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Wang Y, Gong GN, Wang Y, Zhang RG, Hörandl E, Zhang ZX, Charlesworth D, He L. Gap-free X and Y chromosome assemblies of Salix arbutifolia reveal an evolutionary change from male to female heterogamety in willows, without a change in the position of the sex-determining locus. THE NEW PHYTOLOGIST 2024; 242:2872-2887. [PMID: 38581199 DOI: 10.1111/nph.19744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Accepted: 03/21/2024] [Indexed: 04/08/2024]
Abstract
In the Vetrix clade of Salix, a genus of woody flowering plants, sex determination involves chromosome 15, but an XY system has changed to a ZW system. We studied the detailed genetic changes involved. We used genome sequencing, with chromosome conformation capture (Hi-C) and PacBio HiFi reads to assemble chromosome level gap-free X and Y of Salix arbutifolia, and distinguished the haplotypes in the 15X- and 15Y-linked regions, to study the evolutionary history of the sex-linked regions (SLRs). Our sequencing revealed heteromorphism of the X and Y haplotypes of the SLR, with the X-linked region being considerably larger than the corresponding Y region, mainly due to accumulated repetitive sequences and gene duplications. The phylogenies of single-copy orthogroups within the SLRs indicate that S. arbutifolia and Salix purpurea share an ancestral SLR within a repeat-rich region near the chromosome 15 centromere. During the change in heterogamety, the X-linked region changed to a W-linked one, while the Z was derived from the Y.
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Affiliation(s)
- Yi Wang
- Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, 201602, China
- Laboratory of Systematic Evolution and Biogeography of Woody Plants, School of Ecology and Nature Conservation, Beijing Forestry University, Beijing, 100091, China
| | - Guang-Nan Gong
- Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, 201602, China
| | - Yuan Wang
- Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, 201602, China
| | - Ren-Gang Zhang
- Yunnan Key Laboratory for Integrative Conservation of Plant Species with Extremely Small Populations, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, Yunnan, China
| | - Elvira Hörandl
- Department of Systematics, Biodiversity and Evolution of Plants (with Herbarium), University of Goettingen, 37073, Göttingen, Germany
| | - Zhi-Xiang Zhang
- Laboratory of Systematic Evolution and Biogeography of Woody Plants, School of Ecology and Nature Conservation, Beijing Forestry University, Beijing, 100091, China
| | - Deborah Charlesworth
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3FL, UK
| | - Li He
- Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, 201602, China
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Bačovský V, Čegan R, Šimoníková D, Hřibová E, Hobza R. The Formation of Sex Chromosomes in Silene latifolia and S. dioica Was Accompanied by Multiple Chromosomal Rearrangements. FRONTIERS IN PLANT SCIENCE 2020; 11:205. [PMID: 32180787 PMCID: PMC7059608 DOI: 10.3389/fpls.2020.00205] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 02/11/2020] [Indexed: 05/02/2023]
Abstract
The genus Silene includes a plethora of dioecious and gynodioecious species. Two species, Silene latifolia (white campion) and Silene dioica (red campion), are dioecious plants, having heteromorphic sex chromosomes with an XX/XY sex determination system. The X and Y chromosomes differ mainly in size, DNA content and posttranslational histone modifications. Although it is generally assumed that the sex chromosomes evolved from a single pair of autosomes, it is difficult to distinguish the ancestral pair of chromosomes in related gynodioecious and hermaphroditic plants. We designed an oligo painting probe enriched for X-linked scaffolds from currently available genomic data and used this probe on metaphase chromosomes of S. latifolia (2n = 24, XY), S. dioica (2n = 24, XY), and two gynodioecious species, S. vulgaris (2n = 24) and S. maritima (2n = 24). The X chromosome-specific oligo probe produces a signal specifically on the X and Y chromosomes in S. latifolia and S. dioica, mainly in the subtelomeric regions. Surprisingly, in S. vulgaris and S. maritima, the probe hybridized to three pairs of autosomes labeling their p-arms. This distribution suggests that sex chromosome evolution was accompanied by extensive chromosomal rearrangements in studied dioecious plants.
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Affiliation(s)
- Václav Bačovský
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czechia
- *Correspondence: Václav Bačovský,
| | - Radim Čegan
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czechia
- Institute of Experimental Botany, Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czechia
| | - Denisa Šimoníková
- Institute of Experimental Botany, Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czechia
| | - Eva Hřibová
- Institute of Experimental Botany, Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czechia
| | - Roman Hobza
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czechia
- Institute of Experimental Botany, Czech Academy of Sciences, Centre of the Region Haná for Biotechnological and Agricultural Research, Olomouc, Czechia
- Roman Hobza,
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Bačovský V, Houben A, Kumke K, Hobza R. The distribution of epigenetic histone marks differs between the X and Y chromosomes in Silene latifolia. PLANTA 2019; 250:487-494. [PMID: 31069521 DOI: 10.1007/s00425-019-03182-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 05/03/2019] [Indexed: 05/18/2023]
Abstract
Contrasting patterns of histone modifications between the X and Y chromosome in Silene latifolia show euchromatic histone mark depletion on the Y chromosome and indicate hyperactivation of one X chromosome in females. Silene latifolia (white campion) is a dioecious plant with heteromorphic sex chromosomes (24, XX in females and 24, XY in males), and a genetically degenerated Y chromosome that is 1.4 times larger than the X chromosome. Although the two sex chromosomes differ in their DNA content, information about epigenetic histone marks and evidence of their function are scarce. We performed immunolabeling experiments using antibodies specific for active and suppressive histone modifications as well as pericentromere-specific histone modifications. We show that the Y chromosome is partially depleted of histone modifications important for transcriptionally active chromatin, and carries these marks only in the pseudo-autosomal region, but that it is not enriched for suppressive and pericentromere histone marks. We also show that two of the active marks are specifically enriched in one of the X chromosomes in females and in the X chromosome in males. Our data support recent findings that genetic imprinting mediates dosage compensation of sex chromosomes in S. latifolia.
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Affiliation(s)
- Václav Bačovský
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska 135, 612 65, Brno, Czech Republic.
| | - Andreas Houben
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, Gatersleben, 06466, Germany
| | - Katrin Kumke
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, Gatersleben, 06466, Germany
| | - Roman Hobza
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska 135, 612 65, Brno, Czech Republic.
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Puterova J, Kubat Z, Kejnovsky E, Jesionek W, Cizkova J, Vyskot B, Hobza R. The slowdown of Y chromosome expansion in dioecious Silene latifolia due to DNA loss and male-specific silencing of retrotransposons. BMC Genomics 2018; 19:153. [PMID: 29458354 PMCID: PMC5819184 DOI: 10.1186/s12864-018-4547-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 02/13/2018] [Indexed: 11/10/2022] Open
Abstract
Background The rise and fall of the Y chromosome was demonstrated in animals but plants often possess the large evolutionarily young Y chromosome that is thought has expanded recently. Break-even points dividing expansion and shrinkage phase of plant Y chromosome evolution are still to be determined. To assess the size dynamics of the Y chromosome, we studied intraspecific genome size variation and genome composition of male and female individuals in a dioecious plant Silene latifolia, a well-established model for sex-chromosomes evolution. Results Our genome size data are the first to demonstrate that regardless of intraspecific genome size variation, Y chromosome has retained its size in S. latifolia. Bioinformatics study of genome composition showed that constancy of Y chromosome size was caused by Y chromosome DNA loss and the female-specific proliferation of recently active dominant retrotransposons. We show that several families of retrotransposons have contributed to genome size variation but not to Y chromosome size change. Conclusions Our results suggest that the large Y chromosome of S. latifolia has slowed down or stopped its expansion. Female-specific proliferation of retrotransposons, enlarging the genome with exception of the Y chromosome, was probably caused by silencing of highly active retrotransposons in males and represents an adaptive mechanism to suppress degenerative processes in the haploid stage. Sex specific silencing of transposons might be widespread in plants but hidden in traditional hermaphroditic model plants. Electronic supplementary material The online version of this article (10.1186/s12864-018-4547-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Janka Puterova
- Department of Plant Developmental Genetics, Institute of Biophysics, Czech Academy of Sciences, Kralovopolska 135, 612 00, Brno, Czech Republic.,Department of Information Systems, Faculty of Information Technology, Brno University of Technology, 61200, Brno, Czech Republic
| | - Zdenek Kubat
- Department of Plant Developmental Genetics, Institute of Biophysics, Czech Academy of Sciences, Kralovopolska 135, 612 00, Brno, Czech Republic.
| | - Eduard Kejnovsky
- Department of Plant Developmental Genetics, Institute of Biophysics, Czech Academy of Sciences, Kralovopolska 135, 612 00, Brno, Czech Republic
| | - Wojciech Jesionek
- Department of Plant Developmental Genetics, Institute of Biophysics, Czech Academy of Sciences, Kralovopolska 135, 612 00, Brno, Czech Republic
| | - Jana Cizkova
- Centre of Plant Structural and Functional Genomics, Institute of Experimental Botany, Czech Academy of Sciences, 783 71, Olomouc - Holice, Czech Republic
| | - Boris Vyskot
- Department of Plant Developmental Genetics, Institute of Biophysics, Czech Academy of Sciences, Kralovopolska 135, 612 00, Brno, Czech Republic
| | - Roman Hobza
- Department of Plant Developmental Genetics, Institute of Biophysics, Czech Academy of Sciences, Kralovopolska 135, 612 00, Brno, Czech Republic. .,Centre of Plant Structural and Functional Genomics, Institute of Experimental Botany, Czech Academy of Sciences, 783 71, Olomouc - Holice, Czech Republic.
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Chromosome Evolution in Connection with Repetitive Sequences and Epigenetics in Plants. Genes (Basel) 2017; 8:genes8100290. [PMID: 29064432 PMCID: PMC5664140 DOI: 10.3390/genes8100290] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Revised: 10/16/2017] [Accepted: 10/18/2017] [Indexed: 01/18/2023] Open
Abstract
Chromosome evolution is a fundamental aspect of evolutionary biology. The evolution of chromosome size, structure and shape, number, and the change in DNA composition suggest the high plasticity of nuclear genomes at the chromosomal level. Repetitive DNA sequences, which represent a conspicuous fraction of every eukaryotic genome, particularly in plants, are found to be tightly linked with plant chromosome evolution. Different classes of repetitive sequences have distinct distribution patterns on the chromosomes. Mounting evidence shows that repetitive sequences may play multiple generative roles in shaping the chromosome karyotypes in plants. Furthermore, recent development in our understanding of the repetitive sequences and plant chromosome evolution has elucidated the involvement of a spectrum of epigenetic modification. In this review, we focused on the recent evidence relating to the distribution pattern of repetitive sequences in plant chromosomes and highlighted their potential relevance to chromosome evolution in plants. We also discussed the possible connections between evolution and epigenetic alterations in chromosome structure and repatterning, such as heterochromatin formation, centromere function, and epigenetic-associated transposable element inactivation.
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6
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Charlesworth et al. on Background Selection and Neutral Diversity. Genetics 2017; 204:829-832. [PMID: 28114095 DOI: 10.1534/genetics.116.196170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Bhowmick BK, Jha S. Dynamics of sex expression and chromosome diversity in Cucurbitaceae: a story in the making. J Genet 2016; 94:793-808. [PMID: 26690537 DOI: 10.1007/s12041-015-0562-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The family Cucurbitaceae showcases a wide range of sexual phenotypes being variedly regulated by biological and environmental factors. In the present context, we have tried to assemble reports of cytogenetic investigations carried out in cucurbits accompanied by information on sex expression diversities and chromosomal or molecular basis of sex determination in dioecious (or other sexual types, if reported) taxa known so far. Most of the Cucurbitaceae tribes have mixed sexual phenotypes with varying range of chromosome numbers and hence, ancestral conditions become difficult to probe. Occurrence of polyploidy is rare in the family and has no influence on sexual traits. The sex determination mechanisms have been elucidated in some well-studied taxa like Bryonia,Coccinia and Cucumis showing interplay of genic, biochemical, developmental and sometimes chromosomal determinants. Substantial knowledge about genic and molecular sex differentiation has been obtained for genera like Momordica, Cucurbita and Trichosanthes. The detailed information on sex determination schemes, genomic sequences and molecular phylogenetic relationships facilitate further comprehensive investigations in the tribe Bryonieae. The discovery of organ identity genes and sex-specific sequences regulating sexual behaviour in Coccinia,Cucumis and Cucurbita opens up opportunities of relevant investigations to answer yet unaddressed questions pertaining to floral unisexuality, dioecy and chromosome evolution in the family. The present discussion brings the genera in light, previously recognized under subfamily Nhandiroboideae, where the study of chromosome cytology and sex determination mechanisms can simplify our understanding of sex expression pathways and its phylogenetic impacts.
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Affiliation(s)
- Biplab Kumar Bhowmick
- Centre of Advanced Study, Department of Botany, University of Calcutta, 35, Ballygunge Circular Road, Kolkata 700 019, India.
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8
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Li SF, Zhang GJ, Yuan JH, Deng CL, Gao WJ. Repetitive sequences and epigenetic modification: inseparable partners play important roles in the evolution of plant sex chromosomes. PLANTA 2016; 243:1083-95. [PMID: 26919983 DOI: 10.1007/s00425-016-2485-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Accepted: 02/07/2016] [Indexed: 05/03/2023]
Abstract
The present review discusses the roles of repetitive sequences played in plant sex chromosome evolution, and highlights epigenetic modification as potential mechanism of repetitive sequences involved in sex chromosome evolution. Sex determination in plants is mostly based on sex chromosomes. Classic theory proposes that sex chromosomes evolve from a specific pair of autosomes with emergence of a sex-determining gene(s). Subsequently, the newly formed sex chromosomes stop recombination in a small region around the sex-determining locus, and over time, the non-recombining region expands to almost all parts of the sex chromosomes. Accumulation of repetitive sequences, mostly transposable elements and tandem repeats, is a conspicuous feature of the non-recombining region of the Y chromosome, even in primitive one. Repetitive sequences may play multiple roles in sex chromosome evolution, such as triggering heterochromatization and causing recombination suppression, leading to structural and morphological differentiation of sex chromosomes, and promoting Y chromosome degeneration and X chromosome dosage compensation. In this article, we review the current status of this field, and based on preliminary evidence, we posit that repetitive sequences are involved in sex chromosome evolution probably via epigenetic modification, such as DNA and histone methylation, with small interfering RNAs as the mediator.
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Affiliation(s)
- Shu-Fen Li
- College of Life Sciences, Henan Normal University, Xinxiang, 453007, China
| | - Guo-Jun Zhang
- School of Basic Medical Sciences, Xinxiang Medical University, Xinxiang, 453003, China
| | - Jin-Hong Yuan
- College of Life Sciences, Henan Normal University, Xinxiang, 453007, China
| | - Chuan-Liang Deng
- College of Life Sciences, Henan Normal University, Xinxiang, 453007, China
| | - Wu-Jun Gao
- College of Life Sciences, Henan Normal University, Xinxiang, 453007, China.
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Hossain MU, Islam M, Afroz M, Sultana SS, Alam SS. Karyotype and RAPD Analysis of Male and Female <i>Coccinia grandis</i> L. from Bangladesh. CYTOLOGIA 2016. [DOI: 10.1508/cytologia.81.349] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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10
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Bhowmick BK, Yamamoto M, Jha S. Chromosomal localization of 45S rDNA, sex-specific C values, and heterochromatin distribution in Coccinia grandis (L.) Voigt. PROTOPLASMA 2016; 253:201-209. [PMID: 25795278 DOI: 10.1007/s00709-015-0797-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 03/05/2015] [Indexed: 06/04/2023]
Abstract
Coccinia grandis is a widely distributed dioecious cucurbit in India, with heteromorphic sex chromosomes and X-Y sex determination mode. The present study aids in the cytogenetic characterization of four native populations of this plant employing distribution patterns of 45S rDNA on chromosomes and guanine-cytosine (GC)-rich heterochromatin in the genome coupled with flow cytometric determination of genome sizes. Existence of four nucleolar chromosomes could be confirmed by the presence of four telomeric 45S rDNA signals in both male and female plants. All four 45S rDNA sites are rich in heterochromatin evident from the co-localization of telomeric chromomycin A (CMA)(+ve) signals. The size of 45S rDNA signal was found to differ between the homologues of one nucleolar chromosome pair. The distribution of heterochromatin is found to differ among the male and female populations. The average GC-rich heterochromatin content of male and female populations is 23.27 and 29.86 %, respectively. Moreover, the male plants have a genome size of 0.92 pg/2C while the female plants have a size of 0.73 pg/2C, reflecting a huge genomic divergence between the genders. The great variation in genome size is owing to the presence of Y chromosome in the male populations, playing a multifaceted role in sexual divergence in C. grandis.
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Affiliation(s)
- Biplab Kumar Bhowmick
- Center of Advanced Study, Department of Botany, University of Calcutta 35, Ballygunge Circular Road, Kolkata, West Bengal, 700019, India.
| | - Masashi Yamamoto
- Faculty of Agriculture, Kagoshima University, 1-21-24, Korimoto, Kagoshima, 890-0065, Japan.
| | - Sumita Jha
- Center of Advanced Study, Department of Botany, University of Calcutta 35, Ballygunge Circular Road, Kolkata, West Bengal, 700019, India.
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Abstract
Background Silene latifolia represents one of the best-studied plant sex chromosome systems. A new approach using RNA-seq data has recently identified hundreds of new sex-linked genes in this species. However, this approach is expected to miss genes that are either not expressed or are expressed at low levels in the tissue(s) used for RNA-seq. Therefore other independent approaches are needed to discover such sex-linked genes. Results Here we used 10 well-characterized S. latifolia sex-linked genes and their homologs in Silene vulgaris, a species without sex chromosomes, to screen BAC libraries of both species. We isolated and sequenced 4 Mb of BAC clones of S. latifolia X and Y and S. vulgaris genomic regions, which yielded 59 new sex-linked genes (with S. vulgaris homologs for some of them). We assembled sequences that we believe represent the tip of the Xq arm. These sequences are clearly not pseudoautosomal, so we infer that the S. latifolia X has a single pseudoautosomal region (PAR) on the Xp arm. The estimated mean gene density in X BACs is 2.2 times lower than that in S. vulgaris BACs, agreeing with the genome size difference between these species. Gene density was estimated to be extremely low in the Y BAC clones. We compared our BAC-located genes with the sex-linked genes identified in previous RNA-seq studies, and found that about half of them (those with low expression in flower buds) were not identified as sex-linked in previous RNA-seq studies. We compiled a set of ~70 validated X/Y genes and X-hemizygous genes (without Y copies) from the literature, and used these genes to show that X-hemizygous genes have a higher probability of being undetected by the RNA-seq approach, compared with X/Y genes; we used this to estimate that about 30 % of our BAC-located genes must be X-hemizygous. The estimate is similar when we use BAC-located genes that have S. vulgaris homologs, which excludes genes that were gained by the X chromosome. Conclusions Our BAC sequencing identified 59 new sex-linked genes, and our analysis of these BAC-located genes, in combination with RNA-seq data suggests that gene losses from the S. latifolia Y chromosome could be as high as 30 %, higher than previous estimates of 10-20 %. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1698-7) contains supplementary material, which is available to authorized users.
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Abstract
Dioecy (separate male and female individuals) ensures outcrossing and is more prevalent in animals than in plants. Although it is common in bryophytes and gymnosperms, only 5% of angiosperms are dioecious. In dioecious higher plants, flowers borne on male and female individuals are, respectively deficient in functional gynoecium and androecium. Dioecy is inherited via three sex chromosome systems: XX/XY, XX/X0 and WZ/ZZ, such that XX or WZ is female and XY, X0 or ZZ are males. The XX/XY system generates the rarer XX/X0 and WZ/ZZ systems. An autosome pair begets XY chromosomes. A recessive loss-of-androecium mutation (ana) creates X chromosome and a dominant gynoecium-suppressing (GYS) mutation creates Y chromosome. The ana/ANA and gys/GYS loci are in the sex-determining region (SDR) of the XY pair. Accumulation of inversions, deleterious mutations and repeat elements, especially transposons, in the SDR of Y suppresses recombination between X and Y in SDR, making Y labile and increasingly degenerate and heteromorphic from X. Continued recombination between X and Y in their pseudoautosomal region located at the ends of chromosomal arms allows survival of the degenerated Y and of the species. Dioecy is presumably a component of the evolutionary cycle for the origin of new species. Inbred hermaphrodite species assume dioecy. Later they suffer degenerate-Y-led population regression. Cross-hybridization between such extinguishing species and heterologous species, followed by genome duplication of segregants from hybrids, give rise to new species.
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Castric V, Billiard S, Vekemans X. Trait transitions in explicit ecological and genomic contexts: plant mating systems as case studies. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 781:7-36. [PMID: 24277293 DOI: 10.1007/978-94-007-7347-9_2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Plants are astonishingly diverse in how they reproduce sexually, and the study of plant mating systems provides some of the most compelling cases of parallel and independent evolutionary transitions. In this chapter, we review how the massive amount of genomic data being produced is allowing long-standing predictions from ecological and evolutionary theory to be put to test. After a review of theoretical predictions about the importance of considering the genomic architecture of the mating system, we focus on a set of recent discoveries on how the mating system is controlled in a variety of model and non-model species. In parallel, genomic approaches have revealed the complex interaction between the evolution of genes controlling mating systems and genome evolution, both genome-wide and in the mating system control region. In several cases, major transitions in the mating system can be clearly associated with important ecological changes, hence illuminating an important interplay between ecological and genomic approaches. We also list a number of major unsolved questions that remain for the field, and highlight foreseeable conceptual developments that are likely to play a major role in our understanding of how plant mating systems evolve in Nature.
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Affiliation(s)
- Vincent Castric
- Laboratoire de Génétique et Evolution des Populations Végétales (GEPV), UMR 8198; CNRS, Université Lille 1, Sciences et Technologies, Cité Scientifique, Villeneuve d'Ascq, France,
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14
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Bergero R, Qiu S, Forrest A, Borthwick H, Charlesworth D. Expansion of the pseudo-autosomal region and ongoing recombination suppression in the Silene latifolia sex chromosomes. Genetics 2013; 194:673-86. [PMID: 23733786 PMCID: PMC3697972 DOI: 10.1534/genetics.113.150755] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 04/20/2013] [Indexed: 11/18/2022] Open
Abstract
There are two very interesting aspects to the evolution of sex chromosomes: what happens after recombination between these chromosome pairs stops and why suppressed recombination evolves. The former question has been intensively studied in a diversity of organisms, but the latter has been studied largely theoretically. To obtain empirical data, we used codominant genic markers in genetic mapping of the dioecious plant Silene latifolia, together with comparative mapping of S. latifolia sex-linked genes in S. vulgaris (a related hermaphrodite species without sex chromosomes). We mapped 29 S. latifolia fully sex-linked genes (including 21 newly discovered from transcriptome sequencing), plus 6 genes in a recombining pseudo-autosomal region (PAR) whose genetic map length is ∼25 cM in both male and female meiosis, suggesting that the PAR may contain many genes. Our comparative mapping shows that most fully sex-linked genes in S. latifolia are located on a single S. vulgaris linkage group and were probably inherited from a single autosome of an ancestor. However, unexpectedly, our maps suggest that the S. latifolia PAR region expanded through translocation events. Some genes in these regions still recombine in S. latifolia, but some genes from both addition events are now fully sex-linked. Recombination suppression is therefore still ongoing in S. latifolia, and multiple recombination suppression events have occurred in a timescale of few million years, much shorter than the timescale of formation of the most recent evolutionary strata of mammal and bird sex chromosomes.
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Affiliation(s)
- Roberta Bergero
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Ashworth Lab, Edinburgh EH9 3JT, United Kingdom
| | - Suo Qiu
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Ashworth Lab, Edinburgh EH9 3JT, United Kingdom
| | | | - Helen Borthwick
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Ashworth Lab, Edinburgh EH9 3JT, United Kingdom
| | - Deborah Charlesworth
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Ashworth Lab, Edinburgh EH9 3JT, United Kingdom
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Testing for the footprint of sexually antagonistic polymorphisms in the pseudoautosomal region of a plant sex chromosome pair. Genetics 2013; 194:663-72. [PMID: 23733787 DOI: 10.1534/genetics.113.152397] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The existence of sexually antagonistic (SA) polymorphism is widely considered the most likely explanation for the evolution of suppressed recombination of sex chromosome pairs. This explanation is largely untested empirically, and no such polymorphisms have been identified, other than in fish, where no evidence directly implicates these genes in events causing loss of recombination. We tested for the presence of loci with SA polymorphism in the plant Silene latifolia, which is dioecious (with separate male and female individuals) and has a pair of highly heteromorphic sex chromosomes, with XY males. Suppressed recombination between much of the Y and X sex chromosomes evolved in several steps, and the results in Bergero et al. (2013) show that it is still ongoing in the recombining or pseudoautosomal, regions (PARs) of these chromosomes. We used molecular evolutionary approaches to test for the footprints of SA polymorphisms, based on sequence diversity levels in S. latifolia PAR genes identified by genetic mapping. Nucleotide diversity is high for at least four of six PAR genes identified, and our data suggest the existence of polymorphisms maintained by balancing selection in this genome region, since molecular evolutionary (HKA) tests exclude an elevated mutation rate, and other tests also suggest balancing selection. The presence of sexually antagonistic alleles at a locus or loci in the PAR is suggested by the very different X and Y chromosome allele frequencies for at least one PAR gene.
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Abstract
It is now well established that plants have an important place in studies of sex chromosome evolution because of the repeated independent evolution of separate sexes and sex chromosomes. There has been considerable recent progress in studying plant sex chromosomes. In this review, I focus on how these recent studies have helped clarify or answer several important questions about sex chromosome evolution, and I shall also try to clarify some common misconceptions. I also outline future work that will be needed to make further progress, including testing some important ideas by genetic, molecular, and developmental approaches. Systems with different ages can clearly help show the time course of events during changes from an ancestral co-sexual state (hermaphroditism or monoecy), and I will also explain how different questions can be studied in lineages whose dioecy or sex chromosomes evolved at different times in the past.
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Affiliation(s)
- Deborah Charlesworth
- Institute of Evolutionary Biology, School of Biological Sciences, The University of Edinburgh, The King's Buildings, West Mains Road, Edinburgh EH9 3JT, UK.
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Sousa A, Fuchs J, Renner SS. Molecular cytogenetics (FISH, GISH) of Coccinia grandis : a ca. 3 myr-old species of cucurbitaceae with the largest Y/autosome divergence in flowering plants. Cytogenet Genome Res 2012. [PMID: 23207224 DOI: 10.1159/000345370] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The independent evolution of heteromorphic sex chromosomes in 19 species from 4 families of flowering plants permits studying X/Y divergence after the initial recombination suppression. Here, we document autosome/Y divergence in the tropical Cucurbitaceae Coccinia grandis, which is ca. 3 myr old. Karyotyping and C-value measurements show that the C. grandis Y chromosome has twice the size of any of the other chromosomes, with a male/female C-value difference of 0.094 pg or 10% of the total genome. FISH staining revealed 5S and 45S rDNA sites on autosomes but not on the Y chromosome, making it unlikely that rDNA contributed to the elongation of the Y chromosome; recent end-to-end fusion also seems unlikely given the lack of interstitial telomeric signals. GISH with different concentrations of female blocking DNA detected a possible pseudo-autosomal region on the Y chromosome, and C-banding suggests that the entire Y chromosome in C. grandis is heterochromatic. During meiosis, there is an end-to-end connection between the X and the Y chromosome, but the X does not otherwise differ from the remaining chromosomes. These findings and a review of plants with heteromorphic sex chromosomes reveal no relationship between species age and degree of sex chromosome dimorphism. Its relatively small genome size (0.943 pg/2C in males), large Y chromosome, and phylogenetic proximity to the fully sequenced Cucumis sativus make C. grandis a promising model to study sex chromosome evolution.
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Affiliation(s)
- A Sousa
- Systematic Botany and Mycology, University of Munich (LMU), Munich, Germany
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18
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Wang J, Na JK, Yu Q, Gschwend AR, Han J, Zeng F, Aryal R, VanBuren R, Murray JE, Zhang W, Navajas-Pérez R, Feltus FA, Lemke C, Tong EJ, Chen C, Man Wai C, Singh R, Wang ML, Min XJ, Alam M, Charlesworth D, Moore PH, Jiang J, Paterson AH, Ming R. Sequencing papaya X and Yh chromosomes reveals molecular basis of incipient sex chromosome evolution. Proc Natl Acad Sci U S A 2012; 109:13710-5. [PMID: 22869747 PMCID: PMC3427123 DOI: 10.1073/pnas.1207833109] [Citation(s) in RCA: 209] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Sex determination in papaya is controlled by a recently evolved XY chromosome pair, with two slightly different Y chromosomes controlling the development of males (Y) and hermaphrodites (Y(h)). To study the events of early sex chromosome evolution, we sequenced the hermaphrodite-specific region of the Y(h) chromosome (HSY) and its X counterpart, yielding an 8.1-megabase (Mb) HSY pseudomolecule, and a 3.5-Mb sequence for the corresponding X region. The HSY is larger than the X region, mostly due to retrotransposon insertions. The papaya HSY differs from the X region by two large-scale inversions, the first of which likely caused the recombination suppression between the X and Y(h) chromosomes, followed by numerous additional chromosomal rearrangements. Altogether, including the X and/or HSY regions, 124 transcription units were annotated, including 50 functional pairs present in both the X and HSY. Ten HSY genes had functional homologs elsewhere in the papaya autosomal regions, suggesting movement of genes onto the HSY, whereas the X region had none. Sequence divergence between 70 transcripts shared by the X and HSY revealed two evolutionary strata in the X chromosome, corresponding to the two inversions on the HSY, the older of which evolved about 7.0 million years ago. Gene content differences between the HSY and X are greatest in the older stratum, whereas the gene content and order of the collinear regions are identical. Our findings support theoretical models of early sex chromosome evolution.
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Affiliation(s)
- Jianping Wang
- Department of Plant Biology, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Jong-Kuk Na
- Department of Plant Biology, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Qingyi Yu
- Texas AgriLife Research Center, Department of Plant Pathology and Microbiology, Texas A&M University, Weslaco, TX 78596
- Hawaii Agriculture Research Center, Kunia, HI 96759
| | - Andrea R. Gschwend
- Department of Plant Biology, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Jennifer Han
- Department of Plant Biology, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Fanchang Zeng
- Department of Plant Biology, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Rishi Aryal
- Department of Plant Biology, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Robert VanBuren
- Department of Plant Biology, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Jan E. Murray
- Department of Plant Biology, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Wenli Zhang
- Department of Horticulture, University of Wisconsin, Madison, WI 53706
| | | | - F. Alex Feltus
- Plant Genome Mapping Laboratory, University of Georgia, Athens, GA 30606
| | - Cornelia Lemke
- Plant Genome Mapping Laboratory, University of Georgia, Athens, GA 30606
| | - Eric J. Tong
- Hawaii Agriculture Research Center, Kunia, HI 96759
| | - Cuixia Chen
- Department of Plant Biology, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Ching Man Wai
- Hawaii Agriculture Research Center, Kunia, HI 96759
- Department of Tropical Plants and Soil Sciences, University of Hawaii, Honolulu, HI 96822
| | | | - Ming-Li Wang
- Hawaii Agriculture Research Center, Kunia, HI 96759
| | - Xiang Jia Min
- Department of Biological Sciences, Youngstown State University, Youngstown, OH 44555
| | - Maqsudul Alam
- Advanced Studies in Genomics, Proteomics and Bioinformatics, University of Hawaii, Honolulu, HI 96822; and
| | - Deborah Charlesworth
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
| | | | - Jiming Jiang
- Department of Horticulture, University of Wisconsin, Madison, WI 53706
| | - Andrew H. Paterson
- Plant Genome Mapping Laboratory, University of Georgia, Athens, GA 30606
| | - Ray Ming
- Department of Plant Biology, University of Illinois at Urbana–Champaign, Urbana, IL 61801
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Muyle A, Zemp N, Deschamps C, Mousset S, Widmer A, Marais GAB. Rapid de novo evolution of X chromosome dosage compensation in Silene latifolia, a plant with young sex chromosomes. PLoS Biol 2012; 10:e1001308. [PMID: 22529744 PMCID: PMC3328428 DOI: 10.1371/journal.pbio.1001308] [Citation(s) in RCA: 124] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Accepted: 03/01/2012] [Indexed: 11/18/2022] Open
Abstract
Silene latifolia is a dioecious plant with heteromorphic sex chromosomes that have originated only ∼10 million years ago and is a promising model organism to study sex chromosome evolution in plants. Previous work suggests that S. latifolia XY chromosomes have gradually stopped recombining and the Y chromosome is undergoing degeneration as in animal sex chromosomes. However, this work has been limited by the paucity of sex-linked genes available. Here, we used 35 Gb of RNA-seq data from multiple males (XY) and females (XX) of an S. latifolia inbred line to detect sex-linked SNPs and identified more than 1,700 sex-linked contigs (with X-linked and Y-linked alleles). Analyses using known sex-linked and autosomal genes, together with simulations indicate that these newly identified sex-linked contigs are reliable. Using read numbers, we then estimated expression levels of X-linked and Y-linked alleles in males and found an overall trend of reduced expression of Y-linked alleles, consistent with a widespread ongoing degeneration of the S. latifolia Y chromosome. By comparing expression intensities of X-linked alleles in males and females, we found that X-linked allele expression increases as Y-linked allele expression decreases in males, which makes expression of sex-linked contigs similar in both sexes. This phenomenon is known as dosage compensation and has so far only been observed in evolutionary old animal sex chromosome systems. Our results suggest that dosage compensation has evolved in plants and that it can quickly evolve de novo after the origin of sex chromosomes.
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Affiliation(s)
- Aline Muyle
- Laboratoire de Biométrie et Biologie Evolutive (UMR 5558), CNRS/Université Lyon 1, Villeurbanne, France
| | - Niklaus Zemp
- Institute of Integrative Biology (IBZ), ETH Zurich, Zürich, Switzerland
| | | | - Sylvain Mousset
- Laboratoire de Biométrie et Biologie Evolutive (UMR 5558), CNRS/Université Lyon 1, Villeurbanne, France
| | - Alex Widmer
- Institute of Integrative Biology (IBZ), ETH Zurich, Zürich, Switzerland
- * E-mail: (GABM); (AW)
| | - Gabriel A. B. Marais
- Laboratoire de Biométrie et Biologie Evolutive (UMR 5558), CNRS/Université Lyon 1, Villeurbanne, France
- * E-mail: (GABM); (AW)
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20
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Cegan R, Vyskot B, Kejnovsky E, Kubat Z, Blavet H, Šafář J, Doležel J, Blavet N, Hobza R. Genomic diversity in two related plant species with and without sex chromosomes--Silene latifolia and S. vulgaris. PLoS One 2012; 7:e31898. [PMID: 22393373 PMCID: PMC3290532 DOI: 10.1371/journal.pone.0031898] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 01/16/2012] [Indexed: 01/25/2023] Open
Abstract
Background Genome size evolution is a complex process influenced by polyploidization, satellite DNA accumulation, and expansion of retroelements. How this process could be affected by different reproductive strategies is still poorly understood. Methodology/Principal Findings We analyzed differences in the number and distribution of major repetitive DNA elements in two closely related species, Silene latifolia and S. vulgaris. Both species are diploid and possess the same chromosome number (2n = 24), but differ in their genome size and mode of reproduction. The dioecious S. latifolia (1C = 2.70 pg DNA) possesses sex chromosomes and its genome is 2.5× larger than that of the gynodioecious S. vulgaris (1C = 1.13 pg DNA), which does not possess sex chromosomes. We discovered that the genome of S. latifolia is larger mainly due to the expansion of Ogre retrotransposons. Surprisingly, the centromeric STAR-C and TR1 tandem repeats were found to be more abundant in S. vulgaris, the species with the smaller genome. We further examined the distribution of major repetitive sequences in related species in the Caryophyllaceae family. The results of FISH (fluorescence in situ hybridization) on mitotic chromosomes with the Retand element indicate that large rearrangements occurred during the evolution of the Caryophyllaceae family. Conclusions/Significance Our data demonstrate that the evolution of genome size in the genus Silene is accompanied by the expansion of different repetitive elements with specific patterns in the dioecious species possessing the sex chromosomes.
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Affiliation(s)
- Radim Cegan
- Department of Plant Developmental Genetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic
- Department of Plant Biology, Faculty of Agronomy, Mendel University in Brno, Brno, Czech Republic
| | - Boris Vyskot
- Department of Plant Developmental Genetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic
| | - Eduard Kejnovsky
- Department of Plant Developmental Genetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic
| | - Zdenek Kubat
- Department of Plant Developmental Genetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic
| | - Hana Blavet
- Department of Plant Developmental Genetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic
| | - Jan Šafář
- Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany, Olomouc, Czech Republic
| | - Jaroslav Doležel
- Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany, Olomouc, Czech Republic
| | - Nicolas Blavet
- Institute of Integrative Biology, Plant Ecological Genetics, ETH Zurich, Zurich, Switzerland
| | - Roman Hobza
- Department of Plant Developmental Genetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Brno, Czech Republic
- * E-mail:
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21
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Kofler R, Betancourt AJ, Schlötterer C. Sequencing of pooled DNA samples (Pool-Seq) uncovers complex dynamics of transposable element insertions in Drosophila melanogaster. PLoS Genet 2012; 8:e1002487. [PMID: 22291611 PMCID: PMC3266889 DOI: 10.1371/journal.pgen.1002487] [Citation(s) in RCA: 148] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Accepted: 12/01/2011] [Indexed: 12/16/2022] Open
Abstract
Transposable elements (TEs) are mobile genetic elements that parasitize genomes by semi-autonomously increasing their own copy number within the host genome. While TEs are important for genome evolution, appropriate methods for performing unbiased genome-wide surveys of TE variation in natural populations have been lacking. Here, we describe a novel and cost-effective approach for estimating population frequencies of TE insertions using paired-end Illumina reads from a pooled population sample. Importantly, the method treats insertions present in and absent from the reference genome identically, allowing unbiased TE population frequency estimates. We apply this method to data from a natural Drosophila melanogaster population from Portugal. Consistent with previous reports, we show that low recombining genomic regions harbor more TE insertions and maintain insertions at higher frequencies than do high recombining regions. We conservatively estimate that there are almost twice as many “novel” TE insertion sites as sites known from the reference sequence in our population sample (6,824 novel versus 3,639 reference sites, with on average a 31-fold coverage per insertion site). Different families of transposable elements show large differences in their insertion densities and population frequencies. Our analyses suggest that the history of TE activity significantly contributes to this pattern, with recently active families segregating at lower frequencies than those active in the more distant past. Finally, using our high-resolution TE abundance measurements, we identified 13 candidate positively selected TE insertions based on their high population frequencies and on low Tajima's D values in their neighborhoods. Transposable elements (TE's) are parasitic genetic elements that spread by replicating themselves within a host genome. Most organisms are burdened with transposable elements; in fact, up to 80% of some genomes can consist of TE–derived DNA. Here, we use new sequencing technology to examine variation in genomic TE composition within a population at a finer scale and in a more unbiased fashion than has been possible before. We study a Portuguese population of D. melanogaster and find a large number of TE insertions, most of which occur in few individuals. Our analysis confirms that TE insertions are subject to purifying selection that counteracts their spread, and it suggests that the genome records waves of past TE invasions, with recently active elements occurring at low population frequency. We also find indications that TE insertions may sometimes have beneficial effects.
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Affiliation(s)
- Robert Kofler
- Institut für Populationsgenetik, Vetmeduni Vienna, Wien, Austria
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23
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Muir G, Bergero R, Charlesworth D, Filatov DA. Does local adaptation cause high population differentiation of Silene latifolia Y chromosomes? Evolution 2011; 65:3368-80. [PMID: 22133212 DOI: 10.1111/j.1558-5646.2011.01410.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Natural selection can reduce the effective population size of the nonrecombining Y chromosome, whereas local adaptation of Y-linked genes can increase the population divergence and overall intra-species polymorphism of Y-linked sequences. The plant Silene latifolia evolved a Y chromosome relatively recently, and most known X-linked genes have functional Y homologues, making the species interesting for comparisons of X- and Y-linked diversity and subdivision. Y-linked genes show higher population differentiation, compared to X-linked genes, and this might be maintained by local adaptation in Y-linked genes (or low sequence diversity). Here we attempt to test between these causes by investigating DNA polymorphism and population differentiation using a larger set of Y-linked and X-linked S. latifolia genes (than used previously), and show that net sequence divergence for Y-linked sequences (measured by D(a) , also known as δ) is low, and not consistently higher than X-linked genes. This does not support local adaptation, instead, the higher values of differentiation measures for the Y-linked genes probably result largely from reduced total variation on the Y chromosome, which in turn reflect deterministic processes lowering effective population sizes of evolving Y-chromosomes.
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Affiliation(s)
- Graham Muir
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, United Kingdom.
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24
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Hikosaka A, Nishimura K, Hikosaka-Katayama T, Kawahara A. Recent transposition activity of Xenopus T2 family miniature inverted-repeat transposable elements. Mol Genet Genomics 2011; 285:219-24. [PMID: 21234602 DOI: 10.1007/s00438-010-0599-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 12/27/2010] [Indexed: 10/18/2022]
Abstract
To investigate the recent transposition activity of T2 family miniature inverted-repeat transposable elements (MITEs) in Xenopus tropicalis (Western clawed frog), we analyzed the intraspecific polymorphisms associated with MITE insertion in X. tropicalis for three subfamilies of the T2 family (T2-A1, T2-C, and T2-E). A high frequency of MITE-insertion polymorphisms was observed at the T2-A1 (50%) and T2-C insertion loci (60%), but none were noted at the T2-E insertion locus (0%). Analyses of the collected data indicated that members of the T2-A1 and T2-C subfamilies may be currently active in the host species. Identification of these active transpositions will help us in understanding the mechanisms underlying the long-term survival (over several tens of millions of years) of the T2-A1 and T2-C subfamilies.
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Affiliation(s)
- Akira Hikosaka
- Graduate School of Integrated Arts and Sciences, Hiroshima University, Kagamiyama 1-7-1, Higashi-Hiroshima, Hiroshima 739-8521, Japan.
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25
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Oyama RK, Silber MV, Renner SS. A specific insertion of a solo-LTR characterizes the Y-chromosome of Bryonia dioica (Cucurbitaceae). BMC Res Notes 2010; 3:166. [PMID: 20546563 PMCID: PMC2898664 DOI: 10.1186/1756-0500-3-166] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Accepted: 06/14/2010] [Indexed: 11/24/2022] Open
Abstract
Background Relatively few species of flowering plants are dioecious and even fewer are known to have sex chromosomes. Current theory posits that homomorphic sex chromosomes, such as found in Bryonia dioica (Cucurbitaceae), offer insight into the early stages in the evolution of sex chromosomes from autosomes. Little is known about these early steps, but an accumulation of transposable element sequences has been observed on the Y-chromosomes of some species with heteromorphic sex chromosomes. Recombination, by which transposable elements are removed, is suppressed on at least part of the emerging Y-chromosome, and this may explain the correlation between the emergence of sex chromosomes and transposable element enrichment. Findings We sequenced 2321 bp of the Y-chromosome in Bryonia dioica that flank a male-linked marker, BdY1, reported previously. Within this region, which should be suppressed for recombination, we observed a solo-LTR nested in a Copia-like transposable element. We also found other, presumably paralogous, solo-LTRs in a consensus sequence of the underlying Copia-like transposable element. Conclusions Given that solo-LTRs arise via recombination events, it is noteworthy that we find one in a genomic region where recombination should be suppressed. Although the solo-LTR could have arisen before recombination was suppressed, creating the male-linked marker BdY1, our previous study on B. dioica suggested that BdY1 may not lie in the recombination-suppressed region of the Y-chromosome in all populations. Presence of a solo-LTR near BdY1 therefore fits with the observed correlation between retrotransposon accumulation and the suppression of recombination early in the evolution of sex chromosomes. These findings further suggest that the homomorphic sex chromosomes of B. dioica, the first organism for which genetic XY sex-determination was inferred, are evolutionarily young and offer reference information for comparative studies of other plant sex chromosomes.
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Affiliation(s)
- Ryan K Oyama
- Systematic Botany & Mycology, Ludwig-Maximilians-Universität (LMU Munich), 80638 Munich, Germany.
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Lockton S, Gaut BS. The evolution of transposable elements in natural populations of self-fertilizing Arabidopsis thaliana and its outcrossing relative Arabidopsis lyrata. BMC Evol Biol 2010; 10:10. [PMID: 20067644 PMCID: PMC2837042 DOI: 10.1186/1471-2148-10-10] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Accepted: 01/12/2010] [Indexed: 12/02/2022] Open
Abstract
Background Transposable Elements (TEs) make up the majority of plant genomes, and thus understanding TE evolutionary dynamics is key to understanding plant genome evolution. Plant reproductive systems are diverse and mating type variation is one factor among many hypothesized to influence TE evolutionary dynamics. Here, we collected a large TE-display data set in self-fertilizing Arabidopsis thaliana, and compared it to data gathered in outcrossing Arabidopsis lyrata. We analyzed seven TE families in four natural populations of each species to tease apart the effects of mating system, demography, transposition, and selection in determining patterns of TE diversity. Results Measures of TE band differentiation were largely consistent across TE families. However, patterns of diversity in A. thaliana Ac elements differed significantly from that other TEs, perhaps signaling a lack of recent transposition. Across TE families, we estimated higher allele frequencies and lower selection coefficients on A. thaliana TE insertions relative to A. lyrata TE insertions. Conclusions The differences in TE distributions between the two Arabidopsis species represents a synthesis of evolutionary forces that include the transposition dynamics of individual TE families and the demographic histories of populations. There are also species-specific differences that could be attributed to the effects of mating system, including higher overall allele frequencies in the selfing lineage and a greater proportion of among population TE diversity in the outcrossing lineage.
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Affiliation(s)
- Steven Lockton
- Department of Ecology and Evolutionary Biology, University of California, Irvine, USA.
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27
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The role of repetitive DNA in structure and evolution of sex chromosomes in plants. Heredity (Edinb) 2009; 102:533-41. [PMID: 19277056 DOI: 10.1038/hdy.2009.17] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Eukaryotic genomes contain a large proportion of repetitive DNA sequences, mostly transposable elements (TEs) and tandem repeats. These repetitive sequences often colonize specific chromosomal (Y or W chromosomes, B chromosomes) or subchromosomal (telomeres, centromeres) niches. Sex chromosomes, especially non-recombining regions of the Y chromosome, are subject to different evolutionary forces compared with autosomes. In non-recombining regions of the Y chromosome repetitive DNA sequences are accumulated, representing a dominant and early process forming the Y chromosome, probably before genes start to degenerate. Here we review the occurrence and role of repetitive DNA in Y chromosome evolution in various species with a focus on dioecious plants. We also discuss the potential link between recombination and transposition in shaping genomes.
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The evolution of plant genomes: scaling up from a population perspective. Curr Opin Genet Dev 2009; 18:565-70. [PMID: 19131240 DOI: 10.1016/j.gde.2008.11.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2008] [Revised: 11/14/2008] [Accepted: 11/18/2008] [Indexed: 02/02/2023]
Abstract
Plant genomes exhibit tremendous diversity in both their size and structure, with genome sizes across land plants ranging over two to three orders of magnitude and significant variation in structural organization was observed across species (EA Kellogg, JL Bennetzen, The evolution of nuclear genome structure in seed plants, Am J Bot 2004, 91:1709-1725). Five plant genomes are now either completely sequenced or in the draft stage; the grape (O Jaillon et al., The grapevine genome sequence suggests ancestral hexaploidization in major angiosperm phyla, Nature 2007, 449:463-467) and papaya (R Ming et al., The draft genome of the transgenic tropical fruit tree papaya (Carica papaya Linnaeus), Nature 2008, 452:991-997) whole genome sequences were reported most recently. Moreover, sequencing of 41 additional genomes is in progress. There is now an emerging consensus that understanding genome evolution requires consideration of the population genetics of genome diversification, and that description of evolutionary forces at the level of populations and within species can help identify the features that led to plant genome diversity (M Lynch, JS Conery, The origins of genome complexity, Science 2003, 302:1401-1404). In this review we focus on advances in our understanding of the mechanisms that drive the diversification of genomes. In particular, we look at the extent to which demographic features such as effective population size changes within species can drive genome evolution, discuss population genetic models of genome diversification associated with transposable element (TE) mobilization, and describe recent studies on the evolution of gene families.
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