Nodules associated with axial cores and synaptonemal complexes during zygotene in Psilotum nudum

Chromosoma ◽  
1988 ◽  
Vol 97 (1) ◽  
pp. 96-100 ◽  
Author(s):  
Lorinda K. Anderson ◽  
Stephen M. Stack
Keyword(s):  
Synaptonemal Complexes ◽  
Psilotum Nudum

The Occurrence of Polycomplexes During the Sporogenesis in Psilotum Nudum

1980 ◽  
Vol 38 ◽  
pp. 532-533
Author(s):  
Kit W. Lee
Keyword(s):  
Developmental Stages ◽  
Higher Plants ◽  
Vascular Plant ◽  
Uranyl Acetate ◽  
Late Zygotene ◽  
Synaptonemal Complexes ◽  
Chromosome Synapsis ◽  
Psilotum Nudum ◽  
Consistent Feature ◽  
Ethanol Series

The structure of the polycomplexes has been extensively studied in recent years (1,2,3). Theres structures are usually described as stacks or aggregates of the tripartite synaptonemal complexes. Although the presence of the synaptonemal complexes is a consistent feature in the late zygotene or pachytene stages of chlasmate meiosis and Its role in the processes of chromosome synapsis and crossing over has been suggested (4), the function of the polycomplexes remains obscure. Most of our understandings of the polycomplexes are obtained from the observations during the gametogenesis of the insects, and only a few examples of this structure in fungi and higher plants have been reported. The present study examines the occurrence of polycomplexes during the sporogenesis in the primitive vascular plant. Sporangia at different developmental stages were fixed with 3% glutaraldehyde in 0.1 M phosphate buffer, and postflxed in 2% osmium tetroxide. Dehydration was carried out with the ethanol series followed by embedding in Epon 812. Ultrathln sections were stained with uranyl acetate and lead citrate.

A Scanning Electron Microscope Study of Isolated Guard Cells

1973 ◽  
Vol 31 ◽  
pp. 454-455 ◽  
Author(s):  
P. Dayanandan ◽  
P. B. Kaufman
Keyword(s):  
Electron Microscope ◽  
Electron Microscope Study ◽  
Three Dimensional ◽  
Guard Cells ◽  
Scanning Electron Microscope Study ◽  
Psilotum Nudum ◽  
Subsidiary Cells ◽  
Welwitschia Mirabilis ◽  
Cycas Revoluta ◽  
Scanning Electron

A three dimensional appreciation of the guard cell morphology coupled with ultrastjuctural studies should lead to a better understanding of their still obscure dynamics of movement. We have found the SEM of great value not only in studies of the surface details of stomata but also in resolving the structures and relationships that exist between the guard and subsidiary cells. We now report the isolation and SEM studies of guard cells from nine genera of plants.Guard cells were isolated from the following plants: Psilotum nudum, four species of Equisetum, Cycas revoluta, Ceratozamia sp., Pinus sylvestris, Ephedra cochuma, Welwitschia mirabilis, Euphorbia tirucalli and Allium cepa.

An Ultrastructural and Radioautographic Study of Early Oogenesis in the Toad Xenopus Laevis

1973 ◽  
Vol 12 (1) ◽  
pp. 71-93
Author(s):  
LESLEY WATSON COGGINS
Keyword(s):  
Electron Microscope ◽  
Xenopus Laevis ◽  
Thymidine Incorporation ◽  
Ultrastructural Level ◽  
Extrachromosomal Dna ◽  
Late Pachytene ◽  
Synaptonemal Complexes ◽  
Round Nucleus ◽  
A Cell ◽  
Major Period

Early oogenesis in the toad Xenopus laevis has been investigated at the ultrastructural level, with particular reference to the formation of extrachromosomal DNA. Thymidine incorporation was localized by electron microscope radioautography. In oogonia, the nucleus is irregular in outline and may contain several nucleoli. Oocytes, from premeiotic interphase to late pachytene, are found in cell nests which are estimated to consist of about 16 cells each. Adjacent oocytes within a nest are connected by intercellular bridges and develop synchronously. Each premeiotic interphase-leptotene oocyte has a round nucleus which contains one or two centrally located, spherical nucleoli. Electron-microscope radioautography showed that all nuclei in a cell nest incorporate thymidine synchronously during premeiotic S-phase. In zygotene oocytes, axial cores and synaptonemal complexes are observed in the nucleus and abut against the inner nuclear membrane in the region nearest the centre of the cell nest. The nucleolus is still more-or-less round in outline, but is asymmetrically positioned in the nucleus. It lies near the nuclear envelope on the side of the nucleus furthest away from the attachment of the chromosome ends, that is, nearest the outside of the cell nest. Each nucleolus is surrounded by a fibrillar ‘halo’ of nucleolus-associated chromatin into which a low level of thymidine incorporation occurs during zygotene. This is thought to represent the start of the major period of amplification of the ribosomal DNA. Pachytene is characterized by the presence of synaptonemal complexes in the nucleus. The nucleolus becomes very irregular in outline. The fibrillar area around it, which represents the extrachromosomal DNA, increases in size and thymidine is incorporated over the whole of this region. In late pachytene, many small fibrogranular bodies, the multiple nucleoli, are formed in it. The members of a cell nest become separated from one another at this time and begin to develop asynchronously. In diplotene, synaptonemal complexes are no longer observed in the nucleus. The most prominent structures in the nucleus are now the multiple nucleoli, which increase greatly in number in early diplotene. A large increase in cytoplasmic volume occurs and the oocyte grows in size.

Ultrastructural karyology of Spongospora subterranea (Plasmodiophoromycetes)

1992 ◽  
Vol 70 (6) ◽  
pp. 1228-1233 ◽  
Author(s):  
James P. Braselton
Keyword(s):  
Electron Microscopy ◽  
Single Unit ◽  
Spongospora Subterranea ◽  
Unit Membrane ◽  
Potato Tubers ◽  
Haploid Chromosome Number ◽  
Synaptonemal Complexes ◽  
Transmission Electron ◽  
Host Parasite ◽  
Section Analysis

Sporogenic (cystogenous) stages of development of Spongospora subterranea (Wallroth) Lagerheim f.sp. subterranea Tomlinson infecting potato tubers were examined with transmission electron microscopy. Volume of nuclei in transitional Plasmodia was 28.2 ± 8.3 μm3. Serial section analysis revealed 37 synaptonemal complexes, hence the haploid chromosome number was considered to be 37. Total length of synaptonemal complexes per nucleus was 74.6 ± 1.4 μm, with individual synaptonemal complexes ranging in length from 1.34 ± 0.07 μm to 3.48 ± 0.17 μm. No polycomplexes were observed in transitional nuclei. Electron-opaque thickenings of lateral elements occurred irregularly. Additional ultrastructural features of sporogenic plasmodia included end-to-end paired centrioles defining the poles of the nuclei and a host–parasite boundary of a single unit membrane. Key words: karyotype, Plasmodiophoromycetes, Spongospora, synaptonemal complex.

scholarly journals Stomatal Development in Aerial Axes of Psilotum nudum (Psilotaceae)

2012 ◽  
Vol 128 (3-4) ◽  
pp. 95-99 ◽  
Author(s):  
James E. Mickle ◽  
Maria Rosaria Barone Lumaga ◽  
Paolo De Luca
Keyword(s):  
Electron Microscopy ◽  
Guard Cells ◽  
Cytoplasmic Protein ◽  
Stomatal Development ◽  
Wax Deposition ◽  
Psilotum Nudum ◽  
Pd Alloy ◽  
Entire Cell ◽  
Mother Cells ◽  
Scanning Electron

Abstract Apical regions of developing aerial shoots of Psilotum nudum (L.) Beauv. were studied using both scanning electron microscopy (SEM) and light microscopy (LM) with the aim of improving our understanding of early stages in stomatal and epidermal ontogenesis. SEM samples were fixed in gluteraldehyde, critical point dried, and coated with an Au-Pd alloy. LM samples were fixed in FAA and embedded in paraffin. LM sections were stained with 0.05% toluidine blue for protein. SEM shows that P. nudum stomata develop from 20 µm-long domed meristemoid cells into guard cell mother cells (GMCs). A furrow dividing guard cells develops at 30 µm long, and wax deposition that will cover the entire cell begins at 70 µm long. LM longitudinal sections of GMCs show a cytoplasmic protein net that organizes into radial fibers, similar to reports of actin fibers in stomata of angiosperms. This study provides additional details of stomatal development in Psilotum and is the first report of an actin-like protein net in Psilotum.

The synaptonemal complexes of Achlya recurva (Oomycetes): karyotype analysis and three-dimensional reconstruction of pachytene nuclei in antheridia and oogonia

1991 ◽  
Vol 69 (6) ◽  
pp. 1384-1395 ◽  
Author(s):  
Hobart R. Williamson ◽  
Pesach Ben Yitzchak
Keyword(s):  
Synaptonemal Complex ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolus Organizer Region ◽  
Three Dimensional ◽  
Central Element ◽  
Three Dimensional Reconstruction ◽  
Synaptonemal Complexes ◽  
Sequence Of Events ◽  
Dimensional Reconstruction

Fifteen synaptonemal complexes, as determined by three-dimensional reconstruction of serial, ultrathin sections, were present within both antheridial and oogonial zygotene and pachytene nuclei of the oomyceteous fungus Achlya recurva, thus n = 15. The present study represents the first complete reconstruction of synaptonemal complexes in the genus Achlya. The occurrence of both zygonema and pachynema was simultaneous in antheridia and oogonia. Pachytene nuclei of antheridia and oogonia are small, 13 μm3 in volume, and the average length of the synaptonemal complexes ranged from 1.9 to 4.4 μm. Lateral elements at zygotene ranged from 1.2 to 4.7 μm. Both ends of each synaptonemal complex were attached randomly to the nuclear envelope, so a bouquet formation was not observed at pachytene. In A. recurva, the dimensions of the synaptonemal complex were as follows: overall width = 270 nm; the lateral elements = 75 nm each in width and the central region = 120 nm. There was no central element and associated transverse filaments, which may be associated with development of alternative reproductive strategies other than amphimixis, as in nematodes. Of the 15 synaptonemal complexes present, only the one carrying the nucleolus organizer region could be clearly identified from one nucleus to the next. The nucleolar organizer region was on the average 0.75 μm from the telomere in both zygotene and pachytene nuclei. There were an average of three recombination nodules in each nucleus. Synaptonemal complexes have been reported in over 80 different species of fungi and related protista. Karyotypic evolution in the oomycetes and fungi may be the result of poly-ploidization, followed by cytogenetic diversification involving aneuploidy and differing degrees of polyploidy. Such a sequence of events could explain the apparent polyphyletic formation of this group. Key words: karyotype, Oomycetes, pachytene, synaptonemal complexes, three-dimensional reconstruction.

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