XX:XY sex chromosome system with X heterochromatinization: an early stage of sex chromosome differentiation in the Neotropic electric eel Eigenmannia virescens

2001 ◽  
Vol 95 (1-2) ◽  
pp. 73-78 ◽  
Author(s):  
L.F. de Almeida-Toledo ◽  
F. Foresti ◽  
E.V. Péquignot ◽  
M.F.Z. Daniel-Silva
Keyword(s):  
Sex Chromosome ◽  
Early Stage ◽  
Chromosome Differentiation ◽  
Electric Eel ◽  
Sex Chromosome System ◽  
Eigenmannia Virescens

scholarly journals Extreme heterogeneity in sex chromosome differentiation and dosage compensation in livebearers

2019 ◽  
Author(s):  
Iulia Darolti ◽  
Alison E. Wright ◽  
Benjamin A. Sandkam ◽  
Jake Morris ◽  
Natasha I. Bloch ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Dosage Compensation ◽  
Sex Chromosomes ◽  
Poecilia Reticulata ◽  
Sex Chromosome ◽  
Sequencing Data ◽  
Chromosome Differentiation ◽  
Shared Ancestry ◽  
Sex Chromosome System ◽  
Suppressed Recombination

ABSTRACTOnce recombination is halted between the X and Y chromosome, sex chromosomes begin to differentiate and transition to heteromorphism. While there is a remarkable variation across clades in the degree of sex chromosome divergence, far less is known about variation in sex chromosome differentiation within clades. Here, we combined whole genome and transcriptome sequencing data to characterise the structure and conservation of sex chromosome systems across Poeciliidae, the livebearing clade that includes guppies. We found that the Poecilia reticulata XY system is much older than previously thought, being shared not only with its sister species, Poecilia wingei, but also with Poecilia picta, which diverged 30 mya. Despite the shared ancestry, we uncovered an extreme heterogeneity across these species in the proportion of the sex chromosome with suppressed recombination, and the degree of Y chromosome decay. The sex chromosomes in P. reticulata are largely homomorphic, with recombination persisting over a substantial fraction. However, the sex chromosomes in P. picta are completely non-recombining and strikingly heteromorphic. ln addition to being highly divergent, the sex chromosome system in P. picta includes a neo-sex chromosome, the result of a fusion between the ancestral sex chromosome and part of chromosome 7. Remarkably, the profound degradation of the ancestral Y chromosome in P. picta is counterbalanced by the evolution of complete dosage compensation in this species, the first such documented case in teleost fish. Our results offer important insight into the initial stages of sex chromosome evolution and dosage compensation.

scholarly journals Sex Chromosome Heteromorphism and the Fast-X Effect in Poeciliids

2021 ◽  
Author(s):  
Iulia Darolti ◽  
Lydia J. M. Fong ◽  
Judith E. Mank
Keyword(s):  
X Chromosome ◽  
Sex Chromosomes ◽  
Poecilia Reticulata ◽  
Sex Chromosome ◽  
Comparative Approach ◽  
Sequence Evolution ◽  
Chromosome Differentiation ◽  
Poeciliid Fish ◽  
Sex Chromosome System ◽  
Chromosome Heteromorphism

AbstractAn accelerated rate of sequence evolution on the X chromosome compared to autosomes, known as Fast-X evolution, has been observed in a range of heteromorphic sex chromosomes. However, it remains unclear how early in the process of sex chromosome differentiation the Fast-X effect becomes detectible. Recently, we uncovered an extreme variation in sex chromosome heteromorphism across Poeciliid fish species. The common guppy, Poecilia reticulata, Endler’s guppy, P. wingei, and the swamp guppy, P. picta, appear to share the same XY system and exhibit a remarkable range of heteromorphism. The sex chromosome system is absent in recent outgroups, including P. latipinna and Gambusia holbrooki. We combined analyses of sequence divergence and polymorphism data across Poeciliids to investigate X chromosome evolution as a function of hemizygosity and reveal the causes for Fast-X effects. Consistent with the extent of Y degeneration in each species, we detect higher rates of divergence on the X relative to autosomes and a strong Fast-X effect in P. picta, while no change in the rate of evolution of X-linked relative to autosomal genes in P. reticulata. In P. wingei, the species with intermediate sex chromosome differentiation, we see an increase in the rate of nonsynonymous substitutions on the older stratum of divergence only. We also use our comparative approach to test different models for the origin of the sex chromosomes in this clade. Taken together, our study reveals an important role of hemizygosity in Fast-X and suggests a single, recent origin of the sex chromosome system in this clade.

scholarly journals Cytogenetic characterization of Hypostomus soniae Hollanda-Carvalho & Weber, 2004 from the Teles Pires River, southern Amazon basin: evidence of an early stage of an XX/XY sex chromosome system

2019 ◽  
Vol 13 (4) ◽  
pp. 411-422 ◽  
Author(s):  
Luciene Castuera de Oliveira ◽  
Marcos Otávio Ribeiro ◽  
Gerlane de Medeiros Costa ◽  
Cláudio Henrique Zawadzki ◽  
Ana Camila Prizon-Nakajima ◽  
...  
Keyword(s):  
Amazon Basin ◽  
Sex Chromosome ◽  
Early Stage ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Structural Difference ◽  
Chromosomal Polymorphism ◽  
Nucleolus Organizer ◽  
Rdna Sites ◽  
Sex Chromosome System

In the present study, we analyzed individuals of Hypostomus soniae (Loricariidae) collected from the Teles Pires River, southern Amazon basin, Brazil. Hypostomus soniae has a diploid chromosome number of 2n = 64 and a karyotype composed of 12 metacentric (m), 22 submetacentric (sm), 14 subtelocentric (st), and 16 acrocentric (a) chromosomes, with a structural difference between the chromosomes of the two sexes: the presence of a block of heterochromatin in sm pair No. 26, which appears to represent a putative initial stage of the differentiation of an XX/XY sex chromosome system. This chromosome, which had a heterochromatin block, and was designated proto-Y (pY), varied in the length of the long arm (q) in comparison with its homolog, resulting from the addition of constitutive heterochromatin. It is further distinguished by the presence of major ribosomal cistrons in a subterminal position of the long arm (q). The Nucleolus Organizer Region (NOR) had different phenotypes among the H. soniae individuals in terms of the number of Ag-NORs and 18S rDNA sites. The origin, distribution and maintenance of the chromosomal polymorphism found in H. soniae reinforced the hypothesis of the existence of a proto-Y chromosome, demonstrating the rise of an XX/XY sex chromosome system.

SEX CHROMOSOME DIFFERENTIATION: AN INTERMEDIATE STAGE IN A LIZARD

1978 ◽  
Vol 20 (2) ◽  
pp. 205-209 ◽  
Author(s):  
James Bull
Keyword(s):  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Early Stage ◽  
Intermediate Stage ◽  
Meiotic Cell ◽  
Chromosome Differentiation ◽  
Cell Divisions ◽  
Staining Techniques

Sex chromosomes of the lizard, Cnemidophorus tigris (Baird and Girard), were analyzed in mitotic and meiotic cell divisions using C-band and G-band staining techniques. The X and Y are homologous along most of their lengths but do not crossover in the medial portion of the bivalent, where their centromeres lie. In this region the X and Y differ in centric position and heterochromatin. The similarities of the X and Y in C. tigris contrast to sex chromosomes in other animals, and probably represent an early stage of differentiation.

scholarly journals Evolution of a Multiple Sex-Chromosome System by Three-Sequential Translocations among Potential Sex-Chromosomes in the Taiwanese Frog Odorrana swinhoana

Cells ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 661
Author(s):  
Ikuo Miura ◽  
Foyez Shams ◽  
Si-Min Lin ◽  
Marcelo de Bello Cioffi ◽  
Thomas Liehr ◽  
...  
Keyword(s):  
Sex Chromosomes ◽  
Rare Case ◽  
Sex Chromosome ◽  
Sex Chromosome System ◽  
Brown Frog ◽  
Male Specific

Translocation between sex-chromosomes and autosomes generates multiple sex-chromosome systems. It happens unexpectedly, and therefore, the evolutionary meaning is not clear. The current study shows a multiple sex chromosome system comprising three different chromosome pairs in a Taiwanese brown frog (Odorrana swinhoana). The male-specific three translocations created a system of six sex-chromosomes, ♂X1Y1X2Y2X3Y3 -♀X1X1X2X2X3X3. It is unique in that the translocations occurred among three out of the six members of potential sex-determining chromosomes, which are known to be involved in sex-chromosome turnover in frogs, and the two out of three include orthologs of the sex-determining genes in mammals, birds and fishes. This rare case suggests sex-specific, nonrandom translocations and thus provides a new viewpoint for the evolutionary meaning of the multiple sex chromosome system.

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