1
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Corral-Lopez A, Bloch NI, van der Bijl W, Cortazar-Chinarro M, Szorkovszky A, Kotrschal A, Darolti I, Buechel SD, Romenskyy M, Kolm N, Mank JE. Functional convergence of genomic and transcriptomic architecture underlies schooling behaviour in a live-bearing fish. Nat Ecol Evol 2024; 8:98-110. [PMID: 37985898 PMCID: PMC10781616 DOI: 10.1038/s41559-023-02249-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Accepted: 10/12/2023] [Indexed: 11/22/2023]
Abstract
The organization and coordination of fish schools provide a valuable model to investigate the genetic architecture of affiliative behaviours and dissect the mechanisms underlying social behaviours and personalities. Here we used replicate guppy selection lines that vary in schooling propensity and combine quantitative genetics with genomic and transcriptomic analyses to investigate the genetic basis of sociability phenotypes. We show that consistent with findings in collective motion patterns, experimental evolution of schooling propensity increased the sociability of female, but not male, guppies when swimming with unfamiliar conspecifics. This finding highlights a relevant link between coordinated motion and sociability for species forming fission-fusion societies in which both group size and the type of social interactions are dynamic across space and time. We further show that alignment and attraction, the two major traits forming the sociability personality axis in this species, showed heritability estimates at the upper end of the range previously described for social behaviours, with important variation across sexes. The results from both Pool-seq and RNA-seq data indicated that genes involved in neuron migration and synaptic function were instrumental in the evolution of sociability, highlighting a crucial role of glutamatergic synaptic function and calcium-dependent signalling processes in the evolution of schooling.
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Affiliation(s)
- Alberto Corral-Lopez
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada.
- Department of Zoology/Ethology, Stockholm University, Stockholm, Sweden.
- Division of Ecology and Genetics, Uppsala University, Uppsala, Sweden.
| | - Natasha I Bloch
- Department of Biomedical Engineering, University of Los Andes, Bogota, Colombia
| | - Wouter van der Bijl
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
| | - Maria Cortazar-Chinarro
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada
- MEMEG Department of Biology, Lund University, Lund, Sweden
| | - Alexander Szorkovszky
- RITMO Centre for Interdisciplinary Studies in Rhythm, Time and Motion, University of Oslo, Oslo, Norway
| | - Alexander Kotrschal
- Behavioural Ecology, Wageningen University and Research, Wageningen, the Netherlands
| | - Iulia Darolti
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Severine D Buechel
- Behavioural Ecology, Wageningen University and Research, Wageningen, the Netherlands
| | - Maksym Romenskyy
- Department of Zoology/Ethology, Stockholm University, Stockholm, Sweden
| | - Niclas Kolm
- Department of Zoology/Ethology, Stockholm University, Stockholm, Sweden
| | - Judith E Mank
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
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2
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Fong LJM, Darolti I, Metzger DCH, Morris J, Lin Y, Sandkam BA, Mank JE. Parsimony and Poeciliid Sex Chromosome Evolution. Genome Biol Evol 2023; 15:evad128. [PMID: 37670515 PMCID: PMC10480581 DOI: 10.1093/gbe/evad128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/01/2023] [Indexed: 09/07/2023] Open
Affiliation(s)
- Lydia J M Fong
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, Canada
| | - Iulia Darolti
- Department of Ecology and Evolution, University of Lausanne, Switzerland
| | - David C H Metzger
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, Canada
| | - Jake Morris
- School of Biological Sciences, University of Bristol, United Kingdom
| | - Yuying Lin
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, Canada
| | - Benjamin A Sandkam
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York, USA
| | - Judith E Mank
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, Canada
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3
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Lin Y, Darolti I, van der Bijl W, Morris J, Mank JE. Extensive variation in germline de novo mutations in Poecilia reticulata. Genome Res 2023; 33:1317-1324. [PMID: 37442578 PMCID: PMC10547258 DOI: 10.1101/gr.277936.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 07/07/2023] [Indexed: 07/15/2023]
Abstract
The rate of germline mutation is fundamental to evolutionary processes, as it generates the variation upon which selection acts. The guppy, Poecilia reticulata, is a model of rapid adaptation, however the relative contribution of standing genetic variation versus de novo mutation (DNM) to evolution in this species remains unclear. Here, we use pedigree-based approaches to quantify and characterize germline DNMs in three large guppy families. Our results suggest germline mutation rate in the guppy varies substantially across individuals and families. Most DNMs are shared across multiple siblings, suggesting they arose during early embryonic development. DNMs are randomly distributed throughout the genome, and male-biased mutation rate is low, as would be expected from the short guppy generation time. Overall, our study shows remarkable variation in germline mutation rate and provides insights into rapid evolution of guppies.
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Affiliation(s)
- Yuying Lin
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada;
| | - Iulia Darolti
- Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Wouter van der Bijl
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Jake Morris
- School of Biological Science, University of Bristol, Bristol BS8 1TQ, United Kingdom
| | - Judith E Mank
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
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4
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Darolti I, Fong LJM, Sandkam BA, Metzger DCH, Mank JE. Sex chromosome heteromorphism and the Fast-X effect in poeciliids. Mol Ecol 2023; 32:4599-4609. [PMID: 37309716 DOI: 10.1111/mec.17048] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Revised: 05/29/2023] [Accepted: 05/31/2023] [Indexed: 06/14/2023]
Abstract
Fast-X evolution has been observed in a range of heteromorphic sex chromosomes. However, it remains unclear how early in the process of sex chromosome differentiation the Fast-X effect becomes detectible. Recently, we uncovered an extreme variation in sex chromosome heteromorphism across poeciliid fish species. The common guppy, Poecilia reticulata, Endler's guppy, P. wingei, swamp guppy, P. picta and para guppy, P. parae, appear to share the same XY system and exhibit a remarkable range of heteromorphism. Species outside this group lack this sex chromosome system. We combined analyses of sequence divergence and polymorphism data across poeciliids to investigate X chromosome evolution as a function of hemizygosity and reveal the causes for Fast-X effects. Consistent with the extent of Y degeneration in each species, we detect higher rates of divergence on the X relative to autosomes, a signal of Fast-X evolution, in P. picta and P. parae, species with high levels of X hemizygosity in males. In P. reticulata, which exhibits largely homomorphic sex chromosomes and little evidence of hemizygosity, we observe no change in the rate of evolution of X-linked relative to autosomal genes. In P. wingei, the species with intermediate sex chromosome differentiation, we see an increase in the rate of nonsynonymous substitutions on the older stratum of divergence only. We also use our comparative approach to test for the time of origin of the sex chromosomes in this clade. Taken together, our study reveals an important role of hemizygosity in Fast-X evolution.
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Affiliation(s)
- Iulia Darolti
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Lydia J M Fong
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
| | - Benjamin A Sandkam
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York, USA
| | - David C H Metzger
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
| | - Judith E Mank
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
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5
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Darolti I, Mank JE. Sex-biased gene expression at single-cell resolution: cause and consequence of sexual dimorphism. Evol Lett 2023; 7:148-156. [PMID: 37251587 PMCID: PMC10210449 DOI: 10.1093/evlett/qrad013] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 03/08/2023] [Accepted: 04/06/2023] [Indexed: 05/31/2023] Open
Abstract
Gene expression differences between males and females are thought to be key for the evolution of sexual dimorphism, and sex-biased genes are often used to study the molecular footprint of sex-specific selection. However, gene expression is often measured from complex aggregations of diverse cell types, making it difficult to distinguish between sex differences in expression that are due to regulatory rewiring within similar cell types and those that are simply a consequence of developmental differences in cell-type abundance. To determine the role of regulatory versus developmental differences underlying sex-biased gene expression, we use single-cell transcriptomic data from multiple somatic and reproductive tissues of male and female guppies, a species that exhibits extensive phenotypic sexual dimorphism. Our analysis of gene expression at single-cell resolution demonstrates that nonisometric scaling between the cell populations within each tissue and heterogeneity in cell-type abundance between the sexes can influence inferred patterns of sex-biased gene expression by increasing both the false-positive and false-negative rates. Moreover, we show that, at the bulk level, the subset of sex-biased genes that are the product of sex differences in cell-type abundance can significantly confound patterns of coding-sequence evolution. Taken together, our results offer a unique insight into the effects of allometry and cellular heterogeneity on perceived patterns of sex-biased gene expression and highlight the power of single-cell RNA-sequencing in distinguishing between sex-biased genes that are the result of regulatory change and those that stem from sex differences in cell-type abundance, and hence are a consequence rather than a cause of sexual dimorphism.
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Affiliation(s)
- Iulia Darolti
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Judith E Mank
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
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6
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Fong LJM, Darolti I, Metzger DCH, Morris J, Lin Y, Sandkam BA, Mank JE. Evolutionary History of the Poecilia picta Sex Chromosomes. Genome Biol Evol 2023; 15:evad030. [PMID: 36802329 PMCID: PMC10003743 DOI: 10.1093/gbe/evad030] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 01/27/2023] [Accepted: 02/03/2023] [Indexed: 02/23/2023] Open
Abstract
The degree of divergence between the sex chromosomes is not always proportional to their age. In poeciliids, four closely related species all exhibit a male heterogametic sex chromosome system on the same linkage group, yet show a remarkable diversity in X and Y divergence. In Poecilia reticulata and P. wingei, the sex chromosomes remain homomorphic, yet P. picta and P. parae have a highly degraded Y chromosome. To test alternative theories about the origin of their sex chromosomes, we used a combination of pedigrees and RNA-seq data from P. picta families in conjunction with DNA-seq data collected from P. reticulata, P. wingei, P. parae, and P. picta. Phylogenetic clustering analysis of X and Y orthologs, identified through segregation patterns, and their orthologous sequences in closely related species demonstrates a similar time of origin for both the P. picta and P. reticulata sex chromosomes. We next used k-mer analysis to identify shared ancestral Y sequence across all four species, suggesting a single origin to the sex chromosome system in this group. Together, our results provide key insights into the origin and evolution of the poeciliid Y chromosome and illustrate that the rate of sex chromosome divergence is often highly heterogenous, even over relatively short evolutionary time frames.
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Affiliation(s)
- Lydia J M Fong
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Canada
| | - Iulia Darolti
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Canada
| | - David C H Metzger
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Canada
| | - Jake Morris
- Department of Zoology, University of Cambridge, United Kingdom
| | - Yuying Lin
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Canada
| | | | - Judith E Mank
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Canada
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7
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Darolti I, Almeida P, Wright AE, Mank JE. Comparison of methodological approaches to the study of young sex chromosomes: A case study in Poecilia. J Evol Biol 2022; 35:1646-1658. [PMID: 35506576 PMCID: PMC10084049 DOI: 10.1111/jeb.14013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 03/21/2022] [Accepted: 04/11/2022] [Indexed: 12/16/2022]
Abstract
Studies of sex chromosome systems at early stages of divergence are key to understanding the initial process and underlying causes of recombination suppression. However, identifying signatures of divergence in homomorphic sex chromosomes can be challenging due to high levels of sequence similarity between the X and the Y. Variations in methodological precision and underlying data can make all the difference between detecting subtle divergence patterns or missing them entirely. Recent efforts to test for X-Y sequence differentiation in the guppy have led to contradictory results. Here, we apply different analytical methodologies to the same data set to test for the accuracy of different approaches in identifying patterns of sex chromosome divergence in the guppy. Our comparative analysis reveals that the most substantial source of variation in the results of the different analyses lies in the reference genome used. Analyses using custom-made genome assemblies for the focal population or species successfully recover a signal of divergence across different methodological approaches. By contrast, using the distantly related Xiphophorus reference genome results in variable patterns, due to both sequence evolution and structural variations on the sex chromosomes between the guppy and Xiphophorus. Changes in mapping and filtering parameters can additionally introduce noise and obscure the signal. Our results illustrate how analytical differences can alter perceived results and we highlight best practices for the study of nascent sex chromosomes.
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Affiliation(s)
- Iulia Darolti
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
| | - Pedro Almeida
- Department of Genetics, Evolution and Environment, University College London, London, UK
| | - Alison E Wright
- Ecology and Evolutionary Biology, School of Biosciences, University of Sheffield, Sheffield, UK
| | - Judith E Mank
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada.,Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Cornwall, UK
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8
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Meunier C, Darolti I, Reimegård J, Mank JE, Johannesson H. Nuclear-specific gene expression in heterokaryons of the filamentous ascomycete Neurospora tetrasperma. Proc Biol Sci 2022; 289:20220971. [PMID: 35946150 PMCID: PMC9363985 DOI: 10.1098/rspb.2022.0971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Heterokaryosis is a system in which genetically distinct nuclei coexist within the same cytoplasm. While heterokaryosis dominates the life cycle of many fungal species, the transcriptomic changes associated with the transition from homokaryosis to heterokaryosis is not well understood. Here, we analyse gene expression profiles of homokaryons and heterokaryons from three phylogenetically and reproductively isolated lineages of the filamentous ascomycete Neurospora tetrasperma. We show that heterokaryons are transcriptionally distinct from homokaryons in the sexual stage of development, but not in the vegetative stage, suggesting that the phenotypic switch to fertility in heterokaryons is associated with major changes in gene expression. Heterokaryon expression is predominantly defined by additive effects of its two nuclear components. Furthermore, allele-specific expression analysis of heterokaryons with varying nuclear ratios show patterns of expression ratios strongly dependent on nuclear ratios in the vegetative stage. By contrast, in the sexual stage, strong deviations of expression ratios indicate a co-regulation of nuclear gene expression in all three lineages. Taken together, our results show two levels of expression control: additive effects suggest a nuclear level of expression, whereas co-regulation of gene expression indicate a heterokaryon level of control.
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Affiliation(s)
- Cécile Meunier
- Department ECOBIO, UMR CNRS 6553, Université Rennes 1, Rennes, France
| | - Iulia Darolti
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, Canada
| | - Johan Reimegård
- Department of Cell and Molecular Biology, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Judith E. Mank
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, Canada,Centre for Ecology and Conservation, University of Exeter, Penryn Campus, UK
| | - Hanna Johannesson
- Department of Organismal Biology, Uppsala University, Uppsala, Sweden,The Royal Swedish Academy of Sciences and Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
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9
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Lin Y, Darolti I, Furman BLS, Almeida P, Sandkam BA, Breden F, Wright AE, Mank JE. Gene duplication to the Y chromosome in Trinidadian Guppies. Mol Ecol 2022; 31:1853-1863. [PMID: 35060220 DOI: 10.1111/mec.16355] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Revised: 12/06/2021] [Accepted: 01/07/2022] [Indexed: 11/29/2022]
Abstract
Differences in allele frequencies at autosomal genes between males and females in a population can result from two scenarios. First, unresolved sexual conflict over survival can produce allelic differentiation between the sexes. However, given the substantial mortality costs required to produce allelic differences between males and females at each generation, it remains unclear how many loci within the genome experience significant sexual conflict over survival. Alternatively, recent studies have shown that similarity between autosomal and Y sequences can create perceived allelic differences between the sexes. However, Y duplications are most likely in species with large non-recombining regions, in part because they simply represent larger targets for duplications. We assessed the genomes of 120 wild-caught guppies, which experience extensive predation- and pathogen-induced mortality and have a relatively small ancestral Y chromosome. We identified seven autosomal genes that show allelic differences between male and female adults. Five of these genes show clear evidence of whole or partial gene duplication between the Y chromosome and the autosomes. The remaining two genes show evidence of partial homology to the Y. Overall, our findings suggest that the guppy genome experiences a very low level of unresolved sexual conflict over survival, and instead the Y chromosome, despite its small ancestral size and recent origin, may nonetheless accumulate genes with male-specific functions.
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Affiliation(s)
- Yuying Lin
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Canada
| | - Iulia Darolti
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Canada
| | - Benjamin L S Furman
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Canada
| | - Pedro Almeida
- Department of Genetics, Evolution and Environment, University College London, United Kingdom
| | - Benjamin A Sandkam
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Canada
| | - Felix Breden
- Department of Biological Sciences, Simon Fraser University, Canada
| | - Alison E Wright
- Ecology and Evolutionary Biology, School of Biosciences, University of Sheffield
| | - Judith E Mank
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Canada.,Biosciences, University of Exeter, Penryn Campus, United Kingdom
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10
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Darolti I, Mank JE. A bioinformatic toolkit to simultaneously identify sex and sex-linked regions. Mol Ecol Resour 2021; 22:455-457. [PMID: 34662503 DOI: 10.1111/1755-0998.13530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Accepted: 10/11/2021] [Indexed: 11/29/2022]
Abstract
Sex chromosomes are strange things, and often exhibit unusual patterns of diversity, rates of evolution, and gene regulation (Bachtrog et al., 2011, Mank, 2013). These unique features mean that although sex chromosomes are often a relatively small proportion of the genome, they are best identified and assessed separately from the autosomal majority when carrying out genomic analyses. However, identifying and partitioning genomic regions into sex-linked and autosomal in non-model species can often be quite difficult. In this issue of Molecular Ecology Resources, Nursyifa et al. (2021) provide a useful method that combines sequencing depth information with clustering models to assign sex to samples at the same time as identifying sex-linked scaffolds. This method gives robust results even with more challenging or low-quality data, and thus is particularly promising in studies of non-model organisms.
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Affiliation(s)
- Iulia Darolti
- Department of Zoology & Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
| | - Judith E Mank
- Department of Zoology & Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada.,Centre for Ecology and Conservation, University of Exeter, Penryn, UK
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11
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Abstract
The loss of recombination triggers divergence between the sex chromosomes and promotes degeneration of the sex-limited chromosome. Several livebearers within the genus Poecilia share a male-heterogametic sex chromosome system that is roughly 20 Myr old, with extreme variation in the degree of Y chromosome divergence. In Poecilia picta, the Y is highly degenerate and associated with complete X chromosome dosage compensation. In contrast, although recombination is restricted across almost the entire length of the sex chromosomes in Poecilia reticulata and Poecilia wingei, divergence between the X chromosome and the Y chromosome is very low. This clade therefore offers a unique opportunity to study the forces that accelerate or hinder sex chromosome divergence. We used RNA-seq data from multiple families of both P. reticulata and P. wingei, the species with low levels of sex chromosome divergence, to differentiate X and Y coding sequences based on sex-limited SNP inheritance. Phylogenetic tree analyses reveal that occasional recombination has persisted between the sex chromosomes for much of their length, as X- and Y-linked sequences cluster by species instead of by gametolog. This incomplete recombination suppression maintains the extensive homomorphy observed in these systems. In addition, we see differences between the previously identified strata in the phylogenetic clustering of X–Y orthologs, with those that cluster by chromosome located in the older stratum, the region previously associated with the sex-determining locus. However, recombination arrest appears to have expanded throughout the sex chromosomes more gradually instead of through a stepwise process associated with inversions.
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Affiliation(s)
- Iulia Darolti
- Biodiversity Research Centre and Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Alison E Wright
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, United Kingdom
| | - Judith E Mank
- Biodiversity Research Centre and Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
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12
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Abstract
Dosage compensation balances gene expression between the sexes in systems with diverged heterogametic sex chromosomes. Theory predicts that dosage compensation should rapidly evolve in tandem with the divergence of sex chromosomes to prevent the deleterious effects of dosage imbalances that occur as a result of sex chromosome divergence. Examples of complete dosage compensation, where gene expression of the entire sex chromosome is compensated, are rare, and have only been found in relatively ancient sex chromosome systems. Consequently, very little is known about the evolutionary dynamics of complete dosage compensation systems. Within the family Poeciliidae the subgenus Lebistes share the same sex chromosome system which originated 18.48–26.08 Ma. In Poecilia reticulata and P. wingei, the Y chromosome has been largely maintained, whereas the Y in the closely related species P. picta and P. parae has rapidly degraded. We recently found P. picta to be the first example of complete dosage compensation in a fish. Here, we show that P. parae also has complete dosage compensation, thus complete dosage compensation likely evolved in the short (∼3.7 Myr) interval after the split of the ancestor of these two species from P. reticulata, but before they diverged from each other. These data suggest that novel dosage compensation mechanisms can evolve rapidly, thus supporting the longstanding theoretical prediction that such mechanisms arise in tandem with rapidly diverging sex chromosomes.
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Affiliation(s)
- David C H Metzger
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Canada
| | - Benjamin A Sandkam
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Canada
| | - Iulia Darolti
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Canada
| | - Judith E Mank
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Canada.,Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Cornwall, United Kingdom
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13
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Abstract
The guppy sex chromosomes show an extraordinary diversity in divergence across populations and closely related species. In order to understand the dynamics of the guppy Y chromosome, we used linked-read sequencing to assess Y chromosome evolution and diversity across upstream and downstream population pairs that vary in predator and food abundance in three replicate watersheds. Based on our population-specific genome assemblies, we first confirmed and extended earlier reports of two strata on the guppy sex chromosomes. Stratum I shows significant accumulation of male-specific sequence, consistent with Y divergence, and predates the colonization of Trinidad. In contrast, Stratum II shows divergence from the X, but no Y-specific sequence, and this divergence is greater in three replicate upstream populations compared with their downstream pair. Despite longstanding assumptions that sex chromosome recombination suppression is achieved through inversions, we find no evidence of inversions associated with either Stratum I or Stratum II. Instead, we observe a remarkable diversity in Y chromosome haplotypes within each population, even in the ancestral Stratum I. This diversity is likely due to gradual mechanisms of recombination suppression, which, unlike an inversion, allow for the maintenance of multiple haplotypes. In addition, we show that this Y diversity is dominated by low-frequency haplotypes segregating in the population, suggesting a link between haplotype diversity and female preference for rare Y-linked color variation. Our results reveal the complex interplay between recombination suppression and Y chromosome divergence at the earliest stages of sex chromosome divergence.
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Affiliation(s)
- Pedro Almeida
- Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Benjamin A Sandkam
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Jake Morris
- Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Iulia Darolti
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Felix Breden
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
| | - Judith E Mank
- Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
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14
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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15
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Furman BLS, Metzger DCH, Darolti I, Wright AE, Sandkam BA, Almeida P, Shu JJ, Mank JE. Sex Chromosome Evolution: So Many Exceptions to the Rules. Genome Biol Evol 2020; 12:750-763. [PMID: 32315410 PMCID: PMC7268786 DOI: 10.1093/gbe/evaa081] [Citation(s) in RCA: 98] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/14/2020] [Indexed: 01/10/2023] Open
Abstract
Genomic analysis of many nonmodel species has uncovered an incredible diversity of sex chromosome systems, making it possible to empirically test the rich body of evolutionary theory that describes each stage of sex chromosome evolution. Classic theory predicts that sex chromosomes originate from a pair of homologous autosomes and recombination between them is suppressed via inversions to resolve sexual conflict. The resulting degradation of the Y chromosome gene content creates the need for dosage compensation in the heterogametic sex. Sex chromosome theory also implies a linear process, starting from sex chromosome origin and progressing to heteromorphism. Despite many convergent genomic patterns exhibited by independently evolved sex chromosome systems, and many case studies supporting these theoretical predictions, emerging data provide numerous interesting exceptions to these long-standing theories, and suggest that the remarkable diversity of sex chromosomes is matched by a similar diversity in their evolution. For example, it is clear that sex chromosome pairs are not always derived from homologous autosomes. In addition, both the cause and the mechanism of recombination suppression between sex chromosome pairs remain unclear, and it may be that the spread of recombination suppression is a more gradual process than previously thought. It is also clear that dosage compensation can be achieved in many ways, and displays a range of efficacy in different systems. Finally, the remarkable turnover of sex chromosomes in many systems, as well as variation in the rate of sex chromosome divergence, suggest that assumptions about the inevitable linearity of sex chromosome evolution are not always empirically supported, and the drivers of the birth-death cycle of sex chromosome evolution remain to be elucidated. Here, we concentrate on how the diversity in sex chromosomes across taxa highlights an equal diversity in each stage of sex chromosome evolution.
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Affiliation(s)
- Benjamin L S Furman
- Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - David C H Metzger
- Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Iulia Darolti
- Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Alison E Wright
- Department of Animal and Plant Sciences, University of Sheffield, United Kingdom
| | - Benjamin A Sandkam
- Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Pedro Almeida
- Department of Genetics, Evolution and Environment, University College London, United Kingdom
| | - Jacelyn J Shu
- Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Judith E Mank
- Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Genetics, Evolution and Environment, University College London, United Kingdom
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16
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Farré M, Li Q, Darolti I, Zhou Y, Damas J, Proskuryakova AA, Kulemzina AI, Chemnick LG, Kim J, Ryder OA, Ma J, Graphodatsky AS, Zhang G, Larkin DM, Lewin HA. An integrated chromosome-scale genome assembly of the Masai giraffe (Giraffa camelopardalis tippelskirchi). Gigascience 2020; 8:5542321. [PMID: 31367745 PMCID: PMC6669057 DOI: 10.1093/gigascience/giz090] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Revised: 06/12/2019] [Accepted: 07/09/2019] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The Masai giraffe (Giraffa camelopardalis tippelskirchi) is the largest-bodied giraffe and the world's tallest terrestrial animal. With its extreme size and height, the giraffe's unique anatomical and physiological adaptations have long been of interest to diverse research fields. Giraffes are also critical to ecosystems of sub-Saharan Africa, with their long neck serving as a conduit to food sources not shared by other herbivores. Although the genome of a Masai giraffe has been sequenced, the assembly was highly fragmented and suboptimal for genome analysis. Herein we report an improved giraffe genome assembly to facilitate evolutionary analysis of the giraffe and other ruminant genomes. FINDINGS Using SOAPdenovo2 and 170 Gbp of Illumina paired-end and mate-pair reads, we generated a 2.6-Gbp male Masai giraffe genome assembly, with a scaffold N50 of 3 Mbp. The incorporation of 114.6 Gbp of Chicago library sequencing data resulted in a HiRise SOAPdenovo + Chicago assembly with an N50 of 48 Mbp and containing 95% of expected genes according to BUSCO analysis. Using the Reference-Assisted Chromosome Assembly tool, we were able to order and orient scaffolds into 42 predicted chromosome fragments (PCFs). Using fluorescence in situ hybridization, we placed 153 cattle bacterial artificial chromosomes onto giraffe metaphase spreads to assess and assign the PCFs on 14 giraffe autosomes and the X chromosome resulting in the final assembly with an N50 of 177.94 Mbp. In this assembly, 21,621 protein-coding genes were identified using both de novo and homology-based predictions. CONCLUSIONS We have produced the first chromosome-scale genome assembly for a Giraffidae species. This assembly provides a valuable resource for the study of artiodactyl evolution and for understanding the molecular basis of the unique adaptive traits of giraffes. In addition, the assembly will provide a powerful resource to assist conservation efforts of Masai giraffe, whose population size has declined by 52% in recent years.
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Affiliation(s)
- Marta Farré
- Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London NW1 0TU, UK.,School of Biosciences, University of Kent, Canterbury CT2 7NJ, UK
| | - Qiye Li
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China.,China National Genebank, BGI-Shenzhen, Shenzhen 518083, China
| | - Iulia Darolti
- Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London NW1 0TU, UK.,Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK
| | - Yang Zhou
- Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK.,Centre for Social Evolution, Department of Biology, Universitetsparken 15, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Joana Damas
- Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London NW1 0TU, UK.,The Genome Center, University of California, Davis, CA 95616, USA
| | - Anastasia A Proskuryakova
- Institute of Molecular and Cellular Biology, SB RAS, Novosibirsk 630090, Russia.,Novosibirsk State University, Novosibirsk 630090, Russia
| | | | - Leona G Chemnick
- San Diego Institute for Conservation Research, San Diego Zoo Global, Escondido, CA, USA
| | - Jaebum Kim
- Department of Biomedical Science and Engineering, Konkuk University, Seoul 05029, South Korea
| | - Oliver A Ryder
- San Diego Institute for Conservation Research, San Diego Zoo Global, Escondido, CA, USA
| | - Jian Ma
- Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Alexander S Graphodatsky
- Institute of Molecular and Cellular Biology, SB RAS, Novosibirsk 630090, Russia.,Novosibirsk State University, Novosibirsk 630090, Russia
| | - Guoije Zhang
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China.,China National Genebank, BGI-Shenzhen, Shenzhen 518083, China.,Centre for Social Evolution, Department of Biology, Universitetsparken 15, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Denis M Larkin
- Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London NW1 0TU, UK.,The Federal Research Center Institute of Cytology and Genetics, The Siberian Branch of the Russian Academy of Sciences (ICG SB RAS), Novosibirsk 630090, Russia
| | - Harris A Lewin
- The Genome Center, University of California, Davis, CA 95616, USA.,Department of Evolution and Ecology, College of Biological Sciences, and the Department of Reproduction and Population Health, School of Veterinary Medicine, University of California, Davis, CA 95616, USA
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17
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Wright AE, Darolti I, Bloch NI, Oostra V, Sandkam BA, Buechel SD, Kolm N, Breden F, Vicoso B, Mank JE. On the power to detect rare recombination events. Proc Natl Acad Sci U S A 2019; 116:12607-12608. [PMID: 31213531 PMCID: PMC6601268 DOI: 10.1073/pnas.1905555116] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Alison E Wright
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, United Kingdom;
| | - Iulia Darolti
- Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, United Kingdom
| | - Natasha I Bloch
- Department of Biomedical Engineering, University of Los Andes, Bogotá 111711, Colombia
| | - Vicencio Oostra
- Research Centre for Ecological Change, University of Helsinki, Helsinki FI-00014, Finland
| | - Benjamin A Sandkam
- Department of Zoology, University of British Columbia, Vancouver V6T 1Z4, Canada
| | - Séverine D Buechel
- Department of Zoology, Stockholm University, Stockholm SE-106 91, Sweden
| | - Niclas Kolm
- Department of Zoology, Stockholm University, Stockholm SE-106 91, Sweden
| | - Felix Breden
- Department of Biological Sciences, Simon Fraser University, Burnaby V5A 1S6, Canada
| | - Beatriz Vicoso
- Institute of Science and Technology Austria, 3400 Klosterneuburg, Austria
| | - Judith E Mank
- Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, United Kingdom
- Department of Zoology, University of British Columbia, Vancouver V6T 1Z4, Canada
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18
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Morris J, Darolti I, Bloch NI, Wright AE, Mank JE. Shared and Species-Specific Patterns of Nascent Y Chromosome Evolution in Two Guppy Species. Genes (Basel) 2018; 9:E238. [PMID: 29751570 PMCID: PMC5977178 DOI: 10.3390/genes9050238] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 04/20/2018] [Accepted: 04/26/2018] [Indexed: 11/22/2022] Open
Abstract
Sex chromosomes form once recombination is halted around the sex-determining locus between a homologous pair of chromosomes, resulting in a male-limited Y chromosome. We recently characterized the nascent sex chromosome system in the Trinidadian guppy (Poeciliareticulata). The guppy Y is one of the youngest animal sex chromosomes yet identified, and therefore offers a unique window into the early evolutionary forces shaping sex chromosome formation, particularly the rate of accumulation of repetitive elements and Y-specific sequence. We used comparisons between male and female genomes in P. reticulata and its sister species, Endler’s guppy (P. wingei), which share an ancestral sex chromosome, to identify male-specific sequences and to characterize the degree of differentiation between the X and Y chromosomes. We identified male-specific sequence shared between P. reticulata and P. wingei consistent with a small ancestral non-recombining region. Our assembly of this Y-specific sequence shows substantial homology to the X chromosome, and appears to be significantly enriched for genes implicated in pigmentation. We also found two plausible candidates that may be involved in sex determination. Furthermore, we found that the P. wingei Y chromosome exhibits a greater signature of repetitive element accumulation than the P. reticulata Y chromosome. This suggests that Y chromosome divergence does not necessarily correlate with the time since recombination suppression. Overall, our results reveal the early stages of Y chromosome divergence in the guppy.
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Affiliation(s)
- Jake Morris
- Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK.
| | - Iulia Darolti
- Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK.
| | - Natasha I Bloch
- Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK.
| | - Alison E Wright
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
| | - Judith E Mank
- Department of Genetics, Evolution and Environment, University College London, London WC1E 6BT, UK.
- Department of Organismal Biology, Uppsala University, 752 36 Uppsala, Sweden.
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19
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Darolti I, Wright AE, Pucholt P, Berlin S, Mank JE. Slow evolution of sex-biased genes in the reproductive tissue of the dioecious plant Salix viminalis. Mol Ecol 2018; 27:694-708. [PMID: 29274186 PMCID: PMC5901004 DOI: 10.1111/mec.14466] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 11/21/2017] [Accepted: 11/28/2017] [Indexed: 12/13/2022]
Abstract
The relative rate of evolution for sex‐biased genes has often been used as a measure of the strength of sex‐specific selection. In contrast to studies in a wide variety of animals, far less is known about the molecular evolution of sex‐biased genes in plants, particularly in dioecious angiosperms. Here, we investigate the gene expression patterns and evolution of sex‐biased genes in the dioecious plant Salix viminalis. We observe lower rates of sequence evolution for male‐biased genes expressed in the reproductive tissue compared to unbiased and female‐biased genes. These results could be partially explained by the lower codon usage bias for male‐biased genes leading to elevated rates of synonymous substitutions compared to unbiased genes. However, the stronger haploid selection in the reproductive tissue of plants, together with pollen competition, would also lead to higher levels of purifying selection acting to remove deleterious variation. Future work should focus on the differential evolution of haploid‐ and diploid‐specific genes to understand the selective dynamics acting on these loci.
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Affiliation(s)
- Iulia Darolti
- Department of Genetics, Evolution and Environment, University College London, London, UK
| | - Alison E Wright
- Department of Genetics, Evolution and Environment, University College London, London, UK.,Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK
| | - Pascal Pucholt
- Department of Plant Biology, Linnean Centre for Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden.,Array and Analysis Facility, Department of Medical Science, Uppsala University, Uppsala, Sweden
| | - Sofia Berlin
- Department of Plant Biology, Linnean Centre for Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Judith E Mank
- Department of Genetics, Evolution and Environment, University College London, London, UK.,Department of Organismal Biology, Uppsala University, Uppsala, Sweden
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20
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Wright AE, Darolti I, Bloch NI, Oostra V, Sandkam B, Buechel SD, Kolm N, Breden F, Vicoso B, Mank JE. Convergent recombination suppression suggests role of sexual selection in guppy sex chromosome formation. Nat Commun 2017; 8:14251. [PMID: 28139647 PMCID: PMC5290318 DOI: 10.1038/ncomms14251] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 12/13/2016] [Indexed: 01/19/2023] Open
Abstract
Sex chromosomes evolve once recombination is halted between a homologous pair of chromosomes. The dominant model of sex chromosome evolution posits that recombination is suppressed between emerging X and Y chromosomes in order to resolve sexual conflict. Here we test this model using whole genome and transcriptome resequencing data in the guppy, a model for sexual selection with many Y-linked colour traits. We show that although the nascent Y chromosome encompasses nearly half of the linkage group, there has been no perceptible degradation of Y chromosome gene content or activity. Using replicate wild populations with differing levels of sexually antagonistic selection for colour, we also show that sexual selection leads to greater expansion of the non-recombining region and increased Y chromosome divergence. These results provide empirical support for longstanding models of sex chromosome catalysis, and suggest an important role for sexual selection and sexual conflict in genome evolution.
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Affiliation(s)
- Alison E. Wright
- Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
| | - Iulia Darolti
- Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
| | - Natasha I. Bloch
- Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
| | - Vicencio Oostra
- Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
| | - Ben Sandkam
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6
| | - Severine D. Buechel
- Department of Zoology, Stockholm University, Svante Arrheniusväg 18 B, Stockholm 106 91, Sweden
| | - Niclas Kolm
- Department of Zoology, Stockholm University, Svante Arrheniusväg 18 B, Stockholm 106 91, Sweden
| | - Felix Breden
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6
| | - Beatriz Vicoso
- Institute of Science and Technology, Am Campus 1A, Klosterneuburg 3400, Austria
| | - Judith E. Mank
- Department of Genetics, Evolution and Environment, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
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