Nuclear division and chromosome behavior during meiosis and ascosporogenesis in Pyricularia oryzae

1987 ◽  
Vol 65 (1) ◽  
pp. 112-123 ◽  
Author(s):  
Hei Leung ◽  
P. H. Williams
Keyword(s):  
Magnaporthe Grisea ◽  
Nuclear Division ◽  
Spindle Pole ◽  
Pyricularia Oryzae ◽  
Maximum Diameter ◽  
Chromosome Movement ◽  
Chromosome Behavior ◽  
Electron Microscopic ◽  
Homologous Chromosomes ◽  
Spindle Pole Bodies

Meiosis and mitoses during ascosporogenesis in fertile mating strains of Pyricularia oryzae Cavara (teleomorph: Magnaporthe grisea) were studied using a propionic–iron–hematoxylin procedure which stained chromosomes, nucleolus, and spindle pole bodies. Meioses and mitoses in P. oryzae resembled those in other ascomycetes. Zygotene chromosomes were highly contracted followed by elongation at pachytene when close pairings of homologous chromosomes were observed. Nucleoli attained a maximum diameter of 3.8 μm during pachytene. Nucleolar growth was accompanied by a rapid growth of the ascus. Chromosome lengths varied among pachytene cells, with the longest chromosome averaging 8.5 and the smallest 2.9 μm. Telomeric knobs and chromomeres were discernible on fully extended pachytene chromosomes. Six chromosomes were observed at pachytene and diakinesis, and during metaphase of ascospore mitosis. Chromosome movement at meiotic and mitotic anaphase was asynchronous, resulting in lagging chromosomes. Electron microscopic observations revealed spindle pole bodies associated with profusion and early meiotic prophase nuclei. In pachytene nuclei, 50 nm wide structures resembling synaptonemal complexes were observed.

Somatic nuclear division in the sporidia of Ustilago violacea. III. Ultrastructural observations

1976 ◽  
Vol 22 (4) ◽  
pp. 495-506 ◽  
Author(s):  
N. H. Poon ◽  
A. W. Day
Keyword(s):  
Daughter Cell ◽  
Daughter Nucleus ◽  
Nuclear Division ◽  
Spindle Pole ◽  
The Other ◽  
Parent Cell ◽  
Electron Microscopic ◽  
Ustilago Violacea ◽  
Left Behind ◽  
Spindle Pole Bodies

The paper provides detailed ultrastructural observations on nuclear division in the smut fungus Ustilago violacea and is based on previous light-microscopic work outlining the division in living and stained cells. The division as in many other Basidiomycetes is not intranuclear, but occurs within a partially disrupted membrane. The division takes place after migration of most of the nucleus into the bud cell, after limited breakdown of the nuclear membrane, and after the formation of a spindle between two spindle-pole bodies (SPB). The remaining part of the nucleus containing the nucleolus is left behind in the parent cell and degenerates there. The SPB, as in other Basidiomycetes, is a dome-shaped relatively structureless body, quite distinct from the flat plaques of many Ascomycetes and the elaborate centrioles of Phycomycetes. The SPB divides shortly before migration into the daughter cell and invariably is located at the apex of the migrating nucleus. Nuclear division is completed when the two masses of chromatin clustered about each of the SPB's are separated as the spindle elongates. One daughter nucleus reforms in the bud and the other is reformed in the mother cell.Cells fixed and stained by conventional light-microscopic methods were examined in the light of the electron-microscopic observations to determine whether these procedures induce artefacts. Aceto-orcein and Giemsa when used cold were found to produce relatively artefact-free preparations. However, previous results in which the cells were warmed gently in these stains are now seen to contain artefacts in the form of contracted chromatinic granules often arranged in chains. These artefacts may provide useful information but clearly they must be interpreted cautiously until the nature of the changes induced by heating are known.

scholarly journals Requirement for ESP1 in the nuclear division of Saccharomyces cerevisiae.

1992 ◽  
Vol 3 (12) ◽  
pp. 1443-1454 ◽  
Author(s):  
J T McGrew ◽  
L Goetsch ◽  
B Byers ◽  
P Baum
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Normal Cell ◽  
Cell Cycle Progression ◽  
Nuclear Division ◽  
Flow Cytometric Analysis ◽  
Spindle Pole ◽  
Spindle Pole Bodies ◽  
Mutant Cells ◽  
Normal Cell Cycle

Mutations in the ESP1 gene of Saccharomyces cerevisiae disrupt normal cell-cycle control and cause many cells in a mutant population to accumulate extra spindle pole bodies. To determine the stage at which the esp1 gene product becomes essential for normal cell-cycle progression, synchronous cultures of ESP1 mutant cells were exposed to the nonpermissive temperature for various periods of time. The mutant cells retained viability until the onset of mitosis, when their viability dropped markedly. Examination of these cells by fluorescence and electron microscopy showed the first detectable defect to be a structural failure in the spindle. Additionally, flow cytometric analysis of DNA content demonstrated that massive chromosome missegregation accompanied this failure of spindle function. Cytokinesis occurred despite the aberrant nuclear division, which often resulted in segregation of both spindle poles to the same cell. At later times, the missegregated spindle pole bodies entered a new cycle of duplication, thereby leading to the accumulation of extra spindle pole bodies within a single nucleus. The DNA sequence predicts a protein product similar to those of two other genes that are also required for nuclear division: the cut1 gene of Schizosaccharomyces pombe and the bimB gene of Aspergillus nidulans.

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 Mitosis in the fission yeast Schizosaccharomyces pombe as revealed by freeze-substitution electron microscopy

1986 ◽  
Vol 80 (1) ◽  
pp. 253-268
Author(s):  
K. Tanaka ◽  
T. Kanbe
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Mitotic Spindle ◽  
Nuclear Division ◽  
Freeze Substitution ◽  
Spindle Pole ◽  
Nuclear Space ◽  
Spindle Pole Bodies ◽  
Transmission Electron ◽  
Cytoplasmic Microtubules ◽  
Spindle Microtubules

Nuclear division in Schizosaccharomyces pombe has been studied in transmission electron micrographs of sections of cells fixed by a method of freeze-substitution. We have found cytoplasmic microtubules in the vicinity of the spindle pole bodies and two kinds of microtubules, short discontinuous ones and long, parallel ones in the intranuclear mitotic spindle. For most of the time taken by nuclear division the spindle pole bodies face each other squarely across the nuclear space but early in mitosis they briefly appear twisted out of alignment with each other, thereby imparting a sigmoidal shape to the bundle of spindle microtubules extending between them. This configuration is interpreted as indicating active participation of the spindle in the initial elongation of the dividing nucleus. It is proposed that mitosis is accompanied by the shortening of chromosomal microtubules simultaneously with the elongation of the central pole-to-pole bundle of microtubules of the intranuclear spindle. Daughter nuclei are separated by the sliding apart of interdigitating microtubules of the spindle at telophase. Some of the latter bear dense knobs at their ends.

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.

Hypersensitive death, autofluorescence, and ultrastructural changes in cells of leaf sheaths of susceptible and resistant near-isogenic lines of rice (Pi-zt) in relation to penetration and growth of Pyricularia oryzae

1994 ◽  
Vol 72 (10) ◽  
pp. 1463-1477 ◽  
Author(s):  
Hlronori Koga
Keyword(s):  
Cell Death ◽  
Cell Walls ◽  
Magnaporthe Grisea ◽  
Pyricularia Oryzae ◽  
Ultrastructural Changes ◽  
Near Isogenic Lines ◽  
Resistant Line ◽  
Electron Microscopic ◽  
Hypersensitive Cell Death ◽  
Isogenic Lines

Leaf sheaths of susceptible and resistant (Pi-zt) near-isogenic lines of rice were inoculated with Pyricularia oryzae (Magnaporthe grisea) and the host – parasite interactions in living tissues were continuously observed using fluorescence and bright field microscopy. Growth of invading hyphae in the resistant line was restricted within cells that underwent hypersensitive death during fungal penetration. Experiments using heat shock and NaAsO2 treatments suggested that cell death alone is not responsible for restriction of hyphal growth within the penetrated cell. Fungal hyphae grew unimpeded in dead cells of treated tissue unless the dead cells had also developed the capacity to autofluoresce under blue light. Electron microscopic studies showed that hypersensitive cell death occurred specifically in the resistant line after penetration of the cuticle, and in some cases it occurred before cell walls were completely penetrated. In the susceptible line, wall appositions were induced in the epidermal cells at a similar stage of fungal penetration (i.e., before infection hyphae had reached the cell lumen). Inward indentation of the cuticle and cell wall and inward folding of the cuticle at the penetration site suggested that the cuticle was breached mechanically. Wall penetration appeared to be facilitated by enzyme action because the microfibrils of host cell walls around infection pegs were disorganized and nonhomogeneous in electron density. Key words: resistance, penetration, ultrastructure, autofluorescence, rice blast, Pyricularia oryzae (Magnaporthe grisea).

A light and electron microscopic study of mitosis in the clamp connection of Auricularia auricula-judae

1995 ◽  
Vol 73 (2) ◽  
pp. 315-332 ◽  
Author(s):  
Haisheng Lü ◽  
David J. McLaughlin
Keyword(s):  
Electron Microscopy ◽  
Nuclear Division ◽  
Spindle Pole Body ◽  
Microscopic Analysis ◽  
Freeze Substitution ◽  
Spindle Pole ◽  
Sensu Stricto ◽  
Mitotic Division ◽  
Electron Microscopic ◽  
Auricularia Auricula

Nuclear behavior and mitotic division in living and fixed somatic hyphae of Auricularia auricula-judae were studied with phase-contrast, fluorescence, and electron microscopy to clarify the process of mitosis in Auriculariales sensu stricto for cytological and phylogenetic analysis. Both conventional chemical fixation and freeze-substitution methods were employed for electron microscopic analysis. Mitotic division began when one of the two nuclei was moving into the clamp and lasted about 12 – 18 min. The spindle pole body had an electron-opaque central core surrounded by an electron-transparent zone from prometaphase to anaphase. The spindle changed the orientation of its long axis from a position parallel to the long axis of the clamp or hypha in prometaphase, to an oblique position in early metaphase, and finally to a parallel position again in midmetaphase. The nuclear envelope was disrupted in prometaphase to early metaphase and showed discontinuity at both polar and central regions in late anaphase; however, in metaphase it was intact with polar fenestrations. Nuclear division in the dikaryotic hypha was asynchronous. The data obtained from mitosis in A. auricula-judae support a close relationship of Auriculariales s.str. with homobasidiomycetes. The phylogenetic significance of the nuclear division characters is analyzed. Key words: Auricularia auricula-judae, electron microscopy, light microscopy, mitosis, phylogeny.

scholarly journals Evidence for anaphase pulling forces during C. elegans meiosis

2020 ◽  
Vol 219 (12) ◽  
Author(s):  
Brennan M. Danlasky ◽  
Michelle T. Panzica ◽  
Karen P. McNally ◽  
Elizabeth Vargas ◽  
Cynthia Bailey ◽  
...  
Keyword(s):  
Spindle Pole ◽  
Outer Face ◽  
Chromosome Movement ◽  
Female Meiosis ◽  
Homologous Chromosomes ◽  
C Elegans ◽  
Spindle Poles ◽  
Pulling Forces ◽  
Spindle Elongation ◽  
Anaphase B

Anaphase chromosome movement is thought to be mediated by pulling forces generated by end-on attachment of microtubules to the outer face of kinetochores. However, it has been suggested that during C. elegans female meiosis, anaphase is mediated by a kinetochore-independent pushing mechanism with microtubules only attached to the inner face of segregating chromosomes. We found that the kinetochore proteins KNL-1 and KNL-3 are required for preanaphase chromosome stretching, suggesting a role in pulling forces. In the absence of KNL-1,3, pairs of homologous chromosomes did not separate and did not move toward a spindle pole. Instead, each homolog pair moved together with the same spindle pole during anaphase B spindle elongation. Two masses of chromatin thus ended up at opposite spindle poles, giving the appearance of successful anaphase.

Chromosome behavior in living cells and the electron microscopy of chromosome attachment to the spindle

1983 ◽  
Vol 41 ◽  
pp. 548-551
Author(s):  
D. F. Kubai ◽  
R. B. Nicklas
Keyword(s):  
Homologous Chromosome ◽  
Meiotic Chromosome ◽  
Spindle Pole ◽  
Chromosome Movement ◽  
Chromosome Behavior ◽  
Daughter Cells ◽  
Chromosome Distribution ◽  
Chromosome Attachment

During mitosis and meiosis, chromosomes are distributed to daughter cells in controlled fashion, with patterns of chromosome distribution determined by specific interactions between chromosomes and the microtubules composing the spindle. In meiosis, for example, homologous chromosome pairs (bivalents) attach to the spindle so that the kinetochore of one chromosome of the pair is associated with kinetochore microtubules extending toward one spindle pole while the kinetochore-associated microtubules of the partner chromosome extend toward the opposite pole. This arrangement assures that partner chromosomes proceed in opposite directions during anaphase chromosome movement and results in the delivery of only one member of the homologous chromosome pair to each daughter cell. This sort of descriptive/mechanical account of mitotic and meiotic chromosome behavior is now well-established. However, total understanding of the role of the spindle in precise chromosome distribution demands a much more detailed analysis of spindle organization than is yet available. For instance, determination of where and how the innumerable microtubules of the spindle are mechanically linked should help to clarify exactly where forces for chromosome movement are applied.

Morphology and ultrastructure of a protistan pathogen in the haemolymph of shrimp (Pandalus spp.) in the northeastern Pacific Ocean

2002 ◽  
Vol 80 (6) ◽  
pp. 1055-1068 ◽  
Author(s):  
Susan M Bower ◽  
Gary R Meyer
Keyword(s):  
Nuclear Membrane ◽  
Nuclear Division ◽  
Spindle Pole ◽  
Secondary Sexual Characteristics ◽  
Spindle Pole Bodies ◽  
Sexual Characteristics ◽  
Northeastern Pacific ◽  
Superficial Similarity ◽  
Taxonomic Affiliation ◽  
Parasitic Dinoflagellates

A eukaryotic parasite of uncertain taxonomic affiliation, with superficial similarity to parasitic dinoflagellates (large plasmodia and numerous trophonts) but a different mechanism of nuclear division and a lack of organelles characteristic of parasitic dinoflagellates, is described from spot prawns (Pandalus platyceros). Up to 20% of the spot prawns examined from Malaspina Strait, British Columbia, were infected. Infections in the majority of the prawns were cryptic (asymptomatic) but of sufficient duration to affect secondary sexual characteristics and castrate the host. Cryptic infections consisted of plasmodia containing numerous nuclei. The plasmodia were observed in the haemal sinuses of all tissues. In mature plasmodia the nuclei stopped dividing and showed a peripheral chromatin ring, an internal chromatin web, and up to three tiny nucleoli. Mature plasmodia divided into numerous uninucleate trophonts, resulting in symptoms of lethargy, orange discoloration, and milky haemolymph caused by a plethora of either spherical or discoid trophonts. Symptomatic infections of the prawns fished with traps rarely exceeded 2%. In 3 of the 156 symptomatic prawns examined, about 30% of the trophonts were in the process of binary fission. During mitosis the nuclear membrane was persistent, but openings (about 0.8 µm in width) at either pole accommodated emergent spindle-pole bodies to which the few chromosomes were attached by microtubules. Attempts to transmit the infection between prawns in the laboratory were unsuccessful.

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