Degenerated, Undifferentiated, Rearranged, Lost: High Variability of Sex Chromosomes in Geometridae (Lepidoptera) Identified by Sex Chromatin

Sex chromatin is a conspicuous body that occurs in polyploid nuclei of most lepidopteran females and consists of numerous copies of the W sex chromosome. It is also a cytogenetic tool used to rapidly assess the W chromosome presence in Lepidoptera. However, certain chromosomal features could disrupt the formation of sex chromatin and lead to the false conclusion that the W chromosome is absent in the respective species. Here we tested the sex chromatin presence in 50 species of Geometridae. In eight selected species with either missing, atypical, or normal sex chromatin patterns, we performed a detailed karyotype analysis by means of comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH). The results showed a high diversity of W chromosomes and clarified the reasons for atypical sex chromatin, including the absence or poor differentiation of W, rearrangements leading to the neo-W emergence, possible association with the nucleolus, and the existence of multiple W chromosomes. In two species, we detected intraspecific variability in the sex chromatin status and sex chromosome constitution. We show that the sex chromatin is not a sufficient marker of the W chromosome presence, but it may be an excellent tool to pinpoint species with atypical sex chromosomes.

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Codling moth cytogenetics: karyotype, chromosomal location of rDNA, and molecular differentiation of sex chromosomes

Genome ◽

10.1139/g05-063 ◽

2005 ◽

Vol 48 (6) ◽

pp. 1083-1092 ◽

Cited By ~ 71

Author(s):

Iva Fuková ◽

Petr Nguyen ◽

František Marec

Keyword(s):

Sex Chromosomes ◽

Sex Chromosome ◽

Codling Moth ◽

Dna Probe ◽

Rrna Genes ◽

Comparative Genomic ◽

W Chromosome ◽

Genomic Hybridization ◽

Molecular Differentiation ◽

Sex Chromatin

We performed a detailed karyotype analysis in the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), the key pest of pome fruit in the temperate regions of the world. The codling moth karyotype consisted of 2n = 56 chromosomes of a holokinetic type. The chromosomes were classified into 5 groups according to their sizes: extra large (3 pairs), large (3 pairs), medium (15 pairs), small (5 pairs), and dot-like (2 pairs). In pachytene nuclei of both sexes, a curious NOR (nucleolar organizer region) bivalent was observed. It carried 2 nucleoli, each associated with one end of the bivalent. FISH with an 18S ribosomal DNA probe confirmed the presence of 2 clusters of rRNA genes at the opposite ends of the bivalent. In accordance with this finding, 2 homologous NOR chromosomes were identified in mitotic metaphase, each showing hybridization signals at both ends. In highly polyploid somatic nuclei, females showed a large heterochromatin body, the so-called sex chromatin or W chromatin. The heterochromatin body was absent in male nuclei, indicating a WZ/ZZ (female/male) sex chromosome system. In keeping with the sex chromatin status, pachytene oocytes showed a sex chromosome bivalent (WZ) that was easily discernible by its heterochromatic W thread. To study molecular differentiation of the sex chromosomes, we employed genomic in situ hybridization (GISH) and comparative genomic hybridization (CGH). GISH detected the W chromosome by strong binding of the Cy3-labelled, female-derived DNA probe. With CGH, both the Cy3-labelled female-derived probe and Fluor-X labelled male-derived probe evenly bound to the W chromosome. This suggested that the W chromosome is predominantly composed of repetitive DNA sequences occurring scattered in other chromosomes but accumulated in the W chromosome. The demonstrated ways of W chromosome identification will facilitate the development of genetic sexing strains desirable for pest control using the sterile insect technique.Key words: CGH, codling moth, FISH, GISH, genomic hybridization, heterochromatin, holokinetic chromosomes, karyotype, NOR, rDNA, SIT, sex chromosomes.

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Sex chromosome pairing and sex chromatin bodies in W–Z translocation strains of Ephestia kuehniella (Lepidoptera)

Genome ◽

10.1139/g94-060 ◽

1994 ◽

Vol 37 (3) ◽

pp. 426-435 ◽

Cited By ~ 27

Author(s):

František Marec ◽

Walther Traut

Keyword(s):

Chromosome Pairing ◽

Sex Chromosomes ◽

Sex Chromosome ◽

Ephestia Kuehniella ◽

Z Chromosome ◽

W Chromosome ◽

Wild Type ◽

Electron Microscopic ◽

Sex Chromatin ◽

Mediterranean Flour Moth

Structure and pairing behavior of sex chromosomes in females of four T(W;Z) lines of the Mediterranean flour moth, Ephestia kuehniella, were investigated using light and electron microscopic techniques and compared with the wild type. In light microscopic preparations of pachytene oocytes of wild-type females, the WZ bivalent stands out by its heterochromatic W chromosome strand. In T(W;Z) females, the part of the Z chromosome that was translated onto the W chromosome was demonstrated as a distal segment of the neo-W chromosome, displaying a characteristic non-W chromosomal chromomere–interchromomere pattern. This segment is homologously paired with the corresponding part of a complete Z chromosome. In contrast with the single ball of heterochromatic W chromatin in highly polyploid somatic nuclei of wild-type females, the translocation causes the formation of deformed or fragmented W chromatin bodies, probably owing to opposing tendencies of the Z and W chromosomal parts of the neo-W. In electron microscopic preparations of microspread nuclei, sex chromosome bivalents were identified by the remnants of electron-dense heterochromatin tangles decorating the W chromosome axis, by the different lengths of the Z and W chromosome axes, and by incomplete pairing. No heterochromatin tangles were attached to the translocated segment of the Z chromosome at one end of the neo-W chromosome. Because of the homologous pairing between the translocation and the structurally normal Z chromosome, pairing affinity of sex chromosomes in T(W;Z) females is significantly improved. Specific differences observed among T(W;Z)1–4 translocations are probably due to the different lengths of the translocated segments.Key words: Mediterranean flour moth, sex chromosomes, sex chromatin, translocations, synaptonemal complexes, microspreading.

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Patterns of Sex Chromosome Differentiation in Spiders: Insights from Comparative Genomic Hybridisation

Genes ◽

10.3390/genes11080849 ◽

2020 ◽

Vol 11 (8) ◽

pp. 849

Author(s):

Alexandr Sember ◽

Michaela Pappová ◽

Martin Forman ◽

Petr Nguyen ◽

František Marec ◽

...

Keyword(s):

X Chromosome ◽

Sex Chromosomes ◽

Sex Chromosome ◽

Intraspecific Variability ◽

Comparative Genomic Hybridisation ◽

Comparative Genomic ◽

Chromosome Differentiation ◽

Molecular Differentiation ◽

Y Chromosomes ◽

Cryptic Sex

Spiders are an intriguing model to analyse sex chromosome evolution because of their peculiar multiple X chromosome systems. Y chromosomes were considered rare in this group, arising after neo-sex chromosome formation by X chromosome-autosome rearrangements. However, recent findings suggest that Y chromosomes are more common in spiders than previously thought. Besides neo-sex chromosomes, they are also involved in the ancient X1X2Y system of haplogyne spiders, whose origin is unknown. Furthermore, spiders seem to exhibit obligatorily one or two pairs of cryptic homomorphic XY chromosomes (further cryptic sex chromosome pairs, CSCPs), which could represent the ancestral spider sex chromosomes. Here, we analyse the molecular differentiation of particular types of spider Y chromosomes in a representative set of ten species by comparative genomic hybridisation (CGH). We found a high Y chromosome differentiation in haplogyne species with X1X2Y system except for Loxosceles spp. CSCP chromosomes exhibited generally low differentiation. Possible mechanisms and factors behind the observed patterns are discussed. The presence of autosomal regions marked predominantly or exclusively with the male or female probe was also recorded. We attribute this pattern to intraspecific variability in the copy number and distribution of certain repetitive DNAs in spider genomes, pointing thus to the limits of CGH in this arachnid group. In addition, we confirmed nonrandom association of chromosomes belonging to particular CSCPs at spermatogonial mitosis and spermatocyte meiosis and their association with multiple Xs throughout meiosis. Taken together, our data suggest diverse evolutionary pathways of molecular differentiation in different types of spider Y chromosomes.

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Absence of W Chromosome in Psychidae Moths and Implications for the Theory of Sex Chromosome Evolution in Lepidoptera

Genes ◽

10.3390/genes10121016 ◽

2019 ◽

Vol 10 (12) ◽

pp. 1016

Author(s):

Martina Hejníčková ◽

Petr Koutecký ◽

Pavel Potocký ◽

Irena Provazníková ◽

Anna Voleníková ◽

...

Keyword(s):

Genome Size ◽

Sex Chromosome ◽

Phylogenetic Position ◽

Z Chromosome ◽

Comparative Genomic ◽

W Chromosome ◽

Sex Chromatin ◽

Sex Chromosome System ◽

The Common ◽

Female Specific

Moths and butterflies (Lepidoptera) are the largest group with heterogametic females. Although the ancestral sex chromosome system is probably Z0/ZZ, most lepidopteran species have the W chromosome. When and how the W chromosome arose remains elusive. Existing hypotheses place the W origin either at the common ancestor of Ditrysia and Tischeriidae, or prefer independent origins of W chromosomes in these two groups. Due to their phylogenetic position at the base of Ditrysia, bagworms (Psychidae) play an important role in investigating the W chromosome origin. Therefore, we examined the W chromosome status in three Psychidae species, namely Proutia betulina, Taleporia tubulosa, and Diplodoma laichartingella, using both classical and molecular cytogenetic methods such as sex chromatin assay, comparative genomic hybridization (CGH), and male vs. female genome size comparison by flow cytometry. In females of all three species, no sex chromatin was found, no female-specific chromosome regions were revealed by CGH, and a Z-chromosome univalent was observed in pachytene oocytes. In addition, the genome size of females was significantly smaller than males. Overall, our study provides strong evidence for the absence of the W chromosome in Psychidae, thus supporting the hypothesis of two independent W chromosome origins in Tischeriidae and in advanced Ditrysia.

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The Diversity and Evolution of Sex Chromosomes in Frogs

Genes ◽

10.3390/genes12040483 ◽

2021 ◽

Vol 12 (4) ◽

pp. 483

Author(s):

Wen-Juan Ma ◽

Paris Veltsos

Keyword(s):

Sex Determination ◽

Sex Chromosomes ◽

Chromosome Evolution ◽

Sex Chromosome ◽

Comparative Genomic ◽

Ancestral State ◽

Heteromorphic Sex Chromosomes ◽

Genomic Studies ◽

Evolutionary Trajectories ◽

Heterogametic Sex

Frogs are ideal organisms for studying sex chromosome evolution because of their diversity in sex chromosome differentiation and sex-determination systems. We review 222 anuran frogs, spanning ~220 Myr of divergence, with characterized sex chromosomes, and discuss their evolution, phylogenetic distribution and transitions between homomorphic and heteromorphic states, as well as between sex-determination systems. Most (~75%) anurans have homomorphic sex chromosomes, with XY systems being three times more common than ZW systems. Most remaining anurans (~25%) have heteromorphic sex chromosomes, with XY and ZW systems almost equally represented. There are Y-autosome fusions in 11 species, and no W-/Z-/X-autosome fusions are known. The phylogeny represents at least 19 transitions between sex-determination systems and at least 16 cases of independent evolution of heteromorphic sex chromosomes from homomorphy, the likely ancestral state. Five lineages mostly have heteromorphic sex chromosomes, which might have evolved due to demographic and sexual selection attributes of those lineages. Males do not recombine over most of their genome, regardless of which is the heterogametic sex. Nevertheless, telomere-restricted recombination between ZW chromosomes has evolved at least once. More comparative genomic studies are needed to understand the evolutionary trajectories of sex chromosomes among frog lineages, especially in the ZW systems.

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ZZ/ZW Sex Determination with Multiple Neo-Sex Chromosomes is Common in Madagascan Chameleons of the Genus Furcifer (Reptilia: Chamaeleonidae)

Genes ◽

10.3390/genes10121020 ◽

2019 ◽

Vol 10 (12) ◽

pp. 1020 ◽

Cited By ~ 3

Author(s):

Rovatsos ◽

Altmanová ◽

Augstenová ◽

Mazzoleni ◽

Velenský ◽

...

Keyword(s):

Sex Determination ◽

Sex Chromosomes ◽

Comparative Genomic ◽

Telomeric Sequences ◽

Female Heterogamety ◽

Chromosomal Variability ◽

Determination System ◽

Hybridization In Situ ◽

Sex Determination System

Chameleons are well-known, highly distinctive lizards characterized by unique morphological and physiological traits, but their karyotypes and sex determination system have remained poorly studied. We studied karyotypes in six species of Madagascan chameleons of the genus Furcifer by classical (conventional stain, C-banding) and molecular (comparative genomic hybridization, in situ hybridization with rDNA, microsatellite, and telomeric sequences) cytogenetic approaches. In contrast to most sauropsid lineages, the chameleons of the genus Furcifer show chromosomal variability even among closely related species, with diploid chromosome numbers varying from 2n = 22 to 2n = 28. We identified female heterogamety with cytogenetically distinct Z and W sex chromosomes in all studied species. Notably, multiple neo-sex chromosomes in the form Z1Z1Z2Z2/Z1Z2W were uncovered in four species of the genus (F. bifidus, F. verrucosus, F. willsii, and previously studied F. pardalis). Phylogenetic distribution and morphology of sex chromosomes suggest that multiple sex chromosomes, which are generally very rare among vertebrates with female heterogamety, possibly evolved several times within the genus Furcifer. Although acrodontan lizards (chameleons and dragon lizards) demonstrate otherwise notable variability in sex determination, it seems that female heterogamety with differentiated sex chromosomes remained stable in the chameleons of the genus Furcifer for about 30 million years.

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The influence of the Robertsonian translocation Rb(X.2)2Ad on anaphase I non-disjunction in male laboratory mice

Genetics Research ◽

10.1017/s0016672300027944 ◽

1989 ◽

Vol 53 (2) ◽

pp. 77-86 ◽

Cited By ~ 14

Author(s):

I.-D. Adler ◽

R. Johannisson ◽

H. Winking

Keyword(s):

Sex Chromosomes ◽

Robertsonian Translocation ◽

Sex Chromosome ◽

Light And Electron Microscopy ◽

Normal Karyotype ◽

Chromosome 2 ◽

Male Genome ◽

The Difference ◽

Normal Pairing

SummaryA Robertsonian translocation in the mouse between theXchromosome and chromosome 2 is described. The male and female carriers of the Rb(X.2)2Ad were fertile. A homozygous/hemizygous line was maintained. The influence of theX-autosomal Robertsonian translocation on anaphase I non-disjunction in male mice was studied by chromosome counts in cells at metaphase II of meoisis and by assessment of aneuploid progeny. The results conclusively show that the inclusion of Rb2Ad in the male genome induces non-disjunction at the first meoitic division. In second metaphase cells the frequency of sex-chromosomal aneuploidy was 10·8%, and secondary spermatocytes containing two or no sex chromosome were equally frequent. The Rb2Ad males sired 3·9% sex-chromosome aneuploid progeny. The difference in aneuploidy frequencies in the germ cells and among the progeny suggests that the viability of XO and XXY individuals is reduced. The pairing configurations of chromosomes 2, Rb2Ad andYwere studied during meiotic prophase by light and electron microscopy. Trivalent pairing was seen in all well spread nuclei. Complete pairing of the acrocentric autosome 2 with the corresponding segment of the Rb2Ad chromosome was only seen in 3·2% of the cells analysed in the electron microscope. The pairing between theXand theYchromosome in the Rb2Ad males corresponded to that in males with normal karyotype. Reasons for sex-chromosomal non-disjunction despite the normal pairing pattern between the sex chromosomes may be seen in the terminal chiasma location coupled with the asynchronous separation of the sex chromosomes and the autosomes. The Rb2Ad chromosome can be useful for studies ofXinactivation, as a marker for parental derivation of theXchromosome and for mapping loci byin situhybridization.

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Chromosomal Spreading of Microsatellites and (TTAGGG)n Sequences in the Characidium zebra and C. gomesi Genomes (Characiformes: Crenuchidae)

Cytogenetic and Genome Research ◽

10.1159/000447959 ◽

2016 ◽

Vol 149 (3) ◽

pp. 182-190 ◽

Cited By ~ 12

Author(s):

Marcela B. Pucci ◽

Patricia Barbosa ◽

Viviane Nogaroto ◽

Mara C. Almeida ◽

Roberto F. Artoni ◽

...

Keyword(s):

Repetitive Dna ◽

Sex Chromosomes ◽

Dna Sequences ◽

Tandem Repeats ◽

Additional Data ◽

Sex Chromosome ◽

Binding Motif ◽

W Chromosome ◽

Repeat Sequences ◽

Heteromorphic Sex Chromosomes

Sex chromosome evolution involves the accumulation of repeat sequences such as multigenic families, noncoding repetitive DNA (satellite, minisatellite, and microsatellite), and mobile elements such as transposons and retrotransposons. Most species of Characidium exhibit heteromorphic ZZ/ZW sex chromosomes; the W is characterized by an intense accumulation of repetitive DNA including dispersed satellite DNA sequences and transposable elements. The aim of this study was to analyze the distribution pattern of 18 different tandem repeats, including (GATA)n and (TTAGGG)n, in the genomes of C. zebra and C. gomesi, especially in the C. gomesi W chromosome. In the C. gomesi W chromosome, weak signals were seen for (CAA)10, (CAC)10, (CAT)10, (CGG)10, (GAC)10, and (CA)15 probes. (GA)15 and (TA)15 hybridized to the autosomes but not to the W chromosome. The (GATA)n probe hybridized to the short arms of the W chromosome as well as the (CG)15 probe. The (GATA)n repeat is known to be a protein-binding motif. GATA-binding proteins are necessary for the decondensation of heterochromatic regions that hold coding genes, especially in some heteromorphic sex chromosomes that may keep genes related to oocyte development. The (TAA)10 repeat is accumulated in the entire W chromosome, and this microsatellite accumulation is probably involved in the sex chromosome differentiation process and crossover suppression in C. gomesi. These additional data on the W chromosome DNA composition help to explain the evolution of sex chromosomes in Characidium.

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Whole-chromosome fusions in the karyotype evolution of Sceloporus (Iguania, Reptilia) are more frequent in sex chromosomes than autosomes

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2020.0099 ◽

2021 ◽

Vol 376 (1833) ◽

pp. 20200099

Author(s):

Artem P. Lisachov ◽

Katerina V. Tishakova ◽

Svetlana A. Romanenko ◽

Anna S. Molodtseva ◽

Dmitry Yu. Prokopov ◽

...

Keyword(s):

Sex Chromosomes ◽

Recombination Rate ◽

Complex Analysis ◽

Chromosome Evolution ◽

Sex Chromosome ◽

Comparative Genomic ◽

Synaptonemal Complex Analysis ◽

Chromosome Fusions ◽

Chromosome Formation ◽

Pseudoautosomal Regions

Whole-chromosome fusions play a major role in the karyotypic evolution of reptiles. It has been suggested that certain chromosomes tend to fuse with sex chromosomes more frequently than others. However, the comparative genomic synteny data are too scarce to draw strong conclusions. We obtained and sequenced chromosome-specific DNA pools of Sceloporus malachiticus , an iguanian species which has experienced many chromosome fusions. We found that four of seven lineage-specific fusions involved sex chromosomes, and that certain syntenic blocks which constitute the sex chromosomes, such as the homologues of the Anolis carolinensis chromosomes 11 and 16, are repeatedly involved in sex chromosome formation in different squamate species. To test the hypothesis that the karyotypic shift could be associated with changes in recombination patterns, we performed a synaptonemal complex analysis in this species and in Sceloporus variabilis (2 n = 34). It revealed that the sex chromosomes in S. malachiticus had two distal pseudoautosomal regions and a medial differentiated region. We found that multiple fusions little affected the recombination rate in S. malachiticus . Our data confirm more frequent involvement of certain chromosomes in sex chromosome formation, but do not reveal a connection between the gonosome–autosome fusions and the evolution of recombination rate. This article is part of the theme issue ‘Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part II)’.

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A frog with three sex chromosomes that co-mingle together in nature: Xenopus tropicalis has a degenerate W and a Y that evolved from a Z chromosome

PLoS Genetics ◽

10.1371/journal.pgen.1009121 ◽

2020 ◽

Vol 16 (11) ◽

pp. e1009121

Author(s):

Benjamin L. S. Furman ◽

Caroline M. S. Cauret ◽

Martin Knytl ◽

Xue-Ying Song ◽

Tharindu Premachandra ◽

...

Keyword(s):

Sex Differences ◽

Y Chromosome ◽

Sex Chromosomes ◽

Sexual Differentiation ◽

Sex Chromosome ◽

Xenopus Tropicalis ◽

Z Chromosome ◽

W Chromosome ◽

Recombination Suppression ◽

Determining Factor

In many species, sexual differentiation is a vital prelude to reproduction, and disruption of this process can have severe fitness effects, including sterility. It is thus interesting that genetic systems governing sexual differentiation vary among—and even within—species. To understand these systems more, we investigated a rare example of a frog with three sex chromosomes: the Western clawed frog, Xenopus tropicalis. We demonstrate that natural populations from the western and eastern edges of Ghana have a young Y chromosome, and that a male-determining factor on this Y chromosome is in a very similar genomic location as a previously known female-determining factor on the W chromosome. Nucleotide polymorphism of expressed transcripts suggests genetic degeneration on the W chromosome, emergence of a new Y chromosome from an ancestral Z chromosome, and natural co-mingling of the W, Z, and Y chromosomes in the same population. Compared to the rest of the genome, a small sex-associated portion of the sex chromosomes has a 50-fold enrichment of transcripts with male-biased expression during early gonadal differentiation. Additionally, X. tropicalis has sex-differences in the rates and genomic locations of recombination events during gametogenesis that are similar to at least two other Xenopus species, which suggests that sex differences in recombination are genus-wide. These findings are consistent with theoretical expectations associated with recombination suppression on sex chromosomes, demonstrate that several characteristics of old and established sex chromosomes (e.g., nucleotide divergence, sex biased expression) can arise well before sex chromosomes become cytogenetically distinguished, and show how these characteristics can have lingering consequences that are carried forward through sex chromosome turnovers.

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