1
|
Crombie TA, McKeown R, Moya ND, Evans K, Widmayer S, LaGrassa V, Roman N, Tursunova O, Zhang G, Gibson S, Buchanan C, Roberto N, Vieira R, Tanny R, Andersen E. CaeNDR, the Caenorhabditis Natural Diversity Resource. Nucleic Acids Res 2024; 52:D850-D858. [PMID: 37855690 PMCID: PMC10767927 DOI: 10.1093/nar/gkad887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 09/30/2023] [Accepted: 10/06/2023] [Indexed: 10/20/2023] Open
Abstract
Studies of model organisms have provided important insights into how natural genetic differences shape trait variation. These discoveries are driven by the growing availability of genomes and the expansive experimental toolkits afforded to researchers using these species. For example, Caenorhabditis elegans is increasingly being used to identify and measure the effects of natural genetic variants on traits using quantitative genetics. Since 2016, the C. elegans Natural Diversity Resource (CeNDR) has facilitated many of these studies by providing an archive of wild strains, genome-wide sequence and variant data for each strain, and a genome-wide association (GWA) mapping portal for the C. elegans community. Here, we present an updated platform, the Caenorhabditis Natural Diversity Resource (CaeNDR), that enables quantitative genetics and genomics studies across the three Caenorhabditis species: C. elegans, C. briggsae and C. tropicalis. The CaeNDR platform hosts several databases that are continually updated by the addition of new strains, whole-genome sequence data and annotated variants. Additionally, CaeNDR provides new interactive tools to explore natural variation and enable GWA mappings. All CaeNDR data and tools are accessible through a freely available web portal located at caendr.org.
Collapse
Affiliation(s)
- Timothy A Crombie
- Department of Biomedical and Chemical Engineering and Sciences, Florida Institute of Technology, Melbourne, FL, USA
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Ryan McKeown
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
- Interdisciplinary Biological Sciences Program, Northwestern University, Evanston, IL, USA
| | - Nicolas D Moya
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
- Cell, Molecular, Developmental biology, and Biophysics Graduate Program, ohns Hopkins University, Baltimore, MD, USA
| | - Kathryn S Evans
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Samuel J Widmayer
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Vincent LaGrassa
- Northwestern University Information Technology, Media and Technology Innovation, Northwestern University, Evanston, IL USA
| | - Natalie Roman
- Northwestern University Information Technology, Media and Technology Innovation, Northwestern University, Evanston, IL USA
| | - Orzu Tursunova
- Northwestern University Information Technology, Media and Technology Innovation, Northwestern University, Evanston, IL USA
| | - Gaotian Zhang
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Sophia B Gibson
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Claire M Buchanan
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Nicole M Roberto
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Rodolfo Vieira
- Northwestern University Information Technology, Media and Technology Innovation, Northwestern University, Evanston, IL USA
| | - Robyn E Tanny
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| | - Erik C Andersen
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| |
Collapse
|
2
|
Hine E, Runcie DE, Allen SL, Wang Y, Chenoweth SF, Blows MW, McGuigan K. Maintenance of quantitative genetic variance in complex, multi-trait phenotypes: The contribution of rare, large effect variants in two Drosophila species. Genetics 2022; 222:6663993. [PMID: 35961029 PMCID: PMC9526065 DOI: 10.1093/genetics/iyac122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 08/02/2022] [Indexed: 11/29/2022] Open
Abstract
The interaction of evolutionary processes to determine quantitative genetic variation has implications for contemporary and future phenotypic evolution, as well as for our ability to detect causal genetic variants. While theoretical studies have provided robust predictions to discriminate among competing models, empirical assessment of these has been limited. In particular, theory highlights the importance of pleiotropy in resolving observations of selection and mutation, but empirical investigations have typically been limited to few traits. Here, we applied high-dimensional Bayesian Sparse Factor Genetic modeling to gene expression datasets in 2 species, Drosophila melanogaster and Drosophila serrata, to explore the distributions of genetic variance across high-dimensional phenotypic space. Surprisingly, most of the heritable trait covariation was due to few lines (genotypes) with extreme [>3 interquartile ranges (IQR) from the median] values. Intriguingly, while genotypes extreme for a multivariate factor also tended to have a higher proportion of individual traits that were extreme, we also observed genotypes that were extreme for multivariate factors but not for any individual trait. We observed other consistent differences between heritable multivariate factors with outlier lines vs those factors without extreme values, including differences in gene functions. We use these observations to identify further data required to advance our understanding of the evolutionary dynamics and nature of standing genetic variation for quantitative traits.
Collapse
Affiliation(s)
- Emma Hine
- School of Biological Sciences, The University of Queensland, Brisbane 4072 Australia
| | - Daniel E Runcie
- Department of Plant Sciences, University of California Davis, Davis, CA 95616, USA
| | - Scott L Allen
- School of Biological Sciences, The University of Queensland, Brisbane 4072 Australia
| | - Yiguan Wang
- School of Biological Sciences, The University of Queensland, Brisbane 4072 Australia.,Institute of Evolutionary Biology, University of Edinburgh, Edinburgh, EH9 3FL, UK
| | - Stephen F Chenoweth
- School of Biological Sciences, The University of Queensland, Brisbane 4072 Australia
| | - Mark W Blows
- School of Biological Sciences, The University of Queensland, Brisbane 4072 Australia
| | - Katrina McGuigan
- School of Biological Sciences, The University of Queensland, Brisbane 4072 Australia
| |
Collapse
|
3
|
Conradsen C, Blows MW, McGuigan K. Causes of variability in estimates of mutational variance from mutation accumulation experiments. Genetics 2022; 221:6569838. [PMID: 35435211 PMCID: PMC9157167 DOI: 10.1093/genetics/iyac060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 04/08/2022] [Indexed: 11/15/2022] Open
Abstract
Characteristics of the new phenotypic variation introduced via mutation have broad implications in evolutionary and medical genetics. Standardized estimates of this mutational variance, VM, span 2 orders of magnitude, but the causes of this remain poorly resolved. We investigated estimate heterogeneity using 2 approaches. First, meta-analyses of ∼150 estimates of standardized VM from 37 mutation accumulation studies did not support a difference among taxa (which differ in mutation rate) but provided equivocal support for differences among trait types (life history vs morphology, predicted to differ in mutation rate). Notably, several experimental factors were confounded with taxon and trait, and further empirical data are required to resolve their influences. Second, we analyzed morphological data from an experiment in Drosophila serrata to determine the potential for unintentional heterogeneity among environments in which phenotypes were measured (i.e. among laboratories or time points) or transient segregation of mutations within mutation accumulation lines to affect standardized VM. Approximating the size of an average mutation accumulation experiment, variability among repeated estimates of (accumulated) mutational variance was comparable to variation among published estimates of standardized VM. This heterogeneity was (partially) attributable to unintended environmental variation or within line segregation of mutations only for wing size, not wing shape traits. We conclude that sampling error contributed substantial variation within this experiment, and infer that it will also contribute substantially to differences among published estimates. We suggest a logistically permissive approach to improve the precision of estimates, and consequently our understanding of the dynamics of mutational variance of quantitative traits.
Collapse
Affiliation(s)
- Cara Conradsen
- School of Biological Sciences; The University of Queensland; St. Lucia, Queensland, Australia 4072
| | - Mark W Blows
- School of Biological Sciences; The University of Queensland; St. Lucia, Queensland, Australia 4072
| | - Katrina McGuigan
- School of Biological Sciences; The University of Queensland; St. Lucia, Queensland, Australia 4072
| |
Collapse
|
4
|
Heaton A, Faulconer E, Milligan E, Kroetz MB, Weir SM, Glaberman S. Interspecific Variation in Nematode Responses to Metals. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2020; 39:1006-1016. [PMID: 32072668 DOI: 10.1002/etc.4689] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 11/25/2019] [Accepted: 02/12/2020] [Indexed: 06/10/2023]
Abstract
Performing toxicity testing on multiple species with differing degrees of evolutionary relatedness can provide important information on how chemical sensitivity varies among species and can help pinpoint the biological drivers of species sensitivity. Such knowledge could ultimately be used to design better multispecies predictive ecological risk assessment models and identify particularly sensitive species. However, laboratory toxicity tests involving multiple species can also be resource intensive, especially when each species has unique husbandry conditions. We performed lethality tests with 2 metals, copper chloride and zinc chloride, on 5 different nematode species, which are nested in their degree of evolutionary relatedness: Caenorhabditis briggsae, Caenorhabditis elegans, Oscheius myriophila, Oscheius tipulae, and Pristionchus pacificus. All species were successfully cultured and tested concurrently with limited resources, demonstrating that inexpensive, multispecies nematode toxicity testing systems are achievable. The results indicate that P. pacificus is the most sensitive to both metals. Conversely, C. elegans is the least sensitive species to copper, but the second most sensitive to zinc, indicating that species relationships do not necessarily predict species sensitivity. Toxicity testing with additional nematode species and types of chemicals is feasible and will help form more generalizable conclusions about relative species sensitivity. Environ Toxicol Chem 2020;39:1006-1016. © 2020 SETAC.
Collapse
Affiliation(s)
- Andrew Heaton
- Department of Biology, University of South Alabama, Mobile, Alabama, USA
| | | | - Emma Milligan
- Department of Biology, University of South Alabama, Mobile, Alabama, USA
| | - Mary B Kroetz
- Department of Biology, University of South Alabama, Mobile, Alabama, USA
| | - Scott M Weir
- Department of Biology, Queens University of Charlotte, Charlotte, North Carolina, USA
| | - Scott Glaberman
- Department of Biology, University of South Alabama, Mobile, Alabama, USA
- Department of Environmental Science & Policy, George Mason University, Fairfax, Virginia, USA
| |
Collapse
|
5
|
Woodruff GC, Johnson E, Phillips PC. A large close relative of C. elegans is slow-developing but not long-lived. BMC Evol Biol 2019; 19:74. [PMID: 30866802 PMCID: PMC6416856 DOI: 10.1186/s12862-019-1388-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 02/13/2019] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Variation in body size is thought to be a major driver of a wide variety of ecological and evolutionary patterns, including changes in development, reproduction, and longevity. Additionally, drastic changes in natural context often have profound effects on multiple fitness-related traits. Caenorhabditis inopinata is a recently-discovered fig-associated nematode that is unusually large relative to other members of the genus, including the closely related model system C. elegans. Here we test whether the dramatic increase in body size and shift in ecological context has led to correlated changes in key life history and developmental parameters within this species. RESULTS Using four developmental milestones, C. inopinata was found to have a slower rate of development than C. elegans across a range of temperatures. Despite this, C. inopinata did not reveal any differences in adult lifespan from C. elegans after accounting for differences in developmental timing and reproductive mode. C. inopinata fecundity was generally lower than that of C. elegans, but fitness improved under continuous-mating, consistent with sperm-limitation under gonochoristic (male/female) reproduction. C. inopinata also revealed greater fecundity and viability at higher temperatures. CONCLUSION Consistent with observations in other ectotherms, slower growth in C. inopinata indicates a potential trade-off between body size and developmental timing, whereas its unchanged lifespan suggests that longevity is largely uncoupled from its increase in body size. Additionally, temperature-dependent patterns of fitness in C. inopinata are consistent with its geographic origins in subtropical Okinawa. Overall, these results underscore the extent to which changes in ecological context and body size can shape life history traits.
Collapse
Affiliation(s)
- Gavin C. Woodruff
- Department of Biology, Institute of Ecology and Evolution, University of Oregon, Eugene, USA
| | - Erik Johnson
- Department of Biology, Institute of Ecology and Evolution, University of Oregon, Eugene, USA
| | - Patrick C. Phillips
- Department of Biology, Institute of Ecology and Evolution, University of Oregon, Eugene, USA
| |
Collapse
|
6
|
Jonas M, Navarro D. Induced mutations alter patterns of quantitative variation, phenotypic integration, and plasticity to elevated CO 2 in Arabidopsis thaliana. JOURNAL OF PLANT RESEARCH 2019; 132:33-47. [PMID: 30255212 DOI: 10.1007/s10265-018-1064-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 09/03/2018] [Indexed: 06/08/2023]
Abstract
A key step toward predicting responses to climate change is characterizing genetic variation in populations. While short-term responses will likely be shaped by currently available genetic variation, longer-term evolutionary responses will depend on the supply of novel variation by, ultimately, mutation. Studying mutational contributions to phenotypic variation can provide insights into the extent of potential variation on which selection may operate in future human-altered environments. Here we used the chemical mutagen ethyl methanesulfonate (EMS) to explore mutational contributions to phenotypic variation, integration, and plasticity to elevated carbon dioxide (eCO2) in three accessions of Arabidopsis thaliana. We found that (1) mutagenesis increased broad-sense heritabilities and variation in plasticity to eCO2 (genotype by environment interactions); (2) mutational effects varied among the three genetic backgrounds; (3) induced mutations had non-random (biased) effects on patterns of phenotypic integration. To our knowledge, this is the first study to address the effects of chemically induced mutations on phenotypic plasticity to eCO2 in a model plant. We discuss our results in light of emerging insights from theoretical and empirical quantitative genetics, suggest potential avenues of research, and identify approaches that may help advance our understanding of climate-driven evolution in plants.
Collapse
Affiliation(s)
- Mark Jonas
- Department of Biology, School of Natural and Social Sciences, State University of New York-Purchase College, 735 Anderson Hill Road, Purchase, NY, 10577, USA.
| | - Dania Navarro
- Department of Biology, School of Natural and Social Sciences, State University of New York-Purchase College, 735 Anderson Hill Road, Purchase, NY, 10577, USA
| |
Collapse
|
7
|
Vanhoenacker E, Sandell L, Roze D. Stabilizing selection, mutational bias, and the evolution of sex*. Evolution 2018; 72:1740-1758. [DOI: 10.1111/evo.13547] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 06/20/2018] [Indexed: 12/16/2022]
Affiliation(s)
- Eloïse Vanhoenacker
- CNRS UMI 3614 Evolutionary Biology and Ecology of Algae 29688 Roscoff France
- Sorbonne Université 29688 Roscoff France
| | - Linnéa Sandell
- Department of Zoology University of British Columbia Vancouver BC V6T1Z4 Canada
| | - Denis Roze
- CNRS UMI 3614 Evolutionary Biology and Ecology of Algae 29688 Roscoff France
- Sorbonne Université 29688 Roscoff France
| |
Collapse
|
8
|
Malerba ME, White CR, Marshall DJ. Eco-energetic consequences of evolutionary shifts in body size. Ecol Lett 2017; 21:54-62. [PMID: 29143436 DOI: 10.1111/ele.12870] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 09/14/2017] [Accepted: 09/30/2017] [Indexed: 11/30/2022]
Abstract
Size imposes physiological and ecological constraints upon all organisms. Theory abounds on how energy flux covaries with body size, yet causal links are often elusive. As a more direct way to assess the role of size, we used artificial selection to evolve the phytoplankton species Dunaliella tertiolecta towards smaller and larger body sizes. Within 100 generations (c. 1 year), we generated a fourfold difference in cell volume among selected lineages. Large-selected populations produced four times the energy than small-selected populations of equivalent total biovolume, but at the cost of much higher volume-specific respiration. These differences in energy utilisation between large (more productive) and small (more energy-efficient) individuals were used to successfully predict ecological performance (r and K) across novel resource regimes. We show that body size determines the performance of a species by mediating its net energy flux, with worrying implications for current trends in size reduction and for global carbon cycles.
Collapse
Affiliation(s)
- Martino E Malerba
- Centre of Geometric Biology, School of Biological Sciences, Monash University, Melbourne, Vic., 3800, Australia
| | - Craig R White
- Centre of Geometric Biology, School of Biological Sciences, Monash University, Melbourne, Vic., 3800, Australia
| | - Dustin J Marshall
- Centre of Geometric Biology, School of Biological Sciences, Monash University, Melbourne, Vic., 3800, Australia
| |
Collapse
|
9
|
McGuigan K, Aw E. How does mutation affect the distribution of phenotypes? Evolution 2017; 71:2445-2456. [PMID: 28884791 DOI: 10.1111/evo.13358] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 08/27/2017] [Accepted: 08/29/2017] [Indexed: 12/14/2022]
Abstract
The potential for mutational processes to influence patterns of neutral or adaptive phenotypic evolution is not well understood. If mutations are directionally biased, shifting trait means in a particular direction, or if mutation generates more variance in some directions of multivariate trait space than others, mutation itself might be a source of bias in phenotypic evolution. Here, we use mutagenesis to investigate the affect of mutation on trait mean and (co)variances in zebrafish, Danio rerio. Mutation altered the relationship between age and both prolonged swimming speed and body shape. These observations suggest that mutational effects on ontogeny or aging have the potential to generate variance across the phenome. Mutations had a far greater effect in males than females, although whether this is a reflection of sex-specific ontogeny or aging remains to be determined. In males, mutations generated positive covariance between swimming speed, size, and body shape suggesting the potential for mutation to affect the evolutionary covariation of these traits. Overall, our observations suggest that mutation does not generate equal variance in all directions of phenotypic space or in each sex, and that pervasive variation in ontogeny or aging within a cohort could affect the variation available to evolution.
Collapse
Affiliation(s)
- Katrina McGuigan
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland 4072
| | - Ernest Aw
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland 4072
| |
Collapse
|
10
|
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: 53] [Impact Index Per Article: 7.6] [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.
Collapse
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
| |
Collapse
|
11
|
Davies SK, Leroi A, Burt A, Bundy JG, Baer CF. The mutational structure of metabolism in Caenorhabditis elegans. Evolution 2016; 70:2239-2246. [PMID: 27465022 PMCID: PMC5050113 DOI: 10.1111/evo.13020] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Revised: 06/27/2016] [Accepted: 07/10/2016] [Indexed: 12/14/2022]
Abstract
A properly functioning organism must maintain metabolic homeostasis. Deleterious mutations degrade organismal function, presumably at least in part via effects on metabolic function. Here we present an initial investigation into the mutational structure of the Caenorhabditis elegans metabolome by means of a mutation accumulation experiment. We find that pool sizes of 29 metabolites vary greatly in their vulnerability to mutation, both in terms of the rate of accumulation of genetic variance (the mutational variance, VM) and the rate of change of the trait mean (the mutational bias, ΔM). Strikingly, some metabolites are much more vulnerable to mutation than any other trait previously studied in the same way. Although we cannot statistically assess the strength of mutational correlations between individual metabolites, principal component analysis provides strong evidence that some metabolite pools are genetically correlated, but also that there is substantial scope for independent evolution of different groups of metabolites. Averaged over mutation accumulation lines, PC3 is positively correlated with relative fitness, but a model in which metabolites are uncorrelated with fitness is nearly as good by Akaike's Information Criterion.
Collapse
Affiliation(s)
- Sarah K Davies
- Department of Life Sciences, Imperial College London, United Kingdom
- Department of Surgery and Cancer, Imperial College London, United Kingdom
| | - Armand Leroi
- Department of Life Sciences, Imperial College London, United Kingdom
| | - Austin Burt
- Department of Life Sciences, Imperial College London, United Kingdom
| | - Jacob G Bundy
- Department of Surgery and Cancer, Imperial College London, United Kingdom
| | - Charles F Baer
- Department of Biology, University of Florida, Gainesville, Florida.
- Genetics Institute, University of Florida, Gainesville, Florida.
| |
Collapse
|
12
|
Mutation Is a Sufficient and Robust Predictor of Genetic Variation for Mitotic Spindle Traits in Caenorhabditis elegans. Genetics 2016; 203:1859-70. [PMID: 27334268 DOI: 10.1534/genetics.115.185736] [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: 12/04/2015] [Accepted: 06/13/2016] [Indexed: 12/24/2022] Open
Abstract
Different types of phenotypic traits consistently exhibit different levels of genetic variation in natural populations. There are two potential explanations: Either mutation produces genetic variation at different rates or natural selection removes or promotes genetic variation at different rates. Whether mutation or selection is of greater general importance is a longstanding unresolved question in evolutionary genetics. We report mutational variances (VM) for 19 traits related to the first mitotic cell division in Caenorhabditis elegans and compare them to the standing genetic variances (VG) for the same suite of traits in a worldwide collection C. elegans Two robust conclusions emerge. First, the mutational process is highly repeatable: The correlation between VM in two independent sets of mutation accumulation lines is ∼0.9. Second, VM for a trait is a good predictor of VG for that trait: The correlation between VM and VG is ∼0.9. This result is predicted for a population at mutation-selection balance; it is not predicted if balancing selection plays a primary role in maintaining genetic variation.
Collapse
|
13
|
Abstract
DNA does not make phenotypes on its own. In this volume entitled "Genes and Phenotypic Evolution," the present review draws the attention on the process of phenotype construction-including development of multicellular organisms-and the multiple interactions and feedbacks between DNA, organism, and environment at various levels and timescales in the evolutionary process. First, during the construction of an individual's phenotype, DNA is recruited as a template for building blocks within the cellular context and may in addition be involved in dynamical feedback loops that depend on the environmental and organismal context. Second, in the production of phenotypic variation among individuals, stochastic, environmental, genetic, and parental sources of variation act jointly. While in controlled laboratory settings, various genetic and environmental factors can be tested one at a time or in various combinations, they cannot be separated in natural populations because the environment is not controlled and the genotype can rarely be replicated. Third, along generations, genotype and environment each have specific properties concerning the origin of their variation, the hereditary transmission of this variation, and the evolutionary feedbacks. Natural selection acts as a feedback from phenotype and environment to genotype. This review integrates recent results and concrete examples that illustrate these three points. Although some themes are shared with recent calls and claims to a new conceptual framework in evolutionary biology, the viewpoint presented here only means to add flesh to the standard evolutionary synthesis.
Collapse
Affiliation(s)
- M-A Félix
- Institut de Biologie Ecole Normale Supérieure, CNRS, Paris, France.
| |
Collapse
|
14
|
Bi Z, Gong Y, Huang X, Yu H, Bai L, Hu J. Efficacy of Four Nematicides Against the Reproduction and Development of Pinewood Nematode, Bursaphelenchus xylophilus. J Nematol 2015; 47:126-132. [PMID: 26170474 PMCID: PMC4492287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Indexed: 06/04/2023] Open
Abstract
To understand the efficacy of emamectin benzoate, avermectin, milbemectin, and thiacloprid on the reproduction and development of Bursaphelenchus xylophilus, seven parameters, namely population growth, fecundity, egg hatchability, larval lethality, percent larval development, body size, and sexual ratio, were investigated using sublethal (LC20) doses of these compounds in the laboratory. Emamectin benzoate treatment led to a significant suppression in population size, brood size, and percent larval development with 411, 3.50, and 49.63%, respectively, compared to 20850, 24.33, and 61.43% for the negative control. The embryonic and larval lethality increased obviously from 12.47% and 13.70% to 51.37% and 75.30%, respectively. In addition, the body length was also significantly reduced for both males and females in the emamectin benzoate treatment. Avermectin and milbemectin were also effective in suppressing population growth by increasing larval lethality and reducing larval development, although they did not affect either brood size or embryonic lethality. Body length for both male and female worms was increased by avermectin. Thiacloprid caused no adverse reproductive effects, although it suppressed larval development. Sexual ratio was not affected by any of these four nematicides. Our results indicate that emamectin benzoate, milbemectin, and avermectin are effective against the reproduction of B. xylophilus. We think these three nematicides can be useful for the control of pine wilt disease.
Collapse
Affiliation(s)
- Zhenzhen Bi
- Zhejiang Provincial Key Laboratory of Chemical Utilization of Forestry Biomass, Zhejiang Agricultural & Forestry University, Lin'an, Zhejiang Province, 311300, P.R. China
| | - Yanting Gong
- Zhejiang Provincial Key Laboratory of Chemical Utilization of Forestry Biomass, Zhejiang Agricultural & Forestry University, Lin'an, Zhejiang Province, 311300, P.R. China
| | - Xiaojuan Huang
- Zhejiang Provincial Key Laboratory of Chemical Utilization of Forestry Biomass, Zhejiang Agricultural & Forestry University, Lin'an, Zhejiang Province, 311300, P.R. China
| | - Hongshi Yu
- Zhejiang Provincial Key Laboratory of Chemical Utilization of Forestry Biomass, Zhejiang Agricultural & Forestry University, Lin'an, Zhejiang Province, 311300, P.R. China
| | - Liqun Bai
- Zhejiang Provincial Key Laboratory of Chemical Utilization of Forestry Biomass, Zhejiang Agricultural & Forestry University, Lin'an, Zhejiang Province, 311300, P.R. China
| | - Jiafu Hu
- Zhejiang Provincial Key Laboratory of Chemical Utilization of Forestry Biomass, Zhejiang Agricultural & Forestry University, Lin'an, Zhejiang Province, 311300, P.R. China. ; Collaborative Innovation Center of Sustaintable Forestry in Southern China, Nanjing Forestry University
| |
Collapse
|
15
|
Etienne V, Andersen EC, Ponciano JM, Blanton D, Cadavid A, Joyner-Matos J, Matsuba C, Tabman B, Baer CF. The red death meets the abdominal bristle: polygenic mutation for susceptibility to a bacterial pathogen in Caenorhabditis elegans. Evolution 2015; 69:508-19. [PMID: 25495240 DOI: 10.1111/evo.12585] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 12/04/2014] [Indexed: 12/21/2022]
Abstract
Understanding the genetic basis of susceptibility to pathogens is an important goal of medicine and of evolutionary biology. A key first step toward understanding the genetics and evolution of any phenotypic trait is characterizing the role of mutation. However, the rate at which mutation introduces genetic variance for pathogen susceptibility in any organism is essentially unknown. Here, we quantify the per-generation input of genetic variance by mutation (VM) for susceptibility of Caenorhabditis elegans to the pathogenic bacterium Pseudomonas aeruginosa (defined as the median time of death, LT50). VM for LT50 is slightly less than VM for a variety of life-history and morphological traits in this strain of C. elegans, but is well within the range of reported values in a variety of organisms. Mean LT50 did not change significantly over 250 generations of mutation accumulation. Comparison of VM to the standing genetic variance (VG) implies a strength of selection against new mutations of a few tenths of a percent. These results suggest that the substantial standing genetic variation for susceptibility of C. elegans to P. aeruginosa can be explained by polygenic mutation coupled with purifying selection.
Collapse
Affiliation(s)
- Veronique Etienne
- Department of Biology, University of Florida, P.O. Box 118525, Gainesville, Florida, 32611
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Latimer CAL, McGuigan K, Wilson RS, Blows MW, Chenoweth SF. The contribution of spontaneous mutations to thermal sensitivity curve variation in Drosophila serrata. Evolution 2014; 68:1824-37. [PMID: 24576006 DOI: 10.1111/evo.12392] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 01/27/2014] [Indexed: 10/25/2022]
Abstract
Many traits studied in ecology and evolutionary biology change their expression in response to a continuously varying environmental factor. One well-studied example are thermal performance curves (TPCs); continuous reaction norms that describe the relationship between organismal performance and temperature and are useful for understanding the trade-offs involved in thermal adaptation. We characterized curves describing the thermal sensitivity of voluntary locomotor activity in a set of 66 spontaneous mutation accumulation lines in the fly Drosophila serrata. Factor-analytic modeling of the mutational variance-covariance matrix, M, revealed support for three axes of mutational variation in males and two in females. These independent axes of mutational variance corresponded well to the major axes of TPC variation required for different types of thermal adaptation; "faster-slower" representing changes in performance largely independent of temperature, and the "hotter-colder" and "generalist-specialist" axes, representing trade-offs. In contrast to its near-absence from standing variance in this species, a "faster-slower" axis, accounted for most mutational variance (75% in males and 66% in females) suggesting selection may easily fix or remove these types of mutations in outbred populations. Axes resembling the "hotter-colder" and "generalist-specialist" modes of variation contributed less mutational variance but nonetheless point to an appreciable input of new mutations that may contribute to thermal adaptation.
Collapse
Affiliation(s)
- Camille A L Latimer
- School of Biological Sciences, University of Queensland, St. Lucia, Queensland, 4072, Australia
| | | | | | | | | |
Collapse
|
17
|
Morran LT, Parrish RC, Gelarden IA, Lively CM. Temporal dynamics of outcrossing and host mortality rates in host-pathogen experimental coevolution. Evolution 2012; 67:1860-8. [PMID: 23815644 DOI: 10.1111/evo.12007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Accepted: 10/23/2012] [Indexed: 12/13/2022]
Abstract
Cross-fertilization is predicted to facilitate the short-term response and the long-term persistence of host populations engaged in antagonistic coevolutionary interactions. Consistent with this idea, our previous work has shown that coevolving bacterial pathogens (Serratia marcescens) can drive obligately selfing hosts (Caenorhabditis elegans) to extinction, whereas the obligately outcrossing and partially outcrossing populations persisted. We focused the present study on the partially outcrossing (mixed mating) and obligately outcrossing hosts, and analyzed the changes in the host resistance/avoidance (and pathogen infectivity) over time. We found that host mortality rates increased in the mixed mating populations over the first 10 generations of coevolution when outcrossing rates were initially low. However, mortality rates decreased after elevated outcrossing rates evolved during the experiment. In contrast, host mortality rates decreased in the obligately outcrossing populations during the first 10 generations of coevolution, and remained low throughout the experiment. Therefore, predominant selfing reduced the ability of the hosts to respond to coevolving pathogens compared to outcrossing hosts. Thus, we found that host-pathogen coevolution can generate rapid evolutionary change, and that host mating system can influence the outcome of coevolution at a fine temporal scale.
Collapse
Affiliation(s)
- Levi T Morran
- Department of Biology, Indiana University, Bloomington, IN, USA.
| | | | | | | |
Collapse
|
18
|
Abstract
Theoretical explanations of empirically observed standing genetic variation, mutation, and selection suggest that many alleles must jointly affect fitness and metric traits. However, there are few direct demonstrations of the nature and extent of these pleiotropic associations. We implemented a mutation accumulation (MA) divergence experimental design in Drosophila serrata to segregate genetic variants for fitness and metric traits. By exploiting naturally occurring MA line extinctions as a measure of line-level total fitness, manipulating sexual selection, and measuring productivity we were able to demonstrate genetic covariance between fitness and standard metric traits, wing size, and shape. Larger size was associated with lower total fitness and male sexual fitness, but higher productivity. Multivariate wing shape traits, capturing major axes of wing shape variation among MA lines, evolved only in the absence of sexual selection, and to the greatest extent in lines that went extinct, indicating that mutations contributing wing shape variation also typically had deleterious effects on both total fitness and male sexual fitness. This pleiotropic covariance of metric traits with fitness will drive their evolution, and generate the appearance of selection on the metric traits even in the absence of a direct contribution to fitness.
Collapse
Affiliation(s)
- Katrina McGuigan
- School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072, Australia.
| | | |
Collapse
|
19
|
Caenorhabditis elegans as a platform for molecular quantitative genetics and the systems biology of natural variation. Genet Res (Camb) 2011; 92:331-48. [PMID: 21429266 DOI: 10.1017/s0016672310000601] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Over the past 30 years, the characteristics that have made the nematode Caenorhabditis elegans one of the premier animal model systems have also allowed it to emerge as a powerful model system for determining the genetic basis of quantitative traits, particularly for the identification of naturally segregating and/or lab-adapted alleles with large phenotypic effects. To better understand the genetic underpinnings of natural variation in other complex phenotypes, C. elegans is uniquely poised in the emerging field of quantitative systems biology because of the extensive knowledge of cellular and neural bases to such traits. However, perturbations in standing genetic variation and patterns of linkage disequilibrium among loci are likely to limit our ability to tie understanding of molecular function to a broader evolutionary context. Coupling the experimental strengths of the C. elegans system with the ecological advantages of closely related nematodes should provide a powerful means of understanding both the molecular and evolutionary genetics of quantitative traits.
Collapse
|
20
|
Matzen da Silva J, Creer S, dos Santos A, Costa AC, Cunha MR, Costa FO, Carvalho GR. Systematic and evolutionary insights derived from mtDNA COI barcode diversity in the Decapoda (Crustacea: Malacostraca). PLoS One 2011; 6:e19449. [PMID: 21589909 PMCID: PMC3093375 DOI: 10.1371/journal.pone.0019449] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Accepted: 04/06/2011] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND Decapods are the most recognizable of all crustaceans and comprise a dominant group of benthic invertebrates of the continental shelf and slope, including many species of economic importance. Of the 17635 morphologically described Decapoda species, only 5.4% are represented by COI barcode region sequences. It therefore remains a challenge to compile regional databases that identify and analyse the extent and patterns of decapod diversity throughout the world. METHODOLOGY/PRINCIPAL FINDINGS We contributed 101 decapod species from the North East Atlantic, the Gulf of Cadiz and the Mediterranean Sea, of which 81 species represent novel COI records. Within the newly-generated dataset, 3.6% of the species barcodes conflicted with the assigned morphological taxonomic identification, highlighting both the apparent taxonomic ambiguity among certain groups, and the need for an accelerated and independent taxonomic approach. Using the combined COI barcode projects from the Barcode of Life Database, we provide the most comprehensive COI data set so far examined for the Order (1572 sequences of 528 species, 213 genera, and 67 families). Patterns within families show a general predicted molecular hierarchy, but the scale of divergence at each taxonomic level appears to vary extensively between families. The range values of mean K2P distance observed were: within species 0.285% to 1.375%, within genus 6.376% to 20.924% and within family 11.392% to 25.617%. Nucleotide composition varied greatly across decapods, ranging from 30.8 % to 49.4 % GC content. CONCLUSIONS/SIGNIFICANCE Decapod biological diversity was quantified by identifying putative cryptic species allowing a rapid assessment of taxon diversity in groups that have until now received limited morphological and systematic examination. We highlight taxonomic groups or species with unusual nucleotide composition or evolutionary rates. Such data are relevant to strategies for conservation of existing decapod biodiversity, as well as elucidating the mechanisms and constraints shaping the patterns observed.
Collapse
Affiliation(s)
- Joana Matzen da Silva
- Molecular Ecology and Fisheries Genetics Laboratory, School of Biological Sciences, Environment Centre for Wales, Bangor University, Bangor, Wales, United Kingdom.
| | | | | | | | | | | | | |
Collapse
|
21
|
Klapper M, Ehmke M, Palgunow D, Böhme M, Matthäus C, Bergner G, Dietzek B, Popp J, Döring F. Fluorescence-based fixative and vital staining of lipid droplets in Caenorhabditis elegans reveal fat stores using microscopy and flow cytometry approaches. J Lipid Res 2011; 52:1281-1293. [PMID: 21421847 DOI: 10.1194/jlr.d011940] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The proportions of body fat and fat-free mass are determining factors of adiposity-associated diseases. Work in Caenorhabditis elegans has revealed evolutionarily conserved pathways of fat metabolism. Nevertheless, analysis of body composition and fat distribution in the nematodes has only been partially unraveled because of methodological difficulties. We characterized metabolic C. elegans mutants by using novel and feasible BODIPY 493/503-based fat staining and flow cytometry approaches. Fixative as well as vital BODIPY staining procedures visualize major fat stores, preserve native lipid droplet morphology, and allow quantification of fat content per body volume of individual worms. Colocalization studies using coherent anti-Stokes Raman scattering microscopy, Raman microspectroscopy, and imaging of lysosome-related organelles as well as biochemical measurement confirm our approaches. We found that the fat-to-volume ratio of dietary restriction, TGF-β, and germline mutants are specific for each strain. In contrast, the proportion of fat-free mass is constant between the mutants, although their volumes differ by a factor of 3. Our approaches enable sensitive, accurate, and high-throughput assessment of adiposity in large C. elegans populations at a single-worm level.
Collapse
Affiliation(s)
- Maja Klapper
- Institute of Human Nutrition and Food Science, Research Group Molecular Prevention, University of Kiel, Kiel, Germany
| | - Madeleine Ehmke
- Institute of Human Nutrition and Food Science, Research Group Molecular Prevention, University of Kiel, Kiel, Germany
| | - Daniela Palgunow
- Institute of Human Nutrition and Food Science, Research Group Molecular Prevention, University of Kiel, Kiel, Germany
| | - Mike Böhme
- Institute of Human Nutrition and Food Science, Research Group Molecular Prevention, University of Kiel, Kiel, Germany
| | | | | | | | - Jürgen Popp
- Institute of Photonic Technology, Jena, Germany
| | - Frank Döring
- Institute of Human Nutrition and Food Science, Research Group Molecular Prevention, University of Kiel, Kiel, Germany.
| |
Collapse
|
22
|
Baer CF, Joyner-Matos J, Ostrow D, Grigaltchik V, Salomon MP, Upadhyay A. Rapid decline in fitness of mutation accumulation lines of gonochoristic (outcrossing) Caenorhabditis nematodes. Evolution 2011; 64:3242-53. [PMID: 20649813 DOI: 10.1111/j.1558-5646.2010.01061.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Evolutionary theory predicts that the strength of natural selection to reduce the mutation rate should be stronger in self-fertilizing than in outcrossing taxa. However, the relative efficacy of selection on mutation rate relative to the many other factors influencing the evolution of any species is poorly understood. To address this question, we allowed mutations to accumulate for ∼100 generations in several sets of "mutation accumulation" (MA) lines in three species of gonochoristic (dieocious) Caenorhabditis (C. remanei, C. brenneri, C. sp. 5) as well as in a dioecious strain of the historically self-fertile hermaprohodite C. elegans. In every case, the rate of mutational decay is substantially greater in the gonochoristic taxa than in C. elegans (∼4× greater on average). Residual heterozygosity in the ancestral controls of these MA lines introduces some complications in interpreting the results, but circumstantial evidence suggests the results are not primarily due to inbreeding depression resulting from residual segregating variation. The results suggest that natural selection operates to optimize the mutation rate in Caenorhabditis and that the strength (or efficiency) of selection differs consistently on the basis of mating system, as predicted by theory. However, context-dependent environmental and/or synergistic epistasis could also explain the results.
Collapse
Affiliation(s)
- Charles F Baer
- Department of Biology, University of Florida, Gainesville, Florida 32611-8525, USA.
| | | | | | | | | | | |
Collapse
|
23
|
Braendle C, Baer CF, Félix MA. Bias and evolution of the mutationally accessible phenotypic space in a developmental system. PLoS Genet 2010; 6:e1000877. [PMID: 20300655 PMCID: PMC2837400 DOI: 10.1371/journal.pgen.1000877] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Accepted: 02/08/2010] [Indexed: 11/19/2022] Open
Abstract
Genetic and developmental architecture may bias the mutationally available phenotypic spectrum. Although such asymmetries in the introduction of variation may influence possible evolutionary trajectories, we lack quantitative characterization of biases in mutationally inducible phenotypic variation, their genotype-dependence, and their underlying molecular and developmental causes. Here we quantify the mutationally accessible phenotypic spectrum of the vulval developmental system using mutation accumulation (MA) lines derived from four wild isolates of the nematodes Caenorhabditis elegans and C. briggsae. The results confirm that on average, spontaneous mutations degrade developmental precision, with MA lines showing a low, yet consistently increased, proportion of developmental defects and variants. This result indicates strong purifying selection acting to maintain an invariant vulval phenotype. Both developmental system and genotype significantly bias the spectrum of mutationally inducible phenotypic variants. First, irrespective of genotype, there is a developmental bias, such that certain phenotypic variants are commonly induced by MA, while others are very rarely or never induced. Second, we found that both the degree and spectrum of mutationally accessible phenotypic variation are genotype-dependent. Overall, C. briggsae MA lines exhibited a two-fold higher decline in precision than the C. elegans MA lines. Moreover, the propensity to generate specific developmental variants depended on the genetic background. We show that such genotype-specific developmental biases are likely due to cryptic quantitative variation in activities of underlying molecular cascades. This analysis allowed us to identify the mutationally most sensitive elements of the vulval developmental system, which may indicate axes of potential evolutionary variation. Consistent with this scenario, we found that evolutionary trends in the vulval system concern the phenotypic characters that are most easily affected by mutation. This study provides an empirical assessment of developmental bias and the evolution of mutationally accessible phenotypes and supports the notion that such bias may influence the directions of evolutionary change.
Collapse
|
24
|
Baer CF, Denver DR. Spontaneous mutations decrease sensitivity of gene expression to random environmental variation in Caenorhabditis elegans. PLoS One 2010; 5:e8750. [PMID: 20090917 PMCID: PMC2807463 DOI: 10.1371/journal.pone.0008750] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Accepted: 12/20/2009] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Biological phenotypes are described as "canalized" if they are robust to minor variation of environment and/or genetic background. The existence of a robust phenotype logically implies that some underlying mechanism must be variable, in the sense of "able to vary", in order to compensate for variation in the environment and/or genetic effects. Several lines of evidence lead to the conclusion that deleterious mutations predictably render morphological, developmental, and life-history traits more sensitive to small random environmental perturbations--that is, mutations de-canalize the phenotype. METHODOLOGY/PRINCIPAL FINDINGS Using conventional dye-swap microarray methodology, we compared transcript abundance in a sample of >7,000 genes between four mutation accumulation (MA) lines of the nematode Caenorhabditis elegans and the common (unmutated) ancestor. There was significantly less environmental variance in the MA lines than in the ancestor, both among replicates of the same gene and among genes. CONCLUSIONS/SIGNIFICANCE Deleterious mutations consistently decrease the within-line component of variance in transcript abundance, which is straightforwardly interpreted as reducing the sensitivity of gene expression to small random variation in the environment. This finding is consistent with the idea that underlying variability in gene expression might be mechanistically responsible for phenotypic robustness.
Collapse
Affiliation(s)
- Charles F Baer
- Department of Biology, University of Florida, Gainesville, Florida, United States of America.
| | | |
Collapse
|
25
|
Zhang XS, Hill WG. Change and maintenance of variation in quantitative traits in the context of the Price equation. Theor Popul Biol 2009; 77:14-22. [PMID: 19836408 DOI: 10.1016/j.tpb.2009.10.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Revised: 10/06/2009] [Accepted: 10/12/2009] [Indexed: 11/30/2022]
Abstract
The Price equation is a general description of evolutionary change in any character from one generation to the next due to natural selection and other forces such as mutation and recombination. Recently it has been widely utilised in many fields including quantitative genetics, but these applications have focused mainly on the response to selection in the mean of characters. Many different and, in some cases, conflicting models have been investigated by quantitative geneticists to examine the change and maintenance of both genetic and environmental variance of quantitative traits under selection and other forces. In this study, we use the Price equation to derive many such well-known results for the dynamics and equilibria of variances in a straightforward way and to develop them further.
Collapse
Affiliation(s)
- Xu-Sheng Zhang
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, UK
| | | |
Collapse
|
26
|
Joyner-Matos J, Upadhyay A, Salomon MP, Grigaltchik V, Baer CF. Genetic (Co)variation for life span in rhabditid nematodes: role of mutation, selection, and history. J Gerontol A Biol Sci Med Sci 2009; 64:1134-45. [PMID: 19671885 DOI: 10.1093/gerona/glp112] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The evolutionary mechanisms maintaining genetic variation in life span, particularly post-reproductive life span, are poorly understood. We characterized the effects of spontaneous mutations on life span in the rhabditid nematodes Caenorhabditis elegans and C. briggsae and standing genetic variance for life span and correlation of life span with fitness in C. briggsae. Mutations decreased mean life span, a signature of directional selection. Mutational correlations between life span and fitness were consistently positive. The average selection coefficient against new mutations in C. briggsae was approximately 2% when homozygous. The pattern of phylogeographic variation in life span is inconsistent with global mutation-selection balance (MSB), but MSB appears to hold at the local level. Standing genetic correlations in C. briggsae reflect mutational correlations at a local scale but not at a broad phylogeographic level. At the local scale, results are broadly consistent with predictions of the "mutation accumulation" hypothesis for the evolution of aging.
Collapse
Affiliation(s)
- Joanna Joyner-Matos
- Department of Biology, Eastern Washington University, Cheney, WA 99004-2440, USA.
| | | | | | | | | |
Collapse
|
27
|
Comparing mutational and standing genetic variability for fitness and size in Caenorhabditis briggsae and C. elegans. Genetics 2009; 183:685-92, 1SI-19SI. [PMID: 19667133 DOI: 10.1534/genetics.109.107383] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The genetic variation present in a species depends on the interplay between mutation, population size, and natural selection. At mutation-(purifying) selection balance (MSB) in a large population, the standing genetic variance for a trait (VG) is predicted to be proportional to the mutational variance for the trait (VM); VM is proportional to the mutation rate for the trait. The ratio VM/VG predicts the average strength of selection (S) against a new mutation. Here we compare VM and VG for lifetime reproductive success (approximately fitness) and body volume in two species of self-fertilizing rhabditid nematodes, Caenorhabditis briggsae and C. elegans, which the evidence suggests have different mutation rates. Averaged over traits, species, and populations within species, the relationship between VG and VM is quite stable, consistent with the hypothesis that differences among groups in standing variance can be explained by differences in mutational input. The average (homozygous) selection coefficient inferred from VM/VG is a few percent, smaller than typical direct estimates from mutation accumulation (MA) experiments. With one exception, the variance present in a worldwide sample of these species is similar to the variance present within a sample from a single locale. These results are consistent with specieswide MSB and uniform purifying selection, but genetic draft (hitchhiking) is a plausible alternative possibility.
Collapse
|
28
|
Cutter AD, Dey A, Murray RL. Evolution of the Caenorhabditis elegans genome. Mol Biol Evol 2009; 26:1199-234. [PMID: 19289596 DOI: 10.1093/molbev/msp048] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
A fundamental problem in genome biology is to elucidate the evolutionary forces responsible for generating nonrandom patterns of genome organization. As the first metazoan to benefit from full-genome sequencing, Caenorhabditis elegans has been at the forefront of research in this area. Studies of genomic patterns, and their evolutionary underpinnings, continue to be augmented by the recent push to obtain additional full-genome sequences of related Caenorhabditis taxa. In the near future, we expect to see major advances with the onset of whole-genome resequencing of multiple wild individuals of the same species. In this review, we synthesize many of the important insights to date in our understanding of genome organization and function that derive from the evolutionary principles made explicit by theoretical population genetics and molecular evolution and highlight fertile areas for future research on unanswered questions in C. elegans genome evolution. We call attention to the need for C. elegans researchers to generate and critically assess nonadaptive hypotheses for genomic and developmental patterns, in addition to adaptive scenarios. We also emphasize the potential importance of evolution in the gonochoristic (female and male) ancestors of the androdioecious (hermaphrodite and male) C. elegans as the source for many of its genomic and developmental patterns.
Collapse
Affiliation(s)
- Asher D Cutter
- Department of Ecology & Evolutionary Biology and the Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada.
| | | | | |
Collapse
|
29
|
Phillips N, Salomon M, Custer A, Ostrow D, Baer CF. Spontaneous mutational and standing genetic (co)variation at dinucleotide microsatellites in Caenorhabditis briggsae and Caenorhabditis elegans. Mol Biol Evol 2008; 26:659-69. [PMID: 19109257 DOI: 10.1093/molbev/msn287] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Understanding the evolutionary processes responsible for shaping genetic variation within and between species requires separating the effects of mutation and selection. Differences between the patterns of genetic variation observed in nature and when mutations are allowed to accumulate in the relative absence of selection can reveal biases imposed by selection. We characterize the genetic variation at dinucleotide microsatellite repeats in four sets of 250-generation mutation accumulation (MA) lines, two in the species Caenorhabditis briggsae and two in Caenorhabditis elegans, and compare the mutational variation with the standing variation in those species. We also compare the mutational properties of microsatellites with the cumulative effects of mutations on fitness in the same lines. Integrated over the whole genome, we infer that the mutation rate of C. briggsae is about twice that of C. elegans, consistent with the cumulative mutational effects on fitness. The mutational spectrum (ratio of insertions to deletions) differs between repeat types and, in some cases, between species. The per-locus mutation rate is significantly positively correlated with the standing genetic variation at the same locus in both species, providing justification for the common practice of using the standing genetic variance as a surrogate for the mutation rate.
Collapse
|
30
|
The anomalous effects of biased mutation revisited: mean-optimum deviation and apparent directional selection under stabilizing selection. Genetics 2008; 179:1135-41. [PMID: 18558659 DOI: 10.1534/genetics.107.083428] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Empirical evidence indicates that the distribution of the effects of mutations on quantitative traits is not symmetric about zero. Under stabilizing selection in infinite populations with normally distributed mutant effects having a nonzero mean, Waxman and Peck showed that the deviation of the population mean from the optimum is expected to be small. We show by simulation that genetic drift, leptokurtosis of mutational effects, and pleiotropy can increase the mean-optimum deviation greatly, however, and that the apparent directional selection thereby caused can be substantial.
Collapse
|
31
|
Abstract
The evolution of canalization, the robustness of the phenotype to environmental or genetic perturbation, has attracted considerable recent interest. A key step toward understanding the evolution of any phenotype is characterizing the rate at which mutation introduces genetic variation for the trait (the mutational variance, V(M)) and the average directional effects of mutations on the trait mean (DeltaM). In this study, the mutational parameters for canalization of productivity and body volume are quantified in two sets of mutation accumulation lines of nematodes in the genus Caenorhabditis and are compared with the mutational parameters for the traits themselves. Four results emerge: (1) spontaneous mutations consistently decanalize the phenotype; (2) the mutational parameters for decanalization, V(M) (quantified as mutational heritability) and DeltaM, are of the same order of magnitude as the same parameters for the traits themselves; (3) the mutational parameters for canalization are roughly correlated with the parameters for the traits themselves across taxa; and (4) there is no evidence that residual segregating overdominant loci contribute to the decay of canalization. These results suggest that canalization is readily evolvable and that any evolutionary factor that causes mutations to accumulate will, on average, decanalize the phenotype.
Collapse
Affiliation(s)
- Charles F Baer
- Department of Zoology, University of Florida Genetics Institute, PO Box 118525, Gainesville, Florida 32611, USA.
| |
Collapse
|