Observations on the Fine Structure and Development of the Spindle at Mitosis and Meiosis in a Marine Centric Diatom (Lithodesmium Undulatum)

1970 ◽  
Vol 7 (2) ◽  
pp. 407-443
Author(s):  
IRENE MANTON ◽  
K. KOWALLIK ◽  
H. A. VON STOSCH
Keyword(s):  
Centric Diatom ◽  
Serial Sections ◽  
Late Prophase ◽  
Haploid Chromosome Number ◽  
Male Gametogenesis ◽  
Common Time ◽  
Precursor Material ◽  
Mitosis And Meiosis ◽  
Meiosis I ◽  
Unusual Shape

The second meiotic division is shown to be of critical importance for interpretation of structures and events already seen at other divisions. The development of flagellar bases at interkinesis is demonstrated in relation to precursor material seen to accumulate near each pole at meiosis I. The name ‘paracentrosome’ is suggested for this material, which is used up in forming the flagellar bases and spindle precursor. The spindle at late prophase, metaphase and telophase II is shown to resemble those of other divisions except that it is consistently smaller; this fact is numerically demonstrated from serial sections of metaphase II cells. The greatly reduced size and unusual shape of the polar plates present in addition to flagellar bases at metaphase II suggest that these are in a sense equivalent structures with a mutually competitive relation to the paracentrosome. Preliminary observations with the light microscope on the relatively large nuclei of oogonia during meiosis I have shown that the haploid chromosome number is not less than 19 nor more than 23 and that chromatid separation in relation to the kinetochores at anaphase I is normal; the bearing of these findings on interpretation of the spindle is discussed. Comparisons with other organisms are carried out in a preliminary way and the investigation ends with a résumé of the more important externally visible events in male gametogenesis adjusted to a common time scale in the course of one day.

Observations on the Fine Structure and Development of the Spindle at Mitosis and Meiosis in a Marine Centric Diatom (Lithodesmium Undulatum)

1969 ◽  
Vol 5 (1) ◽  
pp. 271-298
Author(s):  
IRENE MANTON ◽  
K. KOWALLIK ◽  
H. A. VON STOSCH
Keyword(s):  
Fine Structure ◽  
Chromosome Structure ◽  
Centric Diatom ◽  
Serial Sections ◽  
Ground Plan ◽  
Living Culture ◽  
Full Discussion ◽  
Two Stages ◽  
Mitosis And Meiosis ◽  
Spindle Structure

Various cytoplasmic phenomena, including spindle structure and development during prophase of the first meiotic division, are described and illustrated. The living culture is represented by a timed sequence of photographs continuing those previously published with respect to mitotic stages in the same filament. The meiotic preliminaries include the so-called swelling phase, by which the parental frustule is forced open, liberating the contained spermatocytes. This occurs during pachytene on evidence of chromosome structure which is illustrated. A spindle precursor is shown to be present before opening of the frustule; this resembles structurally the mitotic equivalent though the ground plan is oblong instead of square. Growth of the precursor continues until after opening of the frustule, when the spindle itself begins to be laid down. Two stages of developing spindles during the later prophases are illustrated by sections cut in three planes and by serial sections. Preliminary comparisons are made with metaphase I and with mitosis, both qualitatively and quantitatively, but a full discussion is deferred pending completion of the record for the later meiotic stages.

Observations on the fine structure and development of the spindle at mitosis and meiosis in a marine centric diatom (Lithodesmium Undulatum)

1970 ◽  
Vol 6 (1) ◽  
pp. 131-156
Author(s):  
IRENE MANTON ◽  
K. KOWALLIK ◽  
H. A. VON STOSCH
Keyword(s):  
Living Cells ◽  
Slight Variation ◽  
Centric Diatom ◽  
Serial Sections ◽  
Spindle Microtubules ◽  
Physical Forces ◽  
First Time ◽  
Mitosis And Meiosis ◽  
Chromosome Movements ◽  
Different Parts

Numerical information with respect to spindle microtubules in serial sections of 3 cells at metaphase of the first meiotic division has been compiled and illustrated sufficiently to supplement the previous accounts with respect to both longitudinal and transverse views. At the equator the microtubules of the spindle are united laterally into bundles, the number of bundles being of the same order as that encountered at a premeiotic mitosis, though there is slight variation from cell to cell. The number of microtubules is greater than that at mitosis in a normal spermatogonium, though the distribution in different parts of the spindle is qualitatively similar. Stages of anaphase have been illustrated for the first time and shown to involve at least types of physical forces mediating chromosome movements of various kinds. The later stages of cytokinesis have been timed and are illustrated from living cells and from sections. The relation of the spindle to the cord which unites the separating protoplasts towards the end of cytokinesis has been traced in outline. The cord itself is shown to contain micro- tubules in limited number and it is therefore not the whole spindle. The interpretation of these findings is discussed in a preliminary way.

scholarly journals Klp2 and Ase1 synergize to maintain meiotic spindle stability during metaphase I

2020 ◽  
Author(s):  
Fan Zheng ◽  
Fenfen Dong ◽  
Shuo Yu ◽  
Tianpeng Li ◽  
Yanze Jian ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Yeast Cells ◽  
Meiotic Spindle ◽  
Homologous Chromosomes ◽  
Spindle Dynamics ◽  
Live Cell Microscopy ◽  
Spindle Stability ◽  
Cell Microscopy ◽  
Mitosis And Meiosis ◽  
Meiosis I

ABSTRACTThe spindle apparatus segregates bi-oriented sister chromatids during mitosis but mono-oriented homologous chromosomes during meiosis I. It has remained unclear if similar molecular mechanisms operate to regulate spindle dynamics during mitosis and meiosis I. Here, we employed live-cell microscopy to compare the spindle dynamics of mitosis and meiosis I in fission yeast cells and demonstrated that the conserved kinesin-14 motor Klp2 plays a specific role in maintaining metaphase spindle length during meiosis I, but not during mitosis. Moreover, the maintenance of metaphase spindle stability during meiosis I requires the synergism between Klp2 and the conserved microtubule crosslinker Ase1 as the absence of both proteins causes exacerbated defects in metaphase spindle stability. The synergism is not necessary for regulating mitotic spindle dynamics. Hence, our work reveals a new molecular mechanism underlying meiotic spindle dynamics and provides insights into understanding differential regulation of meiotic and mitotic events.

scholarly journals The Maize Homologue of the Cell Cycle Checkpoint Protein MAD2 Reveals Kinetochore Substructure and Contrasting Mitotic and Meiotic Localization Patterns

1999 ◽  
Vol 145 (3) ◽  
pp. 425-435 ◽  
Author(s):  
Hong-Guo Yu ◽  
Michael G. Muszynski ◽  
R. Kelly Dawe
Keyword(s):  
Cell Cycle ◽  
Spindle Assembly ◽  
Cell Cycle Checkpoint ◽  
Checkpoint Protein ◽  
Microtubule Attachment ◽  
Checkpoint Pathway ◽  
Outer Domain ◽  
Cycle Checkpoint ◽  
Mitosis And Meiosis ◽  
Meiosis I

We have identified a maize homologue of yeast MAD2, an essential component in the spindle checkpoint pathway that ensures metaphase is complete before anaphase begins. Combined immunolocalization of MAD2 and a recently cloned maize CENPC homologue indicates that MAD2 localizes to an outer domain of the prometaphase kinetochore. MAD2 staining was primarily observed on mitotic kinetochores that lacked attached microtubules; i.e., at prometaphase or when the microtubules were depolymerized with oryzalin. In contrast, the loss of MAD2 staining in meiosis was not correlated with initial microtubule attachment but was correlated with a measure of tension: the distance between homologous or sister kinetochores (in meiosis I and II, respectively). Further, the tension-sensitive 3F3/2 phosphoepitope colocalized, and was lost concomitantly, with MAD2 staining at the meiotic kinetochore. The mechanism of spindle assembly (discussed here with respect to maize mitosis and meiosis) is likely to affect the relative contributions of attachment and tension. We support the idea that MAD2 is attachment-sensitive and that tension stabilizes microtubule attachments.

scholarly journals Spo13 prevents premature cohesin cleavage during meiosis

2019 ◽  
Vol 4 ◽  
pp. 29 ◽  
Author(s):  
Stefan Galander ◽  
Rachael E. Barton ◽  
David A. Kelly ◽  
Adèle L. Marston
Keyword(s):  
Regulatory Subunit ◽  
Homologous Chromosomes ◽  
Sister Chromatids ◽  
Functional Homolog ◽  
Sister Kinetochore ◽  
Phosphatase 2A ◽  
Cohesin Subunit ◽  
Yeast Meiosis ◽  
Mitosis And Meiosis ◽  
Meiosis I

Background: Meiosis produces gametes through two successive nuclear divisions, meiosis I and meiosis II. In contrast to mitosis and meiosis II, where sister chromatids are segregated, during meiosis I, homologous chromosomes are segregated. This requires the monopolar attachment of sister kinetochores and the loss of cohesion from chromosome arms, but not centromeres, during meiosis I. The establishment of both sister kinetochore mono-orientation and cohesion protection rely on the budding yeast meiosis I-specific Spo13 protein, the functional homolog of fission yeast Moa1 and mouse MEIKIN. Methods: Here we investigate the effects of loss of SPO13 on cohesion during meiosis I using a live-cell imaging approach. Results: Unlike wild type, cells lacking SPO13 fail to maintain the meiosis-specific cohesin subunit, Rec8, at centromeres and segregate sister chromatids to opposite poles during anaphase I. We show that the cohesin-destabilizing factor, Wpl1, is not primarily responsible for the loss of cohesion during meiosis I. Instead, premature loss of centromeric cohesin during anaphase I in spo13Δ cells relies on separase-dependent cohesin cleavage. Further, cohesin loss in spo13Δ anaphase I cells is blocked by forcibly tethering the regulatory subunit of protein phosphatase 2A, Rts1, to Rec8. Conclusions: Our findings indicate that separase-dependent cleavage of phosphorylated Rec8 causes premature cohesin loss in spo13Δ cells.

Meiosis-specific arrest revealed in DNA topoisomerase II mutants

1993 ◽  
Vol 13 (6) ◽  
pp. 3445-3455 ◽  
Author(s):  
D Rose ◽  
C Holm
Keyword(s):  
Electron Microscopy ◽  
Synaptonemal Complex ◽  
Topoisomerase Ii ◽  
Meiotic Chromosome ◽  
Dna Topoisomerase Ii ◽  
Wild Type ◽  
Dna Topoisomerase ◽  
Fluorescence And Electron Microscopy ◽  
Mitosis And Meiosis ◽  
Meiosis I

Although the processes of mitosis and meiosis are similar, there is evidence for fundamental regulatory differences between the two. To examine these differences, we have compared the meiotic phenotype of DNA topoisomerase II mutants with their previously described mitotic phenotype (C. Holm, T. Goto, J. Wang, and D. Botstein, Cell 41:553-563, 1985). top2 mutants in meiosis show no defects in the latest detectable stages of recombination, yet they arrest prior to spindle establishment at meiosis I. Fluorescence and electron microscopy reveal that top2 mutants exhibit wild-type levels of meiotic chromosome condensation and form morphologically normal synaptonemal complex but are delayed in the exit from pachytene. Arrested cells retain viability and form colonies if transferred to mitotic medium. Our results suggest that the top2 meiotic arrest is regulatory in nature. This arrest may have evolved to ensure the resolution of fortuitous tangles between nonhomologous chromosomes.

scholarly journals The external mechanics of the chromosomes III-Meiosis in triploids

1936 ◽  
Vol 121 (823) ◽  
pp. 290-300 ◽  
Keyword(s):  
Sexual Reproduction ◽  
Chromosome Pairing ◽  
Natural Experiment ◽  
Diploid Species ◽  
Homologous Chromosomes ◽  
Normal Series ◽  
Mitosis And Meiosis ◽  
Meiosis I ◽  
Prophase Of Meiosis ◽  
The Way

Triploid organisms have three homologous chromosomes of each kind instead of the two of diploids. The regular mechanism of heredity fails in these circumstances. The triploid is incapable of breeding true by sexual reproduction. But the way in which it carries out the process of chromosome pairing and segregation is of great significance. The processes take place in normal series, but the relationships they establish are abnormal. A triploid thus provides a natural experiment, with the diploid of its own species as a control for one variable, and with triploids of different species as controls for others. In Tulipa and Hyacinthus I have made use of this experiment for inducing the principles of the external mechanics of chromosomes during the prophase of meiosis. I have inferred from them the relationships between the forces working in mitosis and meiosis. The triploid forms of various Fritillaria species make it possible to test the principles of metaphase mechanics induced from observations on structural hybrids and other polyploids (Darlington, 1932, b , and 1933, c ) as well as from the exceptional behaviour in the diploid species of Fritillaria already discussed.

scholarly journals Meiosis in Sciara coprophila: structure of the spindle and chromosome behavior during the first meiotic division.

1982 ◽  
Vol 93 (3) ◽  
pp. 655-669 ◽  
Author(s):  
D F Kubai
Keyword(s):  
Chromosome Segregation ◽  
Chromosome Movement ◽  
Serial Sections ◽  
Chromosome Behavior ◽  
Monopolar Spindle ◽  
Prophase Nucleus ◽  
Fungus Gnat ◽  
Spindle Microtubules ◽  
Conical Radiation ◽  
Meiosis I

Light microscope descriptions of meiosis I in males of the fungus gnat Sciara coprophila suggested the presence of a monopolar spindle in which maternal and limited chromosomes move poleward while paternal chromosomes "back away" from the pole. The ultrastructural analysis reported here, based upon serial sections of cells in different stages of meiosis I, shows that the spindle is indeed monopolar with a distinctive differentiation, the polar complex, at one pole. This complex is the focus of a conical radiation of spindle microtubules. Kinetochores of paternal chromosomes face the complex and microtubules associated with these kinetochores run toward the complex. No kinetochore microtubules were discovered on maternal or limited chromosomes. When the position of paternal, maternal, and limited chromosomes is compared at various stages, it is found that limited chromosomes always remain near the polar complex, paternal chromosomes remain far from it and only maternal chromosomes move closer to the pole. Apparently, chromosome segregation does not depend on paternal chromosomes "backing away" from the pole, and the required movement of maternal chromosomes take place in the absence of kinetochore microtubules. In the prophase nucleus, limited and maternal chromosomes are already spatially separate from paternal chromosomes before the spindle forms. Thus, the monopolar spindle functions only to increase the distance between already segregated sets of chromosomes. An extensive system of microtubule-associated membranes outlines the spindle; the possibility that maternal chromosome movement is somehow related to the presence of this membrane is discussed.

An uncommon H3/Ser10 phosphorylation pattern in Cestrum strigilatum (Solanaceae), a species with B chromosomes

Genome ◽  
2008 ◽  
Vol 51 (9) ◽  
pp. 772-777 ◽  
Author(s):  
Thiago Fernandes ◽  
Priscila Mary Yuyama ◽  
Ana Paula Moraes ◽  
André Luís Laforga Vanzela
Keyword(s):  
Histone H3 ◽  
Pericentromeric Region ◽  
B Chromosomes ◽  
South American ◽  
Terminal Portion ◽  
Mendelian Segregation ◽  
Cell Divisions ◽  
Phosphorylation Pattern ◽  
Mitosis And Meiosis ◽  
Meiosis I

Cestrum strigilatum (Solanaceae) is a South American shrub with B chromosomes. Bs show a univalent behavior when a single B is present, have non-Mendelian segregation, and are poor in genes and rich in repetitive DNA. In this study, the histone H3 at serine 10 (H3/Ser10) phosphorylation pattern was investigated during mitosis and meiosis of C. strigilatum collected from the wild and was compared in A and B chromosomes. The results revealed that H3/Ser10 phosphorylation of A chromosomes occurred only in the pericentromeric region in both mitosis and meiosis, whereas in the B univalent, phosphorylation appeared in almost the whole extent of the chromosome, except in the terminal portion of the long arm. In meiosis II, the phosphorylation of A chromosomes was similar to that in the first division of meiosis, but the Bs did not show H3/Ser10 phosphorylation. Our results suggest that phosphorylation at the pericentromeric region may be associated with chromosome motility during cell divisions and with the cohesion of B chromatids in a univalent structure in meiosis I.

Sign in / Sign up

Export Citation Format

Share Document