Nuclear divisions at meiosis in the ascomycetous yeast Wickerhamia fluorescens

1973 ◽  
Vol 19 (11) ◽  
pp. 1383-1387 ◽  
Author(s):  
Lynn Rooney ◽  
Peter B. Moens
Keyword(s):  
Nuclear Envelope ◽  
Developmental Stages ◽  
Spindle Pole ◽  
The Other ◽  
Sporulation Medium ◽  
Serial Sections ◽  
Yeast Saccharomyces Cerevisiae ◽  
Ascomycetous Yeast ◽  
Spindle Pole Bodies ◽  
A Chain

In cultures of cells which have been on sporulation medium for 22 h, all stages of meiosis and sporulation occur. In electron microscopy of glutaraldehyde-fixed cells, spindles and spindle-pole bodies are preserved but chromosomes and kinetochores are not apparent. Photographic records of complete serial sections of some 40 asci in different developmental stages show that during the first meiotic division, the nuclear envelope remains intact and the spindle elongates from about 1 μm to 4 μm. Each of the spindle-pole bodies then divides and the bilobed nucleus contains two short spindles (one in each lobe). During the second division the spindles elongate from about 0.5 μm to 3.5 μm while the nuclear envelope remains intact. As a result there is a four-lobed nucleus, either in a chain formation or in a more compact arrangement. The spindle-pole bodies increase in complexity to varying degrees during the second division. One becomes the organizer of a complete ascospore wall while the other three may develop an incomplete wall and eventually these three nuclei degenerate in the cytoplasm of the ascus. It is shown that the nuclear behavior during meiosis parallels that of the yeast Saccharomyces cerevisiae but differs from that reported for Euascomycetes.

scholarly journals The Spindle Pole Bodies Facilitate Nuclear Envelope Division during Closed Mitosis in Fission Yeast

PLoS Biology ◽  
2007 ◽  
Vol 5 (7) ◽  
pp. e170 ◽  
Author(s):  
Liling Zheng ◽  
Cindi Schwartz ◽  
Valentin Magidson ◽  
Alexey Khodjakov ◽  
Snezhana Oliferenko
Keyword(s):  
Nuclear Envelope ◽  
Fission Yeast ◽  
Spindle Pole ◽  
Spindle Pole Bodies

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 The Three Fungal Transmembrane Nuclear Pore Complex Proteins of Aspergillus nidulans Are Dispensable in the Presence of an Intact An-Nup84-120 Complex

2009 ◽  
Vol 20 (2) ◽  
pp. 616-630 ◽  
Author(s):  
Hui-Lin Liu ◽  
Colin P.C. De Souza ◽  
Aysha H. Osmani ◽  
Stephen A. Osmani
Keyword(s):  
High Temperature ◽  
Nuclear Envelope ◽  
Aspergillus Nidulans ◽  
Nuclear Pore Complex ◽  
Mitotic Spindle ◽  
Spindle Pole ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Spindle Pole Bodies ◽  
Pore Complexes

In Aspergillus nidulans nuclear pore complexes (NPCs) undergo partial mitotic disassembly such that 12 NPC proteins (Nups) form a core structure anchored across the nuclear envelope (NE). To investigate how the NPC core is maintained, we affinity purified the major core An-Nup84-120 complex and identified two new fungal Nups, An-Nup37 and An-ELYS, previously thought to be vertebrate specific. During mitosis the An-Nup84-120 complex locates to the NE and spindle pole bodies but, unlike vertebrate cells, does not concentrate at kinetochores. We find that mutants lacking individual An-Nup84-120 components are sensitive to the membrane destabilizer benzyl alcohol (BA) and high temperature. Although such mutants display no defects in mitotic spindle formation, they undergo mitotic specific disassembly of the NPC core and transient aggregation of the mitotic NE, suggesting the An-Nup84-120 complex might function with membrane. Supporting this, we show cells devoid of all known fungal transmembrane Nups (An-Ndc1, An-Pom152, and An-Pom34) are viable but that An-ndc1 deletion combined with deletion of individual An-Nup84-120 components is either lethal or causes sensitivity to treatments expected to destabilize membrane. Therefore, the An-Nup84-120 complex performs roles, perhaps at the NPC membrane as proposed previously, that become essential without the An-Ndc1 transmembrane Nup.

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 Progression Into the First Meiotic Division Is Sensitive to Histone HN-HZB Dimer Concentration in Saccharomyces cerevisiae

Genetics ◽  
1997 ◽  
Vol 145 (3) ◽  
pp. 647-659
Author(s):  
Kochung Tsui ◽  
Lee Simon ◽  
David Norris
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Meiotic Division ◽  
Expression Patterns ◽  
Spindle Pole ◽  
Chain Elongation ◽  
Histone H2a ◽  
Yeast Saccharomyces Cerevisiae ◽  
Spindle Pole Bodies ◽  
Dna Chain ◽  
Mitosis And Meiosis

The yeast Saccharomyces cerevisiae contains two genes for histone H2A and two for histone H2B located in two divergently transcribed gene pairs: HTA1-HTB1 and HTA2-HTB2. Diploid strains lacking HTA1-HTB1 (hta1-htb1Δ/hta1-htb1Δ, HTA2-HTB2/HTA2-HTB2) grow vegetatively, but will not sporulate. This sporulation phenotype results from a partial depletion of H2A-H2B dimers. Since the expression patterns of HTA1-HTB1 and HTA2-HTB2 are similar in mitosis and meiosis, the sporulation pathway is therefore more sensitive than the mitotic cycle to depletion of H2A-H2B dimers. After completing premeiotic DNA replication, commitment to meiotic recombination, and chiasma resolution, the hta1-htb1Δ/hta1-htb1Δ, HTA2-HTB2/HTA2-HTB2 mutant arrests before the first meiotic division. The arrest is not due to any obvious disruptions in spindle pole bodies or microtubules. The meiotic block is not bypassed in backgrounds homozygous for spo13, rad50Δ, or rad9Δ mutations, but is bypassed in the presence of hydroxyurea, a drug known to inhibit DNA chain elongation. We hypothesize that the deposition of H2A-H2B dimers in the mutant is unable to keep pace with the replication fork, thereby leading to a disruption in chromosome structure that interferes with the meiotic divisions.

Chromatin behaviour during the mitotic cell cycle of Saccharomyces cerevisiae

1977 ◽  
Vol 24 (1) ◽  
pp. 81-93
Author(s):  
C.N. Gordon
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Division ◽  
Mitotic Cell ◽  
Spindle Pole ◽  
Chromosomal Distribution ◽  
Yeast Saccharomyces Cerevisiae ◽  
Thin Sections ◽  
Daughter Cells ◽  
Spindle Pole Bodies ◽  
Direct Attachment

Chromatin behaviour during the cell division cycle of the yeast Saccharomyces cerevisiae has been investigated in cells which have been depleted of 90% of their RNA by digestion with ribonuclease. Removal of large amounts of RNA from the yeast nucleus before treatment of the cells with heavy metal fixatives and stains permits chromatin to be visualized with extreme clarity in thin sections of cells processed for electron microscopy by conventional procedures. Spindle pole bodies were also visualized by this treatment, although the associated microtubules were not. Chromatin is dispersed during interphase and occupies the non-nucleolar region of the nucleus which is known to be Feulgen-positive from light microscopy. Because spindle microtubules are not visualized, direct attachment of microtubules to chromatin fibrils could not be verified. However, chromatin was not attached directly to the spindle pole bodies and kinetochore differentiations were not observed in the nucleoplasm. During nuclear division chromatin remains dispersed and does not condense into discrete chromatids. As the nucleus expands into the bud, chromosomal distribution to the daughter cells is thought to result from the separation of the poles of the spindle apparatus with attached chromatin fibrils. However, that such distribution is occurring as the nucleus elongates is not obvious until an advanced stage of nuclear division is reached and partition of the nucleus is nearly complete. Thus, no aggregation of chromatin into metaphase or anaphase plates occurs and the appearance of chromatin during mitosis is essentially the same as in interphase. These observations indicate that the marked changes in the topological structure of chromatin which characterize mitosis in the higher eukaryotes do not occur in S. cerevisiae.

The role of spindle pole bodies and modified microtubule ends in the initiation of microtubule assembly in Saccharomyces cerevisiae

1978 ◽  
Vol 30 (1) ◽  
pp. 331-352 ◽  
Author(s):  
B. Byers ◽  
K. Shriver ◽  
L. Goetsch
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Spindle Pole ◽  
Microtubule Assembly ◽  
Structural Differentiation ◽  
Yeast Saccharomyces Cerevisiae ◽  
Microtubule Polymerization ◽  
Spindle Pole Bodies ◽  
Osmotic Lysis

The spindle poles of the budding yeast, Saccharomyces cerevisiae, have been removed from mitotic and meiotic cells by osmotic lysis of spheroplasts. The spindle pole bodies (SPBs)—diskoidal structures also termed ‘spindle plaques’—have been analysed for their ability to potentiate the polymerization of microtubules in vitro. Free SPBs were completely deprived of any detectable native microtubules by incubation in the absence of added tubulin and were then challenged with chick neurotubulin, which had been rendered partially defective in self-initiation of repolymerization. Electron microscopy revealed that these SPBs served as foci for the initiation of microtubule polymerization in vitro. Because the attached microtubules elongated linearly with time but did not increase in numbers after the first stage of the reaction, it is apparent that there are a limited number of sites for initiation. The initiating potential of the SPBs was found to be inhibited by enzymic hydrolysis of protein but not of DNA. The microtubule end proximal to the site of initiation on the SPB is distinguished by a ‘closed’ appearance because of a terminal component which is continuous with the microtubule wall, whereas the distal end has the ‘open’ appearance characteristic of freely repolymerized neurotubules. SPBs which were partially purified on sucrose gradients retained their ability to initiate the assembly of microtubules with the same structural differentiation of their ends. The occurrence of closed proximal ends on native yeast microtubules suggests that closed ends may play a role in the initiation of microtubule polymerization in vivo, as well as in vitro.

Yeast-Like Endosymbionts in an Ichneumonid Wasp

1984 ◽  
Vol 39 (3-4) ◽  
pp. 322-326 ◽  
Author(s):  
J. Middeldorf ◽  
A. Ruthmann
Keyword(s):  
Nuclear Envelope ◽  
Spindle Pole ◽  
Next Generation ◽  
Vegetative Cells ◽  
Host Cytoplasm ◽  
Spindle Pole Bodies ◽  
Pathogenic Infection

Vegetative cells and spores of a yeast-like micro organism found in various tissues in both sexes of the ichneumonid wasp Pimpla turionellae are passed to the offspring by infection of the oocytes. Because of their intranuclearspindles with spindle pole bodies associated with the nuclear envelope as pole structures, the microorganisms are thought to be yeasts or closely related to yeasts. The high vitality and fertility of the wasps seem to exclude a pathogenic infection. Both the passage of vesicles from the microorganisms to the host cytoplasm and their transmission to the next generation by the oocytes point to anendosymbiotic relationship

scholarly journals Nuclear Pore Complex Number and Distribution throughout theSaccharomyces cerevisiaeCell Cycle by Three-Dimensional Reconstruction from Electron Micrographs of Nuclear Envelopes

1997 ◽  
Vol 8 (11) ◽  
pp. 2119-2132 ◽  
Author(s):  
Mark Winey ◽  
Defne Yarar ◽  
Thomas H. Giddings ◽  
David N. Mastronarde
Keyword(s):  
Cell Cycle ◽  
Nuclear Envelope ◽  
Electron Micrographs ◽  
Three Dimensional ◽  
Spindle Pole ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Nuclear Surface ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cell Cycle Stage

The number of nuclear pore complexes (NPCs) in individual nuclei of the yeast Saccharomyces cerevisiae was determined by computer-aided reconstruction of entire nuclei from electron micrographs of serially sectioned cells. Nuclei of 32 haploid cells at various points in the cell cycle were modeled and found to contain between 65 and 182 NPCs. Morphological markers, such as cell shape and nuclear shape, were used to determine the cell cycle stage of the cell being examined. NPC number was correlated with cell cycle stage to reveal that the number of NPCs increases steadily, beginning in G1-phase, suggesting that NPC assembly occurs continuously throughout the cell cycle. However, the accumulation of nuclear envelope observed during the cell cycle, indicated by nuclear surface area, is not continuous at the same rate, such that the density of NPCs per unit area of nuclear envelope peaks in apparent S-phase cells. Analysis of the nuclear envelope reconstructions also revealed no preferred NPC-to-NPC distance. However, NPCs were found in large clusters over regions of the nuclear envelope. Interestingly, clusters of NPCs were most pronounced in early mitotic nuclei and were found to be associated with the spindle pole bodies, but the functional significance of this association is unknown.

The fine structure of ascospore delimitation in the yeast Wickerhamia fluorescens

1973 ◽  
Vol 19 (11) ◽  
pp. 1389-1392 ◽  
Author(s):  
Lynn Rooney ◽  
Peter B. Moens
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fine Structure ◽  
Outer Membrane ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Spore Wall ◽  
Serial Sections ◽  
Spore Body ◽  
Pole Body ◽  
Spindle Pole Bodies

Photographic records of complete serial sections of asci in different stages of sporulation show that one of the four nuclear lobes produced during meiosis in the ascus of the yeast Wickerhamia fluorescens has a complex spindle-pole body, which is the site from where the presumptive ascospore wall, or prospore wall, develops and eventually surrounds the ascospore nucleus and associated cytoplasm. The three remaining nuclei develop spindle-pole bodies and prospore walls to lesser and varying degrees. With few exceptions, all three degenerate. The outer membrane of the prospore wall forms a fold, or rim, on the outside of the spore. Thickening of the spore wall takes place first in the asymmetric ring, then around the spore body, and finally at the site where the nucleus is associated with the wall. It is shown that ascospore delimitation in W. fluorescens and Saccharomyces cerevisiae are similar to each other, and that it differs from the type observed in a number of Euascomycetes.

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