1
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Zhu Z, Younas L, Zhou Q. Evolution and regulation of animal sex chromosomes. Nat Rev Genet 2024:10.1038/s41576-024-00757-3. [PMID: 39026082 DOI: 10.1038/s41576-024-00757-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2024] [Indexed: 07/20/2024]
Abstract
Animal sex chromosomes typically carry the upstream sex-determining gene that triggers testis or ovary development and, in some species, are regulated by global dosage compensation in response to functional decay of the Y chromosome. Despite the importance of these pathways, they exhibit striking differences across species, raising fundamental questions regarding the mechanisms underlying their evolutionary turnover. Recent studies of non-model organisms, including insects, reptiles and teleosts, have yielded a broad view of the diversity of sex chromosomes that challenges established theories. Moreover, continued studies in model organisms with recently developed technologies have characterized the dynamics of sex determination and dosage compensation in three-dimensional nuclear space and at single-cell resolution. Here, we synthesize recent insights into sex chromosomes from a variety of species to review their evolutionary dynamics with respect to the canonical model, as well as their diverse mechanisms of regulation.
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Affiliation(s)
- Zexian Zhu
- Evolutionary and Organismal Biology Research Center and Women's Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Lubna Younas
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna, Austria
| | - Qi Zhou
- The MOE Key Laboratory of Biosystems Homeostasis & Protection and Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang, China.
- State Key Laboratory of Transvascular Implantation Devices, The 2nd Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China.
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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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Sacchi B, Humphries Z, Kružlicová J, Bodláková M, Pyne C, Choudhury BI, Gong Y, Bačovský V, Hobza R, Barrett SCH, Wright SI. Phased Assembly of Neo-Sex Chromosomes Reveals Extensive Y Degeneration and Rapid Genome Evolution in Rumex hastatulus. Mol Biol Evol 2024; 41:msae074. [PMID: 38606901 PMCID: PMC11057207 DOI: 10.1093/molbev/msae074] [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: 10/06/2023] [Revised: 01/31/2024] [Accepted: 04/05/2024] [Indexed: 04/13/2024] Open
Abstract
Y chromosomes are thought to undergo progressive degeneration due to stepwise loss of recombination and subsequent reduction in selection efficiency. However, the timescales and evolutionary forces driving degeneration remain unclear. To investigate the evolution of sex chromosomes on multiple timescales, we generated a high-quality phased genome assembly of the massive older (<10 MYA) and neo (<200,000 yr) sex chromosomes in the XYY cytotype of the dioecious plant Rumex hastatulus and a hermaphroditic outgroup Rumex salicifolius. Our assemblies, supported by fluorescence in situ hybridization, confirmed that the neo-sex chromosomes were formed by two key events: an X-autosome fusion and a reciprocal translocation between the homologous autosome and the Y chromosome. The enormous sex-linked regions of the X (296 Mb) and two Y chromosomes (503 Mb) both evolved from large repeat-rich genomic regions with low recombination; however, the complete loss of recombination on the Y still led to over 30% gene loss and major rearrangements. In the older sex-linked region, there has been a significant increase in transposable element abundance, even into and near genes. In the neo-sex-linked regions, we observed evidence of extensive rearrangements without gene degeneration and loss. Overall, we inferred significant degeneration during the first 10 million years of Y chromosome evolution but not on very short timescales. Our results indicate that even when sex chromosomes emerge from repetitive regions of already-low recombination, the complete loss of recombination on the Y chromosome still leads to a substantial increase in repetitive element content and gene degeneration.
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Affiliation(s)
- Bianca Sacchi
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
| | - Zoë Humphries
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
| | - Jana Kružlicová
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Markéta Bodláková
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic
| | - Cassandre Pyne
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
| | - Baharul I Choudhury
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
- Department of Biology, Queen’s University, Kingston, Canada
| | - Yunchen Gong
- Centre for Analysis of Genome Evolution and Function, University of Toronto, Toronto, Canada
| | - Václav Bačovský
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic
| | - Roman Hobza
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic
| | - Spencer C H Barrett
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
| | - Stephen I Wright
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
- Centre for Analysis of Genome Evolution and Function, University of Toronto, Toronto, Canada
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4
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Duhamel M, Hood ME, Rodríguez de la Vega RC, Giraud T. Dynamics of transposable element accumulation in the non-recombining regions of mating-type chromosomes in anther-smut fungi. Nat Commun 2023; 14:5692. [PMID: 37709766 PMCID: PMC10502011 DOI: 10.1038/s41467-023-41413-4] [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: 12/23/2022] [Accepted: 08/30/2023] [Indexed: 09/16/2023] Open
Abstract
In the absence of recombination, the number of transposable elements (TEs) increases due to less efficient selection, but the dynamics of such TE accumulations are not well characterized. Leveraging a dataset of 21 independent events of recombination cessation of different ages in mating-type chromosomes of Microbotryum fungi, we show that TEs rapidly accumulated in regions lacking recombination, but that TE content reached a plateau at ca. 50% of occupied base pairs by 1.5 million years following recombination suppression. The same TE superfamilies have expanded in independently evolved non-recombining regions, in particular rolling-circle replication elements (Helitrons). Long-terminal repeat (LTR) retrotransposons of the Copia and Ty3 superfamilies also expanded, through transposition bursts (distinguished from gene conversion based on LTR divergence), with both non-recombining regions and autosomes affected, suggesting that non-recombining regions constitute TE reservoirs. This study improves our knowledge of genome evolution by showing that TEs can accumulate through bursts, following non-linear decelerating dynamics.
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Affiliation(s)
- Marine Duhamel
- Ecologie Systématique Evolution, IDEEV, CNRS, Université Paris-Saclay, AgroParisTech, Bâtiment 680, 12 route RD128, 91190, Gif-sur-Yvette, France.
- Evolution der Pflanzen und Pilze, Ruhr-Universität Bochum, Universitätsstraße 150, 44780, Bochum, Germany.
| | - Michael E Hood
- Department of Biology, Amherst College, 01002-5000, Amherst, MA, USA
| | - Ricardo C Rodríguez de la Vega
- Ecologie Systématique Evolution, IDEEV, CNRS, Université Paris-Saclay, AgroParisTech, Bâtiment 680, 12 route RD128, 91190, Gif-sur-Yvette, France
| | - Tatiana Giraud
- Ecologie Systématique Evolution, IDEEV, CNRS, Université Paris-Saclay, AgroParisTech, Bâtiment 680, 12 route RD128, 91190, Gif-sur-Yvette, France
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5
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Fawcett JA, Takeshima R, Kikuchi S, Yazaki E, Katsube-Tanaka T, Dong Y, Li M, Hunt HV, Jones MK, Lister DL, Ohsako T, Ogiso-Tanaka E, Fujii K, Hara T, Matsui K, Mizuno N, Nishimura K, Nakazaki T, Saito H, Takeuchi N, Ueno M, Matsumoto D, Norizuki M, Shirasawa K, Li C, Hirakawa H, Ota T, Yasui Y. Genome sequencing reveals the genetic architecture of heterostyly and domestication history of common buckwheat. NATURE PLANTS 2023; 9:1236-1251. [PMID: 37563460 DOI: 10.1038/s41477-023-01474-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 07/03/2023] [Indexed: 08/12/2023]
Abstract
Common buckwheat, Fagopyrum esculentum, is an orphan crop domesticated in southwest China that exhibits heterostylous self-incompatibility. Here we present chromosome-scale assemblies of a self-compatible F. esculentum accession and a self-compatible wild relative, Fagopyrum homotropicum, together with the resequencing of 104 wild and cultivated F. esculentum accessions. Using these genomic data, we report the roles of transposable elements and whole-genome duplications in the evolution of Fagopyrum. In addition, we show that (1) the breakdown of heterostyly occurs through the disruption of a hemizygous gene jointly regulating the style length and female compatibility and (2) southeast Tibet was involved in common buckwheat domestication. Moreover, we obtained mutants conferring the waxy phenotype for the first time in buckwheat. These findings demonstrate the utility of our F. esculentum assembly as a reference genome and promise to accelerate buckwheat research and breeding.
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Affiliation(s)
| | - Ryoma Takeshima
- Institute of Crop Science, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
| | - Shinji Kikuchi
- Graduate School of Horticulture, Chiba University, Matsudo, Japan
- Plant Molecular Science Center, Chiba University, Chiba, Japan
| | | | | | - Yumei Dong
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan Agricultural University, Kunming, China
| | - Meifang Li
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan Agricultural University, Kunming, China
| | - Harriet V Hunt
- McDonald Institute for Archaeological Research, University of Cambridge, Cambridge, UK
- Royal Botanic Gardens Kew, Richmond, UK
| | - Martin K Jones
- McDonald Institute for Archaeological Research, University of Cambridge, Cambridge, UK
| | - Diane L Lister
- McDonald Institute for Archaeological Research, University of Cambridge, Cambridge, UK
- Conservation Research Institute, University of Cambridge, Cambridge, UK
| | - Takanori Ohsako
- Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan
| | - Eri Ogiso-Tanaka
- Institute of Crop Science, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
- Center for Molecular Biodiversity Research, National Museum of Nature and Science, Tsukuba, Japan
| | - Kenichiro Fujii
- Institute of Crop Science, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
| | - Takashi Hara
- Hokkaido Agricultural Research Center, National Agriculture and Food Research Organization (NARO), Kasai, Japan
| | - Katsuhiro Matsui
- Institute of Crop Science, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
- Institute of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Nobuyuki Mizuno
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | | | | | - Hiroki Saito
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
- Tropical Agriculture Research Front, Japan International Research Center for Agricultural Sciences, Ishigaki, Japan
| | - Naoko Takeuchi
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Mariko Ueno
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Daiki Matsumoto
- Faculty of Bioscience and Biotechnology, Fukui Prefectural University, Awara, Japan
| | - Miyu Norizuki
- Graduate School of Horticulture, Chiba University, Matsudo, Japan
| | | | - Chengyun Li
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan Agricultural University, Kunming, China.
| | | | - Tatsuya Ota
- Department of Evolutionary Studies of Biosystems, SOKENDAI, Hayama, Japan.
- Research Center for Integrative Evolutionary Science, SOKENDAI, Hayama, Japan.
| | - Yasuo Yasui
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
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6
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Yue J, Krasovec M, Kazama Y, Zhang X, Xie W, Zhang S, Xu X, Kan B, Ming R, Filatov DA. The origin and evolution of sex chromosomes, revealed by sequencing of the Silene latifolia female genome. Curr Biol 2023:S0960-9822(23)00678-4. [PMID: 37290443 DOI: 10.1016/j.cub.2023.05.046] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 04/07/2023] [Accepted: 05/19/2023] [Indexed: 06/10/2023]
Abstract
White campion (Silene latifolia, Caryophyllaceae) was the first vascular plant where sex chromosomes were discovered. This species is a classic model for studies on plant sex chromosomes due to presence of large, clearly distinguishable X and Y chromosomes that originated de novo about 11 million years ago (mya), but lack of genomic resources for this relatively large genome (∼2.8 Gb) remains a significant hurdle. Here we report S. latifolia female genome assembly integrated with sex-specific genetic maps of this species, focusing on sex chromosomes and their evolution. The analysis reveals a highly heterogeneous recombination landscape with strong reduction in recombination rate in the central parts of all chromosomes. Recombination on the X chromosome in female meiosis primarily occurs at the very ends, and over 85% of the X chromosome length is located in a massive (∼330 Mb) gene-poor, rarely recombining pericentromeric region (Xpr). The results indicate that the non-recombining region on the Y chromosome (NRY) initially evolved in a relatively small (∼15 Mb), actively recombining region at the end of the q-arm, possibly as a result of inversion on the nascent X chromosome. The NRY expanded about 6 mya via linkage between the Xpr and the sex-determining region, which may have been caused by expanding pericentromeric recombination suppression on the X chromosome. These findings shed light on the origin of sex chromosomes in S. latifolia and yield genomic resources to assist ongoing and future investigations into sex chromosome evolution.
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Affiliation(s)
- Jingjing Yue
- Centre for Genomics and Biotechnology, Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, Key Laboratory of Genetics, Breeding and Multiple Utilization of Crops, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Marc Krasovec
- Department of Biology, University of Oxford, Oxford OX1 3RB, UK; Sorbonne Université, CNRS, UMR 7232 Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, 66650 Banyuls-sur-Mer, France
| | - Yusuke Kazama
- Department of Bioscience and Biotechnology, Fukui Prefectural University, 4-1-1 Kenjojima, Matsuoka, Eiheiji-cho, Fukui 910-1195, Japan
| | - Xingtan Zhang
- Centre for Genomics and Biotechnology, Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, Key Laboratory of Genetics, Breeding and Multiple Utilization of Crops, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou 350002, China; Shenzhen Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518100, China
| | - Wangyang Xie
- Centre for Genomics and Biotechnology, Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, Key Laboratory of Genetics, Breeding and Multiple Utilization of Crops, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Shencheng Zhang
- Shenzhen Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518100, China
| | - Xiuming Xu
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, College of the Environment and Ecology, Xiamen University, Xiamen 361100, China
| | - Baolin Kan
- Centre for Genomics and Biotechnology, Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, Key Laboratory of Genetics, Breeding and Multiple Utilization of Crops, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Ray Ming
- Centre for Genomics and Biotechnology, Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, Key Laboratory of Genetics, Breeding and Multiple Utilization of Crops, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Dmitry A Filatov
- Department of Biology, University of Oxford, Oxford OX1 3RB, UK.
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7
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Koenemann DM, Kistler L, Burke JM. A plastome phylogeny of Rumex (Polygonaceae) illuminates the divergent evolutionary histories of docks and sorrels. Mol Phylogenet Evol 2023; 182:107755. [PMID: 36906194 DOI: 10.1016/j.ympev.2023.107755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 02/07/2023] [Accepted: 03/05/2023] [Indexed: 03/12/2023]
Abstract
The genus Rumex L. (Polygonaceae) provides a unique system for investigating the evolutionary development of sex determination and molecular rate evolution. Historically, Rumex has been divided, both taxonomically and colloquially into two groups: 'docks' and 'sorrels'. A well-resolved phylogeny can help evaluate a genetic basis for this division. Here we present a plastome phylogeny for 34 species of Rumex, inferred using maximum likelihood criteria. The historical 'docks' (Rumex subgenus Rumex) were resolved as monophyletic. The historical 'sorrels' (Rumex subgenera Acetosa and Acetosella) were resolved together, though not monophyletic due to the inclusion of R. bucephalophorus (Rumex subgenus Platypodium). Emex is supported as its own subgenus within Rumex, instead of resolved as sister taxa. We found remarkably low nucleotide diversity among the docks, consistent with recent diversification in that group, especially as compared to the sorrels. Fossil calibration of the phylogeny suggested that the common ancestor for Rumex (including Emex) has origins in the lower Miocene (22.13 MYA). The sorrels appear to have subsequently diversified at a relatively constant rate. The origin of the docks, however, was placed in the upper Miocene, but with most speciation occurring in the Plio-Pleistocene.
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Affiliation(s)
- Daniel M Koenemann
- Claflin University, Department of Biology, 400 Magnolia Street, Orangeburg, SC 29115, USA.
| | - Logan Kistler
- National Museum of Natural History, Anthropology Department, 10th Street & Constitution Avenue NW, Washington, DC 20560, USA.
| | - Janelle M Burke
- Howard University, Department of Biology, EE Just Hall, 415 College Street NW, Washington, DC 20059, USA.
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8
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Heterochiasmy and Sex Chromosome Evolution in Silene. Genes (Basel) 2023; 14:genes14030543. [PMID: 36980816 PMCID: PMC10048291 DOI: 10.3390/genes14030543] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 02/17/2023] [Accepted: 02/21/2023] [Indexed: 02/24/2023] Open
Abstract
The evolution of a non-recombining sex-specific region is a key step in sex chromosome evolution. Suppression of recombination between the (proto-) X- and Y-chromosomes in male meiosis creates a non-recombining Y-linked region (NRY), while the X-chromosome continues to recombine in females. Lack of recombination in the NRY defines its main properties—genetic degeneration and accumulation of repetitive DNA, making X and Y chromosomes very different from each other. How and why recombination suppression on sex chromosomes evolves remains controversial. A strong difference in recombination rates between the sexes (heterochiasmy) can facilitate or even cause recombination suppression. In the extreme case—complete lack of recombination in the heterogametic sex (achiasmy)—the entire sex-specific chromosome is automatically non-recombining. In this study, I analyse sex-specific recombination rates in a dioecious plant Silene latifolia (Caryophyllaceae), which evolved separate sexes and sex chromosomes ~11 million years ago. I reconstruct high-density RNAseq-based genetic maps including over five thousand genic markers for the two sexes separately. The comparison of the male and female maps reveals only modest heterochiasmy across the genome, with the exception of the sex chromosomes, where recombination is suppressed in males. This indicates that heterochiasmy likely played only a minor, if any, role in NRY evolution in S. latifolia, as recombination suppression is specific to NRY rather than to the entire genome in males. Other mechanisms such as structural rearrangements and/or epigenetic modifications were likely involved, and comparative genome analysis and genetic mapping in multiple Silene species will help to shed light on the mechanism(s) of recombination suppression that led to the evolution of sex chromosomes.
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9
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Beaudry FEG, Rifkin JL, Peake AL, Kim D, Jarvis-Cross M, Barrett SCH, Wright SI. Effects of the neo-X chromosome on genomic signatures of hybridization in Rumex hastatulus. Mol Ecol 2022; 31:3708-3721. [PMID: 35569016 DOI: 10.1111/mec.16496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 04/23/2022] [Accepted: 05/05/2022] [Indexed: 11/30/2022]
Abstract
Natural hybrid zones provide opportunities for studies of the evolution of reproductive isolation in wild populations. Although recent investigations have found that the formation of neo-sex chromosomes is associated with reproductive isolation, the mechanisms remain unclear in most cases. Here, we assess the contemporary structure of gene flow in the contact zone between largely allopatric cytotypes of the dioecious plant Rumex hastatulus, a species with evidence of sex chromosome turn-over. Males to the west of the Mississippi river, USA, have an X and a single Y chromosome, whereas populations to the east of the river have undergone a chromosomal rearrangement giving rise to a larger X and two Y chromosomes. Using reduced-representation sequencing, we provide evidence that hybrids form readily and survive multiple backcross generations in the field, demonstrating the potential for ongoing gene flow between the cytotypes. Cline analysis of each chromosome separately captured no signals of difference in cline shape between chromosomes. However, principal component regression revealed a significant increase in the contribution of individual SNPs to inter-cytotype differentiation on the neo-X chromosome, but no correlation with recombination rate. Cline analysis revealed that the only SNPs with significantly steeper clines than the genome average were located on the neo-X. Our data are consistent with a role for neo-sex chromosomes in reproductive isolation between R. hastatulus cytotypes. Our investigation highlights the importance of studying plant hybrid zones for understanding the evolution of sex chromosomes.
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Affiliation(s)
- Felix E G Beaudry
- The University of Toronto, Department of Ecology and Evolutionary Biology, Toronto, ON, Canada
| | - Joanna L Rifkin
- The University of Toronto, Department of Ecology and Evolutionary Biology, Toronto, ON, Canada
| | - Amanda L Peake
- The University of Toronto, Department of Ecology and Evolutionary Biology, Toronto, ON, Canada
| | - Deanna Kim
- The University of Toronto, Department of Ecology and Evolutionary Biology, Toronto, ON, Canada
| | - Madeline Jarvis-Cross
- The University of Toronto, Department of Ecology and Evolutionary Biology, Toronto, ON, Canada
| | - Spencer C H Barrett
- The University of Toronto, Department of Ecology and Evolutionary Biology, Toronto, ON, Canada
| | - Stephen I Wright
- The University of Toronto, Department of Ecology and Evolutionary Biology, Toronto, ON, Canada
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10
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Renner SS, Müller NA. Sex determination and sex chromosome evolution in land plants. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210210. [PMID: 35306895 PMCID: PMC8935313 DOI: 10.1098/rstb.2021.0210] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 01/19/2022] [Indexed: 01/02/2023] Open
Abstract
Linnaeus's very first opus, written when he was 22 years old, dealt with the analogy that exists between plants and animals in how they 'propagate their species', and a revised version with a plate depicting the union of male and female Mercurialis annua plants became a foundational text on the sexuality of plants. The question how systems with separate males and females have evolved in sedentary organisms that appear ancestrally bisexual has fascinated biologists ever since. The phenomenon, termed dioecy, has important consequences for plant reproductive success and is of commercial interest since it affects seed quality and fruit production. This theme issue presents a series of articles that synthesize and challenge the current understanding of how plants achieve dioecy. The articles deal with a broad set of taxa, including Coccinia, Ginkgo, Mercurialis, Populus, Rumex and Silene, as well as overarching topics, such as the field's terminology, analogies with animal sex determination systems, evolutionary pathways to dioecy, dosage compensation, and the longevity of the two sexes. In this introduction, we focus on four topics, each addressed by several articles from different angles and with different conclusions. Our highlighting of unclear or controversial issues may help future studies to build on the current understanding and to ask new questions that will expand our knowledge of plant sexual systems. This article is part of the theme issue 'Sex determination and sex chromosome evolution in land plants'.
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Affiliation(s)
- Susanne S. Renner
- Department of Biology, Washington University, Saint Louis, MO 63130, USA
| | - Niels A. Müller
- Thünen-Institute of Forest Genetics, Sieker Landstrasse 2, 22927 Grosshansdorf, Germany
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