scholarly journals Digest: Climate plays marginal role for homomorphic sex chromosome differentiation in common frogs†

Evolution ◽  
2020 ◽  
Vol 74 (3) ◽  
pp. 690-693
Author(s):  
Fanny E. Hartmann ◽  
Wen‐Juan Ma
Keyword(s):  
Sex Chromosome ◽  
Chromosome Differentiation

scholarly journals Telomere-to-telomere assembly of a fish Y chromosome reveals the origin of a young sex chromosome pair

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Lingzhan Xue ◽  
Yu Gao ◽  
Meiying Wu ◽  
Tian Tian ◽  
Haiping Fan ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Pair ◽  
Sex Chromosome ◽  
Structural Variations ◽  
Recombination Suppression ◽  
Chromosome Differentiation ◽  
Y Chromosomes ◽  
Recent Origin ◽  
Mastacembelus Armatus

Abstract Background The origin of sex chromosomes requires the establishment of recombination suppression between the proto-sex chromosomes. In many fish species, the sex chromosome pair is homomorphic with a recent origin, providing species for studying how and why recombination suppression evolved in the initial stages of sex chromosome differentiation, but this requires accurate sequence assembly of the X and Y (or Z and W) chromosomes, which may be difficult if they are recently diverged. Results Here we produce a haplotype-resolved genome assembly of zig-zag eel (Mastacembelus armatus), an aquaculture fish, at the chromosomal scale. The diploid assembly is nearly gap-free, and in most chromosomes, we resolve the centromeric and subtelomeric heterochromatic sequences. In particular, the Y chromosome, including its highly repetitive short arm, has zero gaps. Using resequencing data, we identify a ~7 Mb fully sex-linked region (SLR), spanning the sex chromosome centromere and almost entirely embedded in the pericentromeric heterochromatin. The SLRs on the X and Y chromosomes are almost identical in sequence and gene content, but both are repetitive and heterochromatic, consistent with zero or low recombination. We further identify an HMG-domain containing gene HMGN6 in the SLR as a candidate sex-determining gene that is expressed at the onset of testis development. Conclusions Our study supports the idea that preexisting regions of low recombination, such as pericentromeric regions, can give rise to SLR in the absence of structural variations between the proto-sex chromosomes.

scholarly journals Sex chromosome differentiation in Belostoma (Insecta: Heteroptera: Belostomatidae)

2012 ◽  
Vol 11 (3) ◽  
pp. 2476-2486 ◽  
Author(s):  
V.B. Bardella ◽  
A.L. Dias ◽  
L. Giuliano-Caetano ◽  
J.R.I. Ribeiro ◽  
R. da Rosa
Keyword(s):  
Sex Chromosome ◽  
Chromosome Differentiation

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

2019 ◽  
Vol 116 (38) ◽  
pp. 19031-19036 ◽  
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 ◽  
Y Chromosomes ◽  
Shared Ancestry ◽  
Suppressed Recombination

Once recombination is halted between the X and Y chromosomes, 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 the variation in sex chromosome differentiation within clades. Here, we combined whole-genome and transcriptome sequencing data to characterize 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 roughly 20 million years ago. 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 and P. wingei are largely homomorphic, with recombination in the former persisting over a substantial fraction. However, the sex chromosomes in P. picta are completely nonrecombining and strikingly heteromorphic. Remarkably, the profound degradation of the ancestral Y chromosome in P. picta is counterbalanced by the evolution of functional chromosome-wide dosage compensation in this species, which has not been previously observed in teleost fish. Our results offer important insight into the initial stages of sex chromosome evolution and dosage compensation.

scholarly journals Early stages of sex chromosome differentiation in fish as analysed by simple repetitive DNA sequences

Chromosoma ◽  
1992 ◽  
Vol 101 (5-6) ◽  
pp. 301-310 ◽  
Author(s):  
Indrajit Nanda ◽  
Manfred Schartl ◽  
Wolfgang Feichtinger ◽  
J�rg T. Epplen ◽  
Michael Schmid
Keyword(s):  
Repetitive Dna ◽  
Dna Sequences ◽  
Sex Chromosome ◽  
Repetitive Dna Sequences ◽  
Chromosome Differentiation ◽  
Early Stages

Karyotype, sex chromatin and sex chromosome differentiation in the carob moth,Ectomyelois ceratoniae(Lepidoptera: Pyralidae)

Caryologia ◽  
2004 ◽  
Vol 57 (2) ◽  
pp. 184-194 ◽  
Author(s):  
Jouda Mediouni ◽  
Iva Fuková ◽  
Radmila Frydrychová ◽  
Mohamed Habib Dhouibi ◽  
František Marec
Keyword(s):  
Sex Chromosome ◽  
Ectomyelois Ceratoniae ◽  
Chromosome Differentiation ◽  
Sex Chromatin ◽  
Lepidoptera Pyralidae ◽  
Carob Moth

Sibling species and sex chromosome differentiation in Simulium neornatipes (Diptera: Simuliidae)

1984 ◽  
Vol 26 (3) ◽  
pp. 318-325 ◽  
Author(s):  
D. G. Bedo
Keyword(s):  
Polytene Chromosome ◽  
Sibling Species ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Close Association ◽  
Chromosome Analysis ◽  
Sex Linkage ◽  
Direct Role ◽  
Chromosome Differentiation ◽  
Close Relationship

Polytene chromosome analysis of five Simulium neornatipes populations not only confirms the existence of the two sibling species, S. neornatipes 1 and 2, proposed earlier but reveals a third. S. neornatipes 3. These sibling species share a common standard polytene chromosome banding sequence which differs from the Australian S. ornatipes complex standard by five fixed inversions. The sharing of polymorphic inversions between the ornatipes and neornatipes complexes indicates their close relationship. The neornatipes species are distinguished from each other by additional fixed inversions and differentiated sex chromosomes. Extensive sex chromosome differentiation involving chromosome III has occurred in S. neornatipes 1 and 2. A period of incomplete sex-linkage allowing reassortment of inversions must have preceded the currently observed strong sex-linkage of differentiated sex chromosomes to account for the complex array of sex chromosomes found. The close association of sex chromosome differentiation with speciation in black flies is discussed in relation to appropriate speciation mechanisms. It is concluded that the rearrangements themselves have no direct role in the speciation process.Key words: sibling species, sex chromosomes, Simuliidae.

The degenerate Y chromosome – can conversion save it?

2004 ◽  
Vol 16 (5) ◽  
pp. 527 ◽  
Author(s):  
Jennifer A. Marshall Graves
Keyword(s):  
Gene Conversion ◽  
Y Chromosome ◽  
Genetic Drift ◽  
Sex Chromosome ◽  
Chromosome Differentiation ◽  
Y Chromosomes ◽  
Speed Up ◽  
Selection For ◽  
Human Y Chromosome

The human Y chromosome is running out of time. In the last 300 million years, it has lost 1393 of its original 1438 genes, and at this rate it will lose the last 45 in a mere 10 million years. But there has been a proposal that perhaps rescue is at hand in the form of recently discovered gene conversion within palindromes. However, I argue here that although conversion will increase the frequency of variation of the Y (particularly amplification) between Y chromosomes in a population, it will not lead to a drive towards a more functional Y. The forces of evolution have made the Y a genetically isolated, non-recombining entity, vulnerable to genetic drift and selection for favourable new variants sharing the Y with damaging mutations. Perhaps it will even speed up the decline of the Y chromosome and the onset of a new round of sex-chromosome differentiation. The struggle to preserve males may perhaps lead to hominid speciation.

scholarly journals Using conventionalF-statistics to study unconventional sex-chromosome differentiation

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3207 ◽  
Author(s):  
Nicolas Rodrigues ◽  
Christophe Dufresnes
Keyword(s):  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Rana Temporaria ◽  
Microsatellite Data ◽  
Homologous Chromosomes ◽  
Chromosome Differentiation ◽  
Population Analyses ◽  
Hyla Arborea ◽  
Frog Species ◽  
Heterogametic Sex

Species with undifferentiated sex chromosomes emerge as key organisms to understand the astonishing diversity of sex-determination systems. Whereas new genomic methods are widening opportunities to study these systems, the difficulty to separately characterize their X and Y homologous chromosomes poses limitations. Here we demonstrate that two simpleF-statistics calculated from sex-linked genotypes, namely the genetic distance (Fst) between sexes and the inbreeding coefficient (Fis) in the heterogametic sex, can be used as reliable proxies to compare sex-chromosome differentiation between populations. We correlated these metrics using published microsatellite data from two frog species (Hyla arboreaandRana temporaria), and show that they intimately relate to the overall amount of X–Y differentiation in populations. However, the fits for individual loci appear highly variable, suggesting that a dense genetic coverage will be needed for inferring fine-scale patterns of differentiation along sex-chromosomes. The applications of theseF-statistics, which implies little sampling requirement, significantly facilitate population analyses of sex-chromosomes.

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