Mitosis in the yeast phase of Agaricostilbum pulcherrimum and its evolutionary significance

1996 ◽  
Vol 74 (9) ◽  
pp. 1392-1406 ◽  
Author(s):  
Elizabeth M. Frieders ◽  
David J. McLaughlln
Keyword(s):  
Cell Cycle ◽  
Spindle Pole Body ◽  
Cladistic Analysis ◽  
Freeze Substitution ◽  
Spindle Pole ◽  
Yeast Cells ◽  
Evolutionary Significance ◽  
Basidiomycetous Yeasts ◽  
Spindle Pole Bodies ◽  
Yeast Phase

Agaricostilbum pulcherrimum is an anomaly and is difficult to place systematically. It possesses a yeast phase, and as in most basidiomycetous yeasts, mitosis has not been investigated cytoiogically. Yeast cells of A. pulcherrimum were prepared for immunofluorescence and transmission electron microscopy by a freeze-substitution method. A cladistic analysis of cell cycle characters among A. pulcherrimum and two ascomycetous and two basidiomycetous yeasts, performed with phylogenetic analysis using parsimony, revealed that A. pulcherrimum is basal within these basidiomycetes. Spindle pole bodies are multilayered discs and appear to be intranuclear during early division, similar to meiotic division. Spindle initiation and early elongation occur in the parent, a situation unreported in basidiomycetous yeasts. The site of spindle initiation, the position of the nucleus during division, and the pattern of astral microtubules demonstrate that the mode of nuclear division in A. pulcherrimum is intermediate between those of the investigated ascomycetous and basidiomycetous yeasts. Keywords: basidiomycete, cell cycle, cytoskeleton, immunofluorescence, phylogeny, spindle pole body.

Asymmetry of the spindle pole bodies and spg1p GAP segregation during mitosis in fission yeast

1999 ◽  
Vol 112 (14) ◽  
pp. 2313-2321 ◽  
Author(s):  
L. Cerutti ◽  
V. Simanis
Keyword(s):  
Cell Cycle ◽  
Fission Yeast ◽  
Spindle Pole Body ◽  
Mitotic Cell ◽  
Spindle Pole ◽  
The Other ◽  
Septum Formation ◽  
Spindle Pole Bodies ◽  
Interphase Cells ◽  
Early Mitosis

In the fission yeast Schizosaccharomyces pombe, the onset of septum formation is induced by a signal transduction network involving several protein kinases and a GTPase switch. One of the roles of the spg1p GTPase is to localise the cdc7p protein kinase to the poles of the mitotic spindle, from where the onset of septation is thought to be signalled at the end of mitosis. Immunofluorescence studies have shown that cdc7p is located on both spindle pole bodies early in mitosis, but only on one during the later stages of anaphase. This is mediated by inactivation of spg1p on one pole before the other. The GAP for spg1p is a complex of two proteins, cdc16p and byr4p. Localisation of cdc16p and byr4p by indirect immunofluorescence during the mitotic cell cycle showed that both proteins are present on the spindle pole body in interphase cells. During mitosis, byr4p is seen first on both poles of the spindle, then on only one. This occurs prior to cdc7p becoming asymmetric. In contrast, the signal due to cdc16p decreases to a low level during early mitosis, before being seen strongly on the same pole as byr4p. Double staining indicates that this is the opposite pole to that which retains cdc7p in late anaphase. Examination of the effect of inactivating cdc16p at various stages of the cell cycle suggests that cdc16p, together with cdc2p plays a role in restraining septum formation during interphase. The asymmetric inactivation of spg1p is mediated by recruitment of the cdc16p-byr4p GAP to one of the poles of the spindle before the other, and the asymmetry of the spindle pole bodies may be established early during mitosis. Moreover, the spindle pole bodies appear to be non-equivalent even after division has been completed.

scholarly journals Studies concerning the temporal and genetic control of cell polarity in Saccharomyces cerevisiae.

1991 ◽  
Vol 114 (3) ◽  
pp. 515-532 ◽  
Author(s):  
M Snyder ◽  
S Gehrung ◽  
B D Page
Keyword(s):  
Cell Cycle ◽  
Cell Polarity ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Yeast Cells ◽  
Cell Cycle Distribution ◽  
Restrictive Temperature ◽  
Microtubule Bundle ◽  
Pole Body ◽  
Capture Site

The establishment of cell polarity was examined in the budding yeast, S. cerevisiae. The distribution of a polarized protein, the SPA2 protein, was followed throughout the yeast cell cycle using synchronized cells and cdc mutants. The SPA2 protein localizes to a patch at the presumptive bud site of G1 cells. Later it concentrates at the bud tip in budded cells. At cytokinesis, the SPA2 protein is at the neck between the mother and daughter cells. Analysis of unbudded haploid cells has suggested a series of events that occurs during G1. The SPA2 patch is established very early in G1, while the spindle pole body residues on the distal side of the nucleus. Later, microtubules emanating from the spindle pole body intersect the SPA2 crescent, and the nucleus probably rotates towards the SPA2 patch. By middle G1, most cells contain the SPB on the side of the nucleus proximal to the SPA2 patch, and a long extranuclear microtubule bundle intersects this patch. We suggest that a microtubule capture site exists in the SPA2 staining region that stabilizes the long microtubule bundle; this capture site may be responsible for rotation of the nucleus. Cells containing a polarized distribution of the SPA2 protein also possess a polarized distribution of actin spots in the same region, although the actin staining is much more diffuse. Moreover, cdc4 mutants, which form multiple buds at the restrictive temperature, exhibit simultaneous staining of the SPA2 protein and actin spots in a subset of the bud tips. spa2 mutants contain a polarized distribution of actin spots, and act1-1 and act1-2 mutants often contain a polarized distribution of the SPA2 protein suggesting that the SPA2 protein is not required for localization of the actin spots and the actin spots are not required for localization of the SPA2 protein. cdc24 mutants, which fail to form buds at the restrictive temperature, fail to exhibit polarized localization of the SPA2 protein and actin spots, indicating that the CDC24 protein is directly or indirectly responsible for controlling the polarity of these proteins. Based on the cell cycle distribution of the SPA2 protein, a "cytokinesis tag" model is proposed to explain the mechanism of the non-random positioning of bud sites in haploid yeast cells.

scholarly journals Budding Yeast Bub2 Is Localized at Spindle Pole Bodies and Activates the Mitotic Checkpoint via a Different Pathway from Mad2

1999 ◽  
Vol 145 (5) ◽  
pp. 979-991 ◽  
Author(s):  
Roberta Fraschini ◽  
Elisa Formenti ◽  
Giovanna Lucchini ◽  
Simonetta Piatti
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Cell Cycle Progression ◽  
Budding Yeast ◽  
Spindle Pole Body ◽  
Mitotic Checkpoint ◽  
Spindle Pole ◽  
Cycle Progression ◽  
Spindle Pole Bodies

The mitotic checkpoint blocks cell cycle progression before anaphase in case of mistakes in the alignment of chromosomes on the mitotic spindle. In budding yeast, the Mad1, 2, 3, and Bub1, 2, 3 proteins mediate this arrest. Vertebrate homologues of Mad1, 2, 3, and Bub1, 3 bind to unattached kinetochores and prevent progression through mitosis by inhibiting Cdc20/APC-mediated proteolysis of anaphase inhibitors, like Pds1 and B-type cyclins. We investigated the role of Bub2 in budding yeast mitotic checkpoint. The following observations indicate that Bub2 and Mad1, 2 probably activate the checkpoint via different pathways: (a) unlike the other Mad and Bub proteins, Bub2 localizes at the spindle pole body (SPB) throughout the cell cycle; (b) the effect of concomitant lack of Mad1 or Mad2 and Bub2 is additive, since nocodazole-treated mad1 bub2 and mad2 bub2 double mutants rereplicate DNA more rapidly and efficiently than either single mutant; (c) cell cycle progression of bub2 cells in the presence of nocodazole requires the Cdc26 APC subunit, which, conversely, is not required for mad2 cells in the same conditions. Altogether, our data suggest that activation of the mitotic checkpoint blocks progression through mitosis by independent and partially redundant mechanisms.

scholarly journals Components of the yeast spindle and spindle pole body.

1990 ◽  
Vol 111 (5) ◽  
pp. 1913-1927 ◽  
Author(s):  
M P Rout ◽  
J V Kilmartin
Keyword(s):  
Spindle Pole Body ◽  
Spindle Pole ◽  
The Other ◽  
Yeast Cells ◽  
Immunofluorescent Staining ◽  
Cell Extracts ◽  
Pole Body ◽  
Spindle Pole Bodies ◽  
Cytoplasmic Face ◽  
Spindle Microtubules

Yeast spindle pole bodies (SPBs) with attached nuclear microtubles were enriched approximately 600-fold from yeast cell extracts. 14 mAbs prepared against this enriched SPB fraction define at least three components of the SPB and spindle. Immunofluorescent staining of yeast cells showed that throughout the cell cycle two of the components (110 and 90 kD) were localized exclusively to the SPB region, and the other (80 kD) was localized both to the SPB region and to particulate dots in short spindles. Immunoelectron microscopy confirmed and extended most of these findings. Thus the 110-kD component was localized to a layer in the SPB just to the nuclear side of the plane of the inner nuclear membrane. The 90-kD component was localized in a layer across the cytoplasmic face of intact SPBs, and, in SPBs where nuclear microtubules were removed by extraction with DEAE-dextran, the 90-kD component was also found in an inner nuclear layer close to where spindle microtubules emerge. In intact SPBs with attached nuclear microtubules the anit-80-kD mAb labels microtubules, particularly those close to the SPB. These results begin to provide a preliminary molecular map of the SPB and should also enable the corresponding genes to be isolated.

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.

scholarly journals PREFERENTIAL OCCURRENCE OF NONSISTER SPORES IN TWO-SPORED ASCI OF SACCHAROMYCES CEREVISIAE: EVIDENCE FOR REGULATION OF SPORE-WALL FORMATION BY THE SPINDLE POLE BODY

Genetics ◽  
1980 ◽  
Vol 94 (3) ◽  
pp. 581-595 ◽  
Author(s):  
Lance S Davidow ◽  
Loretta Goetsch ◽  
Breck Byers
Keyword(s):  
Spindle Pole Body ◽  
Electron Microscopic Examination ◽  
Spindle Pole ◽  
Spore Wall ◽  
Yeast Cells ◽  
Thermal Arrest ◽  
Electron Microscopic ◽  
Spore Yield ◽  
Pole Body ◽  
Spindle Pole Bodies

ABSTRACT Yeast cells subjected to a reversible thermal arrest of meiosis yielded progressively fewer spores per ascus as the arrest was extended. Dissection of two-spored asci by a newly developed method that prevents selection of false asci revealed that the spores were not a random sample of the haploid meiotic products. Most, if not all, pairs of spores contain nonsister products of the reductional division. Electron microscopic examination of the meiotic cells revealed the cytological basis for this bias. All four spindle pole bodies (SPBs) present at the second meiotic division normally gain a structural modification (the outer plaque) upon which the initiation of the prospore wall occurs. In the formation of a two-spored ascus, only one spindle pole body on each meiosis I1 spindle was so modified. These observations suggest that the morphogenesis of spcires is regulated at meiosis 11 by limiting the number of SPBs gaining the outer plaque. The enhancement of spore yield upon addition of fresh medium suggests that this morphogenetic regulation responds more directly to nutrient deprivation arising during the thermal arrest, rather than to elevated temperature per se.

Evidence for cell cycle-specific, spindle pole body-mediated, nuclear positioning in the fission yeast Schizosaccharomyces pombe

1997 ◽  
Vol 110 (16) ◽  
pp. 1851-1866 ◽  
Author(s):  
I. Hagan ◽  
M. Yanagida
Keyword(s):  
Cell Cycle ◽  
Fission Yeast ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Nuclear Positioning ◽  
Central Location ◽  
Pole Body ◽  
Spindle Pole Bodies ◽  
A Cell ◽  
Multiple Spindle

Specific changes in spatial order occur during cell cycle progression in fission yeast. Growth of the rod-shaped cells is highly regulated and undergoes a cell cycle and size-regulated switch from monopolar to bipolar tip extension. During both phases of growth, the interphase nucleus is maintained in a central location. Following the separation of the genome to the cell tips in mitosis, the two nuclei migrate back towards the cell equator before stopping in two new positions that will become the middle of the two new cells. Here we use simultaneous labeling of microtubules, chromatin and spindle pole bodies in wild-type and cdc mutants, to show that nuclear positioning is achieved by regulation of spindle pole body-mediated nuclear migration. We show that the number and location of nuclear positioning signals is regulated in a cell cycle-specific manner and that spindle pole body-mediated forces are likely to be responsible for maintaining correct nuclear position once the nuclei have reached the appropriate position in the cell. Accentuating the movement of the nuclei back towards the cell equator after mitosis by artificially increasing cell length shows that the spindle pole body leads the nucleus during this migration. When multiple spindle pole bodies are associated with the same or different nuclei they all go to the same point indicating that the different spindle pole bodies are responding to the same positional cue. In a septation-defective mutant cell, which contains four nuclei, the spindle pole bodies on the four different nuclei initially group as two pairs in regions that would become the middle of the new cells, were the cell able to divide. In the subsequent interphase, the nuclei aggregate as a group of four in the centre of the cell. The presence of two or three clusters of spindle pole bodies in larger cells with eight nuclei suggests that the mechanisms specifying the normally central location for multiple nuclei may be unable to operate properly as the cells get larger. Perturbation of microtubules with the microtubule poison thiabendazole prevents the spindle pole body clustering in septation mutants, demonstrating that nuclear positioning requires a functional microtubule cytoskeleton.

Variation in cytoplasmic microtubule organization and spindle length between the two forms of the dimorphic fungus Candida albicans

1988 ◽  
Vol 91 (2) ◽  
pp. 211-220
Author(s):  
R. Barton ◽  
K. Gull
Keyword(s):  
Cell Cycle ◽  
Candida Albicans ◽  
Mitotic Spindle ◽  
Spindle Pole ◽  
Yeast Cells ◽  
Dimorphic Fungus ◽  
Microtubule Organization ◽  
Cytoplasmic Microtubule ◽  
Yeast Phase ◽  
Cytoplasmic Microtubules

Candida albicans is a dimorphic fungus capable of growing as a budding yeast and as a filamentous hypha. We have used the technique of immunofluorescence to study the changes in the microtubule cytoskeleton during the cell cycle in both growth forms. This approach has revealed the presence of an extensive system of microtubules, including cytoplasmic microtubules and a rod-like intranuclear spindle. We have provided a complete description of the arrangement of cytoplasmic and spindle microtubules at each phase of the yeast cell cycle. A novel and characteristic feature of the yeast phase of Candida is the presence of an array of short microtubules at the neck of the doublet cell. This neck-associated array (NAA), is apparently organized independently of the main microtubule-organizing centre, the spindle pole bodies, at late anaphase. Analysis of microtubule patterns in the hyphal state reveals that the general arrangements of microtubules are similar to those seen in the yeast phase. These patterns suggest a role for the cytoplasmic microtubules in the nuclear migration that occurs during hyphal growth. A major finding is that the mitotic spindle in hyphae is considerably longer (12–20 microns) than the spindle in yeast cells (7–8 microns). This may reflect the role of the hyphal mitotic spindle not only in nuclear division but also in the positioning of the daughter nuclei at the centres of hyphal compartments.

scholarly journals Depletion of a Polo-like Kinase inCandida albicansActivates Cyclase-dependent Hyphal-like Growth

2003 ◽  
Vol 14 (5) ◽  
pp. 2163-2180 ◽  
Author(s):  
Catherine Bachewich ◽  
David Y. Thomas ◽  
Malcolm Whiteway
Keyword(s):  
Cell Cycle ◽  
Regulatory Networks ◽  
Hyphal Growth ◽  
Growth Conditions ◽  
Spindle Pole ◽  
Yeast Cells ◽  
Internal Cell ◽  
Spindle Pole Bodies ◽  
A Cell ◽  
Spindle Elongation

Morphogenesis in the fungal pathogen Candida albicans is an important virulence-determining factor, as a dimorphic switch between yeast and hyphal growth forms can increase pathogenesis. We identified CaCDC5, a cell cycle regulatory polo-like kinase (PLK) in C. albicans and demonstrate that shutting off its expression induced cell cycle defects and dramatic changes in morphology. Cells lacking CaCdc5p were blocked early in nuclear division with very short spindles and unseparated chromatin. GFP-tagged CaCdc5p localized to unseparated spindle pole bodies, the spindle, and chromatin, consistent with a role in spindle elongation at an earlier point in the cell cycle than that described for the homologue Cdc5p in yeast. Strikingly, the cell cycle defects were accompanied by the formation of hyphal-like filaments under yeast growth conditions. Filament growth was determinate, as the filaments started to die after 24 h. The filaments resembled serum-induced hyphae with respect to morphology, organization of cytoplasmic microtubules, localization of nuclei, and expression of hyphal-specific components. Filament formation required CaCDC35, but not EFG1 or CPH1. Similar defects in spindle elongation and a corresponding induction of filaments occurred when yeast cells were exposed to hydroxyurea. Because CaCdc5p does not appear to act as a direct repressor of hyphal growth, the data suggest that a target of CaCdc5p function is associated with hyphal-like development. Thus, an internal, cell cycle–related cue can activate hyphal regulatory networks in Candida.

γ-Tubulin and the fungal microtubule cytoskeleton

1995 ◽  
Vol 73 (S1) ◽  
pp. 352-358 ◽  
Author(s):  
Berl R. Oakley
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Microtubule Organizing Center ◽  
Pole Body ◽  
Spindle Pole Bodies ◽  
Key Words Tubulin ◽  
Organizing Center ◽  
Chromosomal Condensation

γ-Tubulin is present in phylogenetically diverse eukaryotes. It is a component of microtubule organizing centers such as the spindle pole bodies of fungi. In Aspergillus nidulans and Schizosaccharomyces pombe, it is essential for nuclear division, and, thus, for viability. In A. nidulans, nuclei carrying a γ-tubulin disruption can be maintained in heterokaryons, and the phenotypes caused by the disruption can be determined in uninucleate spores produced by the heterokaryons. Experiments with heterokaryons created in strains with mutations that allow synchronization of the cell cycle reveal that γ-tubulin is not required for the transition from the G1 phase of the cell cycle through S phase to G2, nor for the entry into mitosis as judged by chromosomal condensation. It is, however, required for the formation of the mitotic spindle and for the successful completion of mitosis. Staining with the MPM-2 monoclonal antibody reveals that spindle pole body replication occurs in the absence of functional γ-tubulin. Finally, human γ-tubulin functions in fission yeast, and this indicates that γ-tubulin has similar functions in widely divergent organisms. Key words: tubulin, microtubule, spindle pole body, microtubule organizing center.

Sign in / Sign up

Export Citation Format

Share Document