scholarly journals Mitosis in the cellular slime mold Polysphondylium violaceum.

1975 ◽  
Vol 64 (2) ◽  
pp. 480-491 ◽  
Author(s):  
U P Roos
Keyword(s):  
Spindle Pole ◽  
Equatorial Region ◽  
Cellular Slime Mold ◽  
Central Spindle ◽  
Spindle Pole Bodies ◽  
Cellular Slime ◽  
Late Telophase ◽  
Spindle Elongation ◽  
Well Differentiated ◽  
Opaque Body

Myxamebas of Polysphondylium violaceum were grown in liquid medium and processed for electron microscopy. Mitosis is characterized by a persistent nuclear envelope, ring-shaped extranuclear spindle pole bodies (SPBs), a central spindle spatially separated from the chromosomal microtubules, well-differentiated kinetochores, and dispersion of the nucleoli. SPBs originate from the division, during prophase, of an electron-opaque body associated with the interphase nucleus. The nuclear nevelope becomes fenestrated in their vicinity, allowing the build-up of the intranuclear, central spindle and chromosomal microtubules as the SPBs migrate to opposite poles. At metaphase the chromosomes are in amphitelic orientation, each sister chromatid being directly connected to the corresponding SPB by a single microtubule. During ana- and telophase the central spindle elongates, the daughter chromosomes approach the SPBs, and the nucleus constricts in the equatorial region. The cytoplasm cleaves by furrowing in late telophase, which is in other respects characterized by a re-establishment of the interphase condition. Spindle elongation and poleward movement of chromosomes are discussed in relation to hypotheses of the mechanism of mitosis.

Fine structure of an organelle associated with the nucleus and cytoplasmic microtubules in the cellular slime mould Polysphondylium violaceum

1975 ◽  
Vol 18 (2) ◽  
pp. 315-326
Author(s):  
U.P. Roos
Keyword(s):  
Mitotic Spindle ◽  
Spindle Pole ◽  
Interphase Nuclei ◽  
Spindle Pole Bodies ◽  
Nucleation Sites ◽  
Cellular Slime ◽  
Granular Matrix ◽  
Cytoplasmic Microtubules ◽  
Spindle Microtubules ◽  
Opaque Body

Polysphondylium violaceum was grown in association with Escherichia coli. Vegetative amoebae and pseudoplasmodia were fixed under different conditions and processed for electron microscopy. An electron-opaque body (nucleus-associated body, NAB) lies in the cytoplasm near the tapered end of interphase nuclei. The NAB consists of a disk-shaped, multilayered core, approximately 200 nm in diameter and 150 nm thick, embedded in a granular matrix from which electron-opaque nodules protrude. The nodules are termination points of microtubules radiating from the NAB into the cytoplasm or running along the nucleus. On the average there are 16 nodules per NAB. One or two microtubules terminate in each nodule. Spindle pole bodies, arising by duplication of the NAB at the beginning of mitosis, are unstructured foci for spindle microtubules in mitotic cells. It is suggested that cytoplasmic microtubules do not determine cell shape, but they probably cause the tapering deformation of the nucleus. They may, furthermore, represent a storage form of subunits for utilization during the formation of the mitotic spindle. The nodules of the NAB are potential nucleation sites of cytoplasmic microtubules during interphase. Spindle pole bodies presumably acquire a microtubule organizing capability by integration of the decondensed nodules.

scholarly journals Spindle and kinetochore morphology of Dictyostelium discoideum.

1976 ◽  
Vol 68 (1) ◽  
pp. 113-122 ◽  
Author(s):  
P B Moens
Keyword(s):  
Nuclear Envelope ◽  
Dictyostelium Discoideum ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Slime Molds ◽  
Central Spindle ◽  
Pole Body ◽  
Spindle Pole Bodies ◽  
Nuclear Separation ◽  
Cellular Slime

The metaphase spindle of haploid Dictyostelium discoideum (n = 7) is 2 mum long. It consists of some 20 microtubules which seem continuous between the spindle pole bodies and there are about 20 chromosomal microtubules at each end of the spindle. During anaphase the central spindle elongates and the chromosomal microtubules shorten. The spindle length and structure at this stage suggests that lengthening is caused by elongation as well as parallel sliding of the nonchromosomal microtubules. The nuclear envelope remains mostly intact during mitosis, and nuclear separation through medial constriction takes place when the spindle is 6 mum long. Cytokinesis occurs when the spindle is 10 mum long. At that time the kinetochores double in size. During interphase, the spindle pole body separates from the nucleus to a distance of 0.7 mum, and it returns at the onset of the next prophase when it becomes functionally double, thereby starting the formation of a central spindle. When comparing mitosis in the cellular slime molds Polysphondylium violaceum and D. discoideum, several similarities and some differences are apparent.

The ultrastructure of nuclear division in Armillaria mellea: meiosis

1979 ◽  
Vol 57 (18) ◽  
pp. 1860-1872 ◽  
Author(s):  
Diane Cope Peabody ◽  
Jerome J. Motta
Keyword(s):  
Nuclear Envelope ◽  
Membrane Structure ◽  
Nuclear Division ◽  
Spindle Pole ◽  
Armillaria Mellea ◽  
Spindle Pole Bodies ◽  
Late Telophase ◽  
Meiosis I ◽  
Metaphase I

Meiosis I in isolates of Armillaria mellea in which subhymenial hyphae are uninucleate and lack clamp connections was examined ultrastructurally. Although the overall pattern of development and basidiosporogenesis appears similar to other Homobasidiomycetes it was observed that spindle pole bodies are predominantly monoglobular and are associated with a unique membrane structure of the subtending nuclear envelope. The nuclear envelope also disappears at metaphase I and reforms by the coalescence of membrane fragments around the compacted chromatin at late telophase I. The significance of these features in relation to other Basidiomycetes is briefly discussed.

scholarly journals Analysis of the distribution of spindle microtubules in the diatom Fragilaria.

1978 ◽  
Vol 79 (3) ◽  
pp. 737-763 ◽  
Author(s):  
D H Tippit ◽  
D Schulz ◽  
J D Pickett-Heaps
Keyword(s):  
Spatial Arrangement ◽  
Spindle Pole ◽  
Serial Sections ◽  
Late Prophase ◽  
Central Spindle ◽  
Sources Of Error ◽  
Late Anaphase ◽  
Spindle Microtubules ◽  
Spindle Elongation ◽  
Intercellular Variability

The spindle of the colonial diatom Fragilaria contains two distinct sets of spindle microtubules (MTs): (a) MTs comprising the central spindle, which is composed of two half-spindles interdigitated to form a region of "overlap"; (b) MTs which radiate laterally from the poles. The central spindles from 28 cells are reconstructed by tracking each MT of the central spindle through consecutive serial sections. Because the colonies of Fragilaria are flat ribbons of contiguous cells (clones), it is possible, by using single ribbons of cells, to compare reconstructed spindles at different mitotic stages with minimal intercellular variability. From these reconstructions we have determined: (a) the changes in distribution of MTs along the spindle during mitosis; (b) the change in the total number of MTs during mitosis; (c) the length of each MT (measured by the number of sections each traverses) at different mitotic stages; (d) the frequency of different classes of MTs (i.e., free, continuous, etc.); (e) the spatial arrangement of MTs from opposite poles in the overlap; (f) the approximate number of MTs, separate from the central spindle, which radiate from each spindle pole. From longitudinal sections of the central spindle, the lengths of the whole spindle, half-spindle, and overlap were measured from 80 cells at different mitotic stages. Numerous sources of error may create inaccuracies in these measurements; these problems are discussed. The central spindle at prophase consists predominantly of continuous MTs (pole to pole). Between late prophase and prometaphase, spindle length increases, and the spindle is transformed into two half-spindles (mainly polar MTs) interdigitated to form the overlap. At late anaphase-telophase, the overlap decreases concurrent with spindle elongation. Our interpretation is that the MTs of the central spindle slide past one another at both late prophase and late anaphase. These changes in MT distribution have the effect of elongating the spindle and are not involved in the poleward movement of the chromosomes. Some aspects of tracking spindle MTs, the interaction of MTs in the overlap, formation of the prophase spindle, and our interpretation of rearrangements of MTs, are discussed.

scholarly journals A Novel Role of the Budding Yeast Separin Esp1 in Anaphase Spindle Elongation

2001 ◽  
Vol 152 (1) ◽  
pp. 27-40 ◽  
Author(s):  
Sanne Jensen ◽  
Marisa Segal ◽  
Duncan J. Clarke ◽  
Steven I. Reed
Keyword(s):  
Mutational Analysis ◽  
Spindle Pole ◽  
Nuclear Localization Sequence ◽  
Anaphase Promoting Complex ◽  
Nuclear Targeting ◽  
Spindle Pole Bodies ◽  
Localization Sequence ◽  
Spindle Midzone ◽  
Spindle Elongation ◽  
Anaphase B

In Saccharomyces cerevisiae, the metaphase–anaphase transition is initiated by the anaphase-promoting complex–dependent degradation of Pds1, whereby Esp1 is activated to promote sister chromatid separation. Although this is a fundamental step in the cell cycle, little is known about the regulation of Esp1 and how loss of cohesion is coordinated with movement of the anaphase spindle. Here, we show that Esp1 has a novel role in promoting anaphase spindle elongation. The localization of Esp1 to the spindle apparatus, analyzed by live cell imaging, is regulated in a manner consistent with a function during anaphase B. The protein accumulates in the nucleus in G2 and is mobilized onto the spindle pole bodies and spindle midzone at anaphase onset, where it persists into midanaphase. Association with Pds1 occurs during S phase and is required for efficient nuclear targeting of Esp1. Spindle association is not fully restored in pds1 mutants expressing an Esp1-nuclear localization sequence fusion protein, suggesting that Pds1 is also required to promote Esp1 spindle binding. In agreement, Pds1 interacts with the spindle at the metaphase–anaphase transition and a fraction remains at the spindle pole bodies and the spindle midzone in anaphase cells. Finally, mutational analysis reveals that the conserved COOH-terminal region of Esp1 is important for spindle interaction.

scholarly journals Budding Yeast Chromosome Structure and Dynamics during Mitosis

2001 ◽  
Vol 152 (6) ◽  
pp. 1255-1266 ◽  
Author(s):  
Chad G. Pearson ◽  
Paul S. Maddox ◽  
E.D. Salmon ◽  
Kerry Bloom
Keyword(s):  
Fluorescent Protein ◽  
Budding Yeast ◽  
Spindle Pole ◽  
Elastic Recoil ◽  
Rapid Acquisition ◽  
Anaphase Onset ◽  
Spindle Pole Bodies ◽  
Spindle Elongation ◽  
Green Fluorescent ◽  
Anaphase B

Using green fluorescent protein probes and rapid acquisition of high-resolution fluorescence images, sister centromeres in budding yeast are found to be separated and oscillate between spindle poles before anaphase B spindle elongation. The rates of movement during these oscillations are similar to those of microtubule plus end dynamics. The degree of preanaphase separation varies widely, with infrequent centromere reassociations observed before anaphase. Centromeres are in a metaphase-like conformation, whereas chromosome arms are neither aligned nor separated before anaphase. Upon spindle elongation, centromere to pole movement (anaphase A) was synchronous for all centromeres and occurred coincident with or immediately after spindle pole separation (anaphase B). Chromatin proximal to the centromere is stretched poleward before and during anaphase onset. The stretched chromatin was observed to segregate to the spindle pole bodies at rates greater than centromere to pole movement, indicative of rapid elastic recoil between the chromosome arm and the centromere. These results indicate that the elastic properties of DNA play an as of yet undiscovered role in the poleward movement of chromosome arms.

Mitosis in the rice blast fungus and its possible implications for pathogenic variability

1985 ◽  
Vol 63 (6) ◽  
pp. 1129-1134 ◽  
Author(s):  
K. V. S. R. Kameswar Row ◽  
J. R. Aist ◽  
J. P. Crill
Keyword(s):  
Nuclear Envelope ◽  
High Frequency ◽  
Spindle Pole Body ◽  
Rice Blast Fungus ◽  
Spindle Pole ◽  
Central Spindle ◽  
Pole Body ◽  
Spindle Pole Bodies ◽  
Pathogenic Variability ◽  
Anaphase B

Mitosis in Pyricularia oryzae was reexamined, using both living and stained specimens. During prophase, the spindle pole body becomes quiescent and separates into two parts. The nucleolus disperses as chromosomes become visible. At metaphase, the spindle pole bodies are situated at the ends of the intranuclear spindle to which the chromosomes are attached at different points along its length. Anaphase A disjunction of chromatids is asynchronous; consequently, lagging chromosomes are typical. Anaphase B involves a marked elongation of the central spindle as first one incipient daughter nucleus and then the other migrates out of the original, intact nuclear envelope. During telophase, the central spindle and remainder of the nuclear envelope disappear, the chromatin returns to the dispersed state, and the nucleolus reappears. Contrary to earlier reports, mitosis in P. oryzae is virtually identical with that now known to be typical for other Ascomycetes, such as Ceratocystis and Nectria. The high frequency of pathogenic variability in P. oryzae could result from aneuploidy, and several mechanisms by which aneuploidy could arise are postulated.

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.

scholarly journals Unrestrained Spindle Elongation during Recovery from Spindle Checkpoint Activation in cdc15-2 Cells Results in Mis-Segregation of Chromosomes

2010 ◽  
Vol 21 (14) ◽  
pp. 2384-2398 ◽  
Author(s):  
Chuan Chung Chai ◽  
Ee Mei Teh ◽  
Foong May Yeong
Keyword(s):  
Spindle Assembly Checkpoint ◽  
Spindle Checkpoint ◽  
Spindle Assembly ◽  
Spindle Pole ◽  
Checkpoint Activation ◽  
Sister Chromatids ◽  
Spindle Pole Bodies ◽  
Balance Of Forces ◽  
Spindle Elongation ◽  
Pulling Force

During normal metaphase in Saccharomyces cerevisiae, chromosomes are captured at the kinetochores by microtubules emanating from the spindle pole bodies at opposite poles of the dividing cell. The balance of forces between the cohesins holding the replicated chromosomes together and the pulling force from the microtubules at the kinetochores result in the biorientation of the sister chromatids before chromosome segregation. The absence of kinetochore–microtubule interactions or loss of cohesion between the sister chromatids triggers the spindle checkpoint which arrests cells in metaphase. We report here that an MEN mutant, cdc15-2, though competent in activating the spindle assembly checkpoint when exposed to Noc, mis-segregated chromosomes during recovery from spindle checkpoint activation. cdc15-2 cells arrested in Noc, although their Pds1p levels did not accumulate as well as in wild-type cells. Genetic analysis indicated that Pds1p levels are lower in a mad2Δ cdc15-2 and bub2Δ cdc15-2 double mutants compared with the single mutants. Chromosome mis-segregation in the mutant was due to premature spindle elongation in the presence of unattached chromosomes, likely through loss of proper control on spindle midzone protein Slk19p and kinesin protein, Cin8p. Our data indicate that a slower rate of transition through the cell division cycle can result in an inadequate level of Pds1p accumulation that can compromise recovery from spindle assembly checkpoint activation.

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