1
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Liang X, Yang S, Wang D, Knief U. Characterization and distribution of de novo mutations in the zebra finch. Commun Biol 2024; 7:1243. [PMID: 39358581 PMCID: PMC11447093 DOI: 10.1038/s42003-024-06945-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Accepted: 09/24/2024] [Indexed: 10/04/2024] Open
Abstract
Germline de novo mutations (DNMs) provide the raw material for evolution. The DNM rate varies considerably between species, sexes and chromosomes. Here, we identify DNMs in the zebra finch (Taeniopygia guttata) across 16 parent-offspring trios using two genome assemblies of different quality. Using an independent genotyping assay, we validate 82% of the 150 candidate DNMs. DNM rates are consistent between both assemblies, with estimates of 6.14 × 10-9 and 6.36 × 10-9 per site per generation. We observe a strong paternal bias in DNM rates (male-to-female ratio ɑ ≈ 4), but this bias is in transition mutations only, leading to a transition-to-transversion ratio of 3.18 and 3.57. Finally, we find that DNMs tend to be randomly distributed across chromosomes, not associated with recombination hotspots or genic regions. However, the sex chromosome chrZ shows a roughly fourfold increased DNM rate compared to autosomes, which is more than the expected increase due to chrZ spending two-thirds of its time in males. Overall, our results further enhance our understanding of DNMs in passerine songbirds.
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Affiliation(s)
- Xixi Liang
- Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
| | - Shuai Yang
- Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Daiping Wang
- Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
- University of Chinese Academy of Sciences, Beijing, China.
| | - Ulrich Knief
- Evolutionary Biology & Ecology, Faculty of Biology, University of Freiburg, Freiburg, Germany
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2
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Jay P, Jeffries D, Hartmann FE, Véber A, Giraud T. Why do sex chromosomes progressively lose recombination? Trends Genet 2024; 40:564-579. [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] [MESH Headings] [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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3
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Venney CJ, Mérot C, Normandeau E, Rougeux C, Laporte M, Bernatchez L. Epigenetic and Genetic Differentiation Between Coregonus Species Pairs. Genome Biol Evol 2024; 16:evae013. [PMID: 38271269 PMCID: PMC10849188 DOI: 10.1093/gbe/evae013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 01/11/2024] [Accepted: 01/19/2024] [Indexed: 01/27/2024] Open
Abstract
Phenotypic diversification is classically associated with genetic differentiation and gene expression variation. However, increasing evidence suggests that DNA methylation is involved in evolutionary processes due to its phenotypic and transcriptional effects. Methylation can increase mutagenesis and could lead to increased genetic divergence between populations experiencing different environmental conditions for many generations, though there has been minimal empirical research on epigenetically induced mutagenesis in diversification and speciation. Whitefish, freshwater members of the salmonid family, are excellent systems to study phenotypic diversification and speciation due to the repeated divergence of benthic-limnetic species pairs serving as natural replicates. Here we investigate whole genome genetic and epigenetic differentiation between sympatric benthic-limnetic species pairs in lake and European whitefish (Coregonus clupeaformis and Coregonus lavaretus) from four lakes (N = 64). We found considerable, albeit variable, genetic and epigenetic differences between species pairs. All SNP types were enriched at CpG sites supporting the mutagenic nature of DNA methylation, though C>T SNPs were most common. We also found an enrichment of overlaps between outlier SNPs with the 5% highest FST between species and differentially methylated loci. This could possibly represent differentially methylated sites that have caused divergent genetic mutations between species, or divergent selection leading to both genetic and epigenetic variation at these sites. Our results support the hypothesis that DNA methylation contributes to phenotypic divergence and mutagenesis during whitefish speciation.
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Affiliation(s)
- Clare J Venney
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Canada
| | - Claire Mérot
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Canada
- UMR 6553 Ecobio, OSUR, CNRS, Université de Rennes, Rennes, France
| | - Eric Normandeau
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Canada
| | - Clément Rougeux
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Canada
| | - Martin Laporte
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Canada
- Ministère des Forêts, de la Faune et des Parcs (MFFP), Québec, Québec, Canada
| | - Louis Bernatchez
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec, Canada
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4
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Volná A, Bartas M, Nezval J, Pech R, Pečinka P, Špunda V, Červeň J. Beyond the Primary Structure of Nucleic Acids: Potential Roles of Epigenetics and Noncanonical Structures in the Regulations of Plant Growth and Stress Responses. Methods Mol Biol 2023; 2642:331-361. [PMID: 36944887 DOI: 10.1007/978-1-0716-3044-0_18] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023]
Abstract
Epigenetics deals with changes in gene expression that are not caused by modifications in the primary sequence of nucleic acids. These changes beyond primary structures of nucleic acids not only include DNA/RNA methylation, but also other reversible conversions, together with histone modifications or RNA interference. In addition, under particular conditions (such as specific ion concentrations or protein-induced stabilization), the right-handed double-stranded DNA helix (B-DNA) can form noncanonical structures commonly described as "non-B DNA" structures. These structures comprise, for example, cruciforms, i-motifs, triplexes, and G-quadruplexes. Their formation often leads to significant differences in replication and transcription rates. Noncanonical RNA structures have also been documented to play important roles in translation regulation and the biology of noncoding RNAs. In human and animal studies, the frequency and dynamics of noncanonical DNA and RNA structures are intensively investigated, especially in the field of cancer research and neurodegenerative diseases. In contrast, noncanonical DNA and RNA structures in plants have been on the fringes of interest for a long time and only a few studies deal with their formation, regulation, and physiological importance for plant stress responses. Herein, we present a review focused on the main fields of epigenetics in plants and their possible roles in stress responses and signaling, with special attention dedicated to noncanonical DNA and RNA structures.
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Affiliation(s)
- Adriana Volná
- Department of Physics, Faculty of Science, University of Ostrava, Ostrava, Czech Republic
| | - Martin Bartas
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, Ostrava, Czech Republic
| | - Jakub Nezval
- Department of Physics, Faculty of Science, University of Ostrava, Ostrava, Czech Republic
| | - Radomír Pech
- Department of Physics, Faculty of Science, University of Ostrava, Ostrava, Czech Republic
| | - Petr Pečinka
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, Ostrava, Czech Republic
| | - Vladimír Špunda
- Department of Physics, Faculty of Science, University of Ostrava, Ostrava, Czech Republic
- Global Change Research Institute, Czech Academy of Sciences, Brno, Czech Republic
| | - Jiří Červeň
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, Ostrava, Czech Republic.
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5
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Hanson HE, Liebl AL. The Mutagenic Consequences of DNA Methylation within and across Generations. EPIGENOMES 2022; 6:33. [PMID: 36278679 PMCID: PMC9624357 DOI: 10.3390/epigenomes6040033] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Revised: 09/20/2022] [Accepted: 09/28/2022] [Indexed: 12/28/2022] Open
Abstract
DNA methylation is an epigenetic modification with wide-ranging consequences across the life of an organism. This modification can be stable, persisting through development despite changing environmental conditions. However, in other contexts, DNA methylation can also be flexible, underlying organismal phenotypic plasticity. One underappreciated aspect of DNA methylation is that it is a potent mutagen; methylated cytosines mutate at a much faster rate than other genetic motifs. This mutagenic property of DNA methylation has been largely ignored in eco-evolutionary literature, despite its prevalence. Here, we explore how DNA methylation induced by environmental and other factors could promote mutation and lead to evolutionary change at a more rapid rate and in a more directed manner than through stochastic genetic mutations alone. We argue for future research on the evolutionary implications of DNA methylation driven mutations both within the lifetime of organisms, as well as across timescales.
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Affiliation(s)
- Haley E. Hanson
- Global and Planetary Health, University of South Florida, Tampa, FL 33620, USA
| | - Andrea L. Liebl
- Department of Biology, University of South Dakota, Vermillion, SD 57069, USA
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6
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Li SF, Lv CC, Lan LN, Jiang KL, Zhang YL, Li N, Deng CL, Gao WJ. DNA methylation is involved in sexual differentiation and sex chromosome evolution in the dioecious plant garden asparagus. HORTICULTURE RESEARCH 2021; 8:198. [PMID: 34465747 PMCID: PMC8408194 DOI: 10.1038/s41438-021-00633-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 05/25/2021] [Accepted: 06/01/2021] [Indexed: 05/04/2023]
Abstract
DNA methylation is a crucial regulatory mechanism in many biological processes. However, limited studies have dissected the contribution of DNA methylation to sexual differentiation in dioecious plants. In this study, we investigated the variances in methylation and transcriptional patterns of male and female flowers of garden asparagus. Compared with male flowers, female flowers at the same stages showed higher levels of DNA methylation. Both male and female flowers gained DNA methylation globally from the premeiotic to meiotic stages. Detailed analysis revealed that the increased DNA methylation was largely due to increased CHH methylation. Correlation analysis of differentially expressed genes and differentially methylated regions suggested that DNA methylation might not have contributed to the expression variation of the sex-determining genes SOFF and TDF1 but probably played important roles in sexual differentiation and flower development of garden asparagus. The upregulated genes AoMS1, AoLAP3, AoAMS, and AoLAP5 with varied methylated CHH regions might have been involved in sexual differentiation and flower development of garden asparagus. Plant hormone signaling genes and transcription factor genes also participated in sexual differentiation and flower development with potential epigenetic regulation. In addition, the CG and CHG methylation levels in the Y chromosome were notably higher than those in the X chromosome, implying that DNA methylation might have been involved in Y chromosome evolution. These data provide insights into the epigenetic modification of sexual differentiation and flower development and improve our understanding of sex chromosome evolution in garden asparagus.
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Affiliation(s)
- Shu-Fen Li
- College of Life Sciences, Henan Normal University, Xinxiang, 453007, China
| | - Can-Can Lv
- College of Life Sciences, Henan Normal University, Xinxiang, 453007, China
| | - Li-Na Lan
- College of Life Sciences, Henan Normal University, Xinxiang, 453007, China
| | - Kai-Lu Jiang
- College of Life Sciences, Henan Normal University, Xinxiang, 453007, China
| | - Yu-Lan Zhang
- College of Life Sciences, Henan Normal University, Xinxiang, 453007, China
| | - Ning Li
- 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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7
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Mezzasalma M, Guarino FM, Odierna G. Lizards as Model Organisms of Sex Chromosome Evolution: What We Really Know from a Systematic Distribution of Available Data? Genes (Basel) 2021; 12:1341. [PMID: 34573323 PMCID: PMC8468487 DOI: 10.3390/genes12091341] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 08/20/2021] [Accepted: 08/27/2021] [Indexed: 01/19/2023] Open
Abstract
Lizards represent unique model organisms in the study of sex determination and sex chromosome evolution. Among tetrapods, they are characterized by an unparalleled diversity of sex determination systems, including temperature-dependent sex determination (TSD) and genetic sex determination (GSD) under either male or female heterogamety. Sex chromosome systems are also extremely variable in lizards. They include simple (XY and ZW) and multiple (X1X2Y and Z1Z2W) sex chromosome systems and encompass all the different hypothesized stages of diversification of heterogametic chromosomes, from homomorphic to heteromorphic and completely heterochromatic sex chromosomes. The co-occurrence of TSD, GSD and different sex chromosome systems also characterizes different lizard taxa, which represent ideal models to study the emergence and the evolutionary drivers of sex reversal and sex chromosome turnover. In this review, we present a synthesis of general genome and karyotype features of non-snakes squamates and discuss the main theories and evidences on the evolution and diversification of their different sex determination and sex chromosome systems. We here provide a systematic assessment of the available data on lizard sex chromosome systems and an overview of the main cytogenetic and molecular methods used for their identification, using a qualitative and quantitative approach.
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Affiliation(s)
- Marcello Mezzasalma
- Department of Biology, University of Naples Federico II, I-80126 Naples, Italy; (F.M.G.); (G.O.)
- CIBIO-InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO, Universidade do Porto, Rua Padre Armando Quintas 7, 4485-661 Vairaõ, Portugal
| | - Fabio M. Guarino
- Department of Biology, University of Naples Federico II, I-80126 Naples, Italy; (F.M.G.); (G.O.)
| | - Gaetano Odierna
- Department of Biology, University of Naples Federico II, I-80126 Naples, Italy; (F.M.G.); (G.O.)
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8
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Renn SC, Hurd PL. Epigenetic Regulation and Environmental Sex Determination in Cichlid Fishes. Sex Dev 2021; 15:93-107. [PMID: 34433170 PMCID: PMC8440468 DOI: 10.1159/000517197] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2021] [Accepted: 05/12/2021] [Indexed: 12/14/2022] Open
Abstract
Studying environmental sex determination (ESD) in cichlids provides a phylogenetic and comparative approach to understand the evolution of the underlying mechanisms, their impact on the evolution of the overlying systems, and the neuroethology of life history strategies. Natural selection normally favors parents who invest equally in the development of male and female offspring, but evolution may favor deviations from this 50:50 ratio when environmental conditions produce an advantage for doing so. Many species of cichlids demonstrate ESD in response to water chemistry (temperature, pH, and oxygen concentration). The relative strengths of and the exact interactions between these factors vary between congeners, demonstrating genetic variation in sensitivity. The presence of sizable proportions of the less common sex towards the environmental extremes in most species strongly suggests the presence of some genetic sex-determining loci acting in parallel with the ESD factors. Sex determination and differentiation in these species does not seem to result in the organization of a final and irreversible sexual fate, so much as a life-long ongoing battle between competing male- and female-determining genetic and hormonal networks governed by epigenetic factors. We discuss what is and is not known about the epigenetic mechanism behind the differentiation of both gonads and sex differences in the brain. Beyond the well-studied tilapia species, the 2 best-studied dwarf cichlid systems showing ESD are the South American genus Apistogramma and the West African genus Pelvicachromis. Both species demonstrate male morphs with alternative reproductive tactics. We discuss the further neuroethology opportunities such systems provide to the study of epigenetics of alternative life history strategies and other behavioral variation.
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Affiliation(s)
| | - Peter L Hurd
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, CA
- Department of Psychology, University of Alberta, Edmonton, AB, CA
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9
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Piferrer F. Epigenetic mechanisms in sex determination and in the evolutionary transitions between sexual systems. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200110. [PMID: 34247505 PMCID: PMC8273503 DOI: 10.1098/rstb.2020.0110] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The hypothesis that epigenetic mechanisms of gene expression regulation have two main roles in vertebrate sex is presented. First, and within a given generation, by contributing to the acquisition and maintenance of (i) the male or female function once during the lifetime in individuals of gonochoristic species; and (ii) the male and female function in the same individual, either at the same time in simultaneous hermaphrodites, or first as one sex and then as the other in sequential hermaphrodites. Second, if environmental conditions change, epigenetic mechanisms may have also a role across generations, by providing the necessary phenotypic plasticity to facilitate the transition: (i) from one sexual system to another, or (ii) from one sex-determining mechanism to another. Furthermore, if the environmental change lasts enough time, epimutations could facilitate assimilation into genetic changes that stabilize the new sexual system or sex-determining mechanism. Examples supporting these assertions are presented, caveats or difficulties and knowledge gaps identified, and possible ways to test this hypothesis suggested. This article is part of the theme issue ‘Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part I)’.
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Affiliation(s)
- Francesc Piferrer
- Institut de Ciències del Mar (ICM), Spanish National Research Council (CSIC), Passeig Marítim, 37-49, 08003 Barcelona, Spain
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10
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Almeida P, Sandkam BA, Morris J, Darolti I, Breden F, Mank JE. Divergence and Remarkable Diversity of the Y Chromosome in Guppies. Mol Biol Evol 2021; 38:619-633. [PMID: 33022040 PMCID: PMC7826173 DOI: 10.1093/molbev/msaa257] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The guppy sex chromosomes show an extraordinary diversity in divergence across populations and closely related species. In order to understand the dynamics of the guppy Y chromosome, we used linked-read sequencing to assess Y chromosome evolution and diversity across upstream and downstream population pairs that vary in predator and food abundance in three replicate watersheds. Based on our population-specific genome assemblies, we first confirmed and extended earlier reports of two strata on the guppy sex chromosomes. Stratum I shows significant accumulation of male-specific sequence, consistent with Y divergence, and predates the colonization of Trinidad. In contrast, Stratum II shows divergence from the X, but no Y-specific sequence, and this divergence is greater in three replicate upstream populations compared with their downstream pair. Despite longstanding assumptions that sex chromosome recombination suppression is achieved through inversions, we find no evidence of inversions associated with either Stratum I or Stratum II. Instead, we observe a remarkable diversity in Y chromosome haplotypes within each population, even in the ancestral Stratum I. This diversity is likely due to gradual mechanisms of recombination suppression, which, unlike an inversion, allow for the maintenance of multiple haplotypes. In addition, we show that this Y diversity is dominated by low-frequency haplotypes segregating in the population, suggesting a link between haplotype diversity and female preference for rare Y-linked color variation. Our results reveal the complex interplay between recombination suppression and Y chromosome divergence at the earliest stages of sex chromosome divergence.
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Affiliation(s)
- Pedro Almeida
- Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Benjamin A Sandkam
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Jake Morris
- Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Iulia Darolti
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
| | - Felix Breden
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
| | - Judith E Mank
- Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada
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11
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Rodríguez Lorenzo JL, Hubinský M, Vyskot B, Hobza R. Histone post-translational modifications in Silene latifolia X and Y chromosomes suggest a mammal-like dosage compensation system. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2020; 299:110528. [PMID: 32900432 DOI: 10.1016/j.plantsci.2020.110528] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 05/07/2020] [Accepted: 05/09/2020] [Indexed: 06/11/2023]
Abstract
Silene latifolia is a model organism to study evolutionary young heteromorphic sex chromosome evolution in plants. Previous research indicates a Y-allele gene degeneration and a dosage compensation system already operating. Here, we propose an epigenetic approach based on analysis of several histone post-translational modifications (PTMs) to find the first epigenetic hints of the X:Y sex chromosome system regulation in S. latifolia. Through chromatin immunoprecipitation we interrogated six genes from X and Y alleles. Several histone PTMS linked to DNA methylation and transcriptional repression (H3K27me3, H3K23me, H3K9me2 and H3K9me3) and to transcriptional activation (H3K4me3 and H4K5, 8, 12, 16ac) were used. DNA enrichment (Immunoprecipitated DNA/input DNA) was analyzed and showed three main results: (i) promoters of the Y allele are associated with heterochromatin marks, (ii) promoters of the X allele in males are associated with activation of transcription marks and finally, (iii) promoters of X alleles in females are associated with active and repressive marks. Our finding indicates a transcription activation of X allele and transcription repression of Y allele in males. In females we found a possible differential regulation (up X1, down X2) of each female X allele. These results agree with the mammal-like epigenetic dosage compensation regulation.
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Affiliation(s)
- José Luis Rodríguez Lorenzo
- The Czech Academy of Sciences, Institute of Biophysics v.v.i., Department of Plant Developmental Genetics, Královopolská 135, 612 65, Brno, Czech Republic.
| | - Marcel Hubinský
- The Czech Academy of Sciences, Institute of Biophysics v.v.i., Department of Plant Developmental Genetics, Královopolská 135, 612 65, Brno, Czech Republic
| | - Boris Vyskot
- The Czech Academy of Sciences, Institute of Biophysics v.v.i., Department of Plant Developmental Genetics, Královopolská 135, 612 65, Brno, Czech Republic
| | - Roman Hobza
- The Czech Academy of Sciences, Institute of Biophysics v.v.i., Department of Plant Developmental Genetics, Královopolská 135, 612 65, Brno, Czech Republic
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12
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Driscoll RMH, Faber-Hammond JJ, O'Rourke CF, Hurd PL, Renn SCP. Epigenetic regulation of gonadal and brain aromatase expression in a cichlid fish with environmental sex determination. Gen Comp Endocrinol 2020; 296:113538. [PMID: 32585214 DOI: 10.1016/j.ygcen.2020.113538] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 03/11/2020] [Accepted: 05/14/2020] [Indexed: 11/26/2022]
Abstract
A fit animal must develop testes or ovaries, with brain and physiology to match. In species with alternative male morphs this coordination of development across tissues operates within sexes as well as between. For Pelvicachromis pulcher, an African cichlid in which early pH exposure influences both sex and alternative male morph, we sequence both copies of aromatase (cyp19a1), a key gene for sex determination. We analyze gene expression and epigenetic state, comparing gonad and brain tissue from females, alternative male morphs, and fry. Relative to brain, we find elevated expression of the A-copy in the ovaries but not testes. Methylation analysis suggests strong epigenetic regulation, with one region specifying sex and another specifying tissue. We find elevated brain expression of the B-copy with no sex or male morph differences. B-copy methylation follows that of the A-copy rather than corresponding to B-copy expression. In 30-day old fry, we see elevated B-copy expression in the head, but we do not see the expected elevated A-copy expression in the trunk that would reflect ovarian development. Interestingly, the A-copy epialleles that distinguish ovaries from testes are among the most explanatory patterns for variation among fry, suggesting epigenetic marking of sex prior to differentiation and thus laying the groundwork for mechanistic studies of epigenetic regulation of sex and morph differentiation.
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Affiliation(s)
- Rose M H Driscoll
- Department of Biology, Reed College, Portland, OR, USA; Department of Biology, University of Rochester, Rochester, NY, USA
| | | | | | - Peter L Hurd
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada; Department of Psychology, University of Alberta, Edmonton, AB, Canada
| | - Suzy C P Renn
- Department of Biology, Reed College, Portland, OR, USA.
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13
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Fruchard C, Badouin H, Latrasse D, Devani RS, Muyle A, Rhoné B, Renner SS, Banerjee AK, Bendahmane A, Marais GAB. Evidence for Dosage Compensation in Coccinia grandis, a Plant with a Highly Heteromorphic XY System. Genes (Basel) 2020; 11:E787. [PMID: 32668777 PMCID: PMC7397054 DOI: 10.3390/genes11070787] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 07/01/2020] [Accepted: 07/08/2020] [Indexed: 01/17/2023] Open
Abstract
About 15,000 angiosperms are dioecious, but the mechanisms of sex determination in plants remain poorly understood. In particular, how Y chromosomes evolve and degenerate, and whether dosage compensation evolves as a response, are matters of debate. Here, we focus on Coccinia grandis, a dioecious cucurbit with the highest level of X/Y heteromorphy recorded so far. We identified sex-linked genes using RNA sequences from a cross and a model-based method termed SEX-DETector. Parents and F1 individuals were genotyped, and the transmission patterns of SNPs were then analyzed. In the >1300 sex-linked genes studied, maximum X-Y divergence was 0.13-0.17, and substantial Y degeneration is implied by an average Y/X expression ratio of 0.63 and an inferred gene loss on the Y of ~40%. We also found reduced Y gene expression being compensated by elevated expression of corresponding genes on the X and an excess of sex-biased genes on the sex chromosomes. Molecular evolution of sex-linked genes in C. grandis is thus comparable to that in Silene latifolia, another dioecious plant with a strongly heteromorphic XY system, and cucurbits are the fourth plant family in which dosage compensation is described, suggesting it might be common in plants.
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Affiliation(s)
- Cécile Fruchard
- Laboratoire de Biométrie et Biologie Evolutive (LBBE), UMR5558, Université Lyon 1, 69622 Villeurbanne, France; (C.F.); (H.B.); (B.R.)
| | - Hélène Badouin
- Laboratoire de Biométrie et Biologie Evolutive (LBBE), UMR5558, Université Lyon 1, 69622 Villeurbanne, France; (C.F.); (H.B.); (B.R.)
| | - David Latrasse
- Institute of Plant Sciences Paris Saclay (IPS2), University of Paris Saclay, 91405 Orsay, France; (D.L.); (R.S.D.); (A.B.)
| | - Ravi S. Devani
- Institute of Plant Sciences Paris Saclay (IPS2), University of Paris Saclay, 91405 Orsay, France; (D.L.); (R.S.D.); (A.B.)
- Biology Division, Indian Institute of Science Education and Research (IISER), Pune 411008, Maharashtra, India;
| | - Aline Muyle
- Department of Ecology and Evolutionary Biology, University of California Irvine, Irvine, CA 92697, USA;
| | - Bénédicte Rhoné
- Laboratoire de Biométrie et Biologie Evolutive (LBBE), UMR5558, Université Lyon 1, 69622 Villeurbanne, France; (C.F.); (H.B.); (B.R.)
- Institut de Recherche pour le Développement (IRD), Université Montpellier, DIADE, F-34394 Montpellier, France
| | - Susanne S. Renner
- Systematic Botany and Mycology, University of Munich (LMU), Menzinger Str. 67, 80638 Munich, Germany;
| | - Anjan K. Banerjee
- Biology Division, Indian Institute of Science Education and Research (IISER), Pune 411008, Maharashtra, India;
| | - Abdelhafid Bendahmane
- Institute of Plant Sciences Paris Saclay (IPS2), University of Paris Saclay, 91405 Orsay, France; (D.L.); (R.S.D.); (A.B.)
| | - Gabriel A. B. Marais
- Laboratoire de Biométrie et Biologie Evolutive (LBBE), UMR5558, Université Lyon 1, 69622 Villeurbanne, France; (C.F.); (H.B.); (B.R.)
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14
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Furman BLS, Metzger DCH, Darolti I, Wright AE, Sandkam BA, Almeida P, Shu JJ, Mank JE. Sex Chromosome Evolution: So Many Exceptions to the Rules. Genome Biol Evol 2020; 12:750-763. [PMID: 32315410 PMCID: PMC7268786 DOI: 10.1093/gbe/evaa081] [Citation(s) in RCA: 115] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/14/2020] [Indexed: 01/10/2023] Open
Abstract
Genomic analysis of many nonmodel species has uncovered an incredible diversity of sex chromosome systems, making it possible to empirically test the rich body of evolutionary theory that describes each stage of sex chromosome evolution. Classic theory predicts that sex chromosomes originate from a pair of homologous autosomes and recombination between them is suppressed via inversions to resolve sexual conflict. The resulting degradation of the Y chromosome gene content creates the need for dosage compensation in the heterogametic sex. Sex chromosome theory also implies a linear process, starting from sex chromosome origin and progressing to heteromorphism. Despite many convergent genomic patterns exhibited by independently evolved sex chromosome systems, and many case studies supporting these theoretical predictions, emerging data provide numerous interesting exceptions to these long-standing theories, and suggest that the remarkable diversity of sex chromosomes is matched by a similar diversity in their evolution. For example, it is clear that sex chromosome pairs are not always derived from homologous autosomes. In addition, both the cause and the mechanism of recombination suppression between sex chromosome pairs remain unclear, and it may be that the spread of recombination suppression is a more gradual process than previously thought. It is also clear that dosage compensation can be achieved in many ways, and displays a range of efficacy in different systems. Finally, the remarkable turnover of sex chromosomes in many systems, as well as variation in the rate of sex chromosome divergence, suggest that assumptions about the inevitable linearity of sex chromosome evolution are not always empirically supported, and the drivers of the birth-death cycle of sex chromosome evolution remain to be elucidated. Here, we concentrate on how the diversity in sex chromosomes across taxa highlights an equal diversity in each stage of sex chromosome evolution.
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Affiliation(s)
- Benjamin L S Furman
- Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - David C H Metzger
- Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Iulia Darolti
- Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Alison E Wright
- Department of Animal and Plant Sciences, University of Sheffield, United Kingdom
| | - Benjamin A Sandkam
- Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Pedro Almeida
- Department of Genetics, Evolution and Environment, University College London, United Kingdom
| | - Jacelyn J Shu
- Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Judith E Mank
- Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Genetics, Evolution and Environment, University College London, United Kingdom
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15
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Singh SK, Das D, Rhen T. Embryonic Temperature Programs Phenotype in Reptiles. Front Physiol 2020; 11:35. [PMID: 32082193 PMCID: PMC7005678 DOI: 10.3389/fphys.2020.00035] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 01/16/2020] [Indexed: 12/14/2022] Open
Abstract
Reptiles are critically affected by temperature throughout their lifespan, but especially so during early development. Temperature-induced changes in phenotype are a specific example of a broader phenomenon called phenotypic plasticity in which a single individual is able to develop different phenotypes when exposed to different environments. With climate change occurring at an unprecedented rate, it is important to study temperature effects on reptiles. For example, the potential impact of global warming is especially pronounced in species with temperature-dependent sex determination (TSD) because temperature has a direct effect on a key phenotypic (sex) and demographic (population sex ratios) trait. Reptiles with TSD also serve as models for studying temperature effects on the development of other traits that display continuous variation. Temperature directly influences metabolic and developmental rate of embryos and can have permanent effects on phenotype that last beyond the embryonic period. For instance, incubation temperature programs post-hatching hormone production and growth physiology, which can profoundly influence fitness. Here, we review current knowledge of temperature effects on phenotypic and developmental plasticity in reptiles. First, we examine the direct effect of temperature on biophysical processes, the concept of thermal performance curves, and the process of thermal acclimation. After discussing these reversible temperature effects, we focus the bulk of the review on developmental programming of phenotype by temperature during embryogenesis (i.e., permanent developmental effects). We focus on oviparous species because eggs are especially susceptible to changes in ambient temperature. We then discuss recent work probing the role of epigenetic mechanisms in mediating temperature effects on phenotype. Based on phenotypic effects of temperature, we return to the potential impact of global warming on reptiles. Finally, we highlight key areas for future research, including the identification of temperature sensors and assessment of genetic variation for thermosensitivity.
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Affiliation(s)
| | | | - Turk Rhen
- Department of Biology, University of North Dakota, Grand Forks, ND, United States
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16
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17
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Danchin É, Pocheville A, Huneman P. Early in life effects and heredity: reconciling neo-Darwinism with neo-Lamarckism under the banner of the inclusive evolutionary synthesis. Philos Trans R Soc Lond B Biol Sci 2019; 374:20180113. [PMID: 30966884 PMCID: PMC6460090 DOI: 10.1098/rstb.2018.0113] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/01/2018] [Indexed: 12/22/2022] Open
Abstract
Recent discoveries show that early in life effects often have long-lasting influences, sometimes even spanning several generations. Such intergenerational effects of early life events appear not easily reconcilable with strict genetic inheritance. However, an integrative evolutionary medicine of early life effects needs a sound view of inheritance in development and evolution. Here, we show how to articulate the gene-centred and non-gene-centred visions of inheritance. We first recall the coexistence of two gene concepts in scientific discussions, a statistical one (focused on patterns of parent-offspring resemblance, and implicitly including non-DNA-sequence-based resemblance), and a molecular one (based on the DNA sequence). We then show how all the different mechanisms of inheritance recently discovered can be integrated into an inclusive theory of evolution where different mechanisms would enable adaptation to changing environments at different timescales. One surprising consequence of this integrative vision of inheritance is that early in life effects start much earlier than fertilization. This article is part of the theme issue 'Developing differences: early-life effects and evolutionary medicine'.
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Affiliation(s)
- Étienne Danchin
- Laboratoire Évolution and Diversité Biologique (EDB UMR 5174), Université de Toulouse Midi-Pyrénées, CNRS, IRD, UPS, 118 route de Narbonne, Bat 4R1, 31062 Toulouse cedex 9, France
| | - Arnaud Pocheville
- Laboratoire Évolution and Diversité Biologique (EDB UMR 5174), Université de Toulouse Midi-Pyrénées, CNRS, IRD, UPS, 118 route de Narbonne, Bat 4R1, 31062 Toulouse cedex 9, France
- Department of Philosophy and Charles Perkins Centre, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Philippe Huneman
- Institut d'Histoire et de Philosophie des Sciences et des Techniques, CNRS/Université Paris I Panthéon-Sorbonne, Paris, France
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18
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Metzger DCH, Schulte PM. The DNA Methylation Landscape of Stickleback Reveals Patterns of Sex Chromosome Evolution and Effects of Environmental Salinity. Genome Biol Evol 2018; 10:775-785. [PMID: 29420714 PMCID: PMC5841383 DOI: 10.1093/gbe/evy034] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/05/2018] [Indexed: 12/12/2022] Open
Abstract
Epigenetic mechanisms such as DNA methylation are a key component of dosage compensation on sex chromosomes and have been proposed as an important source of phenotypic variation influencing plasticity and adaptive evolutionary processes, yet little is known about the role of DNA methylation in an ecological or evolutionary context in vertebrates. The threespine stickleback (Gasterosteus aculeatus) is an ecological and evolutionary model system that has been used to study mechanisms involved in the evolution of adaptive phenotypes in novel environments as well as the evolution heteromorphic sex chromosomes and dosage compensation in vertebrates. Using whole genome bisulfite sequencing, we compared genome-wide DNA methylation patterns between threespine stickleback males and females and between stickleback reared at different environmental salinities. Apparent hypermethylation of the younger evolutionary stratum of the stickleback X chromosome in females relative to males suggests a potential role of DNA methylation in the evolution of heteromorphic sex chromosomes. We also demonstrate that rearing salinity has genome-wide effects on DNA methylation levels, which has the potential to lead to the accumulation of epigenetic variation between natural populations in different environments.
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Affiliation(s)
- David C H Metzger
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Patricia M Schulte
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
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19
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Danchin E, Pocheville A, Rey O, Pujol B, Blanchet S. Epigenetically facilitated mutational assimilation: epigenetics as a hub within the inclusive evolutionary synthesis. Biol Rev Camb Philos Soc 2018. [PMCID: PMC6378602 DOI: 10.1111/brv.12453] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
After decades of debate about the existence of non‐genetic inheritance, the focus is now slowly shifting towards dissecting its underlying mechanisms. Here, we propose a new mechanism that, by integrating non‐genetic and genetic inheritance, may help build the long‐sought inclusive vision of evolution. After briefly reviewing the wealth of evidence documenting the existence and ubiquity of non‐genetic inheritance in a table, we review the categories of mechanisms of parent–offspring resemblance that underlie inheritance. We then review several lines of argument for the existence of interactions between non‐genetic and genetic components of inheritance, leading to a discussion of the contrasting timescales of action of non‐genetic and genetic inheritance. This raises the question of how the fidelity of the inheritance system can match the rate of environmental variation. This question is central to understanding the role of different inheritance systems in evolution. We then review and interpret evidence indicating the existence of shifts from inheritance systems with low to higher transmission fidelity. Based on results from different research fields we propose a conceptual hypothesis linking genetic and non‐genetic inheritance systems. According to this hypothesis, over the course of generations, shifts among information systems allow gradual matching between the rate of environmental change and the inheritance fidelity of the corresponding response. A striking conclusion from our review is that documented shifts between types of inherited non‐genetic information converge towards epigenetics (i.e. inclusively heritable molecular variation in gene expression without change in DNA sequence). We then interpret the well‐documented mutagenicity of epigenetic marks as potentially generating a final shift from epigenetic to genetic encoding. This sequence of shifts suggests the existence of a relay in inheritance systems from relatively labile ones to gradually more persistent modes of inheritance, a relay that could constitute a new mechanistic basis for the long‐proposed, but still poorly documented, hypothesis of genetic assimilation. A profound difference between the genocentric and the inclusive vision of heredity revealed by the genetic assimilation relay proposed here lies in the fact that a given form of inheritance can affect the rate of change of other inheritance systems. To explore the consequences of such inter‐connection among inheritance systems, we briefly review published theoretical models to build a model of genetic assimilation focusing on the shift in the engraving of environmentally induced phenotypic variation into the DNA sequence. According to this hypothesis, when environmental change remains stable over a sufficient number of generations, the relay among inheritance systems has the potential to generate a form of genetic assimilation. In this hypothesis, epigenetics appears as a hub by which non‐genetically inherited environmentally induced variation in traits can become genetically encoded over generations, in a form of epigenetically facilitated mutational assimilation. Finally, we illustrate some of the major implications of our hypothetical framework, concerning mutation randomness, the central dogma of molecular biology, concepts of inheritance and the curing of inherited disorders, as well as for the emergence of the inclusive evolutionary synthesis.
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Affiliation(s)
- Etienne Danchin
- Laboratoire Évolution & Diversité Biologique (EDB UMR 5174); Université de Toulouse Midi-Pyrénées, CNRS, IRD, UPS. 118 route de Narbonne, Bat 4R1; 31062 Toulouse Cedex 9 France
| | - Arnaud Pocheville
- Laboratoire Évolution & Diversité Biologique (EDB UMR 5174); Université de Toulouse Midi-Pyrénées, CNRS, IRD, UPS. 118 route de Narbonne, Bat 4R1; 31062 Toulouse Cedex 9 France
- Department of Philosophy and Charles Perkins Centre; University of Sydney; Sydney NSW 2006 Australia
| | - Olivier Rey
- CNRS, Station d'Ecologie Théorique et Expérimentale (SETE), UMR5321; 09200 Moulis France
- Université de Perpignan Via Domitia, IHPE UMR 5244, CNRS, IFREMER, Université de Montpellier; F-66860 Perpignan France
| | - Benoit Pujol
- Laboratoire Évolution & Diversité Biologique (EDB UMR 5174); Université de Toulouse Midi-Pyrénées, CNRS, IRD, UPS. 118 route de Narbonne, Bat 4R1; 31062 Toulouse Cedex 9 France
| | - Simon Blanchet
- Laboratoire Évolution & Diversité Biologique (EDB UMR 5174); Université de Toulouse Midi-Pyrénées, CNRS, IRD, UPS. 118 route de Narbonne, Bat 4R1; 31062 Toulouse Cedex 9 France
- CNRS, Station d'Ecologie Théorique et Expérimentale (SETE), UMR5321; 09200 Moulis France
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20
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Rodríguez Lorenzo JL, Hobza R, Vyskot B. DNA methylation and genetic degeneration of the Y chromosome in the dioecious plant Silene latifolia. BMC Genomics 2018; 19:540. [PMID: 30012097 PMCID: PMC6048894 DOI: 10.1186/s12864-018-4936-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Accepted: 07/10/2018] [Indexed: 02/01/2023] Open
Abstract
Background S. latifolia is a model organism for the study of sex chromosome evolution in plants. Its sex chromosomes include large regions in which recombination became gradually suppressed. The regions tend to expand over time resulting in the formation of evolutionary strata. Non-recombination and later accumulation of repetitive sequences is a putative cause of the size increase in the Y chromosome. Gene decay and accumulation of repetitive DNA are identified as key evolutionary events. Transposons in the X and Y chromosomes are distributed differently and there is a regulation of transposon insertion by DNA methylation of the target sequences, this points to an important role of DNA methylation during sex chromosome evolution in Silene latifolia. The aim of this study was to elucidate whether the reduced expression of the Y allele in S. latifolia is caused by genetic degeneration or if the cause is methylation triggered by transposons and repetitive sequences. Results Gene expression analysis in S. latifolia males has shown expression bias in both X and Y alleles. To determine whether these differences are caused by genetic degeneration or methylation spread by transposons and repetitive sequences, we selected several sex-linked genes with varying degrees of degeneration and from different evolutionary strata. Immunoprecipitation of methylated DNA (MeDIP) from promoter, exon and intron regions was used and validated through bisulfite sequencing. We found DNA methylation in males, and only in the promoter of genes of stratum I (older). The Y alleles in genes of stratum I were methylation enriched compared to X alleles. There was also abundant and high percentage methylation in the CHH context in most sequences, indicating de novo methylation through the RdDM pathway. Conclusions We speculate that TE accumulation and not gene decay is the cause of DNA methylation in the S. latifolia Y sex chromosome with influence on the process of heterochromatinization. Electronic supplementary material The online version of this article (10.1186/s12864-018-4936-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- José Luis Rodríguez Lorenzo
- Plant Developmental Genetics, Institute of Biophysics v.v.i, Academy of Sciences of the Czech Republic, Královopolská 135, 612 65, Brno, Czech Republic.
| | - Roman Hobza
- Plant Developmental Genetics, Institute of Biophysics v.v.i, Academy of Sciences of the Czech Republic, Královopolská 135, 612 65, Brno, Czech Republic
| | - Boris Vyskot
- Plant Developmental Genetics, Institute of Biophysics v.v.i, Academy of Sciences of the Czech Republic, Královopolská 135, 612 65, Brno, Czech Republic
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21
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Ponnikas S, Sigeman H, Abbott JK, Hansson B. Why Do Sex Chromosomes Stop Recombining? Trends Genet 2018; 34:492-503. [DOI: 10.1016/j.tig.2018.04.001] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2017] [Revised: 03/22/2018] [Accepted: 04/02/2018] [Indexed: 01/05/2023]
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22
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Alam SMI, Sarre SD, Gleeson D, Georges A, Ezaz T. Did Lizards Follow Unique Pathways in Sex Chromosome Evolution? Genes (Basel) 2018; 9:E239. [PMID: 29751579 PMCID: PMC5977179 DOI: 10.3390/genes9050239] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 04/26/2018] [Accepted: 04/26/2018] [Indexed: 02/02/2023] Open
Abstract
Reptiles show remarkable diversity in modes of reproduction and sex determination, including high variation in the morphology of sex chromosomes, ranging from homomorphic to highly heteromorphic. Additionally, the co-existence of genotypic sex determination (GSD) and temperature-dependent sex determination (TSD) within and among sister clades makes this group an attractive model to study and understand the evolution of sex chromosomes. This is particularly so with Lizards (Order Squamata) which, among reptiles, show extraordinary morphological diversity. They also show no particular pattern of sex chromosome degeneration of the kind observed in mammals, birds and or even in snakes. We therefore speculate that sex determination sensu sex chromosome evolution is labile and rapid and largely follows independent trajectories within lizards. Here, we review the current knowledge on the evolution of sex chromosomes in lizards and discuss how sex chromosome evolution within that group differs from other amniote taxa, facilitating unique evolutionary pathways.
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Affiliation(s)
| | - Stephen D Sarre
- Institute for Applied Ecology, University of Canberra, Canberra 2616, Australia.
| | - Dianne Gleeson
- Institute for Applied Ecology, University of Canberra, Canberra 2616, Australia.
| | - Arthur Georges
- Institute for Applied Ecology, University of Canberra, Canberra 2616, Australia.
| | - Tariq Ezaz
- Institute for Applied Ecology, University of Canberra, Canberra 2616, Australia.
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23
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Bräutigam K, Cronk Q. DNA Methylation and the Evolution of Developmental Complexity in Plants. FRONTIERS IN PLANT SCIENCE 2018; 9:1447. [PMID: 30349550 PMCID: PMC6186995 DOI: 10.3389/fpls.2018.01447] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 09/12/2018] [Indexed: 05/20/2023]
Abstract
All land plants so far examined use DNA methylation to silence transposons (TEs). DNA methylation therefore appears to have been co-opted in evolution from an original function in TE management to a developmental function (gene regulation) in both phenotypic plasticity and in normal development. The significance of DNA methylation to the evolution of developmental complexity in plants lies in its role in the management of developmental pathways. As such it is more important in fine tuning the presence, absence, and placement of organs rather than having a central role in the evolution of new organs. Nevertheless, its importance should not be underestimated as it contributes considerably to the range of phenotypic expression and complexity available to plants: the subject of the emerging field of epi-evodevo. Furthermore, changes in DNA methylation can function as a "soft" mutation that may be important in the early stages of major evolutionary novelty.
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Affiliation(s)
- Katharina Bräutigam
- Department of Biology, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Quentin Cronk
- Department of Botany, The University of British Columbia, Vancouver, BC, Canada
- *Correspondence: Quentin Cronk,
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24
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Mohanty JN, Nayak S, Jha S, Joshi RK. Transcriptome profiling of the floral buds and discovery of genes related to sex-differentiation in the dioecious cucurbit Coccinia grandis (L.) Voigt. Gene 2017; 626:395-406. [DOI: 10.1016/j.gene.2017.05.058] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 04/22/2017] [Accepted: 05/30/2017] [Indexed: 10/19/2022]
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25
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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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Kalinka A, Achrem M, Poter P. The DNA methylation level against the background of the genome size and t-heterochromatin content in some species of the genus Secale L. PeerJ 2017; 5:e2889. [PMID: 28149679 PMCID: PMC5267573 DOI: 10.7717/peerj.2889] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 12/08/2016] [Indexed: 01/05/2023] Open
Abstract
Methylation of cytosine in DNA is one of the most important epigenetic modifications in eukaryotes and plays a crucial role in the regulation of gene activity and the maintenance of genomic integrity. DNA methylation and other epigenetic mechanisms affect the development, differentiation or the response of plants to biotic and abiotic stress. This study compared the level of methylation of cytosines on a global (ELISA) and genomic scale (MSAP) between the species of the genus Secale. We analyzed whether the interspecific variation of cytosine methylation was associated with the size of the genome (C-value) and the content of telomeric heterochromatin. MSAP analysis showed that S. sylvestre was the most distinct species among the studied rye taxa; however, the results clearly indicated that these differences were not statistically significant. The total methylation level of the studied loci was very similar in all taxa and ranged from 60% in S. strictum ssp. africanum to 66% in S. cereale ssp. segetale, which confirmed the lack of significant differences in the sequence methylation pattern between the pairs of rye taxa. The level of global cytosine methylation in the DNA was not significantly associated with the content of t-heterochromatin and did not overlap with the existing taxonomic rye relationships. The highest content of 5-methylcytosine was found in S. cereale ssp. segetale (83%), while very low in S. strictum ssp. strictum (53%), which was significantly different from the methylation state of all taxa, except for S. sylvestre. The other studied taxa of rye had a similar level of methylated cytosine ranging from 66.42% (S. vavilovii) to 74.41% in (S. cereale ssp. afghanicum). The results obtained in this study are evidence that the percentage of methylated cytosine cannot be inferred solely based on the genome size or t-heterochromatin. This is a significantly more complex issue.
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Affiliation(s)
- Anna Kalinka
- Department of Cell Biology, Faculty of Biology, University of Szczecin, Szczecin, Poland; Molecular Biology and Biotechnology Center, Faculty of Biology, University of Szczecin, Szczecin, Poland
| | - Magdalena Achrem
- Department of Cell Biology, Faculty of Biology, University of Szczecin, Szczecin, Poland; Molecular Biology and Biotechnology Center, Faculty of Biology, University of Szczecin, Szczecin, Poland
| | - Paulina Poter
- Department of Cell Biology, Faculty of Biology, University of Szczecin , Szczecin , Poland
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Gorelick R, Carpinone J, Derraugh LJ. No universal differences between female and male eukaryotes: anisogamy and asymmetrical female meiosis. Biol J Linn Soc Lond 2016. [DOI: 10.1111/bij.12874] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Root Gorelick
- Department of Biology; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
- School of Mathematics & Statistics and Institute of Interdisciplinary Studies; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
| | - Jessica Carpinone
- Department of Biology; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
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Ellison A, Rodríguez López CM, Moran P, Breen J, Swain M, Megias M, Hegarty M, Wilkinson M, Pawluk R, Consuegra S. Epigenetic regulation of sex ratios may explain natural variation in self-fertilization rates. Proc Biol Sci 2016; 282:rspb.2015.1900. [PMID: 26559950 DOI: 10.1098/rspb.2015.1900] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Self-fertilization (selfing) favours reproductive success when mate availability is low, but renders populations more vulnerable to environmental change by reducing genetic variability. A mixed-breeding strategy (alternating selfing and outcrossing) may allow species to balance these needs, but requires a system for regulating sexual identity. We explored the role of DNA methylation as a regulatory system for sex-ratio modulation in the mixed-mating fish Kryptolebias marmoratus. We found a significant interaction between sexual identity (male or hermaphrodite), temperature and methylation patterns when two selfing lines were exposed to different temperatures during development. We also identified several genes differentially methylated in males and hermaphrodites that represent candidates for the temperature-mediated sex regulation in K. marmoratus. We conclude that an epigenetic mechanism regulated by temperature modulates sexual identity in this selfing species, providing a potentially widespread mechanism by which environmental change may influence selfing rates. We also suggest that K. marmoratus, with naturally inbred populations, represents a good vertebrate model for epigenetic studies.
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Affiliation(s)
- Amy Ellison
- IBERS, Aberystwyth University, Penglais Campus, Aberystwyth SY23 3DA, UK
| | | | - Paloma Moran
- Facultad de Biología, Universidad de Vigo, Vigo 36310, Spain
| | - James Breen
- School of Agriculture, Wine and Food, University of Adelaide, Adelaide 5005, Australia
| | - Martin Swain
- IBERS, Aberystwyth University, Penglais Campus, Aberystwyth SY23 3DA, UK
| | - Manuel Megias
- Facultad de Biología, Universidad de Vigo, Vigo 36310, Spain
| | - Matthew Hegarty
- IBERS, Aberystwyth University, Penglais Campus, Aberystwyth SY23 3DA, UK
| | - Mike Wilkinson
- School of Agriculture, Wine and Food, University of Adelaide, Adelaide 5005, Australia
| | - Rebecca Pawluk
- Department of Biosciences, College of Science, Swansea University, Swansea SA2 8PP, UK
| | - Sofia Consuegra
- IBERS, Aberystwyth University, Penglais Campus, Aberystwyth SY23 3DA, UK Department of Biosciences, College of Science, Swansea University, Swansea SA2 8PP, UK
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Consuegra S, Rodríguez López CM. Epigenetic-induced alterations in sex-ratios in response to climate change: An epigenetic trap? Bioessays 2016; 38:950-8. [PMID: 27548838 DOI: 10.1002/bies.201600058] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We hypothesize that under the predicted scenario of climate change epigenetically mediated environmental sex determination could become an epigenetic trap. Epigenetically regulated environmental sex determination is a mechanism by which species can modulate their breeding strategies to accommodate environmental change. Growing evidence suggests that epigenetic mechanisms may play a key role in phenotypic plasticity and in the rapid adaptation of species to environmental change, through the capacity of organisms to maintain a non-genetic plastic memory of the environmental and ecological conditions experienced by their parents. However, inherited epigenetic variation could also be maladaptive, becoming an epigenetic trap. This is because environmental sex determination can alter sex ratios by increasing the survival of one of the sexes at the expense of negative fitness consequences for the other, which could lead not only to the collapse of natural populations, but also have an impact in farmed animal and plant species.
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Affiliation(s)
- Sofia Consuegra
- Department of Biosciences, College of Science, Swansea University, Swansea, UK.
| | - Carlos M Rodríguez López
- Environmental Epigenetics and Genetics Group, School of Agriculture, University of Adelaide, Glen Osmond, South Australia, Australia.
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Wright AE, Dean R, Zimmer F, Mank JE. How to make a sex chromosome. Nat Commun 2016; 7:12087. [PMID: 27373494 PMCID: PMC4932193 DOI: 10.1038/ncomms12087] [Citation(s) in RCA: 160] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 05/27/2016] [Indexed: 12/19/2022] Open
Abstract
Sex chromosomes can evolve once recombination is halted between a homologous pair of chromosomes. Owing to detailed studies using key model systems, we have a nuanced understanding and a rich review literature of what happens to sex chromosomes once recombination is arrested. However, three broad questions remain unanswered. First, why do sex chromosomes stop recombining in the first place? Second, how is recombination halted? Finally, why does the spread of recombination suppression, and therefore the rate of sex chromosome divergence, vary so substantially across clades? In this review, we consider each of these three questions in turn to address fundamental questions in the field, summarize our current understanding, and highlight important areas for future work. Sex chromosome evolution begins when recombination between a homologous pair of chromosomes is halted. Here, Wright et al. review our current understanding of the causes and mechanisms of recombination suppression between incipient sex chromosomes and suggest future directions for the field.
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Affiliation(s)
- Alison E. Wright
- Department of Genetics, Evolution and Environment University College London, London WC1E 6BT UK
| | - Rebecca Dean
- Department of Genetics, Evolution and Environment University College London, London WC1E 6BT UK
| | - Fabian Zimmer
- Department of Genetics, Evolution and Environment University College London, London WC1E 6BT UK
| | - Judith E. Mank
- Department of Genetics, Evolution and Environment University College London, London WC1E 6BT UK
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Gorelick R, Fraser D, Mansfield M, Dawson JW, Wijenayake S, Bertram SM. Abrupt shortening of bird W chromosomes in ancestral Neognathae. Biol J Linn Soc Lond 2016. [DOI: 10.1111/bij.12832] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Root Gorelick
- Department of Biology; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
- School of Mathematics & Statistics and Institute of Interdisciplinary Studies; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
| | - Danielle Fraser
- Department of Biology; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
| | - Melissa Mansfield
- Department of Biology; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
| | - Jeff W. Dawson
- Department of Biology; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
| | - Sanoji Wijenayake
- Department of Biology; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
| | - Susan M. Bertram
- Department of Biology; Carleton University; 1125 Raven Road Ottawa Ontario K1S 5B6 Canada
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Jiang Q, Li Q, Yu H, Kong L. Inheritance and Variation of Genomic DNA Methylation in Diploid and Triploid Pacific Oyster (Crassostrea gigas). MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2016; 18:124-132. [PMID: 26585587 DOI: 10.1007/s10126-015-9674-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 10/06/2015] [Indexed: 06/05/2023]
Abstract
DNA methylation is an important epigenetic mechanism that could be responsive to environmental changes indicating a potential role in natural selection and adaption. In order to evaluate an evolutionary role of DNA methylation, it is essential to first gain a better insight into inheritability. To address this question, this study investigated DNA methylation variation from parents to offspring in the Pacific oyster Crassostrea gigas using fluorescent-labeled methylation-sensitive amplified polymorphism (F-MSAP) analysis. Most of parental methylated loci were stably transmitted to offspring segregating following Medelian expectation. However, methylated loci deviated more often than non-methylated loci and offspring showed a few de novo methylated loci indicating DNA methylation changes from parents to offspring. Interestingly, some male-specific methylated loci were found in this study which might help to explore sex determination in oyster. Despite environmental stimuli, genomic stresses such as polyploidization also can induce methylation changes. This study also compared global DNA methylation level and individual methylated loci between diploid and triploid oysters. Results showed no difference in global methylation state but a few ploidy-specific loci were detected. DNA methylation variation during polyploidization was less than autonomous methylation variation from parents to offspring.
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Affiliation(s)
- Qun Jiang
- The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, 266003, China
| | - Qi Li
- The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, 266003, China.
| | - Hong Yu
- The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, 266003, China
| | - Lingfeng Kong
- The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao, 266003, China
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33
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Characterization and expression of cyp19a gene in the Chinese giant salamander Andrias davidianus. Comp Biochem Physiol B Biochem Mol Biol 2016; 192:21-9. [DOI: 10.1016/j.cbpb.2015.11.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 11/05/2015] [Accepted: 11/11/2015] [Indexed: 12/25/2022]
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Du S, Sang Y, Liu X, Xing S, Li J, Tang H, Sun L. Transcriptome Profile Analysis from Different Sex Types of Ginkgo biloba L. FRONTIERS IN PLANT SCIENCE 2016; 7:871. [PMID: 27379148 PMCID: PMC4910463 DOI: 10.3389/fpls.2016.00871] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 06/02/2016] [Indexed: 05/21/2023]
Abstract
In plants, sex determination is a comprehensive process of correlated events, which involves genes that are differentially and/or specifically expressed in distinct developmental phases. Exploring gene expression profiles from different sex types will contribute to fully understanding sex determination in plants. In this study, we conducted RNA-sequencing of female and male buds (FB and MB) as well as ovulate strobilus and staminate strobilus (OS and SS) of Ginkgo biloba to gain insights into the genes potentially related to sex determination in this species. Approximately 60 Gb of clean reads were obtained from eight cDNA libraries. De novo assembly of the clean reads generated 108,307 unigenes with an average length of 796 bp. Among these unigenes, 51,953 (47.97%) had at least one significant match with a gene sequence in the public databases searched. A total of 4709 and 9802 differentially expressed genes (DEGs) were identified in MB vs. FB and SS vs. OS, respectively. Genes involved in plant hormone signal and transduction as well as those encoding DNA methyltransferase were found to be differentially expressed between different sex types. Their potential roles in sex determination of G. biloba were discussed. Pistil-related genes were expressed in male buds while anther-specific genes were identified in female buds, suggesting that dioecism in G. biloba was resulted from the selective arrest of reproductive primordia. High correlation of expression level was found between the RNA-Seq and quantitative real-time PCR results. The transcriptome resources that we generated allowed us to characterize gene expression profiles and examine differential expression profiles, which provided foundations for identifying functional genes associated with sex determination in G. biloba.
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35
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Trukhina AV, Lukina NA, Nekrasova AA, Smirnov AF. Sex inversion and epigenetic regulation in vertebrates. RUSS J GENET+ 2015. [DOI: 10.1134/s1022795415020155] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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36
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37
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Alonso C, Pérez R, Bazaga P, Herrera CM. Global DNA cytosine methylation as an evolving trait: phylogenetic signal and correlated evolution with genome size in angiosperms. Front Genet 2015; 6:4. [PMID: 25688257 PMCID: PMC4310347 DOI: 10.3389/fgene.2015.00004] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 01/07/2015] [Indexed: 01/17/2023] Open
Abstract
DNA cytosine methylation is a widespread epigenetic mechanism in eukaryotes, and plant genomes commonly are densely methylated. Genomic methylation can be associated with functional consequences such as mutational events, genomic instability or altered gene expression, but little is known on interspecific variation in global cytosine methylation in plants. In this paper, we compare global cytosine methylation estimates obtained by HPLC and use a phylogenetically-informed analytical approach to test for significance of evolutionary signatures of this trait across 54 angiosperm species in 25 families. We evaluate whether interspecific variation in global cytosine methylation is statistically related to phylogenetic distance and also whether it is evolutionarily correlated with genome size (C-value). Global cytosine methylation varied widely between species, ranging between 5.3% (Arabidopsis) and 39.2% (Narcissus). Differences between species were related to their evolutionary trajectories, as denoted by the strong phylogenetic signal underlying interspecific variation. Global cytosine methylation and genome size were evolutionarily correlated, as revealed by the significant relationship between the corresponding phylogenetically independent contrasts. On average, a ten-fold increase in genome size entailed an increase of about 10% in global cytosine methylation. Results show that global cytosine methylation is an evolving trait in angiosperms whose evolutionary trajectory is significantly linked to changes in genome size, and suggest that the evolutionary implications of epigenetic mechanisms are likely to vary between plant lineages.
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Affiliation(s)
| | - Ricardo Pérez
- Instituto de Investigaciones Químicas, Centro de Investigaciones Científicas Isla de La Cartuja, CSIC-US Sevilla, Spain
| | - Pilar Bazaga
- Estación Biológica de Doñana, CSIC Sevilla, Spain
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38
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Abstract
Sex chromosomes are the most dynamic entity in any genome having unique morphology, gene content, and evolution. They have evolved multiple times and independently throughout vertebrate evolution. One of the major genomic changes that pertain to sex chromosomes involves the amplification of common repeats. It is hypothesized that such amplification of repeats facilitates the suppression of recombination, leading to the evolution of heteromorphic sex chromosomes through genetic degradation of Y or W chromosomes. Although contrasting evidence is available, it is clear that amplification of simple repetitive sequences played a major role in the evolution of Y and W chromosomes in vertebrates. In this review, we present a brief overview of the repetitive DNA classes that accumulated during sex chromosome evolution, mainly focusing on vertebrates, and discuss their possible role and potential function in this process.
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39
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Shen ZG, Wang HP. Molecular players involved in temperature-dependent sex determination and sex differentiation in Teleost fish. Genet Sel Evol 2014; 46:26. [PMID: 24735220 PMCID: PMC4108122 DOI: 10.1186/1297-9686-46-26] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2013] [Accepted: 03/24/2014] [Indexed: 12/11/2022] Open
Abstract
The molecular mechanisms that underlie sex determination and differentiation are conserved and diversified. In fish species, temperature-dependent sex determination and differentiation seem to be ubiquitous and molecular players involved in these mechanisms may be conserved. Although how the ambient temperature transduces signals to the undifferentiated gonads remains to be elucidated, the genes downstream in the sex differentiation pathway are shared between sex-determining mechanisms. In this paper, we review recent advances on the molecular players that participate in the sex determination and differentiation in fish species, by putting emphasis on temperature-dependent sex determination and differentiation, which include temperature-dependent sex determination and genetic sex determination plus temperature effects. Application of temperature-dependent sex differentiation in farmed fish and the consequences of temperature-induced sex reversal are discussed.
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Affiliation(s)
| | - Han-Ping Wang
- Aquaculture Genetics and Breeding Laboratory, The Ohio State University South Centers, Piketon, Ohio 45661, USA.
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40
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Aryal R, Ming R. Sex determination in flowering plants: papaya as a model system. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2014; 217-218:56-62. [PMID: 24467896 DOI: 10.1016/j.plantsci.2013.10.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Revised: 10/28/2013] [Accepted: 10/29/2013] [Indexed: 05/23/2023]
Abstract
Unisexuality in flowering plants evolved from a hermaphrodite ancestor. Transition from hermaphrodite to unisexual flowers has occurred multiple times across the different lineages of the angiosperms. Sexuality in plants is regulated by genetic, epigenetic and physiological mechanisms. The most specialized mechanism of sex determination is sex chromosomes. The sex chromosomes ensure the stable segregation of sexual phenotypes by preventing the recombination of sex determining genes. Despite continuous efforts, sex determining genes of dioecious plants have not yet been cloned. Concerted efforts with various model systems are necessary to understand the complex mechanism of sex determination in plants. Papaya (Carica papaya L.) is a tropical fruit tree with three sex forms, male, hermaphrodite, and female. Sexuality in papaya is determined by an XY chromosome system that is in an early evolutionary stage. The male and hermaphrodite of papaya are controlled by two different types of Y chromosomes: Y and Y(h). Large amounts of information in the area of genetics, genomics, and epigenetics of papaya have been accumulated over the last few decades. Relatively short lifecycle, small genome size, and readily available genetic and genomic resources render papaya an excellent model system to study sex determination and sex chromosomes in flowering plants.
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Affiliation(s)
- Rishi Aryal
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
| | - Ray Ming
- Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; FAFU and UIUC-SIB Joint Center for Genomics and Biotechnology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China.
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41
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Parrott BB, Kohno S, Cloy-McCoy JA, Guillette LJ. Differential incubation temperatures result in dimorphic DNA methylation patterning of the SOX9 and aromatase promoters in gonads of alligator (Alligator mississippiensis) embryos. Biol Reprod 2014; 90:2. [PMID: 24227754 DOI: 10.1095/biolreprod.113.111468] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Environmental factors are known to influence sex determination in many nonmammalian vertebrates. In all crocodilians studied thus far, temperature is the only known determinant of sex. However, the molecular mechanisms mediating the effect of temperature on sex determination are not known. Aromatase (CYP19A1) and SOX9 play critical roles in vertebrate sex determination and gonadogenesis. Here, we used a variety of techniques to investigate the potential roles of DNA methylation patterning on CYP19A1 and SOX9 expression in the American alligator, an organism that relies on temperature-dependent sex determination. Our findings reveal that developing gonads derived from embryos incubated at a male-producing temperature (MPT) show elevated CYP19A1 promoter methylation and decreased levels of gene expression relative to incubation at a female-producing temperature (FPT). The converse was observed at the SOX9 locus, with increased promoter methylation and decreased expression occurring in embryonic gonads resulting from incubation at FPT relative to that of MPT. We also examined the gonadal expression of the three primary, catalytically active DNA methyltransferase enzymes and show that they are present during critical stages of gonadal development. Together, these data strongly suggest that DNA methylation patterning is a central component in coordinating the genetic cascade responsible for sexual differentiation. In addition, these data raise the possibility that DNA methylation could act as a key mediator integrating temperature into a molecular trigger that determines sex in the alligator.
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Affiliation(s)
- Benjamin B Parrott
- Department of Obstetrics and Gynecology, Medical University of South Carolina, and Hollings Marine Laboratory, Charleston, South Carolina
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Ashman TL, Kwok A, Husband BC. Revisiting the dioecy-polyploidy association: alternate pathways and research opportunities. Cytogenet Genome Res 2013; 140:241-55. [PMID: 23838528 DOI: 10.1159/000353306] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The evolutionary transition from hermaphroditism (combined sexes) to dioecy (separate sexes) is associated with whole genome duplication (polyploidy) in several flowering plant genera. Moreover, there is evidence for transitions in the opposite direction, i.e. a loss of dioecy with an increase in ploidy. Here, we review evidence for these associations, synthesize previous ideas on the mechanism underlying the patterns and explore alternative pathways. Specifically, we examine potential ecological and genetic mechanisms, differentiated by whether ploidy or gender (functional sex expression of the plant) changes are the primary cause and whether the effect is direct or indirect. An analysis of 22 genera variable for both ploidy and gender indicates that gender monomorphism (hermaphroditism, monoecy) is more common among diploid than polyploid species, whereas gender dimorphism (dioecy, gynodioecy, subdioecy) is more frequent among polyploid species. The transition from diploid hermaphroditic to polyploid gender-dimorphic taxa may arise directly through changes in gender as a result of genome duplication through genomic rearrangements or homeologous recombination, or changes in gender may result in increased unreduced gamete production leading to polyploid formation. Alternatively, the transition may occur through the indirect effects of genome duplication on mating system and inbreeding depression, which favor selection for unisexuality, or habitat shifts associated with unisexuality may simultaneously cause increased unreduced gamete production. Novel mechanisms for transitions in the opposite direction (from dioecy to hermaphroditism with increase in ploidy) include disruption of genetic sex determination and the benefits of reproductive assurance. We highlight key questions requiring further attention and promising approaches for answering them and better clarifying the genesis of sexual system polyploidy associations. See also the sister article focusing on animals by Wertheim et al. in this themed issue.
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Affiliation(s)
- T-L Ashman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260-3929, USA. tia1 @ pitt.edu
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GORELICK ROOT, OLSON KRYSTLE. Polyploidy Is Genetic Hence May Cause Non-Adaptive Radiations, Whereas Pseudopolyploidy Is Genomic Hence May Cause Adaptive Non-Radiations. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2013; 320:286-94. [DOI: 10.1002/jez.b.22499] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 03/12/2013] [Indexed: 12/21/2022]
Affiliation(s)
- ROOT GORELICK
- Department of Biology; Carleton University; Ottawa, Ontario Canada
- School of Mathematics and Statistics and Institute of Interdisciplinary Studies; Carleton University; Ottawa, Ontario Canada
| | - KRYSTLE OLSON
- Department of Biology; Carleton University; Ottawa, Ontario Canada
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44
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Piferrer F. Epigenetics of sex determination and gonadogenesis. Dev Dyn 2013; 242:360-70. [PMID: 23335256 DOI: 10.1002/dvdy.23924] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Revised: 12/27/2012] [Accepted: 12/27/2012] [Indexed: 01/22/2023] Open
Abstract
Epigenetics is commonly defined as the study of heritable changes in gene function that cannot be explained by changes in DNA sequence. The three major epigenetic mechanisms for gene expression regulation include DNA methylation, histone modifications, and non-coding RNAs. Epigenetic mechanisms provide organisms with the ability to integrate genomic and environmental information to modify the activity of their genes for generating a particular phenotype. During development, cells differentiate, acquire, and maintain identity through changes in gene expression. This is crucial for sex determination and differentiation, which are among the most important developmental processes for the proper functioning and perpetuation of species. This review summarizes studies showing how epigenetic regulatory mechanisms contribute to sex determination and reproductive organ formation in plants, invertebrates, and vertebrates. Further progress will be made by integrating several approaches, including genomics and Next Generation Sequencing to create epigenetic maps related to different aspects of sex determination and gonadogenesis. Epigenetics will also contribute to understand the etiology of several disorders of sexual development. It also might play a significant role in the control of reproduction in animal farm production and will aid in recognizing the environmental versus genetic influences on sex determination of sensitive species in a global change scenario.
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Affiliation(s)
- Francesc Piferrer
- Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain.
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45
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Piferrer F, Ribas L, Díaz N. Genomic approaches to study genetic and environmental influences on fish sex determination and differentiation. MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2012; 14:591-604. [PMID: 22544374 PMCID: PMC3419836 DOI: 10.1007/s10126-012-9445-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Accepted: 03/05/2012] [Indexed: 05/15/2023]
Abstract
The embryonic gonad is the only organ that takes two mutually exclusive differentiating pathways and hence gives rise to two different adult organs: testes or ovaries. The recent application of genomic tools including microarrays, next-generation sequencing approaches, and epigenetics can significantly contribute to decipher the molecular mechanisms involved in the processes of sex determination and sex differentiation. However, in fish, these studies are complicated by the fact that these processes depend, perhaps to a larger extent when compared to other vertebrates, on the interplay of genetic and environmental influences. Here, we review the advances made so far, taking into account different experimental approaches, and illustrate some technical complications deriving from the fact that as development progresses it becomes more and more difficult to distinguish whether changes in gene expression or DNA methylation patterns are the cause or the consequence of such developmental events. Finally, we suggest some avenues for further research in both model fish species and fish species facing specific problems within an aquaculture context.
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Affiliation(s)
- Francesc Piferrer
- Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas, Passeig Marítim 37-49, Barcelona, Spain.
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Njuguna W, Liston A, Cronn R, Ashman TL, Bassil N. Insights into phylogeny, sex function and age of Fragaria based on whole chloroplast genome sequencing. Mol Phylogenet Evol 2012; 66:17-29. [PMID: 22982444 DOI: 10.1016/j.ympev.2012.08.026] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 08/20/2012] [Accepted: 08/30/2012] [Indexed: 01/25/2023]
Abstract
The cultivated strawberry is one of the youngest domesticated plants, developed in France in the 1700s from chance hybridization between two western hemisphere octoploid species. However, little is known about the evolution of the species that gave rise to this important fruit crop. Phylogenetic analysis of chloroplast genome sequences of 21 Fragaria species and subspecies resolves the western North American diploid F. vesca subsp. bracteata as sister to the clade of octoploid/decaploid species. No extant tetraploids or hexaploids are directly involved in the maternal ancestry of the octoploids. There is strong geographic segregation of chloroplast haplotypes in subsp. bracteata, and the gynodioecious Pacific Coast populations are implicated as both the maternal lineage and the source of male-sterility in the octoploid strawberries. Analysis of sexual system evolution in Fragaria provides evidence that the loss of male and female function can follow polyploidization, but does not seem to be associated with loss of self-incompatibility following genome doubling. Character-state mapping provided insight into sexual system evolution and its association with loss of self-incompatibility and genome doubling/merger. Fragaria attained its circumboreal and amphitropical distribution within the past one to four million years and the rise of the octoploid clade is dated at 0.372-2.05 million years ago.
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Affiliation(s)
- Wambui Njuguna
- Department of Horticulture, Oregon State University, ALS 4017, Corvallis, OR 97331, USA.
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Spigler RB, Ashman TL. Gynodioecy to dioecy: are we there yet? ANNALS OF BOTANY 2012; 109:531-43. [PMID: 21807691 PMCID: PMC3278288 DOI: 10.1093/aob/mcr170] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Accepted: 05/05/2011] [Indexed: 05/08/2023]
Abstract
BACKGROUND The 'gynodioecy-dioecy pathway' is considered to be one of the most important evolutionary routes from hermaphroditism to separate sexes (dioecy). Despite a large accumulation of evidence for female seed fertility advantages in gynodioecious species (females and hermaphrodites coexist) in support of the first step in the gynodioecy-dioecy pathway, we still have very little evidence for the second step, i.e. the transition from gynodioecy to dioecy. SCOPE We review the literature to evaluate whether basic predictions by theory are supported. To establish whether females' seed fertility advantage and frequencies are sufficient to favour the invasion of males, we review these for species along the gynodioecy-dioecy pathway published in the last 5 years. We then review the empirical evidence for predictions deriving from the second step, i.e. hermaphrodites' male fertility increases with female frequency, selection favours greater male fertility in hermaphrodites in gynodioecious species, and, where males and hermaphrodites coexist with females (subdioecy), males have greater male fertility than hermaphrodites. We review how genetic control and certain ecological features (pollen limitation, selfing, plasticity in sex expression and antagonists) influence the trajectory of a population along the gynodioecy-dioecy pathway. CONCLUSIONS Females tend to have greater seed fertility advantages over hermaphrodites where the two coexist, and this advantage is positively correlated with female frequency across species, as predicted by theory. A limited number of studies in subdioecious species have demonstrated that males have an advantage over hermaphrodites, as also predicted by theory. However, less evidence exists for phenotypic selection to increase male traits of hermaphrodites or for increasing male function of hermaphrodites in populations with high female frequency. A few key case studies underline the importance of examining multiple components of male fertility and the roles of pollen limitation, selfing and plasticity, when evaluating advantages. We conclude that we do not yet have a full understanding of the transition from gynodioecy to dioecy.
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Affiliation(s)
| | - Tia-Lynn Ashman
- Department of Biological Sciences, 4249 Fifth Ave., University of Pittsburgh, Pittsburgh, PA 15260-3929, USA
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Navarro-Martín L, Viñas J, Ribas L, Díaz N, Gutiérrez A, Di Croce L, Piferrer F. DNA methylation of the gonadal aromatase (cyp19a) promoter is involved in temperature-dependent sex ratio shifts in the European sea bass. PLoS Genet 2011; 7:e1002447. [PMID: 22242011 PMCID: PMC3248465 DOI: 10.1371/journal.pgen.1002447] [Citation(s) in RCA: 310] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Accepted: 11/16/2011] [Indexed: 11/18/2022] Open
Abstract
Sex ratio shifts in response to temperature are common in fish and reptiles. However, the mechanism linking temperature during early development and sex ratios has remained elusive. We show in the European sea bass (sb), a fish in which temperature effects on sex ratios are maximal before the gonads form, that juvenile males have double the DNA methylation levels of females in the promoter of gonadal aromatase (cyp19a), the enzyme that converts androgens into estrogens. Exposure to high temperature increased the cyp19a promoter methylation levels of females, indicating that induced-masculinization involves DNA methylation-mediated control of aromatase gene expression, with an observed inverse relationship between methylation levels and expression. Although different CpGs within the sb cyp19a promoter exhibited different sensitivity to temperature, we show that the increased methylation of the sb cyp19a promoter, which occurs in the gonads but not in the brain, is not a generalized effect of temperature. Importantly, these effects were also observed in sexually undifferentiated fish and were not altered by estrogen treatment. Thus, methylation of the sb cyp19a promoter is the cause of the lower expression of cyp19a in temperature-masculinized fish. In vitro, induced methylation of the sb cyp19a promoter suppressed the ability of SF-1 and Foxl2 to stimulate transcription. Finally, a CpG differentially methylated by temperature and adjacent to a Sox transcription factor binding site is conserved across species. Thus, DNA methylation of the aromatase promoter may be an essential component of the long-sought-after mechanism connecting environmental temperature and sex ratios in vertebrate species with temperature-dependent sex determination.
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Affiliation(s)
- Laia Navarro-Martín
- Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Jordi Viñas
- Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Laia Ribas
- Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Noelia Díaz
- Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Arantxa Gutiérrez
- Centre de Regulació Genòmica (CRG)/ICREA and Univeristat Pompeu Fabra (UPF), Barcelona, Spain
| | - Luciano Di Croce
- Centre de Regulació Genòmica (CRG)/ICREA and Univeristat Pompeu Fabra (UPF), Barcelona, Spain
| | - Francesc Piferrer
- Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
- * E-mail:
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Comparative genetic mapping points to different sex chromosomes in sibling species of wild strawberry (Fragaria). Genetics 2010; 186:1425-33. [PMID: 20923978 DOI: 10.1534/genetics.110.122911] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Separate sexes have evolved repeatedly from hermaphroditic ancestors in flowering plants, and thus select taxa can provide unparalleled insight into the evolutionary dynamics of sex chromosomes that are thought to be shared by plants and animals alike. Here we ask whether two octoploid sibling species of wild strawberry--one almost exclusively dioecious (males and females), Fragaria chiloensis, and one subdioecious (males, females, and hermaphrodites), F. virginiana--share the same sex-determining chromosome. We created a genetic map of the sex chromosome and its homeologs in F. chiloensis and assessed macrosynteny between it and published maps of the proto-sex chromosome of F. virginiana and the homeologous autosome of hermaphroditic diploid species. Segregation of male and female function in our F. chiloensis mapping population confirmed that linkage and dominance relations are similar to those in F. virginiana. However, identification of the molecular markers most tightly linked to the sex-determining locus in the two octoploid species shows that, in both, this region maps to homeologues of chromosome 6 in diploid congeners, but is located at opposite ends of their respective chromosomes.
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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: 0.8] [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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