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Ye Z, Wei W, Pfrender ME, Lynch M. Evolutionary Insights from a Large-Scale Survey of Population-Genomic Variation. Mol Biol Evol 2023; 40:msad233. [PMID: 37863047 PMCID: PMC10630549 DOI: 10.1093/molbev/msad233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 09/11/2023] [Accepted: 10/03/2023] [Indexed: 10/22/2023] Open
Abstract
The field of genomics has ushered in new methods for studying molecular-genetic variation in natural populations. However, most population-genomic studies still rely on small sample sizes (typically, <100 individuals) from single time points, leaving considerable uncertainties with respect to the behavior of relatively young (and rare) alleles and, owing to the large sampling variance of measures of variation, to the specific gene targets of unusually strong selection. Genomic sequences of ∼1,700 haplotypes distributed over a 10-year period from a natural population of the microcrustacean Daphnia pulex reveal evolutionary-genomic features at a refined scale, including previously hidden information on the behavior of rare alleles predicted by recent theory. Background selection, resulting from the recurrent introduction of deleterious alleles, appears to strongly influence the dynamics of neutral alleles, inducing indirect negative selection on rare variants and positive selection on common variants. Temporally fluctuating selection increases the persistence of nonsynonymous alleles with intermediate frequencies, while reducing standing levels of variation at linked silent sites. Combined with the results from an equally large metapopulation survey of the study species, classes of genes that are under strong positive selection can now be confidently identified in this key model organism. Most notable among rapidly evolving Daphnia genes are those associated with ribosomes, mitochondrial functions, sensory systems, and lifespan determination.
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Affiliation(s)
- Zhiqiang Ye
- Hubei Key Laboratory of Genetic Regulation & Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Wen Wei
- Biodesign Center for Mechanisms of Evolution, Arizona State University, Tempe, AZ 85287, USA
| | - Michael E Pfrender
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Michael Lynch
- Biodesign Center for Mechanisms of Evolution, Arizona State University, Tempe, AZ 85287, USA
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2
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Mukherjee A, Hossain Z, Erben E, Ma S, Choi JY, Kim HS. Identification of a small-molecule inhibitor that selectively blocks DNA-binding by Trypanosoma brucei replication protein A1. Nat Commun 2023; 14:4390. [PMID: 37474515 PMCID: PMC10359466 DOI: 10.1038/s41467-023-39839-x] [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: 10/12/2022] [Accepted: 06/30/2023] [Indexed: 07/22/2023] Open
Abstract
Replication Protein A (RPA) is a broadly conserved complex comprised of the RPA1, 2 and 3 subunits. RPA protects the exposed single-stranded DNA (ssDNA) during DNA replication and repair. Using structural modeling, we discover an inhibitor, JC-229, that targets RPA1 in Trypanosoma brucei, the causative parasite of African trypanosomiasis. The inhibitor is highly toxic to T. brucei cells, while mildly toxic to human cells. JC-229 treatment mimics the effects of TbRPA1 depletion, including DNA replication inhibition and DNA damage accumulation. In-vitro ssDNA-binding assays demonstrate that JC-229 inhibits the activity of TbRPA1, but not the human ortholog. Indeed, despite the high sequence identity with T. cruzi and Leishmania RPA1, JC-229 only impacts the ssDNA-binding activity of TbRPA1. Site-directed mutagenesis confirms that the DNA-Binding Domain A (DBD-A) in TbRPA1 contains a JC-229 binding pocket. Residue Serine 105 determines specific binding and inhibition of TbRPA1 but not T. cruzi and Leishmania RPA1. Our data suggest a path toward developing and testing highly specific inhibitors for the treatment of African trypanosomiasis.
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Affiliation(s)
- Aditi Mukherjee
- Public Health Research Institute, Rutgers Biomedical Health Sciences, Newark, NJ, 07103, USA
| | - Zakir Hossain
- Department of Chemistry and Biochemistry, Queens College, New York, NY, 11367, USA
| | - Esteban Erben
- Instituto de Investigaciones Biotecnológicas, Universidad Nacional de San Martín (UNSAM) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Martín, Provincia de Buenos Aires, Argentina
- Escuela de Bio y Nanotecnologías (EByN), Universidad Nacional de San Martín, San Martín, Provincia de Buenos Aires, Argentina
| | - Shuai Ma
- Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA
| | - Jun Yong Choi
- Department of Chemistry and Biochemistry, Queens College, New York, NY, 11367, USA.
- Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA.
- Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY, 10016, USA.
| | - Hee-Sook Kim
- Public Health Research Institute, Rutgers Biomedical Health Sciences, Newark, NJ, 07103, USA.
- Department of Microbiology, Biochemistry, and Molecular Genetics, New Jersey Medical School, Rutgers Biomedical Health Sciences, Newark, NJ, 07103, USA.
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3
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Ye Z, Wei W, Pfrender M, Lynch M. Evolutionary Insights from a Large-scale Survey of Population-genomic Variation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.03.539276. [PMID: 37205430 PMCID: PMC10187179 DOI: 10.1101/2023.05.03.539276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Results from data on > 1000 haplotypes distributed over a nine-year period from a natural population of the microcrustacean Daphnia pulex reveal evolutionary-genomic features at a refined scale, including key population-genetic properties that are obscured in studies with smaller sample sizes. Background selection, resulting from the recurrent introduction of deleterious alleles, appears to strongly influence the dynamics of neutral alleles, inducing indirect negative selection on rare variants and positive selection on common variants. Fluctuating selection increases the persistence of nonsynonymous alleles with intermediate frequencies, while reducing standing levels of variation at linked silent sites. Combined with the results from an equally large metapopulation survey of the study species, regions of gene structure that are under strong purifying selection and classes of genes that are under strong positive selection in this key species can be confidently identified. Most notable among rapidly evolving Daphnia genes are those associated with ribosomes, mitochondrial functions, sensory systems, and lifespan determination.
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Affiliation(s)
- Zhiqiang Ye
- Biodesign Center for Mechanisms of Evolution, Arizona State University, Tempe, AZ 85287
| | - Wen Wei
- Biodesign Center for Mechanisms of Evolution, Arizona State University, Tempe, AZ 85287
| | - Michael Pfrender
- Department of Biological Sciences, Notre Dame University, Notre Dame, IN 46556
| | - Michael Lynch
- Biodesign Center for Mechanisms of Evolution, Arizona State University, Tempe, AZ 85287
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4
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Kilwanila SI, Lyimo CM, Rija AA. Mitochondrial genetic diversity of the Greater Cane rat (Thryonomys swinderianus) populations from the Eastern Arc Mountains ecosystem, Tanzania. Mol Biol Rep 2022; 49:10431-10442. [DOI: 10.1007/s11033-022-07823-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 07/26/2022] [Indexed: 11/24/2022]
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5
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Baldwin JW, Garcia-Porta J, Botero CA. Phenotypic responses to climate change are significantly dampened in big-brained birds. Ecol Lett 2022; 25:939-947. [PMID: 35142006 DOI: 10.1111/ele.13971] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 11/03/2021] [Accepted: 01/05/2022] [Indexed: 01/29/2023]
Abstract
Anthropogenic climate change is rapidly altering local environments and threatening biodiversity throughout the world. Although many wildlife responses to this phenomenon appear largely idiosyncratic, a wealth of basic research on this topic is enabling the identification of general patterns across taxa. Here, we expand those efforts by investigating how avian responses to climate change are affected by the ability to cope with ecological variation through behavioural flexibility (as measured by relative brain size). After accounting for the effects of phylogenetic uncertainty and interspecific variation in adaptive potential, we confirm that although climate warming is generally correlated with major body size reductions in North American migrants, these responses are significantly weaker in species with larger relative brain sizes. Our findings suggest that cognition can play an important role in organismal responses to global change by actively buffering individuals from the environmental effects of warming temperatures.
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Affiliation(s)
- Justin W Baldwin
- Department of Biology, Washington University, St. Louis, Missouri, USA
| | - Joan Garcia-Porta
- Department of Biology, Washington University, St. Louis, Missouri, USA
| | - Carlos A Botero
- Department of Biology, Washington University, St. Louis, Missouri, USA
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6
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Ho EKH, Macrae F, Latta LC, McIlroy P, Ebert D, Fields PD, Benner MJ, Schaack S. High and Highly Variable Spontaneous Mutation Rates in Daphnia. Mol Biol Evol 2021; 37:3258-3266. [PMID: 32520985 PMCID: PMC7820357 DOI: 10.1093/molbev/msaa142] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The rate and spectrum of spontaneous mutations are critical parameters in basic and applied biology because they dictate the pace and character of genetic variation introduced into populations, which is a prerequisite for evolution. We use a mutation–accumulation approach to estimate mutation parameters from whole-genome sequence data from multiple genotypes from multiple populations of Daphnia magna, an ecological and evolutionary model system. We report extremely high base substitution mutation rates (µ-n,bs = 8.96 × 10−9/bp/generation [95% CI: 6.66–11.97 × 10−9/bp/generation] in the nuclear genome and µ-m,bs = 8.7 × 10−7/bp/generation [95% CI: 4.40–15.12 × 10−7/bp/generation] in the mtDNA), the highest of any eukaryote examined using this approach. Levels of intraspecific variation based on the range of estimates from the nine genotypes collected from three populations (Finland, Germany, and Israel) span 1 and 3 orders of magnitude, respectively, resulting in up to a ∼300-fold difference in rates among genomic partitions within the same lineage. In contrast, mutation spectra exhibit very consistent patterns across genotypes and populations, suggesting the mechanisms underlying the mutational process may be similar, even when the rates at which they occur differ. We discuss the implications of high levels of intraspecific variation in rates, the importance of estimating gene conversion rates using a mutation–accumulation approach, and the interacting factors influencing the evolution of mutation parameters. Our findings deepen our knowledge about mutation and provide both challenges to and support for current theories aimed at explaining the evolution of the mutation rate, as a trait, across taxa.
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Affiliation(s)
- Eddie K H Ho
- Department of Biology, Reed College, Portland, OR
| | | | - Leigh C Latta
- Department of Biology, Reed College, Portland, OR.,Division of Natural Sciences and Mathematics, Lewis-Clark State College, Lewiston, ID
| | | | - Dieter Ebert
- Department of Environmental Sciences, Zoology, University of Basel, Basel, Switzerland
| | - Peter D Fields
- Department of Environmental Sciences, Zoology, University of Basel, Basel, Switzerland
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7
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Davenport ES, Agrelius TC, Harmon KB, Dudycha JL. Fitness effects of spontaneous mutations in a warming world. Evolution 2021; 75:1513-1524. [PMID: 33751559 PMCID: PMC8252619 DOI: 10.1111/evo.14208] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 02/09/2021] [Accepted: 02/16/2021] [Indexed: 12/14/2022]
Abstract
Spontaneous mutations fuel evolutionary processes and differ in consequence, but the consequences depend on the environment. Biophysical considerations of protein thermostability predict that warm temperatures may systematically increase the deleteriousness of mutation. We sought to test whether mutation reduced fitness more when measured in an environment that reflected climate change projections for temperature. We investigated the effects of spontaneous mutations on life history, size, and fitness in 21 mutation accumulation lines and 12 control lines of Daphnia pulex at standard and elevated (+4℃) temperatures. Warmer temperature accelerated life history and reduced body length and clutch sizes. Mutation led to reduced mean clutch sizes and fitness estimates at both temperatures. We found no evidence of a systematic temperature–mutation interaction on trait means, although some lines showed evidence of beneficial mutation at one temperature and deleterious mutation at the other. However, trait variances are also influenced by mutation, and we observed increased variances due to mutation for most traits. For variance of the intrinsic rate of increase and some reproductive traits, we found significant temperature–mutation interactions, with a larger increase due to mutation in the warmer environment. This suggests that selection on new mutations will be more efficient at elevated temperatures.
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Affiliation(s)
- Elizabeth S Davenport
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina, 29208.,Department of Ecology & Evolutionary Biology, University of Michigan, Ann Arbor, Michigan, 48109
| | - Trenton C Agrelius
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina, 29208
| | - Krista B Harmon
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina, 29208
| | - Jeffry L Dudycha
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina, 29208
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8
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Fitness and Genomic Consequences of Chronic Exposure to Low Levels of Copper and Nickel in Daphnia pulex Mutation Accumulation Lines. G3-GENES GENOMES GENETICS 2019; 9:61-71. [PMID: 30389796 PMCID: PMC6325897 DOI: 10.1534/g3.118.200797] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In at least some unicellular organisms, mutation rates are temporarily raised upon exposure to environmental stress, potentially contributing to the evolutionary response to stress. Whether this is true for multicellular organisms, however, has received little attention. This study investigated the effects of chronic mild stress, in the form of low-level copper and nickel exposure, on mutational processes in Daphnia pulex using a combination of mutation accumulation, whole genome sequencing and life-history assays. After over 100 generations of mutation accumulation, we found no effects of metal exposure on the rates of single nucleotide mutations and of loss of heterozygosity events, the two mutation classes that occurred in sufficient numbers to allow statistical analysis. Similarly, rates of decline in fitness, as measured by intrinsic rate of population increase and of body size at first reproduction, were negligibly affected by metal exposure. We can reject the possibility that Daphnia were insufficiently stressed to invoke genetic responses as we have previously shown rates of large-scale deletions and duplications are elevated under metal exposure in this experiment. Overall, the mutation accumulation lines did not significantly depart from initial values for phenotypic traits measured, indicating the lineage used was broadly mutationally robust. Taken together, these results indicate that the mutagenic effects of chronic low-level exposure to these metals are restricted to certain mutation classes and that fitness consequences are likely minor and therefore unlikely to be relevant in determining the evolutionary responses of populations exposed to these stressors.
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9
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Hintz WD, Jones DK, Relyea RA. Evolved tolerance to freshwater salinization in zooplankton: life-history trade-offs, cross-tolerance and reducing cascading effects. Philos Trans R Soc Lond B Biol Sci 2018; 374:rstb.2018.0012. [PMID: 30509914 DOI: 10.1098/rstb.2018.0012] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/24/2018] [Indexed: 12/22/2022] Open
Abstract
Recent discoveries have documented evolutionary responses to freshwater salinization. We investigated if evolutionary responses to salinization exhibit life-history trade-offs or if they can mitigate ecological impacts such as cascading effects through mechanisms of tolerance and cross-tolerance. We conducted an outdoor mesocosm experiment using populations of Daphnia pulex-a ubiquitous algal grazer-that were either naive or had previously experienced selection to become more tolerant to sodium chloride (NaCl). During the initial phase of population growth, we discovered that evolved tolerance comes at the cost of slower population growth in the absence of salt. We found evolved Daphnia populations maintained a tolerance to NaCl approximately 30 generations after the initial discovery. Evolved tolerance to NaCl also conferred cross-tolerance to a high concentration of CaCl2 (3559 µS cm-1) and a moderate concentration of MgCl2 (967 µS cm-1). A higher concentration of MgCl2 (2188 µS cm-1) overwhelmed the cross-tolerance and killed all Daphnia Tolerance to NaCl did not mitigate NaCl-induced cascades leading to phytoplankton blooms, but cross-tolerance at moderate concentrations of MgCl2 and high concentrations of CaCl2 mitigated such cascading effects caused by these two salts. These discoveries highlight the important interplay between ecology and evolution in understanding the full impacts of freshwater salinization.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.
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Affiliation(s)
- William D Hintz
- Darrin Fresh Water Institute, Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Devin K Jones
- Darrin Fresh Water Institute, Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | - Rick A Relyea
- Darrin Fresh Water Institute, Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
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10
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Abstract
Understanding the context-dependence of spontaneous mutations is crucial to predicting evolutionary trajectories. In this experiment, the impact of genetic background and trait-type on mutational susceptibility was investigated. Mutant and non-mutant lines of six unique genotypes from two populations of Daphnia magna were phenotypically assayed using a common-garden experiment. Morphological, life-history, and behavioral traits were measured and estimates of the mutation parameters were generated. The mutation parameters varied between the populations and among genotypes, suggesting differential susceptibility to mutation depending upon genomic background. Traits also varied in their susceptibility to mutation with behavioral traits evolving more rapidly than life-history and morphological traits. These results may reflect the unique selection histories of these populations.
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11
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Thomas GWC, Wang RJ, Puri A, Harris RA, Raveendran M, Hughes DST, Murali SC, Williams LE, Doddapaneni H, Muzny DM, Gibbs RA, Abee CR, Galinski MR, Worley KC, Rogers J, Radivojac P, Hahn MW. Reproductive Longevity Predicts Mutation Rates in Primates. Curr Biol 2018; 28:3193-3197.e5. [PMID: 30270182 DOI: 10.1016/j.cub.2018.08.050] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 07/26/2018] [Accepted: 08/22/2018] [Indexed: 12/30/2022]
Abstract
Mutation rates vary between species across several orders of magnitude, with larger organisms having the highest per-generation mutation rates. Hypotheses for this pattern typically invoke physiological or population-genetic constraints imposed on the molecular machinery preventing mutations [1]. However, continuing germline cell division in multicellular eukaryotes means that organisms with longer generation times and of larger size will leave more mutations to their offspring simply as a byproduct of their increased lifespan [2, 3]. Here, we deeply sequence the genomes of 30 owl monkeys (Aotus nancymaae) from six multi-generation pedigrees to demonstrate that paternal age is the major factor determining the number of de novo mutations in this species. We find that owl monkeys have an average mutation rate of 0.81 × 10-8 per site per generation, roughly 32% lower than the estimate in humans. Based on a simple model of reproductive longevity that does not require any changes to the mutational machinery, we show that this is the expected mutation rate in owl monkeys. We further demonstrate that our model predicts species-specific mutation rates in other primates, including study-specific mutation rates in humans based on the average paternal age. Our results suggest that variation in life history traits alone can explain variation in the per-generation mutation rate among primates, and perhaps among a wide range of multicellular organisms.
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Affiliation(s)
- Gregg W C Thomas
- Department of Biology, Indiana University, 107 S. Indiana Avenue, Bloomington, IN 47405, USA; Department of Computer Science, Indiana University, 107 S. Indiana Avenue, Bloomington, IN 47405, USA.
| | - Richard J Wang
- Department of Biology, Indiana University, 107 S. Indiana Avenue, Bloomington, IN 47405, USA
| | - Arthi Puri
- Department of Computer Science, Indiana University, 107 S. Indiana Avenue, Bloomington, IN 47405, USA
| | - R Alan Harris
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA
| | - Muthuswamy Raveendran
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA
| | - Daniel S T Hughes
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA
| | - Shwetha C Murali
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA
| | - Lawrence E Williams
- Keeling Center for Comparative Medicine and Research, University of Texas, MD Anderson Cancer Center, 650 Cool Water Drive, Bastrop, TX 78602, USA
| | - Harsha Doddapaneni
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA
| | - Donna M Muzny
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA
| | - Richard A Gibbs
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA
| | - Christian R Abee
- Keeling Center for Comparative Medicine and Research, University of Texas, MD Anderson Cancer Center, 650 Cool Water Drive, Bastrop, TX 78602, USA
| | - Mary R Galinski
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, 201 Dowman Drive, Atlanta, GA, USA; Division of Infectious Diseases, Department of Medicine, Emory University, 201 Dowman Drive, Atlanta, GA, USA
| | - Kim C Worley
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA
| | - Jeffrey Rogers
- Human Genome Sequencing Center, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA
| | - Predrag Radivojac
- Department of Computer Science, Indiana University, 107 S. Indiana Avenue, Bloomington, IN 47405, USA
| | - Matthew W Hahn
- Department of Biology, Indiana University, 107 S. Indiana Avenue, Bloomington, IN 47405, USA; Department of Computer Science, Indiana University, 107 S. Indiana Avenue, Bloomington, IN 47405, USA.
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12
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Flynn JM, Chain FJ, Schoen DJ, Cristescu ME. Spontaneous Mutation Accumulation inDaphnia pulexin Selection-Free vs. Competitive Environments. Mol Biol Evol 2016; 34:160-173. [DOI: 10.1093/molbev/msw234] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
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13
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Braverman JM, Hamilton MB, Johnson BA. Patterns of Substitution Rate Variation at Many Nuclear Loci in Two Species Trios in the Brassicaceae Partitioned with ANOVA. J Mol Evol 2016; 83:97-109. [PMID: 27592229 DOI: 10.1007/s00239-016-9752-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 07/14/2016] [Indexed: 01/09/2023]
Abstract
There are marked variations among loci and among lineages in rates of nucleotide substitution. The generation time hypothesis (GTH) is a neutral explanation for substitution rate heterogeneity that has genomewide application, predicting that species with shorter generation times accumulate DNA sequence substitutions faster than species with longer generation times do since faster genome replication provides more opportunities for mutations to occur and reach fixation by genetic drift. Relatively few studies have rigorously evaluated the GTH in plants, and there are numerous alternative hypotheses for plant substitution rate variation. One major challenge has been finding pairs of closely related plant species with contrasting generation times and appropriate outgroup taxa that all also have DNA sequence data for numerous loci. To test for causes of rate variation, we obtained sequence data for 256 genes for Arabidopsis thaliana, normally reproducing every year, and the biennial Arabidopsis lyrata with three closely related outgroup taxa (Brassica rapa, Capsella grandiflora, and Neslia paniculata) as well as the biennial Brassica oleracea and the annual B. rapa lineage with the outgroup N. paniculata. A sign test indicated that more loci than expected by chance have faster rates of substitution on the branch leading to the annual than to the perennial for one three-species trio but not another. Tajima's 1D and 2D tests, and a likelihood ratio test that incorporated saturation correction, rejected rate homogeneity for up to 26 genes (up to 14 genes when correcting for multiple tests), consistently showing faster rates for the annual lineage in the Arabidopsis species trio. ANOVA showed significant rate heterogeneity between the Arabidopsis and Brassica species trios (about 6 % of rate variation) and among loci (about 26-32 % of rate variation). The lineage-by-locus interaction which would be caused by locus- and lineage-specific natural selection explained about 13 % of substitution rate variation in one ANOVA model using substitution rates from genes partitioned into odd and even codons but was not a significant effect without partitioned genes. Annual/perennial lineage and species trio by annual/perennial lineage each explained about 1 % of substitution rate variation.
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Affiliation(s)
- John M Braverman
- Department of Biology, Saint Joseph's University, Philadelphia, PA, USA.
| | | | - Brent A Johnson
- Department of Biostatistics and Computational Biology, University of Rochester, Rochester, NY, USA
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14
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Hodgins-Davis A, Rice DP, Townsend JP. Gene Expression Evolves under a House-of-Cards Model of Stabilizing Selection. Mol Biol Evol 2015; 32:2130-40. [PMID: 25901014 PMCID: PMC4592357 DOI: 10.1093/molbev/msv094] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Divergence in gene regulation is hypothesized to underlie much of phenotypic evolution, but the role of natural selection in shaping the molecular phenotype of gene expression continues to be debated. To resolve the mode of gene expression, evolution requires accessible theoretical predictions for the effect of selection over long timescales. Evolutionary quantitative genetic models of phenotypic evolution can provide such predictions, yet those predictions depend on the underlying hypotheses about the distributions of mutational and selective effects that are notoriously difficult to disentangle. Here, we draw on diverse genomic data sets including expression profiles of natural genetic variation and mutation accumulation lines, empirical estimates of genomic mutation rates, and inferences of genetic architecture to differentiate contrasting hypotheses for the roles of stabilizing selection and mutation in shaping natural expression variation. Our analysis suggests that gene expression evolves in a domain of phenotype space well fit by the House-of-Cards (HC) model. Although the strength of selection inferred is sensitive to the number of loci controlling gene expression, the model is not. The consistency of these results across evolutionary time from budding yeast through fruit fly implies that this model is general and that mutational effects on gene expression are relatively large. Empirical estimates of the genetic architecture of gene expression traits imply that selection provides modest constraints on gene expression levels for most genes, but that the potential for regulatory evolution is high. Our prediction using data from laboratory environments should encourage the collection of additional data sets allowing for more nuanced parameterizations of HC models for gene expression.
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Affiliation(s)
- Andrea Hodgins-Davis
- Department of Ecology and Evolutionary Biology, Yale University Department of Biostatistics, School of Public Health, Yale University
| | - Daniel P Rice
- Department of Ecology and Evolutionary Biology, Yale University Department of Organismic and Evolutionary Biology, Harvard University
| | - Jeffrey P Townsend
- Department of Ecology and Evolutionary Biology, Yale University Department of Biostatistics, School of Public Health, Yale University Program in Computational Biology and Bioinformatics, Yale University
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15
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Latta LC, Peacock M, Civitello DJ, Dudycha JL, Meik JM, Schaack S. The phenotypic effects of spontaneous mutations in different environments. Am Nat 2015; 185:243-52. [PMID: 25616142 DOI: 10.1086/679501] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Understanding the context dependence of mutation represents the current frontier of mutation research. In particular, understanding how traits vary in their abilities to accrue mutational variation and how the environment influences expression of mutant phenotypes yields insight into evolutionary processes. We conducted phenotypic assays in four environments using a set of Daphnia pulex mutation accumulation lines to examine the context dependence of mutation. Life-history traits accrued mutational variance faster than morphological traits when considered in individual environments. Across environments, the mutational variance in plasticity was also greater for life-history traits than for morphological traits, although this pattern was less robust. In addition, the expression of mutational variance depended on the environment, which resulted in changes in the rank order of genotype performance across environments in some cases. Such cryptic genetic variation resulting from mutation may maintain genetic diversity and allow for rapid adaptation in spatially or temporally variable environments.
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Affiliation(s)
- Leigh C Latta
- Department of Biology, Reed College, Portland, Oregon 97202
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Abstract
Substitution rates vary between species, and many explanations regarding the causes of this variation have been proposed. Here we consider how new genomic data on the per-generation mutation rate impinge on proposed hypotheses for substitution rate variation in primates. We propose that the generation-time effect as it is usually understood cannot explain the observed rate variation, but instead that selection for decreased somatic mutation rates can. By considering the disparate causes underlying mutation rate changes in recent human history, we also show that the per-generation mutation rate is increasing even as the per-cell-division rate is decreasing.
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Tucker AE, Ackerman MS, Eads BD, Xu S, Lynch M. Population-genomic insights into the evolutionary origin and fate of obligately asexual Daphnia pulex. Proc Natl Acad Sci U S A 2013; 110:15740-5. [PMID: 23959868 PMCID: PMC3785735 DOI: 10.1073/pnas.1313388110] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Despite much theoretical work, the molecular-genetic causes and evolutionary consequences of asexuality remain largely undetermined. Asexual animal species are rare, evolutionarily short-lived, and thought to suffer mutational meltdown as a result of lack of recombination. Whole-genome analysis of 11 sexual and 11 asexual genotypes of Daphnia pulex indicates that current asexual lineages are in fact very young, exhibit no signs of purifying selection against accumulating mutations, and have extremely high rates of gene conversion and deletion. The reconstruction of chromosomal haplotypes in regions containing SNP markers associated with asexuality (chromosomes VIII and IX) indicates that introgression from a sister species, Daphnia pulicaria, underlies the origin of the asexual phenotype. Silent-site divergence of the shared chromosomal haplotypes of asexuals indicates that the spread of asexuality is as recent as 1,250 y, although the origin of the meiosis-suppressing element or elements could be substantially older. In addition, using previous estimates of the gene conversion rate from Daphnia mutation accumulation lines, we are able to age each asexual lineage. Although asexual lineages originate from wide crosses that introduce elevated individual heterozygosities on clone foundation, they also appear to be constrained by the inbreeding-like effect of loss of heterozygosity that accrues as gene conversion and hemizygous deletion expose preexisting recessive deleterious alleles of asexuals, limiting their evolutionary longevity. Our study implies that the buildup of newly introduced deleterious mutations (i.e., Muller's ratchet) may not be the dominant force imperiling nonrecombining populations of D. pulex, as previously proposed.
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Affiliation(s)
| | | | - Brian D. Eads
- Department of Biology, Indiana University, Bloomington, IN 47405
| | - Sen Xu
- Department of Biology, Indiana University, Bloomington, IN 47405
| | - Michael Lynch
- Department of Biology, Indiana University, Bloomington, IN 47405
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