold with little change in biochemistry. Analyzing both natural cleavage and egg extract partitioned into droplets revealed that mitotic spindle size scales with cell size, with an upper limit in very large cells. We discuss spindle-size scaling in the small- and large-cell regimes with a focus on the "limiting-component" hypotheses. Zygotes and early blastomeres show a scaling mismatch between spindle and cell size. This problem is solved, we argue, by interphase asters that act to position the spindle and transport chromosomes to the center of daughter cells. These tasks are executed by the spindle in smaller cells. We end by discussing possible mechanisms that limit mitotic aster size and promote interphase aster growth to cell-spanning dimensions. Copyright © 2015 Cold Spring Harbor Laboratory Press; all rights reserved.
    Cold Spring Harbor perspectives in biology 08/2015; DOI:10.1101/cshperspect.a019182 · 8.68 Impact Factor
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    • "Cortical microtubules play a central role in regulating the development of cell wall structures by controlling how the cellulose synthase complex is targeted to the plasma membrane (Paredez et al., 2006; Crowell et al., 2009; Gutierrez et al., 2009). Although cortical microtubules are closely and tightly anchored to the plasma membrane, they exhibit dynamic behaviors, such as growth, shrinkage, and branching (Shaw et al., 2003; Murata et al., 2005; Chan et al., 2009; Nakamura et al., 2010) and exhibit bundling (Dixit and Cyr, 2004), which leads to the self-organization of parallel microtubule arrays (Wasteneys and Ambrose, 2009). Several microtubule-associated proteins (MAPs) have been discovered that regulate the global dynamics of cortical microtubules in the cell. "
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    ABSTRACT: Patterning of the cellulosic cell wall underlies the shape and function of plant cells. The cortical microtubule array plays a central role in the regulation of cell wall patterns. However, the regulatory mechanisms by which secondary cell wall patterns are established through cortical microtubules remain to be fully determined. Our recent study in xylem vessel cells revealed that a mutual inhibitory interaction between cortical microtubules and distinct plasma membrane domains leads to distinctive patterning in secondary cell walls. Our research revealed that the recycling of active and inactive ROP proteins by a specific GAP and GEF pair establishes distinct de novo plasma membrane domains. Active ROP recruits a plant-specific microtubule-associated protein, MIDD1, which mediates the mutual interaction between cortical microtubules and plasma membrane domains. In this mini review, we summarize recent research regarding secondary wall patterning, with a focus on the emerging interplay between plasma membrane domains and cortical microtubules through MIDD1 and ROP.
    Frontiers in Plant Science 12/2013; 4:511. DOI:10.3389/fpls.2013.00511 · 3.95 Impact Factor
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    • "The chromatin-dependent microtubule generation pathway has been investigated in detail, and the results indicated that Ran-GTP and the chromosome passenger complex, which are enriched around the chromosomes, induce microtubule nucleation [9-11]. In addition, the microtubule-dependent microtubule generation pathway, which was originally identified in the cells of fission yeast [12] and higher plants [13], involves the generation of microtubules throughout the spindle and not necessarily near the chromosomes [14-16]. "
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    ABSTRACT: The completion of cytokinesis is crucial for mitotic cell division. Cleavage furrow ingression is followed by the breaking and resealing of the intercellular bridge, but the detailed mechanism underlying this phenomenon remains unknown. Katanin is a microtubule-severing protein comprised of an AAA ATPase subunit and an accessory subunit designated as p60 and p80, respectively. Localization of katanin p60 was observed at the midzone to midbody from anaphase to cytokinesis in rat cells, and showed a ring-shaped distribution in the gap between the inside of the contractile ring and the central spindle bundle in telophase. Katanin p60 did not bind with p80 at the midzone or midbody, and localization was shown to be dependent on microtubules. At the central spindle and the midbody, no microtubule growth plus termini were seen with katanin p60, and microtubule density was inversely correlated with katanin p60 density in the region of katanin p60 localization that seemed to lead to microtubule destabilization at the midbody. Inhibition of katanin p60 resulted in incomplete cytokinesis by regression and thus caused the appearance of binucleate cells. These results suggest that katanin p60 contributes to microtubule instability at the midzone and midbody and facilitates cytokinesis in rat cells.
    PLoS ONE 11/2013; 8(11):e80392. DOI:10.1371/journal.pone.0080392 · 3.23 Impact Factor
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