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Crombie TA, McKeown R, Moya ND, Evans K, Widmayer S, LaGrassa V, Roman N, Tursunova O, Zhang G, Gibson S, Buchanan C, Roberto N, Vieira R, Tanny R, Andersen E. CaeNDR, the Caenorhabditis Natural Diversity Resource. Nucleic Acids Res 2024; 52:D850-D858. [PMID: 37855690 PMCID: PMC10767927 DOI: 10.1093/nar/gkad887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 09/30/2023] [Accepted: 10/06/2023] [Indexed: 10/20/2023] Open
Abstract
Studies of model organisms have provided important insights into how natural genetic differences shape trait variation. These discoveries are driven by the growing availability of genomes and the expansive experimental toolkits afforded to researchers using these species. For example, Caenorhabditis elegans is increasingly being used to identify and measure the effects of natural genetic variants on traits using quantitative genetics. Since 2016, the C. elegans Natural Diversity Resource (CeNDR) has facilitated many of these studies by providing an archive of wild strains, genome-wide sequence and variant data for each strain, and a genome-wide association (GWA) mapping portal for the C. elegans community. Here, we present an updated platform, the Caenorhabditis Natural Diversity Resource (CaeNDR), that enables quantitative genetics and genomics studies across the three Caenorhabditis species: C. elegans, C. briggsae and C. tropicalis. The CaeNDR platform hosts several databases that are continually updated by the addition of new strains, whole-genome sequence data and annotated variants. Additionally, CaeNDR provides new interactive tools to explore natural variation and enable GWA mappings. All CaeNDR data and tools are accessible through a freely available web portal located at caendr.org.
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Affiliation(s)
- Timothy A Crombie
- Department of Biomedical and Chemical Engineering and Sciences, Florida Institute of Technology, Melbourne, FL, USA
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Ryan McKeown
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
- Interdisciplinary Biological Sciences Program, Northwestern University, Evanston, IL, USA
| | - Nicolas D Moya
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
- Cell, Molecular, Developmental biology, and Biophysics Graduate Program, ohns Hopkins University, Baltimore, MD, USA
| | - Kathryn S Evans
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Samuel J Widmayer
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Vincent LaGrassa
- Northwestern University Information Technology, Media and Technology Innovation, Northwestern University, Evanston, IL USA
| | - Natalie Roman
- Northwestern University Information Technology, Media and Technology Innovation, Northwestern University, Evanston, IL USA
| | - Orzu Tursunova
- Northwestern University Information Technology, Media and Technology Innovation, Northwestern University, Evanston, IL USA
| | - Gaotian Zhang
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Sophia B Gibson
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Claire M Buchanan
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Nicole M Roberto
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Rodolfo Vieira
- Northwestern University Information Technology, Media and Technology Innovation, Northwestern University, Evanston, IL USA
| | - Robyn E Tanny
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| | - Erik C Andersen
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
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2
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Rödelsperger C. Comparative Genomics of Sex, Chromosomes, and Sex Chromosomes in Caenorhabditis elegans and Other Nematodes. Methods Mol Biol 2024; 2802:455-472. [PMID: 38819568 DOI: 10.1007/978-1-0716-3838-5_15] [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] [Indexed: 06/01/2024]
Abstract
The nematode phylum has evolved a remarkable diversity of reproductive modes, including the repeated emergence of asexuality and hermaphroditism across divergent clades. The species-richness and small genome size of nematodes make them ideal systems for investigating the genome-wide causes and consequences of such major transitions. The availability of functional annotations for most Caenorhabditis elegans genes further allows the linking of patterns of gene content evolution with biological processes. Such gene-centric studies were recently complemented by investigations of chromosome evolution that made use of the first chromosome-scale genome assemblies outside the Caenorhabditis genus. This review highlights recent comparative genomic studies of reproductive mode evolution addressing the hybrid origin of asexuality and the parallel gene loss following the emergence of hermaphroditism. It further summarizes ongoing efforts to characterize ancient linkage blocks called Nigon elements, which form central units of chromosome evolution. Fusions between Nigon elements have been demonstrated to impact recombination and speciation. Finally, multiple recent fusions between autosomal and the sex-linked Nigon element reveal insights into the dynamic evolution of sex chromosomes across various timescales.
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Affiliation(s)
- Christian Rödelsperger
- Department for Integrative Evolutionary Biology, Max Planck Institute for Biology, Tübingen, Germany.
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3
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Stevens L, Martínez-Ugalde I, King E, Wagah M, Absolon D, Bancroft R, Gonzalez de la Rosa P, Hall JL, Kieninger M, Kloch A, Pelan S, Robertson E, Pedersen AB, Abreu-Goodger C, Buck AH, Blaxter M. Ancient diversity in host-parasite interaction genes in a model parasitic nematode. Nat Commun 2023; 14:7776. [PMID: 38012132 PMCID: PMC10682056 DOI: 10.1038/s41467-023-43556-w] [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: 05/26/2023] [Accepted: 11/13/2023] [Indexed: 11/29/2023] Open
Abstract
Host-parasite interactions exert strong selection pressures on the genomes of both host and parasite. These interactions can lead to negative frequency-dependent selection, a form of balancing selection that is hypothesised to explain the high levels of polymorphism seen in many host immune and parasite antigen loci. Here, we sequence the genomes of several individuals of Heligmosomoides bakeri, a model parasite of house mice, and Heligmosomoides polygyrus, a closely related parasite of wood mice. Although H. bakeri is commonly referred to as H. polygyrus in the literature, their genomes show levels of divergence that are consistent with at least a million years of independent evolution. The genomes of both species contain hyper-divergent haplotypes that are enriched for proteins that interact with the host immune response. Many of these haplotypes originated prior to the divergence between H. bakeri and H. polygyrus, suggesting that they have been maintained by long-term balancing selection. Together, our results suggest that the selection pressures exerted by the host immune response have played a key role in shaping patterns of genetic diversity in the genomes of parasitic nematodes.
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Affiliation(s)
- Lewis Stevens
- Tree of Life, Wellcome Sanger Institute, Hinxton, UK.
| | - Isaac Martínez-Ugalde
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Erna King
- Tree of Life, Wellcome Sanger Institute, Hinxton, UK
| | - Martin Wagah
- Tree of Life, Wellcome Sanger Institute, Hinxton, UK
| | | | - Rowan Bancroft
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | | | - Jessica L Hall
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | | | | | - Sarah Pelan
- Tree of Life, Wellcome Sanger Institute, Hinxton, UK
| | - Elaine Robertson
- Institute of Immunology & Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Amy B Pedersen
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Cei Abreu-Goodger
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Amy H Buck
- Institute of Immunology & Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Mark Blaxter
- Tree of Life, Wellcome Sanger Institute, Hinxton, UK.
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4
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Palka JK, Dyba A, Brzozowska J, Antoł W, Sychta K, Prokop ZM. Evolution of fertilization ability in obligatorily outcrossing populations of Caenorhabditis elegans. PeerJ 2023; 11:e15825. [PMID: 37701823 PMCID: PMC10494835 DOI: 10.7717/peerj.15825] [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: 02/17/2023] [Accepted: 07/10/2023] [Indexed: 09/14/2023] Open
Abstract
In species reproducing by selfing, the traits connected with outcrossing typically undergo degeneration, a phenomenon called selfing syndrome. In Caenorhabditis elegans nematodes, selfing syndrome affects many traits involved in mating, rendering cross-fertilization highly inefficient. In this study, we investigated the evolution of cross-fertilization efficiency in populations genetically modified to reproduce by obligatory outcrossing. Following the genetic modification, replicate obligatorily outcrossing were maintained for over 100 generations, at either optimal (20 °C) or elevated (24 °C) temperatures, as a part of a broader experimental evolution program. Subsequently, fertilization rates were assayed in the evolving populations, as well as their ancestors who had the obligatory outcrossing introduced but did not go through experimental evolution. Fertilization effectivity was measured by tracking the fractions of fertilized females in age-synchronized populations, through 8 h since reaching adulthood. In order to check the robustness of our measurements, each evolving population was assayed in two or three independent replicate blocks. Indeed, we found high levels of among-block variability in the fertilization trajectories, and in the estimates of divergence between evolving populations and their ancestors. We also identified five populations which appear to have evolved increased fertilization efficiency, relative to their ancestors. However, due to the abovementioned high variability, this set of populations should be treated as candidate, with further replications needed to either confirm or disprove their divergence from ancestors. Furthermore, we also discuss additional observations we have made concerning fertilization trajectories.
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Affiliation(s)
- Joanna K. Palka
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University in Cracow, Cracow, Poland
| | - Alicja Dyba
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University in Cracow, Cracow, Poland
| | - Julia Brzozowska
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University in Cracow, Cracow, Poland
| | - Weronika Antoł
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University in Cracow, Cracow, Poland
| | - Karolina Sychta
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University in Cracow, Cracow, Poland
| | - Zofia M. Prokop
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University in Cracow, Cracow, Poland
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5
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Teterina AA, Willis JH, Lukac M, Jovelin R, Cutter AD, Phillips PC. Genomic diversity landscapes in outcrossing and selfing Caenorhabditis nematodes. PLoS Genet 2023; 19:e1010879. [PMID: 37585484 PMCID: PMC10461856 DOI: 10.1371/journal.pgen.1010879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 08/28/2023] [Accepted: 07/21/2023] [Indexed: 08/18/2023] Open
Abstract
Caenorhabditis nematodes form an excellent model for studying how the mode of reproduction affects genetic diversity, as some species reproduce via outcrossing whereas others can self-fertilize. Currently, chromosome-level patterns of diversity and recombination are only available for self-reproducing Caenorhabditis, making the generality of genomic patterns across the genus unclear given the profound potential influence of reproductive mode. Here we present a whole-genome diversity landscape, coupled with a new genetic map, for the outcrossing nematode C. remanei. We demonstrate that the genomic distribution of recombination in C. remanei, like the model nematode C. elegans, shows high recombination rates on chromosome arms and low rates toward the central regions. Patterns of genetic variation across the genome are also similar between these species, but differ dramatically in scale, being tenfold greater for C. remanei. Historical reconstructions of variation in effective population size over the past million generations echo this difference in polymorphism. Evolutionary simulations demonstrate how selection, recombination, mutation, and selfing shape variation along the genome, and that multiple drivers can produce patterns similar to those observed in natural populations. The results illustrate how genome organization and selection play a crucial role in shaping the genomic pattern of diversity whereas demographic processes scale the level of diversity across the genome as a whole.
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Affiliation(s)
- Anastasia A. Teterina
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon, United States of America
- Center of Parasitology, Severtsov Institute of Ecology and Evolution RAS, Moscow, Russia
| | - John H. Willis
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon, United States of America
| | - Matt Lukac
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon, United States of America
| | - Richard Jovelin
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
| | - Asher D. Cutter
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
| | - Patrick C. Phillips
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon, United States of America
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6
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Sun B, Kim H, Mello CC, Priess JR. The CERV protein of Cer1, a C. elegans LTR retrotransposon, is required for nuclear export of viral genomic RNA and can form giant nuclear rods. PLoS Genet 2023; 19:e1010804. [PMID: 37384599 DOI: 10.1371/journal.pgen.1010804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Accepted: 05/31/2023] [Indexed: 07/01/2023] Open
Abstract
Retroviruses and closely related LTR retrotransposons export full-length, unspliced genomic RNA (gRNA) for packaging into virions and to serve as the mRNA encoding GAG and POL polyproteins. Because gRNA often includes splice acceptor and donor sequences used to splice viral mRNAs, retroelements must overcome host mechanisms that retain intron-containing RNAs in the nucleus. Here we examine gRNA expression in Cer1, an LTR retrotransposon in C. elegans which somehow avoids silencing and is highly expressed in germ cells. Newly exported Cer1 gRNA associates rapidly with the Cer1 GAG protein, which has structural similarity with retroviral GAG proteins. gRNA export requires CERV (C. elegans regulator of viral expression), a novel protein encoded by a spliced Cer1 mRNA. CERV phosphorylation at S214 is essential for gRNA export, and phosphorylated CERV colocalizes with nuclear gRNA at presumptive sites of transcription. By electron microscopy, tagged CERV proteins surround clusters of distinct, linear fibrils that likely represent gRNA molecules. Single fibrils, or groups of aligned fibrils, also localize near nuclear pores. During the C. elegans self-fertile period, when hermaphrodites fertilize oocytes with their own sperm, CERV concentrates in two nuclear foci that are coincident with gRNA. However, as hermaphrodites cease self-fertilization, and can only produce cross-progeny, CERV undergoes a remarkable transition to form giant nuclear rods or cylinders that can be up to 5 microns in length. We propose a novel mechanism of rod formation, in which stage-specific changes in the nucleolus induce CERV to localize to the nucleolar periphery in flattened streaks of protein and gRNA; these streaks then roll up into cylinders. The rods are a widespread feature of Cer1 in wild strains of C. elegans, but their function is not known and might be limited to cross-progeny. We speculate that the adaptive strategy Cer1 uses for the identical self-progeny of a host hermaphrodite might differ for heterozygous cross-progeny sired by males. For example, mating introduces male chromosomes which can have different, or no, Cer1 elements.
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Affiliation(s)
- Bing Sun
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester,United States of America
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
| | - Haram Kim
- Fred Hutchinson Cancer Center, Seattle, Washington, United States of America
| | - Craig C Mello
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester,United States of America
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
| | - James R Priess
- Fred Hutchinson Cancer Center, Seattle, Washington, United States of America
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7
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Bu L, Lu L, Laidemitt MR, Zhang SM, Mutuku M, Mkoji G, Steinauer M, Loker ES. A genome sequence for Biomphalaria pfeifferi, the major vector snail for the human-infecting parasite Schistosoma mansoni. PLoS Negl Trop Dis 2023; 17:e0011208. [PMID: 36961841 PMCID: PMC10075465 DOI: 10.1371/journal.pntd.0011208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 04/05/2023] [Accepted: 02/27/2023] [Indexed: 03/25/2023] Open
Abstract
BACKGROUND Biomphalaria pfeifferi is the world's most widely distributed and commonly implicated vector snail species for the causative agent of human intestinal schistosomiasis, Schistosoma mansoni. In efforts to control S. mansoni transmission, chemotherapy alone has proven insufficient. New approaches to snail control offer a way forward, and possible genetic manipulations of snail vectors will require new tools. Towards this end, we here offer a diverse set of genomic resources for the important African schistosome vector, B. pfeifferi. METHODOLOGY/PRINCIPAL FINDINGS Based largely on PacBio High-Fidelity long reads, we report a genome assembly size of 772 Mb for B. pfeifferi (Kenya), smaller in size than known genomes of other planorbid schistosome vectors. In a total of 505 scaffolds (N50 = 3.2Mb), 430 were assigned to 18 large linkage groups inferred to represent the 18 known chromosomes, based on whole genome comparisons with Biomphalaria glabrata. The annotated B. pfeifferi genome reveals a divergence time of 3.01 million years with B. glabrata, a South American species believed to be similar to the progenitors of B. pfeifferi which undertook a trans-Atlantic colonization < five million years ago. CONCLUSIONS/SIGNIFICANCE The genome for this preferentially self-crossing species is less heterozygous than related species known to be preferential out-crossers; its smaller genome relative to congeners may similarly reflect its preference for selfing. Expansions of gene families with immune relevance are noted, including the FReD gene family which is far more similar in its composition to B. glabrata than to Bulinus truncatus, a vector for Schistosoma haematobium. Provision of this annotated genome will help better understand the dependencies of trematodes on snails, enable broader comparative insights regarding factors contributing to susceptibility/ resistance of snails to schistosome infections, and provide an invaluable resource with respect to identifying and manipulating snail genes as potential targets for more specific snail control programs.
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Affiliation(s)
- Lijing Bu
- Department of Biology, Center for Evolutionary and Theoretical Immunology, Parasite Division Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Lijun Lu
- Department of Biology, Center for Evolutionary and Theoretical Immunology, Parasite Division Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Martina R Laidemitt
- Department of Biology, Center for Evolutionary and Theoretical Immunology, Parasite Division Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Si-Ming Zhang
- Department of Biology, Center for Evolutionary and Theoretical Immunology, Parasite Division Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico, United States of America
| | - Martin Mutuku
- Center for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Gerald Mkoji
- Center for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Michelle Steinauer
- College of Osteopathic Medicine of the Pacific-Northwest, Western University of Health Sciences, Lebanon, Oregon, United States of America
| | - Eric S Loker
- Department of Biology, Center for Evolutionary and Theoretical Immunology, Parasite Division Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico, United States of America
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8
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Antoł W, Byszko J, Dyba A, Palka J, Babik W, Prokop Z. No detectable changes in reproductive behaviour of Caenorhabditis elegans males after 97 generations under obligatory outcrossing. PeerJ 2023; 11:e14572. [PMID: 36643640 PMCID: PMC9838211 DOI: 10.7717/peerj.14572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 11/28/2022] [Indexed: 01/12/2023] Open
Abstract
In Caenorhabditis elegans, a species reproducing mostly via self-fertilization, numerous signatures of selfing syndrome are observed, including differences in reproductive behaviour compared to related obligatory outcrossing species. In this study we investigated the effect of nearly 100 generations of obligatory outcrossing on several characteristics of male reproductive behaviour. A genetically uniform ancestral population carrying a mutation changing the reproductive system to obligatory outcrossing was split into four independent populations. We predicted that the transition from the natural reproductive system, where males were extremely rare, to obligatory outcrossing, where males comprise 50% of the population and are necessary for reproduction, will increase the selection pressure on higher effectiveness of mating behaviour. Several characteristics of male mating behaviour during a 15 min interaction as well as copulation success were compared between the ancestral and evolved populations. No significant differences in male mating behaviour or fertilization success were detected between generations 1 and 97 of obligatory outcrossing populations. We found, however, that longer contact with females increased chances of successful copulation, although this effect did not differ between populations. We conclude that either selection acting on male mating behaviour has not been strong enough, or mutational input of new adaptive variants has not been sufficient to cause noticeable behavioural differences after 97 generations of evolution starting from genetically uniform population.
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9
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Wiberg RAW, Viktorin G, Schärer L. Mating strategy predicts gene presence/absence patterns in a genus of simultaneously hermaphroditic flatworms. Evolution 2022; 76:3054-3066. [PMID: 36199200 PMCID: PMC10092323 DOI: 10.1111/evo.14635] [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: 05/16/2022] [Accepted: 09/28/2022] [Indexed: 01/22/2023]
Abstract
Gene repertoire turnover is a characteristic of genome evolution. However, we lack well-replicated analyses of presence/absence patterns associated with different selection contexts. Here, we study ∼100 transcriptome assemblies across Macrostomum, a genus of simultaneously hermaphroditic flatworms exhibiting multiple convergent shifts in mating strategy and associated reproductive morphologies. Many species mate reciprocally, with partners donating and receiving sperm at the same time. Other species convergently evolved to mate by hypodermic injection of sperm into the partner. We find that for orthologous transcripts annotated as expressed in the body region containing the testes, sequences from hypodermically inseminating species diverge more rapidly from the model species, Macrostomum lignano, and have a lower probability of being observed in other species. For other annotation categories, simpler models with a constant rate of similarity decay with increasing genetic distance from M. lignano match the observed patterns well. Thus, faster rates of sequence evolution for hypodermically inseminating species in testis-region genes result in higher rates of homology detection failure, yielding a signal of rapid evolution in sequence presence/absence patterns. Our results highlight the utility of considering appropriate null models for unobserved genes, as well as associating patterns of gene presence/absence with replicated evolutionary events in a phylogenetic context.
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Affiliation(s)
- R Axel W Wiberg
- Zoological Institute, Department of Environmental Sciences, University of Basel, Basel, CH-4051, Switzerland.,Evolutionary Biology, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Uppsala, SE-75236, Sweden
| | - Gudrun Viktorin
- Zoological Institute, Department of Environmental Sciences, University of Basel, Basel, CH-4051, Switzerland
| | - Lukas Schärer
- Zoological Institute, Department of Environmental Sciences, University of Basel, Basel, CH-4051, Switzerland
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10
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Sun S, Kanzaki N, Dayi M, Maeda Y, Yoshida A, Tanaka R, Kikuchi T. The compact genome of Caenorhabditis niphades n. sp., isolated from a wood-boring weevil, Niphades variegatus. BMC Genomics 2022; 23:765. [PMID: 36418933 PMCID: PMC9682657 DOI: 10.1186/s12864-022-09011-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2022] [Accepted: 11/14/2022] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND The first metazoan genome sequenced, that of Caenorhabditis elegans, has motivated animal genome evolution studies. To date > 50 species from the genus Caenorhabditis have been sequenced, allowing research on genome variation. RESULTS In the present study, we describe a new gonochoristic species, Caenorhabditis niphades n. sp., previously referred as C. sp. 36, isolated from adult weevils (Niphades variegatus), with whom they appear to be tightly associated during its life cycle. Along with a species description, we sequenced the genome of C. niphades n. sp. and produced a chromosome-level assembly. A genome comparison highlighted that C. niphades n. sp. has the smallest genome (59 Mbp) so far sequenced in the Elegans supergroup, despite being closely related to a species with an exceptionally large genome, C. japonica. CONCLUSIONS The compact genome of C. niphades n. sp. can serve as a key resource for comparative evolutionary studies of genome and gene number expansions in Caenorhabditis species.
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Affiliation(s)
- Simo Sun
- grid.26999.3d0000 0001 2151 536XDepartment of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba, 277-8562 Japan ,grid.410849.00000 0001 0657 3887Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Miyazaki, 889-1692 Japan
| | - Natsumi Kanzaki
- grid.417935.d0000 0000 9150 188XKansai Research Center, Forestry and Forest Products Research Institute, 68 Nagaikyutaroh, Momoyama, Fushimi, Kyoto, 612-0855 Japan
| | - Mehmet Dayi
- grid.26999.3d0000 0001 2151 536XDepartment of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba, 277-8562 Japan ,grid.412121.50000 0001 1710 3792Forestry Vocational School, Duzce University, 81620 Duzce, Türkiye
| | - Yasunobu Maeda
- grid.26999.3d0000 0001 2151 536XDepartment of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba, 277-8562 Japan ,grid.410849.00000 0001 0657 3887Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Miyazaki, 889-1692 Japan
| | - Akemi Yoshida
- grid.410849.00000 0001 0657 3887Genomics and Bioenvironmental Science, Frontier Science Research Center, University of Miyazaki, Miyazaki, 889-1692 Japan
| | - Ryusei Tanaka
- grid.410849.00000 0001 0657 3887Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Miyazaki, 889-1692 Japan
| | - Taisei Kikuchi
- grid.26999.3d0000 0001 2151 536XDepartment of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba, 277-8562 Japan ,grid.410849.00000 0001 0657 3887Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Miyazaki, 889-1692 Japan
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11
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Abstract
The nematode Caenorhabditis elegans has shed light on many aspects of eukaryotic biology, including genetics, development, cell biology, and genomics. A major factor in the success of C. elegans as a model organism has been the availability, since the late 1990s, of an essentially gap-free and well-annotated nuclear genome sequence, divided among 6 chromosomes. In this review, we discuss the structure, function, and biology of C. elegans chromosomes and then provide a general perspective on chromosome biology in other diverse nematode species. We highlight malleable chromosome features including centromeres, telomeres, and repetitive elements, as well as the remarkable process of programmed DNA elimination (historically described as chromatin diminution) that induces loss of portions of the genome in somatic cells of a handful of nematode species. An exciting future prospect is that nematode species may enable experimental approaches to study chromosome features and to test models of chromosome evolution. In the long term, fundamental insights regarding how speciation is integrated with chromosome biology may be revealed.
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Affiliation(s)
- Peter M Carlton
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | - Richard E Davis
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Denver, CO 80045, USA.,RNA Bioscience Initiative, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Shawn Ahmed
- Department of Genetics, University of North Carolina, Chapel Hill, NC 27599, USA.,Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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12
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Andersen EC, Rockman MV. Natural genetic variation as a tool for discovery in Caenorhabditis nematodes. Genetics 2022; 220:iyab156. [PMID: 35134197 PMCID: PMC8733454 DOI: 10.1093/genetics/iyab156] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Accepted: 09/11/2021] [Indexed: 11/12/2022] Open
Abstract
Over the last 20 years, studies of Caenorhabditis elegans natural diversity have demonstrated the power of quantitative genetic approaches to reveal the evolutionary, ecological, and genetic factors that shape traits. These studies complement the use of the laboratory-adapted strain N2 and enable additional discoveries not possible using only one genetic background. In this chapter, we describe how to perform quantitative genetic studies in Caenorhabditis, with an emphasis on C. elegans. These approaches use correlations between genotype and phenotype across populations of genetically diverse individuals to discover the genetic causes of phenotypic variation. We present methods that use linkage, near-isogenic lines, association, and bulk-segregant mapping, and we describe the advantages and disadvantages of each approach. The power of C. elegans quantitative genetic mapping is best shown in the ability to connect phenotypic differences to specific genes and variants. We will present methods to narrow genomic regions to candidate genes and then tests to identify the gene or variant involved in a quantitative trait. The same features that make C. elegans a preeminent experimental model animal contribute to its exceptional value as a tool to understand natural phenotypic variation.
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Affiliation(s)
- Erik C Andersen
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60201, USA
| | - Matthew V Rockman
- Department of Biology and Center for Genomics & Systems Biology, New York University, New York, NY 10003, USA
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13
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Van Goor J, Shakes DC, Haag ES. Fisher vs. the Worms: Extraordinary Sex Ratios in Nematodes and the Mechanisms that Produce Them. Cells 2021; 10:1793. [PMID: 34359962 PMCID: PMC8303164 DOI: 10.3390/cells10071793] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 07/08/2021] [Accepted: 07/13/2021] [Indexed: 01/20/2023] Open
Abstract
Parker, Baker, and Smith provided the first robust theory explaining why anisogamy evolves in parallel in multicellular organisms. Anisogamy sets the stage for the emergence of separate sexes, and for another phenomenon with which Parker is associated: sperm competition. In outcrossing taxa with separate sexes, Fisher proposed that the sex ratio will tend towards unity in large, randomly mating populations due to a fitness advantage that accrues in individuals of the rarer sex. This creates a vast excess of sperm over that required to fertilize all available eggs, and intense competition as a result. However, small, inbred populations can experience selection for skewed sex ratios. This is widely appreciated in haplodiploid organisms, in which females can control the sex ratio behaviorally. In this review, we discuss recent research in nematodes that has characterized the mechanisms underlying highly skewed sex ratios in fully diploid systems. These include self-fertile hermaphroditism and the adaptive elimination of sperm competition factors, facultative parthenogenesis, non-Mendelian meiotic oddities involving the sex chromosomes, and environmental sex determination. By connecting sex ratio evolution and sperm biology in surprising ways, these phenomena link two "seminal" contributions of G. A. Parker.
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Affiliation(s)
- Justin Van Goor
- Department of Biology, University of Maryland, College Park, MD 20742, USA;
| | - Diane C. Shakes
- Department of Biology, William and Mary, Williamsburg, VA 23187, USA;
| | - Eric S. Haag
- Department of Biology, University of Maryland, College Park, MD 20742, USA;
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14
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Sutton JM, Millwood JD, Case McCormack A, Fierst JL. Optimizing experimental design for genome sequencing and assembly with Oxford Nanopore Technologies. GIGABYTE 2021; 2021:gigabyte27. [PMID: 36824342 PMCID: PMC9650304 DOI: 10.46471/gigabyte.27] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 07/05/2021] [Indexed: 11/09/2022] Open
Abstract
High quality reference genome sequences are the core of modern genomics. Oxford Nanopore Technologies (ONT) produces inexpensive DNA sequences, but has high error rates, which make sequence assembly and analysis difficult as genome size and complexity increases. Robust experimental design is necessary for ONT genome sequencing and assembly, but few studies have addressed eukaryotic organisms. Here, we present novel results using simulated and empirical ONT and DNA libraries to identify best practices for sequencing and assembly for several model species. We find that the unique error structure of ONT libraries causes errors to accumulate and assembly statistics plateau as sequence depth increases. High-quality assembled eukaryotic sequences require high-molecular-weight DNA extractions that increase sequence read length, and computational protocols that reduce error through pre-assembly correction and read selection. Our quantitative results will be helpful for researchers seeking guidance for de novo assembly projects.
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Affiliation(s)
- John M. Sutton
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487-0344, USA
| | - Joshua D. Millwood
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487-0344, USA
| | - A. Case McCormack
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487-0344, USA
| | - Janna L. Fierst
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487-0344, USA, Corresponding author. E-mail:
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15
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Rödelsperger C, Ebbing A, Sharma DR, Okumura M, Sommer RJ, Korswagen HC. Spatial Transcriptomics of Nematodes Identifies Sperm Cells as a Source of Genomic Novelty and Rapid Evolution. Mol Biol Evol 2021; 38:229-243. [PMID: 32785688 PMCID: PMC8480184 DOI: 10.1093/molbev/msaa207] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Divergence of gene function and expression during development can give rise to phenotypic differences at the level of cells, tissues, organs, and ultimately whole organisms. To gain insights into the evolution of gene expression and novel genes at spatial resolution, we compared the spatially resolved transcriptomes of two distantly related nematodes, Caenorhabditis elegans and Pristionchus pacificus, that diverged 60–90 Ma. The spatial transcriptomes of adult worms show little evidence for strong conservation at the level of single genes. Instead, regional expression is largely driven by recent duplication and emergence of novel genes. Estimation of gene ages across anatomical structures revealed an enrichment of novel genes in sperm-related regions. This provides first evidence in nematodes for the “out of testis” hypothesis that has been previously postulated based on studies in Drosophila and mammals. “Out of testis” genes represent a mix of products of pervasive transcription as well as fast evolving members of ancient gene families. Strikingly, numerous novel genes have known functions during meiosis in Caenorhabditis elegans indicating that even universal processes such as meiosis may be targets of rapid evolution. Our study highlights the importance of novel genes in generating phenotypic diversity and explicitly characterizes gene origination in sperm-related regions. Furthermore, it proposes new functions for previously uncharacterized genes and establishes the spatial transcriptome of Pristionchus pacificus as a catalog for future studies on the evolution of gene expression and function.
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Affiliation(s)
- Christian Rödelsperger
- Department for Integrative Evolutionary Biology, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Annabel Ebbing
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Utrecht, The Netherlands
| | - Devansh Raj Sharma
- Department for Integrative Evolutionary Biology, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Misako Okumura
- Program of Biomedical Science, Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan
| | - Ralf J Sommer
- Department for Integrative Evolutionary Biology, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Hendrik C Korswagen
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht, Utrecht, The Netherlands.,Developmental Biology, Department of Biology, Institute of Biodynamics and Biocomplexity, Utrecht University, Utrecht, The Netherlands
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16
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O’Connor CH, Sikkink KL, Nelson TC, Fierst JL, Cresko WA, Phillips PC. Complex pleiotropic genetic architecture of evolved heat stress and oxidative stress resistance in the nematode Caenorhabditis remanei. G3 (BETHESDA, MD.) 2021; 11:jkab045. [PMID: 33605401 PMCID: PMC8049431 DOI: 10.1093/g3journal/jkab045] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 02/01/2021] [Indexed: 12/04/2022]
Abstract
The adaptation of complex organisms to changing environments has been a central question in evolutionary quantitative genetics since its inception. The structure of the genotype-phenotype maps is critical because pleiotropic effects can generate widespread correlated responses to selection and potentially restrict the extent of evolutionary change. In this study, we use experimental evolution to dissect the genetic architecture of natural variation for acute heat stress and oxidative stress response in the nematode Caenorhabiditis remanei. Previous work in the classic model nematode Caenorhabiditis elegans has found that abiotic stress response is controlled by a handful of genes of major effect and that mutations in any one of these genes can have widespread pleiotropic effects on multiple stress response traits. Here, we find that acute heat stress response and acute oxidative response in C. remanei are polygenic, complex traits, with hundreds of genomic regions responding to selection. In contrast to expectation from mutation studies, we find that evolved acute heat stress and acute oxidative stress response for the most part display independent genetic bases. This lack of correlation is reflected at the levels of phenotype, gene expression, and in the genomic response to selection. Thus, while these findings support the general view that rapid adaptation can be generated by changes at hundreds to thousands of sites in the genome, the architecture of segregating variation is likely to be determined by the pleiotropic structure of the underlying genetic networks.
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Affiliation(s)
- Christine H O’Connor
- Institute for Ecology and Evolution, University of Oregon, Eugene, OR 97403, USA
| | - Kristin L Sikkink
- Institute for Ecology and Evolution, University of Oregon, Eugene, OR 97403, USA
| | - Thomas C Nelson
- Institute for Ecology and Evolution, University of Oregon, Eugene, OR 97403, USA
| | - Janna L Fierst
- Department of Biological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA
| | - William A Cresko
- Institute for Ecology and Evolution, University of Oregon, Eugene, OR 97403, USA
| | - Patrick C Phillips
- Institute for Ecology and Evolution, University of Oregon, Eugene, OR 97403, USA
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17
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Sánchez-Ramírez S, Weiss JG, Thomas CG, Cutter AD. Widespread misregulation of inter-species hybrid transcriptomes due to sex-specific and sex-chromosome regulatory evolution. PLoS Genet 2021; 17:e1009409. [PMID: 33667233 PMCID: PMC7968742 DOI: 10.1371/journal.pgen.1009409] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 03/17/2021] [Accepted: 02/09/2021] [Indexed: 01/04/2023] Open
Abstract
When gene regulatory networks diverge between species, their dysfunctional expression in inter-species hybrid individuals can create genetic incompatibilities that generate the developmental defects responsible for intrinsic post-zygotic reproductive isolation. Both cis- and trans-acting regulatory divergence can be hastened by directional selection through adaptation, sexual selection, and inter-sexual conflict, in addition to cryptic evolution under stabilizing selection. Dysfunctional sex-biased gene expression, in particular, may provide an important source of sexually-dimorphic genetic incompatibilities. Here, we characterize and compare male and female/hermaphrodite transcriptome profiles for sibling nematode species Caenorhabditis briggsae and C. nigoni, along with allele-specific expression in their F1 hybrids, to deconvolve features of expression divergence and regulatory dysfunction. Despite evidence of widespread stabilizing selection on gene expression, misexpression of sex-biased genes pervades F1 hybrids of both sexes. This finding implicates greater fragility of male genetic networks to produce dysfunctional organismal phenotypes. Spermatogenesis genes are especially prone to high divergence in both expression and coding sequences, consistent with a "faster male" model for Haldane's rule and elevated sterility of hybrid males. Moreover, underdominant expression pervades male-biased genes compared to female-biased and sex-neutral genes and an excess of cis-trans compensatory regulatory divergence for X-linked genes underscores a "large-X effect" for hybrid male expression dysfunction. Extensive regulatory divergence in sex determination pathway genes likely contributes to demasculinization of XX hybrids. The evolution of genetic incompatibilities due to regulatory versus coding sequence divergence, however, are expected to arise in an uncorrelated fashion. This study identifies important differences between the sexes in how regulatory networks diverge to contribute to sex-biases in how genetic incompatibilities manifest during the speciation process.
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Affiliation(s)
- Santiago Sánchez-Ramírez
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
- * E-mail: (SSR); (ADC)
| | - Jörg G. Weiss
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
| | - Cristel G. Thomas
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
- Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
| | - Asher D. Cutter
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
- * E-mail: (SSR); (ADC)
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18
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Noble LM, Yuen J, Stevens L, Moya N, Persaud R, Moscatelli M, Jackson JL, Zhang G, Chitrakar R, Baugh LR, Braendle C, Andersen EC, Seidel HS, Rockman MV. Selfing is the safest sex for Caenorhabditis tropicalis. eLife 2021; 10:e62587. [PMID: 33427200 PMCID: PMC7853720 DOI: 10.7554/elife.62587] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 01/08/2021] [Indexed: 12/30/2022] Open
Abstract
Mating systems have profound effects on genetic diversity and compatibility. The convergent evolution of self-fertilization in three Caenorhabditis species provides a powerful lens to examine causes and consequences of mating system transitions. Among the selfers, Caenorhabditis tropicalis is the least genetically diverse and most afflicted by outbreeding depression. We generated a chromosomal-scale genome for C. tropicalis and surveyed global diversity. Population structure is very strong, and islands of extreme divergence punctuate a genomic background that is highly homogeneous around the globe. Outbreeding depression in the laboratory is caused largely by multiple Medea-like elements, genetically consistent with maternal toxin/zygotic antidote systems. Loci with Medea activity harbor novel and duplicated genes, and their activity is modified by mito-nuclear background. Segregating Medea elements dramatically reduce fitness, and simulations show that selfing limits their spread. Frequent selfing in C. tropicalis may therefore be a strategy to avoid Medea-mediated outbreeding depression.
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Affiliation(s)
- Luke M Noble
- Department of Biology and Center for Genomics & Systems Biology, New York UniversityNew YorkUnited States
- Institute de Biologie, École Normale Supérieure, CNRS, InsermParisFrance
| | - John Yuen
- Department of Biology and Center for Genomics & Systems Biology, New York UniversityNew YorkUnited States
| | - Lewis Stevens
- Department of Molecular Biosciences, Northwestern UniversityEvanstonUnited States
| | - Nicolas Moya
- Department of Molecular Biosciences, Northwestern UniversityEvanstonUnited States
| | - Riaad Persaud
- Department of Biology and Center for Genomics & Systems Biology, New York UniversityNew YorkUnited States
| | - Marc Moscatelli
- Department of Biology and Center for Genomics & Systems Biology, New York UniversityNew YorkUnited States
| | - Jacqueline L Jackson
- Department of Biology and Center for Genomics & Systems Biology, New York UniversityNew YorkUnited States
| | - Gaotian Zhang
- Department of Molecular Biosciences, Northwestern UniversityEvanstonUnited States
| | | | - L Ryan Baugh
- Department of Biology, Duke UniversityDurhamUnited States
| | - Christian Braendle
- Institut de Biologie Valrose, Université Côte d’Azur, CNRS, InsermNiceFrance
| | - Erik C Andersen
- Department of Molecular Biosciences, Northwestern UniversityEvanstonUnited States
| | - Hannah S Seidel
- Department of Biology, Eastern Michigan UniversityYpsilantiUnited States
| | - Matthew V Rockman
- Department of Biology and Center for Genomics & Systems Biology, New York UniversityNew YorkUnited States
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19
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Solares EA, Tao Y, Long AD, Gaut BS. HapSolo: an optimization approach for removing secondary haplotigs during diploid genome assembly and scaffolding. BMC Bioinformatics 2021; 22:9. [PMID: 33407090 PMCID: PMC7788845 DOI: 10.1186/s12859-020-03939-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 12/15/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Despite marked recent improvements in long-read sequencing technology, the assembly of diploid genomes remains a difficult task. A major obstacle is distinguishing between alternative contigs that represent highly heterozygous regions. If primary and secondary contigs are not properly identified, the primary assembly will overrepresent both the size and complexity of the genome, which complicates downstream analysis such as scaffolding. RESULTS Here we illustrate a new method, which we call HapSolo, that identifies secondary contigs and defines a primary assembly based on multiple pairwise contig alignment metrics. HapSolo evaluates candidate primary assemblies using BUSCO scores and then distinguishes among candidate assemblies using a cost function. The cost function can be defined by the user but by default considers the number of missing, duplicated and single BUSCO genes within the assembly. HapSolo performs hill climbing to minimize cost over thousands of candidate assemblies. We illustrate the performance of HapSolo on genome data from three species: the Chardonnay grape (Vitis vinifera), with a genome of 490 Mb, a mosquito (Anopheles funestus; 200 Mb) and the Thorny Skate (Amblyraja radiata; 2650 Mb). CONCLUSIONS HapSolo rapidly identified candidate assemblies that yield improvements in assembly metrics, including decreased genome size and improved N50 scores. Contig N50 scores improved by 35%, 9% and 9% for Chardonnay, mosquito and the thorny skate, respectively, relative to unreduced primary assemblies. The benefits of HapSolo were amplified by down-stream analyses, which we illustrated by scaffolding with Hi-C data. We found, for example, that prior to the application of HapSolo, only 52% of the Chardonnay genome was captured in the largest 19 scaffolds, corresponding to the number of chromosomes. After the application of HapSolo, this value increased to ~ 84%. The improvements for the mosquito's largest three scaffolds, representing the number of chromosomes, were from 61 to 86%, and the improvement was even more pronounced for thorny skate. We compared the scaffolding results to assemblies that were based on PurgeDups for identifying secondary contigs, with generally superior results for HapSolo.
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Affiliation(s)
- Edwin A Solares
- Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA, 92697-2525, USA
| | - Yuan Tao
- Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA, 92697-2525, USA
| | - Anthony D Long
- Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA, 92697-2525, USA
| | - Brandon S Gaut
- Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA, 92697-2525, USA.
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20
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Woodruff GC, Teterina AA. Degradation of the Repetitive Genomic Landscape in a Close Relative of Caenorhabditis elegans. Mol Biol Evol 2020; 37:2549-2567. [PMID: 32359146 PMCID: PMC7475029 DOI: 10.1093/molbev/msaa107] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The abundance, diversity, and genomic distribution of repetitive elements is highly variable among species. These patterns are thought to be driven in part by reproductive mode and the interaction of selection and recombination, and recombination rates typically vary by chromosomal position. In the nematode Caenorhabditis elegans, repetitive elements are enriched at chromosome arms and depleted on centers, and this mirrors the chromosomal distributions of other genomic features such as recombination rate. How conserved is this genomic landscape of repeats, and what evolutionary forces maintain it? To address this, we compared the genomic organization of repetitive elements across five Caenorhabditis species with chromosome-level assemblies. As previously reported, repeat content is enriched on chromosome arms in most Caenorhabditis species, and no obvious patterns of repeat content associated with reproductive mode were observed. However, the fig-associated C. inopinata has experienced repetitive element expansion and reveals no association of global repeat density with chromosome position. Patterns of repeat superfamily specific distributions reveal this global pattern is driven largely by a few repeat superfamilies that in C. inopinata have expanded in number and have weak associations with chromosome position. Additionally, 15% of predicted protein-coding genes in C. inopinata align to transposon-related proteins. When these are excluded, C. inopinata has no enrichment of genes in chromosome centers, in contrast to its close relatives who all have such clusters. Forward evolutionary simulations reveal that chromosomal heterogeneity in recombination rate alone can generate structured repetitive genomic landscapes when insertions are weakly deleterious, whereas chromosomal heterogeneity in the fitness effects of transposon insertion can promote such landscapes across a variety of evolutionary scenarios. Thus, patterns of gene density along chromosomes likely contribute to global repetitive landscapes in this group, although other historical or genomic factors are needed to explain the idiosyncrasy of genomic organization of various transposable element taxa within C. inopinata. Taken together, these results highlight the power of comparative genomics and evolutionary simulations in testing hypotheses regarding the causes of genome organization.
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Affiliation(s)
- Gavin C Woodruff
- Institute of Ecology and Evolution, University of Oregon, Eugene, OR
| | - Anastasia A Teterina
- Institute of Ecology and Evolution, University of Oregon, Eugene, OR
- Center of Parasitology, Severtsov Institute of Ecology and Evolution RAS, Moscow, Russia
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21
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Teterina AA, Willis JH, Phillips PC. Chromosome-Level Assembly of the Caenorhabditis remanei Genome Reveals Conserved Patterns of Nematode Genome Organization. Genetics 2020; 214:769-780. [PMID: 32111628 PMCID: PMC7153949 DOI: 10.1534/genetics.119.303018] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 02/24/2020] [Indexed: 12/23/2022] Open
Abstract
The nematode Caenorhabditis elegans is one of the key model systems in biology, including possessing the first fully assembled animal genome. Whereas C. elegans is a self-reproducing hermaphrodite with fairly limited within-population variation, its relative C. remanei is an outcrossing species with much more extensive genetic variation, making it an ideal parallel model system for evolutionary genetic investigations. Here, we greatly improve on previous assemblies by generating a chromosome-level assembly of the entire C. remanei genome (124.8 Mb of total size) using long-read sequencing and chromatin conformation capture data. Like other fully assembled genomes in the genus, we find that the C. remanei genome displays a high degree of synteny with C. elegans despite multiple within-chromosome rearrangements. Both genomes have high gene density in central regions of chromosomes relative to chromosome ends and the opposite pattern for the accumulation of repetitive elements. C. elegans and C. remanei also show similar patterns of interchromosome interactions, with the central regions of chromosomes appearing to interact with one another more than the distal ends. The new C. remanei genome presented here greatly augments the use of the Caenorhabditis as a platform for comparative genomics and serves as a basis for molecular population genetics within this highly diverse species.
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Affiliation(s)
- Anastasia A Teterina
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon 97403
- Center of Parasitology, A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow 117071, Russia
| | - John H Willis
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon 97403
| | - Patrick C Phillips
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon 97403
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22
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Garrigues JM, Tsu BV, Daugherty MD, Pasquinelli AE. Diversification of the Caenorhabditis heat shock response by Helitron transposable elements. eLife 2019; 8:51139. [PMID: 31825311 PMCID: PMC6927752 DOI: 10.7554/elife.51139] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 12/10/2019] [Indexed: 12/15/2022] Open
Abstract
Heat Shock Factor 1 (HSF-1) is a key regulator of the heat shock response (HSR). Upon heat shock, HSF-1 binds well-conserved motifs, called Heat Shock Elements (HSEs), and drives expression of genes important for cellular protection during this stress. Remarkably, we found that substantial numbers of HSEs in multiple Caenorhabditis species reside within Helitrons, a type of DNA transposon. Consistent with Helitron-embedded HSEs being functional, upon heat shock they display increased HSF-1 and RNA polymerase II occupancy and up-regulation of nearby genes in C. elegans. Interestingly, we found that different genes appear to be incorporated into the HSR by species-specific Helitron insertions in C. elegans and C. briggsae and by strain-specific insertions among different wild isolates of C. elegans. Our studies uncover previously unidentified targets of HSF-1 and show that Helitron insertions are responsible for rewiring and diversifying the Caenorhabditis HSR.
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Affiliation(s)
- Jacob M Garrigues
- Division of Biology, University of California, San Diego, San Diego, United States
| | - Brian V Tsu
- Division of Biology, University of California, San Diego, San Diego, United States
| | - Matthew D Daugherty
- Division of Biology, University of California, San Diego, San Diego, United States
| | - Amy E Pasquinelli
- Division of Biology, University of California, San Diego, San Diego, United States
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23
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Lamelza P, Young JM, Noble LM, Caro L, Isakharov A, Palanisamy M, Rockman MV, Malik HS, Ailion M. Hybridization promotes asexual reproduction in Caenorhabditis nematodes. PLoS Genet 2019; 15:e1008520. [PMID: 31841515 PMCID: PMC6946170 DOI: 10.1371/journal.pgen.1008520] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Revised: 01/07/2020] [Accepted: 11/15/2019] [Indexed: 02/04/2023] Open
Abstract
Although most unicellular organisms reproduce asexually, most multicellular eukaryotes are obligately sexual. This implies that there are strong barriers that prevent the origin or maintenance of asexuality arising from an obligately sexual ancestor. By studying rare asexual animal species we can gain a better understanding of the circumstances that facilitate their evolution from a sexual ancestor. Of the known asexual animal species, many originated by hybridization between two ancestral sexual species. The balance hypothesis predicts that genetic incompatibilities between the divergent genomes in hybrids can modify meiosis and facilitate asexual reproduction, but there are few instances where this has been shown. Here we report that hybridizing two sexual Caenorhabditis nematode species (C. nouraguensis females and C. becei males) alters the normal inheritance of the maternal and paternal genomes during the formation of hybrid zygotes. Most offspring of this interspecies cross die during embryogenesis, exhibiting inheritance of a diploid C. nouraguensis maternal genome and incomplete inheritance of C. becei paternal DNA. However, a small fraction of offspring develop into viable adults that can be either fertile or sterile. Fertile offspring are produced asexually by sperm-dependent parthenogenesis (also called gynogenesis or pseudogamy); these progeny inherit a diploid maternal genome but fail to inherit a paternal genome. Sterile offspring are hybrids that inherit both a diploid maternal genome and a haploid paternal genome. Whole-genome sequencing of individual viable worms shows that diploid maternal inheritance in both fertile and sterile offspring results from an altered meiosis in C. nouraguensis oocytes and the inheritance of two randomly selected homologous chromatids. We hypothesize that hybrid incompatibility between C. nouraguensis and C. becei modifies maternal and paternal genome inheritance and indirectly induces gynogenetic reproduction. This system can be used to dissect the molecular mechanisms by which hybrid incompatibilities can facilitate the emergence of asexual reproduction.
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Affiliation(s)
- Piero Lamelza
- Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, Washington, United States of America
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Janet M. Young
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Luke M. Noble
- Department of Biology and Center for Genomics & Systems Biology, New York University, New York, New York, United States of America
| | - Lews Caro
- Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, Washington, United States of America
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Arielle Isakharov
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Meenakshi Palanisamy
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Matthew V. Rockman
- Department of Biology and Center for Genomics & Systems Biology, New York University, New York, New York, United States of America
| | - Harmit S. Malik
- Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, Washington, United States of America
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Michael Ailion
- Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, Washington, United States of America
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
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24
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Cutter AD. Reproductive transitions in plants and animals: selfing syndrome, sexual selection and speciation. THE NEW PHYTOLOGIST 2019; 224:1080-1094. [PMID: 31336389 DOI: 10.1111/nph.16075] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 07/17/2019] [Indexed: 05/23/2023]
Abstract
The evolution of predominant self-fertilisation frequently coincides with the evolution of a collection of phenotypes that comprise the 'selfing syndrome', in both plants and animals. Genomic features also display a selfing syndrome. Selfing syndrome traits often involve changes to male and female reproductive characters that were subject to sexual selection and sexual conflict in the obligatorily outcrossing ancestor, including the gametic phase for both plants and animals. Rapid evolution of reproductive traits, due to both relaxed selection and directional selection under the new status of predominant selfing, lays the genetic groundwork for reproductive isolation. Consequently, shifts in sexual selection pressures coupled to transitions to selfing provide a powerful paradigm for investigating the speciation process. Plant and animal studies, however, emphasise distinct selective forces influencing reproductive-mode transitions: genetic transmission advantage to selfing or reproductive assurance outweighing the costs of inbreeding depression vs the costs of males and meiosis. Here, I synthesise links between sexual selection, evolution of selfing and speciation, with particular focus on identifying commonalities and differences between plant and animal systems and pointing to areas warranting further synergy.
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Affiliation(s)
- Asher D Cutter
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
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25
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Gimond C, Vielle A, Silva-Soares N, Zdraljevic S, McGrath PT, Andersen EC, Braendle C. Natural Variation and Genetic Determinants of Caenorhabditis elegans Sperm Size. Genetics 2019; 213:615-632. [PMID: 31395653 PMCID: PMC6781899 DOI: 10.1534/genetics.119.302462] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 08/04/2019] [Indexed: 01/28/2023] Open
Abstract
The diversity in sperm shape and size represents a powerful paradigm to understand how selection drives the evolutionary diversification of cell morphology. Experimental work on the sperm biology of the male-hermaphrodite nematode Caenorhabditis elegans has elucidated diverse factors important for sperm fertilization success, including the competitive superiority of larger sperm. Yet despite extensive research, the molecular mechanisms regulating C. elegans sperm size and the genetic basis underlying natural variation in sperm size remain unknown. To address these questions, we quantified male sperm size variation of a worldwide panel of 97 genetically distinct C. elegans strains, allowing us to uncover significant genetic variation in male sperm size. Aiming to characterize the molecular genetic basis of C. elegans male sperm size variation using a genome-wide association study, we did not detect any significant quantitative trait loci. We therefore focused on the genetic analysis of pronounced sperm size differences observed between recently diverged laboratory strains (N2 vs. LSJ1/2). Using mutants and quantitative complementation tests, we demonstrate that variation in the gene nurf-1 underlies the evolution of small sperm in the LSJ lineage. Given the previous discovery that this same nurf-1 variation was central for hermaphrodite laboratory adaptation, the evolution of reduced male sperm size in LSJ strains likely reflects a pleiotropic consequence. Together, our results provide a comprehensive quantification of natural variation in C. elegans sperm size and first insights into the genetic determinants of Caenorhabditis sperm size, pointing at an involvement of the NURF chromatin remodeling complex.
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Affiliation(s)
- Clotilde Gimond
- Université Côte d'Azur, CNRS, Inserm, IBV, Nice 06100, France
| | - Anne Vielle
- Université Côte d'Azur, CNRS, Inserm, IBV, Nice 06100, France
| | - Nuno Silva-Soares
- Université Côte d'Azur, CNRS, Inserm, IBV, Nice 06100, France
- Instituto Gulbenkian de Ciencia, 2780-156 Oeiras, Portugal
| | - Stefan Zdraljevic
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208
| | - Patrick T McGrath
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Erik C Andersen
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208
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26
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Baker EA, Woollard A. How Weird is The Worm? Evolution of the Developmental Gene Toolkit in Caenorhabditis elegans. J Dev Biol 2019; 7:E19. [PMID: 31569401 PMCID: PMC6956190 DOI: 10.3390/jdb7040019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 09/20/2019] [Accepted: 09/25/2019] [Indexed: 01/14/2023] Open
Abstract
Comparative developmental biology and comparative genomics are the cornerstones of evolutionary developmental biology. Decades of fruitful research using nematodes have produced detailed accounts of the developmental and genomic variation in the nematode phylum. Evolutionary developmental biologists are now utilising these data as a tool with which to interrogate the evolutionary basis for the similarities and differences observed in Nematoda. Nematodes have often seemed atypical compared to the rest of the animal kingdom-from their totally lineage-dependent mode of embryogenesis to their abandonment of key toolkit genes usually deployed by bilaterians for proper development-worms are notorious rule breakers of the bilaterian handbook. However, exploring the nature of these deviations is providing answers to some of the biggest questions about the evolution of animal development. For example, why is the evolvability of each embryonic stage not the same? Why can evolution sometimes tolerate the loss of genes involved in key developmental events? Lastly, why does natural selection act to radically diverge toolkit genes in number and sequence in certain taxa? In answering these questions, insight is not only being provided about the evolution of nematodes, but of all metazoans.
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Affiliation(s)
- Emily A Baker
- Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, UK.
| | - Alison Woollard
- Department of Biochemistry, University of Oxford, South Parks Rd, Oxford OX1 3QU, UK.
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27
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Xu W, Long L, Zhao Y, Stevens L, Felipe I, Munoz J, Ellis RE, McGrath PT. Evolution of Yin and Yang isoforms of a chromatin remodeling subunit precedes the creation of two genes. eLife 2019; 8:e48119. [PMID: 31498079 PMCID: PMC6752949 DOI: 10.7554/elife.48119] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 09/05/2019] [Indexed: 12/13/2022] Open
Abstract
Genes can encode multiple isoforms, broadening their functions and providing a molecular substrate to evolve phenotypic diversity. Evolution of isoform function is a potential route to adapt to new environments. Here we show that de novo, beneficial alleles in the nurf-1 gene became fixed in two laboratory lineages of C. elegans after isolation from the wild in 1951, before methods of cryopreservation were developed. nurf-1 encodes an ortholog of BPTF, a large (>300 kD) multidomain subunit of the NURF chromatin remodeling complex. Using CRISPR-Cas9 genome editing and transgenic rescue, we demonstrate that in C. elegans, nurf-1 has split into two, largely non-overlapping isoforms (NURF-1.D and NURF-1.B, which we call Yin and Yang, respectively) that share only two of 26 exons. Both isoforms are essential for normal gametogenesis but have opposite effects on male/female gamete differentiation. Reproduction in hermaphrodites, which involves production of both sperm and oocytes, requires a balance of these opposing Yin and Yang isoforms. Transgenic rescue and genetic position of the fixed mutations suggest that different isoforms are modified in each laboratory strain. In a related clade of Caenorhabditis nematodes, the shared exons have duplicated, resulting in the split of the Yin and Yang isoforms into separate genes, each containing approximately 200 amino acids of duplicated sequence that has undergone accelerated protein evolution following the duplication. Associated with this duplication event is the loss of two additional nurf-1 transcripts, including the long-form transcript and a newly identified, highly expressed transcript encoded by the duplicated exons. We propose these lost transcripts are non-functional side products necessary to transcribe the Yin and Yang transcripts in the same cells. Our work demonstrates how gene sharing, through the production of multiple isoforms, can precede the creation of new, independent genes.
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Affiliation(s)
- Wen Xu
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaUnited States
| | - Lijiang Long
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaUnited States
- Interdisciplinary Graduate Program in Quantitative BiosciencesGeorgia Institute of TechnologyAtlantaUnited States
| | - Yuehui Zhao
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaUnited States
| | - Lewis Stevens
- Institute of Evolutionary Biology, Ashworth Laboratories, School of Biological SciencesUniversity of EdinburghEdinburghUnited Kingdom
| | - Irene Felipe
- Epithelial Carcinogenesis GroupSpanish National Cancer Research Center-CNIOMadridSpain
| | - Javier Munoz
- Proteomics Unit-ProteoRed-ISCIIISpanish National Cancer Research Center-CNIOMadridSpain
| | - Ronald E Ellis
- Department of Molecular BiologyRowan University School of Osteopathic MedicineStratfordUnited States
| | - Patrick T McGrath
- School of Biological SciencesGeorgia Institute of TechnologyAtlantaUnited States
- Parker H. Petit Institute of Bioengineering and BioscienceGeorgia Institute of TechnologyAtlantaUnited States
- School of PhysicsGeorgia Institute of TechnologyAtlantaUnited States
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28
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Roessler K, Muyle A, Diez CM, Gaut GRJ, Bousios A, Stitzer MC, Seymour DK, Doebley JF, Liu Q, Gaut BS. The genome-wide dynamics of purging during selfing in maize. NATURE PLANTS 2019; 5:980-990. [PMID: 31477888 DOI: 10.1038/s41477-019-0508-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 07/26/2019] [Indexed: 05/07/2023]
Abstract
Self-fertilization (also known as selfing) is an important reproductive strategy in plants and a widely applied tool for plant genetics and plant breeding. Selfing can lead to inbreeding depression by uncovering recessive deleterious variants, unless these variants are purged by selection. Here we investigated the dynamics of purging in a set of eleven maize lines that were selfed for six generations. We show that heterozygous, putatively deleterious single nucleotide polymorphisms are preferentially lost from the genome during selfing. Deleterious single nucleotide polymorphisms were lost more rapidly in regions of high recombination, presumably because recombination increases the efficacy of selection by uncoupling linked variants. Overall, heterozygosity decreased more slowly than expected, by an estimated 35% to 40% per generation instead of the expected 50%, perhaps reflecting pervasive associative overdominance. Finally, three lines exhibited marked decreases in genome size due to the purging of transposable elements. Genome loss was more likely to occur for lineages that began with larger genomes with more transposable elements and chromosomal knobs. These three lines purged an average of 398 Mb from their genomes, an amount equivalent to three Arabidopsis thaliana genomes per lineage, in only a few generations.
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Affiliation(s)
- Kyria Roessler
- Department of Ecology and Evolutionary Biology, UC Irvine, Irvine, CA, USA
| | - Aline Muyle
- Department of Ecology and Evolutionary Biology, UC Irvine, Irvine, CA, USA
| | | | | | | | | | - Danelle K Seymour
- Department of Ecology and Evolutionary Biology, UC Irvine, Irvine, CA, USA
| | - John F Doebley
- Department of Genetics, University of Wisconsin, Madison, WI, USA
| | - Qingpo Liu
- The Key Laboratory for Quality Improvement of Agricultural Products of Zheijang Province, College of Agriculture and Food Sciences, Zhejiang A&F University, Lin'an, Hangzhou, China.
| | - Brandon S Gaut
- Department of Ecology and Evolutionary Biology, UC Irvine, Irvine, CA, USA.
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29
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Cutter AD, Morran LT, Phillips PC. Males, Outcrossing, and Sexual Selection in Caenorhabditis Nematodes. Genetics 2019; 213:27-57. [PMID: 31488593 PMCID: PMC6727802 DOI: 10.1534/genetics.119.300244] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 06/06/2019] [Indexed: 12/15/2022] Open
Abstract
Males of Caenorhabditis elegans provide a crucial practical tool in the laboratory, but, as the rarer and more finicky sex, have not enjoyed the same depth of research attention as hermaphrodites. Males, however, have attracted the attention of evolutionary biologists who are exploiting the C. elegans system to test longstanding hypotheses about sexual selection, sexual conflict, transitions in reproductive mode, and genome evolution, as well as to make new discoveries about Caenorhabditis organismal biology. Here, we review the evolutionary concepts and data informed by study of males of C. elegans and other Caenorhabditis We give special attention to the important role of sperm cells as a mediator of inter-male competition and male-female conflict that has led to drastic trait divergence across species, despite exceptional phenotypic conservation in many other morphological features. We discuss the evolutionary forces important in the origins of reproductive mode transitions from males being common (gonochorism: females and males) to rare (androdioecy: hermaphrodites and males) and the factors that modulate male frequency in extant androdioecious populations, including the potential influence of selective interference, host-pathogen coevolution, and mutation accumulation. Further, we summarize the consequences of males being common vs rare for adaptation and for trait divergence, trait degradation, and trait dimorphism between the sexes, as well as for molecular evolution of the genome, at both micro-evolutionary and macro-evolutionary timescales. We conclude that C. elegans male biology remains underexploited and that future studies leveraging its extensive experimental resources are poised to discover novel biology and to inform profound questions about animal function and evolution.
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Affiliation(s)
- Asher D Cutter
- Department of Ecology and Evolutionary Biology, University of Toronto, Ontario M5S3B2, Canada
| | - Levi T Morran
- Department of Biology, Emory University, Atlanta, Georgia 30322, and
| | - Patrick C Phillips
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon 97403
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30
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Frenk S, Lister-Shimauchi EH, Ahmed S. Telomeric small RNAs in the genus Caenorhabditis. RNA (NEW YORK, N.Y.) 2019; 25:1061-1077. [PMID: 31239299 PMCID: PMC6800518 DOI: 10.1261/rna.071324.119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 05/28/2019] [Indexed: 06/09/2023]
Abstract
Telomeric DNA is composed of simple tandem repeat sequences and has a G-rich strand that runs 5' to 3' toward the chromosome terminus. Small RNAs with homology to telomeres have been observed in several organisms and could originate from telomeres or from interstitial telomere sequences (ITSs), which are composites of degenerate and perfect telomere repeat sequences found on chromosome arms. We identified Caenorhabditis elegans small RNAs composed of the Caenorhabditis telomere sequence (TTAGGC)n with up to three mismatches, which might interact with telomeres. We rigorously defined ITSs for genomes of C. elegans and for two closely related nematodes, Caenorhabditis briggsae and Caenorhabditis remanei Most telomeric small RNAs with mismatches originated from ITSs, which were depleted from mRNAs but were enriched in introns whose genes often displayed hallmarks of genomic silencing. C. elegans small RNAs composed of perfect telomere repeats were very rare but their levels increased by several orders of magnitude in C. briggsae and C. remanei Major small RNA species in C. elegans begin with a 5' guanine nucleotide, which was strongly depleted from perfect telomeric small RNAs of all three Caenorhabditis species. Perfect G-rich or C-rich telomeric small RNAs commonly began with 5' UAGGCU and 5' UUAGGC or 5' CUAAGC, respectively. In contrast, telomeric small RNAs with mismatches had a mixture of all four 5' nucleotides. We suggest that perfect telomeric small RNAs have a mechanism of biogenesis that is distinct from known classes of small RNAs and that a dramatic change in their regulation occurred during recent Caenorhabditis evolution.
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Affiliation(s)
- Stephen Frenk
- Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
| | - Evan H Lister-Shimauchi
- Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
| | - Shawn Ahmed
- Department of Genetics, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
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31
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Specific Interactions Between Autosome and X Chromosomes Cause Hybrid Male Sterility in Caenorhabditis Species. Genetics 2019; 212:801-813. [PMID: 31064822 DOI: 10.1534/genetics.119.302202] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 05/03/2019] [Indexed: 11/18/2022] Open
Abstract
Hybrid male progeny from interspecies crosses are more prone to sterility or inviability than hybrid female progeny, and the male sterility and inviability often demonstrate parent-of-origin asymmetry. However, the underlying genetic mechanism of asymmetric sterility or inviability remains elusive. We previously established a genome-wide hybrid incompatibility (HI) landscape between Caenorhabditis briggsae and C. nigoni by phenotyping a large collection of C. nigoni strains each carrying a C. briggsae introgression. In this study, we systematically dissect the genetic mechanism of asymmetric sterility and inviability in both hybrid male and female progeny between the two species. Specifically, we performed reciprocal crosses between C . briggsae and different C. nigoni strains that each carry a GFP-labeled C. briggsae genomic fragment referred to as introgression, and scored the HI phenotypes in the F1 progeny. The aggregated introgressions cover 94.6% of the C. briggsae genome, including 100% of the X chromosome. Surprisingly, we observed that two C. briggsae X fragments that produce C. nigoni male sterility as an introgression rescued hybrid F1 sterility in males fathered by C. briggsae Subsequent backcrossing analyses indicated that a specific interaction between the X-linked interaction and one autosome introgression is required to rescue the hybrid male sterility. In addition, we identified another two C. briggsae genomic intervals on chromosomes II and IV that can rescue the inviability, but not the sterility, of hybrid F1 males fathered by C. nigoni, suggesting the involvement of differential epistatic interactions in the asymmetric hybrid male fertility and inviability. Importantly, backcrossing of the rescued sterile males with C. nigoni led to the isolation of a 1.1-Mb genomic interval that specifically interacts with an X-linked introgression, which is essential for hybrid male fertility. We further identified three C. briggsae genomic intervals on chromosome I, II, and III that produced inviability in all F1 progeny, dependent on or independent of the parent-of-origin. Taken together, we identified multiple independent interacting loci that are responsible for asymmetric hybrid male and female sterility, and inviability, which lays a foundation for their molecular characterization.
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32
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Chromosome-Wide Evolution and Sex Determination in the Three-Sexed Nematode Auanema rhodensis. G3-GENES GENOMES GENETICS 2019; 9:1211-1230. [PMID: 30770412 PMCID: PMC6469403 DOI: 10.1534/g3.119.0011] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Trioecy, a mating system in which males, females and hermaphrodites co-exist, is a useful system to investigate the origin and maintenance of alternative mating strategies. In the trioecious nematode Auanema rhodensis, males have one X chromosome (XO), whereas females and hermaphrodites have two (XX). The female vs. hermaphrodite sex determination mechanisms have remained elusive. In this study, RNA-seq analyses show a 20% difference between the L2 hermaphrodite and female gene expression profiles. RNAi experiments targeting the DM (doublesex/mab-3) domain transcription factor dmd-10/11 suggest that the hermaphrodite sexual fate requires the upregulation of this gene. The genetic linkage map (GLM) shows that there is chromosome-wide heterozygosity for the X chromosome in F2 hermaphrodite-derived lines originated from crosses between two parental inbred strains. These results confirm the lack of recombination of the X chromosome in hermaphrodites, as previously reported. We also describe conserved chromosome elements (Nigon elements), which have been mostly maintained throughout the evolution of Rhabditina nematodes. The seven-chromosome karyotype of A. rhodensis, instead of the typical six found in other rhabditine species, derives from fusion/rearrangements events involving three Nigon elements. The A. rhodensis X chromosome is the smallest and most polymorphic with the least proportion of conserved genes. This may reflect its atypical mode of father-to-son transmission and its lack of recombination in hermaphrodites and males. In conclusion, this study provides a framework for studying the evolution of chromosomes in rhabditine nematodes, as well as possible mechanisms for the sex determination in a three-sexed species.
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33
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Stevens L, Félix M, Beltran T, Braendle C, Caurcel C, Fausett S, Fitch D, Frézal L, Gosse C, Kaur T, Kiontke K, Newton MD, Noble LM, Richaud A, Rockman MV, Sudhaus W, Blaxter M. Comparative genomics of 10 new Caenorhabditis species. Evol Lett 2019; 3:217-236. [PMID: 31007946 PMCID: PMC6457397 DOI: 10.1002/evl3.110] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 02/08/2019] [Accepted: 02/25/2019] [Indexed: 01/29/2023] Open
Abstract
The nematode Caenorhabditis elegans has been central to the understanding of metazoan biology. However, C. elegans is but one species among millions and the significance of this important model organism will only be fully revealed if it is placed in a rich evolutionary context. Global sampling efforts have led to the discovery of over 50 putative species from the genus Caenorhabditis, many of which await formal species description. Here, we present species descriptions for 10 new Caenorhabditis species. We also present draft genome sequences for nine of these new species, along with a transcriptome assembly for one. We exploit these whole-genome data to reconstruct the Caenorhabditis phylogeny and use this phylogenetic tree to dissect the evolution of morphology in the genus. We reveal extensive variation in genome size and investigate the molecular processes that underlie this variation. We show unexpected complexity in the evolutionary history of key developmental pathway genes. These new species and the associated genomic resources will be essential in our attempts to understand the evolutionary origins of the C. elegans model.
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Affiliation(s)
- Lewis Stevens
- Institute of Evolutionary Biology, Ashworth Laboratories, School of Biological SciencesUniversity of EdinburghEdinburghEH9 3JTUnited Kingdom
| | - Marie‐Anne Félix
- Institut de Biologie de l'Ecole Normale Supérieure, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, École Normale SupérieureParis Sciences et Lettres75005ParisFrance
| | - Toni Beltran
- MRC London Institute of Medical SciencesLondonW12 0NNUnited Kingdom
| | - Christian Braendle
- Université Côte d'Azur, Centre National de la Recherche Scientifique, InsermInstitute of Biology Valrose06108NiceFrance
| | - Carlos Caurcel
- Institute of Evolutionary Biology, Ashworth Laboratories, School of Biological SciencesUniversity of EdinburghEdinburghEH9 3JTUnited Kingdom
| | - Sarah Fausett
- Université Côte d'Azur, Centre National de la Recherche Scientifique, InsermInstitute of Biology Valrose06108NiceFrance
| | - David Fitch
- Department of BiologyNew York UniversityNew YorkNew York10003
| | - Lise Frézal
- Institut de Biologie de l'Ecole Normale Supérieure, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, École Normale SupérieureParis Sciences et Lettres75005ParisFrance
| | - Charlie Gosse
- Institut de Biologie de l'Ecole Normale Supérieure, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, École Normale SupérieureParis Sciences et Lettres75005ParisFrance
| | - Taniya Kaur
- Center for Genomics and Systems Biology, Department of BiologyNew York UniversityNew YorkNew York10003
| | - Karin Kiontke
- Department of BiologyNew York UniversityNew YorkNew York10003
| | - Matthew D. Newton
- MRC London Institute of Medical SciencesLondonW12 0NNUnited Kingdom
- Molecular Virology, Department of MedicineImperial College LondonDu Cane RoadLondonW12 0NNUnited Kingdom
| | - Luke M. Noble
- Center for Genomics and Systems Biology, Department of BiologyNew York UniversityNew YorkNew York10003
| | - Aurélien Richaud
- Institut de Biologie de l'Ecole Normale Supérieure, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, École Normale SupérieureParis Sciences et Lettres75005ParisFrance
| | - Matthew V. Rockman
- Center for Genomics and Systems Biology, Department of BiologyNew York UniversityNew YorkNew York10003
| | - Walter Sudhaus
- Institut für Biologie/ZoologieFreie Universität BerlinBerlinD‐14195Germany
| | - Mark Blaxter
- Institute of Evolutionary Biology, Ashworth Laboratories, School of Biological SciencesUniversity of EdinburghEdinburghEH9 3JTUnited Kingdom
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34
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Sikkink KL, Reynolds RM, Ituarte CM, Cresko WA, Phillips PC. Environmental and Evolutionary Drivers of the Modular Gene Regulatory Network Underlying Phenotypic Plasticity for Stress Resistance in the Nematode Caenorhabditis remanei. G3 (BETHESDA, MD.) 2019; 9:969-982. [PMID: 30679247 PMCID: PMC6404610 DOI: 10.1534/g3.118.200017] [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] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 01/23/2019] [Indexed: 11/18/2022]
Abstract
Organisms can cope with stressful environments via a combination of phenotypic plasticity at the individual level and adaptation at the population level. Changes in gene expression can play an important role in both. Significant advances in our understanding of gene regulatory plasticity and evolution have come from comparative studies in the field and laboratory. Experimental evolution provides another powerful path by which to learn about how differential regulation of genes and pathways contributes to both acclimation and adaptation. Here we present results from one such study using the nematode Caenorhabditis remanei We selected one set of lines to withstand heat stress and another oxidative stress. We then compared transcriptional responses to acute heat stress of both and an unselected control to the ancestral population using a weighted gene coexpression network analysis, finding that the transcriptional response is primarily dominated by a plastic response that is shared in the ancestor and all evolved populations. In addition, we identified several modules that respond to artificial selection by (1) changing the baseline level of expression, (2) altering the magnitude of the plastic response, or (3) a combination of the two. Our findings therefore reveal that while patterns of transcriptional response can be perturbed with short bouts of intense selection, the overall ancestral structure of transcriptional plasticity is largely maintained over time.
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Affiliation(s)
- Kristin L Sikkink
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon 97403
| | - Rose M Reynolds
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon 97403
- Department of Biology, William Jewell College, Liberty, Missouri 64068
| | - Catherine M Ituarte
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon 97403
| | - William A Cresko
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon 97403
| | - Patrick C Phillips
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon 97403
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35
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Memar N, Schiemann S, Hennig C, Findeis D, Conradt B, Schnabel R. Twenty million years of evolution: The embryogenesis of four Caenorhabditis species are indistinguishable despite extensive genome divergence. Dev Biol 2019; 447:182-199. [DOI: 10.1016/j.ydbio.2018.12.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Revised: 12/18/2018] [Accepted: 12/20/2018] [Indexed: 12/19/2022]
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36
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Abstract
A major current molecular evolution challenge is to link comparative genomic patterns to species' biology and ecology. Breeding systems are pivotal because they affect many population genetic processes and thus genome evolution. We review theoretical predictions and empirical evidence about molecular evolutionary processes under three distinct breeding systems-outcrossing, selfing, and asexuality. Breeding systems may have a profound impact on genome evolution, including molecular evolutionary rates, base composition, genomic conflict, and possibly genome size. We present and discuss the similarities and differences between the effects of selfing and clonality. In reverse, comparative and population genomic data and approaches help revisiting old questions on the long-term evolution of breeding systems.
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Affiliation(s)
- Sylvain Glémin
- Institut des Sciences de l'Evolution, UMR5554, Université Montpellier II, Montpellier, France
| | - Clémentine M François
- Institut des Sciences de l'Evolution, UMR5554, Université Montpellier II, Montpellier, France
| | - Nicolas Galtier
- Institut des Sciences de l'Evolution, UMR5554, Université Montpellier II, Montpellier, France.
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37
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Haddad R, Meter B, Ross JA. The Genetic Architecture of Intra-Species Hybrid Mito-Nuclear Epistasis. Front Genet 2018; 9:481. [PMID: 30505316 PMCID: PMC6250786 DOI: 10.3389/fgene.2018.00481] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 09/28/2018] [Indexed: 01/03/2023] Open
Abstract
Genetic variants that are neutral within, but deleterious between, populations (Dobzhansky-Muller Incompatibilities) are thought to initiate hybrid dysfunction and then to accumulate and complete the speciation process. To identify the types of genetic differences that might initiate speciation, it is useful to study inter-population (intra-species) hybrids that exhibit reduced fitness. In Caenorhabditis briggsae, a close relative of the nematode C. elegans, such minor genetic incompatibilities have been identified. One incompatibility between the mitochondrial and nuclear genomes reduces the fitness of some hybrids. To understand the nuclear genetic architecture of this epistatic interaction, we constructed two sets of recombinant inbred lines by hybridizing two genetically diverse wild populations. In such lines, selection is able to eliminate deleterious combinations of alleles derived from the two parental populations. The genotypes of surviving hybrid lines thus reveal favorable allele combinations at loci experiencing selection. Our genotype data from the resulting lines are consistent with the interpretation that the X alleles participate in epistatic interactions with autosomes and the mitochondrial genome. We evaluate this possibility given predictions that mitochondria-X epistasis should be more prevalent than between mitochondria and autosomes. Our empirical identification of inter-genomic linkage disequilibrium supports the body of literature indicating that the accumulation of mito-nuclear genetic incompatibilities might initiate the speciation process through the generation of less-fit inter-population hybrids.
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Affiliation(s)
- Rania Haddad
- Department of Biology, California State University, Fresno, Fresno, CA, United States
| | - Brandon Meter
- Department of Biology, California State University, Fresno, Fresno, CA, United States
| | - Joseph A Ross
- Department of Biology, California State University, Fresno, Fresno, CA, United States
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38
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Haag ES, Fitch DHA, Delattre M. From "the Worm" to "the Worms" and Back Again: The Evolutionary Developmental Biology of Nematodes. Genetics 2018; 210:397-433. [PMID: 30287515 PMCID: PMC6216592 DOI: 10.1534/genetics.118.300243] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 08/03/2018] [Indexed: 12/13/2022] Open
Abstract
Since the earliest days of research on nematodes, scientists have noted the developmental and morphological variation that exists within and between species. As various cellular and developmental processes were revealed through intense focus on Caenorhabditis elegans, these comparative studies have expanded. Within the genus Caenorhabditis, they include characterization of intraspecific polymorphisms and comparisons of distinct species, all generally amenable to the same laboratory culture methods and supported by robust genomic and experimental tools. The C. elegans paradigm has also motivated studies with more distantly related nematodes and animals. Combined with improved phylogenies, this work has led to important insights about the evolution of nematode development. First, while many aspects of C. elegans development are representative of Caenorhabditis, and of terrestrial nematodes more generally, others vary in ways both obvious and cryptic. Second, the system has revealed several clear examples of developmental flexibility in achieving a particular trait. This includes developmental system drift, in which the developmental control of homologous traits has diverged in different lineages, and cases of convergent evolution. Overall, the wealth of information and experimental techniques developed in C. elegans is being leveraged to make nematodes a powerful system for evolutionary cellular and developmental biology.
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Affiliation(s)
- Eric S Haag
- Department of Biology, University of Maryland, College Park, Maryland 20742
| | | | - Marie Delattre
- Laboratoire de Biologie Moléculaire de la Cellule, CNRS, INSERM, Ecole Normale Supérieure de Lyon, 69007, France
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39
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Rödelsperger C, Röseler W, Prabh N, Yoshida K, Weiler C, Herrmann M, Sommer RJ. Phylotranscriptomics of Pristionchus Nematodes Reveals Parallel Gene Loss in Six Hermaphroditic Lineages. Curr Biol 2018; 28:3123-3127.e5. [DOI: 10.1016/j.cub.2018.07.041] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 06/12/2018] [Accepted: 07/12/2018] [Indexed: 11/28/2022]
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40
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Prabh N, Roeseler W, Witte H, Eberhardt G, Sommer RJ, Rödelsperger C. Deep taxon sampling reveals the evolutionary dynamics of novel gene families in Pristionchus nematodes. Genome Res 2018; 28:1664-1674. [PMID: 30232197 PMCID: PMC6211646 DOI: 10.1101/gr.234971.118] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 09/05/2018] [Indexed: 01/20/2023]
Abstract
The widespread identification of genes without detectable homology in related taxa is a hallmark of genome sequencing projects in animals, together with the abundance of gene duplications. Such genes have been called novel, young, taxon-restricted, or orphans, but little is known about the mechanisms accounting for their origin, age, and mode of evolution. Phylogenomic studies relying on deep and systematic taxon sampling and using the comparative method can provide insight into the evolutionary dynamics acting on novel genes. We used a phylogenomic approach for the nematode model organism Pristionchus pacificus and sequenced six additional Pristionchus and two outgroup species. This resulted in 10 genomes with a ladder-like phylogeny, sequenced in one laboratory using the same platform and analyzed by the same bioinformatic procedures. Our analysis revealed that 68%-81% of genes are assignable to orthologous gene families, the majority of which defined nine age classes with presence/absence patterns that can be explained by single evolutionary events. Contrasting different age classes, we find that older age classes are concentrated at chromosome centers, whereas novel gene families preferentially arise at the periphery, are weakly expressed, evolve rapidly, and have a high propensity of being lost. Over time, they increase in expression and become more constrained. Thus, the detailed phylogenetic resolution allowed a comprehensive characterization of the evolutionary dynamics of Pristionchus genomes indicating that distribution of age classes and their associated differences shape chromosomal divergence. This study establishes the Pristionchus system for future research on the mechanisms that drive the formation of novel genes.
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Affiliation(s)
- Neel Prabh
- Department of Integrative Evolutionary Biology, Max-Planck-Institute for Developmental Biology, Max-Planck-Ring 9, 72076 Tübingen, Germany
| | - Waltraud Roeseler
- Department of Integrative Evolutionary Biology, Max-Planck-Institute for Developmental Biology, Max-Planck-Ring 9, 72076 Tübingen, Germany
| | - Hanh Witte
- Department of Integrative Evolutionary Biology, Max-Planck-Institute for Developmental Biology, Max-Planck-Ring 9, 72076 Tübingen, Germany
| | - Gabi Eberhardt
- Department of Integrative Evolutionary Biology, Max-Planck-Institute for Developmental Biology, Max-Planck-Ring 9, 72076 Tübingen, Germany
| | - Ralf J Sommer
- Department of Integrative Evolutionary Biology, Max-Planck-Institute for Developmental Biology, Max-Planck-Ring 9, 72076 Tübingen, Germany
| | - Christian Rödelsperger
- Department of Integrative Evolutionary Biology, Max-Planck-Institute for Developmental Biology, Max-Planck-Ring 9, 72076 Tübingen, Germany
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41
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Kanzaki N, Tsai IJ, Tanaka R, Hunt VL, Liu D, Tsuyama K, Maeda Y, Namai S, Kumagai R, Tracey A, Holroyd N, Doyle SR, Woodruff GC, Murase K, Kitazume H, Chai C, Akagi A, Panda O, Ke HM, Schroeder FC, Wang J, Berriman M, Sternberg PW, Sugimoto A, Kikuchi T. Biology and genome of a newly discovered sibling species of Caenorhabditis elegans. Nat Commun 2018; 9:3216. [PMID: 30097582 PMCID: PMC6086898 DOI: 10.1038/s41467-018-05712-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 07/19/2018] [Indexed: 01/19/2023] Open
Abstract
A 'sibling' species of the model organism Caenorhabditis elegans has long been sought for use in comparative analyses that would enable deep evolutionary interpretations of biological phenomena. Here, we describe the first sibling species of C. elegans, C. inopinata n. sp., isolated from fig syconia in Okinawa, Japan. We investigate the morphology, developmental processes and behaviour of C. inopinata, which differ significantly from those of C. elegans. The 123-Mb C. inopinata genome was sequenced and assembled into six nuclear chromosomes, allowing delineation of Caenorhabditis genome evolution and revealing unique characteristics, such as highly expanded transposable elements that might have contributed to the genome evolution of C. inopinata. In addition, C. inopinata exhibits massive gene losses in chemoreceptor gene families, which could be correlated with its limited habitat area. We have developed genetic and molecular techniques for C. inopinata; thus C. inopinata provides an exciting new platform for comparative evolutionary studies.
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Affiliation(s)
- Natsumi Kanzaki
- Forestry and Forest Products Research Institute, Tsukuba, 305-8687, Japan
- Kansai Research Center, Forestry and Forest Products Research Institute, 68 Nagaikyutaroh, Momoyama, Fushimi, Kyoto, 612-0855, Japan
| | - Isheng J Tsai
- Biodiversity Research Center, Academia Sinica, Taipei city, 11529, Taiwan
| | - Ryusei Tanaka
- Faculty of Medicine, University of Miyazaki, Miyazaki, 889-1692, Japan
| | - Vicky L Hunt
- Faculty of Medicine, University of Miyazaki, Miyazaki, 889-1692, Japan
| | - Dang Liu
- Biodiversity Research Center, Academia Sinica, Taipei city, 11529, Taiwan
| | - Kenji Tsuyama
- Laboratory of Developmental Dynamics, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan
| | - Yasunobu Maeda
- Faculty of Medicine, University of Miyazaki, Miyazaki, 889-1692, Japan
| | - Satoshi Namai
- Laboratory of Developmental Dynamics, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan
| | - Ryohei Kumagai
- Laboratory of Developmental Dynamics, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan
| | - Alan Tracey
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, CB10 1SA, UK
| | - Nancy Holroyd
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, CB10 1SA, UK
| | - Stephen R Doyle
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, CB10 1SA, UK
| | - Gavin C Woodruff
- Forestry and Forest Products Research Institute, Tsukuba, 305-8687, Japan
- Department of Biology, Institute of Ecology and Evolution, University of Oregon, Eugene, OR, 97403-5289, USA
| | - Kazunori Murase
- Faculty of Medicine, University of Miyazaki, Miyazaki, 889-1692, Japan
| | - Hiromi Kitazume
- Faculty of Medicine, University of Miyazaki, Miyazaki, 889-1692, Japan
| | - Cynthia Chai
- HHMI and Division of Biology and Biological Engineering, Caltech, Pasadena, CA, 91125, USA
| | - Allison Akagi
- HHMI and Division of Biology and Biological Engineering, Caltech, Pasadena, CA, 91125, USA
| | - Oishika Panda
- Boyce Thompson Institute, and Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Huei-Mien Ke
- Biodiversity Research Center, Academia Sinica, Taipei city, 11529, Taiwan
| | - Frank C Schroeder
- Boyce Thompson Institute, and Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA
| | - John Wang
- Biodiversity Research Center, Academia Sinica, Taipei city, 11529, Taiwan
| | - Matthew Berriman
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, CB10 1SA, UK
| | - Paul W Sternberg
- HHMI and Division of Biology and Biological Engineering, Caltech, Pasadena, CA, 91125, USA
| | - Asako Sugimoto
- Laboratory of Developmental Dynamics, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan.
| | - Taisei Kikuchi
- Faculty of Medicine, University of Miyazaki, Miyazaki, 889-1692, Japan.
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42
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Bundus JD, Wang D, Cutter AD. Genetic basis to hybrid inviability is more complex than hybrid male sterility in Caenorhabditis nematodes. Heredity (Edinb) 2018; 121:169-182. [PMID: 29626207 PMCID: PMC6039526 DOI: 10.1038/s41437-018-0069-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 01/22/2018] [Accepted: 02/11/2018] [Indexed: 12/31/2022] Open
Abstract
Hybrid male sterility often evolves before female sterility or inviability of hybrids, implying that the accumulation of divergence between separated lineages should lead hybrid male sterility to have a more polygenic basis. However, experimental evidence is mixed. Here, we use the nematodes Caenorhabditis remanei and C. latens to characterize the underlying genetic basis of asymmetric hybrid male sterility and hybrid inviability. We demonstrate that hybrid male sterility is consistent with a simple genetic basis, involving a single X-autosome incompatibility. We also show that hybrid inviability involves more genomic compartments, involving diverse nuclear-nuclear incompatibilities, a mito-nuclear incompatibility, and maternal effects. These findings demonstrate that male sensitivity to genetic perturbation may be genetically simple compared to hybrid inviability in Caenorhabditis and motivates tests of generality for the genetic architecture of hybrid incompatibility across the breadth of phylogeny.
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Affiliation(s)
- Joanna D Bundus
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
| | - Donglin Wang
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
| | - Asher D Cutter
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada.
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43
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Rödelsperger C, Meyer JM, Prabh N, Lanz C, Bemm F, Sommer RJ. Single-Molecule Sequencing Reveals the Chromosome-Scale Genomic Architecture of the Nematode Model Organism Pristionchus pacificus. Cell Rep 2018; 21:834-844. [PMID: 29045848 DOI: 10.1016/j.celrep.2017.09.077] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 08/01/2017] [Accepted: 09/24/2017] [Indexed: 01/24/2023] Open
Abstract
The nematode Pristionchus pacificus is an established model for integrative evolutionary biology and comparative studies with Caenorhabditis elegans. While an existing genome draft facilitated the identification of several genes controlling various developmental processes, its high degree of fragmentation complicated virtually all genomic analyses. Here, we present a de novo genome assembly from single-molecule, long-read sequencing data consisting of 135 P. pacificus contigs. When combined with a genetic linkage map, 99% of the assembly could be ordered and oriented into six chromosomes. This allowed us to robustly characterize chromosomal patterns of gene density, repeat content, nucleotide diversity, linkage disequilibrium, and macrosynteny in P. pacificus. Despite widespread conservation of synteny between P. pacificus and C. elegans, we identified one major translocation from an autosome to the sex chromosome in the lineage leading to C. elegans. This highlights the potential of the chromosome-scale assembly for future genomic studies of P. pacificus.
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Affiliation(s)
- Christian Rödelsperger
- Department of Evolutionary Biology, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany.
| | - Jan M Meyer
- Department of Evolutionary Biology, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Neel Prabh
- Department of Evolutionary Biology, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Christa Lanz
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Felix Bemm
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Ralf J Sommer
- Department of Evolutionary Biology, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany.
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44
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Curran DM, Gilleard JS, Wasmuth JD. MIPhy: identify and quantify rapidly evolving members of large gene families. PeerJ 2018; 6:e4873. [PMID: 29868279 PMCID: PMC5983006 DOI: 10.7717/peerj.4873] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 05/10/2018] [Indexed: 11/20/2022] Open
Abstract
After transitioning to a new environment, species often exhibit rapid phenotypic innovation. One of the fastest mechanisms for this is duplication followed by specialization of existing genes. When this happens to a member of a gene family, it tends to leave a detectable phylogenetic signature of lineage-specific expansions and contractions. These can be identified by analyzing the gene family across several species and identifying patterns of gene duplication and loss that do not correlate with the known relationships between those species. This signature, termed phylogenetic instability, has been previously linked to adaptations that change the way an organism samples and responds to its environment; conversely, low phylogenetic instability has been previously linked to proteins with endogenous functions. With the increase in genome-level data, there is a need to identify and quantify phylogenetic instability. Here, we present Minimizing Instability in Phylogenetics (MIPhy), a tool that solves this problem by quantifying the incongruence of a gene's evolutionary history. The motivation behind MIPhy was to produce a tool to aid in interpreting phylogenetic trees. It can predict which members of a gene family are under adaptive evolution, working only from a gene tree and the relationship between the species under consideration. While it does not conduct any estimation of positive selection-which is the typical indication of adaptive evolution-the results tend to agree. We demonstrate the usefulness of MIPhy by accurately predicting which members of the mammalian cytochrome P450 gene superfamily metabolize xenobiotics and which metabolize endogenous compounds. Our predictions correlate very well with known substrate specificities of the human enzymes. We also analyze the Caenorhabditis collagen gene family and use MIPhy to predict genes that produce an observable phenotype when knocked down in C. elegans, and show that our predictions correlate well with existing knowledge. The software can be downloaded and installed from https://github.com/dave-the-scientist/miphy and is also available as an online web tool at http://www.miphy.wasmuthlab.org.
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Affiliation(s)
- David M. Curran
- Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
| | - John S. Gilleard
- Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
| | - James D. Wasmuth
- Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada
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45
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Bilinski P, Albert PS, Berg JJ, Birchler JA, Grote MN, Lorant A, Quezada J, Swarts K, Yang J, Ross-Ibarra J. Parallel altitudinal clines reveal trends in adaptive evolution of genome size in Zea mays. PLoS Genet 2018; 14:e1007162. [PMID: 29746459 PMCID: PMC5944917 DOI: 10.1371/journal.pgen.1007162] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 12/20/2017] [Indexed: 12/03/2022] Open
Abstract
While the vast majority of genome size variation in plants is due to differences in repetitive sequence, we know little about how selection acts on repeat content in natural populations. Here we investigate parallel changes in intraspecific genome size and repeat content of domesticated maize (Zea mays) landraces and their wild relative teosinte across altitudinal gradients in Mesoamerica and South America. We combine genotyping, low coverage whole-genome sequence data, and flow cytometry to test for evidence of selection on genome size and individual repeat abundance. We find that population structure alone cannot explain the observed variation, implying that clinal patterns of genome size are maintained by natural selection. Our modeling additionally provides evidence of selection on individual heterochromatic knob repeats, likely due to their large individual contribution to genome size. To better understand the phenotypes driving selection on genome size, we conducted a growth chamber experiment using a population of highland teosinte exhibiting extensive variation in genome size. We find weak support for a positive correlation between genome size and cell size, but stronger support for a negative correlation between genome size and the rate of cell production. Reanalyzing published data of cell counts in maize shoot apical meristems, we then identify a negative correlation between cell production rate and flowering time. Together, our data suggest a model in which variation in genome size is driven by natural selection on flowering time across altitudinal clines, connecting intraspecific variation in repetitive sequence to important differences in adaptive phenotypes. Genome size in plants can vary by orders of magnitude, but this variation has long been considered to be of little functional consequence. Studying three independent adaptations to high altitude in Zea mays, we find that genome size experiences parallel pressures from natural selection, causing a reduction in genome size with increasing altitude. Though reductions in overall repetitive content are responsible for the genome size change, we find that only those individual loci contributing most to the variation in genome size are individually targeted by selection. To identify the phenotype influenced by genome size, we study how variation in genome size within a single wild population impacts leaf growth and cell division. We find that genome size variation correlates negatively with the rate of cell division, suggesting that individuals with larger genomes require longer to complete a mitotic cycle. Finally, we reanalyze data from maize inbreds to show that faster cell division is correlated with earlier flowering, connecting observed variation in genome size to an important adaptive phenotype.
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Affiliation(s)
- Paul Bilinski
- Department of Plant Sciences, University of California, Davis, Davis, California, United States of America
- Research Group for Ancient Genomics and Evolution, Department of Molecular Biology, Max Planck Institute for Developmental Biology, Tuebingen, Germany
- * E-mail: (PB); (JRI)
| | - Patrice S. Albert
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, United States of America
| | - Jeremy J. Berg
- Center for Population Biology, University of California, Davis, Davis, California, United States of America
- Department of Evolution and Ecology, University of California, Davis, Davis, California, United States of America
| | - James A. Birchler
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, United States of America
| | - Mark N. Grote
- Department of Anthropology, University of California, Davis, Davis, California, United States of America
| | - Anne Lorant
- Department of Plant Sciences, University of California, Davis, Davis, California, United States of America
| | - Juvenal Quezada
- Department of Plant Sciences, University of California, Davis, Davis, California, United States of America
| | - Kelly Swarts
- Research Group for Ancient Genomics and Evolution, Department of Molecular Biology, Max Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Jinliang Yang
- Department of Plant Sciences, University of California, Davis, Davis, California, United States of America
- Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Jeffrey Ross-Ibarra
- Department of Plant Sciences, University of California, Davis, Davis, California, United States of America
- Center for Population Biology, University of California, Davis, Davis, California, United States of America
- Genome Center, University of California, Davis, Davis, California, United States of America
- * E-mail: (PB); (JRI)
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46
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Bilinski P, Albert PS, Berg JJ, Birchler JA, Grote MN, Lorant A, Quezada J, Swarts K, Yang J, Ross-Ibarra J. Parallel altitudinal clines reveal trends in adaptive evolution of genome size in Zea mays. PLoS Genet 2018; 14:e1007162. [PMID: 29746459 DOI: 10.1371/journal.pgen.1007162.g001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 12/20/2017] [Indexed: 05/23/2023] Open
Abstract
While the vast majority of genome size variation in plants is due to differences in repetitive sequence, we know little about how selection acts on repeat content in natural populations. Here we investigate parallel changes in intraspecific genome size and repeat content of domesticated maize (Zea mays) landraces and their wild relative teosinte across altitudinal gradients in Mesoamerica and South America. We combine genotyping, low coverage whole-genome sequence data, and flow cytometry to test for evidence of selection on genome size and individual repeat abundance. We find that population structure alone cannot explain the observed variation, implying that clinal patterns of genome size are maintained by natural selection. Our modeling additionally provides evidence of selection on individual heterochromatic knob repeats, likely due to their large individual contribution to genome size. To better understand the phenotypes driving selection on genome size, we conducted a growth chamber experiment using a population of highland teosinte exhibiting extensive variation in genome size. We find weak support for a positive correlation between genome size and cell size, but stronger support for a negative correlation between genome size and the rate of cell production. Reanalyzing published data of cell counts in maize shoot apical meristems, we then identify a negative correlation between cell production rate and flowering time. Together, our data suggest a model in which variation in genome size is driven by natural selection on flowering time across altitudinal clines, connecting intraspecific variation in repetitive sequence to important differences in adaptive phenotypes.
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Affiliation(s)
- Paul Bilinski
- Department of Plant Sciences, University of California, Davis, Davis, California, United States of America
- Research Group for Ancient Genomics and Evolution, Department of Molecular Biology, Max Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Patrice S Albert
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, United States of America
| | - Jeremy J Berg
- Center for Population Biology, University of California, Davis, Davis, California, United States of America
- Department of Evolution and Ecology, University of California, Davis, Davis, California, United States of America
| | - James A Birchler
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, United States of America
| | - Mark N Grote
- Department of Anthropology, University of California, Davis, Davis, California, United States of America
| | - Anne Lorant
- Department of Plant Sciences, University of California, Davis, Davis, California, United States of America
| | - Juvenal Quezada
- Department of Plant Sciences, University of California, Davis, Davis, California, United States of America
| | - Kelly Swarts
- Research Group for Ancient Genomics and Evolution, Department of Molecular Biology, Max Planck Institute for Developmental Biology, Tuebingen, Germany
| | - Jinliang Yang
- Department of Plant Sciences, University of California, Davis, Davis, California, United States of America
- Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Jeffrey Ross-Ibarra
- Department of Plant Sciences, University of California, Davis, Davis, California, United States of America
- Center for Population Biology, University of California, Davis, Davis, California, United States of America
- Genome Center, University of California, Davis, Davis, California, United States of America
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47
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Ren X, Li R, Wei X, Bi Y, Ho V, Ding Q, Xu Z, Zhang Z, Hsieh CL, Young A, Zeng J, Liu X, Zhao Z. Genomic basis of recombination suppression in the hybrid between Caenorhabditis briggsae and C. nigoni. Nucleic Acids Res 2018; 46:1295-1307. [PMID: 29325078 PMCID: PMC5814819 DOI: 10.1093/nar/gkx1277] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Revised: 12/07/2017] [Accepted: 12/19/2017] [Indexed: 02/06/2023] Open
Abstract
DNA recombination is required for effective segregation and diversification of genomes and for the successful completion of meiosis. Recent studies in various species hybrids have demonstrated a genetic link between DNA recombination and speciation. Consistent with this, we observed a striking suppression of recombination in the hybrids between two nematodes, the hermaphroditic Caenorhabditis briggsae and the gonochoristic C. nigoni. To unravel the molecular basis underlying the recombination suppression in their hybrids, we generated a C. nigoni genome with chromosome-level contiguity and produced an improved C. briggsae genome with resolved gaps up to 2.8 Mb. The genome alignment reveals not only high sequence divergences but also pervasive intra- and inter-chromosomal sequence re-arrangements between the two species, which are plausible culprits for the observed suppression. Comparison of recombination boundary sequences suggests that recombination in the hybrid requires extensive sequence homology, which is rarely seen between the two genomes. The new genomes and genomic libraries form invaluable resources for studying genome evolution, hybrid incompatibilities and sex evolution for this pair of model species.
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Affiliation(s)
- Xiaoliang Ren
- Department of Biology, Hong Kong Baptist University, Hong Kong, China
| | - Runsheng Li
- Department of Biology, Hong Kong Baptist University, Hong Kong, China
| | - Xiaolin Wei
- MOE Key Laboratory of Bioinformatics, Center for Synthetic and Systems Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
- PTN (Peking University-Tsinghua University-National Institute of Biological Sciences) Joint Graduate Program, Beijing 100084, China
- School of Life Sciences, Peking University, Beijing 100871, China
| | - Yu Bi
- Department of Biology, Hong Kong Baptist University, Hong Kong, China
| | - Vincy Wing Sze Ho
- Department of Biology, Hong Kong Baptist University, Hong Kong, China
| | - Qiutao Ding
- Department of Biology, Hong Kong Baptist University, Hong Kong, China
| | - Zhichao Xu
- MOE Key Laboratory of Bioinformatics, Center for Synthetic and Systems Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Zhihong Zhang
- Illumina Inc., 5200 Illumina Way, San Diego 92122, USA
| | | | - Amanda Young
- Illumina Inc., 5200 Illumina Way, San Diego 92122, USA
| | - Jianyang Zeng
- Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - Xiao Liu
- MOE Key Laboratory of Bioinformatics, Center for Synthetic and Systems Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Zhongying Zhao
- Department of Biology, Hong Kong Baptist University, Hong Kong, China
- State Key Laboratory of Environmental and Biological Analysis, Hong Kong Baptist University, Hong Kong, China
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48
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Yin D, Schwarz EM, Thomas CG, Felde RL, Korf IF, Cutter AD, Schartner CM, Ralston EJ, Meyer BJ, Haag ES. Rapid genome shrinkage in a self-fertile nematode reveals sperm competition proteins. Science 2018; 359:55-61. [PMID: 29302007 PMCID: PMC5789457 DOI: 10.1126/science.aao0827] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 11/17/2017] [Indexed: 12/30/2022]
Abstract
To reveal impacts of sexual mode on genome content, we compared chromosome-scale assemblies of the outcrossing nematode Caenorhabditis nigoni to its self-fertile sibling species, C. briggsaeC. nigoni's genome resembles that of outcrossing relatives but encodes 31% more protein-coding genes than C. briggsaeC. nigoni genes lacking C. briggsae orthologs were disproportionately small and male-biased in expression. These include the male secreted short (mss) gene family, which encodes sperm surface glycoproteins conserved only in outcrossing species. Sperm from mss-null males of outcrossing C. remanei failed to compete with wild-type sperm, despite normal fertility in noncompetitive mating. Restoring mss to C. briggsae males was sufficient to enhance sperm competitiveness. Thus, sex has a pervasive influence on genome content that can be used to identify sperm competition factors.
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Affiliation(s)
- Da Yin
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Erich M Schwarz
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
| | - Cristel G Thomas
- Department of Biology, University of Maryland, College Park, MD 20742, USA
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario M5S 3B2, Canada
| | - Rebecca L Felde
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Ian F Korf
- Department of Molecular and Cellular Biology and Genome Center, University of California, Davis, CA 95616, USA
| | - Asher D Cutter
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario M5S 3B2, Canada
| | - Caitlin M Schartner
- Howard Hughes Medical Institute and Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Edward J Ralston
- Howard Hughes Medical Institute and Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Barbara J Meyer
- Howard Hughes Medical Institute and Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Eric S Haag
- Department of Biology, University of Maryland, College Park, MD 20742, USA.
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49
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GIBSON AMANDAK, MORRAN LEVIT. A Model for Evolutionary Ecology of Disease: The Case for Caenorhabditis Nematodes and Their Natural Parasites. J Nematol 2018. [DOI: 10.21307/jofnem-2017-083] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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50
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Abstract
Nematodes, such as Caenorhabditis elegans, form one of the most species-rich animal phyla. By now more than 30 nematode genomes have been published allowing for comparative genomic analyses at various different time-scales. The majority of a nematode's gene repertoire is represented by either duplicated or so-called orphan genes of unknown origin. This indicates the importance of mechanisms that generate new genes during the course of evolution. While it is certain that nematodes have acquired genes by horizontal gene transfer from various donors, this process only explains a small portion of the nematode gene content. As evolutionary genomic analyses strongly support that most orphan genes are indeed protein-coding, future studies will have to decide, whether they are result from extreme divergence or evolved de novo from previously noncoding sequences. In this contribution, I summarize several studies investigating gene loss and gain in nematodes and discuss the strengths and weaknesses of individual approaches and datasets. These approaches can be used to ask nematode-specific questions such as associated with the evolution of parasitism or with switches in mating systems, but also can complement studies in other animal phyla like vertebrates and insects to broaden our general view on genome evolution.
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Affiliation(s)
- Christian Rödelsperger
- Department for Evolutionary Biology, Max Planck Institute for Developmental Biology, Spemannstr. 35, 72076, Tübingen, Germany.
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