A reevaluation of the mitotic spindle pole body cycle in Tilletia caries based on freeze-substitution techniques

1994 ◽  
Vol 72 (10) ◽  
pp. 1412-1423 ◽  
Author(s):  
Kerry O'donnell
Keyword(s):  
Electron Microscopy ◽  
Mitotic Spindle ◽  
Spindle Pole Body ◽  
Freeze Substitution ◽  
Spindle Pole ◽  
Metaphase Chromosomes ◽  
Tilletia Caries ◽  
Pole Body ◽  
The One ◽  
Mitotic Spindle Pole

Mitosis in the wheat pathogen Tilletia caries (Basidiomycota, Tilletiales) was investigated by electron microscopy of serially sectioned, fast-frozen, freeze-substituted mitotic cells called ballistospores. A duplicated spindle pole body consisting of two identical, three-layered globular elements connected by a middle piece was attached to the extranuclear face of each nucleus at interphase. During mitosis, astral and spindle microtubules radiated from the globular elements that form the poles of an intranuclear spindle. At metaphase, chromosomes were interspersed with the nonkinetochore microtubules, and they were spread along the central two-thirds of the spindle. Each chromatid was attached to a spindle pole by a single, continuous, kinetochore microtubule. Postmitotic replication of the spindle pole body occurred during late telophase to interphase. Results from this study are presented in the form of a model of the mitotic spindle pole body cycle in Tilletia, and this model is compared with the one previously reported for Tilletia and other basidiomycetes. Key words: electron microscopy, freeze substitution, mitosis, spindle pole body, Tilletia.

The transition of cells of the fission yeast beta-tubulin mutant nda3-311 as seen by freeze-substitution electron microscopy. Requirement of functional tubulin for spindle pole body duplication

1990 ◽  
Vol 96 (2) ◽  
pp. 275-282
Author(s):  
T. Kanbe ◽  
Y. Hiraoka ◽  
K. Tanaka ◽  
M. Yanagida
Keyword(s):  
Electron Microscopy ◽  
Cross Section ◽  
Nuclear Membrane ◽  
Mitotic Spindle ◽  
Spindle Pole Body ◽  
Freeze Substitution ◽  
Spindle Pole ◽  
Permissive Temperature ◽  
Beta Tubulin ◽  
Pole Body

A previous fluorescence light-microscopic study showed that the fission yeast cold-sensitive beta-tubulin mutant nda3-311 was arrested with rod-like condensed chromosomes in a mitotic state at the restrictive temperature. Upon transfer to the permissive temperature, a spindle was formed and the nucleus was divided. In the present study, we employed freeze-substitution electron microscopy to examine the ultrastructure of arrested and released nda3-311 cells. In arrested cells, a single, displaced nucleus was seen with a single spindle pole body. Therefore, spindle pole body duplication seemed to require functional beta-tubulin. The nuclear membrane was highly deformed with a leaf-like profile in cross-section, possibly due to an interaction with the rod-like, condensed chromosomes. Upon transfer to the permissive temperature, the spindle pole duplicated and the daughter spindle pole bodies rapidly migrated to the opposite ends of the nucleus, accompanied by the formation of the mitotic spindle. Elongation of the nuclear envelope occurred with concomitant spindle extension, as in a wild-type mitosis. The deformed nuclear membrane became smooth and described a convex curve. The numerous vacuoles that are seen in the arrested cells decreased in number and increased in size. Septation was completed, leaving the two divided nuclei in one half of the cell. Hexagonally arranged microtubules, apparently forming the mitotic spindle, were observed in a cross-section of a cell after return to the permissive conditions.

Role of gamma-tubulin in mitosis-specific microtubule nucleation from the Schizosaccharomyces pombe spindle pole body

1996 ◽  
Vol 109 (1) ◽  
pp. 165-177 ◽  
Author(s):  
H. Masuda ◽  
T. Shibata
Keyword(s):  
Protein Kinase ◽  
Mitotic Spindle ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Microtubule Nucleation ◽  
Amino Terminal ◽  
Pole Body ◽  
Gamma Tubulin ◽  
Mitotic Spindle Pole

The ability of the Schizosacchromyces pombe spindle pole body to nucleate microtubules is activated at the onset of mitosis for forming a mitotic spindle, but it is inactivated during interphase. We have previously developed an in vitro assay for studying the molecular mechanism of spindle pole body activation using permeabilized interphase S. pombe cells and Xenopus mitotic extracts. We have shown that the interphase spindle pole body is activated indirectly by p34cdc2 protein kinase in Xenopus mitotic extracts. In this study we examined the role of gamma-tubulin, a component of both interphase and mitotic spindle pole body, in formation of the microtubule nucleating complex at the mitotic spindle pole body. A polyclonal antibody specific to S. pombe gamma-tubulin inhibited both activation of the interphase spindle pole body and microtubule nucleation from the mitotic spindle pole body. Addition of bacterially expressed S. pombe gamma-tubulin or its amino-terminal fragments to Xenopus mitotic extracts inhibited spindle pole body activation. Affinity chromatography of partially fractionated Xenopus mitotic extracts with the amino-terminal fragment of S. pombe gamma-tubulin showed that fractions bound to the fragment supported the activation. The fractions did not contain Xenopus gamma-tubulin, showing that activation of the spindle pole body is not due to recruitment of Xenopus gamma-tubulin to the spindle pole body. The spindle pole body activation occurred in extracts depleted of p34cdc2 protein kinase or MAP kinase. The activity of the fractions bound to the fragment was inhibited by a protein kinase inhibitor, staurosporine. These results suggest that S. pombe gamma-tubulin is a component of the microtubule nucleating complex, and that the function of proteins that interact with gamma-tubulin is required for activation of the spindle pole body. We present possible models for the activation that convert the immature microtubule nucleating complex at interphase into the mature microtubule nucleating complex at mitosis.

scholarly journals Mutant Membrane Protein of the Budding Yeast Spindle Pole Body Is Targeted to the Endoplasmic Reticulum Degradation Pathway

Genetics ◽  
2002 ◽  
Vol 162 (2) ◽  
pp. 567-578 ◽  
Author(s):  
Susan McBratney ◽  
Mark Winey
Keyword(s):  
Mitotic Spindle ◽  
Spindle Pole Body ◽  
Degradation Pathway ◽  
Spindle Pole ◽  
Wild Type ◽  
Er Quality Control ◽  
Pole Body ◽  
Cytoplasmic Face ◽  
Ubiquitin Conjugating Enzyme ◽  
Ubiquitin Conjugation

Abstract Mutation of either the yeast MPS2 or the NDC1 gene leads to identical spindle pole body (SPB) duplication defects: The newly formed SPB is improperly inserted into the nuclear envelope (NE), preventing the cell from forming a bipolar mitotic spindle. We have previously shown that both MPS2 and NDC1 encode integral membrane proteins localized at the SPB. Here we show that CUE1, previously known to have a role in coupling ubiquitin conjugation to ER degradation, is an unusual dosage suppressor of mutations in MPS2 and NDC1. Cue1p has been shown to recruit the soluble ubiquitin-conjugating enzyme, Ubc7p, to the cytoplasmic face of the ER membrane where it can ubiquitinate its substrates and target them for degradation by the proteasome. Both mps2-1 and ndc1-1 are also suppressed by disruption of UBC7 or its partner, UBC6. The Mps2-1p mutant protein level is markedly reduced compared to wild-type Mps2p, and deletion of CUE1 restores the level of Mps2-1p to nearly wild-type levels. Our data indicate that Mps2p may be targeted for degradation by the ER quality control pathway.

Ultrastructure of meiosis and the spindle pole body cycle in freeze-substituted basidia of the smut fungi Ustilago maydis and Ustilago avenae

1992 ◽  
Vol 70 (3) ◽  
pp. 629-638 ◽  
Author(s):  
Kerry O'Donnell
Keyword(s):  
Electron Microscopy ◽  
Spindle Pole Body ◽  
Ustilago Maydis ◽  
Spindle Pole ◽  
Meiotic Spindle ◽  
Smut Fungi ◽  
Late Prophase ◽  
Prophase I ◽  
Pole Body ◽  
Middle Piece

Meiosis in the smut fungi Ustilago maydis and Ustilago avenae (Basidiomycota, Ustilaginales) was studied by electron microscopy of serial-sectioned freeze substituted basidia. At prophase I, a spindle pole body composed of two globular elements connected by a middle piece was attached to the extranuclear surface of each nucleus. Astral and spindle microtubules were initiated at each globular element at late prophase I to prometaphase I. During spindle initiation, the middle piece disappeared and interdigitating half-spindles entered the nucleoplasm, which was surrounded by discontinuous nuclear envelope together with perinuclear endoplasmic reticulum. Kinetochore pairs at metaphase I were analyzed to obtain a karyotype for each species. The meiotic spindle pole body replicational cycle is described. Key words: electron microscopy, freeze-substitution, meiosis, Ustilago, spindle pole body.

scholarly journals Targeting Alp7/TACC to the spindle pole body is essential for mitotic spindle assembly in fission yeast

FEBS Letters ◽  
2014 ◽  
Vol 588 (17) ◽  
pp. 2814-2821 ◽  
Author(s):  
Ngang Heok Tang ◽  
Naoyuki Okada ◽  
Chii Shyang Fong ◽  
Kunio Arai ◽  
Masamitsu Sato ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Mitotic Spindle ◽  
Spindle Pole Body ◽  
Spindle Assembly ◽  
Spindle Pole ◽  
Pole Body ◽  
Mitotic Spindle Assembly

scholarly journals NDC1: a nuclear periphery component required for yeast spindle pole body duplication

1993 ◽  
Vol 122 (4) ◽  
pp. 743-751 ◽  
Author(s):  
M Winey ◽  
MA Hoyt ◽  
C Chan ◽  
L Goetsch ◽  
D Botstein ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Mitotic Spindle ◽  
Nuclear Periphery ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Immunofluorescent Localization ◽  
Pole Body ◽  
Acid Protein ◽  
Monopolar Spindle ◽  
Mutant Cells

The spindle pole body (SPB) of Saccharomyces cerevisiae serves as the centrosome in this organism, undergoing duplication early in the cell cycle to generate the two poles of the mitotic spindle. The conditional lethal mutation ndc1-1 has previously been shown to cause asymmetric segregation, wherein all the chromosomes go to one pole of the mitotic spindle (Thomas, J. H., and D. Botstein. 1986. Cell. 44:65-76). Examination by electron microscopy of mutant cells subjected to the nonpermissive temperature reveals a defect in SPB duplication. Although duplication is seen to occur, the nascent SPB fails to undergo insertion into the nuclear envelope. The parental SPB remains functional, organizing a monopolar spindle to which all the chromosomes are presumably attached. Order-of-function experiments reveal that the NDC1 function is required in G1 after alpha-factor arrest but before the arrest caused by cdc34. Molecular analysis shows that the NDC1 gene is essential and that it encodes a 656 amino acid protein (74 kD) with six or seven putative transmembrane domains. This evidence for membrane association is further supported by immunofluorescent localization of the NDC1 product to the vicinity of the nuclear envelope. These findings suggest that the NDC1 protein acts within the nuclear envelope to mediate insertion of the nascent SPB.

scholarly journals ULTRASTRUCTURE AND TIME COURSE OF MITOSIS IN THE FUNGUS FUSARIUM OXYSPORUM

1972 ◽  
Vol 55 (2) ◽  
pp. 368-389 ◽  
Author(s):  
James R. Aist ◽  
P. H. Williams
Keyword(s):  
Electron Microscopy ◽  
Fusarium Oxysporum ◽  
Time Course ◽  
Light And Electron Microscopy ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Metaphase Chromosomes ◽  
Mitotic Apparatus ◽  
Spindle Poles ◽  
Spindle Microtubules

Mitosis in Fusarium oxysporum Schlect. was studied by light and electron microscopy. The average times required for the stages of mitosis, as determined from measurements made on living nuclei, were as follows: prophase, 70 sec; metaphase, 120 sec; anaphase, 13 sec; and telophase, 125 sec, for a total of 5.5 min. New postfixation procedures were developed specifically to preserve the fine-structure of the mitotic apparatus. Electron microscopy of mitotic nuclei revealed a fibrillo-granular, extranuclear Spindle Pole Body (SPB) at each pole of the intranuclear, microtubular spindles. Metaphase chromosomes were attached to spindle microtubules via kinetochores, which were found near the spindle poles at telophase. The still-intact, original nuclear envelope constricted around the incipient daughter nuclei during telophase.

The spindle pole body cycle, meiosis, and basidial cytology of the smut fungus Microbotryum violaceum

1991 ◽  
Vol 69 (8) ◽  
pp. 1795-1803 ◽  
Author(s):  
Mary L. Berbee ◽  
Robert Bauer ◽  
F. Oberwinkler
Keyword(s):  
Spindle Pole Body ◽  
Freeze Substitution ◽  
Ustilago Maydis ◽  
Spindle Pole ◽  
Meiotic Spindle ◽  
Smut Fungus ◽  
Microbotryum Violaceum ◽  
Pole Body ◽  
Spindle Pole Bodies ◽  
Middle Piece

Freeze-substituted basidia of the smut fungus Microbotryum violaceum (Ustilaginales, Basidiomycotina) were examined electron microscopically with particular attention to the meiotic spindle pole body cycle and cytoplasmic characters of phylogenetic significance. Prophase basidia contained a subapical cluster of vesicles and tubules. During prophase, the spindle pole body consisted of two globular elements connected by a middle piece. The spindle pole body had an electron-opaque layer near the nucleus, and each globular element was bisected by an electron-opaque disk. The meiosis I spindle extended between two monoglobular, disc-containing spindle pole bodies. During interphase I and II, septa lacking pores divided the basidium between daughter nuclei. In interphase I, a putative new spindle pole body appeared between the nuclear envelope and the monoglobular spindle pole body residual from the first division. In meiosis II, a spindle was again established between two monoglobular spindle pole bodies, each of which again contained an electron-opaque disc. The cytoplasmic characters of M. violaceum are compared with those of Ustilago maydis and Sphacelotheca polygoni-serrulati. Key words: Microbotryum violaceum, basidiomycete, Ustilaginales, spindle pole body, freeze-substitution, ultrastructure.

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