1
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Shpak M, Ghanavi HR, Lange JD, Pool JE, Stensmyr MC. Genomes from historical Drosophila melanogaster specimens illuminate adaptive and demographic changes across more than 200 years of evolution. PLoS Biol 2023; 21:e3002333. [PMID: 37824452 PMCID: PMC10569592 DOI: 10.1371/journal.pbio.3002333] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 09/11/2023] [Indexed: 10/14/2023] Open
Abstract
The ability to perform genomic sequencing on long-dead organisms is opening new frontiers in evolutionary research. These opportunities are especially notable in the case of museum collections, from which countless documented specimens may now be suitable for genomic analysis-if data of sufficient quality can be obtained. Here, we report 25 newly sequenced genomes from museum specimens of the model organism Drosophila melanogaster, including the oldest extant specimens of this species. By comparing historical samples ranging from the early 1800s to 1933 against modern-day genomes, we document evolution across thousands of generations, including time periods that encompass the species' initial occupation of northern Europe and an era of rapidly increasing human activity. We also find that the Lund, Sweden population underwent local genetic differentiation during the early 1800s to 1933 interval (potentially due to drift in a small population) but then became more similar to other European populations thereafter (potentially due to increased migration). Within each century-scale time period, our temporal sampling allows us to document compelling candidates for recent natural selection. In some cases, we gain insights regarding previously implicated selection candidates, such as ChKov1, for which our inferred timing of selection favors the hypothesis of antiviral resistance over insecticide resistance. Other candidates are novel, such as the circadian-related gene Ahcy, which yields a selection signal that rivals that of the DDT resistance gene Cyp6g1. These insights deepen our understanding of recent evolution in a model system, and highlight the potential of future museomic studies.
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Affiliation(s)
- Max Shpak
- Laboratory of Genetics, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | | | - Jeremy D. Lange
- Laboratory of Genetics, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - John E. Pool
- Laboratory of Genetics, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Marcus C. Stensmyr
- Department of Biology, Lund University, Lund, Scania, Sweden
- Max Planck Center on Next Generation Insect Chemical Ecology, Lund, Sweden
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2
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Bruner-Montero G, Luque CM, Cesar CS, Ding SD, Day JP, Jiggins FM. Hunting Drosophila viruses from wild populations: A novel isolation approach and characterisation of viruses. PLoS Pathog 2023; 19:e1010883. [PMID: 36996192 PMCID: PMC10109509 DOI: 10.1371/journal.ppat.1010883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 04/17/2023] [Accepted: 03/08/2023] [Indexed: 04/01/2023] Open
Abstract
Metagenomic studies have demonstrated that viruses are extremely diverse and abundant in insects, but the difficulty of isolating them means little is known about the biology of these newly discovered viruses. To overcome this challenge in Drosophila, we created a cell line that was more permissive to infection and detected novel viruses by the presence of double-stranded RNA. We demonstrate the utility of these tools by isolating La Jolla virus (LJV) and Newfield virus (NFV) from several wild Drosophila populations. These viruses have different potential host ranges, with distinct abilities to replicate in five Drosophila species. Similarly, in some species they cause high mortality and in others they are comparatively benign. In three species, NFV but not LJV caused large declines in female fecundity. This sterilization effect was associated with differences in tissue tropism, as NFV but not LJV was able to infect Drosophila melanogaster ovaries. We saw a similar effect in the invasive pest of fruit crops Drosophila suzukii, where oral infection with NFV caused reductions in the fecundity, suggesting it has potential as a biocontrol agent. In conclusion, a simple protocol allowed us to isolate new viruses and demonstrate that viruses identified by metagenomics have a large effect on the fitness of the model organism D. melanogaster and related species.
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Affiliation(s)
- Gaspar Bruner-Montero
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
- Coiba Scientific Station, City of Knowledge, Clayton, Panama
| | - Carlos M Luque
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Cássia Siqueira Cesar
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
- Ecology Department, Universidade de São Paulo, São Paulo, Brazil
| | | | - Jonathan P Day
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
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3
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Leitão AB, Bian X, Day JP, Pitton S, Demir E, Jiggins FM. Independent effects on cellular and humoral immune responses underlie genotype-by-genotype interactions between Drosophila and parasitoids. PLoS Pathog 2019; 15:e1008084. [PMID: 31589659 PMCID: PMC6797232 DOI: 10.1371/journal.ppat.1008084] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 10/17/2019] [Accepted: 09/16/2019] [Indexed: 11/18/2022] Open
Abstract
It is common to find abundant genetic variation in host resistance and parasite infectivity within populations, with the outcome of infection frequently depending on genotype-specific interactions. Underlying these effects are complex immune defenses that are under the control of both host and parasite genes. We have found extensive variation in Drosophila melanogaster's immune response against the parasitoid wasp Leptopilina boulardi. Some aspects of the immune response, such as phenoloxidase activity, are predominantly affected by the host genotype. Some, such as upregulation of the complement-like protein Tep1, are controlled by the parasite genotype. Others, like the differentiation of immune cells called lamellocytes, depend on the specific combination of host and parasite genotypes. These observations illustrate how the outcome of infection depends on independent genetic effects on different aspects of host immunity. As parasite-killing results from the concerted action of different components of the immune response, these observations provide a physiological mechanism to generate phenomena like epistasis and genotype-interactions that underlie models of coevolution.
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Affiliation(s)
| | - Xueni Bian
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Jonathan P. Day
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Simone Pitton
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Eşref Demir
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
- Antalya Bilim University, Faculty of Engineering, Department of Material Science and Nanotechnology Engineering, Dosemealti, Antalya, Turkey
| | - Francis M. Jiggins
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
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4
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Hall MD, Routtu J, Ebert D. Dissecting the genetic architecture of a stepwise infection process. Mol Ecol 2019; 28:3942-3957. [PMID: 31283079 DOI: 10.1111/mec.15166] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 06/27/2019] [Accepted: 06/28/2019] [Indexed: 02/06/2023]
Abstract
How a host fights infection depends on an ordered sequence of steps, beginning with attempts to prevent a pathogen from establishing an infection, through to steps that mitigate a pathogen's control of host resources or minimize the damage caused during infection. Yet empirically characterizing the genetic basis of these steps remains challenging. Although each step is likely to have a unique genetic and environmental signature, and may therefore respond to selection in different ways, events that occur earlier in the infection process can mask or overwhelm the contributions of subsequent steps. In this study, we dissect the genetic architecture of a stepwise infection process using a quantitative trait locus (QTL) mapping approach. We control for variation at the first line of defence against a bacterial pathogen and expose downstream genetic variability related to the host's ability to mitigate the damage pathogens cause. In our model, the water-flea Daphnia magna, we found a single major effect QTL, explaining 64% of the variance, that is linked to the host's ability to completely block pathogen entry by preventing their attachment to the host oesophagus; this is consistent with the detection of this locus in previous studies. In susceptible hosts allowing attachment, however, a further 23 QTLs, explaining between 5% and 16% of the variance, were mapped to traits related to the expression of disease. The general lack of pleiotropy and epistasis for traits related to the different stages of the infection process, together with the wide distribution of QTLs across the genome, highlights the modular nature of a host's defence portfolio, and the potential for each different step to evolve independently. We discuss how isolating the genetic basis of individual steps can help to resolve discussion over the genetic architecture of host resistance.
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Affiliation(s)
- Matthew D Hall
- Department of Environmental Sciences, Zoology, University of Basel, Basel, Switzerland.,School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | - Jarkko Routtu
- Department of Environmental Sciences, Zoology, University of Basel, Basel, Switzerland.,Molecular Ecology, Martin-Luther-Universität, Halle-Wittenberg, Germany
| | - Dieter Ebert
- Department of Environmental Sciences, Zoology, University of Basel, Basel, Switzerland
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5
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Aparicio R, Rana A, Walker DW. Upregulation of the Autophagy Adaptor p62/SQSTM1 Prolongs Health and Lifespan in Middle-Aged Drosophila. Cell Rep 2019; 28:1029-1040.e5. [PMID: 31340141 PMCID: PMC6688777 DOI: 10.1016/j.celrep.2019.06.070] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 04/21/2019] [Accepted: 06/19/2019] [Indexed: 01/27/2023] Open
Abstract
Autophagy, a lysosomal degradation pathway, plays crucial roles in health and disease. p62/SQSTM1 (hereafter p62) is an autophagy adaptor protein that can shuttle ubiquitinated cargo for autophagic degradation. Here, we show that upregulating the Drosophila p62 homolog ref(2)P/dp62, starting in midlife, delays the onset of pathology and prolongs healthy lifespan. Midlife induction of dp62 improves proteostasis, in aged flies, in an autophagy-dependent manner. Previous studies have reported that p62 plays a role in mediating the clearance of dysfunctional mitochondria via mitophagy. However, the causal relationships between p62 expression, mitochondrial homeostasis, and aging remain largely unexplored. We show that upregulating dp62, in midlife, promotes mitochondrial fission, facilitates mitophagy, and improves mitochondrial function in aged flies. Finally, we show that mitochondrial fission is required for the anti-aging effects of midlife dp62 induction. Our findings indicate that p62 represents a potential therapeutic target to counteract aging and prolong health in aged mammals.
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Affiliation(s)
- Ricardo Aparicio
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Anil Rana
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - David W Walker
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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6
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Duxbury EML, Day JP, Maria Vespasiani D, Thüringer Y, Tolosana I, Smith SCL, Tagliaferri L, Kamacioglu A, Lindsley I, Love L, Unckless RL, Jiggins FM, Longdon B. Host-pathogen coevolution increases genetic variation in susceptibility to infection. eLife 2019; 8:e46440. [PMID: 31038124 PMCID: PMC6491035 DOI: 10.7554/elife.46440] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Accepted: 04/07/2019] [Indexed: 12/31/2022] Open
Abstract
It is common to find considerable genetic variation in susceptibility to infection in natural populations. We have investigated whether natural selection increases this variation by testing whether host populations show more genetic variation in susceptibility to pathogens that they naturally encounter than novel pathogens. In a large cross-infection experiment involving four species of Drosophila and four host-specific viruses, we always found greater genetic variation in susceptibility to viruses that had coevolved with their host. We went on to examine the genetic architecture of resistance in one host species, finding that there are more major-effect genetic variants in coevolved host-pathogen interactions. We conclude that selection by pathogens has increased genetic variation in host susceptibility, and much of this effect is caused by the occurrence of major-effect resistance polymorphisms within populations.
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Affiliation(s)
- Elizabeth ML Duxbury
- Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
- School of Biological SciencesUniversity of East AngliaNorwichUnited Kingdom
| | - Jonathan P Day
- Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| | | | - Yannik Thüringer
- Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| | - Ignacio Tolosana
- Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| | - Sophia CL Smith
- Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| | - Lucia Tagliaferri
- Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| | - Altug Kamacioglu
- Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| | - Imogen Lindsley
- Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| | - Luca Love
- Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| | - Robert L Unckless
- Department of Molecular BiosciencesUniversity of KansasLawrenceUnited States
| | - Francis M Jiggins
- Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
| | - Ben Longdon
- Department of GeneticsUniversity of CambridgeCambridgeUnited Kingdom
- Centre for Ecology and Conservation, BiosciencesUniversity of Exeter (Penryn Campus)CornwallUnited Kingdom
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7
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Abstract
The power and ease of Drosophila genetics and the medical relevance of mosquito-transmitted viruses have made dipterans important model organisms in antiviral immunology. Studies of virus-host interactions at the molecular and population levels have illuminated determinants of resistance to virus infection. Here, we review the sources and nature of variation in antiviral immunity and virus susceptibility in model dipteran insects, specifically the fruit fly Drosophila melanogaster and vector mosquitoes of the genera Aedes and Culex. We first discuss antiviral immune mechanisms and describe the virus-specificity of these responses. In the following sections, we review genetic and microbiota-dependent variation in antiviral immunity. In the final sections, we explore less well-studied sources of variation, including abiotic factors, sexual dimorphism, infection history, and endogenous viral elements. We borrow from work on other pathogen types and non-dipteran species when it parallels or complements studies in dipterans. Understanding natural variation in virus-host interactions may lead to the identification of novel restriction factors and immune mechanisms and shed light on the molecular determinants of vector competence.
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Affiliation(s)
- William H Palmer
- Institute of Evolutionary Biology and Centre for Infection, Evolution and Immunity, University of Edinburgh, Edinburgh EH9 3FL UK.
| | - Finny S Varghese
- Department of Medical Microbiology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, P.O. Box 9101, Nijmegen 6500 HB, The Netherlands.
- Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen 6525 GA, The Netherlands.
| | - Ronald P van Rij
- Department of Medical Microbiology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, P.O. Box 9101, Nijmegen 6500 HB, The Netherlands.
- Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen 6525 GA, The Netherlands.
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8
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van Sluijs L, Pijlman GP, Kammenga JE. Why do Individuals Differ in Viral Susceptibility? A Story Told by Model Organisms. Viruses 2017; 9:E284. [PMID: 28973976 PMCID: PMC5691635 DOI: 10.3390/v9100284] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 09/22/2017] [Accepted: 09/26/2017] [Indexed: 01/30/2023] Open
Abstract
Viral susceptibility and disease progression is determined by host genetic variation that underlies individual differences. Genetic polymorphisms that affect the phenotype upon infection have been well-studied for only a few viruses, such as HIV-1 and Hepatitis C virus. However, even for well-studied viruses the genetic basis of individual susceptibility differences remains elusive. Investigating the effect of causal polymorphisms in humans is complicated, because genetic methods to detect rare or small-effect polymorphisms are limited and genetic manipulation is not possible in human populations. Model organisms have proven a powerful experimental platform to identify and characterize polymorphisms that underlie natural variations in viral susceptibility using quantitative genetic tools. We summarize and compare the genetic tools available in three main model organisms, Mus musculus, Drosophila melanogaster, and Caenorhabditis elegans, and illustrate how these tools can be applied to detect polymorphisms that determine the viral susceptibility. Finally, we analyse how candidate polymorphisms from model organisms can be used to shed light on the underlying mechanism of individual variation. Insights in causal polymorphisms and mechanisms underlying individual differences in viral susceptibility in model organisms likely provide a better understanding in humans.
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Affiliation(s)
- Lisa van Sluijs
- Laboratory of Nematology, Wageningen University, 6708 PB Wageningen, The Netherlands.
- Laboratory of Virology, Wageningen University, 6708 PB Wageningen, The Netherlands.
| | - Gorben P Pijlman
- Laboratory of Virology, Wageningen University, 6708 PB Wageningen, The Netherlands.
| | - Jan E Kammenga
- Laboratory of Nematology, Wageningen University, 6708 PB Wageningen, The Netherlands.
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9
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Magalhães S, Sucena É. Genetics of host-parasite interactions: towards a comprehensive dissection of Drosophila resistance to viral infection. Mol Ecol 2017; 25:4981-4983. [PMID: 27714976 DOI: 10.1111/mec.13834] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 08/26/2016] [Accepted: 08/29/2016] [Indexed: 02/03/2023]
Abstract
One of the major challenges in evolutionary biology is to unravel the genetic basis of adaptation. This issue has been gaining momentum in recent years with the accelerated development of novel genetic and genomic techniques and resources. In this issue of Molecular Ecology, Cogni et al. (2016) address the genetic basis of resistance to two viruses in Drosophila melanogaster using a panel of recombinant inbred lines with unprecedented resolution allowing detection of rare alleles and/or alleles of small effect. The study confirms the role of previously identified genes of major effect and adds novel regions with minor effect to the genetic basis of Drosophila resistance to the Drosophila C virus or the sigma virus. Additional analyses reveal the absence of cross-resistance and of epistasis between the various genomic regions. This detailed information on the genetic architecture of host resistance constitutes an important step towards the understanding of both the physiology of antiviral immunity and the evolution of host-parasite interactions.
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Affiliation(s)
- Sara Magalhães
- cE3c: Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016, Lisboa, Portugal.
| | - Élio Sucena
- Instituto Gulbenkian de Ciências, Apartado 14, 2780-901, Oeiras, Portugal.,Faculdade de Ciências, Departamento de Biologia Animal, Universidade de Lisboa, edifício C2, Campo Grande, 1749-016, Lisboa, Portugal
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10
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Valverde S, Elena SF, Solé R. Spatially induced nestedness in a neutral model of phage-bacteria networks. Virus Evol 2017; 3:vex021. [PMID: 28852574 PMCID: PMC5570086 DOI: 10.1093/ve/vex021] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Ecological networks, both displaying mutualistic or antagonistic interactions, seem to share common structural traits: the presence of nestedness and modularity. A variety of model approaches and hypothesis have been formulated concerning the significance and implications of these properties. In phage-bacteria bipartite infection networks, nestedness seems to be the rule in many different contexts. Modeling the coevolution of a diverse virus-host ensemble is a difficult task, given the dimensionality and multi parametric nature of a standard continuous approximation. Here, we take a different approach, by using a neutral, toy model of host-phage interactions on a spatial lattice. Each individual is represented by a bit string (a digital genome) but all strings in each class (i.e. hosts or phages) share the same sets of parameters. A matching allele model of phage-virus recognition rule is enough to generate a complex, diverse ecosystem with heterogeneous patterns of interaction and nestedness, provided that interactions take place under a spatially constrained setting. It is found that nestedness seems to be an emergent property of the co-evolutionary dynamics. Our results indicate that the enhanced diversity resulting from localized interactions strongly promotes the presence of nested infection matrices.
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Affiliation(s)
- Sergi Valverde
- ICREA-Complex Systems Lab, Universitat Pompeu Fabra, PRBB Dr. Aiguader 88, 08003 Barcelona, Spain
- Institut de Biologia Evolutiva (IBE), Consejo Superior de Investigaciones Científicas - Universitat Pompeu Fabra, Psg. Maritim Barceloneta 37–49, 08003 Barcelona, Spain
| | - Santiago F. Elena
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), CSIC-UPV, 46022 Valencia, Spain
- Instituto de Biología Integrativa de Sistemas (I2SysBio), Consejo Superior de Investigaciones Científicas-Universitat de Valencia, Paterna, 46182 Valencia, Spain
- Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA
| | - Ricard Solé
- ICREA-Complex Systems Lab, Universitat Pompeu Fabra, PRBB Dr. Aiguader 88, 08003 Barcelona, Spain
- Institut de Biologia Evolutiva (IBE), Consejo Superior de Investigaciones Científicas - Universitat Pompeu Fabra, Psg. Maritim Barceloneta 37–49, 08003 Barcelona, Spain
- Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA
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11
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Ashby B, Boots M. Multi-mode fluctuating selection in host-parasite coevolution. Ecol Lett 2017; 20:357-365. [DOI: 10.1111/ele.12734] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 09/30/2016] [Accepted: 12/19/2016] [Indexed: 01/06/2023]
Affiliation(s)
- Ben Ashby
- Department of Mathematical Sciences; University of Bath; Bath BA2 7AY UK
- Integrative Biology; University of California Berkeley; Berkeley CA USA
| | - Mike Boots
- Integrative Biology; University of California Berkeley; Berkeley CA USA
- Department of Biosciences, College of Life and Environmental Sciences; University of Exeter; Penryn TR10 9EZ UK
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12
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Longdon B, Day JP, Schulz N, Leftwich PT, de Jong MA, Breuker CJ, Gibbs M, Obbard DJ, Wilfert L, Smith SCL, McGonigle JE, Houslay TM, Wright LI, Livraghi L, Evans LC, Friend LA, Chapman T, Vontas J, Kambouraki N, Jiggins FM. Vertically transmitted rhabdoviruses are found across three insect families and have dynamic interactions with their hosts. Proc Biol Sci 2017; 284:20162381. [PMID: 28100819 PMCID: PMC5310039 DOI: 10.1098/rspb.2016.2381] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 12/20/2016] [Indexed: 11/17/2022] Open
Abstract
A small number of free-living viruses have been found to be obligately vertically transmitted, but it remains uncertain how widespread vertically transmitted viruses are and how quickly they can spread through host populations. Recent metagenomic studies have found several insects to be infected with sigma viruses (Rhabdoviridae). Here, we report that sigma viruses that infect Mediterranean fruit flies (Ceratitis capitata), Drosophila immigrans, and speckled wood butterflies (Pararge aegeria) are all vertically transmitted. We find patterns of vertical transmission that are consistent with those seen in Drosophila sigma viruses, with high rates of maternal transmission, and lower rates of paternal transmission. This mode of transmission allows them to spread rapidly in populations, and using viral sequence data we found the viruses in D. immigrans and C. capitata had both recently swept through host populations. The viruses were common in nature, with mean prevalences of 12% in C. capitata, 38% in D. immigrans and 74% in P. aegeria We conclude that vertically transmitted rhabdoviruses may be widespread in a broad range of insect taxa, and that these viruses can have dynamic interactions with their hosts.
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Affiliation(s)
- Ben Longdon
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
| | - Jonathan P Day
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
| | - Nora Schulz
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Philip T Leftwich
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Maaike A de Jong
- School of Biological Sciences, University of Bristol, Bristol Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Casper J Breuker
- Evolutionary Developmental Biology Research Group, Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Gipsy Lane, Headington, Oxford OX3 0BP, UK
| | - Melanie Gibbs
- NERC Centre for Ecology and Hydrology, Crowmarsh Gifford, Maclean Building, Wallingford, Oxfordshire OX10 8BB, UK
| | - Darren J Obbard
- Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK
| | - Lena Wilfert
- Centre for Ecology and Conservation, Biosciences, College of Life and Environmental Sciences, University of Exeter, Penryn Campus TR10 9FE, UK
| | - Sophia C L Smith
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
| | - John E McGonigle
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
| | - Thomas M Houslay
- Centre for Ecology and Conservation, Biosciences, College of Life and Environmental Sciences, University of Exeter, Penryn Campus TR10 9FE, UK
| | - Lucy I Wright
- Centre for Ecology and Conservation, Biosciences, College of Life and Environmental Sciences, University of Exeter, Penryn Campus TR10 9FE, UK
- Zoological Society of London, Regent's Park, London NW1 4RY, UK
| | - Luca Livraghi
- Evolutionary Developmental Biology Research Group, Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Gipsy Lane, Headington, Oxford OX3 0BP, UK
| | - Luke C Evans
- Evolutionary Developmental Biology Research Group, Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Gipsy Lane, Headington, Oxford OX3 0BP, UK
- Ecology and Evolutionary Biology Research Division, School of Biological Sciences, University of Reading, Whiteknights, Reading RG6 6AS, UK
| | - Lucy A Friend
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Tracey Chapman
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - John Vontas
- Lab Pesticide Science, Agricultural University of Athens, Iera Odos 75, 11855, Athens, Greece
- Molecular Entomology, Institute Molecular Biology and Biotechnology/Foundation for Research and Technology, Voutes, 70013, Heraklio, Crete, Greece
| | - Natasa Kambouraki
- Lab Pesticide Science, Agricultural University of Athens, Iera Odos 75, 11855, Athens, Greece
- Molecular Entomology, Institute Molecular Biology and Biotechnology/Foundation for Research and Technology, Voutes, 70013, Heraklio, Crete, Greece
| | - Francis M Jiggins
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK
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13
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Cogni R, Cao C, Day JP, Bridson C, Jiggins FM. The genetic architecture of resistance to virus infection in Drosophila. Mol Ecol 2016; 25:5228-5241. [PMID: 27460507 PMCID: PMC5082504 DOI: 10.1111/mec.13769] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 07/03/2016] [Accepted: 07/05/2016] [Indexed: 12/18/2022]
Abstract
Variation in susceptibility to infection has a substantial genetic component in natural populations, and it has been argued that selection by pathogens may result in it having a simpler genetic architecture than many other quantitative traits. This is important as models of host-pathogen co-evolution typically assume resistance is controlled by a small number of genes. Using the Drosophila melanogaster multiparent advanced intercross, we investigated the genetic architecture of resistance to two naturally occurring viruses, the sigma virus and DCV (Drosophila C virus). We found extensive genetic variation in resistance to both viruses. For DCV resistance, this variation is largely caused by two major-effect loci. Sigma virus resistance involves more genes - we mapped five loci, and together these explained less than half the genetic variance. Nonetheless, several of these had a large effect on resistance. Models of co-evolution typically assume strong epistatic interactions between polymorphisms controlling resistance, but we were only able to detect one locus that altered the effect of the main effect loci we had mapped. Most of the loci we mapped were probably at an intermediate frequency in natural populations. Overall, our results are consistent with major-effect genes commonly affecting susceptibility to infectious diseases, with DCV resistance being a near-Mendelian trait.
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Affiliation(s)
- Rodrigo Cogni
- Department of Genetics, University of Cambridge, Cambridge, CB2 3EH, UK.
- Department of Ecology, University of São Paulo, São Paulo, 05508-900, Brazil.
| | - Chuan Cao
- Department of Genetics, University of Cambridge, Cambridge, CB2 3EH, UK
| | - Jonathan P Day
- Department of Genetics, University of Cambridge, Cambridge, CB2 3EH, UK
| | - Calum Bridson
- Department of Genetics, University of Cambridge, Cambridge, CB2 3EH, UK
| | - Francis M Jiggins
- Department of Genetics, University of Cambridge, Cambridge, CB2 3EH, UK
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14
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Croze M, Živković D, Stephan W, Hutter S. Balancing selection on immunity genes: review of the current literature and new analysis in Drosophila melanogaster. ZOOLOGY 2016; 119:322-9. [PMID: 27106015 DOI: 10.1016/j.zool.2016.03.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 02/11/2016] [Accepted: 03/16/2016] [Indexed: 12/18/2022]
Abstract
Balancing selection has been widely assumed to be an important evolutionary force, yet even today little is known about its abundance and its impact on the patterns of genetic diversity. Several studies have shown examples of balancing selection in humans, plants or parasites, and many genes under balancing selection are involved in immunity. It has been proposed that host-parasite coevolution is one of the main forces driving immune genes to evolve under balancing selection. In this paper, we review the literature on balancing selection on immunity genes in several organisms, including Drosophila. Furthermore, we performed a genome scan for balancing selection in an African population of Drosophila melanogaster using coalescent simulations of a demographic model with and without selection. We find very few genes under balancing selection and only one novel candidate gene related to immunity. Finally, we discuss the possible causes of the low number of genes under balancing selection.
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Affiliation(s)
- Myriam Croze
- Department of Biology II, Ludwig Maximilian University Munich, Großhaderner Str. 2, D-82152 Planegg-Martinsried, Germany.
| | - Daniel Živković
- Department of Biology II, Ludwig Maximilian University Munich, Großhaderner Str. 2, D-82152 Planegg-Martinsried, Germany
| | - Wolfgang Stephan
- Department of Biology II, Ludwig Maximilian University Munich, Großhaderner Str. 2, D-82152 Planegg-Martinsried, Germany
| | - Stephan Hutter
- Department of Biology II, Ludwig Maximilian University Munich, Großhaderner Str. 2, D-82152 Planegg-Martinsried, Germany
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15
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Cao C, Magwire MM, Bayer F, Jiggins FM. A Polymorphism in the Processing Body Component Ge-1 Controls Resistance to a Naturally Occurring Rhabdovirus in Drosophila. PLoS Pathog 2016; 12:e1005387. [PMID: 26799957 PMCID: PMC4723093 DOI: 10.1371/journal.ppat.1005387] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 12/17/2015] [Indexed: 12/30/2022] Open
Abstract
Hosts encounter an ever-changing array of pathogens, so there is continual selection for novel ways to resist infection. A powerful way to understand how hosts evolve resistance is to identify the genes that cause variation in susceptibility to infection. Using high-resolution genetic mapping we have identified a naturally occurring polymorphism in a gene called Ge-1 that makes Drosophila melanogaster highly resistant to its natural pathogen Drosophila melanogaster sigma virus (DMelSV). By modifying the sequence of the gene in transgenic flies, we identified a 26 amino acid deletion in the serine-rich linker region of Ge-1 that is causing the resistance. Knocking down the expression of the susceptible allele leads to a decrease in viral titre in infected flies, indicating that Ge-1 is an existing restriction factor whose antiviral effects have been increased by the deletion. Ge-1 plays a central role in RNA degradation and the formation of processing bodies (P bodies). A key effector in antiviral immunity, the RNAi induced silencing complex (RISC), localises to P bodies, but we found that Ge-1-based resistance is not dependent on the small interfering RNA (siRNA) pathway. However, we found that Decapping protein 1 (DCP1) protects flies against sigma virus. This protein interacts with Ge-1 and commits mRNA for degradation by removing the 5’ cap, suggesting that resistance may rely on this RNA degradation pathway. The serine-rich linker domain of Ge-1 has experienced strong selection during the evolution of Drosophila, suggesting that this gene may be under long-term selection by viruses. These findings demonstrate that studying naturally occurring polymorphisms that increase resistance to infections enables us to identify novel forms of antiviral defence, and support a pattern of major effect polymorphisms controlling resistance to viruses in Drosophila. Hosts and their pathogens are engaged in a never-ending arms race, and hosts must continually evolve new defences to protect themselves from infection. In the fruit fly Drosophila melanogaster we show that virus resistance can evolve through a single mutation. In flies that are highly resistant to a naturally occurring virus called sigma virus we identified a deletion in the protein-coding region of a gene called Ge-1. We experimentally confirmed that this was the cause of resistance by deleting this region in transgenic flies. Furthermore, we show that even the susceptible allele of Ge-1 helps protect flies against the virus, suggesting that this mutation has made an existing antiviral defence more effective. Ge-1 plays a central role in RNA degradation in regions of the cytoplasm called P bodies, and our results suggest that this pathway has been recruited during evolution to protect D. melanogaster against sigma virus. The protein domain that contains the deletion has experienced strong selection during its evolution, suggesting that it may be involved in an ongoing arms race with viruses.
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Affiliation(s)
- Chuan Cao
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
| | - Michael M. Magwire
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Florian Bayer
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Francis M. Jiggins
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
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16
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Cassone BJ, Cisneros Carter FM, Michel AP, Stewart LR, Redinbaugh MG. Genetic insights into Graminella nigrifrons Competence for maize fine streak virus infection and transmission. PLoS One 2014; 9:e113529. [PMID: 25420026 PMCID: PMC4242632 DOI: 10.1371/journal.pone.0113529] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 10/29/2014] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Most plant-infecting rhabdoviruses are transmitted by one or a few closely related insect species. Additionally, intraspecific differences in transmission efficacy often exist among races/biotypes within vector species and among strains within a virus species. The black-faced leafhopper, Graminella nigrifrons, is the only known vector of the persistent propagative rhabdovirus Maize fine streak virus (MFSV). Only a small percentage of leafhoppers are capable of transmitting the virus, although the mechanisms underlying vector competence are not well understood. METHODOLOGY RNA-Seq was carried out to explore transcript expression changes and sequence variation in G. nigrifrons and MFSV that may be associated with the ability of the vector to acquire and transmit the virus. RT-qPCR assays were used to validate differential transcript accumulation. RESULTS/SIGNIFICANCE Feeding on MFSV-infected maize elicited a considerable transcriptional response in G. nigrifrons, with increased expression of cytoskeleton organization and immunity transcripts in infected leafhoppers. Differences between leafhoppers capable of transmitting MFSV, relative to non-transmitting but infected leafhoppers were more limited, which may reflect difficulties discerning between the two groups and/or the likelihood that the transmitter phenotype results from one or a few genetic differences. The ability of infected leafhoppers to transmit MFSV did not appear associated with virus transcript accumulation in the infected leafhoppers or sequence polymorphisms in the viral genome. However, the non-structural MFSV 3 gene was expressed at unexpectedly high levels in infected leafhoppers, suggesting it plays an active role in the infection of the insect host. The results of this study begin to define the functional roles of specific G. nigrifrons and MFSV genes in the viral transmission process.
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Affiliation(s)
- Bryan J. Cassone
- United States Department of Agriculture- Agricultural Research Service, Corn, Soybean and Wheat Quality Research Unit, Ohio Agricultural Research and Development Center (OARDC), Wooster, Ohio, United States of America
| | - Fiorella M. Cisneros Carter
- Department of Plant Pathology, Ohio Agricultural Research and Development Center (OARDC), The Ohio State University, Wooster, Ohio, United States of America
| | - Andrew P. Michel
- Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center (OARDC), The Ohio State University, Wooster, Ohio, United States of America
| | - Lucy R. Stewart
- United States Department of Agriculture- Agricultural Research Service, Corn, Soybean and Wheat Quality Research Unit, Ohio Agricultural Research and Development Center (OARDC), Wooster, Ohio, United States of America
- Department of Plant Pathology, Ohio Agricultural Research and Development Center (OARDC), The Ohio State University, Wooster, Ohio, United States of America
| | - Margaret G. Redinbaugh
- United States Department of Agriculture- Agricultural Research Service, Corn, Soybean and Wheat Quality Research Unit, Ohio Agricultural Research and Development Center (OARDC), Wooster, Ohio, United States of America
- Department of Plant Pathology, Ohio Agricultural Research and Development Center (OARDC), The Ohio State University, Wooster, Ohio, United States of America
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17
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Obbard DJ, Dudas G. The genetics of host-virus coevolution in invertebrates. Curr Opin Virol 2014; 8:73-8. [PMID: 25063907 PMCID: PMC4199324 DOI: 10.1016/j.coviro.2014.07.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 06/30/2014] [Accepted: 07/03/2014] [Indexed: 11/19/2022]
Abstract
Although viral infection and antiviral defence are ubiquitous, genetic data are currently unavailable from the vast majority of animal phyla-potentially biasing our overall perspective of the coevolutionary process. Rapid adaptive evolution is seen in some insect antiviral genes, consistent with invertebrate-virus 'arms-race' coevolution, but equivalent signatures of selection are hard to detect in viruses. We find that, despite the large differences in vertebrate, invertebrate, and plant immune responses, comparison of viral evolution fails to identify any difference among these hosts in the impact of positive selection. The best evidence for invertebrate-virus coevolution is currently provided by large-effect polymorphisms for host resistance and/or viral evasion, as these often appear to have arisen and spread recently, and can be favoured by virus-mediated selection.
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Affiliation(s)
- Darren J Obbard
- Institute of Evolutionary Biology, University of Edinburgh, Kings Buildings, Edinburgh, UK; Centre for Infection Immunity and Evolution, University of Edinburgh, Kings Buildings, Edinburgh, UK.
| | - Gytis Dudas
- Institute of Evolutionary Biology, University of Edinburgh, Kings Buildings, Edinburgh, UK
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18
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Dheilly NM, Adema C, Raftos DA, Gourbal B, Grunau C, Du Pasquier L. No more non-model species: the promise of next generation sequencing for comparative immunology. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2014; 45:56-66. [PMID: 24508980 PMCID: PMC4096995 DOI: 10.1016/j.dci.2014.01.022] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 01/20/2014] [Accepted: 01/21/2014] [Indexed: 05/21/2023]
Abstract
Next generation sequencing (NGS) allows for the rapid, comprehensive and cost effective analysis of entire genomes and transcriptomes. NGS provides approaches for immune response gene discovery, profiling gene expression over the course of parasitosis, studying mechanisms of diversification of immune receptors and investigating the role of epigenetic mechanisms in regulating immune gene expression and/or diversification. NGS will allow meaningful comparisons to be made between organisms from different taxa in an effort to understand the selection of diverse strategies for host defence under different environmental pathogen pressures. At the same time, it will reveal the shared and unique components of the immunological toolkit and basic functional aspects that are essential for immune defence throughout the living world. In this review, we argue that NGS will revolutionize our understanding of immune responses throughout the animal kingdom because the depth of information it provides will circumvent the need to concentrate on a few "model" species.
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Affiliation(s)
- Nolwenn M Dheilly
- CNRS, UMR 5244, Ecologie et Evolution des Interactions (2EI), Perpignan F-66860, France; Université de Perpignan Via Domitia, Perpignan F-66860, France.
| | - Coen Adema
- Center for Evolutionary and Theoretical Immunology, Biology Department, University of New Mexico, Albuquerque, NM 87131, USA
| | - David A Raftos
- Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia
| | - Benjamin Gourbal
- CNRS, UMR 5244, Ecologie et Evolution des Interactions (2EI), Perpignan F-66860, France; Université de Perpignan Via Domitia, Perpignan F-66860, France
| | - Christoph Grunau
- CNRS, UMR 5244, Ecologie et Evolution des Interactions (2EI), Perpignan F-66860, France; Université de Perpignan Via Domitia, Perpignan F-66860, France
| | - Louis Du Pasquier
- University of Basel, Institute of Zoology and Evolutionary Biology, Basel, Switzerland
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19
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Wilfert L, Jiggins FM. Flies on the move: an inherited virus mirrors Drosophila melanogaster's elusive ecology and demography. Mol Ecol 2014; 23:2093-104. [PMID: 24597631 DOI: 10.1111/mec.12709] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 02/27/2014] [Accepted: 02/28/2014] [Indexed: 11/30/2022]
Abstract
Vertically transmitted parasites rely on their host's reproduction for their transmission, leading to the evolutionary histories of both parties being intimately entwined. Parasites can thus serve as a population genetic magnifying glass for their host's demographic history. Here, we study the fruitfly Drosophila melanogaster's vertically transmitted sigma virus DMelSV. The virus has a high mutation rate and low effective population size, allowing us to reconstruct at a fine scale how the combined forces of the movement of flies and selection on the virus have shaped its migration patterns. We found that the virus is likely to have spread to Europe from Africa, mirroring the colonization route of Drosophila. The North American DMelSV population appears to be the result of a recent single immigration from Europe, invading together with its host in the late 19th century. Across Europe, DMelSV migration rates are low and populations are highly genetically structured, likely reflecting limited fly movement. Despite being intolerant of extreme cold, viral diversity suggests that fly populations can persist in harsh continental climates and that recolonization from the warmer south plays a minor role. In conclusion, studying DMelSV can provide insights into the poorly understood ecology of D. melanogaster, one of the best-studied organisms in biology.
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Affiliation(s)
- Lena Wilfert
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, TR10 9FE, UK
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20
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Keebaugh ES, Schlenke TA. Insights from natural host-parasite interactions: the Drosophila model. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2014; 42:111-23. [PMID: 23764256 PMCID: PMC3808516 DOI: 10.1016/j.dci.2013.06.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2013] [Revised: 06/01/2013] [Accepted: 06/01/2013] [Indexed: 05/15/2023]
Abstract
Immune responses against opportunistic pathogens have been extensively studied in Drosophila, leading to a detailed map of the genetics behind innate immunity networks including the Toll, Imd, Jak-Stat, and JNK pathways. However, immune mechanisms of other organisms, such as plants, have primarily been investigated using natural pathogens. It was the use of natural pathogens in plant research that revealed the plant R-Avr system, a specialized immune response derived from antagonistic coevolution between plant immune proteins and their natural pathogens' virulence proteins. Thus, we recommend that researchers begin to use natural Drosophila pathogens to identify novel immune strategies that may have arisen through antagonistic coevolution with common natural pathogens. In this review, we address the benefits of using natural pathogens in research, describe the known natural pathogens of Drosophila, and discuss the future prospects for research on natural pathogens of Drosophila.
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Affiliation(s)
- Erin S Keebaugh
- Department of Biology, Emory University, 1510 Clifton Road, Atlanta, GA, United States.
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21
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Hall MD, Ebert D. The genetics of infectious disease susceptibility: has the evidence for epistasis been overestimated? BMC Biol 2013; 11:79. [PMID: 23855805 PMCID: PMC3711976 DOI: 10.1186/1741-7007-11-79] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Accepted: 07/08/2013] [Indexed: 12/30/2022] Open
Abstract
Interactions amongst genes, known as epistasis, are assumed to make a substantial contribution to the genetic variation in infectious disease susceptibility, but this claim is controversial. Here, we focus on the debate surrounding the evolutionary importance of interactions between resistance loci and argue that its role in explaining overall variance in disease outcomes may have been overestimated.
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Affiliation(s)
- Matthew D Hall
- University of Basel, Zoological Institute, Vesalgasse 1, Basel, CH-4051, Switzerland.
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22
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Susi H, Laine AL. Pathogen life-history trade-offs revealed in allopatry. Evolution 2013; 67:3362-70. [PMID: 24152013 PMCID: PMC4208680 DOI: 10.1111/evo.12182] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 05/29/2013] [Indexed: 11/29/2022]
Abstract
Trade-offs in life-history traits is a central tenet in evolutionary biology, yet their ubiquity and relevance to realized fitness in natural populations remains questioned. Trade-offs in pathogens are of particular interest because they may constrain the evolution and epidemiology of diseases. Here, we studied life-history traits determining transmission in the obligate fungal pathogen, Podosphaera plantaginis, infecting Plantago lanceolata. We find that although traits are positively associated on sympatric host genotypes, on allopatric host genotypes relationships between infectivity and subsequent transmission traits change shape, becoming even negative. The epidemiological prediction of this change in life-history relationships in allopatry is lower disease prevalence in newly established pathogen populations. An analysis of the natural pathogen metapopulation confirms that disease prevalence is lower in newly established pathogen populations and they are more prone to go extinct during winter than older pathogen populations. Hence, life-history trade-offs mediated by pathogen local adaptation may influence epidemiological dynamics at both population and metapopulation levels.
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Affiliation(s)
- Hanna Susi
- Metapopulation Research Group, PO Box 65 (Viikinkaari 1), Department of Biosciences, FI-00014 University of Helsinki, Finland
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23
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Wilfert L, Jiggins FM. The dynamics of reciprocal selective sweeps of host resistance and a parasite counter-adaptation in Drosophila. Evolution 2012; 67:761-73. [PMID: 23461326 DOI: 10.1111/j.1558-5646.2012.01832.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Host-parasite coevolution can result in consecutive selective sweeps of host resistance alleles and parasite counter-adaptations. To illustrate the dynamics of this important but little studied form of coevolution, we have modeled an ongoing arms race between Drosophila melanogaster and the vertically transmitted sigma virus, using parameters we estimated in the field. We integrate these results with previous work showing that the spread of a resistance allele of the ref(2)P gene in the host was followed by the spread of a virus genotype, which overcomes this resistance. In line with these observations, our model predicts that there can be rapid selective sweeps in both the host and parasite, which can drive large changes in the prevalence of infection. The virus will tend to be ahead in the arms race, as incomplete dominance slows down host adaptation and selection for host resistance is weaker than selection for parasites to overcome resistance--the "life-dinner" principle. This asymmetry in the adaptation rates results in a partial sweep of the host resistance allele, as it loses its advantage part way through the selective sweep. This well-understood natural system illustrates how the outcome of host-parasite coevolution is determined by different population genetic parameters in the field.
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Affiliation(s)
- Lena Wilfert
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, United Kingdom.
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24
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Magwire MM, Fabian DK, Schweyen H, Cao C, Longdon B, Bayer F, Jiggins FM. Genome-wide association studies reveal a simple genetic basis of resistance to naturally coevolving viruses in Drosophila melanogaster. PLoS Genet 2012; 8:e1003057. [PMID: 23166512 PMCID: PMC3499358 DOI: 10.1371/journal.pgen.1003057] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Accepted: 09/14/2012] [Indexed: 12/04/2022] Open
Abstract
Variation in susceptibility to infectious disease often has a substantial genetic component in animal and plant populations. We have used genome-wide association studies (GWAS) in Drosophila melanogaster to identify the genetic basis of variation in susceptibility to viral infection. We found that there is substantially more genetic variation in susceptibility to two viruses that naturally infect D. melanogaster (DCV and DMelSV) than to two viruses isolated from other insects (FHV and DAffSV). Furthermore, this increased variation is caused by a small number of common polymorphisms that have a major effect on resistance and can individually explain up to 47% of the heritability in disease susceptibility. For two of these polymorphisms, it has previously been shown that they have been driven to a high frequency by natural selection. An advantage of GWAS in Drosophila is that the results can be confirmed experimentally. We verified that a gene called pastrel--which was previously not known to have an antiviral function--is associated with DCV-resistance by knocking down its expression by RNAi. Our data suggest that selection for resistance to infectious disease can increase genetic variation by increasing the frequency of major-effect alleles, and this has resulted in a simple genetic basis to variation in virus resistance.
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Affiliation(s)
| | | | | | | | | | | | - Francis M. Jiggins
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
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25
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Longdon B, Jiggins FM. Vertically transmitted viral endosymbionts of insects: do sigma viruses walk alone? Proc Biol Sci 2012; 279:3889-98. [PMID: 22859592 PMCID: PMC3427579 DOI: 10.1098/rspb.2012.1208] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Accepted: 07/06/2012] [Indexed: 01/10/2023] Open
Abstract
Insects are host to a wide range of vertically transmitted bacterial endosymbionts, but we know relatively little about their viral counterparts. Here, we discuss the vertically transmitted viral endosymbionts of insects, firstly examining the diversity of this group, and then focusing on the well-studied sigma viruses that infect dipterans. Despite limited sampling, evidence suggests that vertically transmitted viruses may be common in insects. Unlike bacteria, viruses can be transmitted through sperm and eggs, a trait that allows them to rapidly spread through host populations even when infection is costly to the host. Work on Drosophila melanogaster has shown that sigma viruses and their hosts are engaged in a coevolutionary arms race, in which the spread of resistance genes in the host population is followed by the spread of viral genotypes that can overcome host resistance. In the long-term, associations between sigma viruses and their hosts are unstable, and the viruses persist by occasionally switching to new host species. It therefore seems likely that viral endosymbionts have major impacts on the evolution and ecology of insects.
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Affiliation(s)
- Ben Longdon
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK.
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26
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Tack AJM, Thrall PH, Barrett LG, Burdon JJ, Laine AL. Variation in infectivity and aggressiveness in space and time in wild host-pathogen systems: causes and consequences. J Evol Biol 2012; 25:1918-1936. [PMID: 22905782 DOI: 10.1111/j.1420-9101.2012.02588.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 07/02/2012] [Accepted: 07/05/2012] [Indexed: 12/18/2022]
Abstract
Variation in host resistance and in the ability of pathogens to infect and grow (i.e. pathogenicity) is important as it provides the raw material for antagonistic (co)evolution and therefore underlies risks of disease spread, disease evolution and host shifts. Moreover, the distribution of this variation in space and time may inform us about the mode of coevolutionary selection (arms race vs. fluctuating selection dynamics) and the relative roles of G × G interactions, gene flow, selection and genetic drift in shaping coevolutionary processes. Although variation in host resistance has recently been reviewed, little is known about overall patterns in the frequency and scale of variation in pathogenicity, particularly in natural systems. Using 48 studies from 30 distinct host-pathogen systems, this review demonstrates that variation in pathogenicity is ubiquitous across multiple spatial and temporal scales. Quantitative analysis of a subset of extensively studied plant-pathogen systems shows that the magnitude of within-population variation in pathogenicity is large relative to among-population variation and that the distribution of pathogenicity partly mirrors the distribution of host resistance. At least part of the variation in pathogenicity found at a given spatial scale is adaptive, as evidenced by studies that have examined local adaptation at scales ranging from single hosts through metapopulations to entire continents and - to a lesser extent - by comparisons of pathogenicity with neutral genetic variation. Together, these results support coevolutionary selection through fluctuating selection dynamics. We end by outlining several promising directions for future research.
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Affiliation(s)
- A J M Tack
- Metapopulation Research Group, Department of Biosciences, University of Helsinki, Helsinki, Finland
| | - P H Thrall
- CSIRO-Plant Industry, Canberra, ACT, Australia
| | - L G Barrett
- CSIRO-Plant Industry, Canberra, ACT, Australia
| | - J J Burdon
- CSIRO-Plant Industry, Canberra, ACT, Australia
| | - A-L Laine
- Metapopulation Research Group, Department of Biosciences, University of Helsinki, Helsinki, Finland
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27
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Nezis IP. Selective autophagy in Drosophila. Int J Cell Biol 2012; 2012:146767. [PMID: 22567011 PMCID: PMC3332208 DOI: 10.1155/2012/146767] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 02/01/2012] [Accepted: 02/03/2012] [Indexed: 11/26/2022] Open
Abstract
Autophagy is an evolutionarily conserved process of cellular self-eating and is a major pathway for degradation of cytoplasmic material by the lysosomal machinery. Autophagy functions as a cellular response in nutrient starvation, but it is also associated with the removal of protein aggregates and damaged organelles and therefore plays an important role in the quality control of proteins and organelles. Although it was initially believed that autophagy occurs randomly in the cell, during the last years, there is growing evidence that sequestration and degradation of cytoplasmic material by autophagy can be selective. Given the important role of autophagy and selective autophagy in several disease-related processes such as neurodegeneration, infections, and tumorigenesis, it is important to understand the molecular mechanisms of selective autophagy, especially at the organismal level. Drosophila is an excellent genetically modifiable model organism exhibiting high conservation in the autophagic machinery. However, the regulation and mechanisms of selective autophagy in Drosophila have been largely unexplored. In this paper, I will present an overview of the current knowledge about selective autophagy in Drosophila.
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Affiliation(s)
- Ioannis P. Nezis
- Department of Biochemistry, Institute for Cancer Research, Oslo University Hospital, Montebello, 0310 Oslo, Norway
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, 0310 Oslo, Norway
- Laboratory of Cell Biology, Department of Biological Applications and Technologies, University of Ioannina, 45110 Ioannina, Greece
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Carpenter JA, Hadfield JD, Bangham J, Jiggins FM. Specific interactions between host and parasite genotypes do not act as a constraint on the evolution of antiviral resistance in Drosophila. Evolution 2011; 66:1114-25. [PMID: 22486692 DOI: 10.1111/j.1558-5646.2011.01501.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Genetic correlations between parasite resistance and other traits can act as an evolutionary constraint and prevent a population from evolving increased resistance. For example, previous studies have found negative genetic correlations between host resistance and life-history traits. In invertebrates, the level of resistance often depends on the combination of the host and parasite genotypes, and in this study, we have investigated whether such specific resistance also acts as an evolutionary constraint. We measured the resistance of different genotypes of the fruit fly Drosophila melanogaster to different genotypes of a naturally occurring pathogen, the sigma virus. Using a multitrait analysis, we examine whether genetic covariances alter the potential to select for general resistance against all of the different viral genotypes. We found large amounts of heritable variation in resistance, and evidence for specific interactions between host and parasite, but these interactions resulted in little constraint on Drosophila evolving greater resistance.
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Affiliation(s)
- Jennifer A Carpenter
- Institute of Evolutionary Biology, University of Edinburgh, Edinburgh EH9 3JT, UK.
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29
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Longdon B, Wilfert L, Osei-Poku J, Cagney H, Obbard DJ, Jiggins FM. Host-switching by a vertically transmitted rhabdovirus in Drosophila. Biol Lett 2011; 7:747-50. [PMID: 21450721 PMCID: PMC3169049 DOI: 10.1098/rsbl.2011.0160] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Accepted: 03/07/2011] [Indexed: 11/12/2022] Open
Abstract
A diverse range of endosymbionts are found within the cells of animals. As these endosymbionts are normally vertically transmitted, we might expect their evolutionary history to be dominated by host-fidelity and cospeciation with the host. However, studies of bacterial endosymbionts have shown that while this is true for some mutualists, parasites often move horizontally between host lineages over evolutionary timescales. For the first time, to our knowledge, we have investigated whether this is also the case for vertically transmitted viruses. Here, we describe four new sigma viruses, a group of vertically transmitted rhabdoviruses previously known in Drosophila. Using sequence data from these new viruses, and the previously described sigma viruses, we show that they have switched between hosts during their evolutionary history. Our results suggest that sigma virus infections may be short-lived in a given host lineage, so that their long-term persistence relies on rare horizontal transmission events between hosts.
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Affiliation(s)
- Ben Longdon
- Institute of Evolutionary Biology, Centre for Immunity, Infection and Evolution, University of Edinburgh, Edinburgh EH9 3JT, UK.
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30
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Affiliation(s)
- Joshua M. Schmidt
- Genetics Department, The University of Melbourne, Melbourne, Australia
| | - Charles Robin
- Genetics Department, The University of Melbourne, Melbourne, Australia
- * E-mail:
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31
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Magwire MM, Bayer F, Webster CL, Cao C, Jiggins FM. Successive increases in the resistance of Drosophila to viral infection through a transposon insertion followed by a Duplication. PLoS Genet 2011; 7:e1002337. [PMID: 22028673 PMCID: PMC3197678 DOI: 10.1371/journal.pgen.1002337] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Accepted: 08/22/2011] [Indexed: 11/30/2022] Open
Abstract
To understand the molecular basis of how hosts evolve resistance to their parasites, we have investigated the genes that cause variation in the susceptibility of Drosophila melanogaster to viral infection. Using a host-specific pathogen of D. melanogaster called the sigma virus (Rhabdoviridae), we mapped a major-effect polymorphism to a region containing two paralogous genes called CHKov1 and CHKov2. In a panel of inbred fly lines, we found that a transposable element insertion in the protein coding sequence of CHKov1 is associated with increased resistance to infection. Previous research has shown that this insertion results in a truncated messenger RNA that encodes a far shorter protein than the susceptible allele. This resistant allele has rapidly increased in frequency under directional selection and is now the commonest form of the gene in natural populations. Using genetic mapping and site-specific recombination, we identified a third genotype with considerably greater resistance that is currently rare in the wild. In these flies there have been two duplications, resulting in three copies of both the truncated allele of CHKov1 and CHKov2 (one of which is also truncated). Remarkably, the truncated allele of CHKov1 has previously been found to confer resistance to organophosphate insecticides. As estimates of the age of this allele predate the use of insecticides, it is likely that this allele initially functioned as a defence against viruses and fortuitously "pre-adapted" flies to insecticides. These results demonstrate that strong selection by parasites for increased host resistance can result in major genetic changes and rapid shifts in allele frequencies; and, contrary to the prevailing view that resistance to pathogens can be a costly trait to evolve, the pleiotropic effects of these changes can have unexpected benefits.
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Affiliation(s)
- Michael M Magwire
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom.
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32
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Symonds VV, Hatlestad G, Lloyd AM. Natural allelic variation defines a role for ATMYC1: trichome cell fate determination. PLoS Genet 2011; 7:e1002069. [PMID: 21695236 PMCID: PMC3111535 DOI: 10.1371/journal.pgen.1002069] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Accepted: 03/24/2011] [Indexed: 11/19/2022] Open
Abstract
The molecular nature of biological variation is not well understood. Indeed, many questions persist regarding the types of molecular changes and the classes of genes that underlie morphological variation within and among species. Here we have taken a candidate gene approach based on previous mapping results to identify the gene and ultimately a polymorphism that underlies a trichome density QTL in Arabidopsis thaliana. Our results show that natural allelic variation in the transcription factor ATMYC1 alters trichome density in A. thaliana; this is the first reported function for ATMYC1. Using site-directed mutagenesis and yeast two-hybrid experiments, we demonstrate that a single amino acid replacement in ATMYC1, discovered in four ecotypes, eliminates known protein–protein interactions in the trichome initiation pathway. Additionally, in a broad screen for molecular variation at ATMYC1, including 72 A. thaliana ecotypes, a high-frequency block of variation was detected that results in >10% amino acid replacement within one of the eight exons of the gene. This sequence variation harbors a strong signal of divergent selection but has no measurable effect on trichome density. Homologs of ATMYC1 are pleiotropic, however, so this block of variation may be the result of natural selection having acted on another trait, while maintaining the trichome density role of the gene. These results show that ATMYC1 is an important source of variation for epidermal traits in A. thaliana and indicate that the transcription factors that make up the TTG1 genetic pathway generally may be important sources of epidermal variation in plants. Among the goals of modern evolutionary biology is to identify the molecular genetic sources of natural variation. Although genetic mapping has led to an increased understanding of the genetic architecture of natural variation, there are surprisingly few cases where the molecular source of the variation has been identified. Here, we utilize previous mapping results to identify the gene and ultimately a polymorphism that underlies natural variation for a dynamic trait in Arabidopsis thaliana: trichome density. We show that plants carrying a knock-out of the bHLH transcription factor ATMYC1 have a reduced trichome density phenotype; this is the first reported function for ATMYC1. Using traditional and molecular genetic approaches, we identify a single base change in natural alleles of ATMYC1, which leads to an amino acid replacement that qualitatively alters protein–protein interactions with known partners, presumably altering the trichome cell fate pathway. In a broad screen for molecular variation in ATMYC1, we identify a dense block of amino acid replacements that differentiates two high-frequency allele types. Although this block of variation does not appear to affect trichome density, based on paralogs of ATMYC1, we propose that this variation has arisen due to directional selection on another epidermal trait.
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Affiliation(s)
- V Vaughan Symonds
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas, United States of America.
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33
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Wayne ML, Blohm GM, Brooks ME, Regan KL, Brown BY, Barfield M, Holt RD, Bolker BM. The prevalence and persistence of sigma virus, a biparentally transmitted parasite of Drosophila melanogaster. EVOLUTIONARY ECOLOGY RESEARCH 2011; 13:323-345. [PMID: 28217032 PMCID: PMC5313041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
QUESTION How do vertically transmitted parasites persist? ORGANISMS Drosophila melanogaster (host) and sigma virus (parasite). FIELD SITE Peach stands in northern Georgia, USA, on a transect between Macon and Athens. EMPIRICAL METHODS We estimated prevalence in the field. We also estimated male and female transmission in the laboratory, using field-collected animals as parents. We further quantified patrilineal (father to son) transmission in the laboratory, and estimated cost of infection (virulence) by quantifying decreased egg production of infected flies. MATHEMATICAL METHODS Discrete-time, deterministic models for prevalence; analysis of stability of disease-free and endemic equilibria; numerical computation of equilibria based on empirical estimates. KEY ASSUMPTIONS Random mating, discrete generations, cost of infection to females only. PREDICTIONS AND CONCLUSIONS The model allows persistence under parameter estimates obtained for this population. Uncertainty in parameters leads to wide confidence intervals on the predicted prevalence, which may be systematically underestimated due to Jensen's inequality. Male transmission is required for persistence, and multiple generations of strictly patrilineal transmission are possible in the laboratory, albeit with decreasing transmission efficiency.
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Affiliation(s)
- Marta L Wayne
- Department of Biology, University of Florida, Gainesville, Florida, USA ; Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA ; UF Genetics Institute, University of Florida, Gainesville, Florida, USA
| | - Gabriela M Blohm
- Department of Biology, University of Florida, Gainesville, Florida, USA
| | - Mollie E Brooks
- Department of Biology, University of Florida, Gainesville, Florida, USA
| | - Kerry L Regan
- Department of Biology, University of Florida, Gainesville, Florida, USA ; Department of Biological Sciences, University of Notre Dame, South Bend, Indiana, USA
| | - Brennin Y Brown
- Department of Biology, University of Florida, Gainesville, Florida, USA
| | - Michael Barfield
- Department of Biology, University of Florida, Gainesville, Florida, USA
| | - Robert D Holt
- Department of Biology, University of Florida, Gainesville, Florida, USA ; Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA
| | - Benjamin M Bolker
- Department of Biology, University of Florida, Gainesville, Florida, USA ; Department of Mathematics, McMaster University, Hamilton, Ontario, Canada
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34
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Antonovics J, Thrall PH, Burdon JJ, Laine AL. Partial resistance in the Linum-Melampsora host-pathogen system: does partial resistance make the red queen run slower? Evolution 2010; 65:512-22. [PMID: 21029078 DOI: 10.1111/j.1558-5646.2010.01146.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Five levels of disease expression were scored in a cross-inoculation study of 120 host and 60 pathogen lines of wild flax Linum marginale and its rust fungus Melampsora lini sampled from six natural populations. Patterns of partial resistance showed clear evidence of gene-for-gene interactions, with particular levels of partial resistance occurring in specific host-pathogen combinations. Sympatric and putatively more highly coevolved host-pathogen combinations had a lower frequency of partial resistance types relative to allopatric combinations. Sympatric host-pathogen combinations also showed a lower diversity of resistance responses, but there was a trend toward a greater fraction of this variance being determined by pathogen-genotype × host-genotype interactions. In this system, there was no evidence that partial resistances slow host-pathogen coevolution. The analyses show that if variation is generated by among population host or pathogen dispersal, then coevolution occurs largely by pathogens overcoming the partial resistances that are generated.
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Affiliation(s)
- Janis Antonovics
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904, USA.
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35
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Wilfert L, Jiggins FM. Host-parasite coevolution: genetic variation in a virus population and the interaction with a host gene. J Evol Biol 2010; 23:1447-55. [PMID: 20456575 DOI: 10.1111/j.1420-9101.2010.02002.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Host-parasite coevolution is considered to be an important factor in maintaining genetic variation in resistance to pathogens. Drosophila melanogaster is naturally infected by the sigma virus, a vertically transmitted and host-specific pathogen. In fly populations, there is a large amount of genetic variation in the transmission rate from parent to offspring, much of which is caused by major-effect resistance polymorphisms. We have found that there are similarly high levels of genetic variation in the rate of paternal transmission among 95 different isolates of the virus as in the host. However, when we examined a transmission-blocking gene in the host, we found that it was effective across virus isolates. Therefore, the high levels of genetic variation observed in this system do not appear to be maintained because of coevolution resulting from interactions between this host gene and parasite genes.
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Affiliation(s)
- L Wilfert
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK.
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36
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Abstract
Association and linkage mapping have become important tools in understanding the genetics of complex traits, including diseases in humans. As the success of association mapping is reduced by small effect sizes and limited power, linkage studies in laboratory-based model systems are still heavily used. But whether the results of these studies can be replicated in natural populations has been questioned. Here, we show that a polymorphism in the gene ref(2)P, which had previously been linked to sigma virus resistance in Drosophila melanogaster under laboratory conditions, also provides resistance against the virus in female flies in a wild population in the field. This genetic association is thus upheld in spite of a known genotype-by-genotype interaction and environmental variation.
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Affiliation(s)
- Lena Wilfert
- Department of Genetics, University of Cambridge, Cambridge CB2 3EH, UK.
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37
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Tellier A, Brown J. The Influence of Perenniality and Seed Banks on Polymorphism in Plant‐Parasite Interactions. Am Nat 2009; 174:769-79. [DOI: 10.1086/646603] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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38
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Schulenburg H, Kurtz J, Moret Y, Siva-Jothy MT. Introduction. Ecological immunology. Philos Trans R Soc Lond B Biol Sci 2009; 364:3-14. [PMID: 18926970 DOI: 10.1098/rstb.2008.0249] [Citation(s) in RCA: 187] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
An organism's fitness is critically reliant on its immune system to provide protection against parasites and pathogens. The structure of even simple immune systems is surprisingly complex and clearly will have been moulded by the organism's ecology. The aim of this review and the theme issue is to examine the role of different ecological factors on the evolution of immunity. Here, we will provide a general framework of the field by contextualizing the main ecological factors, including interactions with parasites, other types of biotic as well as abiotic interactions, intraspecific selective constraints (life-history trade-offs, sexual selection) and population genetic processes. We then elaborate the resulting immunological consequences such as the diversity of defence mechanisms (e.g. avoidance behaviour, resistance, tolerance), redundancy and protection against immunopathology, life-history integration of the immune response and shared immunity within a community (e.g. social immunity and microbiota-mediated protection). Our review summarizes the concepts of current importance and directs the reader to promising future research avenues that will deepen our understanding of the defence against parasites and pathogens.
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Affiliation(s)
- Hinrich Schulenburg
- Zoological Institute, University of Kiel, Am Botanischen Garten, 24098 Kiel, Germany.
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39
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Abstract
The fruit fly Drosophila melanogaster is a powerful model to study host-pathogen interactions. Most studies so far have focused on extracellular pathogens such as bacteria and fungi. More recently, viruses have come to the front, and RNA interference was shown to play a critical role in the control of viral infections in drosophila. We review here our current knowledge on drosophila viruses. A diverse set of RNA viruses belonging to several families (Rhabdoviridae, Dicistroviridae, Birnaviridae, Reoviridae, Errantiviridae) has been reported in D. melanogaster. By contrast, no DNA virus has been recovered up to now. The drosophila viruses represent powerful tools to study virus-cell interactions in vivo. Analysis of the literature however reveals that for many of them, important gaps exist in our understanding of their replication cycle, genome organization, morphology or pathogenesis. The data obtained in the past few years on antiviral defense mechanisms in drosophila, which point to evolutionary conserved pathways, highlight the potential of the D. melanogaster model to study antiviral innate immunity and to better understand the complex interaction between arthropod-borne viruses and their insect vectors.
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40
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Bangham J, Knott SA, Kim KW, Young RS, Jiggins FM. Genetic variation affecting host-parasite interactions: major-effect quantitative trait loci affect the transmission of sigma virus in Drosophila melanogaster. Mol Ecol 2008; 17:3800-7. [PMID: 18665899 DOI: 10.1111/j.1365-294x.2008.03873.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In natural populations, genetic variation affects resistance to disease. Whether that genetic variation comprises lots of small-effect polymorphisms or a small number of large-effect polymorphisms has implications for adaptation, selection and how genetic variation is maintained in populations. Furthermore, how much genetic variation there is, and the genes that underlie this variation, affects models of co-evolution between parasites and their hosts. We are studying the genetic variation that affects the resistance of Drosophila melanogaster to its natural pathogen--the vertically transmitted sigma virus. We have carried out three separate quantitative trait locus mapping analyses to map gene variants on the second chromosome that cause variation in the rate at which males transmit the infection to their offspring. All three crosses identified a locus in a similar chromosomal location that causes a large drop in the rate at which the virus is transmitted. We also found evidence for an additional smaller-effect quantitative trait locus elsewhere on the chromosome. Our data, together with previous experiments on the sigma virus and parasitoid wasps, indicate that the resistance of D. melanogaster to co-evolved pathogens is controlled by a limited number of major-effect polymorphisms.
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Affiliation(s)
- Jenny Bangham
- School of Biological Sciences, Institute of Evolutionary Biology, The University of Edinburgh, Ashworth Laboratories, The King's Buildings, West Mains Road, Edinburgh, UK.
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Genetic variation affecting host-parasite interactions: different genes affect different aspects of sigma virus replication and transmission in Drosophila melanogaster. Genetics 2008; 178:2191-9. [PMID: 18430944 DOI: 10.1534/genetics.107.085449] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In natural populations, genetic variation affects resistance to disease. Knowing how much variation exists, and understanding the genetic architecture of this variation, is important for medicine, for agriculture, and for understanding evolutionary processes. To investigate the extent and nature of genetic variation affecting resistance to pathogens, we are studying a tractable model system: Drosophila melanogaster and its natural pathogen the vertically transmitted sigma virus. We show that considerable genetic variation affects transmission of the virus from parent to offspring. However, maternal and paternal transmission of the virus is affected by different genes. Maternal transmission is a simple Mendelian trait: most of the genetic variation is explained by a polymorphism in ref(2)P, a gene already well known to affect resistance to sigma. In contrast, there is considerable genetic variation in paternal transmission that cannot be explained by ref(2)P and is caused by other loci on chromosome 2. Furthermore, we found no genetic correlation between paternal transmission of the virus and resistance to infection by the sigma virus following injection. This suggests that different loci affect viral replication and paternal transmission.
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