Ultrastructure of the Fungal Nucleus

1971 ◽  
Vol 9 (2) ◽  
pp. 453-473
Author(s):  
M. GIRBARDT
Keyword(s):  
Nuclear Envelope ◽  
Direct Contact ◽  
Nuclear Division ◽  
Higher Plants ◽  
Compound Structure ◽  
Interphase Nuclei ◽  
Electron Dense Material ◽  
Nuclear Age ◽  
Division Process ◽  
Polar Organelle

The electron-dense material which regularly occurs at the poles of the nuclei of certain fungi during division has been studied in hyphal interphase nuclei of 4 basidio- and 3 ascomycetes. The shape of this material varies with the species and the nuclear age and may be that of a sphere or a dumbbell. In some instances paired diskoidal structures are found in the place of the globular elements of the dumbbell configuration. The organelle in question lies in an invagination of the nuclear envelope preferentially at the forward pointing pole of the nucleus. Its size (0.1-0.5 µm) is correlated with the size of the nucleus. In Polystictus versicolor the diameter of both globular elements of the polar organelle increases during initiation of the division process. The structure is identical with the fungal ‘centriole’ of light-microscopical studies but lacks the characteristic organization of a true centriole. It is suggested that the polar organelle is the equivalent of a kinetochore because it maintains continuous and direct contact with the nuclear envelope (on its cytoplasmic aspect), seems to be connected with the karyoplasm, exhibits oscillating movements, is continuous with microtubules during division and resembles in its fine structure the kinetochores of the chromosomes of higher plants and animals. In addition to its function as an organelle of nuclear motility it also seems to play a part in the initiation of DNA synthesis and nuclear division. If this is correct one would expect to find the genome of the fungal nucleus having the form of a unitary, coherent compound structure (chain) extending from or incorporating a single, solitary kinetochore.

Nuclear division in the marine dinoflagellate Oxyrrhis marina

1986 ◽  
Vol 85 (1) ◽  
pp. 161-175
Author(s):  
X.P. Gao ◽  
J.Y. Li
Keyword(s):  
Nuclear Envelope ◽  
Phylogenetic Relationships ◽  
Nuclear Division ◽  
Metaphase Plate ◽  
Active Role ◽  
Ultrastructural Changes ◽  
Interphase Nuclei ◽  
Oxyrrhis Marina ◽  
Two Stages ◽  
Anaphase B

The nuclear division of Oxyrrhis marina is a very distinct one among the mitoses of dinoflagellates that have been studies. Using synchronized populations, we have investigated the ultrastructural changes in this nuclear division. In interphase, nuclei can be classified into two groups on the basis of the shapes of the chromosomes. Y- and U-shaped chromosomes have been observed in both types of interphase nuclei. By prophase the nucleus becomes oval, many nuclear plaques appear on the nuclear envelope, and many microtubules radiate from these nuclear plaques within the nucleus. Metaphase can be identified by the characteristic arrangement of the chromosomes; an equatorial metaphase plate is absent. As in many higher organisms, anaphase includes two stages: anaphase A and anaphase B. During anaphase A the nucleus does not apparently elongate and the chromosomes migrate towards the poles by a combination of the shortening of the chromosome-associated microtubules and the elongation of those located between daughter chromosomes. During anaphase B the nucleus elongates to about twice its former length. This elongation may result from growth of the interzonal nuclear envelope. Dividing nucleoli are associated with microtubules, which suggests that microtubules may play an active role in the division of the nucleolus. The evolution of mitosis and the phylogenetic relationships between Oxyrrhis, typical dinoflagellates and Syndinium are discussed.

Ultrastructure of Mitosis in the Aquatic Phycomycete Chytriomyces Hyalinus

1980 ◽  
Vol 38 ◽  
pp. 498-499
Author(s):  
David G. Pechak
Keyword(s):  
Life Cycle ◽  
Nuclear Envelope ◽  
Nuclear Division ◽  
Condensed Chromatin ◽  
Nuclear Pores ◽  
Interphase Nuclei ◽  
Aquatic Phycomycete ◽  
Simple Life

The aquatic Phycomycetes, particularly the Chytridiales, are a group of fungi with a rather simple life cycle and morphology. With the advent of ultrastructural investigations on these organisms, two stable characteristics (zoospore ultrastructure and nuclear division) have proven helpful in elucidating relationships in this perplexing taxon. The latter is described in this communication. Conventional techniques were employed in the preparation of the material. Interphase nuclei of C. hyalinus are essentially spherical in shape, measure approximately 2.8 μm in diameter, and have a single, centrally located, nucleus. Prophase nuclei, while not exhibiting condensed chromatin, are characterized by the presence of migrating centrioles and a fusiform or spindle-shape to the nuclear profile (Fig. 1). Nuclear pores predominate near the polar ends of the nuclear envelope. No evidence has been found to indicate that centrioles replicate during prophase.

Spindle Microtubules in the Dividing Nuclei of Trypanosomes

1970 ◽  
Vol 6 (2) ◽  
pp. 365-383 ◽  
Author(s):  
K. VICKERMAN ◽  
T. M. PRESTON
Keyword(s):  
Electron Microscope ◽  
Nuclear Envelope ◽  
Nuclear Division ◽  
Sleeping Sickness ◽  
Condensed Chromatin ◽  
Division Process ◽  
Spindle Microtubules

Stages in nuclear division have been identified in sections of bloodstream and cultured trypanosomes examined with the electron microscope. In the sleeping sickness trypanosome Trypanosoina rhodesiense at division the nuclear envelope and nucleolus-like endosome persist and become stretched along an axis. An acentric spindle of microtubules encases the elongating endosome As division proceeds the endosomal material fragments In bloodstream forms condensed chromatin (chromosomal material) appears to be associated with the nuclear envelope during the phase of nuclear elongation but to fall away from the envelope late in the phase of nuclear constriction. In culture forms the chromatin is not so abundant The discrete chromosomes envisaged by some light microscopists in stained preparations have not been identified using the electron microscope. The spindle may contain only continuous microtubules. It is suggested that the spindle serves to push the two halves of the nucleus apart, and that the nuclear envelope of each half may act as a vehicle in separation of the daughter genomes. In culture forms of the elasmobranch parasite T. raiae, the endosome appears to disintegrate as the spindle is formed, and from then onwards it becomes difficult to distinguish endosomal material from what might be chromatin. There is no noticeable association between chromatin-like material and the nuclear envelope. Some of the spindle tubules converge on kinetochore-like plaques and the presence of chromosomal microtubules cannot be ruled out. These preliminary studies indicate that the nuclear division process of trypanosomes is not closely akin to eukaryote mitosis, though it may bear some resemblance to nuclear division in Euglena. Within the genus Trypanosoma, moreover, the nuclear division process may vary from species to species and, possibly, even from one strain to another within a species.

Fine structure of the haplosporidan Kernstab, a persistent, intranuclear mitotic apparatus

1975 ◽  
Vol 18 (2) ◽  
pp. 327-346
Author(s):  
F.O. Perkins
Keyword(s):  
Fine Structure ◽  
Nuclear Envelope ◽  
Light Microscope ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Interphase Nuclei ◽  
Mitotic Apparatus ◽  
Pole Body

The fine structure of the haplosporidan mitotic apparatus is described from observations of plasmodial nuclei of Minchinia nelsoni, M. costalis, Minchinia sp., and Urosporidium crescens. The apparatus, which is the Kernstab of light-microscope studies, consists of a bundle of microtubules terminating in a spindle pole body (SPB) at each end of the bundle. A few microtubules extend from SPB to SPB, but most either extend from an SPB and terminate in the nucleoplasm or lie in the nucleoplasm, free of either SPB. The bundle lengthens during mitosis, increasing the SPB-to-SPB distance by a factor of 2 to 3 as compared to interphase nuclei. SPBs are not in contact with the nuclear envelope, being found always in the nucleoplasm which is delimited by the nuclear envelope throughout mitosis. The mitotic apparatus is persistent through interphase, at least in a form which is not significantly different from that found in mitotic nuclei.

Maize meiotic spindles assemble around chromatin and do not require paired chromosomes

1998 ◽  
Vol 111 (23) ◽  
pp. 3507-3515 ◽  
Author(s):  
A. Chan ◽  
W.Z. Cande
Keyword(s):  
Nuclear Envelope ◽  
Higher Plants ◽  
Metaphase Plate ◽  
Meiotic Spindle ◽  
Wild Type ◽  
Homologous Chromosomes ◽  
Nuclear Envelope Breakdown ◽  
Meiotic Spindles ◽  
Meiotic Mutations ◽  
Bipolar Spindles

To understand how the meiotic spindle is formed and maintained in higher plants, we studied the organization of microtubule arrays in wild-type maize meiocytes and three maize meiotic mutants, desynaptic1 (dsy1), desynaptic2 (dsy2), and absence of first division (afd). All three meiotic mutations have abnormal chromosome pairing and produce univalents by diakinesis. Using these three mutants, we investigated how the absence of paired homologous chromosomes affects the assembly and maintenance of the meiotic spindle. Before nuclear envelope breakdown, in wild-type meiocytes, there were no bipolar microtubule arrays. Instead, these structures formed after nuclear envelope breakdown and were associated with the chromosomes. The presence of univalent chromosomes in dsy1, dsy2, and afd meiocytes and of unpaired sister chromatids in the afd meiocytes did not affect the formation of bipolar spindles. However, alignment of chromosomes on the metaphase plate and subsequent anaphase chromosome segregation were perturbed. We propose a model for spindle formation in maize meiocytes in which microtubules initially appear around the chromosomes during prometaphase and then the microtubules self-organize. However, this process does not require paired kinetochores to establish spindle bipolarity.

The analysis of 40 kDa nuclear protein, p40, in interphase cells and mitotic cells

1993 ◽  
Vol 106 (3) ◽  
pp. 741-748 ◽  
Author(s):  
Y. Kaneda ◽  
K. Kinoshita ◽  
M. Sato ◽  
K. Tanaka ◽  
Y. Kaneda
Keyword(s):  
Monoclonal Antibody ◽  
Nuclear Envelope ◽  
Nuclear Protein ◽  
Dnase I ◽  
High Salt ◽  
The Other ◽  
Interphase Nuclei ◽  
Interphase Cells ◽  
Detergent Treatment ◽  
Sequential Treatments

We previously reported that the monoclonal antibody M108 recognized a 40 kDa protein both in the nucleus and the cytoplasm. This nuclear 40 kDa antigen was located in the nuclear envelope in interphase cells and in the perichromosomal region during mitosis. Now, we have analyzed this nuclear 40 kDa protein (p40) further, through morphological and biochemical approaches. At the beginning of mitosis, the perinuclear p40 detached from the nuclear envelope and moved to surround the condensing chromatin, while in the late stage of mitosis, the perichromosomal p40 moved back to the reassembled nuclear envelope. Most of the perichromosomal p40 on the metaphase chromosome was solubilized only by DNase I treatment, not by either high salt or detergent treatment. On the other hand, the perinuclear p40 was not solubilized by DNase1 alone, or high salt detergent alone. Sequential treatments with DNase I and high salt detergent were required to extract p40 in interphase nuclei. These results suggest that p40 was associated both with the nuclear envelope and chromatin DNA in interphase nuclei, while it bound only to chromatin DNA in mitosis.

Three-dimensional reconstruction of the chromatin bodies in the nuclei of mature erythrocytes from the newt Triturus cristatus: the number of nuclear envelope-attachment sites

1979 ◽  
Vol 35 (1) ◽  
pp. 59-66
Author(s):  
A.B. Murray ◽  
H.G. Davies
Keyword(s):  
Nuclear Envelope ◽  
Three Dimensional ◽  
Interphase Nuclei ◽  
Interphase Chromosome ◽  
Triturus Cristatus ◽  
3 Dimensional ◽  
Attachment Sites ◽  
Chromatin Body ◽  
Dimensional Reconstruction ◽  
Discrete Site

The arrangement of the chromatin bodies in the interphase nuclei of 6 erythrocytes has been investigated by means of 3-dimensional reconstruction from electron micrographs of serial sections. When the borders of chromatin bodies are marked on the surface of each model, discrete areas of chromatin in contact with the nuclear envelope are revealed. The number of these areas in approximately equal to the number of chromosomes in the diploid set. The data suggest that each chromatin body corresponds to a condensed interphase chromosome and that each chromosome is attached to one discrete site on the nuclear envelope. The data are insufficient to show whether or not the condensed chromosomes are arranged in any orderly pattern in these nuclei.

scholarly journals A carboxyl-terminal interaction of lamin B1 is dependent on the CAAX endoprotease Rce1 and carboxymethylation

2003 ◽  
Vol 162 (7) ◽  
pp. 1223-1232 ◽  
Author(s):  
Christopher P. Maske ◽  
Michael S. Hollinshead ◽  
Niall C. Higbee ◽  
Martin O. Bergo ◽  
Stephen G. Young ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Lamina ◽  
Potential Mechanism ◽  
Interphase Nuclei ◽  
Lamin B1 ◽  
Carboxyl Terminal ◽  
Caax Motif

The mammalian nuclear lamina protein lamin B1 is posttranslationally modified by farnesylation, endoproteolysis, and carboxymethylation at a carboxyl-terminal CAAX motif. In this work, we demonstrate that the CAAX endoprotease Rce1 is required for lamin B1 endoproteolysis, demonstrate an independent pool of proteolyzed but nonmethylated lamin B1, as well as fully processed lamin B1, in interphase nuclei, and show a role for methylation in the organization of lamin B1 into domains of the nuclear lamina. Deficiency in the endoproteolysis or methylation of lamin B1 results in loss of integrity and deformity of the nuclear lamina. These data show that the organization of the nuclear envelope and lamina is dependent on a mechanism involving the methylation of lamin B1, and they identify a potential mechanism of laminopathy involving a B-type lamin.

Ultrastructure of somatic mitosis in a diploid strain of the plant pathogenic fungus Cochliobolus sativus

1975 ◽  
Vol 53 (4) ◽  
pp. 403-414 ◽  
Author(s):  
H. C. Huang ◽  
R. D. Tinline ◽  
L. C. Fowke
Keyword(s):  
Nuclear Envelope ◽  
Ultrastructural Study ◽  
Pathogenic Fungus ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Cochliobolus Sativus ◽  
Diploid Strain ◽  
Interphase Nuclei ◽  
Pole Body ◽  
Spindle Microtubules

An ultrastructural study of mitosis in a diploid strain of Cochliobolus sativus showed the event to be intranuclear. Two nucleoli occasionally were present in interphase nuclei. During division the spindle pole body peripheral to the nuclear envelope divided; spindle microtubules radiated into the nucleoplasm from the amorphous granular region abutting the nuclear envelope beneath the bodies; chromosomes condensed at prophase, approached the equatorial plane at metaphase, and moved asynchronously at anaphase; single microtubules appeared attached to kinetochore-like structures. At telophase, nuclei exhibited maximal elongation; fissures of the nuclear envelope appeared in the interzonal region; the nucleolus dispersed. The polar nuclear areas became new daughter nuclei with nucleoli.

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