scholarly journals The Guppy Sex Chromosome System and the Sexually Antagonistic Polymorphism Hypothesis for Y Chromosome Recombination Suppression

Genes ◽  
2018 ◽  
Vol 9 (5) ◽  
pp. 264 ◽  
Author(s):  
Deborah Charlesworth
Keyword(s):  
Y Chromosome ◽  
Sex Chromosome ◽  
Recombination Suppression ◽  
Chromosome Recombination ◽  
Sex Chromosome System

scholarly journals Guppy Y Chromosome Integrity Maintained by Incomplete Recombination Suppression

2020 ◽  
Vol 12 (6) ◽  
pp. 965-977 ◽  
Author(s):  
Iulia Darolti ◽  
Alison E Wright ◽  
Judith E Mank
Keyword(s):  
Y Chromosome ◽  
X Chromosome ◽  
Sex Chromosomes ◽  
Poecilia Reticulata ◽  
Sex Chromosome ◽  
Rna Seq ◽  
Recombination Suppression ◽  
Sex Chromosome System ◽  
Chromosome Integrity ◽  
Heterogametic Sex

Abstract The loss of recombination triggers divergence between the sex chromosomes and promotes degeneration of the sex-limited chromosome. Several livebearers within the genus Poecilia share a male-heterogametic sex chromosome system that is roughly 20 Myr old, with extreme variation in the degree of Y chromosome divergence. In Poecilia picta, the Y is highly degenerate and associated with complete X chromosome dosage compensation. In contrast, although recombination is restricted across almost the entire length of the sex chromosomes in Poecilia reticulata and Poecilia wingei, divergence between the X chromosome and the Y chromosome is very low. This clade therefore offers a unique opportunity to study the forces that accelerate or hinder sex chromosome divergence. We used RNA-seq data from multiple families of both P. reticulata and P. wingei, the species with low levels of sex chromosome divergence, to differentiate X and Y coding sequences based on sex-limited SNP inheritance. Phylogenetic tree analyses reveal that occasional recombination has persisted between the sex chromosomes for much of their length, as X- and Y-linked sequences cluster by species instead of by gametolog. This incomplete recombination suppression maintains the extensive homomorphy observed in these systems. In addition, we see differences between the previously identified strata in the phylogenetic clustering of X–Y orthologs, with those that cluster by chromosome located in the older stratum, the region previously associated with the sex-determining locus. However, recombination arrest appears to have expanded throughout the sex chromosomes more gradually instead of through a stepwise process associated with inversions.

scholarly journals Evidence of Recombination Suppression Blocks on the Y Chromosome of Date Palm (Phoenix dactylifera)

2021 ◽  
Vol 12 ◽  
Author(s):  
Maria F. Torres ◽  
Yasmin A. Mohamoud ◽  
Shameem Younuskunju ◽  
Karsten Suhre ◽  
Joel A. Malek
Keyword(s):  
Y Chromosome ◽  
Date Palm ◽  
Sex Chromosome ◽  
Sugar Content ◽  
Phoenix Dactylifera ◽  
Palm Tree ◽  
Recombination Suppression ◽  
Sex Chromosome System ◽  
Male Specific ◽  
Specific Sequences

The genus Phoenix includes the fruit producing date palm tree among 14 species that are all dioecious. Females produce the fruit that are high in sugar content and used in multiple countries ranging from North Africa to South Asia, especially from the Phoenix dactylifera, Phoenix sylvestris, and Phoenix canariensis species. While females produce the fruit, understanding of the genetic basis of sex control only began recently. Through genus-wide sequencing of males and females we recently identified three genes that are conserved in all males and absent in all females of the genus and confirmed an XY sex chromosome system. While our previous study focused on conservation of male-specific sequences at the genus-level, it would be of interest to better understand the spread of male-specific sequences away from the core conserved male genes on the Y chromosome during speciation. To this end, we enumerated male-specific 16 bp sequences using three male/female pairs from the western subpopulation of date palm and documented the density of these sequences in contigs of a phased date palm genome assembly. Here we show that male specific sequences in the date palm Y chromosome have likely spread in defined events that appear as blocks of varying density with significant changes in density between them. Collinearity of genes in these blocks with oil palm shows high synteny with chromosome 10 between megabase 15 and 23 and reveals that large sections of the date palm Y chromosome have maintained the ancestral structure even as recombination has stopped between X and Y.

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.

From brain determination to testis determination: evolution of the mammalian sex-determining gene

2001 ◽  
Vol 13 (8) ◽  
pp. 665 ◽  
Author(s):  
Jennifer A. Marshall Graves
Keyword(s):  
Y Chromosome ◽  
Sex Chromosome ◽  
Critical Role ◽  
Dominant Gene ◽  
Comparative Gene Mapping ◽  
Good Account ◽  
Mole Vole ◽  
Sex Chromosome System ◽  
Testis Determination ◽  
Autosome Pair

In mammals, sex is determined by an XY male:XX female sex chromosome system in which a male-dominant gene on the Y chromosome (SRY) determines testis formation. Sex chromosomes evolved from an ordinary autosome pair as the Y chromosome was progressively degraded. The Y chromosome has lost nearly all of its 1500 original genes, and those that survived did so because they evolved a critical role in male determination or differentiation. SRY is typical of Y-borne genes. Comparative gene mapping and sequencing shows that SRY arose quite recently as a degraded version of the SOX3 gene on the X chromosome. SOX3 is expressed predominantly in brain, and so is more likely to be a brain-determining than a testis-determining gene. The male-dominant action of SRY may be an illusion, as its structure suggests that it works by interfering with the action of a related gene, which in turn inhibits testis development. This hypothesis can give a good account of how a brain-determining gene acquired a role in testis determination via differential dosage of SOX3. SRY has no central role in sex determination and it can be replaced as a trigger and lost, as have many other Y-borne genes in recent evolutionary history. The absence of SRY in two species of the mole vole (Ellobius) suggests that its useful life is already running out.

scholarly journals 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 ◽  
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.

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.

Differentiation of Y Chromosome in the X1X1X2X2/X1X2Y Sex Chromosome System of Hoplias malabaricus (Characiformes, Erythrinidae)

2009 ◽  
Vol 127 (1) ◽  
pp. 54-60 ◽  
Author(s):  
R. da Rosa ◽  
A.L. Laforga Vanzela ◽  
M. Rubert ◽  
I.C. Martins-Santos ◽  
L. Giuliano-Caetano
Keyword(s):  
Y Chromosome ◽  
Sex Chromosome ◽  
Hoplias Malabaricus ◽  
Sex Chromosome System

scholarly journals A Selective Sweep Associated With a Recent Gene Transposition in Drosophila miranda

Genetics ◽  
2000 ◽  
Vol 156 (4) ◽  
pp. 1753-1763 ◽  
Author(s):  
Soojin Yi ◽  
Brian Charlesworth
Keyword(s):  
Y Chromosome ◽  
X Chromosome ◽  
Sequence Variation ◽  
Selective Sweep ◽  
Sex Chromosome ◽  
Selective Advantage ◽  
Chromosome Fusion ◽  
Gene Transposition ◽  
Sex Chromosome System ◽  
Male Specific

Abstract In Drosophila miranda, a chromosome fusion between the Y chromosome and the autosome corresponding to Muller’s element C has created a new sex chromosome system. The chromosome attached to the ancestral Y chromosome is transmitted paternally and hence is not exposed to crossing over. This chromosome, conventionally called the neo-Y, and the homologous neo-X chromosome display many properties of evolving sex chromosomes. We report here the transposition of the exuperantia1 (exu1) locus from a neo-sex chromosome to the ancestral X chromosome of D. miranda. Exu1 is known to have several critical developmental functions, including a male-specific role in spermatogenesis. The ancestral location of exu1 is conserved in the sibling species of D. miranda, as well as in a more distantly related species. The transposition of exu1 can be interpreted as an adaptive fixation, driven by a selective advantage conferred by its effect on dosage compensation. This explanation is supported by the pattern of within-species sequence variation at exu1 and the nearby exu2 locus. The implications of this phenomenon for genome evolution are discussed.

scholarly journals Plant genera Cannabis and Humulus share the same pair of well-differentiated sex chromosomes

2021 ◽  
Author(s):  
D Prentout ◽  
N Stajner ◽  
A Cerenak ◽  
T Tricou ◽  
C Brochier-Armanet ◽  
...  
Keyword(s):  
Sex Chromosomes ◽  
Cannabis Sativa ◽  
Sex Chromosome ◽  
Probabilistic Method ◽  
List Type ◽  
Recombination Suppression ◽  
Sex Chromosome System ◽  
The Common ◽  
Well Differentiated ◽  
First Time

SummaryWe recently described, in Cannabis sativa, the oldest sex chromosome system documented so far in plants. Based on our estimate of its age, we predicted that it should be shared by its sister genus Humulus, which is known to also possess XY sex chromosomes.Here, we used transcriptome sequencing of a F1 family of Humulus lupulus to identify and study the sex chromosomes in this species using the probabilistic method SEX-DETector.We identified 265 sex-linked genes in H. lupulus, located on the chromosome that is also the C. sativa sex chromosome pair. Using phylogenies of sex-linked genes, we show that a region of these chromosomes had already stopped recombining in the common ancestor of the two species. Furthermore, as in C. sativa, Y gene expression was reduced in correlation to the position on the X chromosome, and strongly Y degenerated genes showed dosage compensation.Here we report, for the first time in the Angiosperms, a sex chromosome system that is shared by two different genera. Recombination suppression started at least 21-25 My ago, and then (either gradually or step-wise) spread to a large part of the sex chromosomes, leading to a strongly degenerated Y.

The polytene chromosomes of Simulium furculatum (Shewell) (Diptera: Simuliidae)

Genome ◽  
1989 ◽  
Vol 32 (4) ◽  
pp. 522-530
Author(s):  
Fiona F. Hunter
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Polytene Chromosomes ◽  
Species Group ◽  
Western Canada ◽  
Black Flies ◽  
X Chromosomes ◽  
Group A ◽  
Sex Chromosome System

To test whether Simulium furculatum (Shewell) belongs to the Simulium vernum (Macquart) species-group, a comparison was made of the polytene chromosomes of S. furculatum and the S. vernum "Knebworth" standard. Only two chromosome arms (of six) could be completely analysed. It is argued that S. furculatum does not belong to the S. vernum species-group. A complex sex-chromosome system (X1, X2, Y1) is found in both eastern and western Canada. Phylogenetically, the single Y chromosome is intermediate between the two X chromosomes. Intraspecific inversion polymorphisms, which serve to differentiate eastern from western populations, are also identified. Only one sibling is indicated.Key words: black flies, Simulium furculatum, Simulium vernum, cytotaxonomy, polytene chromosomes, sex chromosomes.

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