scholarly journals The female (XX) and male (YY) genomes provide insights into the sex determination mechanism in spinach

2020 ◽  
Author(s):  
Hongbing She ◽  
Zhiyuan Liu ◽  
Zhaosheng Xu ◽  
Helong Zhang ◽  
Feng Cheng ◽  
...  
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Large Scale ◽  
Recombination Suppression ◽  
Autosomal Region ◽  
Male Genome ◽  
Y Chromosomes ◽  
Primary Means ◽  
Almost All

AbstractSexual reproduction is the primary means of reproduction for the vast majority of macroscopic organisms, including almost all animals and plants. Sex chromosomes are predicted to play a central role in sexual dimorphism. Sex determination in spinach is controlled by a pair of sex chromosomes. However, the mechanisms of sex determination in spinach remain poorly understand. Here, we assembled the genomes of both a female (XX) and a male (YY) individual of spinach, and the genome sizes were 978 Mb with 28,320 predicted genes and 926 Mb with 26,537 predicted genes, respectively. Based on reported sex-linked markers, chromosomes 4 of the female and male genome were defined as the X and Y chromosomes, and a 10 Mb male-specific region of the Y chromosome (MSY) from approximately 95– 105 Mb, was identified that contains abundant transposable elements (92.32%). Importantly, a large-scale inversion of about 13 Mb in length was detected on the X chromosome, corresponding to ~9 Mb and ~4 Mb on the Y chromosome, which were located on both sides of the MSY with two distinct evolutionary strata. Almost all sex-linked/Y-specific markers were enriched on the inversions/MSY, suggesting that the flanked inversions might result in recombination suppression between the X and Y chromosomes to maintain the MSY. Forty-nine genes within the MSY had functional homologs elsewhere in the autosomal region, suggesting movement of genes onto the MSY. The X and Y chromosomes of spinach provide a valuable resource for investigating spinach sex chromosomes evolution from wild to cultivated spinach and also provide a broader understanding of the sex determination model in the Amaranthaceae family.

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 Impact of deleterious mutations, sexually antagonistic selection and mode of recombination suppression on transitions between male and female heterogamety

2018 ◽  
Author(s):  
Paul A. Saunders ◽  
Samuel Neuenschwander ◽  
Nicolas Perrin
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Deleterious Mutations ◽  
Mutation Load ◽  
Recombination Suppression ◽  
Male And Female ◽  
Antagonistic Selection ◽  
Y Chromosomes ◽  
Chromosome Mutation ◽  
Sexually Antagonistic Selection

AbstractDeleterious mutations accumulating on non-recombining Y chromosomes can drive XY to XY turnovers, but are thought to prevent XY to ZW turnovers, because the latter require fixation of the ancestral Y. Using individual-based simulations, we explored whether and how a dominant W allele can spread in a young XY system that gradually accumulates deleterious mutations. We also investigated how sexually antagonistic (SA) polymorphism on the ancestral sex chromosomes, and the mechanism controlling X-Y recombination suppression affect these transitions. In contrast with XY to XY turnovers, XY to ZW turnovers cannot be favored by Y chromosome mutation load. If the arrest of X-Y recombination depends on genotypic sex, transitions are strongly hindered by deleterious mutations, and totally suppressed by very small SA cost, because deleterious mutations and female-detrimental SA alleles would have to fix with the Y. If, however, the arrest of X-Y recombination depends on phenotypic sex, X and Y recombine in XY ZW females, allowing for the purge of Y-linked deleterious mutations and loss of the SA polymorphism, causing XY to ZW turnovers to occur at a neutral rate. We generalize our results to other types of turnovers (e.g., triggered by non-dominant sex-determining mutations) and discuss their empirical relevance.

scholarly journals Cytogenetic Analysis of the Asian Box Turtles of the Genus Cuora (Testudines, Geoemydidae)

Genes ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 156
Author(s):  
Lorenzo Clemente ◽  
Sofia Mazzoleni ◽  
Eleonora Pensabene ◽  
Tomáš Protiva ◽  
Philipp Wagner ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Wide Distribution ◽  
Iucn Red List ◽  
Telomeric Repeats ◽  
Rdna Loci ◽  
Box Turtles ◽  
Genotypic Sex Determination ◽  
Poorly Differentiated ◽  
Almost All

The Asian box turtle genus Cuora currently comprises 13 species with a wide distribution in Southeast Asia, including China and the islands of Indonesia and Philippines. The populations of these species are rapidly declining due to human pressure, including pollution, habitat loss, and harvesting for food consumption. Notably, the IUCN Red List identifies almost all species of the genus Cuora as Endangered (EN) or Critically Endangered (CR). In this study, we explore the karyotypes of 10 Cuora species with conventional (Giemsa staining, C-banding, karyogram reconstruction) and molecular cytogenetic methods (in situ hybridization with probes for rDNA loci and telomeric repeats). Our study reveals a diploid chromosome number of 2n = 52 chromosomes in all studied species, with karyotypes of similar chromosomal morphology. In all examined species, rDNA loci are detected at a single medium-sized chromosome pair and the telomeric repeats are restricted to the expected terminal position across all chromosomes. In contrast to a previous report, sex chromosomes are neither detected in Cuoragalbinifrons nor in any other species. Therefore, we assume that these turtles have either environmental sex determination or genotypic sex determination with poorly differentiated sex chromosomes. The conservation of genome organization could explain the numerous observed cases of interspecific hybridization both within the genus Cuora and across geoemydid turtles.

scholarly journals The maintenance of polygenic sex determination depends on the dominance of fitness effects which are predictive of the role of sexual antagonism

2021 ◽  
Author(s):  
Richard P Meisel
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
House Fly ◽  
Sexual Antagonism ◽  
Antagonistic Effects ◽  
Fitness Effects ◽  
Y Chromosomes ◽  
Sexually Antagonistic Selection ◽  
The Individual ◽  
Polygenic Sex Determination

Abstract In species with polygenic sex determination, multiple male- and female-determining loci on different proto-sex chromosomes segregate as polymorphisms within populations. The extent to which these polymorphisms are at stable equilibria is not yet resolved. Previous work demonstrated that polygenic sex determination is most likely to be maintained as a stable polymorphism when the proto-sex chromosomes have opposite (sexually antagonistic) fitness effects in males and females. However, these models usually consider polygenic sex determination systems with only two proto-sex chromosomes, or they do not broadly consider the dominance of the alleles under selection. To address these shortcomings, I used forward population genetic simulations to identify selection pressures that can maintain polygenic sex determination under different dominance scenarios in a system with more than two proto-sex chromosomes (modeled after the house fly). I found that overdominant fitness effects of male-determining proto-Y chromosomes are more likely to maintain polygenic sex determination than dominant, recessive, or additive fitness effects. The overdominant fitness effects that maintain polygenic sex determination tend to have proto-Y chromosomes with sexually antagonistic effects (male-beneficial and female-detrimental). In contrast, dominant fitness effects that maintain polygenic sex determination tend to have sexually antagonistic multi-chromosomal genotypes, but the individual proto-sex chromosomes do not have sexually antagonistic effects. These results demonstrate that sexual antagonism can be an emergent property of the multi-chromosome genotype without individual sexually antagonistic chromosomes. My results further illustrate how the dominance of fitness effects has consequences for both the likelihood that polygenic sex determination will be maintained as well as the role sexually antagonistic selection is expected to play in maintaining the polymorphism.

Polymorphism and differentiation of rainbow trout Y chromosomes

Genome ◽  
2004 ◽  
Vol 47 (6) ◽  
pp. 1105-1113 ◽  
Author(s):  
Alicia Felip ◽  
Atushi Fujiwara ◽  
William P Young ◽  
Paul A Wheeler ◽  
Marc Noakes ◽  
...  
Keyword(s):  
Rainbow Trout ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Morphological Differentiation ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Y Chromosomes ◽  
Cytogenetic Analyses ◽  
Clonal Lines ◽  
Sex Locus

Most fish species show little morphological differentiation in the sex chromosomes. We have coupled molecular and cytogenetic analyses to characterize the male-determining region of the rainbow trout (Oncorhynchus mykiss) Y chromosome. Four genetically diverse male clonal lines of this species were used for genetic and physical mapping of regions in the vicinity of the sex locus. Five markers were genetically mapped to the Y chromosome in these male lines, indicating that the sex locus was located on the same linkage group in each of the lines. We also confirmed the presence of a Y chromosome morphological polymorphism among these lines, with the Y chromosomes from two of the lines having the more common heteromorphic Y chromosome and two of the lines having Y chromosomes morphologically similar to the X chromosome. The fluorescence in situ hybridization (FISH) pattern of two probes linked to sex suggested that the sex locus is physically located on the long arm of the Y chromosome. Fishes appear to be an excellent group of organisms for studying sex chromosome evolution and differentiation in vertebrates because they show considerable variability in the mechanisms and (or) patterns involved in sex determination.Key words: sex chromosomes, sex markers, cytogenetics, rainbow trout, fish.

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 Rapid Y degeneration and dosage compensation in plant sex chromosomes

2015 ◽  
Vol 112 (42) ◽  
pp. 13021-13026 ◽  
Author(s):  
Alexander S. T. Papadopulos ◽  
Michael Chester ◽  
Kate Ridout ◽  
Dmitry A. Filatov
Keyword(s):  
Sex Chromosomes ◽  
Large Scale ◽  
De Novo ◽  
Silene Latifolia ◽  
Stop Codons ◽  
Y Chromosomes ◽  
Evolutionary Trajectories ◽  
Plant Sex Chromosomes ◽  
Two Kingdoms ◽  
Y Degeneration

The nonrecombining regions of animal Y chromosomes are known to undergo genetic degeneration, but previous work has failed to reveal large-scale gene degeneration on plant Y chromosomes. Here, we uncover rapid and extensive degeneration of Y-linked genes in a plant species, Silene latifolia, that evolved sex chromosomes de novo in the last 10 million years. Previous transcriptome-based studies of this species missed unexpressed, degenerate Y-linked genes. To identify sex-linked genes, regardless of their expression, we sequenced male and female genomes of S. latifolia and integrated the genomic contigs with a high-density genetic map. This revealed that 45% of Y-linked genes are not expressed, and 23% are interrupted by premature stop codons. This contrasts with X-linked genes, in which only 1.3% of genes contained stop codons and 4.3% of genes were not expressed in males. Loss of functional Y-linked genes is partly compensated for by gene-specific up-regulation of X-linked genes. Our results demonstrate that the rate of genetic degeneration of Y-linked genes in S. latifolia is as fast as in animals, and that the evolutionary trajectories of sex chromosomes are similar in the two kingdoms.

CYTOTAXONOMY AND SEX DETERMINATION OF RUMEX PAUCIFOLIUS

1956 ◽  
Vol 34 (2) ◽  
pp. 261-268 ◽  
Author(s):  
Áskell Löve ◽  
Nina Sarkar
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
The Other ◽  
Large Chromosome ◽  
Dioecious Species ◽  
The Third ◽  
Male Sex ◽  
Morphological Differences

The western North American dioecious species Rumex paucifolius is shown to be a tetraploid with 2n = 28 chromosomes. It is the third tetraploid known within the subgenus Acetosa, and the first polyploid dioecious taxon of that group, the others having either 2n = 14 ♂, 15 ♀ (R. Acetosa and relatives), or 2n = 8 ♂, 9 ♀ (R. hastatulus). The sex chromosomes of R. paucifolius are of the XX:XY type, the male sex being heterogametic. The X is a large chromosome, while the Y is the smallest chromosome of the complement. The mechanism of sex determination of R. paucifolius follows the Melandrium–Acetosella scheme with strongly epistatic male determinants in the Y–chromosome. Other dioecious Acetosae follow the Drosophila–Acetosa scheme of sex determination with a balance between the number of X and autosome complements, the Y being sexually inert. It is concluded from the observed cytogenetical and morphological differences that R. paucifolius should constitute a section of its own, Paucifoliae, which should be placed as far as possible from the section Acetosa, though within the same subgenus. The other American dioecious endemic, R. hastatulus, is placed in a subsection of the section Acetosa.

Y chromosome specific markers and the evolution of dioecy in the genus Silene

Genome ◽  
1998 ◽  
Vol 41 (2) ◽  
pp. 141-147 ◽  
Author(s):  
Y Hi Zhang ◽  
Veronica S Stilio ◽  
Farah Rehman ◽  
Amy Avery ◽  
David Mulcahy ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Silene Latifolia ◽  
Dioecious Species ◽  
Sequence Characterized Amplified Region ◽  
Y Chromosomes ◽  
Heteromorphic Sex Chromosomes ◽  
Males And Females ◽  
Genus Silene ◽  
Evolution Of Dioecy

Sex determination in plants has been most thoroughly investigated in Silene latifolia, a dioecious species possessing heteromorphic sex chromosomes. We have identified several new Y chromosome linked RAPD markers and converted these to more reliable sequence characterized amplified region (SCAR) markers by cloning the RAPD fragments and developing longer primers. Of the primer pairs for seven SCARs, five amplify a single, unique fragment from the DNA of male S. latifolia. Two sets of primers also amplify additional fragments common to males and females. Homology between the X and Y chromosomes is sufficient to allow the amplification of fragments from females under less stringent PCR conditions. Five of the SCARs also distinguish between the sexes of closely related dioecious taxa of the section Elisanthe, but not between the sexes of distantly related dioecious species. These markers will be useful for continued investigations into the evolution of sex, phylogenetic relationships among taxa, and population dynamics of sex ratios in the genus Silene.Key words: Melandrium, RAPDs, sex chromosomes, SCARs.

Assays of testis development in the mouse distinguish three classes of domesticus-type Y chromosome

Genome ◽  
1988 ◽  
Vol 30 (6) ◽  
pp. 870-878 ◽  
Author(s):  
Fred G. Biddle ◽  
Yutaka Nishioka
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
House Mouse ◽  
Mus Musculus ◽  
Autosomal Recessive ◽  
Recessive Gene ◽  
Laboratory Strain ◽  
Sex Reversal ◽  
Differential Interaction ◽  
Y Chromosomes

The Y chromosome of Mus musculus poschiavinus interacts with the autosomal recessive gene tda-1b of the C57BL/6J laboratory strain of the house mouse to cause complete or partial sex reversal. Ovaries or ovotestes develop in a substantial proportion of the XY fetuses. Several different Y-specific DNA probes distinguish two major types of Y chromosome in the house mouse and they are represented by M. m. domesticus and M. m. musculus. The poschiavinus Y chromosome appears identical to the domesticus Y. The developmental distribution of the gonad types was examined in the first backcross or N2 generation of fetuses in C57BL/6J with six different domesticus-type Y chromosomes and, as controls, three different musculus-type Y chromosomes. Gonadal hermaphrodites were found with three of the six domesticus-type Y chromosomes. Both overall frequency and phenotypic distribution of types of gonadal hermaphrodites identify three classes of domesticus-type Y chromosome by their differential interaction with the C57BL/6J genetic background.Key words: mouse, Y chromosomes, gonadal hermaphrodites, primary sex determination.

Sign in / Sign up

Export Citation Format

Share Document