Sex chromosome evolution: hallmarks and question marks

Molecular Biology and Evolution, Journal Year: 2024, Volume and Issue: 41(11)

Published: Oct. 16, 2024

Abstract Sex chromosomes are widespread in species with separate sexes. They have evolved many times independently and display a truly remarkable diversity. New sequencing technologies methodological developments allowed the field of molecular evolution to explore this diversity large number model nonmodel organisms, broadening our vision on mechanisms involved their evolution. Diverse studies us better capture common evolutionary routes that shape sex chromosomes; however, we still mostly fail explain why so diverse. We review over half century theoretical empirical work chromosome highlight pending questions origins, turnovers, rearrangements, degeneration, dosage compensation, gene content, rates also report recent progress understanding ultimate reasons for chromosomes’ existence.

Language: Английский

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Genetic differentiation in the MAT-proximal region is not sufficient for suppressing recombination in Podospora anserina

G3 Genes Genomes Genetics, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 24, 2025

Recombination is advantageous over the long-term, as it allows efficient selection and purging deleterious mutations. Nevertheless, recombination suppression has repeatedly evolved in sex mating-type chromosomes. The evolutionary causes for proximal mechanisms preventing crossing overs are poorly understood. Several hypotheses have recently been suggested based on theoretical models, particular that divergence could accumulate neutrally around a sex-determining region reduce rates, self-reinforcing process foster progressive extension of suppression. We used ascomycete fungus Podospora anserina investigating these questions: 0.8 Mbp its locus non-recombining, despite being collinear between two mating types. This mostly selfing, resulting highly homozygous individuals, except non-recombining displays differentiation Here, we test hypothesis sequence alone responsible cessation. replaced mat- idiomorph by mat+ idiomorph, to obtain strain sexually compatible with reference isogenic this MAT-proximal region. Crosses showed was still suppressed mutant strains, indicating other than inversions or mere fungus. finding suggests selective likely acted suppressing recombination, spread epigenetic marks, neutral model nucleotide does not seem hold P. anserina.

Language: Английский

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Dynamic evolution of a sex-linked region

Research Square (Research Square), Journal Year: 2025, Volume and Issue: unknown

Published: Feb. 10, 2025

Background Sex chromosomes often evolve exceptionally fast and degenerate after recombination arrest. However, the underlying evolutionary processes are under persistent debate, particularly whether or not arrest evolves in a stepwise manner how switches sex determination genes contribute to chromosome evolution. Here, we study dioecious plant genus Salix with high turnover of chromosomes. Results We identified Z W sex-linked regions (~ 8 Mb) on 15 dwarf willow Salix herbacea using new haplotype-resolved assembly. The region harboured large (5 embedded inversion. Analyses synteny other species, sequence divergence between degeneration suggest that inversion recently incorporated pseudoautosomal sequences into region, extending its length nearly three-fold. W-hemizygous exclusively contained seven pairs inverted partial repeats male essential floral identity gene PISTILLATA, suggesting possible PISTILLATA suppression mechanism by interfering RNA females. Such pseudogenes were also found species ZW but those XY determination. Conclusions Our provides rare compelling direct support for long-standing theory reduction mediated inversions suggests Salicaceae family is associated switch gene.

Language: Английский

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Repetitive DNAs and differentiation of the ZZ/ZW sex chromosome system in the combtail fish Belontia hasselti (Perciformes: Osphronemidae)

BMC Ecology and Evolution, Journal Year: 2025, Volume and Issue: 25(1)

Published: March 18, 2025

Abstract Background Java combtail fish Belontia hasselti (Cuvier, 1831), a member of the Osphronemidae family, inhabits lakes and rivers throughout Southeast Asia Sri Lanka. Previous cytogenetic research revealed it possesses diploid chromosome number 48 chromosomes with female-heterogametic ZZ/ZW sex system, where W is distinguishable as only metacentric element in complement. Female-heterogametic systems seem to be otherwise surprisingly rare highly diverse order Perciformes and, therefore, B. provides an important comparative model evolutionary studies this teleost lineage. To examine level differentiation contribution repetitive DNAs process we combined bioinformatic analyses chromosomal mapping selected DNA classes, genomic hybridization. Results By providing first satellitome study Perciformes, herein identified 13 satellite monomers , suggesting very low diversity satDNA species. Using fluorescence situ hybridization, detectable clusters on for four monomers. Together two mapped microsatellite motifs, repeats primarily accumulated autosomes, no distinct located chromosomes. Comparative hybridization showed region female-specific or enriched chromosome. Telomeric terminated all chromosomes, additional interstitial sites were detected. Conclusion These data collectively indicate degree despite their considerable heteromorphy. Possible mechanisms that may underlie pattern are discussed.

Language: Английский

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Are you with me? Co-occurrence tests from community ecology can identify positive and negative epistasis between inversions in Mimulus guttatus

PLoS ONE, Journal Year: 2025, Volume and Issue: 20(4), P. e0321253 - e0321253

Published: April 28, 2025

Chromosomal inversions are structural genetic variants that can play a crucial role in adaptive evolution and speciation. Patterns of attraction repulsion among unlinked — whether they tend to be carried by the same or different individuals— indicate how selection is acting on these polymorphisms. In this study, we compare analytical techniques using data from 64 segregate 1373 F 2 plants yellow monkeyflower Mimulus guttatus . Mendelian assortment provides strong null hypothesis for χ2 contingency tests. Here, show co-occurrence metrics used community ecology provide additional insight regarding coupling at genotypic level. The centered Jaccard/Tanimoto index affinity score describe specific way interact generate epistasis plant survival. We further explore use network analysis visualize inversion interactions identify essential third fourth order interactions, which expand traditional pairwise scope metrics. suggest combination statistical approaches will most complete characterization fitness effects, both other polymorphisms adaptation

Language: Английский

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Repeated loss of function at HD mating-type genes and of recombination suppression without mating-type locus linkage in anther-smut fungi

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2024, Volume and Issue: unknown

Published: March 4, 2024

A wide diversity of mating systems occur in nature, with frequent evolutionary transitions mating-compatibility mechanisms. Basidiomycete fungi typically have two mating-type loci controlling compatibility, HD and PR, usually residing on different chromosomes. In Microbotryum anther-smut fungi, there been repeated events linkage between the through chromosome fusions, leading to large non-recombining regions. By generating high-quality genome assemblies, we found that sister species parasitizing Dianthus plants, M. superbum shykoffianum, as well distantly related scorzonarae, their PR chromosomes, but fused part ancestral chromosome. Furthermore, progressive extensions recombination suppression generated strata. all three species, rearrangements suggest existence a transient stage HD-PR by whole fusion, and, unexpectedly, genes lost function. superbum, multiple natural diploid strains were homozygous, disrupted HD2 gene was hardly expressed. Mating tests confirmed single genetic factor controlled compatibility (i.e. PR) haploid identical alleles could mate produce infectious hyphae. The therefore function control these species. While loss has reported few basidiomycete are first documented cases for determination heterothallic fungi. is beneficial under selfing can thus be achieved repeatedly, convergence distant lineages, involving genomic or similar pathways.

Language: Английский

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Making sense of recent models of the “sheltering” hypothesis for recombination arrest between sex chromosomes

Evolution, Journal Year: 2024, Volume and Issue: unknown

Published: Oct. 14, 2024

Abstract In their most extreme form, sex chromosomes exhibit a complete lack of genetic recombination along much length in the heterogametic sex. Some recent models explain evolution such suppressed by “sheltering” deleterious mutations chromosomal inversions that prevent around polymorphic locus controlling This sheltering hypothesis is based on following reasoning. An inversion associated with male-determining allele (with male heterogamety) present only heterozygous state. If an carries lower-than-average number mutations, it will accrue selective advantage and be sheltered from homozygosity for any due to enforced heterozygosity itself. It can, therefore, become fixed among all carriers allele. Recent population genetics this process are discussed. shown that, except under unlikely scenario high degree recessivity type other fitness effects have, at best, modest advantage; they usually accumulate proto-Y rate close to, or less than, neutral expectation. While existence does not necessarily spread Y-linked inversions, provide significant them.

Language: Английский

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Dosage compensation in non-model insects – progress and perspectives

Trends in Genetics, Journal Year: 2024, Volume and Issue: 41(1), P. 76 - 98

Published: Sept. 27, 2024

Language: Английский

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Deleterious mutations can contribute to the evolution of recombination suppression between sex chromosomes

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2024, Volume and Issue: unknown

Published: Nov. 19, 2024

Many organisms have sex chromosomes with large non-recombining regions that expand in a stepwise manner, although the underlying reasons remain poorly understood. Recently, we proposed recombination suppression may evolve simply because of presence recessive deleterious mutations within genomes. Specifically, demonstrated chromosomal inversions suppressing and carrying by chance fewer than average selective advantage. In addition, showed permanent heterozygosity Y-like facilitates fixation these less-loaded sheltering effect, i.e., preventing expression homozygous state when they increase frequency. contrast, similar autosomes suffer from disadvantage as their frequency increases, fixation. However, methodology significance our previous study been questioned. Here, present new analyses further reinforce original claims, demonstrating lower-load advantage effect can explain on over broad range parameter values. We show mechanisms promote at rates exceeding those expected under drift alone. used, control, population size Y chromosome, which, argue, provides appropriate neutral control for effect. also address criticisms regarding focus surviving first 20 generations figure study, stemmed misunderstanding what this was intended to illustrate. Including all inversions, even went extinct generations, does not alter conclusions. Overall, offers support theory based combination addresses questions about its applicability.

Language: Английский

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Evidence of a Slower-Z effect in Schistosoma japonicum

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2024, Volume and Issue: unknown

Published: July 4, 2024

Abstract Sex-linked and autosomal loci experience different selective pressures evolutionary dynamics. X (or Z) chromosomes are often hemizygous, as Y W) degenerate. Such hemizygous regions can be under greater efficacy of selection, recessive mutations immediately exposed to selection in the heterogametic sex (the so-called Faster-X or Faster-Z effect). However, young non-recombining regions, Y/W have many functional genes, X/Z-linked therefore diploid. The sheltering on X/Z by homolog is expected drive a Slower-X (Slower-Z) effect for diploid loci, i.e. reduction selection. While has been studied extensively, much less known empirically about dynamics Z chromosomes. Here, we took advantage published population genomic data female-heterogametic human parasite Schistosoma japonicum characterize gene content diversity levels chromosome. We used metrics acting genes test differences relative autosomes. found consistent patterns suggesting reduced Ne, purifying both regions. Moreover, relaxed was particularly pronounced female-biased Z, predicted Slower-Z theory.

Language: Английский

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