scholarly journals Evolution of a sex megachromosome

2020 ◽  
Author(s):  
Matthew A. Conte ◽  
Frances E. Clark ◽  
Reade B. Roberts ◽  
Luohao Xu ◽  
Wenjing Tao ◽  
...  
Keyword(s):  
Sex Determination ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Focal Point ◽  
Alternative Hypothesis ◽  
Cichlid Fish ◽  
B Chromosome ◽  
Sex Chromosome Evolution ◽  
Evolutionary Genomic ◽  
Size And Morphology

AbstractChromosome size and morphology vary within and among species, but little is known about either the proximate or ultimate causes of these differences. Cichlid fish species in the tribe Oreochromini share an unusual megachromosome that is ~3 times longer than any of the other chromosomes. This megachromosome functions as a sex chromosome in some of these species. We explore two hypotheses of how this sex megachromosome may have evolved. The first hypothesis proposes that it developed by the accumulation of repetitive elements as recombination was reduced around a dominant sex-determination locus, as suggested by traditional models of sex chromosome evolution. An alternative hypothesis is that the megachromosome originated via the fusion of an autosome with a highly-repetitive B chromosome, one of which had carried a sex-determination locus. Here we test these hypotheses using comparative analysis of several chromosome-scale cichlid and teleost genomes. We find the megachromosome consists of three distinct regions based on patterns of recombination, gene and transposable element content, and synteny to the ancestral autosome. A WZ sex-determination locus encompasses the last ~105Mbp of the 134Mbp megachromosome and the last 47Mbp of the megachromosome shares no obvious homology to any ancestral chromosome. Comparisons across 69 teleost genomes reveal the megachromosome contains unparalleled amounts of endogenous retroviral elements, immunoglobulin genes, and long non-coding RNAs. Although the origin of this megachromosome remains ambiguous, it has clearly been a focal point of extensive evolutionary genomic conflicts. This megachromosome represents an interesting system for studying sex chromosome evolution and genomic conflicts.

scholarly journals Origin of a Giant Sex Chromosome

2020 ◽  
Author(s):  
Matthew A Conte ◽  
Frances E Clark ◽  
Reade B Roberts ◽  
Luohao Xu ◽  
Wenjing Tao ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sex Chromosome ◽  
Alternative Hypothesis ◽  
Cichlid Fish ◽  
B Chromosome ◽  
Chromosome Fusion ◽  
Size And Morphology ◽  
Giant Chromosome ◽  
Fusion Hypothesis ◽  
Recombination Gene

Abstract Chromosome size and morphology vary within and among species, but little is known about the proximate or ultimate causes of these differences. Cichlid fish species in the tribe Oreochromini share an unusual giant chromosome that is ∼3 times longer than the other chromosomes. This giant chromosome functions as a sex chromosome in some of these species. We test two hypotheses of how this giant sex chromosome may have evolved. The first hypothesis proposes that it evolved by accumulating repetitive elements as recombination was reduced around a dominant sex determination locus, as suggested by canonical models of sex chromosome evolution. An alternative hypothesis is that the giant sex chromosome originated via the fusion of an autosome with a highly repetitive B chromosome, one of which carried a sex determination locus. We test these hypotheses using comparative analysis of chromosome-scale cichlid and teleost genomes. We find that the giant sex chromosome consists of three distinct regions based on patterns of recombination, gene and transposable element content, and synteny to the ancestral autosome. The WZ sex determination locus encompasses the last ∼105 Mb of the 134-Mb giant chromosome. The last 47 Mb of the giant chromosome shares no obvious homology to any ancestral chromosome. Comparisons across 69 teleost genomes reveal that the giant sex chromosome contains unparalleled amounts of endogenous retroviral elements, immunoglobulin genes, and long noncoding RNAs. The results favor the B chromosome fusion hypothesis for the origin of the giant chromosome.

scholarly journals Sex chromosome evolution: historical insights and future perspectives

2017 ◽  
Vol 284 (1854) ◽  
pp. 20162806 ◽  
Author(s):  
Jessica K. Abbott ◽  
Anna K. Nordén ◽  
Bengt Hansson
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Empirical Studies ◽  
Analytical Models ◽  
Specific Gene ◽  
Sex Chromosome Evolution ◽  
Current Thinking

Many separate-sexed organisms have sex chromosomes controlling sex determination. Sex chromosomes often have reduced recombination, specialized (frequently sex-specific) gene content, dosage compensation and heteromorphic size. Research on sex determination and sex chromosome evolution has increased over the past decade and is today a very active field. However, some areas within the field have not received as much attention as others. We therefore believe that a historic overview of key findings and empirical discoveries will put current thinking into context and help us better understand where to go next. Here, we present a timeline of important conceptual and analytical models, as well as empirical studies that have advanced the field and changed our understanding of the evolution of sex chromosomes. Finally, we highlight gaps in our knowledge so far and propose some specific areas within the field that we recommend a greater focus on in the future, including the role of ecology in sex chromosome evolution and new multilocus models of sex chromosome divergence.

scholarly journals The Genome ofArmadillidium vulgare(Crustacea, Isopoda) Provides Insights into Sex Chromosome Evolution in the Context of Cytoplasmic Sex Determination

2019 ◽  
Vol 36 (4) ◽  
pp. 727-741 ◽  
Author(s):  
Mohamed Amine Chebbi ◽  
Thomas Becking ◽  
Bouziane Moumen ◽  
Isabelle Giraud ◽  
Clément Gilbert ◽  
...  
Keyword(s):  
Sex Determination ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sex Chromosome Evolution

scholarly journals Lizards as Model Organisms of Sex Chromosome Evolution: What We Really Know from A Systematic Distribution of Available Data?

Genes ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1341
Author(s):  
Marcello Mezzasalma ◽  
Fabio M. Guarino ◽  
Gaetano Odierna
Keyword(s):  
Sex Determination ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sex Reversal ◽  
Model Organisms ◽  
Sex Chromosome Evolution ◽  
Temperature Dependent ◽  
Systematic Assessment ◽  
Qualitative And Quantitative ◽  
Unique Model

Lizards represent unique model organisms in the study of sex determination and sex chromosome evolution. Among tetrapods, they are characterized by an unparalleled diversity of sex determination systems, including temperature-dependent sex determination (TSD) and genetic sex determination (GSD) under either male or female heterogamety. Sex chromosome systems are also extremely variable in lizards. They include simple (XY and ZW) and multiple (X1X2Y and Z1Z2W) sex chromosome systems and encompass all the different hypothesized stages of diversification of heterogametic chromosomes, from homomorphic to heteromorphic and completely heterochromatic sex chromosomes. The co-occurrence of TSD, GSD and different sex chromosome systems also characterizes different lizard taxa, which represent ideal models to study the emergence and the evolutionary drivers of sex reversal and sex chromosome turnover. In this review, we present a synthesis of general genome and karyotype features of non-snakes squamates and discuss the main theories and evidences on the evolution and diversification of their different sex determination and sex chromosome systems. We here provide a systematic assessment of the available data on lizard sex chromosome systems and an overview of the main cytogenetic and molecular methods used for their identification, using a qualitative and quantitative approach.

Sex Determination Diversity and Sex Chromosome Evolution in Poeciliid Fish

2009 ◽  
Vol 3 (2-3) ◽  
pp. 68-77 ◽  
Author(s):  
C. Schultheis ◽  
A. Böhne ◽  
M. Schartl ◽  
J.N. Volff ◽  
D. Galiana-Arnoux
Keyword(s):  
Sex Determination ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sex Chromosome Evolution ◽  
Poeciliid Fish

scholarly journals Differences in Homomorphic Sex Chromosomes Are Associated with Population Divergence in Sex Determination in Carinascincus ocellatus (Scincidae: Lygosominae)

Cells ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 291
Author(s):  
Peta Hill ◽  
Foyez Shams ◽  
Christopher P. Burridge ◽  
Erik Wapstra ◽  
Tariq Ezaz
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Population Divergence ◽  
Sex Chromosome Evolution ◽  
Evolutionary Transitions ◽  
Evolutionary Origins ◽  
Probe Set

Sex determination directs development as male or female in sexually reproducing organisms. Evolutionary transitions in sex determination have occurred frequently, suggesting simple mechanisms behind the transitions, yet their detail remains elusive. Here we explore the links between mechanisms of transitions in sex determination and sex chromosome evolution at both recent and deeper temporal scales (<1 Myr; ~79 Myr). We studied a rare example of a species with intraspecific variation in sex determination, Carinascincus ocellatus, and a relative, Liopholis whitii, using c-banding and mapping of repeat motifs and a custom Y chromosome probe set to identify the sex chromosomes. We identified both unique and conserved regions of the Y chromosome among C. ocellatus populations differing in sex determination. There was no evidence for homology of sex chromosomes between C. ocellatus and L. whitii, suggesting independent evolutionary origins. We discuss sex chromosome homology between members of the subfamily Lygosominae and propose links between sex chromosome evolution, sex determination transitions, and karyotype evolution.

Sex Determination and Sex Chromosome Evolution: Insights from Medaka

2009 ◽  
Vol 3 (2-3) ◽  
pp. 88-98 ◽  
Author(s):  
M. Kondo ◽  
I. Nanda ◽  
M. Schmid ◽  
M. Schartl
Keyword(s):  
Sex Determination ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sex Chromosome Evolution

scholarly journals The X chromosome of the German cockroach, Blattella germanica, is homologous to a fly X chromosome despite 400 million years divergence

BMC Biology ◽  
2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Richard P. Meisel ◽  
Pablo J. Delclos ◽  
Judith R. Wexler
Keyword(s):  
Sex Determination ◽  
X Chromosome ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Blattella Germanica ◽  
German Cockroach ◽  
Whole Genome Sequence ◽  
Sex Chromosome Evolution ◽  
X Chromosomes

Abstract Background Sex chromosome evolution is a dynamic process that can proceed at varying rates across lineages. For example, different chromosomes can be sex-linked between closely related species, whereas other sex chromosomes have been conserved for > 100 million years. Cases of long-term sex chromosome conservation could be informative of factors that constrain sex chromosome evolution. Cytological similarities between the X chromosomes of the German cockroach (Blattella germanica) and most flies suggest that they may be homologous—possibly representing an extreme case of long-term conservation. Results To test the hypothesis that the cockroach and fly X chromosomes are homologous, we analyzed whole-genome sequence data from cockroaches. We found evidence in both sequencing coverage and heterozygosity that a significant excess of the same genes are on both the cockroach and fly X chromosomes. We also present evidence that the candidate X-linked cockroach genes may be dosage compensated in hemizygous males. Consistent with this hypothesis, three regulators of transcription and chromatin on the fly X chromosome are conserved in the cockroach genome. Conclusions Our results support our hypothesis that the German cockroach shares the same X chromosome as most flies. This may represent the convergent evolution of the X chromosome in the lineages leading to cockroaches and flies. Alternatively, the common ancestor of most insects may have had an X chromosome that resembled the extant cockroach and fly X. Cockroaches and flies diverged ∼ 400 million years ago, which would be the longest documented conservation of a sex chromosome. Cockroaches and flies have different mechanisms of sex determination, raising the possibility that the X chromosome was conserved despite the evolution of the sex determination pathway.

A cytogenetic analysis of the Simulium ochraceum species complex (Diptera: Simuliidae) in Central America

Genome ◽  
1994 ◽  
Vol 37 (1) ◽  
pp. 36-53 ◽  
Author(s):  
Hirohisa Hirai ◽  
William S. Procunier ◽  
J. Onofre Ochoa ◽  
K. Uemoto
Keyword(s):  
Sex Determination ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sympatric Speciation ◽  
Insect Vector ◽  
Sex Chromosome Evolution ◽  
Dispersal Capability ◽  
Chromosome Maps ◽  
Primary Vector ◽  
First Time

A cytobiotaxonomic study of the medically important insect vector Simulium ochraceum s.l. revealed two sibling species and one cytotype from various endemic and nonendemic zones of human onchocerciasis in Guatemala and Mexico. Polytene chromosome maps and idiograms as well as notes on the biology of the three taxa designated S. ochraceum A, S. ochraceum B, and S. ochraceum C within the subgenus Psilopelmia are presented. All three taxa exhibit distinct sex chromosomes and taxon-specific suites of autosomal inversion polymorphisms. Simulium ochraceum C differs from both S. ochraceum A and S. ochraceum B by five interspecific inversions designated IIS-7,8 and IIIL-12, 13 + 14, 15. The three taxa exhibit niche and biting preferences, with S. ochraceum A being highly anthropophilic. Analysis of autosomal inversion polymorphism profiles indicates S. ochraceum A has long-range dispersal capability. Our results are consistent with the general findings that in the Simuliidae, sibling speciation may be suspected wherever a morphospecies occupies different niches in a stream continuum. We find for the first time an apparent partitioning of taxa by altitude. Simulium ochraceum A may be a primary vector of human onchocerciasis in Guatemala, as its vertical distribution is coincident with that of the highest areas of nodule prevalence in the human population. A genotypic component of variation in vectorial capacity of S. ochraceum A populations seems to occur, since the Y4 chromosome and its X chromosome counterpart are associated with hyperendemic areas of human onchocerciasis. Our observation that a supernumerary band, 37B1Hb, is associated with sex determination in two of the taxa may be of significance for the elucidation of the molecular basis of sex determination and possible resolution of issues pertinent to the general model of sympatric speciation in the Simuliidae.Key words: Simulium ochraceum complex, cytobiotaxonomy, vector biology, sex chromosome evolution, human onchocerciasis.

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