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Cornetti L, Fields PD, Du Pasquier L, Ebert D. Long-term balancing selection for pathogen resistance maintains trans-species polymorphisms in a planktonic crustacean. Nat Commun 2024; 15:5333. [PMID: 38909039 PMCID: PMC11193740 DOI: 10.1038/s41467-024-49726-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 06/18/2024] [Indexed: 06/24/2024] Open
Abstract
Balancing selection is an evolutionary process that maintains genetic polymorphisms at selected loci and strongly reduces the likelihood of allele fixation. When allelic polymorphisms that predate speciation events are maintained independently in the resulting lineages, a pattern of trans-species polymorphisms may occur. Trans-species polymorphisms have been identified for loci related to mating systems and the MHC, but they are generally rare. Trans-species polymorphisms in disease loci are believed to be a consequence of long-term host-parasite coevolution by balancing selection, the so-called Red Queen dynamics. Here we scan the genomes of three crustaceans with a divergence of over 15 million years and identify 11 genes containing identical-by-descent trans-species polymorphisms with the same polymorphisms in all three species. Four of these genes display molecular footprints of balancing selection and have a function related to immunity. Three of them are located in or close to loci involved in resistance to a virulent bacterial pathogen, Pasteuria, with which the Daphnia host is known to coevolve. This provides rare evidence of trans-species polymorphisms for loci known to be functionally relevant in interactions with a widespread and highly specific parasite. These findings support the theory that specific antagonistic coevolution is able to maintain genetic diversity over millions of years.
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Affiliation(s)
- Luca Cornetti
- Department of Environmental Sciences, Zoology, University of Basel, Basel, Switzerland
- Syngenta Crop Protection AG, Stein, Switzerland
| | - Peter D Fields
- Department of Environmental Sciences, Zoology, University of Basel, Basel, Switzerland
| | - Louis Du Pasquier
- Department of Environmental Sciences, Zoology, University of Basel, Basel, Switzerland
| | - Dieter Ebert
- Department of Environmental Sciences, Zoology, University of Basel, Basel, Switzerland.
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2
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Shaw CL, Bilich R, Duffy MA. A common multi-host parasite shows genetic structuring at the host species and population levels. Parasitology 2024:1-10. [PMID: 38616414 DOI: 10.1017/s0031182024000428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
Although individual parasite species commonly infect many populations across physical space as well as multiple host species, the extent to which parasites traverse physical and phylogenetic distances is unclear. Population genetic analyses of parasite populations can reveal how parasites move across space or between host species, including helping assess whether a parasite is more likely to infect a different host species in the same location or the same host species in a different location. Identifying these transmission barriers could be exploited for effective disease control. Here, we analysed population genetic structuring of the parasite Pasteuria ramosa in daphniid host species from different lakes. Outbreaks occurred most often in the common host species Daphnia dentifera and Daphnia retrocurva. The genetic distance between parasite samples tended to be smaller when samples were collected from the same lake, the same host species and closer in time. Within lakes, the parasite showed structure by host species and sampling date; within a host species, the parasite showed structure by lake and sampling date. However, despite this structuring, we found the same parasite genotype infecting closely related host species, and we sometimes found the same genotype in nearby lakes. Thus, P. ramosa experiences challenges infecting different host species and moving between populations, but doing so is possible. In addition, the structuring by sampling date indicates potential adaptation to or coevolution with host populations and supports prior findings that parasite population structure is dynamic during outbreaks.
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Affiliation(s)
- Clara L Shaw
- Department of Ecology & Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
- Department of Biology, University of Minnesota Duluth, Duluth, MN, USA
| | - Rebecca Bilich
- Department of Ecology & Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
| | - Meghan A Duffy
- Department of Ecology & Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
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Huessy B, Bumann D, Ebert D. Ectopical expression of bacterial collagen-like protein supports its role as adhesin in host-parasite coevolution. ROYAL SOCIETY OPEN SCIENCE 2024; 11:231441. [PMID: 38577215 PMCID: PMC10987987 DOI: 10.1098/rsos.231441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2023] [Revised: 01/10/2024] [Accepted: 02/13/2024] [Indexed: 04/06/2024]
Abstract
For a profound understanding of antagonistic coevolution, it is necessary to identify the coevolving genes. The bacterium Pasteuria and its host, the microcrustacean Daphnia, are a well-characterized paradigm for co-evolution, but the underlying genes remain largely unknown. A genome-wide association study suggested a Pasteuria collagen-like protein 7 (Pcl7) as a candidate mediating parasite attachment and driving its coevolution with the host. Since Pasteuria ramosa cannot currently be genetically manipulated, we used Bacillus thuringiensis to express a fusion protein of a Pcl7 carboxy-terminus from P. ramosa and the amino-terminal domain of a B. thuringiensis collagen-like protein (CLP). Mutant B. thuringiensis (Pcl7-Bt) spores but not wild-type B. thuringiensis (WT-Bt) spores attached to the same site of susceptible hosts as P. ramosa. Furthermore, Pcl7-Bt spores attached readily to susceptible host genotypes, but only slightly to resistant host genotypes. These findings indicated that the fusion protein was properly expressed and folded and demonstrated that indeed the C-terminus of Pcl7 mediates attachment in a host genotype-specific manner. These results provide strong evidence for the involvement of a CLP in the coevolution of Daphnia and P. ramosa and open new avenues for genetic epidemiological studies of host-parasite interactions.
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Affiliation(s)
- Benjamin Huessy
- Department of Environmental Sciences, Zoology, University of Basel, Basel4051, Switzerland
- University of Basel, Basel4056, Switzerland
| | | | - Dieter Ebert
- Department of Environmental Sciences, Zoology, University of Basel, Basel4051, Switzerland
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Sromek L, Ylinen E, Kunnasranta M, Maduna SN, Sinisalo T, Michell CT, Kovacs KM, Lydersen C, Ieshko E, Andrievskaya E, Alexeev V, Leidenberger S, Hagen SB, Nyman T. Loss of species and genetic diversity during colonization: Insights from acanthocephalan parasites in northern European seals. Ecol Evol 2023; 13:e10608. [PMID: 37869427 PMCID: PMC10585441 DOI: 10.1002/ece3.10608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 09/22/2023] [Accepted: 09/25/2023] [Indexed: 10/24/2023] Open
Abstract
Studies on host-parasite systems that have experienced distributional shifts, range fragmentation, and population declines in the past can provide information regarding how parasite community richness and genetic diversity will change as a result of anthropogenic environmental changes in the future. Here, we studied how sequential postglacial colonization, shifts in habitat, and reduced host population sizes have influenced species richness and genetic diversity of Corynosoma (Acanthocephala: Polymorphidae) parasites in northern European marine, brackish, and freshwater seal populations. We collected Corynosoma population samples from Arctic, Baltic, Ladoga, and Saimaa ringed seal subspecies and Baltic gray seals, and then applied COI barcoding and triple-enzyme restriction-site associated DNA (3RAD) sequencing to delimit species, clarify their distributions and community structures, and elucidate patterns of intraspecific gene flow and genetic diversity. Our results showed that Corynosoma species diversity reflected host colonization histories and population sizes, with four species being present in the Arctic, three in the Baltic Sea, two in Lake Ladoga, and only one in Lake Saimaa. We found statistically significant population-genetic differentiation within all three Corynosoma species that occur in more than one seal (sub)species. Genetic diversity tended to be high in Corynosoma populations originating from Arctic ringed seals and low in the landlocked populations. Our results indicate that acanthocephalan communities in landlocked seal populations are impoverished with respect to both species and intraspecific genetic diversity. Interestingly, the loss of genetic diversity within Corynosoma species seems to have been less drastic than in their seal hosts, possibly due to their large local effective population sizes resulting from high infection intensities and effective intra-host population mixing. Our study highlights the utility of genomic methods in investigations of community composition and genetic diversity of understudied parasites.
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Affiliation(s)
- Ludmila Sromek
- Department of Marine Ecosystems Functioning, Institute of OceanographyUniversity of GdanskGdyniaPoland
| | - Eeva Ylinen
- Department of Environmental and Biological SciencesUniversity of Eastern FinlandJoensuuFinland
| | - Mervi Kunnasranta
- Department of Environmental and Biological SciencesUniversity of Eastern FinlandJoensuuFinland
- Natural Resources Institute FinlandJoensuuFinland
| | - Simo N. Maduna
- Department of Ecosystem in the Barents RegionNorwegian Institute of Bioeconomy ResearchSvanvikNorway
| | - Tuula Sinisalo
- Department of Biological and Environmental SciencesUniversity of JyväskyläJyväskyläFinland
| | - Craig T. Michell
- Department of Environmental and Biological SciencesUniversity of Eastern FinlandJoensuuFinland
- Red Sea Research CenterKing Abdullah University of Science and TechnologyJeddahSaudi Arabia
| | | | | | - Evgeny Ieshko
- Institute of Biology, Karelian Research CentreRussian Academy of SciencesPetrozavodskRussia
| | | | | | - Sonja Leidenberger
- Department of Biology and Bioinformatics, School of BioscienceUniversity of SkövdeSkövdeSweden
| | - Snorre B. Hagen
- Department of Ecosystem in the Barents RegionNorwegian Institute of Bioeconomy ResearchSvanvikNorway
| | - Tommi Nyman
- Department of Ecosystem in the Barents RegionNorwegian Institute of Bioeconomy ResearchSvanvikNorway
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Fredericksen M, Fields PD, Du Pasquier L, Ricci V, Ebert D. QTL study reveals candidate genes underlying host resistance in a Red Queen model system. PLoS Genet 2023; 19:e1010570. [PMID: 36730161 PMCID: PMC9894429 DOI: 10.1371/journal.pgen.1010570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 12/14/2022] [Indexed: 02/03/2023] Open
Abstract
Specific interactions of host and parasite genotypes can lead to balancing selection, maintaining genetic diversity within populations. In order to understand the drivers of such specific coevolution, it is necessary to identify the molecular underpinnings of these genotypic interactions. Here, we investigate the genetic basis of resistance in the crustacean host, Daphnia magna, to attachment and subsequent infection by the bacterial parasite, Pasteuria ramosa. We discover a single locus with Mendelian segregation (3:1 ratio) with resistance being dominant, which we call the F locus. We use QTL analysis and fine mapping to localize the F locus to a 28.8-kb region in the host genome, adjacent to a known resistance supergene. We compare the 28.8-kb region in the two QTL parents to identify differences between host genotypes that are resistant versus susceptible to attachment and infection by the parasite. We identify 13 genes in the region, from which we highlight eight biological candidates for the F locus, based on presence/absence polymorphisms and differential gene expression. The top candidates include a fucosyltransferase gene that is only present in one of the two QTL parents, as well as several Cladoceran-specific genes belonging to a large family that is represented in multiple locations of the host genome. Fucosyltransferases have been linked to resistance in previous studies of Daphnia-Pasteuria and other host-parasite systems, suggesting that P. ramosa spore attachment could be mediated by changes in glycan structures on D. magna cuticle proteins. The Cladoceran-specific candidate genes suggest a resistance strategy that relies on gene duplication. Our results add a new locus to a growing genetic model of resistance in the D. magna-P. ramosa system. The identified candidate genes will be used in future functional genetic studies, with the ultimate aim to test for cycles of allele frequencies in natural populations.
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Affiliation(s)
- Maridel Fredericksen
- University of Basel, Department of Environmental Sciences, Zoology, Basel, Switzerland
- * E-mail:
| | - Peter D. Fields
- University of Basel, Department of Environmental Sciences, Zoology, Basel, Switzerland
| | - Louis Du Pasquier
- University of Basel, Department of Environmental Sciences, Zoology, Basel, Switzerland
| | - Virginie Ricci
- University of Basel, Department of Environmental Sciences, Zoology, Basel, Switzerland
| | - Dieter Ebert
- University of Basel, Department of Environmental Sciences, Zoology, Basel, Switzerland
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Ameline C, Voegtli F, Andras J, Dexter E, Engelstädter J, Ebert D. Genetic slippage after sex maintains diversity for parasite resistance in a natural host population. SCIENCE ADVANCES 2022; 8:eabn0051. [PMID: 36399570 PMCID: PMC9674289 DOI: 10.1126/sciadv.abn0051] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 10/04/2022] [Indexed: 06/16/2023]
Abstract
Although parasite-mediated selection is a major driver of host evolution, its influence on genetic variation for parasite resistance is not yet well understood. We monitored resistance in a large population of the planktonic crustacean Daphnia magna over 8 years, as it underwent yearly epidemics of the bacterial pathogen Pasteuria ramosa. We observed cyclic dynamics of resistance: Resistance increased throughout the epidemics, but susceptibility was restored each spring when hosts hatched from sexual resting stages. Host resting stages collected across the year showed that largely resistant host populations can produce susceptible sexual offspring. A genetic model of resistance developed for this host-parasite system, based on multiple loci and strong epistasis, is in partial agreement with our findings. Our results reveal that, despite strong selection for resistance in a natural host population, genetic slippage after sexual reproduction can be a strong factor for the maintenance of genetic diversity of host resistance.
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Affiliation(s)
- Camille Ameline
- Department of Environmental Sciences, Zoology, University of Basel, Vesalgasse 1, 4051 Basel, Switzerland
| | - Felix Voegtli
- Department of Environmental Sciences, Zoology, University of Basel, Vesalgasse 1, 4051 Basel, Switzerland
| | - Jason Andras
- Department of Environmental Sciences, Zoology, University of Basel, Vesalgasse 1, 4051 Basel, Switzerland
| | - Eric Dexter
- Department of Environmental Sciences, Zoology, University of Basel, Vesalgasse 1, 4051 Basel, Switzerland
| | - Jan Engelstädter
- School of Biological Sciences, The University of Queensland, Brisbane, Australia
| | - Dieter Ebert
- Department of Environmental Sciences, Zoology, University of Basel, Vesalgasse 1, 4051 Basel, Switzerland
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Ebert D. Daphnia as a versatile model system in ecology and evolution. EvoDevo 2022; 13:16. [PMID: 35941607 PMCID: PMC9360664 DOI: 10.1186/s13227-022-00199-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Accepted: 06/20/2022] [Indexed: 11/10/2022] Open
Abstract
Water fleas of the genus Daphnia have been a model system for hundreds of years and is among the best studied ecological model organisms to date. Daphnia are planktonic crustaceans with a cyclic parthenogenetic life-cycle. They have a nearly worldwide distribution, inhabiting standing fresh- and brackish water bodies, from small temporary pools to large lakes. Their predominantly asexual reproduction allows for the study of phenotypes excluding genetic variation, enabling us to separate genetic from non-genetic effects. Daphnia are often used in studies related to ecotoxicology, predator-induced defence, host–parasite interactions, phenotypic plasticity and, increasingly, in evolutionary genomics. The most commonly studied species are Daphnia magna and D. pulex, for which a rapidly increasing number of genetic and genomic tools are available. Here, I review current research topics, where the Daphnia model system plays a critical role.
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Affiliation(s)
- Dieter Ebert
- Department of Environmental Sciences, Zoology, University of Basel, Vesalgasse 1, CH-4051, Basel, Switzerland.
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8
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Virrueta Herrera S, Johnson KP, Sweet AD, Ylinen E, Kunnasranta M, Nyman T. High levels of inbreeding with spatial and host-associated structure in lice of an endangered freshwater seal. Mol Ecol 2022; 31:4593-4606. [PMID: 35726520 PMCID: PMC9544963 DOI: 10.1111/mec.16569] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Revised: 05/12/2022] [Accepted: 05/20/2022] [Indexed: 02/02/2023]
Abstract
Host-specialist parasites of endangered large vertebrates are in many cases more endangered than their hosts. In particular, low host population densities and reduced among-host transmission rates are expected to lead to inbreeding within parasite infrapopulations living on single host individuals. Furthermore, spatial population structures of directly-transmitted parasites should be concordant with those of their hosts. Using population genomic approaches, we investigated inbreeding and population structure in a host-specialist seal louse (Echinophthirius horridus) infesting the Saimaa ringed seal (Phoca hispida saimensis), which is endemic to Lake Saimaa in Finland, and is one of the most endangered pinnipeds in the world. We conducted genome resequencing of pairs of lice collected from 18 individual Saimaa ringed seals throughout the Lake Saimaa complex. Our analyses showed high genetic similarity and inbreeding between lice inhabiting the same individual seal host, indicating low among-host transmission rates. Across the lake, genetic differentiation among individual lice was correlated with their geographic distance, and assignment analyses revealed a marked break in the genetic variation of the lice in the middle of the lake, indicating substantial population structure. These findings indicate that movements of Saimaa ringed seals across the main breeding areas of the fragmented Lake Saimaa complex may in fact be more restricted than suggested by previous population-genetic analyses of the seals themselves.
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Affiliation(s)
- Stephany Virrueta Herrera
- Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, Illinois, USA.,Program in Ecology, Evolution, and Conservation, University of Illinois, Urbana, Illinois, USA
| | - Kevin P Johnson
- Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, Illinois, USA
| | - Andrew D Sweet
- Department of Biological Sciences, Arkansas State University, Jonesboro, Arkansas, USA
| | - Eeva Ylinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| | - Mervi Kunnasranta
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland.,Natural Resources Institute Finland, Joensuu, Finland
| | - Tommi Nyman
- Department of Ecosystems in the Barents Region, Svanhovd Research Station, Norwegian Institute of Bioeconomy Research, Svanvik, Norway
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