Localized recombination nodules and sex chromosome behavior in the male mole cricket, Neocurtilla hexadactyla

Genome ◽  
1989 ◽  
Vol 32 (2) ◽  
pp. 275-281 ◽  
Author(s):  
B. Spyropoulos ◽  
D. Wise ◽  
P. B. Moens
Keyword(s):  
Synaptonemal Complex ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Chromosome X ◽  
Chromosome Behavior ◽  
Autosomal Bivalents ◽  
Electron Dense Material ◽  
Recombination Nodules ◽  
The Third ◽  
Mole Cricket

During meiotic prophase, the 10 metacentric autosomal bivalents of the mole cricket, Neocurtilla hexadactyla Perty, formed synaptonemal complexes only at their ends. These complexes were of similar morphology to those of other species. Virtually all of these distal synaptonemal complex segments contained one or more recombination nodules. There was complete correlation between the locations of the synaptonemal complex segments at pachytene and chiasmata at diplotene. The sex chromosomal bivalent X2 and Y, formed a synaptonemal complex at one end only. While no apparent physical or spatial connection was found during prophase between the X2Y bivalent and the third sex chromosome, X1, electron-dense material covered the centromeres of X1 and Y and to a lesser extent X2, thus differentiating the centromeres of the sex chromosomes from those of the autosomes.Key words: localised pairing, recombination nodules, chiasmata, sex chromosomes.

Chromosomal synapsis and the meiotic process in male mesquite lizards, Sceloporus grammicus complex

Genome ◽  
1992 ◽  
Vol 35 (3) ◽  
pp. 398-408 ◽  
Author(s):  
Kent M. Reed ◽  
Jack W. Sites Jr. ◽  
Ira F. Greenbaum
Keyword(s):  
Synaptonemal Complex ◽  
Sex Chromosomes ◽  
Meiotic Prophase ◽  
Morphological Characterization ◽  
Autosomal Bivalents ◽  
Meiotic Process ◽  
Low Levels ◽  
Sceloporus Grammicus ◽  
Metaphase I

Meiosis in males of the F5 cytotype of Sceloporus grammicus was examined through the analysis of synaptonemal complexes (SCs), diakinetic (metaphase I) nuclei, and secondary spermatocytes (metaphase II configurations). These data allowed the establishment of criteria for substaging of zygonema and pachynema, morphological characterization of the SC complement, and comparison of the orientation and segregation of the autosomes and sex chromosomes. The analysis of nuclei from all stages of meiotic prophase I (leptonema through diakinesis) provided a useful means of partitioning the temporal sequence of early meiotic events. Three substages of zygonema (Z1–Z3) were established, based on the extent of synapsis of the microchromosomal and macrochromosomal elements. Synaptic initiation of the autosomes and sex chromosomes was synchronous. Two patterns of macrochromosomal synapsis were observed. Whereas synapsis of the biarmed elements was biterminal (i.e., progressing from both ends of the homologs), synapsis of the acrocentric elements was uniterminal involving only the distal (noncentromeric) ends of the homologs. Unique sex-chromosomal characteristics were not observed in S. grammicus and, therefore, the substaging of pachynema was based on subjective criteria. Examination of diakinesis – metaphase I and metaphase II configurations indicated low levels of diakinetic irregularities with balanced segregation of the autosomal bivalents and the sex-chromosomal trivalent.Key words: Sceloporus grammicus, meiosis, synaptonemal complex, substaging.

Ultrastructural analysis of the X1X2X3O sex chromosome system during the spermatogenesis of Tegenaria domestica (Arachnida)

1982 ◽  
Vol 58 (1) ◽  
pp. 411-422
Author(s):  
R. Benavente ◽  
R. Wettstein ◽  
M. Papa
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Sex Chromosomes ◽  
Ultrastructural Study ◽  
Chromosome Structure ◽  
Sex Chromosome ◽  
X Chromosomes ◽  
Sex Chromosome System ◽  
Available Information ◽  
Dense Chromatin

An ultrastructural study was performed on the sex chromosomes (male X1X2X3O) during the spermatogenesis of Tegenaria domestica (Arachnida, Agelenidae). This study was carried out using random and serially cut sections. During pachytene and diplotene the three X chromosomes are longitudinally paired. Each of these consists of a central core of condensed chromatin, surrounded by a field of dense chromatin projections through which the chromosomes are in contact with one another. These projections may be responsible for the recognition and pairing of the sex chromosomes and in some way participate in their non-disjunction during anaphase I. A study of the structure and behaviour of the sex chromosomes during spermatogenesis is also presented. The available information on non-synaptonemal complex-mediated chromosome pairing and a systematization of sex chromosome structure in spiders are discussed.

Pattern of X–Y chromosome pairing in the Japanese field vole, Microtus montebelli

Genome ◽  
1997 ◽  
Vol 40 (6) ◽  
pp. 829-833 ◽  
Author(s):  
P. M. Borodin ◽  
M. B. Rogatcheva ◽  
K. Koyasu ◽  
K. Fukuta ◽  
K. Mekada ◽  
...  
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Chromosomal Evolution ◽  
The Other ◽  
Field Vole ◽  
Y Chromosomes ◽  
The One ◽  
Ancestral Type

Pairing of X and Y chromosomes at meiotic prophase in males of Microtus montebelli was analyzed. The sex chromosomes form a synaptonemal complex at pachytene and end-to-end association at diakinesis – metaphase I in two species of the genus Microtus (M. montebelli and M. oeconomus) only, while they do not pair at all in the other species of this genus that have been studied so far. These data confirm that M. montebelli and M. oeconomus are very closely related in their origin. It is suggested that the sex chromosomes of M. montebelli and M. oeconomus display the ancestral type of X–Y pairing. The lack of X–Y pairing in most species of Microtus appeared after the split in lineage that led to M. oeconomus and M. montebelli on the one hand and the remaining species on the other.Key words: Microtus montebelli, arvicoline phylogeny, synaptic sex chromosome, synaptonemal complex, chromosomal evolution.

Synaptonemal complexes of triploid (ZZW) chickens: Z–Z pairing predominates over Z–W pairing

Genome ◽  
1991 ◽  
Vol 34 (5) ◽  
pp. 718-726 ◽  
Author(s):  
Alberto J. Solari ◽  
M. H. Thorne ◽  
B. L. Sheldon ◽  
C. B. Gillies
Keyword(s):  
Synaptonemal Complex ◽  
Central Region ◽  
Sex Chromosomes ◽  
W Chromosome ◽  
Synaptonemal Complexes ◽  
Early Pachytene ◽  
Recombination Nodule ◽  
Recombination Nodules ◽  
Central Regions ◽  
Partial Elimination

Twelve triploid, ZZW chickens of ages ranging from day 19 of incubation to 15 days after hatching were used for oocyte analysis. Oocytes show 117 axes per nucleus. At early pachytene, most axes form double synaptonemal complexes (triplets). An average of 27 triplets, 12 bivalents, and 12 univalents was observed. Later, a partial elimination of triplets occurs, as they are converted into typical trivalents or bivalents and univalents. The number of recombination nodules per nucleus (52.7) is similar to that of diploids. These nodules can occur in register in both central regions of a triplet (no lateral interference), and they probably stabilize the central region. Among 31 oocytes, 29 had a regular ZZ bivalent and a W univalent, and only 2 had triple pairing between a ZZ bivalent and a terminal region of the W axis (less than 1 μm in length and having a terminal recombination nodule). Competition for pairing between the gonosomes results in a large (93.5% of cases) predominance of Z–Z pairing, because of a relatively minor homology between the W and Z chromosomes. The prevailing pairing failure of the W chromosome may lead to early oocyte loss.Key words: sex chromosomes, triploids, synaptonemal complex, Z–W pairing, chicken, recombination nodules.

Synaptonemal complex analysis in spermatocytes of tilapia, Oreochromis niloticus (Pisces, Cichlidae)

Genome ◽  
1993 ◽  
Vol 36 (6) ◽  
pp. 1124-1128 ◽  
Author(s):  
Fausto Foresti ◽  
Claudio Oliveira ◽  
Pedro Manoel Galetti Junior ◽  
Lurdes Foresti de Almeida-Toledo
Keyword(s):  
Synaptonemal Complex ◽  
Sex Chromosomes ◽  
Oreochromis Niloticus ◽  
Complex Analysis ◽  
Sex Chromosome ◽  
Light And Electron Microscopy ◽  
Nucleolus Organizer ◽  
Nucleolus Organizer Regions ◽  
Synaptonemal Complex Analysis ◽  
Sex Chromosome System

Some adaptations of the synaptonemal complex (SC) whole-mounting technique first used in plants permitted its application to meiotic studies in tilapia, Oreochromis niloticus. Direct observation of the chromosome pairing process and bivalent structure during the meiotic prophase of this fish species by light and electron microscopy permitted the analysis of SCs in autosomes and the possible identification of sex chromosomes. The analysis of SCs in spermatocytes of O. niloticus revealed that all 22 bivalent chromosomes completely paired, except for the occurrence of a size heteromorphism in the terminal region of the largest bivalent associated with the presence of an incompletely paired segment during the synapsis process, which may be the cytological visualization of an XX/XY sex chromosome system in this species.Key words: fish cytogenetics, synaptonemal complex, fish meiosis, sex chromosomes, nucleolus organizer regions.

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.

Heteromorphism of “Homomorphic” Sex Chromosomes in Two Anole Species (Squamata, Dactyloidae) Revealed by Synaptonemal Complex Analysis

2017 ◽  
Vol 151 (2) ◽  
pp. 89-95 ◽  
Author(s):  
Artem P. Lisachov ◽  
Vladimir A. Trifonov ◽  
Massimo Giovannotti ◽  
Malcolm A. Ferguson-Smith ◽  
Pavel M. Borodin
Keyword(s):  
Sex Chromosomes ◽  
Complex Analysis ◽  
Sex Chromosome ◽  
Meiotic Chromosome ◽  
Fluorescent Microscopy ◽  
Chromosome Analysis ◽  
Pseudoautosomal Region ◽  
Metaphase Chromosomes ◽  
Recombination Nodules ◽  
Surface Spread

Iguanians (Pleurodonta) are one of the reptile lineages that, like birds and mammals, have sex chromosomes of ancient origin. In most iguanians these are microchromosomes, making a distinction between the X and Y as well as between homeologous sex chromosomes in other species difficult. Meiotic chromosome analysis may be used to elucidate their differentiation, because meiotic prophase chromosomes are longer and less condensed than metaphase chromosomes, and the homologues are paired with each other, revealing minor heteromorphisms. Using electron and fluorescent microscopy of surface spread synaptonemal complexes (SCs) and immunolocalization of the proteins of the SC (SYCP3), the centromere, and recombination nodules (MLH1), we examined sex chromosome synapsis and recombination in 2 species of anoles (Dactyloidae), Anolis carolinensis and Deiroptyx coelestinus, in which the sex chromosomes represent the ancestral condition of iguanians. We detected clear differences in size between the anole X and Y microchromosomes and found an interspecies difference in the localization of the pseudoautosomal region. Our results show that the apparent homomorphy of certain reptile sex chromosome systems can hide a cryptic differentiation, which potentially may influence the evolution of sexual dimorphism and speciation.

scholarly journals Sex Chromosome Turnover in Bent-Toed Geckos (Cyrtodactylus)

Genes ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 116
Author(s):  
Shannon E. Keating ◽  
Madison Blumer ◽  
L. Lee Grismer ◽  
Aung Lin ◽  
Stuart V. Nielsen ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
The Third

Lizards and snakes (squamates) are known for their varied sex determining systems, and gecko lizards are especially diverse, having evolved sex chromosomes independently multiple times. While sex chromosomes frequently turnover among gecko genera, intrageneric turnovers are known only from Gekko and Hemidactylus. Here, we used RADseq to identify sex-specific markers in two species of Burmese bent-toed geckos. We uncovered XX/XY sex chromosomes in Cyrtodactylus chaunghanakwaensis and ZZ/ZW sex chromosomes in Cyrtodactylus pharbaungensis. This is the third instance of intrageneric turnover of sex chromosomes in geckos. Additionally, Cyrtodactylus are closely related to another genus with intrageneric turnover, Hemidactylus. Together, these data suggest that sex chromosome turnover may be common in this clade, setting them apart as exceptionally diverse in a group already known for diverse sex determination systems.

scholarly journals Differential Gene Expression between Fungal Mating Types Is Associated with Sequence Degeneration

2020 ◽  
Vol 12 (4) ◽  
pp. 243-258 ◽  
Author(s):  
Wen-Juan Ma ◽  
Fantin Carpentier ◽  
Tatiana Giraud ◽  
Michael E Hood
Keyword(s):  
Differential Expression ◽  
Differentially Expressed Genes ◽  
Mating Type ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Gc Content ◽  
Differentially Expressed ◽  
Mating Types ◽  
Sexual Antagonism ◽  
Recombination Suppression

Abstract Degenerative mutations in non-recombining regions, such as in sex chromosomes, may lead to differential expression between alleles if mutations occur stochastically in one or the other allele. Reduced allelic expression due to degeneration has indeed been suggested to occur in various sex-chromosome systems. However, whether an association occurs between specific signatures of degeneration and differential expression between alleles has not been extensively tested, and sexual antagonism can also cause differential expression on sex chromosomes. The anther-smut fungus Microbotryum lychnidis-dioicae is ideal for testing associations between specific degenerative signatures and differential expression because 1) there are multiple evolutionary strata on the mating-type chromosomes, reflecting successive recombination suppression linked to mating-type loci; 2) separate haploid cultures of opposite mating types help identify differential expression between alleles; and 3) there is no sexual antagonism as a confounding factor accounting for differential expression. We found that differentially expressed genes were enriched in the four oldest evolutionary strata compared with other genomic compartments, and that, within compartments, several signatures of sequence degeneration were greater for differentially expressed than non-differentially expressed genes. Two particular degenerative signatures were significantly associated with lower expression levels within differentially expressed allele pairs: upstream insertion of transposable elements and mutations truncating the protein length. Other degenerative mutations associated with differential expression included nonsynonymous substitutions and altered intron or GC content. The association between differential expression and allele degeneration is relevant for a broad range of taxa where mating compatibility or sex is determined by genes located in large regions where recombination is suppressed.

Evolution of Sex Chromosome Heteromorphy in Geographic Populations of the Japanese Tago’s Brown Frog Complex

2021 ◽  
pp. 1-9
Author(s):  
Chiao Kuwana ◽  
Hiroyuki Fujita ◽  
Masataka Tagami ◽  
Takanori Matsuo ◽  
Ikuo Miura
Keyword(s):  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Mitochondrial Gene ◽  
Population Level ◽  
Chromosome 7 ◽  
Geographic Population ◽  
Geographic Populations ◽  
Western Japan ◽  
Brown Frog ◽  
Eastern Japan

The sex chromosomes of most anuran amphibians are characterized by homomorphy in both sexes, and evolution to heteromorphy rarely occurs at the species or geographic population level. Here, we report sex chromosome heteromorphy in geographic populations of the Japanese Tago’s brown frog complex (2n = 26), comprising Rana sakuraii and R. tagoi. The sex chromosomes of R. sakuraii from the populations in western Japan were homomorphic in both sexes, whereas chromosome 7 from the populations in eastern Japan were heteromorphic in males. Chromosome 7 of R. tagoi, which is distributed close to R. sakuraii in eastern Japan, was highly similar in morphology to the Y chromosome of R. sakuraii. Based on this and on mitochondrial gene sequence analysis, we hypothesize that in the R. sakuraii populations from eastern Japan the XY heteromorphic sex chromosome system was established by the introduction of chromosome 7 from R. tagoi via interspecies hybridization. In contrast, chromosome 13 of R. tagoi from the 2 large islands in western Japan, Shikoku and Kyushu, showed a heteromorphic pattern of constitutive heterochromatin distribution in males, while this pattern was homomorphic in females. Our study reveals that sex chromosome heteromorphy evolved independently at the geographic lineage level in this species complex.

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