Meiotic chromosome structure. Kinetochores and chromatid cores in standard and B chromosomes of Arcyptera fusca (Orthoptera) revealed by silver staining

Genome ◽  
1991 ◽  
Vol 34 (1) ◽  
pp. 19-27 ◽  
Author(s):  
J. A. Suja ◽  
J. de la Torre ◽  
J. F. Giménez-Abián ◽  
C. García de la Vega ◽  
J. S. Rufas
Keyword(s):  
Meiotic Division ◽  
Silver Staining ◽  
Chromosome Structure ◽  
Sex Chromosome ◽  
Meiotic Chromosome ◽  
B Chromosomes ◽  
Chromosome Organization ◽  
Autosomal Bivalents ◽  
Metaphase I

The behaviour of two chromosome structures in silver-stained chromosomes was analyzed through the first meiotic division in spermatocytes of the acridoid species Arcyptera fusca. Results showed that at diakinesis kinetochores and chromatid cores are individualized while they associate in bivalents of metaphase I; only kinetochores and distal core spots associate in the sex chromosome. Metaphase I is characterized by morphological and localization changes of both kinetochores and cores which define the onset of anaphase I. These changes analyzed in both autosomes and in the sex chromosome allow us to distinguish among three different substages in metaphase I spermatocytes. B chromosomes may be present as univalents, bivalents, or trivalents. Metaphase I B univalents are characterized by separated cores except at their distal ends and individualized and flat sister kinetochores. At anaphase I sister kinetochores of lagging B chromatids remain connected through a silver-stained strand. The behaviour of cores and kinetochores of B bivalents is identical with that found in the autosomal bivalents. The differences in the morphology of kinetochores of every chromosome shown by B trivalents at metaphase I may be related to the balanced forces acting on the multivalent. The results show dramatic changes in chromosome organization of bivalents during metaphase I. These changes suggest that chromatid cores are not involved in the maintenance of bivalents. Moreover, the changes in morphology of kinetochores are independent of the stage of meiosis but correlate with the kind of division (amphitelic–syntelic) that chromosomes undergo.Key words: kinetochore, chromatid core, B chromosomes, meiosis, chromosome structure, silver staining.

Evolution of the Sex Chromosomes in Beetles. I. The Loss of the Y Chromosome

2017 ◽  
Vol 152 (2) ◽  
pp. 97-104 ◽  
Author(s):  
Anne-Marie Dutrillaux ◽  
Bernard Dutrillaux
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Silver Staining ◽  
Sex Chromosome ◽  
B Chromosomes ◽  
Chromosome Constitution ◽  
Chromosome Loss ◽  
Autosomal Bivalents ◽  
C Banding ◽  
Nucleolar Proteins

In the males of Coleoptera, the most frequent sex chromosome constitution is XY. At metaphase I of meiosis, the X and Y are linked by nucleolar proteins, forming the so-called parachute bivalent (Xyp), which is assumed to allow the non-synapsed X and Y to segregate correctly at anaphase I. However, X0 males are not exceptional, and we explored the relationships between the X and nucleolar proteins in the absence of the Y chromosome in 6 species belonging to different families/subfamilies. Using C-banding and silver staining, we show that nucleolar proteins always remain in contact with the X until anaphase I. These proteins are generally more abundant than in the Xyp bivalent, may remain associated with the NOR during diakinesis, and frequently link the X to 1 or 2 autosomal bivalents, which seem to play the same role as the Y. This role may also be played by B chromosomes, which appear to be more frequent in X0 than in XY males. In conclusion, following Y chromosome loss, various strategies using nucleolar proteins have been developed to facilitate the migration of the unique X at meiotic anaphase I.

Meiotic chromosome structure: relationship between the synaptonemal complex and the chromatid cores

Genome ◽  
1992 ◽  
Vol 35 (6) ◽  
pp. 1054-1061 ◽  
Author(s):  
J. S. Rufas ◽  
J. L. Santos ◽  
M. Diez ◽  
J. A. Suja
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Synaptonemal Complex ◽  
Chromosome Structure ◽  
Sex Chromosome ◽  
Meiotic Chromosome ◽  
Light And Electron Microscopy ◽  
Structure Relationship ◽  
Surface Spread ◽  
Relationship Of

The development of silver-stained synaptonemal complexes (SCs) and of chromatid cores was analyzed in squashed and surface-spread grasshopper spermatocytes using light and electron microscopy, respectively. This study was conducted to determine the relationship of the two chromosome structures and then obtain more insight into the meiotic chromosome structure. Pachytene cells observed by light microscopy showed thin silver-stained threads, representing SCs, along the centre of the bivalents. However, fully formed SCs, and an axial element corresponding to the univalent sex chromosome, appeared when these cells were observed by electron microscopy. During early diplotene no silver-stained threads were observed by light microscopy. However, fragmentation of the SCs was apparent in cells at the same stage when observed by electron microscopy. Both light and electron microscopy showed that chromosome cores were first detected in homologues of late diplotene – early diakinesis cells. During diakinesis the cores were not continuous but were interrupted where interstitial chiasmata occur. In prometaphase I – metaphase I cells these cores appeared continuous and double, i.e., each chromatid clearly showed its own core. We propose a model whereby the associated cores of sister chromatids act as frameworks for the formation of the SC lateral elements.Key words: meiosis, chromosome structure, synaptonemal complex, chromatid core.

Chromosome organization in meiosis revealed by light microscope analysis of silver-stained cores

Genome ◽  
1987 ◽  
Vol 29 (5) ◽  
pp. 706-712 ◽  
Author(s):  
J. S. Rufas ◽  
J. Gimenez-Abian ◽  
J. A. Suja ◽  
C. Garcia De La Vega
Keyword(s):  
Key Words ◽  
Light Microscope ◽  
Meiotic Chromosome ◽  
Chiasma Formation ◽  
Silver Impregnation ◽  
Meiotic Metaphase ◽  
Chromosome Organization ◽  
Microscope Analysis ◽  
Impregnation Technique ◽  
Metaphase I

Three species of grasshoppers have been analyzed by means of a modified silver impregnation technique that reveals the presence of a chromatid core that identifies chiasmata at first meiotic metaphase. In terms of the behaviour of the chromatid core most of the configurations observed at diplotene with orcein are easily recognized in metaphase I silver-stained bivalents. Some "hidden" configurations, as well as simple chromatin associations, that do not appear to represent chiasmata have also been detected. The disposition and behaviour of the chromatid cores in metaphase I and anaphase I provide grounds to support a reorganization of half-bivalents between first and second division. Key words: chromatid core, meiotic chromosome organization, chiasma formation, insect cytogenetics.

Pycnotic cycle of the sex chromosome of Pyrgomorpha conica (Orthoptera) and development of spermiogenesis

Genome ◽  
1993 ◽  
Vol 36 (3) ◽  
pp. 535-541 ◽  
Author(s):  
Carmen Antonio ◽  
Jose M. Gonzalez-Garcia ◽  
Jose A. Suja
Keyword(s):  
Meiotic Division ◽  
Centromeric Region ◽  
Sex Chromosome ◽  
Intercellular Bridges ◽  
Metaphase I

We have analyzed the anomalous pycnotic cycle of the X sex chromosome of the grasshopper Pyrgomorpha conica throughout both meiotic divisions and its possible influence on spermiogenesis. During diplotene the sex chromosome shows two differentiated pycnotic regions: (i) the centromeric region, which is negatively heteropycnotic, and (ii) the noncentromeric region, which shows alternating negatively and positively heteropycnotic zones in all standard individuals. The variation in size and location of the negative heteropycnotic zones, their smooth appearance, and their lack of effect on spermiogenesis lead us to suggest that condensation differences and not euchromatinization are responsible for their presence. In two individuals the sex chromosome appeared partially isopycnotic at metaphase I, and high levels of abnormal spermatids (macrospermatids and microspermatids) were found. We suggest that the possible activity of this chromosome during the second meiotic division may promote the disruption of spermiogenesis by affecting the mechanism that maintains intercellular bridges between normal spermatids.Key words: sex chromosome, heterochromatin, heteropycnosis, meiosis, spermiogenesis.

Nucleolar organizer regions are associated with silver-stained chromatid cores in meiotic chromosomes of grasshoppers

Genome ◽  
1989 ◽  
Vol 32 (5) ◽  
pp. 829-833 ◽  
Author(s):  
J. F. Giménez-Abián ◽  
G. Giménez-Martín ◽  
J. A. Suja ◽  
J. S. Rufas
Keyword(s):  
Silver Staining ◽  
Chromosome Structure ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Nucleolar Organizer Regions ◽  
Chromosome Marker ◽  
Meiotic Chromosomes ◽  
Close Interrelationship ◽  
Metaphase I

Silver staining was employed to study the expression and localization of nucleolar organizer regions (NORs) and the localization and development of chromatid cores during the meiotic divisions of the grasshopper Chorthippus jucundus. NORs appear as silver-stained dots on the short arms of the L2 and L3 chromosomes and are always associated with chromatid cores. This observation provides an excellent chromosome marker to analyze the behaviour of chromatid cores during meiosis. Since both structures (NORs and chromatid cores) show a close interrelationship, we have obtained further evidence on the changes of organization that meiotic chromosomes undergo between metaphase I and anaphase I.Key words: nucleolar organizer region, meiosis, chromatid cores, chromosome structure, silver staining.

Synaptonemal complex proteins: occurrence, epitope mapping and chromosome disjunction

1994 ◽  
Vol 107 (10) ◽  
pp. 2749-2760 ◽  
Author(s):  
M.J. Dobson ◽  
R.E. Pearlman ◽  
A. Karaiskakis ◽  
B. Spyropoulos ◽  
P.B. Moens
Keyword(s):  
Synaptonemal Complex ◽  
Fusion Proteins ◽  
Epitope Mapping ◽  
Core Protein ◽  
Binding Capacity ◽  
Polyclonal Antibodies ◽  
Meiotic Chromosome ◽  
Immunogold Labelling ◽  
Chromosome Disjunction ◽  
Metaphase I

We have used polyclonal antibodies against fusion proteins produced from cDNA fragments of a meiotic chromosome core protein, Cor1, and a protein present only in the synapsed portions of the cores, Syn1, to detect the occurrence and the locations of these proteins in rodent meiotic prophase chromosomes. The 234 amino acid Cor1 protein is present in early unpaired cores, in the lateral domains of the synaptonemal complex and in the chromosome cores when they separate at diplotene. A novel observation showed the presence of Cor1 axial to the metaphase I chromosomes and substantial amounts of Cor1 in association with pairs of sister centromeres. The centromere-associated Cor1 protein becomes dissociated from the centromeres at anaphase II and it is not found in mitotic metaphase centromeres. The extended presence of Cor1 suggests that it may have a role in chromosome disjunction by fastening chiasmata at metaphase I and by joining sister kinetochores, which ensures co-segregation at anaphase I. Two-colour immunofluorescence of Cor1 and Syn1 demonstrates that synapsis between homologous cores is initiated at few sites but advances rapidly relative to the establishment of new initiation sites. If the rapid advance of synapsis deters additional initiation sites between pairs of homologues, it may provide a mechanism for positive recombination interference. Immunogold epitope mapping of antibodies to four Syn1 fusion proteins places the amino terminus of Syn1 towards the centre of the synaptonemal complex while the carboxyl terminus extends well into the lateral domain of the synaptonemal complex. The Syn1 fusion proteins have a non-specific DNA binding capacity. Immunogold labelling of Cor1 antigens indicates that the lateral domain of the synaptonemal complex is about twice as wide as the apparent width of lateral elements when stained with electron-dense metal ions. Electron microscopy of shadow-cast surface-spread SCs confirms the greater width of the lateral domain. The implication of these dimensions is that the proteins that comprise the synaptic domain overlap with the protein constituents of the lateral domains of the synaptonemal complex more than was apparent from earlier observations. This arrangement suggests that direct interactions might be expected between some of the synaptonemal complex proteins.

scholarly journals A conserved filamentous assembly underlies the structure of the meiotic chromosome axis

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Alan MV West ◽  
Scott C Rosenberg ◽  
Sarah N Ur ◽  
Madison K Lehmer ◽  
Qiaozhen Ye ◽  
...  
Keyword(s):  
Meiotic Recombination ◽  
Budding Yeast ◽  
Meiotic Chromosome ◽  
Coiled Coil ◽  
Chromosome Organization ◽  
Molecular Architecture ◽  
Master Regulators ◽  
Core Proteins ◽  
Protein Components ◽  
Chromosome Axis

The meiotic chromosome axis plays key roles in meiotic chromosome organization and recombination, yet the underlying protein components of this structure are highly diverged. Here, we show that ‘axis core proteins’ from budding yeast (Red1), mammals (SYCP2/SYCP3), and plants (ASY3/ASY4) are evolutionarily related and play equivalent roles in chromosome axis assembly. We first identify ‘closure motifs’ in each complex that recruit meiotic HORMADs, the master regulators of meiotic recombination. We next find that axis core proteins form homotetrameric (Red1) or heterotetrameric (SYCP2:SYCP3 and ASY3:ASY4) coiled-coil assemblies that further oligomerize into micron-length filaments. Thus, the meiotic chromosome axis core in fungi, mammals, and plants shares a common molecular architecture, and likely also plays conserved roles in meiotic chromosome axis assembly and recombination control.

scholarly journals Varietal variation and chromosome behaviour during meiosis in Solanum tuberosum

Heredity ◽  
2020 ◽  
Vol 125 (4) ◽  
pp. 212-226 ◽  
Author(s):  
Anushree Choudhary ◽  
Liam Wright ◽  
Olga Ponce ◽  
Jing Chen ◽  
Ankush Prashar ◽  
...  
Keyword(s):  
Solanum Tuberosum ◽  
Meiotic Chromosome ◽  
In Situ Hybridisation ◽  
Fluorescence In Situ Hybridisation ◽  
Form Complex ◽  
Meiotic Chromosomes ◽  
Varietal Variation ◽  
Reference Map ◽  
Allelic Segregation ◽  
Metaphase I

Abstract Naturally occurring autopolyploid species, such as the autotetraploid potato Solanum tuberosum, face a variety of challenges during meiosis. These include proper pairing, recombination and correct segregation of multiple homologous chromosomes, which can form complex multivalent configurations at metaphase I, and in turn alter allelic segregation ratios through double reduction. Here, we present a reference map of meiotic stages in diploid and tetraploid S. tuberosum using fluorescence in situ hybridisation (FISH) to differentiate individual meiotic chromosomes 1 and 2. A diploid-like behaviour at metaphase I involving bivalent configurations was predominant in all three tetraploid varieties. The crossover frequency per bivalent was significantly reduced in the tetraploids compared with a diploid variety, which likely indicates meiotic adaptation to the autotetraploid state. Nevertheless, bivalents were accompanied by a substantial frequency of multivalents, which varied by variety and by chromosome (7–48%). We identified possible sites of synaptic partner switching, leading to multivalent formation, and found potential defects in the polymerisation and/or maintenance of the synaptonemal complex in tetraploids. These findings demonstrate the rise of S. tuberosum as a model for autotetraploid meiotic recombination research and highlight constraints on meiotic chromosome configurations and chiasma frequencies as an important feature of an evolved autotetraploid meiosis.

Sign in / Sign up

Export Citation Format

Share Document