1
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Filatov DA. Evolution of a plant sex chromosome driven by expanding pericentromeric recombination suppression. Sci Rep 2024; 14:1373. [PMID: 38228625 DOI: 10.1038/s41598-024-51153-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 01/01/2024] [Indexed: 01/18/2024] Open
Abstract
Recombination suppression around sex-determining gene(s) is a key step in evolution of sex chromosomes, but it is not well understood how it evolves. Recently evolved sex-linked regions offer an opportunity to understand the mechanisms of recombination cessation. This paper analyses such a region on Silene latifolia (Caryophyllaceae) sex chromosomes, where recombination was suppressed in the last 120 thousand years ("stratum 3"). Locating the boundaries of the stratum 3 in S. latifolia genome sequence revealed that this region is far larger than assumed previously-it is about 14 Mb long and includes 202 annotated genes. A gradient of X:Y divergence detected in the stratum 3, with divergence increasing proximally, indicates gradual recombination cessation, possibly caused by expansion of pericentromeric recombination suppression (PRS) into the pseudoautosomal region. Expansion of PRS was also the likely cause for the formation of the older stratum 2 on S. latifolia sex chromosomes. The role of PRS in sex chromosome evolution has been underappreciated, but it may be a significant factor, especially in the species with large chromosomes where PRS is often extensive.
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Affiliation(s)
- Dmitry A Filatov
- Department of Biology, University of Oxford, Oxford, OX1 3RB, UK.
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2
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Heterochiasmy and Sex Chromosome Evolution in Silene. Genes (Basel) 2023; 14:genes14030543. [PMID: 36980816 PMCID: PMC10048291 DOI: 10.3390/genes14030543] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 02/17/2023] [Accepted: 02/21/2023] [Indexed: 02/24/2023] Open
Abstract
The evolution of a non-recombining sex-specific region is a key step in sex chromosome evolution. Suppression of recombination between the (proto-) X- and Y-chromosomes in male meiosis creates a non-recombining Y-linked region (NRY), while the X-chromosome continues to recombine in females. Lack of recombination in the NRY defines its main properties—genetic degeneration and accumulation of repetitive DNA, making X and Y chromosomes very different from each other. How and why recombination suppression on sex chromosomes evolves remains controversial. A strong difference in recombination rates between the sexes (heterochiasmy) can facilitate or even cause recombination suppression. In the extreme case—complete lack of recombination in the heterogametic sex (achiasmy)—the entire sex-specific chromosome is automatically non-recombining. In this study, I analyse sex-specific recombination rates in a dioecious plant Silene latifolia (Caryophyllaceae), which evolved separate sexes and sex chromosomes ~11 million years ago. I reconstruct high-density RNAseq-based genetic maps including over five thousand genic markers for the two sexes separately. The comparison of the male and female maps reveals only modest heterochiasmy across the genome, with the exception of the sex chromosomes, where recombination is suppressed in males. This indicates that heterochiasmy likely played only a minor, if any, role in NRY evolution in S. latifolia, as recombination suppression is specific to NRY rather than to the entire genome in males. Other mechanisms such as structural rearrangements and/or epigenetic modifications were likely involved, and comparative genome analysis and genetic mapping in multiple Silene species will help to shed light on the mechanism(s) of recombination suppression that led to the evolution of sex chromosomes.
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3
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Bergman J, Schierup MH. Evolutionary dynamics of pseudoautosomal region 1 in humans and great apes. Genome Biol 2022; 23:215. [PMID: 36253794 PMCID: PMC9575207 DOI: 10.1186/s13059-022-02784-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 09/30/2022] [Indexed: 12/03/2022] Open
Abstract
Background The pseudoautosomal region 1 (PAR1) is a 2.7 Mb telomeric region of human sex chromosomes. PAR1 has a crucial role in ensuring proper segregation of sex chromosomes during male meiosis, exposing it to extreme recombination and mutation processes. We investigate PAR1 evolution using population genomic datasets of extant humans, eight populations of great apes, and two archaic human genome sequences. Results We find that PAR1 is fast evolving and closer to evolutionary nucleotide equilibrium than autosomal telomeres. We detect a difference between substitution patterns and extant diversity in PAR1, mainly driven by the conflict between strong mutation and recombination-associated fixation bias at CpG sites. We detect excess C-to-G mutations in PAR1 of all great apes, specific to the mutagenic effect of male recombination. Despite recent evidence for Y chromosome introgression from humans into Neanderthals, we find that the Neanderthal PAR1 retained similarity to the Denisovan sequence. We find differences between substitution spectra of these archaics suggesting rapid evolution of PAR1 in recent hominin history. Frequency analysis of alleles segregating in females and males provided no evidence for recent sexual antagonism in this region. We study repeat content and double-strand break hotspot regions in PAR1 and find that they may play roles in ensuring the obligate X-Y recombination event during male meiosis. Conclusions Our study provides an unprecedented quantification of population genetic forces governing PAR1 biology across extant and extinct hominids. PAR1 evolutionary dynamics are predominantly governed by recombination processes with a strong impact on mutation patterns across all species. Supplementary Information The online version contains supplementary material available at 10.1186/s13059-022-02784-x.
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Affiliation(s)
- Juraj Bergman
- Bioinformatics Research Centre, Aarhus University, DK-8000, Aarhus C, Denmark.
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4
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Dagilis AJ, Sardell JM, Josephson MP, Su Y, Kirkpatrick M, Peichel CL. Searching for signatures of sexually antagonistic selection on stickleback sex chromosomes. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210205. [PMID: 35694749 PMCID: PMC9189504 DOI: 10.1098/rstb.2021.0205] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Intralocus sexually antagonistic selection occurs when an allele is beneficial to one sex but detrimental to the other. This form of selection is thought to be key to the evolution of sex chromosomes but is hard to detect. Here we perform an analysis of phased young sex chromosomes to look for signals of sexually antagonistic selection in the Japan Sea stickleback (Gasterosteus nipponicus). Phasing allows us to date the suppression of recombination on the sex chromosome and provides unprecedented resolution to identify sexually antagonistic selection in the recombining region of the chromosome. We identify four windows with elevated divergence between the X and Y in the recombining region, all in or very near genes associated with phenotypes potentially under sexually antagonistic selection in humans. We are unable, however, to rule out the alternative hypothesis that the peaks of divergence result from demographic effects. Thus, although sexually antagonistic selection is a key hypothesis for the formation of supergenes on sex chromosomes, it remains challenging to detect. This article is part of the theme issue ‘Genomic architecture of supergenes: causes and evolutionary consequences’.
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Affiliation(s)
- Andrius J Dagilis
- Department of Integrative Biology, University of Texas, Austin TX 78712, USA.,Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Jason M Sardell
- Department of Integrative Biology, University of Texas, Austin TX 78712, USA
| | - Matthew P Josephson
- Division of Evolutionary Ecology, Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland
| | - Yiheng Su
- Department of Computer Science, University of Texas, Austin TX 78712, USA
| | - Mark Kirkpatrick
- Department of Integrative Biology, University of Texas, Austin TX 78712, USA
| | - Catherine L Peichel
- Division of Evolutionary Ecology, Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland
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5
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Filatov DA. Recent expansion of the non-recombining sex-linked region on Silene latifolia sex chromosomes. J Evol Biol 2022; 35:1696-1708. [PMID: 35834179 PMCID: PMC10083954 DOI: 10.1111/jeb.14063] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 06/19/2022] [Accepted: 06/21/2022] [Indexed: 11/27/2022]
Abstract
Evolution of a non-recombining sex-specific region on the Y (or W) chromosome (NRY) is a key step in sex chromosome evolution, but how recombination suppression evolves is not well understood. Studies in many different organisms indicated that NRY evolution often involves several expansion steps. Why such NRY expansions occur remains unclear, although it is though that they are likely driven by sexually antagonistic selection. This paper describes a recent NRY expansion due to shift of the pseudoautosomal boundary on the sex chromosomes of a dioecious plant Silene latifolia. The shift resulted in inclusion of at least 16 pseudoautosomal genes into the NRY. This region is pseudoautosomal in closely related Silene dioica and Silene diclinis, indicating that the NRY expansion occurred in S. latifolia after it speciated from the other species ~120 thousand years ago. As S. latifolia and S. dioica actively hybridise across Europe, interspecific gene flow could blur the PAR boundary in these species. The pseudoautosomal genes have significantly elevated genetic diversity (π ~ 3% at synonymous sites), which is consistent with balancing selection maintaining diversity in this region. The recent shift of the PAR boundary in S. latifolia offers an opportunity to study the process of on-going NRY expansion.
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6
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Coelho SM, Umen J. Switching it up: algal insights into sexual transitions. PLANT REPRODUCTION 2021; 34:287-296. [PMID: 34181073 PMCID: PMC8566403 DOI: 10.1007/s00497-021-00417-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 06/02/2021] [Indexed: 05/03/2023]
Abstract
While the process of meiosis is highly conserved across eukaryotes, the sexual systems that govern life cycle phase transitions are surprisingly labile. Switches between sexual systems have profound evolutionary and ecological consequences, in particular for plants, but our understanding of the fundamental mechanisms and ultimate causes underlying these transitions is still surprisingly incomplete. We explore here the idea that brown and green algae may be interesting comparative models that can increase our understanding of relevant processes in plant reproductive biology, from evolution of gamete dimorphism, gametogenesis, sex determination and transitions in sex-determining systems.
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Affiliation(s)
- Susana M Coelho
- Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, 72076, Tübingen, Germany.
| | - James Umen
- Donald Danforth Plant Science Center, St. Louis, MO, 63132, USA
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7
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Schenkel MA, Beukeboom LW, Pen I. Epistatic interactions between sex chromosomes and autosomes can affect the stability of sex determination systems. J Evol Biol 2021; 34:1666-1677. [PMID: 34551179 PMCID: PMC9291586 DOI: 10.1111/jeb.13939] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 09/13/2021] [Accepted: 09/15/2021] [Indexed: 12/19/2022]
Abstract
Sex determination (SD) is an essential and ancient developmental process, but the genetic systems that regulate this process are surprisingly variable. Why SD mechanisms vary so much is a longstanding question in evolutionary biology. SD genes are generally located on sex chromosomes which also carry genes that interact epistatically with autosomes to affect fitness. How this affects the evolutionary stability of SD mechanisms is still unknown. Here, we explore how epistatic interactions between a sexually antagonistic (SA) non‐SD gene, located on either an ancestral or novel sex chromosome, and an autosomal gene affect the conditions under which an evolutionary transition to a new SD system occurs. We find that when the SD gene is linked to an ancestral sex‐chromosomal gene which engages in epistatic interactions, epistasis enhances the stability of the sex chromosomes so that they are retained under conditions where transitions would otherwise occur. This occurs both when weaker fitness effects are associated with the ancestral sex chromosome pair or stronger fitness effects associated with a newly evolved SD gene. However, the probability that novel SD genes spread is unaffected if they arise near genes involved in epistasis. This discrepancy occurs because, on autosomes, SA allele frequencies are typically lower than on sex chromosomes. In our model, increased frequencies of these alleles contribute to a higher frequency of epistasis which may therefore more readily occur on sex chromosomes. Because sex chromosome–autosome interactions are abundant and can take several forms, they may play a large role in maintaining sex chromosomes.
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Affiliation(s)
- Martijn A Schenkel
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands
| | - Leo W Beukeboom
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands
| | - Ido Pen
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands
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8
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Kratochvíl L, Stöck M, Rovatsos M, Bullejos M, Herpin A, Jeffries DL, Peichel CL, Perrin N, Valenzuela N, Pokorná MJ. Expanding the classical paradigm: what we have learnt from vertebrates about sex chromosome evolution. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200097. [PMID: 34304593 PMCID: PMC8310716 DOI: 10.1098/rstb.2020.0097] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/26/2021] [Indexed: 12/15/2022] Open
Abstract
Until recently, the field of sex chromosome evolution has been dominated by the canonical unidirectional scenario, first developed by Muller in 1918. This model postulates that sex chromosomes emerge from autosomes by acquiring a sex-determining locus. Recombination reduction then expands outwards from this locus, to maintain its linkage with sexually antagonistic/advantageous alleles, resulting in Y or W degeneration and potentially culminating in their disappearance. Based mostly on empirical vertebrate research, we challenge and expand each conceptual step of this canonical model and present observations by numerous experts in two parts of a theme issue of Phil. Trans. R. Soc. B. We suggest that greater theoretical and empirical insights into the events at the origins of sex-determining genes (rewiring of the gonadal differentiation networks), and a better understanding of the evolutionary forces responsible for recombination suppression are required. Among others, crucial questions are: Why do sex chromosome differentiation rates and the evolution of gene dose regulatory mechanisms between male versus female heterogametic systems not follow earlier theory? Why do several lineages not have sex chromosomes? And: What are the consequences of the presence of (differentiated) sex chromosomes for individual fitness, evolvability, hybridization and diversification? We conclude that the classical scenario appears too reductionistic. Instead of being unidirectional, we show that sex chromosome evolution is more complex than previously anticipated and principally forms networks, interconnected to potentially endless outcomes with restarts, deletions and additions of new genomic material. This article is part of the theme issue 'Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part II)'.
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Affiliation(s)
- Lukáš Kratochvíl
- Department of Ecology, Faculty of Science, Charles University, Viničná 7, Prague, Czech Republic
| | - Matthias Stöck
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries - IGB (Forschungsverbund Berlin), Müggelseedamm 301, 12587 Berlin, Germany
- Amphibian Research Center, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
| | - Michail Rovatsos
- Department of Ecology, Faculty of Science, Charles University, Viničná 7, Prague, Czech Republic
| | - Mónica Bullejos
- Department of Experimental Biology, Faculty of Experimental Sciences, University of Jaén, Las Lagunillas Campus S/N, 23071 Jaén, Spain
| | - Amaury Herpin
- INRAE, LPGP, 35000 Rennes, France
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Sciences, Hunan Normal University, Changsha 410081, Hunan, People's Republic of China
| | - Daniel L. Jeffries
- Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Catherine L. Peichel
- Institute of Ecology and Evolution, University of Bern, CH-3012 Bern, Switzerland
| | - Nicolas Perrin
- Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Nicole Valenzuela
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA
| | - Martina Johnson Pokorná
- Department of Ecology, Faculty of Science, Charles University, Viničná 7, Prague, Czech Republic
- Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Rumburská 89, Liběchov, Czech Republic
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9
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Son JH, Meisel RP. Gene-Level, but Not Chromosome-Wide, Divergence between a Very Young House Fly Proto-Y Chromosome and Its Homologous Proto-X Chromosome. Mol Biol Evol 2021; 38:606-618. [PMID: 32986844 PMCID: PMC7826193 DOI: 10.1093/molbev/msaa250] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
X and Y chromosomes are usually derived from a pair of homologous autosomes, which then diverge from each other over time. Although Y-specific features have been characterized in sex chromosomes of various ages, the earliest stages of Y chromosome evolution remain elusive. In particular, we do not know whether early stages of Y chromosome evolution consist of changes to individual genes or happen via chromosome-scale divergence from the X. To address this question, we quantified divergence between young proto-X and proto-Y chromosomes in the house fly, Musca domestica. We compared proto-sex chromosome sequence and gene expression between genotypic (XY) and sex-reversed (XX) males. We find evidence for sequence divergence between genes on the proto-X and proto-Y, including five genes with mitochondrial functions. There is also an excess of genes with divergent expression between the proto-X and proto-Y, but the number of genes is small. This suggests that individual proto-Y genes, but not the entire proto-Y chromosome, have diverged from the proto-X. We identified one gene, encoding an axonemal dynein assembly factor (which functions in sperm motility), that has higher expression in XY males than XX males because of a disproportionate contribution of the proto-Y allele to gene expression. The upregulation of the proto-Y allele may be favored in males because of this gene's function in spermatogenesis. The evolutionary divergence between proto-X and proto-Y copies of this gene, as well as the mitochondrial genes, is consistent with selection in males affecting the evolution of individual genes during early Y chromosome evolution.
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Affiliation(s)
- Jae Hak Son
- Department of Biology and Biochemistry, University of Houston, Houston, TX.,Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT
| | - Richard P Meisel
- Department of Biology and Biochemistry, University of Houston, Houston, TX
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10
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Cai Z, Yang C, Liao J, Song H, Zhang S. Sex-biased genes and metabolites explain morphologically sexual dimorphism and reproductive costs in Salix paraplesia catkins. HORTICULTURE RESEARCH 2021; 8:125. [PMID: 34059667 PMCID: PMC8166972 DOI: 10.1038/s41438-021-00566-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 03/16/2021] [Accepted: 03/22/2021] [Indexed: 05/10/2023]
Abstract
Dioecious species evolved from species with monomorphic sex systems in order to achieve overall fitness gains by separating male and female functions. As reproductive organs, unisexual flowers have different reproductive roles and exhibit conspicuous sexual dimorphism. To date, little is known about the temporal variations in and molecular mechanisms underlying the morphology and reproductive costs of dioecious flowers. We investigated male and female flowers of Salix paraplesia in three flowering stages before pollination (the early, blooming and late stages) via transcriptional sequencing as well as metabolite content and phenotypic analysis. We found that a large number of sex-biased genes, rather than sex-limited genes, were responsible for sexual dimorphism in S. paraplesia flowers and that the variation in gene expression in male flowers intensified this situation throughout flower development. The temporal dynamics of sex-biased genes derived from changes in reproductive function during the different flowering stages. Sexually differentiated metabolites related to respiration and flavonoid biosynthesis exhibited the same bias directions as the sex-biased genes. These sex-biased genes were involved mainly in signal transduction, photosynthesis, respiration, cell proliferation, phytochrome biosynthesis, and phenol metabolism; therefore, they resulted in more biomass accumulation and higher energy consumption in male catkins. Our results indicated that sex-biased gene expression in S. paraplesia flowers is associated with different reproductive investments in unisexual flowers; male flowers require a greater reproductive investment to meet their higher biomass accumulation and energy consumption needs.
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Affiliation(s)
- Zeyu Cai
- Key Laboratory of Mountain Surface Processes and Ecological Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Congcong Yang
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, China
| | - Jun Liao
- College of Geography and Tourism, Chongqing Normal University, Chongqing, China
| | - Haifeng Song
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, China
| | - Sheng Zhang
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, China.
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11
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Chae T, Harkess A, Moore RC. Sex-linked gene expression and the emergence of hermaphrodites in Carica papaya. AMERICAN JOURNAL OF BOTANY 2021; 108:1029-1041. [PMID: 34156700 DOI: 10.1002/ajb2.1689] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 02/08/2021] [Indexed: 06/13/2023]
Abstract
PREMISE One evolutionary path from hermaphroditism to dioecy is via a gynodioecious intermediate. The evolution of dioecy may also coincide with the formation of sex chromosomes that possess sex-determining loci that are physically linked in a region of suppressed recombination. Dioecious papaya (Carica papaya) has an XY chromosome system, where the presence of a Y chromosome determines maleness. However, in cultivation, papaya is gynodioecious, due to the conversion of the male Y chromosome to a hermaphroditic Yh chromosome during its domestication. METHODS We investigated gene expression linked to the X, Y, and Yh chromosomes at different floral developmental stages to identify differentially expressed genes that may be involved in the sexual transition of males to hermaphrodites. RESULTS We identified 309 sex-biased genes found on the sex chromosomes, most of which are found in the pseudoautosomal regions. Female (XX) expression in the sex-determining region was almost double that of X-linked expression in males (XY) and hermaphrodites (XYh ), which rules out dosage compensation for most sex-linked genes; although, an analysis of hemizygous X-linked loci found evidence of partial dosage compensation. Furthermore, we identified a candidate gene associated with sex determination and the transition to hermaphroditism, a homolog of the MADS-box protein SHORT VEGETATIVE PHASE. CONCLUSIONS We identified a pattern of partial dosage compensation for hemizygous genes located in the papaya sex-determining region. Furthermore, we propose that loss-of-expression of the Y-linked SHORT VEGETATIVE PHASE homolog facilitated the transition from males to hermaphrodites in papaya.
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Affiliation(s)
- Taylor Chae
- Department of Biology, Miami University, Oxford, OH
| | - Alex Harkess
- Department of Crop, Soil, and Environmental Sciences, Auburn University, Auburn, AL
- HudsonAlpha Institute for Biotechnology, Huntsville, AL
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12
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Meisel RP. The maintenance of polygenic sex determination depends on the dominance of fitness effects which are predictive of the role of sexual antagonism. G3 (BETHESDA, MD.) 2021; 11:6261074. [PMID: 33930135 PMCID: PMC8496315 DOI: 10.1093/g3journal/jkab149] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 04/23/2021] [Indexed: 12/18/2022]
Abstract
In species with polygenic sex determination (PSD), 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 PSD 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 PSD 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 PSD 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 PSD than dominant, recessive, or additive fitness effects. The overdominant fitness effects that maintain PSD tend to have proto-Y chromosomes with sexually antagonistic effects (male-beneficial and female-detrimental). In contrast, dominant fitness effects that maintain PSD 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 PSD will be maintained as well as the role sexually antagonistic selection is expected to play in maintaining the polymorphism.
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Affiliation(s)
- Richard P Meisel
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77204, USA
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13
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Monteiro B, Arenas M, Prata MJ, Amorim A. Evolutionary dynamics of the human pseudoautosomal regions. PLoS Genet 2021; 17:e1009532. [PMID: 33872316 PMCID: PMC8084340 DOI: 10.1371/journal.pgen.1009532] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Revised: 04/29/2021] [Accepted: 04/06/2021] [Indexed: 01/19/2023] Open
Abstract
Recombination between the X and Y human sex chromosomes is limited to the two pseudoautosomal regions (PARs) that present quite distinct evolutionary origins. Despite the crucial importance for male meiosis, genetic diversity patterns and evolutionary dynamics of these regions are poorly understood. In the present study, we analyzed and compared the genetic diversity of the PAR regions using publicly available genomic sequences encompassing both PAR1 and PAR2. Comparisons were performed through allele diversities, linkage disequilibrium status and recombination frequencies within and between X and Y chromosomes. In agreement with previous studies, we confirmed the role of PAR1 as a male-specific recombination hotspot, but also observed similar characteristic patterns of diversity in both regions although male recombination occurs at PAR2 to a much lower extent (at least one recombination event at PAR1 and in ≈1% in normal male meioses at PAR2). Furthermore, we demonstrate that both PARs harbor significantly different allele frequencies between X and Y chromosomes, which could support that recombination is not sufficient to homogenize the pseudoautosomal gene pool or is counterbalanced by other evolutionary forces. Nevertheless, the observed patterns of diversity are not entirely explainable by sexually antagonistic selection. A better understanding of such processes requires new data from intergenerational transmission studies of PARs, which would be decisive on the elucidation of PARs evolution and their role in male-driven heterosomal aneuploidies.
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Affiliation(s)
- Bruno Monteiro
- Institute of Investigation and Innovation in Health (i3S). University of Porto, Porto, Portugal
- Institute of Molecular Pathology and Immunology (IPATIMUP), University of Porto, Porto, Portugal
| | - Miguel Arenas
- Department of Biochemistry, Genetics and Immunology, University of Vigo, Vigo, Spain
- CINBIO (Biomedical Research Centre), University of Vigo, Vigo, Spain
| | - Maria João Prata
- Institute of Investigation and Innovation in Health (i3S). University of Porto, Porto, Portugal
- Institute of Molecular Pathology and Immunology (IPATIMUP), University of Porto, Porto, Portugal
- Faculty of Sciences, University of Porto, Porto, Portugal
- * E-mail:
| | - António Amorim
- Institute of Investigation and Innovation in Health (i3S). University of Porto, Porto, Portugal
- Institute of Molecular Pathology and Immunology (IPATIMUP), University of Porto, Porto, Portugal
- Faculty of Sciences, University of Porto, Porto, Portugal
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14
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Wright SI. Deborah Charlesworth, winner of the society for the study of evolution's inaugural lifetime achievement award: Evolutionary biology for the genomics era. Evolution 2021; 75:566-568. [PMID: 33592116 DOI: 10.1111/evo.14195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 02/01/2021] [Accepted: 02/05/2021] [Indexed: 11/29/2022]
Affiliation(s)
- Stephen I Wright
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
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15
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Sakamoto T, Innan H. Establishment of a new sex-determining allele driven by sexually antagonistic selection. G3-GENES GENOMES GENETICS 2021; 11:6028988. [PMID: 33561232 PMCID: PMC8022746 DOI: 10.1093/g3journal/jkaa031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 11/24/2020] [Indexed: 12/04/2022]
Abstract
The turnover of sex-determining loci has repeatedly occurred in a number of species, rather than having a diverged pair of sex chromosomes. We model the turnover process by considering a linked locus under sexually antagonistic selection. The entire process of a turnover may be divided into two phases, which are referred to as the stochastic and deterministic phases. The stochastic phase is when a new sex-determining allele just arises and is still rare and random genetic drift plays an important role. In the deterministic phase, the new allele further increases in frequency by positive selection. The theoretical results currently available are for the deterministic phase, which demonstrated that a turnover of a newly arisen sex-determining locus could benefit from selection at a linked locus under sexually antagonistic selection, by assuming that sexually antagonistic selection works in a form of balancing selection. In this work, we provide a comprehensive theoretical description of the entire process from the stochastic phase to the deterministic phase. In addition to balancing selection, we explore several other modes of selection on the linked locus. Our theory allows us make a quantitative argument on the rate of turnover and the effect of the mode of selection at the linked locus. We also performed simulations to explore the pattern of polymorphism around the new sex-determining locus. We find that the pattern of polymorphism is informative to infer how selection worked through the turnover process.
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Affiliation(s)
- Takahiro Sakamoto
- Department of Evolutionary Studies of Biosystems, SOKENDAI, The Graduate University for Advanced Studies, Shonan Village, Hayama, Kanagawa, 240-0193, Japan
| | - Hideki Innan
- Department of Evolutionary Studies of Biosystems, SOKENDAI, The Graduate University for Advanced Studies, Shonan Village, Hayama, Kanagawa, 240-0193, Japan
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16
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Morris J, Darolti I, van der Bijl W, Mank JE. High-resolution characterization of male ornamentation and re-evaluation of sex linkage in guppies. Proc Biol Sci 2020; 287:20201677. [PMID: 33081622 DOI: 10.1098/rspb.2020.1677] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Coloration plays a key role in the ecology of many species, influencing how an organism interacts with its environment, other species and conspecifics. Guppies are sexually dimorphic, with males displaying sexually selected coloration resulting from female preference. Previous work has suggested that much of guppy colour pattern variation is Y-linked. However, it remains unclear how many individual colour patterns are Y-linked in natural populations as much of the previous work has focused on phenotypes either not found in the wild, or aggregate measures such as total colour area. Moreover, ornaments have traditionally been identified and delineated by hand, and computational methods now make it possible to extract pixels and identify ornaments with automated methods, reducing the potential for human bias. Here we developed a pipeline for semi-automated ornament identification and high-resolution image analysis of male guppy colour patterns and applied it to a multigenerational pedigree. Our results show that loci controlling the presence or the absence of individual male ornaments in our population are not predominantly Y-linked. However, we find that ornaments of similar colour are not independent of each other, and modifier loci that affect whole animal coloration appear to be at least partially Y-linked. Considering these results, Y-linkage of individual ornaments may not be important in driving colour changes in natural populations of guppies, or in expansions of the non-recombining Y region, while Y-linked modifier loci that affect aggregate traits may well play an important role.
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Affiliation(s)
- Jake Morris
- Department of Genetics, Evolution and Environment, University College London, London, UK
| | - Iulia Darolti
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
| | - Wouter van der Bijl
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
| | - Judith E Mank
- Department of Genetics, Evolution and Environment, University College London, London, UK.,Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
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17
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Abstract
Females and males may face different selection pressures. Accordingly, alleles that confer a benefit for one sex often incur a cost for the other. Classic evolutionary theory holds that the X chromosome, whose sex-biased transmission sees it spending more time in females, should value females more than males, whereas autosomes, whose transmission is unbiased, should value both sexes equally. However, recent mathematical and empirical studies indicate that male-beneficial alleles may be more favoured by the X chromosome than by autosomes. Here we develop a gene's-eye-view approach that reconciles the classic view with these recent discordant results, by separating a gene's valuation of female versus male fitness from its ability to induce fitness effects in either sex. We use this framework to generate new comparative predictions for sexually antagonistic evolution in relation to dosage compensation, sex-specific mortality and assortative mating, revealing how molecular mechanisms, ecology and demography drive variation in masculinization versus feminization across the genome.
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Affiliation(s)
| | - Andy Gardner
- School of Biology, University of St Andrews, St Andrews KY16 9TH, UK
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18
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The Location of the Pseudoautosomal Boundary in Silene latifolia. Genes (Basel) 2020; 11:genes11060610. [PMID: 32486434 PMCID: PMC7348893 DOI: 10.3390/genes11060610] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 05/25/2020] [Accepted: 05/28/2020] [Indexed: 12/19/2022] Open
Abstract
Y-chromosomes contain a non-recombining region (NRY), and in many organisms it was shown that the NRY expanded over time. How and why the NRY expands remains unclear. Young sex chromosomes, where NRY expansion occurred recently or is on-going, offer an opportunity to study the causes of this process. Here, we used the plant Silene latifolia, where sex chromosomes evolved ~11 million years ago, to study the location of the boundary between the NRY and the recombining pseudoautosomal region (PAR). The previous work devoted to the NRY/PAR boundary in S. latifolia was based on a handful of genes with locations approximately known from the genetic map. Here, we report the analysis of 86 pseudoautosomal and sex-linked genes adjacent to the S. latifolia NRY/PAR boundary to establish the location of the boundary more precisely. We take advantage of the dense genetic map and polymorphism data from wild populations to identify 20 partially sex-linked genes located in the “fuzzy boundary”, that rarely recombines in male meiosis. Genes proximal to this fuzzy boundary show no evidence of recombination in males, while the genes distal to this partially-sex-linked region are actively recombining in males. Our results provide a more accurate location for the PAR boundary in S. latifolia, which will help to elucidate the causes of PAR boundary shifts leading to NRY expansion over time.
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19
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Ma WJ, Carpentier F, Giraud T, Hood ME. Differential Gene Expression between Fungal Mating Types Is Associated with Sequence Degeneration. Genome Biol Evol 2020; 12:243-258. [PMID: 32058544 PMCID: PMC7150583 DOI: 10.1093/gbe/evaa028] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/09/2020] [Indexed: 12/13/2022] Open
Abstract
Degenerative mutations in non-recombining regions, such as in sex chromosomes, may lead to differential expression between alleles if mutations occur stochastically in one or the other allele. Reduced allelic expression due to degeneration has indeed been suggested to occur in various sex-chromosome systems. However, whether an association occurs between specific signatures of degeneration and differential expression between alleles has not been extensively tested, and sexual antagonism can also cause differential expression on sex chromosomes. The anther-smut fungus Microbotryum lychnidis-dioicae is ideal for testing associations between specific degenerative signatures and differential expression because 1) there are multiple evolutionary strata on the mating-type chromosomes, reflecting successive recombination suppression linked to mating-type loci; 2) separate haploid cultures of opposite mating types help identify differential expression between alleles; and 3) there is no sexual antagonism as a confounding factor accounting for differential expression. We found that differentially expressed genes were enriched in the four oldest evolutionary strata compared with other genomic compartments, and that, within compartments, several signatures of sequence degeneration were greater for differentially expressed than non-differentially expressed genes. Two particular degenerative signatures were significantly associated with lower expression levels within differentially expressed allele pairs: upstream insertion of transposable elements and mutations truncating the protein length. Other degenerative mutations associated with differential expression included nonsynonymous substitutions and altered intron or GC content. The association between differential expression and allele degeneration is relevant for a broad range of taxa where mating compatibility or sex is determined by genes located in large regions where recombination is suppressed.
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Affiliation(s)
- Wen-Juan Ma
- Department of Biology, Amherst College, Amherst, MA
| | - Fantin Carpentier
- Ecologie Systematique et Evolution, Université Paris-Saclay, CNRS, AgroParisTech, Orsay, France
| | - Tatiana Giraud
- Ecologie Systematique et Evolution, Université Paris-Saclay, CNRS, AgroParisTech, Orsay, France
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20
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Xu L, Wa Sin SY, Grayson P, Edwards SV, Sackton TB. Evolutionary Dynamics of Sex Chromosomes of Paleognathous Birds. Genome Biol Evol 2020; 11:2376-2390. [PMID: 31329234 PMCID: PMC6735826 DOI: 10.1093/gbe/evz154] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/10/2019] [Indexed: 12/20/2022] Open
Abstract
Standard models of sex chromosome evolution propose that recombination suppression leads to the degeneration of the heterogametic chromosome, as is seen for the Y chromosome in mammals and the W chromosome in most birds. Unlike other birds, paleognaths (ratites and tinamous) possess large nondegenerate regions on their sex chromosomes (PARs or pseudoautosomal regions). It remains unclear why these large PARs are retained over >100 Myr, and how this retention impacts the evolution of sex chromosomes within this system. To address this puzzle, we analyzed Z chromosome evolution and gene expression across 12 paleognaths, several of whose genomes have recently been sequenced. We confirm at the genomic level that most paleognaths retain large PARs. As in other birds, we find that all paleognaths have incomplete dosage compensation on the regions of the Z chromosome homologous to degenerated portions of the W (differentiated regions), but we find no evidence for enrichments of male-biased genes in PARs. We find limited evidence for increased evolutionary rates (faster-Z) either across the chromosome or in differentiated regions for most paleognaths with large PARs, but do recover signals of faster-Z evolution in tinamou species with mostly degenerated W chromosomes, similar to the pattern seen in neognaths. Unexpectedly, in some species, PAR-linked genes evolve faster on average than genes on autosomes, suggested by diverse genomic features to be due to reduced efficacy of selection in paleognath PARs. Our analysis shows that paleognath Z chromosomes are atypical at the genomic level, but the evolutionary forces maintaining largely homomorphic sex chromosomes in these species remain elusive.
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Affiliation(s)
- Luohao Xu
- Department of Molecular Evolution and Development, University of Vienna, Austria
| | - Simon Yung Wa Sin
- Department of Organismic and Evolutionary Biology, Harvard University
- Museum of Comparative Zoology, Harvard University
- School of Biological Sciences, The University of Hong Kong, Hong Kong
| | - Phil Grayson
- Department of Organismic and Evolutionary Biology, Harvard University
- Museum of Comparative Zoology, Harvard University
| | - Scott V Edwards
- Department of Organismic and Evolutionary Biology, Harvard University
- Museum of Comparative Zoology, Harvard University
| | - Timothy B Sackton
- Informatics Group, Division of Science, Harvard University
- Corresponding author: E-mail:
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21
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Otto SP. Evolutionary potential for genomic islands of sexual divergence on recombining sex chromosomes. THE NEW PHYTOLOGIST 2019; 224:1241-1251. [PMID: 31361905 DOI: 10.1111/nph.16083] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 07/22/2019] [Indexed: 06/10/2023]
Abstract
Differentiated sex chromosomes are thought to develop through the accumulation of polymorphisms at loci subject to opposing selection between males and females, and/or between haploids and diploids. As sex chromosomes differentiate, reduced recombination becomes favored between selected loci and the sex-determining region, strengthening genetic associations between alleles favored in a sex and the corresponding sex chromosome. Here a model is analyzed to explore whether polymorphism at one sexually or ploidally antagonistic locus facilitates the spread of rare alleles at other loci experiencing antagonistic selection, promoting further differentiation of the sex chromosomes. It is found that antagonistic polymorphisms can spread and capture other such loci, building 'genomic islands' of differentiation on sex chromosomes, but the conditions are very restrictive, requiring the loci to be strongly selected, tightly linked and distant from the sex-determining region. Epistatic interactions can facilitate the promotion of polymorphism among selected loci, but only if preferentially favoring heterozygotes. Although these results apply to any taxa, plants provide a fertile ground for testing these and related theories given the recurrent evolutionary transitions to dioecy, which provide multiple opportunities to track the early evolution of sex chromosomes.
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Affiliation(s)
- Sarah P Otto
- Department of Zoology & Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
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22
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Genomic Data Reveal Conserved Female Heterogamety in Giant Salamanders with Gigantic Nuclear Genomes. G3-GENES GENOMES GENETICS 2019; 9:3467-3476. [PMID: 31439718 PMCID: PMC6778777 DOI: 10.1534/g3.119.400556] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Systems of genetic sex determination and the homology of sex chromosomes in different taxa vary greatly across vertebrates. Much progress remains to be made in understanding systems of genetic sex determination in non-model organisms, especially those with homomorphic sex chromosomes and/or large genomes. We used reduced representation genome sequencing to investigate genetic sex determination systems in the salamander family Cryptobranchidae (genera Cryptobranchus and Andrias), which typifies both of these inherent difficulties. We tested hypotheses of male- or female-heterogamety by sequencing hundreds of thousands of anonymous genomic regions in a panel of known-sex cryptobranchids and characterized patterns of presence/absence, inferred zygosity, and depth of coverage to identify sex-linked regions of these 56 gigabase genomes. Our results strongly support the hypothesis that all cryptobranchid species possess homologous systems of female heterogamety, despite maintenance of homomorphic sex chromosomes over nearly 60 million years. Additionally, we report a robust, non-invasive genetic assay for sex diagnosis in Cryptobranchus and Andrias which may have great utility for conservation efforts with these endangered salamanders. Co-amplification of these W-linked markers in both cryptobranchid genera provides evidence for long-term sex chromosome stasis in one of the most divergent salamander lineages. These findings inform hypotheses about the ancestral mode of sex determination in salamanders, but suggest that comparative data from other salamander families are needed. Our results further demonstrate that massive genomes are not necessarily a barrier to effective genome-wide sequencing and that the resulting data can be highly informative about sex determination systems in taxa with homomorphic sex chromosomes.
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23
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Sanderson BJ, Wang L, Tiffin P, Wu Z, Olson MS. Sex-biased gene expression in flowers, but not leaves, reveals secondary sexual dimorphism in Populus balsamifera. THE NEW PHYTOLOGIST 2019; 221:527-539. [PMID: 30252135 DOI: 10.1111/nph.15421] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2018] [Accepted: 06/29/2018] [Indexed: 05/11/2023]
Abstract
Because sexual dimorphism in plants is often less morphologically conspicuous than in animals, studies of sex-biased gene expression may provide a quantitative metric to better address their commonality, molecular pathways, consistency across tissues and taxa, and evolution. The presence of sex-biased gene expression in tissues other than the androecium or gynoecium, termed secondary sexual characters, suggests that these traits arose after the initial evolution of dioecy. Patterns of sequence evolution may provide evidence of positive selection that drove sexual specialization. We compared gene expression in male and female flowers and leaves of Populus balsamifera to assess the extent of sex-biased expression, and tested whether sex-biased genes exhibit elevated rates of protein evolution. Sex-biased expression was pervasive in floral tissue, but nearly absent in leaf tissue. Female-biased genes in flowers were associated with photosynthesis, whereas male-biased genes were associated with mitochondrial function. Sex-biased genes did not exhibit elevated rates of protein evolution, contrary to results from other studies in animals and plants. Our results suggest that the ecological and physiological constraints associated with the energetics of flowering, rather than sexual conflict, have probably shaped the differences in male and female gene expression in P. balsamifera.
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Affiliation(s)
- Brian J Sanderson
- Department of Biological Sciences, Texas Tech University, Box 43131, Lubbock, TX, 79409, USA
| | - Li Wang
- Department of Biological Sciences, Texas Tech University, Box 43131, Lubbock, TX, 79409, USA
- Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA, 50011, USA
| | - Peter Tiffin
- Department of Plant and Microbial Biology, University of Minnesota, St Paul, MN, 55108, USA
| | - Zhiqiang Wu
- Department of Biological Sciences, Texas Tech University, Box 43131, Lubbock, TX, 79409, USA
- Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA, 50011, USA
| | - Matthew S Olson
- Department of Biological Sciences, Texas Tech University, Box 43131, Lubbock, TX, 79409, USA
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24
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Schenkel MA, Pen I, Beukeboom LW, Billeter J. Making sense of intralocus and interlocus sexual conflict. Ecol Evol 2018; 8:13035-13050. [PMID: 30619603 PMCID: PMC6309128 DOI: 10.1002/ece3.4629] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 09/17/2018] [Accepted: 09/18/2018] [Indexed: 01/13/2023] Open
Abstract
Sexual conflict occurs because males and females are exposed to different selection pressures. This can affect many aspects of female and male biology, such as physiology, behavior, genetics, and even population ecology. Its broad impact has caused widespread interest in sexual conflict. However, a key aspect of sexual conflict is often confused; it comprises two distinct forms: intralocus and interlocus sexual conflict (IASC and IRSC). Although both are caused by sex differences in selection, they operate via different proximate and ultimate mechanisms. Intralocus sexual conflict and IRSC are often not clearly defined as separate processes in the scientific literature, which impedes a proper understanding of each form as well as of their relative impact on sexual conflict. Furthermore, our current knowledge of the genetics of these phenomena is severely limited. This prevents us from empirically testing numerous theories regarding the role of these two forms of sexual conflict in evolution. Here, we clarify the distinction between IASC and IRSC, by discussing how male and female interests differ, how and when sex-specific adaptation occurs, and how this may lead to evolutionary change. We then describe a framework for their study, focusing on how future experiments may help identify the genetics underlying these phenomena. Through this, we hope to promote a more critical reflection on IASC and IRSC as well as underline the necessity of genetic and mechanistic studies of these two phenomena.
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Affiliation(s)
- Martijn A. Schenkel
- Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningenThe Netherlands
| | - Ido Pen
- Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningenThe Netherlands
| | - Leo W. Beukeboom
- Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningenThe Netherlands
| | - Jean‐Christophe Billeter
- Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningenThe Netherlands
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25
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Avia K, Lipinska AP, Mignerot L, Montecinos AE, Jamy M, Ahmed S, Valero M, Peters AF, Cock JM, Roze D, Coelho SM. Genetic Diversity in the UV Sex Chromosomes of the Brown Alga Ectocarpus. Genes (Basel) 2018; 9:E286. [PMID: 29882839 PMCID: PMC6027523 DOI: 10.3390/genes9060286] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 05/30/2018] [Accepted: 06/05/2018] [Indexed: 12/24/2022] Open
Abstract
Three types of sex chromosome system exist in nature: diploid XY and ZW systems and haploid UV systems. For many years, research has focused exclusively on XY and ZW systems, leaving UV chromosomes and haploid sex determination largely neglected. Here, we perform a detailed analysis of DNA sequence neutral diversity levels across the U and V sex chromosomes of the model brown alga Ectocarpus using a large population dataset. We show that the U and V non-recombining regions of the sex chromosomes (SDR) exhibit about half as much neutral diversity as the autosomes. This difference is consistent with the reduced effective population size of these regions compared with the rest of the genome, suggesting that the influence of additional factors such as background selection or selective sweeps is minimal. The pseudoautosomal region (PAR) of this UV system, in contrast, exhibited surprisingly high neutral diversity and there were several indications that genes in this region may be under balancing selection. The PAR of Ectocarpus is known to exhibit unusual genomic features and our results lay the foundation for further work aimed at understanding whether, and to what extent, these structural features underlie the high level of genetic diversity. Overall, this study fills a gap between available information on genetic diversity in XY/ZW systems and UV systems and significantly contributes to advancing our knowledge of the evolution of UV sex chromosomes.
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Affiliation(s)
- Komlan Avia
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, 29688 Roscoff, France.
- Evolutionary Biology and Ecology of Algae, CNRS, Sorbonne Universités, UPMC, University of Paris VI, UC, UACH, UMI 3614, 29688 Roscoff, France.
| | - Agnieszka P Lipinska
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, 29688 Roscoff, France.
| | - Laure Mignerot
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, 29688 Roscoff, France.
| | - Alejandro E Montecinos
- Evolutionary Biology and Ecology of Algae, CNRS, Sorbonne Universités, UPMC, University of Paris VI, UC, UACH, UMI 3614, 29688 Roscoff, France.
- Facultad de Ciencias, Instituto de Ciencias Ambientales y Evolutivas, Universidad Austral de Chile, Casilla 567, Valdivia, Chile.
| | - Mahwash Jamy
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, 29688 Roscoff, France.
| | - Sophia Ahmed
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, 29688 Roscoff, France.
| | - Myriam Valero
- Evolutionary Biology and Ecology of Algae, CNRS, Sorbonne Universités, UPMC, University of Paris VI, UC, UACH, UMI 3614, 29688 Roscoff, France.
| | | | - J Mark Cock
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, 29688 Roscoff, France.
| | - Denis Roze
- Evolutionary Biology and Ecology of Algae, CNRS, Sorbonne Universités, UPMC, University of Paris VI, UC, UACH, UMI 3614, 29688 Roscoff, France.
| | - Susana M Coelho
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, 29688 Roscoff, France.
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26
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Charlesworth D. Evolution of recombination rates between sex chromosomes. Philos Trans R Soc Lond B Biol Sci 2018; 372:rstb.2016.0456. [PMID: 29109220 DOI: 10.1098/rstb.2016.0456] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/24/2017] [Indexed: 11/12/2022] Open
Abstract
In species with genetic sex-determination, the chromosomes carrying the sex-determining genes have often evolved non-recombining regions and subsequently evolved the full set of characteristics denoted by the term 'sex chromosomes'. These include size differences, creating chromosomal heteromorphism, and loss of gene functions from one member of the chromosome pair. Such characteristics and changes have been widely reviewed, and underlie molecular genetic approaches that can detect sex chromosome regions. This review deals mainly with the evolution of new non-recombining regions, focusing on how certain evolutionary situations select for suppressed recombination (rather than the proximate mechanisms causing suppressed recombination between sex chromosomes). Particularly important is the likely involvement of sexually antagonistic polymorphisms in genome regions closely linked to sex-determining loci. These may be responsible for the evolutionary strata of sex chromosomes that have repeatedly formed by recombination suppression evolving across large genome regions. More studies of recently evolved non-recombining sex-determining regions should help to test this hypothesis empirically, and may provide evidence about whether other situations can sometimes lead to sex-linked regions evolving. Similarities with other non-recombining genome regions are discussed briefly, to illustrate common features of the different cases, though no general properties apply to all of them.This article is part of the themed issue 'Evolutionary causes and consequences of recombination rate variation in sexual organisms'.
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Affiliation(s)
- Deborah Charlesworth
- Institute of Evolutionary Biology, School of Biological Sciences, Ashworth Laboratory, University of Edinburgh, King's Buildings, Edinburgh EH9 3FL, UK
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27
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Zajitschek F, Connallon T. Antagonistic pleiotropy in species with separate sexes, and the maintenance of genetic variation in life-history traits and fitness. Evolution 2018; 72:1306-1316. [PMID: 29667189 DOI: 10.1111/evo.13493] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 03/21/2018] [Accepted: 03/23/2018] [Indexed: 01/01/2023]
Abstract
Antagonistic pleiotropy (AP)-where alleles of a gene increase some components of fitness at a cost to others-can generate balancing selection, and contribute to the maintenance of genetic variation in fitness traits, such as survival, fecundity, fertility, and mate competition. Previous theory suggests that AP is unlikely to maintain variation unless antagonistic selection is strong, or AP alleles exhibit pronounced differences in genetic dominance between the affected traits. We show that conditions for balancing selection under AP expand under the likely scenario that the strength of selection on each fitness component differs between the sexes. Our model also predicts that the vast majority of balanced polymorphisms have sexually antagonistic effects on total fitness, despite the absence of sexual antagonism for individual fitness components. We conclude that AP polymorphisms are less difficult to maintain than predicted by prior theory, even under our conservative assumption that selection on components of fitness is universally sexually concordant. We discuss implications for the maintenance of genetic variation, and for inferences of sexual antagonism that are based on sex-specific phenotypic selection estimates-many of which are based on single fitness components.
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Affiliation(s)
- Felix Zajitschek
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia
| | - Tim Connallon
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia
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28
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Trombetta B, D'Atanasio E, Cruciani F. Patterns of Inter-Chromosomal Gene Conversion on the Male-Specific Region of the Human Y Chromosome. Front Genet 2017; 8:54. [PMID: 28515739 PMCID: PMC5413550 DOI: 10.3389/fgene.2017.00054] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 04/18/2017] [Indexed: 12/31/2022] Open
Abstract
The male-specific region of the human Y chromosome (MSY) is characterized by the lack of meiotic recombination and it has long been considered an evolutionary independent region of the human genome. In recent years, however, the idea that human MSY did not have an independent evolutionary history begun to emerge with the discovery that inter-chromosomal gene conversion (ICGC) can modulate the genetic diversity of some portions of this genomic region. Despite the study of the dynamics of this molecular mechanism in humans is still in its infancy, some peculiar features and consequences of it can be summarized. The main effect of ICGC is to increase the allelic diversity of MSY by generating a significant excess of clustered single nucleotide polymorphisms (SNPs) (defined as groups of two or more SNPs occurring in close proximity and on the same branch of the Y phylogeny). On the human MSY, 13 inter-chromosomal gene conversion hotspots (GCHs) have been identified so far, involving donor sequences mainly from the X-chromosome and, to a lesser extent, from autosomes. Most of the GCHs are evolutionary conserved and overlap with regions involved in aberrant X–Y crossing-over. This review mainly focuses on the dynamics and the current knowledge concerning the recombinational landscape of the human MSY in the form of ICGC, on how this molecular mechanism may influence the evolution of the MSY, and on how it could affect the information enclosed within a genomic region which, until recently, appeared to be an evolutionary independent unit.
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Affiliation(s)
- Beniamino Trombetta
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di RomaRome, Italy
| | - Eugenia D'Atanasio
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di RomaRome, Italy
| | - Fulvio Cruciani
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di RomaRome, Italy.,Istituto di Biologia e Patologia Molecolari, Consiglio Nazionale delle Ricerche (CNR),Rome, Italy
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29
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Abstract
Mutation generates a steady supply of genetic variation that, while occasionally useful for adaptation, is more often deleterious for fitness. Recent research has emphasized that the fitness effects of mutations often differ between the sexes, leading to important evolutionary consequences for the maintenance of genetic variation and long-term population viability. Some forms of sex-specific selection-i.e., stronger purifying selection in males than females-can help purge a population's load of female-harming mutations and promote population growth. Other scenarios-e.g., sexually antagonistic selection, in which mutations that harm females are beneficial for males-inflate genetic loads and potentially dampen population viability. Evolutionary processes of sexual antagonism and purifying selection are likely to impact the evolutionary dynamics of different loci within a genome, yet theory has mostly ignored the potential for interactions between such loci to jointly shape the evolutionary genetic basis of female and male fitness variation. Here, we show that sexually antagonistic selection at a locus tends to elevate the frequencies of deleterious alleles at tightly linked loci that evolve under purifying selection. Moreover, haplotypes that segregate for different sexually antagonistic alleles accumulate different types of deleterious mutations. Haplotypes that carry female-benefit sexually antagonistic alleles preferentially accumulate mutations that are primarily male harming, whereas male-benefit haplotypes accumulate mutations that are primarily female harming. The theory predicts that sexually antagonistic selection should shape the genomic organization of genetic variation that differentially impacts female and male fitness, and contribute to sexual dimorphism in the genetic basis of fitness variation.
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30
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Lucotte EA, Laurent R, Heyer E, Ségurel L, Toupance B. Detection of Allelic Frequency Differences between the Sexes in Humans: A Signature of Sexually Antagonistic Selection. Genome Biol Evol 2016; 8:1489-500. [PMID: 27189992 PMCID: PMC4898804 DOI: 10.1093/gbe/evw090] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Sexually antagonistic (SA) selection, a form of selection that can occur when both sexes have different fitness optima for a trait, is a major force shaping the evolution of organisms. A seminal model developed by Rice (Rice WR. 1984. Sex chromosomes and the evolution of sexual dimorphism. Evolution 38:735-742.) predicts that the X chromosome should be a hotspot for the accumulation of loci under SA selection as compared with the autosomes. Here, we propose a methodological framework designed to detect a specific signature of SA selection on viability, differences in allelic frequencies between the sexes. Applying this method on genome-wide single nucleotide polymorphism (SNP) data in human populations where no sex-specific population stratification could be detected, we show that there are overall significantly more SNPs exhibiting differences in allelic frequencies between the sexes on the X chromosome as compared with autosomes, supporting the predictions of Rice's model. This pattern is consistent across populations and is robust to correction for potential biases such as differences in linkage disequilibrium, sample size, and genotyping errors between chromosomes. Although SA selection is not the only factor resulting in allelic frequency differences between the sexes, we further show that at least part of the identified X-linked loci is caused by such a sex-specific processes.
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Affiliation(s)
- Elise A Lucotte
- Eco-Anthropologie et Ethnobiologie, UMR 7206 CNRS, MNHN, Univ Paris Diderot, Sorbonne Paris Cité, Paris, France Bioinformatics Research Centre, Aarhus University, Aarhus, Denmark
| | - Romain Laurent
- Eco-Anthropologie et Ethnobiologie, UMR 7206 CNRS, MNHN, Univ Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Evelyne Heyer
- Eco-Anthropologie et Ethnobiologie, UMR 7206 CNRS, MNHN, Univ Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Laure Ségurel
- Eco-Anthropologie et Ethnobiologie, UMR 7206 CNRS, MNHN, Univ Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Bruno Toupance
- Eco-Anthropologie et Ethnobiologie, UMR 7206 CNRS, MNHN, Univ Paris Diderot, Sorbonne Paris Cité, Paris, France
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31
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Gorelick R, Fraser D, Mansfield M, Dawson JW, Wijenayake S, Bertram SM. Abrupt shortening of bird W chromosomes in ancestral Neognathae. Biol J Linn Soc Lond 2016. [DOI: 10.1111/bij.12832] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Root Gorelick
- Department of Biology; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
- School of Mathematics & Statistics and Institute of Interdisciplinary Studies; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
| | - Danielle Fraser
- Department of Biology; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
| | - Melissa Mansfield
- Department of Biology; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
| | - Jeff W. Dawson
- Department of Biology; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
| | - Sanoji Wijenayake
- Department of Biology; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
| | - Susan M. Bertram
- Department of Biology; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
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32
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Luthringer R, Lipinska AP, Roze D, Cormier A, Macaisne N, Peters AF, Cock JM, Coelho SM. The Pseudoautosomal Regions of the U/V Sex Chromosomes of the Brown Alga Ectocarpus Exhibit Unusual Features. Mol Biol Evol 2015; 32:2973-85. [PMID: 26248564 PMCID: PMC4610043 DOI: 10.1093/molbev/msv173] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The recombining regions of sex chromosomes (pseudoautosomal regions, PARs) are predicted to exhibit unusual features due to their being genetically linked to the nonrecombining, sex-determining region. This phenomenon is expected to occur in both diploid (XY, ZW) and haploid (UV) sexual systems, with slightly different consequences for UV sexual systems because of the absence of masking during the haploid phase (when sex is expressed) and because there is no homozygous sex in these systems. Despite a considerable amount of theoretical work on PAR genetics and evolution, these genomic regions have remained poorly characterized empirically. We show here that although the PARs of the U/V sex chromosomes of the brown alga Ectocarpus recombine at a similar rate to autosomal regions of the genome, they exhibit many genomic features typical of nonrecombining regions. The PARs were enriched in clusters of genes that are preferentially, and often exclusively, expressed during the sporophyte generation of the life cycle, and many of these genes appear to have evolved since the Ectocarpales diverged from other brown algal lineages. A modeling-based approach was used to investigate possible evolutionary mechanisms underlying this enrichment in sporophyte-biased genes. Our results are consistent with the evolution of the PAR in haploid systems being influenced by differential selection pressures in males and females acting on alleles that are advantageous during the sporophyte generation of the life cycle.
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Affiliation(s)
- Rémy Luthringer
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, Roscoff, France
| | - Agnieszka P Lipinska
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, Roscoff, France
| | - Denis Roze
- UMI 3614, Evolutionary Biology and Ecology of Algae, CNRS, Sorbonne Universités, UPMC, PUCCh, UACH, Station Biologique de Roscoff, Roscoff, France
| | - Alexandre Cormier
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, Roscoff, France
| | - Nicolas Macaisne
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, Roscoff, France
| | | | - J Mark Cock
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, Roscoff, France
| | - Susana M Coelho
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, Roscoff, France
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33
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Filatov DA. Homomorphic plant sex chromosomes are coming of age. Mol Ecol 2015; 24:3217-9. [PMID: 26113024 DOI: 10.1111/mec.13268] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 06/05/2015] [Indexed: 11/30/2022]
Abstract
Sex chromosomes are a very peculiar part of the genome that have evolved independently in many groups of animals and plants (Bull ). Major research efforts have so far been focused on large heteromorphic sex chromosomes in a few animal and plant species (Chibalina & Filatov ; Zhou & Bachtrog ; Bellott et al. ; Hough et al. ; Zhou et al. ), while homomorphic (cytologically indistinguishable) sex chromosomes have largely been neglected. However, this situation is starting to change. In this issue, Geraldes et al. () describe a small (~100 kb long) sex-determining region on the homomorphic sex chromosomes of poplars (Populus trichocarpa and related species, Fig. ). All species in Populus and its sister genus Salix are dioecious, suggesting that dioecy and the sex chromosomes, if any, should be relatively old. Contrary to this expectation, Geraldes et al. () demonstrate that the sex-determining region in poplars is of very recent origin and probably evolved within the genus Populus only a few million years ago.
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Affiliation(s)
- Dmitry A Filatov
- Department of Plant Sciences, University of Oxford, South Parks Rd, Oxford, OX1 3RB, UK
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34
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Blackmon H, Demuth JP. The fragile Y hypothesis: Y chromosome aneuploidy as a selective pressure in sex chromosome and meiotic mechanism evolution. Bioessays 2015. [DOI: 10.1002/bies.201500040] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Heath Blackmon
- Department of Biology; University of Texas at Arlington; Arlington TX USA
| | - Jeffery P. Demuth
- Department of Biology; University of Texas at Arlington; Arlington TX USA
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35
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Lipinska A, Cormier A, Luthringer R, Peters AF, Corre E, Gachon CMM, Cock JM, Coelho SM. Sexual dimorphism and the evolution of sex-biased gene expression in the brown alga ectocarpus. Mol Biol Evol 2015; 32:1581-97. [PMID: 25725430 DOI: 10.1093/molbev/msv049] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Males and females often have marked phenotypic differences, and the expression of these dissimilarities invariably involves sex differences in gene expression. Sex-biased gene expression has been well characterized in animal species, where a high proportion of the genome may be differentially regulated in males and females during development. Male-biased genes tend to evolve more rapidly than female-biased genes, implying differences in the strength of the selective forces acting on the two sexes. Analyses of sex-biased gene expression have focused on organisms that exhibit separate sexes during the diploid phase of the life cycle (diploid sexual systems), but the genetic nature of the sexual system is expected to influence the evolutionary trajectories of sex-biased genes. We analyze here the patterns of sex-biased gene expression in Ectocarpus, a brown alga with haploid sex determination (dioicy) and a low level of phenotypic sexual dimorphism. In Ectocarpus, female-biased genes were found to be evolving as rapidly as male-biased genes. Moreover, genes expressed at fertility showed faster rates of evolution than genes expressed in immature gametophytes. Both male- and female-biased genes had a greater proportion of sites experiencing positive selection, suggesting that their accelerated evolution is at least partly driven by adaptive evolution. Gene duplication appears to have played a significant role in the generation of sex-biased genes in Ectocarpus, expanding previous models that propose this mechanism for the resolution of sexual antagonism in diploid systems. The patterns of sex-biased gene expression in Ectocarpus are consistent both with predicted characteristics of UV (haploid) sexual systems and with the distinctive aspects of this organism's reproductive biology.
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Affiliation(s)
- Agnieszka Lipinska
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff, France
| | - Alexandre Cormier
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff, France
| | - Rémy Luthringer
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff, France
| | | | - Erwan Corre
- Abims Platform, CNRS-UPMC, FR2424, Station Biologique de Roscoff, Roscoff, France
| | - Claire M M Gachon
- Microbial and Molecular Biology Department, Scottish Marine Institute, Scottish Association for Marine Science, Oban, United Kingdom
| | - J Mark Cock
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff, France
| | - Susana M Coelho
- Sorbonne Université, UPMC Univ Paris 06, CNRS, Algal Genetics Group, UMR 8227, Integrative Biology of Marine Models, Station Biologique de Roscoff, CS 90074, F-29688, Roscoff, France
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36
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Transition in sexual system and sex chromosome evolution in the tadpole shrimp Triops cancriformis. Heredity (Edinb) 2015; 115:37-46. [PMID: 25757406 PMCID: PMC4815504 DOI: 10.1038/hdy.2015.10] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 01/13/2015] [Accepted: 01/14/2015] [Indexed: 12/19/2022] Open
Abstract
Transitions in sexual system and reproductive mode may affect the course of sex chromosome evolution, for instance by altering the strength of sexually antagonistic selection. However, there have been few studies of sex chromosomes in systems where such transitions have been documented. The European tadpole shrimp, Triops cancriformis, has undergone a transition from dioecy to androdioecy (a sexual system where hermaphrodites and males coexist), offering an excellent opportunity to test the impact of this transition on the evolution of sex chromosomes. To identify sex-linked markers, to understand mechanisms of sex determination and to investigate differences between sexual systems, we carried out a genome-wide association study using restriction site-associated DNA sequencing (RAD-seq) of 47 males, females and hermaphrodites from one dioecious and one androdioecious population. We analysed 22.9 Gb of paired-end sequences and identified and scored >3000 high coverage novel genomic RAD markers. Presence–absence of markers, single-nucleotide polymorphism association and read depth identified 52 candidate sex-linked markers. We show that sex is genetically determined in T. cancriformis, with a ZW system conserved across dioecious and androdioecious populations and that hermaphrodites have likely evolved from females. We also show that the structure of the sex chromosomes differs strikingly, with a larger sex-linked region in the dioecious population compared with the androdioecious population.
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37
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Lappin FM, Medert CM, Hawkins KK, Mardonovich S, Wu M, Moore RC. A polymorphic pseudoautosomal boundary in the Carica papaya sex chromosomes. Mol Genet Genomics 2015; 290:1511-22. [DOI: 10.1007/s00438-015-1000-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 01/23/2015] [Indexed: 12/14/2022]
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38
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The influence of pleiotropy between viability and pollen fates on mating system evolution. Theor Popul Biol 2014; 99:7-17. [PMID: 25448089 DOI: 10.1016/j.tpb.2014.10.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Revised: 10/13/2014] [Accepted: 10/18/2014] [Indexed: 11/23/2022]
Abstract
Floral displays are functionally and genetically integrated structures, so modifications to display will likely affect multiple fitness components (pleiotropy), including pollen export and self-pollination, and therefore selfing rate. Consequently, the great diversities of floral displays and of mating systems found among angiosperms have likely co-evolved. I extend previous models of mating system evolution to determine how pleiotropy that links viability (e.g., probability of survival to reproduction) and the allocation of pollen for export and selfing affects the evolution of selfing, outcrossing, and in particular, mixed mating. I show that the outcome depends on how pollen shifts from being exported, unused, or used for selfing. Furthermore, pleiotropy that affects viability can explain observations not addressed by previous theory, including the evolution of mixed mating despite high inbreeding depression in the absence of pollen-limitation. Therefore, pleiotropy may play a key role in explaining selfing rates for such species that exhibit otherwise enigmatic mating systems.
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39
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Pokorná MJ, Kratochvíl L. What was the ancestral sex-determining mechanism in amniote vertebrates? Biol Rev Camb Philos Soc 2014; 91:1-12. [DOI: 10.1111/brv.12156] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 10/01/2014] [Accepted: 10/15/2014] [Indexed: 01/15/2023]
Affiliation(s)
- Martina Johnson Pokorná
- Department of Ecology; Faculty of Science, Charles University in Prague; Viničná 7 Praha 2 Czech Republic
- Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic; Rumburská 89 Liběchov Czech Republic
| | - Lukáš Kratochvíl
- Department of Ecology; Faculty of Science, Charles University in Prague; Viničná 7 Praha 2 Czech Republic
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40
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Smeds L, Kawakami T, Burri R, Bolivar P, Husby A, Qvarnström A, Uebbing S, Ellegren H. Genomic identification and characterization of the pseudoautosomal region in highly differentiated avian sex chromosomes. Nat Commun 2014; 5:5448. [PMID: 25378102 PMCID: PMC4272252 DOI: 10.1038/ncomms6448] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 09/30/2014] [Indexed: 02/07/2023] Open
Abstract
The molecular characteristics of the pseudoautosomal region (PAR) of sex chromosomes
remain elusive. Despite significant genome-sequencing efforts, the PAR of highly
differentiated avian sex chromosomes remains to be identified. Here we use linkage
analysis together with whole-genome re-sequencing to uncover the 630-kb PAR of an
ecological model species, the collared flycatcher. The PAR contains 22 protein-coding
genes and is GC rich. The genetic length is 64 cM in female meiosis, consistent
with an obligate crossing-over event. Recombination is concentrated to a hotspot region,
with an extreme rate of >700 cM/Mb in a 67-kb segment. We find no signatures
of sexual antagonism and propose that sexual antagonism may have limited influence on
PAR sequences when sex chromosomes are nearly fully differentiated and when a
recombination hotspot region is located close to the PAR boundary. Our results
demonstrate that a very small PAR suffices to ensure homologous recombination and proper
segregation of sex chromosomes during meiosis. The genetic basis of sex chromosome pseudoautosomal regions (PAR) in
organisms with female heterogamety is largely unknown. Smeds et al. provide the
first molecular characterization of the PAR in birds with differentiated sex chromosomes
and show a potential recombination hotspot and no evidence for strong sexual antagonism in
this region.
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Affiliation(s)
- Linnéa Smeds
- Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden
| | - Takeshi Kawakami
- Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden
| | - Reto Burri
- Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden
| | - Paulina Bolivar
- Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden
| | - Arild Husby
- 1] Department of Animal Ecology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden [2] Department of Biology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
| | - Anna Qvarnström
- Department of Animal Ecology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden
| | - Severin Uebbing
- Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden
| | - Hans Ellegren
- Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 36 Uppsala, Sweden
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41
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Connallon T, Clark AG. Balancing selection in species with separate sexes: insights from Fisher's geometric model. Genetics 2014; 197:991-1006. [PMID: 24812306 PMCID: PMC4096376 DOI: 10.1534/genetics.114.165605] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 05/06/2014] [Indexed: 01/08/2023] Open
Abstract
How common is balancing selection, and what fraction of phenotypic variance is attributable to balanced polymorphisms? Despite decades of research, answers to these questions remain elusive. Moreover, there is no clear theoretical prediction about the frequency with which balancing selection is expected to arise within a population. Here, we use an extension of Fisher's geometric model of adaptation to predict the probability of balancing selection in a population with separate sexes, wherein polymorphism is potentially maintained by two forms of balancing selection: (1) heterozygote advantage, where heterozygous individuals at a locus have higher fitness than homozygous individuals, and (2) sexually antagonistic selection (a.k.a. intralocus sexual conflict), where the fitness of each sex is maximized by different genotypes at a locus. We show that balancing selection is common under biologically plausible conditions and that sex differences in selection or sex-by-genotype effects of mutations can each increase opportunities for balancing selection. Although heterozygote advantage and sexual antagonism represent alternative mechanisms for maintaining polymorphism, they mutually exist along a balancing selection continuum that depends on population and sex-specific parameters of selection and mutation. Sexual antagonism is the dominant mode of balancing selection across most of this continuum.
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Affiliation(s)
- Tim Connallon
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
| | - Andrew G Clark
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
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42
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Trombetta B, Sellitto D, Scozzari R, Cruciani F. Inter- and intraspecies phylogenetic analyses reveal extensive X-Y gene conversion in the evolution of gametologous sequences of human sex chromosomes. Mol Biol Evol 2014; 31:2108-23. [PMID: 24817545 PMCID: PMC4104316 DOI: 10.1093/molbev/msu155] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
It has long been believed that the male-specific region of the human Y chromosome (MSY) is genetically independent from the X chromosome. This idea has been recently dismissed due to the discovery that X–Y gametologous gene conversion may occur. However, the pervasiveness of this molecular process in the evolution of sex chromosomes has yet to be exhaustively analyzed. In this study, we explored how pervasive X–Y gene conversion has been during the evolution of the youngest stratum of the human sex chromosomes. By comparing about 0.5 Mb of human–chimpanzee gametologous sequences, we identified 19 regions in which extensive gene conversion has occurred. From our analysis, two major features of these emerged: 1) Several of them are evolutionarily conserved between the two species and 2) almost all of the 19 hotspots overlap with regions where X–Y crossing-over has been previously reported to be involved in sex reversal. Furthermore, in order to explore the dynamics of X–Y gametologous conversion in recent human evolution, we resequenced these 19 hotspots in 68 widely divergent Y haplogroups and used publicly available single nucleotide polymorphism data for the X chromosome. We found that at least ten hotspots are still active in humans. Hence, the results of the interspecific analysis are consistent with the hypothesis of widespread reticulate evolution within gametologous sequences in the differentiation of hominini sex chromosomes. In turn, intraspecific analysis demonstrates that X–Y gene conversion may modulate human sex-chromosome-sequence evolution to a greater extent than previously thought.
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Affiliation(s)
- Beniamino Trombetta
- Dipartimento di Biologia e Biotecnologie "Charles Darwin," Sapienza Università di Roma, Roma, Italy
| | | | - Rosaria Scozzari
- Dipartimento di Biologia e Biotecnologie "Charles Darwin," Sapienza Università di Roma, Roma, Italy
| | - Fulvio Cruciani
- Dipartimento di Biologia e Biotecnologie "Charles Darwin," Sapienza Università di Roma, Roma, ItalyIstituto di Biologia e Patologia Molecolari, CNR, Roma, ItalyIstituto Pasteur-Fondazione Cenci Bolognetti, Sapienza Università di Roma, Roma, Italy
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