1
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Jay P, Jeffries D, Hartmann FE, Véber A, Giraud T. Why do sex chromosomes progressively lose recombination? Trends Genet 2024:S0168-9525(24)00067-2. [PMID: 38677904 DOI: 10.1016/j.tig.2024.03.005] [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: 10/17/2023] [Revised: 03/18/2024] [Accepted: 03/19/2024] [Indexed: 04/29/2024]
Abstract
Progressive recombination loss is a common feature of sex chromosomes. Yet, the evolutionary drivers of this phenomenon remain a mystery. For decades, differences in trait optima between sexes (sexual antagonism) have been the favoured hypothesis, but convincing evidence is lacking. Recent years have seen a surge of alternative hypotheses to explain progressive extensions and maintenance of recombination suppression: neutral accumulation of sequence divergence, selection of nonrecombining fragments with fewer deleterious mutations than average, sheltering of recessive deleterious mutations by linkage to heterozygous alleles, early evolution of dosage compensation, and constraints on recombination restoration. Here, we explain these recent hypotheses and dissect their assumptions, mechanisms, and predictions. We also review empirical studies that have brought support to the various hypotheses.
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Affiliation(s)
- Paul Jay
- Center for GeoGenetics, University of Copenhagen, Copenhagen, Denmark; Université Paris-Saclay, CNRS, AgroParisTech, Laboratoire Ecologie Systématique et Evolution, UMR 8079, Bâtiment 680, 12 route RD128, 91190 Gif-sur-Yvette, France.
| | - Daniel Jeffries
- Division of Evolutionary Ecology, Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland
| | - Fanny E Hartmann
- Université Paris-Saclay, CNRS, AgroParisTech, Laboratoire Ecologie Systématique et Evolution, UMR 8079, Bâtiment 680, 12 route RD128, 91190 Gif-sur-Yvette, France
| | - Amandine Véber
- Université Paris Cité, CNRS, MAP5, F-75006 Paris, France
| | - Tatiana Giraud
- Université Paris-Saclay, CNRS, AgroParisTech, Laboratoire Ecologie Systématique et Evolution, UMR 8079, Bâtiment 680, 12 route RD128, 91190 Gif-sur-Yvette, France
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2
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Wong ELY, Filatov DA. Pericentromeric recombination suppression and the 'large X effect' in plants. Sci Rep 2023; 13:21682. [PMID: 38066067 PMCID: PMC10709461 DOI: 10.1038/s41598-023-48870-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 11/29/2023] [Indexed: 12/18/2023] Open
Abstract
X chromosome was reported to be a major contributor to isolation between closely related species-the 'large X' effect (LXE). The causes of LXE are not clear, but the leading theory is that it is caused by recessive species incompatibilities exposed in the phenotype due to the hemizygosity of X-linked genes in the heterogametic sex. However, the LXE was also reported in species with relatively recently evolved sex chromosomes where Y chromosome is not completely degenerate and X-linked genes are not hemizygous, such as the plant Silene latifolia. Recent genome sequencing and detailed genetic mapping in this species revealed a massive (> 330 Mb) non- or rarely-recombining pericentromeric region on the X chromosome (Xpr) that comprises ~ 90% of the chromosome and over 13% of the entire genome. If any of the Xpr genes are involved in species incompatibilities, this would oppose interspecific gene flow for other genes tightly linked in the Xpr. Here we test the hypothesis that the previously reported LXE in S. latifolia is caused by the lack of recombination on most of the X chromosome. Based on genome-wide analysis of DNA polymorphism and gene expression in S. latifolia and its close cross-compatible relative S. dioica, we report that the rarely-recombining regions represent a significant barrier for interspecific gene flow. We found little evidence for any additional factors contributing to the LXE, suggesting that extensive pericentromeric recombination suppression on the X-chromosome is the major if not the only cause of the LXE in S. latifolia and S. dioica.
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Affiliation(s)
- Edgar L Y Wong
- Department of Biology, University of Oxford, Oxford, UK
- Senckenberg Biodiversity and Climate Research Centre, Frankfurt am Main, Germany
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3
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Jay P, Tezenas E, Véber A, Giraud T. Sheltering of deleterious mutations explains the stepwise extension of recombination suppression on sex chromosomes and other supergenes. PLoS Biol 2022; 20:e3001698. [PMID: 35853091 PMCID: PMC9295944 DOI: 10.1371/journal.pbio.3001698] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 06/03/2022] [Indexed: 12/19/2022] Open
Abstract
Many organisms have sex chromosomes with large nonrecombining regions that have expanded stepwise, generating "evolutionary strata" of differentiation. The reasons for this remain poorly understood, but the principal hypotheses proposed to date are based on antagonistic selection due to differences between sexes. However, it has proved difficult to obtain empirical evidence of a role for sexually antagonistic selection in extending recombination suppression, and antagonistic selection has been shown to be unlikely to account for the evolutionary strata observed on fungal mating-type chromosomes. We show here, by mathematical modeling and stochastic simulation, that recombination suppression on sex chromosomes and around supergenes can expand under a wide range of parameter values simply because it shelters recessive deleterious mutations, which are ubiquitous in genomes. Permanently heterozygous alleles, such as the male-determining allele in XY systems, protect linked chromosomal inversions against the expression of their recessive mutation load, leading to the successive accumulation of inversions around these alleles without antagonistic selection. Similar results were obtained with models assuming recombination-suppressing mechanisms other than chromosomal inversions and for supergenes other than sex chromosomes, including those without XY-like asymmetry, such as fungal mating-type chromosomes. However, inversions capturing a permanently heterozygous allele were found to be less likely to spread when the mutation load segregating in populations was lower (e.g., under large effective population sizes or low mutation rates). This may explain why sex chromosomes remain homomorphic in some organisms but are highly divergent in others. Here, we model a simple and testable hypothesis explaining the stepwise extensions of recombination suppression on sex chromosomes, mating-type chromosomes, and supergenes in general.
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Affiliation(s)
- Paul Jay
- Université Paris-Saclay, CNRS, AgroParisTech, Ecologie Systématique et Evolution, 91190, Gif-sur-Yvette, France
- * E-mail:
| | - Emilie Tezenas
- Université Paris-Saclay, CNRS, AgroParisTech, Ecologie Systématique et Evolution, 91190, Gif-sur-Yvette, France
- Univ. Lille, CNRS, UMR 8198 –Evo-Eco-Paleo, F-59000 Lille, France
- Université Paris Cité, CNRS, MAP 5, F-75006 Paris, France
| | - Amandine Véber
- Université Paris Cité, CNRS, MAP 5, F-75006 Paris, France
| | - Tatiana Giraud
- Université Paris-Saclay, CNRS, AgroParisTech, Ecologie Systématique et Evolution, 91190, Gif-sur-Yvette, France
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4
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Cascales J, Acevedo RM, Paiva DI, Gottlieb AM. Differential DNA methylation and gene expression during development of reproductive and vegetative organs in Ilex species. JOURNAL OF PLANT RESEARCH 2021; 134:559-575. [PMID: 33759060 DOI: 10.1007/s10265-021-01279-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 03/05/2021] [Indexed: 06/12/2023]
Abstract
Differential epigenetic (DNA cytosine methylation) and gene expression patterns were investigated in reproductive and vegetative organs from Ilex paraguariensis and I. dumosa, at distinct developmental stages. We aimed at contributing towards elucidating major molecular changes underlying the sexual differentiation processes which, in these dioecious species, are completely unknown. Simultaneously, as a first step towards the development of an early sexing system, we searched for promising molecular markers. This was assessed through Methylation Sensitive Amplified Polymorphism (MSAP) and Amplified Fragment Length Polymorphism on cDNA (cDNA-AFLP) techniques, applying discriminant multivariate analyses, and bioinformatic characterization of differential fragments. A significant positive correlation was found between epigenetic and indirect 'genetic' information for both species, indicating influence of the genetic background on the epigenetic variation. Higher epigenetic than genetic diversities were estimated. Our outcomes showed up to 1.86 times more representation of mCG subepiloci than mCCG in all organs sampled. Along the maturing stages of floral buds, the frequency of mCG evidenced an incremental trend, whereas mCCG and unmethylated conditions showed opposite tendencies. Reproductive and vegetative samples tended to cluster apart based on epigenetic patterns; at gene expression level, organs exhibited clear-cut distinctive patterns, nonetheless profiles of young leaves and floral primordia resemble. Epigenetic and expression data allowed discrimination of I. dumosa´s samples according to the gender of the donor; more elusive patterns were observed for I. paraguariensis. In total, 102 differentially methylated and expressed fragments were characterized bioinformatically. Forty-three were annotated in various functional categories; four candidate markers were validated through qPCR, finding statistical differences among organs but not among sexes. The methylation condition of epilocus C13m33 appears as indicative of gender in both species. Thirty-three organ-specific and 34 gender-specific methylated markers were discriminated and deserve further research, particularly those expressed in leaves. Our study contributes concrete candidate markers with potential for practical application.
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Affiliation(s)
- Jimena Cascales
- Laboratorio de Citogenética y Evolución, Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Instituto de Ecología, Genética y Evolución de Buenos Aires (IEGEBA, CONICET-UBA), Universidad de Buenos Aires, Intendente Güiraldes 2160, Pabellón II, Ciudad Universitaria, C1428EHA, Ciudad Autónoma de Buenos Aires, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, Ciudad Autónoma de Buenos Aires, C1425FQB, Argentina
| | - Raúl Maximiliano Acevedo
- Laboratorio de Biotecnología Aplicada y Genómica Funcional, Facultad de Ciencias Agrarias, Instituto de Botánica del Nordeste (IBONE, UNNE-CONICET), Universidad Nacional del Nordeste, Sargento Juan Bautista Cabral 2131, Corrientes, W3402BKG, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, Ciudad Autónoma de Buenos Aires, C1425FQB, Argentina
| | - Daniela Ivana Paiva
- Instituto Nacional de Tecnología Agropecuaria, Estación Experimental Agropecuaria Montecarlo (INTA EEA Montecarlo), Av. El Libertador 2472, Misiones, N3384, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, Ciudad Autónoma de Buenos Aires, C1425FQB, Argentina
| | - Alexandra Marina Gottlieb
- Laboratorio de Citogenética y Evolución, Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Instituto de Ecología, Genética y Evolución de Buenos Aires (IEGEBA, CONICET-UBA), Universidad de Buenos Aires, Intendente Güiraldes 2160, Pabellón II, Ciudad Universitaria, C1428EHA, Ciudad Autónoma de Buenos Aires, Argentina.
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2290, Ciudad Autónoma de Buenos Aires, C1425FQB, Argentina.
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5
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Almeida P, Proux-Wera E, Churcher A, Soler L, Dainat J, Pucholt P, Nordlund J, Martin T, Rönnberg-Wästljung AC, Nystedt B, Berlin S, Mank JE. Genome assembly of the basket willow, Salix viminalis, reveals earliest stages of sex chromosome expansion. BMC Biol 2020; 18:78. [PMID: 32605573 PMCID: PMC7329446 DOI: 10.1186/s12915-020-00808-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 06/11/2020] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Sex chromosomes have evolved independently multiple times in eukaryotes and are therefore considered a prime example of convergent genome evolution. Sex chromosomes are known to emerge after recombination is halted between a homologous pair of chromosomes, and this leads to a range of non-adaptive modifications causing gradual degeneration and gene loss on the sex-limited chromosome. However, the proximal causes of recombination suppression and the pace at which degeneration subsequently occurs remain unclear. RESULTS Here, we use long- and short-read single-molecule sequencing approaches to assemble and annotate a draft genome of the basket willow, Salix viminalis, a species with a female heterogametic system at the earliest stages of sex chromosome emergence. Our single-molecule approach allowed us to phase the emerging Z and W haplotypes in a female, and we detected very low levels of Z/W single-nucleotide divergence in the non-recombining region. Linked-read sequencing of the same female and an additional male (ZZ) revealed the presence of two evolutionary strata supported by both divergence between the Z and W haplotypes and by haplotype phylogenetic trees. Gene order is still largely conserved between the Z and W homologs, although the W-linked region contains genes involved in cytokinin signaling regulation that are not syntenic with the Z homolog. Furthermore, we find no support across multiple lines of evidence for inversions, which have long been assumed to halt recombination between the sex chromosomes. CONCLUSIONS Our data suggest that selection against recombination is a more gradual process at the earliest stages of sex chromosome formation than would be expected from an inversion and may result instead from the accumulation of transposable elements. Our results present a cohesive understanding of the earliest genomic consequences of recombination suppression as well as valuable insights into the initial stages of sex chromosome formation and regulation of sex differentiation.
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Affiliation(s)
- Pedro Almeida
- Department of Genetics, Evolution & Environment, University College London, London, UK.
| | - Estelle Proux-Wera
- Department of Biochemistry and Biophysics, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Stockholm University, Stockholm, Sweden
| | - Allison Churcher
- Department of Molecular Biology, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Umeå University, Umeå, Sweden
| | - Lucile Soler
- Department of Medical Biochemistry and Microbiology, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Jacques Dainat
- Department of Medical Biochemistry and Microbiology, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Pascal Pucholt
- Department of Medical Sciences, Section of Rheumatology, Uppsala University, Uppsala, Sweden
- Department of Plant Biology, Uppsala BioCenter, Linnean Centre for Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Jessica Nordlund
- Department of Medical Sciences, National Genomics Infrastructure, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Tom Martin
- Department of Medical Sciences, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Ann-Christin Rönnberg-Wästljung
- Department of Plant Biology, Uppsala BioCenter, Linnean Centre for Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Björn Nystedt
- Department of Cell and Molecular Biology, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Sofia Berlin
- Department of Plant Biology, Uppsala BioCenter, Linnean Centre for Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Judith E Mank
- Department of Genetics, Evolution & Environment, University College London, London, UK
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, Canada
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6
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Almeida P, Proux-Wera E, Churcher A, Soler L, Dainat J, Pucholt P, Nordlund J, Martin T, Rönnberg-Wästljung AC, Nystedt B, Berlin S, Mank JE. Genome assembly of the basket willow, Salix viminalis, reveals earliest stages of sex chromosome expansion. BMC Biol 2020. [PMID: 32605573 DOI: 10.1101/589804v1.full] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/23/2023] Open
Abstract
BACKGROUND Sex chromosomes have evolved independently multiple times in eukaryotes and are therefore considered a prime example of convergent genome evolution. Sex chromosomes are known to emerge after recombination is halted between a homologous pair of chromosomes, and this leads to a range of non-adaptive modifications causing gradual degeneration and gene loss on the sex-limited chromosome. However, the proximal causes of recombination suppression and the pace at which degeneration subsequently occurs remain unclear. RESULTS Here, we use long- and short-read single-molecule sequencing approaches to assemble and annotate a draft genome of the basket willow, Salix viminalis, a species with a female heterogametic system at the earliest stages of sex chromosome emergence. Our single-molecule approach allowed us to phase the emerging Z and W haplotypes in a female, and we detected very low levels of Z/W single-nucleotide divergence in the non-recombining region. Linked-read sequencing of the same female and an additional male (ZZ) revealed the presence of two evolutionary strata supported by both divergence between the Z and W haplotypes and by haplotype phylogenetic trees. Gene order is still largely conserved between the Z and W homologs, although the W-linked region contains genes involved in cytokinin signaling regulation that are not syntenic with the Z homolog. Furthermore, we find no support across multiple lines of evidence for inversions, which have long been assumed to halt recombination between the sex chromosomes. CONCLUSIONS Our data suggest that selection against recombination is a more gradual process at the earliest stages of sex chromosome formation than would be expected from an inversion and may result instead from the accumulation of transposable elements. Our results present a cohesive understanding of the earliest genomic consequences of recombination suppression as well as valuable insights into the initial stages of sex chromosome formation and regulation of sex differentiation.
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Affiliation(s)
- Pedro Almeida
- Department of Genetics, Evolution & Environment, University College London, London, UK.
| | - Estelle Proux-Wera
- Department of Biochemistry and Biophysics, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Stockholm University, Stockholm, Sweden
| | - Allison Churcher
- Department of Molecular Biology, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Umeå University, Umeå, Sweden
| | - Lucile Soler
- Department of Medical Biochemistry and Microbiology, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Jacques Dainat
- Department of Medical Biochemistry and Microbiology, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Pascal Pucholt
- Department of Medical Sciences, Section of Rheumatology, Uppsala University, Uppsala, Sweden
- Department of Plant Biology, Uppsala BioCenter, Linnean Centre for Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Jessica Nordlund
- Department of Medical Sciences, National Genomics Infrastructure, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Tom Martin
- Department of Medical Sciences, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Ann-Christin Rönnberg-Wästljung
- Department of Plant Biology, Uppsala BioCenter, Linnean Centre for Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Björn Nystedt
- Department of Cell and Molecular Biology, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Uppsala University, Uppsala, Sweden
| | - Sofia Berlin
- Department of Plant Biology, Uppsala BioCenter, Linnean Centre for Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Judith E Mank
- Department of Genetics, Evolution & Environment, University College London, London, UK
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, Canada
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7
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Scharmann M, Grafe TU, Metali F, Widmer A. Sex is determined by XY chromosomes across the radiation of dioecious Nepenthes pitcher plants. Evol Lett 2019; 3:586-597. [PMID: 31867120 PMCID: PMC6906984 DOI: 10.1002/evl3.142] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 08/23/2019] [Accepted: 09/03/2019] [Indexed: 12/17/2022] Open
Abstract
Species with separate sexes (dioecy) are a minority among flowering plants, but dioecy has evolved multiple times independently in their history. The sex-determination system and sex-linked genomic regions are currently identified in a limited number of dioecious plants only. Here, we study the sex-determination system in a genus of dioecious plants that lack heteromorphic sex chromosomes and are not amenable to controlled breeding: Nepenthes pitcher plants. We genotyped wild populations of flowering males and females of three Nepenthes taxa using ddRAD-seq and sequenced a male inflorescence transcriptome. We developed a statistical tool (privacy rarefaction) to distinguish true sex specificity from stochastic noise in read coverage of sequencing data from wild populations and identified male-specific loci and XY-patterned single nucleotide polymorphsims (SNPs) in all three Nepenthes taxa, suggesting the presence of homomorphic XY sex chromosomes. The male-specific region of the Y chromosome showed little conservation among the three taxa, except for the essential pollen development gene DYT1 that was confirmed as male specific by PCR in additional Nepenthes taxa. Hence, dioecy and part of the male-specific region of the Nepenthes Y-chromosomes likely have a single evolutionary origin.
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Affiliation(s)
- Mathias Scharmann
- Institute of Integrative BiologyETH ZurichZürich8092Switzerland
- Department of Ecology and EvolutionUniversity of LausanneLausanne1015Switzerland
| | - T. Ulmar Grafe
- Faculty of ScienceUniversiti Brunei DarussalamGadongBE 1410Brunei Darussalam
| | - Faizah Metali
- Faculty of ScienceUniversiti Brunei DarussalamGadongBE 1410Brunei Darussalam
| | - Alex Widmer
- Institute of Integrative BiologyETH ZurichZürich8092Switzerland
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8
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Tennessen JA, Wei N, Straub SCK, Govindarajulu R, Liston A, Ashman TL. Repeated translocation of a gene cassette drives sex-chromosome turnover in strawberries. PLoS Biol 2018; 16:e2006062. [PMID: 30148831 PMCID: PMC6128632 DOI: 10.1371/journal.pbio.2006062] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 09/07/2018] [Accepted: 08/09/2018] [Indexed: 11/30/2022] Open
Abstract
Turnovers of sex-determining systems represent important diversifying forces across eukaryotes. Shifts in sex chromosomes—but conservation of the master sex-determining genes—characterize distantly related animal lineages. Yet in plants, in which separate sexes have evolved repeatedly and sex chromosomes are typically homomorphic, we do not know whether such translocations drive sex-chromosome turnovers within closely related taxonomic groups. This phenomenon can only be demonstrated by identifying sex-associated nucleotide sequences, still largely unknown in plants. The wild North American octoploid strawberries (Fragaria) exhibit separate sexes (dioecy) with homomorphic, female heterogametic (ZW) inheritance, yet sex maps to three different chromosomes in different taxa. To characterize these turnovers, we identified sequences unique to females and assembled their reads into contigs. For most octoploid Fragaria taxa, a short (13 kb) sequence was observed in all females and never in males, implicating it as the sex-determining region (SDR). This female-specific “SDR cassette” contains both a gene with a known role in fruit and pollen production and a novel retrogene absent on Z and autosomal chromosomes. Phylogenetic comparison of SDR cassettes revealed three clades and a history of repeated translocation. Remarkably, the translocations can be ordered temporally due to the capture of adjacent sequence with each successive move. The accumulation of the “souvenir” sequence—and the resultant expansion of the hemizygous SDR over time—could have been adaptive by locking genes into linkage with sex. Terminal inverted repeats at the insertion borders suggest a means of movement. To our knowledge, this is the first plant SDR shown to be translocated, and it suggests a new mechanism (“move-lock-grow”) for expansion and diversification of incipient sex chromosomes. Sex chromosomes frequently restructure themselves during organismal evolution, often becoming highly differentiated. This dynamic process is poorly understood for most taxa, especially during the early stages typical of many dioecious flowering plants. We show that in wild strawberries, a female-specific region of DNA is associated with sex and has repeatedly changed its genomic location, each time increasing the size of the hemizygous female-specific sequence on the W sex chromosome. This observation shows, for the first time to our knowledge, that plant sex regions can “jump” and suggests that this phenomenon may be adaptive by gathering and locking new genes into linkage with sex. This conserved and presumed causal sex-determining sequence, which varies in both genomic location and degree of differentiation, will facilitate future studies to understand how sex chromosomes first begin to differentiate.
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Affiliation(s)
- Jacob A. Tennessen
- Department of Integrative Biology, Oregon State University, Corvallis, Oregon, United States of America
| | - Na Wei
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Shannon C. K. Straub
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, United States of America
| | - Rajanikanth Govindarajulu
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Aaron Liston
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, United States of America
| | - Tia-Lynn Ashman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- * E-mail:
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9
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McKown AD, Klápště J, Guy RD, Soolanayakanahally RY, La Mantia J, Porth I, Skyba O, Unda F, Douglas CJ, El-Kassaby YA, Hamelin RC, Mansfield SD, Cronk QCB. Sexual homomorphism in dioecious trees: extensive tests fail to detect sexual dimorphism in Populus †. Sci Rep 2017; 7:1831. [PMID: 28500332 PMCID: PMC5431824 DOI: 10.1038/s41598-017-01893-z] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 04/05/2017] [Indexed: 11/09/2022] Open
Abstract
The evolution of sexual dimorphism and expansion of sex chromosomes are both driven through sexual conflict, arising from differing fitness optima between males and females. Here, we pair work in poplar (Populus) describing one of the smallest sex-determining regions known thus far in complex eukaryotes (~100 kbp) with comprehensive tests for sexual dimorphism using >1300 individuals from two Populus species and assessing 96 non-reproductive functional traits. Against expectation, we found sexual homomorphism (no non-reproductive trait differences between the sexes), suggesting that gender is functionally neutral with respect to non-reproductive features that affect plant survival and fitness. Combined with a small sex-determining region, we infer that sexual conflict may be effectively stymied or non-existent within these taxa. Both sexual homomorphism and the small sex-determining region occur against a background of strong environmental selection and local adaptation in Populus. This presents a powerful hypothesis for the evolution of dioecious species. Here, we suggest that environmental selection may be sufficient to suppress and stymy sexual conflict if it acts orthogonal to sexual selection, thereby placing limitations on the evolution of sexual dimorphism and genomic expansion of sex chromosomes.
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Affiliation(s)
- Athena D McKown
- Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, Forest Sciences Centre, Vancouver, BC V6T 1Z4, Canada.
| | - Jaroslav Klápště
- Department of Dendrology and Forest Tree Breeding, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Prague, 165 21, Czech Republic.,Scion (New Zealand Forest Research Institute Ltd.), Whakarewarewa, Rotorua, 3046, New Zealand
| | - Robert D Guy
- Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, Forest Sciences Centre, Vancouver, BC V6T 1Z4, Canada
| | - Raju Y Soolanayakanahally
- Saskatoon Research and Development Centre, Agriculture and Agri-Food Canada, Saskatoon, SK, S7N 0X2, Canada
| | - Jonathan La Mantia
- United States Department of Agriculture-Agricultural Research Service (USDA-ARS), Corn and Soybean Research, Wooster, OH, 44691, USA
| | - Ilga Porth
- Department of Wood Science, Faculty of Forestry, University of British Columbia, Forest Sciences Centre, Vancouver, BC V6T 1Z4, Canada.,Département des sciences du bois et de la forêt, Faculté de foresterie, de géographie et de géomatique, Université Laval, Québec, QC G1V 0A6, Canada
| | - Oleksandr Skyba
- Department of Wood Science, Faculty of Forestry, University of British Columbia, Forest Sciences Centre, Vancouver, BC V6T 1Z4, Canada
| | - Faride Unda
- Department of Wood Science, Faculty of Forestry, University of British Columbia, Forest Sciences Centre, Vancouver, BC V6T 1Z4, Canada
| | - Carl J Douglas
- Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Yousry A El-Kassaby
- Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, Forest Sciences Centre, Vancouver, BC V6T 1Z4, Canada
| | - Richard C Hamelin
- Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, Forest Sciences Centre, Vancouver, BC V6T 1Z4, Canada
| | - Shawn D Mansfield
- Department of Wood Science, Faculty of Forestry, University of British Columbia, Forest Sciences Centre, Vancouver, BC V6T 1Z4, Canada
| | - Quentin C B Cronk
- Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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Bräutigam K, Soolanayakanahally R, Champigny M, Mansfield S, Douglas C, Campbell MM, Cronk Q. Sexual epigenetics: gender-specific methylation of a gene in the sex determining region of Populus balsamifera. Sci Rep 2017; 7:45388. [PMID: 28345647 PMCID: PMC5366940 DOI: 10.1038/srep45388] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 02/27/2017] [Indexed: 12/27/2022] Open
Abstract
Methylation has frequently been implicated in gender determination in plants. The recent discovery of the sex determining region (SDR) of balsam poplar, Populus balsamifera, pinpointed 13 genes with differentiated X and Y copies. We tested these genes for differential methylation using whole methylome sequencing of xylem tissue of multiple individuals grown under field conditions in two common gardens. The only SDR gene to show a marked pattern of gender-specific methylation is PbRR9, a member of the two component response regulator (type-A) gene family, involved in cytokinin signalling. It is an ortholog of Arabidopsis genes ARR16 and ARR17. The strongest patterns of differential methylation (mostly male-biased) are found in the putative promoter and the first intron. The 4th intron is strongly methylated in both sexes and the 5th intron is unmethylated in both sexes. Using a statistical learning algorithm we find that it is possible accurately to assign trees to gender using genome-wide methylation patterns alone. The strongest predictor is the region coincident with PbRR9, showing that this gene stands out against all genes in the genome in having the strongest sex-specific methylation pattern. We propose the hypothesis that PbRR9 has a direct, epigenetically mediated, role in poplar sex determination.
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Affiliation(s)
- Katharina Bräutigam
- Department of Biology, University of Toronto Missisauga, Mississauga ON, L5L 1C6, Canada
| | - Raju Soolanayakanahally
- Saskatoon Research and Development Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon SK, S7N OX2, Canada
| | - Marc Champigny
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada
| | - Shawn Mansfield
- Department of Wood Science, University of British Columbia, 4030-2424 Main Mall, Vancouver BC, V6T 1Z4, Canada
| | - Carl Douglas
- Department of Botany, University of British Columbia, Vancouver BC, V6T 1Z4, Canada
| | - Malcolm M Campbell
- Department of Molecular and Cellular Biology, University of Guelph, Guelph ON N1G 2W1, Canada
| | - Quentin Cronk
- Department of Botany, University of British Columbia, Vancouver BC, V6T 1Z4, Canada
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Rieseberg L, Geraldes A. Editorial 2016. Mol Ecol 2016; 25:433-49. [DOI: 10.1111/mec.13508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Cronk QCB, Needham I, Rudall PJ. Evolution of Catkins: Inflorescence Morphology of Selected Salicaceae in an Evolutionary and Developmental Context. FRONTIERS IN PLANT SCIENCE 2015; 6:1030. [PMID: 26697024 PMCID: PMC4671327 DOI: 10.3389/fpls.2015.01030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Accepted: 11/06/2015] [Indexed: 05/06/2023]
Abstract
Poplars (Populus sp.) and willows (Salix sp.) are well known woody plants common throughout the northern hemisphere, both with fully sequenced genomes. They bear compact unisexual inflorescences known as "catkins." Closely related genera of the "salicoid clade" within the family Salicaceae include the Asian genera Bennettiodendron, Idesia, Itoa, Poliothyrsis, and Carrierea and the Central American genera Olmediella and Macrohasseltia. Like willow and poplar, most of these genera are dioecious, but unlike willow and poplar they generally have loosely branched panicles rather than catkins, and less highly reduced flowers. However, the early developing inflorescences of Carrierea and Idesia show similarities to catkins which suggest possible pathways by which the salicoid catkin may have evolved.
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Affiliation(s)
- Quentin C. B. Cronk
- Department of Botany, University of British ColumbiaVancouver, BC, Canada
- *Correspondence: Quentin C. B. Cronk,
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