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Parée T, Noble L, Ferreira Gonçalves J, Teotónio H. rec-1 loss of function increases recombination in the central gene clusters at the expense of autosomal pairing centers. Genetics 2024; 226:iyad205. [PMID: 38001364 DOI: 10.1093/genetics/iyad205] [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: 10/03/2023] [Revised: 10/03/2023] [Accepted: 11/08/2023] [Indexed: 11/26/2023] Open
Abstract
Meiotic control of crossover (CO) number and position is critical for homologous chromosome segregation and organismal fertility, recombination of parental genotypes, and the generation of novel genetic combinations. We here characterize the recombination rate landscape of a rec-1 loss of function modifier of CO position in Caenorhabditis elegans, one of the first ever modifiers discovered. By averaging CO position across hermaphrodite and male meioses and by genotyping 203 single-nucleotide variants covering about 95% of the genome, we find that the characteristic chromosomal arm-center recombination rate domain structure is lost in the loss of function rec-1 mutant. The rec-1 loss of function mutant smooths the recombination rate landscape but is insufficient to eliminate the nonuniform position of CO. Lower recombination rates in the rec-1 mutant are particularly found in the autosomal arm domains containing the pairing centers. We further find that the rec-1 mutant is of little consequence for organismal fertility and egg viability and thus for rates of autosomal nondisjunction. It nonetheless increases X chromosome nondisjunction rates and thus male appearance. Our findings question the maintenance of recombination rate heritability and genetic diversity among C. elegans natural populations, and they further suggest that manipulating genetic modifiers of CO position will help find quantitative trait loci located in low-recombining genomic regions normally refractory to discovery.
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Affiliation(s)
- Tom Parée
- Institut de Biologie de l'École Normale Supérieure, CNRS UMR, 8197, Inserm U1024, PSL Research University, Paris F-75005, France
| | - Luke Noble
- Institut de Biologie de l'École Normale Supérieure, CNRS UMR, 8197, Inserm U1024, PSL Research University, Paris F-75005, France
- EnviroDNA, 95 Albert St., Brunswick, Victoria 3065, Australia
| | - João Ferreira Gonçalves
- Institut de Biologie de l'École Normale Supérieure, CNRS UMR, 8197, Inserm U1024, PSL Research University, Paris F-75005, France
| | - Henrique Teotónio
- Institut de Biologie de l'École Normale Supérieure, CNRS UMR, 8197, Inserm U1024, PSL Research University, Paris F-75005, France
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Sepulveda NB, Chen D, Petrella LN. Moderate heat stress-induced sterility is due to motility defects and reduced mating drive in Caenorhabditis elegans males. J Exp Biol 2023; 226:jeb245546. [PMID: 37724024 DOI: 10.1242/jeb.245546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Accepted: 09/11/2023] [Indexed: 09/20/2023]
Abstract
Moderate heat stress negatively impacts fertility in sexually reproducing organisms at sublethal temperatures. These moderate heat stress effects are typically more pronounced in males. In some species, sperm production, quality and motility are the primary cause of male infertility during moderate heat stress. However, this is not the case in the model nematode Caenorhabditis elegans, where changes in mating behavior are the primary cause of fertility loss. We report that heat-stressed C. elegans males are more motivated to locate and remain on food and less motivated to leave food to find and mate with hermaphrodites than their unstressed counterparts. Heat-stressed males also demonstrate a reduction in motility that likely limits their ability to mate. Collectively these changes result in a dramatic reduction in reproductive success. The reduction in mate-searching behavior may be partially due to increased expression of the chemoreceptor odr-10 in the AWA sensory neurons, which is a marker for starvation in males. These results demonstrate that moderate heat stress may have profound and previously underappreciated effects on reproductive behaviors. As climate change continues to raise global temperatures, it will be imperative to understand how moderate heat stress affects behavioral and motility elements critical to reproduction.
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Affiliation(s)
- Nicholas B Sepulveda
- Department of Biological Sciences, Marquette University, 1428 W Clybourn St., Milwaukee, WI 53217, USA
| | - Donald Chen
- Department of Biological Sciences, Marquette University, 1428 W Clybourn St., Milwaukee, WI 53217, USA
| | - Lisa N Petrella
- Department of Biological Sciences, Marquette University, 1428 W Clybourn St., Milwaukee, WI 53217, USA
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3
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Harbin JP, Ellis RE. Efficient production of CRISPR/Cas9 gene knockouts in the male/female nematode Caenorhabditis nigoni. MICROPUBLICATION BIOLOGY 2023; 2023:10.17912/micropub.biology.000968. [PMID: 37746063 PMCID: PMC10512056 DOI: 10.17912/micropub.biology.000968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 08/14/2023] [Accepted: 09/05/2023] [Indexed: 09/26/2023]
Abstract
Although nematode genetics was founded on the use of hermaphrodite genetics for studying animal development and behavior, there is a growing need to extend this work to male/female species. One of the most promising species is C. nigoni, because it is so closely related to the model hermaphroditic C. briggsae. We present methods for using CRISPR/Cas9 gene editing to create mutations, and techniques for balancing, maintaining and studying these mutations.
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Affiliation(s)
- Jonathan P Harbin
- Molecular Biology, Rowan-Virtua SOM, Stratford, New Jersey, United States
| | - Ronald E Ellis
- Molecular Biology, Rowan-Virtua SOM, Stratford, New Jersey, United States
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4
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Mallard F, Noble L, Baer CF, Teotónio H. Variation in mutational (co)variances. G3 (BETHESDA, MD.) 2023; 13:jkac335. [PMID: 36548954 PMCID: PMC9911065 DOI: 10.1093/g3journal/jkac335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 06/10/2022] [Accepted: 12/06/2022] [Indexed: 12/24/2022]
Abstract
Because of pleiotropy, mutations affect the expression and inheritance of multiple traits and, together with selection, are expected to shape standing genetic covariances between traits and eventual phenotypic divergence between populations. It is therefore important to find if the M matrix, describing mutational variances of each trait and covariances between traits, varies between genotypes. We here estimate the M matrix for six locomotion behavior traits in lines of two genotypes of the nematode Caenorhabditis elegans that accumulated mutations in a nearly neutral manner for 250 generations. We find significant mutational variance along at least one phenotypic dimension of the M matrices, but neither their size nor their orientation had detectable differences between genotypes. The number of generations of mutation accumulation, or the number of MA lines measured, was likely insufficient to sample enough mutations and detect potentially small differences between the two M matrices. We then tested if the M matrices were similar to one G matrix describing the standing genetic (co)variances of a population derived by the hybridization of several genotypes, including the two measured for M, and domesticated to a lab-defined environment for 140 generations. We found that the M and G were different because the genetic covariances caused by mutational pleiotropy in the two genotypes are smaller than those caused by linkage disequilibrium in the lab population. We further show that M matrices differed in their alignment with the lab population G matrix. If generalized to other founder genotypes of the lab population, these observations indicate that selection does not shape the evolution of the M matrix for locomotion behavior in the short-term of a few tens to hundreds of generations and suggests that the hybridization of C. elegans genotypes allows selection on new phenotypic dimensions of locomotion behavior.
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Affiliation(s)
- François Mallard
- Institut de Biologie de l’École Normale Supérieure, PSL Research University, CNRS UMR 8197, Inserm U1024, F-75005 Paris, France
| | - Luke Noble
- Institut de Biologie de l’École Normale Supérieure, PSL Research University, CNRS UMR 8197, Inserm U1024, F-75005 Paris, France
| | - Charles F Baer
- Department of Biology, University of Florida Genetics Institute, University of Florida, Gainsville, FL 32611, USA
| | - Henrique Teotónio
- Institut de Biologie de l’École Normale Supérieure, PSL Research University, CNRS UMR 8197, Inserm U1024, F-75005 Paris, France
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5
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Noble LM, Rockman MV, Teotónio H. Gene-level quantitative trait mapping in Caenorhabditis elegans. G3-GENES GENOMES GENETICS 2021; 11:6114457. [PMID: 33693602 PMCID: PMC8022935 DOI: 10.1093/g3journal/jkaa061] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Accepted: 12/13/2020] [Indexed: 02/06/2023]
Abstract
The Caenorhabditis elegans multiparental experimental evolution (CeMEE) panel is a collection of genome-sequenced, cryopreserved recombinant inbred lines useful for mapping the evolution and genetic basis of quantitative traits. We have expanded the resource with new lines and new populations, and here report the genotype and haplotype composition of CeMEE version 2, including a large set of putative de novo mutations, and updated additive and epistatic mapping simulations. Additive quantitative trait loci explaining 4% of trait variance are detected with >80% power, and the median detection interval approaches single-gene resolution on the highly recombinant chromosome arms. Although CeMEE populations are derived from a long-term evolution experiment, genetic structure is dominated by variation present in the ancestral population.
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Affiliation(s)
- Luke M Noble
- Institut de Biologie, École Normale Supérieure, CNRS 8197, Inserm U1024, PSL Research University, F-75005 Paris, France.,Department of Biology, Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA
| | - Matthew V Rockman
- Department of Biology, Center for Genomics and Systems Biology, New York University, New York, NY 10003, USA
| | - Henrique Teotónio
- Institut de Biologie, École Normale Supérieure, CNRS 8197, Inserm U1024, PSL Research University, F-75005 Paris, France
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Webster AK, Hung A, Moore BT, Guzman R, Jordan JM, Kaplan REW, Hibshman JD, Tanny RE, Cook DE, Andersen E, Baugh LR. Population Selection and Sequencing of Caenorhabditis elegans Wild Isolates Identifies a Region on Chromosome III Affecting Starvation Resistance. G3 (BETHESDA, MD.) 2019; 9:3477-3488. [PMID: 31444297 PMCID: PMC6778785 DOI: 10.1534/g3.119.400617] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 08/21/2019] [Indexed: 12/18/2022]
Abstract
To understand the genetic basis of complex traits, it is important to be able to efficiently phenotype many genetically distinct individuals. In the nematode Caenorhabditis elegans, individuals have been isolated from diverse populations around the globe and whole-genome sequenced. As a result, hundreds of wild strains with known genome sequences can be used for genome-wide association studies (GWAS). However, phenotypic analysis of these strains can be laborious, particularly for quantitative traits requiring multiple measurements per strain. Starvation resistance is likely a fitness-proximal trait for nematodes, and it is related to metabolic disease risk in humans. However, natural variation in C. elegans starvation resistance has not been systematically characterized, and precise measurement of the trait is time-intensive. Here, we developed a population-selection-and-sequencing-based approach to phenotype starvation resistance in a pool of 96 wild strains. We used restriction site-associated DNA sequencing (RAD-seq) to infer the frequency of each strain among survivors in a mixed culture over time during starvation. We used manual starvation survival assays to validate the trait data, confirming that strains that increased in frequency over time are starvation-resistant relative to strains that decreased in frequency. Further, we found that variation in starvation resistance is significantly associated with variation at a region on chromosome III. Using a near-isogenic line (NIL), we showed the importance of this genomic interval for starvation resistance. This study demonstrates the feasibility of using population selection and sequencing in an animal model for phenotypic analysis of quantitative traits, documents natural variation of starvation resistance in C. elegans, and identifies a genomic region that contributes to such variation.
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Affiliation(s)
- Amy K Webster
- Department of Biology, Duke University, Durham, NC
- University Program in Genetics and Genomics, Duke University, Durham, NC, and
| | - Anthony Hung
- Department of Biology, Duke University, Durham, NC
| | - Brad T Moore
- Department of Biology, Duke University, Durham, NC
| | - Ryan Guzman
- Department of Biology, Duke University, Durham, NC
| | | | - Rebecca E W Kaplan
- Department of Biology, Duke University, Durham, NC
- University Program in Genetics and Genomics, Duke University, Durham, NC, and
| | - Jonathan D Hibshman
- Department of Biology, Duke University, Durham, NC
- University Program in Genetics and Genomics, Duke University, Durham, NC, and
| | - Robyn E Tanny
- Department of Molecular Biosciences, Northwestern University, Evanston, IL
| | - Daniel E Cook
- Department of Molecular Biosciences, Northwestern University, Evanston, IL
| | - Erik Andersen
- Department of Molecular Biosciences, Northwestern University, Evanston, IL
| | - L Ryan Baugh
- Department of Biology, Duke University, Durham, NC
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7
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Chelo IM, Afonso B, Carvalho S, Theologidis I, Goy C, Pino-Querido A, Proulx SR, Teotónio H. Partial Selfing Can Reduce Genetic Loads While Maintaining Diversity During Experimental Evolution. G3 (BETHESDA, MD.) 2019; 9:2811-2821. [PMID: 31278175 PMCID: PMC6723137 DOI: 10.1534/g3.119.400239] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 06/17/2019] [Indexed: 12/30/2022]
Abstract
Partial selfing, whereby self- and cross- fertilization occur in populations at intermediate frequencies, is generally thought to be evolutionarily unstable. Yet, it is found in natural populations. This could be explained if populations with partial selfing are able to reduce genetic loads and the possibility for inbreeding depression while keeping genetic diversity that may be important for future adaptation. To address this hypothesis, we compare the experimental evolution of Caenorhabditis elegans populations under partial selfing, exclusive selfing or predominant outcrossing, while they adapt to osmotically challenging conditions. We find that the ancestral genetic load, as measured by the risk of extinction upon inbreeding by selfing, is maintained as long as outcrossing is the main reproductive mode, but becomes reduced otherwise. Analysis of genome-wide single-nucleotide polymorphisms (SNPs) during experimental evolution and among the inbred lines that survived enforced inbreeding indicates that populations with predominant outcrossing or partial selfing maintained more genetic diversity than expected with neutrality or purifying selection. We discuss the conditions under which this could be explained by the presence of recessive deleterious alleles and/or overdominant loci. Taken together, our observations suggest that populations evolving under partial selfing can gain some of the benefits of eliminating unlinked deleterious recessive alleles and also the benefits of maintaining genetic diversity at partially dominant or overdominant loci that become associated due to variance of inbreeding levels.
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Affiliation(s)
- Ivo M Chelo
- Instituto Gulbenkian de Ciência, Apartado 14, P-2781-901 Oeiras, Portugal
- cE3c - Center for Ecology, Evolution and Environmental Changes, Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal
| | - Bruno Afonso
- Instituto Gulbenkian de Ciência, Apartado 14, P-2781-901 Oeiras, Portugal
- Institut de Biologie de l'École Normale Supérieure (IBENS), Inserm U1024, CNRS UMR 8197, F-75005 Paris, France
| | - Sara Carvalho
- Instituto Gulbenkian de Ciência, Apartado 14, P-2781-901 Oeiras, Portugal
| | - Ioannis Theologidis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, 73100 Heraklion, Greece
| | - Christine Goy
- Leibniz Research Institute for Environmental Medicine, 40225 Düsseldorf, Germany, and
| | - Ania Pino-Querido
- Instituto Gulbenkian de Ciência, Apartado 14, P-2781-901 Oeiras, Portugal
| | - Stephen R Proulx
- Department of Ecology, Evolution, and Marine Biology, University of California Santa Barbara, CA 93106
| | - Henrique Teotónio
- Institut de Biologie de l'École Normale Supérieure (IBENS), Inserm U1024, CNRS UMR 8197, F-75005 Paris, France
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8
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Sun S, Miao Z, Ratcliffe B, Campbell P, Pasch B, El-Kassaby YA, Balasundaram B, Chen C. SNP variable selection by generalized graph domination. PLoS One 2019; 14:e0203242. [PMID: 30677030 PMCID: PMC6345469 DOI: 10.1371/journal.pone.0203242] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 01/08/2019] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND High-throughput sequencing technology has revolutionized both medical and biological research by generating exceedingly large numbers of genetic variants. The resulting datasets share a number of common characteristics that might lead to poor generalization capacity. Concerns include noise accumulated due to the large number of predictors, sparse information regarding the p≫n problem, and overfitting and model mis-identification resulting from spurious collinearity. Additionally, complex correlation patterns are present among variables. As a consequence, reliable variable selection techniques play a pivotal role in predictive analysis, generalization capability, and robustness in clustering, as well as interpretability of the derived models. METHODS AND FINDINGS K-dominating set, a parameterized graph-theoretic generalization model, was used to model SNP (single nucleotide polymorphism) data as a similarity network and searched for representative SNP variables. In particular, each SNP was represented as a vertex in the graph, (dis)similarity measures such as correlation coefficients or pairwise linkage disequilibrium were estimated to describe the relationship between each pair of SNPs; a pair of vertices are adjacent, i.e. joined by an edge, if the pairwise similarity measure exceeds a user-specified threshold. A minimum k-dominating set in the SNP graph was then made as the smallest subset such that every SNP that is excluded from the subset has at least k neighbors in the selected ones. The strength of k-dominating set selection in identifying independent variables, and in culling representative variables that are highly correlated with others, was demonstrated by a simulated dataset. The advantages of k-dominating set variable selection were also illustrated in two applications: pedigree reconstruction using SNP profiles of 1,372 Douglas-fir trees, and species delineation for 226 grasshopper mouse samples. A C++ source code that implements SNP-SELECT and uses Gurobi optimization solver for the k-dominating set variable selection is available (https://github.com/transgenomicsosu/SNP-SELECT).
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Affiliation(s)
- Shuzhen Sun
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, United States of America
- Department of Forest and Conservation Sciences, Faculty of Forestry, The University of British Columbia, Vancouver, B.C. Canada
| | - Zhuqi Miao
- Center for Health Systems Innovation, Oklahoma State University, Stillwater, United States of America
| | - Blaise Ratcliffe
- Department of Forest and Conservation Sciences, Faculty of Forestry, The University of British Columbia, Vancouver, B.C. Canada
| | - Polly Campbell
- Department of Integrative Biology, Oklahoma State University, Stillwater, United States of America
- Department of Evolution, Ecology and Organismal Biology, University of California, Riverside, Riverside, United States of America
| | - Bret Pasch
- Department of Biological Sciences, Northern Arizona University, Flagstaff, United States of America
| | - Yousry A. El-Kassaby
- Department of Forest and Conservation Sciences, Faculty of Forestry, The University of British Columbia, Vancouver, B.C. Canada
| | - Balabhaskar Balasundaram
- School of Industrial Engineering and Management, Oklahoma State University, Stillwater, United States of America
| | - Charles Chen
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, United States of America
- * E-mail:
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9
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Noble LM, Chelo I, Guzella T, Afonso B, Riccardi DD, Ammerman P, Dayarian A, Carvalho S, Crist A, Pino-Querido A, Shraiman B, Rockman MV, Teotónio H. Polygenicity and Epistasis Underlie Fitness-Proximal Traits in the Caenorhabditis elegans Multiparental Experimental Evolution (CeMEE) Panel. Genetics 2017; 207:1663-1685. [PMID: 29066469 PMCID: PMC5714472 DOI: 10.1534/genetics.117.300406] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 10/10/2017] [Indexed: 01/27/2023] Open
Abstract
Understanding the genetic basis of complex traits remains a major challenge in biology. Polygenicity, phenotypic plasticity, and epistasis contribute to phenotypic variance in ways that are rarely clear. This uncertainty can be problematic for estimating heritability, for predicting individual phenotypes from genomic data, and for parameterizing models of phenotypic evolution. Here, we report an advanced recombinant inbred line (RIL) quantitative trait locus mapping panel for the hermaphroditic nematode Caenorhabditis elegans, the C. elegans multiparental experimental evolution (CeMEE) panel. The CeMEE panel, comprising 507 RILs at present, was created by hybridization of 16 wild isolates, experimental evolution for 140-190 generations, and inbreeding by selfing for 13-16 generations. The panel contains 22% of single-nucleotide polymorphisms known to segregate in natural populations, and complements existing C. elegans mapping resources by providing fine resolution and high nucleotide diversity across > 95% of the genome. We apply it to study the genetic basis of two fitness components, fertility and hermaphrodite body size at time of reproduction, with high broad-sense heritability in the CeMEE. While simulations show that we should detect common alleles with additive effects as small as 5%, at gene-level resolution, the genetic architectures of these traits do not feature such alleles. We instead find that a significant fraction of trait variance, approaching 40% for fertility, can be explained by sign epistasis with main effects below the detection limit. In congruence, phenotype prediction from genomic similarity, while generally poor ([Formula: see text]), requires modeling epistasis for optimal accuracy, with most variance attributed to the rapidly evolving chromosome arms.
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Affiliation(s)
- Luke M Noble
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York 10003
| | - Ivo Chelo
- Instituto Gulbenkian de Ciência, P-2781-901 Oeiras, Portugal
| | - Thiago Guzella
- Institut de Biologie, École Normale Supérieure, Centre National de la Recherche Scientifique (CNRS) UMR 8197, Institut National de la Santé et de la Recherche Médicale (INSERM) U1024, F-75005 Paris, France
| | - Bruno Afonso
- Instituto Gulbenkian de Ciência, P-2781-901 Oeiras, Portugal
- Institut de Biologie, École Normale Supérieure, Centre National de la Recherche Scientifique (CNRS) UMR 8197, Institut National de la Santé et de la Recherche Médicale (INSERM) U1024, F-75005 Paris, France
| | - David D Riccardi
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York 10003
| | - Patrick Ammerman
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York 10003
| | - Adel Dayarian
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106
| | - Sara Carvalho
- Instituto Gulbenkian de Ciência, P-2781-901 Oeiras, Portugal
| | - Anna Crist
- Institut de Biologie, École Normale Supérieure, Centre National de la Recherche Scientifique (CNRS) UMR 8197, Institut National de la Santé et de la Recherche Médicale (INSERM) U1024, F-75005 Paris, France
| | | | - Boris Shraiman
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106
- Department of Physics, University of California, Santa Barbara, California 93106
| | - Matthew V Rockman
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York 10003
| | - Henrique Teotónio
- Institut de Biologie, École Normale Supérieure, Centre National de la Recherche Scientifique (CNRS) UMR 8197, Institut National de la Santé et de la Recherche Médicale (INSERM) U1024, F-75005 Paris, France
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10
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Teotónio H, Estes S, Phillips PC, Baer CF. Experimental Evolution with Caenorhabditis Nematodes. Genetics 2017; 206:691-716. [PMID: 28592504 PMCID: PMC5499180 DOI: 10.1534/genetics.115.186288] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Accepted: 03/07/2017] [Indexed: 12/17/2022] Open
Abstract
The hermaphroditic nematode Caenorhabditis elegans has been one of the primary model systems in biology since the 1970s, but only within the last two decades has this nematode also become a useful model for experimental evolution. Here, we outline the goals and major foci of experimental evolution with C. elegans and related species, such as C. briggsae and C. remanei, by discussing the principles of experimental design, and highlighting the strengths and limitations of Caenorhabditis as model systems. We then review three exemplars of Caenorhabditis experimental evolution studies, underlining representative evolution experiments that have addressed the: (1) maintenance of genetic variation; (2) role of natural selection during transitions from outcrossing to selfing, as well as the maintenance of mixed breeding modes during evolution; and (3) evolution of phenotypic plasticity and its role in adaptation to variable environments, including host-pathogen coevolution. We conclude by suggesting some future directions for which experimental evolution with Caenorhabditis would be particularly informative.
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Affiliation(s)
- Henrique Teotónio
- Institut de Biologie de l´École Normale Supérieure (IBENS), Institut National de la Santé et de la Recherche Médicale U1024, Centre Nationnal de la Recherche Scientifique Unité Mixte de Recherche 8197, Paris Sciences et Lettres Research University, 75005 Paris, France
| | - Suzanne Estes
- Department of Biology, Portland State University, Oregon 97201
| | - Patrick C Phillips
- Institute of Ecology and Evolution, 5289 University of Oregon, Eugene, Oregon 97403, and
| | - Charles F Baer
- Department of Biology, and
- University of Florida Genetics Institute, University of Florida, Gainesville, Florida 32611
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11
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Morgan K, McGaughran A, Rödelsperger C, Sommer RJ. Variation in rates of spontaneous male production within the nematode species Pristionchus pacificus supports an adaptive role for males and outcrossing. BMC Evol Biol 2017; 17:57. [PMID: 28228092 PMCID: PMC5322664 DOI: 10.1186/s12862-017-0873-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 01/05/2017] [Indexed: 12/18/2022] Open
Abstract
Background The nematode species Pristionchus pacificus has an androdioecious mating system in which populations consist of self-fertilizing hermaphrodites and relatively few males. The prevalence of males in such a system is likely to depend on the relative pros and cons of outcrossing. While outcrossing generates novel allelic combinations and can therefore increase adaptive potential, it may also disrupt the potentially beneficial consequences of repeated generations of selfing. These include purging of deleterious alleles, inheritance of co-adapted allele complexes, improved hermaphrodite fitness and increased population growth. Here we use experimental and population genetic approaches to test hypotheses relating to male production and outcrossing in laboratory and natural populations of P. pacificus sampled from the volcanic island of La Réunion. Results We find a significant interaction between sampling locality and temperature treatment influencing rates of spontaneous male production in the laboratory. While strains isolated at higher altitude, cooler localities produce a higher proportion of male offspring at 25 °C relative to 20 or 15 °C, the reverse pattern is seen in strains isolated from warmer, low altitude localities. Linkage disequilibrium extends across long physical distances, but fails to approach levels reported for the partially selfing nematode species Caenorhabditis elegans. Finally, we find evidence for admixture between divergent genetic lineages. Conclusions Elevated rates of laboratory male generation appear to occur under environmental conditions which differ from those experienced by populations in nature. Such elevated male generation may result in higher outcrossing rates, hence driving increased effective recombination and the creation of potentially adaptive novel allelic combinations. Patterns of linkage disequilibrium decay support selfing as the predominant reproductive strategy in P. pacificus. Finally, despite the potential for outcrossing depression, our results suggest admixture has occurred between distinct genetic lineages since their independent colonization of the island, suggesting outcrossing depression may not be uniform in this species. Electronic supplementary material The online version of this article (doi:10.1186/s12862-017-0873-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Katy Morgan
- Department for Evolutionary Biology, Max Planck Institute for Developmental Biology, Tübingen, 72076, Germany. .,Department of Biological Sciences, University of New Orleans, 2000 Lakeshore Drive, New Orleans, LA70148, USA.
| | - Angela McGaughran
- Department for Evolutionary Biology, Max Planck Institute for Developmental Biology, Tübingen, 72076, Germany.,CSIRO Land & Water, Black Mountain Laboratories, Clunies Ross Street, Canberra, ACT 2601, Australia.,University of Melbourne, School of BioSciences, 30 Flemington Road, Melbourne, VIC, 3010, Australia
| | - Christian Rödelsperger
- Department for Evolutionary Biology, Max Planck Institute for Developmental Biology, Tübingen, 72076, Germany
| | - Ralf J Sommer
- Department for Evolutionary Biology, Max Planck Institute for Developmental Biology, Tübingen, 72076, Germany
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Noël E, Chemtob Y, Janicke T, Sarda V, Pélissié B, Jarne P, David P. Reduced mate availability leads to evolution of self-fertilization and purging of inbreeding depression in a hermaphrodite. Evolution 2016; 70:625-40. [DOI: 10.1111/evo.12886] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 02/02/2016] [Accepted: 02/05/2016] [Indexed: 12/30/2022]
Affiliation(s)
- Elsa Noël
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), UMR 5175, CNRS, Université de Montpellier; Université Paul Valéry Montpellier; EPHE, 1919 route de Mende 34293 Montpellier Cedex 5 France
| | - Yohann Chemtob
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), UMR 5175, CNRS, Université de Montpellier; Université Paul Valéry Montpellier; EPHE, 1919 route de Mende 34293 Montpellier Cedex 5 France
- Laboratoire Interdisciplinaire des Energies de Demain (LIED), UMR 8236; Université Paris Diderot; UFR Physique, Bâtiment Condorcet, 10 Rue A. Domon et L. Duquet 75205 Paris Cedex 13 France
| | - Tim Janicke
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), UMR 5175, CNRS, Université de Montpellier; Université Paul Valéry Montpellier; EPHE, 1919 route de Mende 34293 Montpellier Cedex 5 France
| | - Violette Sarda
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), UMR 5175, CNRS, Université de Montpellier; Université Paul Valéry Montpellier; EPHE, 1919 route de Mende 34293 Montpellier Cedex 5 France
| | - Benjamin Pélissié
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), UMR 5175, CNRS, Université de Montpellier; Université Paul Valéry Montpellier; EPHE, 1919 route de Mende 34293 Montpellier Cedex 5 France
| | - Philippe Jarne
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), UMR 5175, CNRS, Université de Montpellier; Université Paul Valéry Montpellier; EPHE, 1919 route de Mende 34293 Montpellier Cedex 5 France
| | - Patrice David
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), UMR 5175, CNRS, Université de Montpellier; Université Paul Valéry Montpellier; EPHE, 1919 route de Mende 34293 Montpellier Cedex 5 France
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Abstract
The roundworm Caenorhabditis elegans has risen to the status of a top model organism for biological research in the last fifty years. Among laboratory animals, this tiny nematode is one of the simplest and easiest organisms to handle. And its life outside the laboratory is beginning to be unveiled. Like other model organisms, C. elegans has a boom-and-bust lifestyle. It feasts on ephemeral bacterial blooms in decomposing fruits and stems. After resource depletion, its young larvae enter a migratory diapause stage, called the dauer. Organisms known to be associated with C. elegans include migration vectors (such as snails, slugs and isopods) and pathogens (such as microsporidia, fungi, bacteria and viruses). By deepening our understanding of the natural history of C. elegans, we establish a broader context and improved tools for studying its biology.
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Affiliation(s)
- Lise Frézal
- Institute of Biology of Ecole Normale Supérieure, Centre National de la Recherche Scientifique, Paris, France
| | - Marie-Anne Félix
- Institute of Biology of Ecole Normale Supérieure, Centre National de la Recherche Scientifique, Paris, France
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14
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Theologidis I, Chelo IM, Goy C, Teotónio H. Reproductive assurance drives transitions to self-fertilization in experimental Caenorhabditis elegans. BMC Biol 2014; 12:93. [PMID: 25369737 PMCID: PMC4234830 DOI: 10.1186/s12915-014-0093-1] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Accepted: 10/23/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Evolutionary transitions from outcrossing between individuals to selfing are partly responsible for the great diversity of animal and plant reproduction systems. The hypothesis of 'reproductive assurance' suggests that transitions to selfing occur because selfers that are able to reproduce on their own ensure the persistence of populations in environments where mates or pollination agents are unavailable. Here we test this hypothesis by performing experimental evolution in Caenorhabditis elegans. RESULTS We show that self-compatible hermaphrodites provide reproductive assurance to a male-female population facing a novel environment where outcrossing is limiting. Invasions of hermaphrodites in male-female populations, and subsequent experimental evolution in the novel environment, led to successful transitions to selfing and adaptation. Adaptation was not due to the loss of males during transitions, as shown by evolution experiments in exclusively hermaphroditic populations and in male-hermaphrodite populations. Instead, adaptation was due to the displacement of females by hermaphrodites. Genotyping of single-nucleotide polymorphisms further indicated that the observed evolution of selfing rates was not due to selection of standing genetic diversity. Finally, numerical modelling and evolution experiments in male-female populations demonstrate that the improvement of male fitness components may diminish the opportunity for reproductive assurance. CONCLUSIONS Our findings support the hypothesis that reproductive assurance can drive the transition from outcrossing to selfing, and further suggest that the success of transitions to selfing hinges on adaptation of obligate outcrossing populations to the environment where outcrossing was once a limiting factor.
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Carvalho S, Chelo IM, Goy C, Teotónio H. The role of hermaphrodites in the experimental evolution of increased outcrossing rates in Caenorhabditis elegans. BMC Evol Biol 2014; 14:116. [PMID: 24891031 PMCID: PMC4055231 DOI: 10.1186/1471-2148-14-116] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 05/21/2014] [Indexed: 01/16/2023] Open
Abstract
Background Why most organisms reproduce via outcrossing rather than selfing is a central question in evolutionary biology. It has long ago been suggested that outcrossing is favoured when it facilitates adaptation to novel environments. We have previously shown that the experimental evolution of increased outcrossing rates in populations of the male-hermaphrodite nematode Caenorhabditis elegans were correlated with the experimental evolution of increased male fitness. However, it is unknown whether outcrossing led to adaptation, and if so, which fitness components can explain the observed increase in outcrossing rates. Results Using experimental evolution in six populations with initially low standing levels of genetic diversity, we show with head-to-head competition assays that population-wide fitness improved during 100 generations. Since outcrossing rates increased during the same period, this result demonstrates that outcrossing is adaptive. We also show that there was little evolution of hermaphrodite fitness under conditions of selfing or under conditions of outcrossing with unrelated tester males. We nonetheless find a positive genetic correlation between hermaphrodite self-fitness and population-wide fitness, and a negative genetic correlation between hermaphrodite mating success and population-wide fitness. These results suggest that the several hermaphrodite traits measured are fitness components. Tradeoffs expressed in hermaphrodites, particularly noticed between self-fitness and mating success, may in turn explain their lack of change during experimental evolution. Conclusions Our findings indicate that outcrossing facilitates adaptation to novel environments. They further indicate that the experimental evolution of increased outcrossing rates depended little on hermaphrodites because of fitness tradeoffs between selfing and outcrossing. Instead, the evolution of increased outcrossing rates appears to have resulted from unhindered selection on males.
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16
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Carvalho S, Phillips PC, Teotónio H. Hermaphrodite life history and the maintenance of partial selfing in experimental populations of Caenorhabditis elegans. BMC Evol Biol 2014; 14:117. [PMID: 24891140 PMCID: PMC4052797 DOI: 10.1186/1471-2148-14-117] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 05/21/2014] [Indexed: 01/18/2023] Open
Abstract
Background Classic population genetics theory predicts that mixed reproductive systems, where self reproduction (selfing) and outcrossing co-exist, should not be as common as they are in nature. One means of reconciling theory with observations is to recognize that sexual conflict between males and hermaphrodites and/or constraints in the allocation of resources towards sex functions in hermaphrodites can balance the fitness components of selfing and outcrossing. Results Using experimental evolution in Caenorhabditis elegans, we test whether the adaptive maintenance of partial selfing is due to sexual conflict and/or to the evolution of sex allocation towards male function in hermaphrodites. For this, we characterized the reproductive schedule and longevity patterns in hermaphrodites under selfing and under outcrossing with naïve males that did not have the opportunity to evolve with them. A shift in reproductive schedule towards earlier reproduction would be indicative of adaptation in our imposed life-cycle, while longevity is expected to evolve as a response to the harm that males impinge on hermaphrodites upon mating. To determine adaptation in the absence of constraints in sex allocation, we also characterized the life history of females that reproduced during experimental evolution through obligate mating with males. As expected with adaptation, we find that after 100 generations of experimental evolution, selfing hermaphrodites and females showed improved reproduction at earlier ages. We did not observe similar reproductive shifts in outcrossed hermaphrodites. We further find increased longevity in outcrossed females after evolution but not in outcrossed hermaphrodites, a result that indicates that sexual conflicts were likely more prevalent under male–female evolution than under male-hermaphrodite evolution. Conclusions Taken together, our findings suggest that the adaptive maintenance of partial selfing during C. elegans experimental evolution resulted from the evolution of sex allocation towards male function in hermaphrodites.
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Affiliation(s)
| | | | - Henrique Teotónio
- Instituto Gulbenkian de Ciência, Apartado 14, P-2781-901 Oeiras, Portugal.
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