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Collins KM, Howansky E, Macon-Foley SC, Adonay ME, Shankar V, Lyman RF, Nazario-Yepiz NO, Brooks JK, Lyman RA, Mackay TFC, Anholt RRH. Drosophila Toxicogenomics: genetic variation and sexual dimorphism in susceptibility to 4-Methylimidazole. Hum Genomics 2024; 18:119. [PMID: 39497218 PMCID: PMC11533318 DOI: 10.1186/s40246-024-00689-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2024] [Accepted: 10/24/2024] [Indexed: 11/07/2024] Open
Abstract
BACKGROUND 4-methylimidazole is a ubiquitous and potentially carcinogenic environmental toxicant. Genetic factors that contribute to variation in susceptibility to its toxic effects are challenging to assess in human populations. We used the Drosophila melanogaster Genetic Reference Panel (DGRP), a living library of natural genetic variation, to identify genes with human orthologs associated with variation in susceptibility to 4-methylimidazole. RESULTS We screened 204 DGRP lines for survival following 24-hour exposure to 4-methylimidazole. We found extensive genetic variation for survival, with a broad sense heritability of 0.82; as well as genetic variation in sexual dimorphism, with a cross-sex genetic correlation of 0.59. Genome-wide association analyses identified a total of 241 candidate molecular polymorphisms in or near 273 unique genes associated with survival. These polymorphisms had either sex-specific or sex-antagonistic effects, and most had putative regulatory effects. We generated interaction networks using these candidate genes as inputs and computationally recruited genes with known physical or genetic interactions. The network genes were significantly over-represented for gene ontology terms involving all aspects of development (including nervous system development) and cellular and organismal functions as well as canonical signaling pathways, and most had human orthologs. CONCLUSIONS The genetic basis of variation in sensitivity to acute exposure to 4-methylimidazole in Drosophila is attributable to variation in genes and networks of genes known for their effects on multiple developmental and cellular processes, including possible neurotoxicity. Given evolutionary conservation of the underlying genes and pathways, these insights may be applicable to humans.
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Affiliation(s)
- Katelynne M Collins
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, SC, 29646, USA
| | - Elisabeth Howansky
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, SC, 29646, USA
| | - Sarah C Macon-Foley
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, SC, 29646, USA
| | - Maria E Adonay
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, SC, 29646, USA
| | - Vijay Shankar
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, SC, 29646, USA
| | - Richard F Lyman
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, SC, 29646, USA
| | - Nestor Octavio Nazario-Yepiz
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, SC, 29646, USA
| | - Jordyn K Brooks
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, SC, 29646, USA
| | - Rachel A Lyman
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, SC, 29646, USA
| | - Trudy F C Mackay
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, SC, 29646, USA.
| | - Robert R H Anholt
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, SC, 29646, USA.
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Yamamoto A, Huang W, Carbone MA, Anholt RRH, Mackay TFC. The genetic basis of incipient sexual isolation in Drosophila melanogaster. Proc Biol Sci 2024; 291:20240672. [PMID: 39045689 PMCID: PMC11267472 DOI: 10.1098/rspb.2024.0672] [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: 03/21/2024] [Revised: 05/15/2024] [Accepted: 06/05/2024] [Indexed: 07/25/2024] Open
Abstract
Speciation is a fundamental evolutionary process but the genetic changes accompanying speciation are difficult to determine since true species do not produce viable and fertile offspring. Partially reproductively isolated incipient species are useful for assessing genetic changes that occur prior to speciation. Drosophila melanogaster from Zimbabwe, Africa are partially sexually isolated from other D. melanogaster populations whose males have poor mating success with Zimbabwe females. We used the North American D. melanogaster Genetic Reference Panel (DGRP) to show that there is significant genetic variation in mating success of DGRP males with Zimbabwe females, to map genetic variants and genes associated with variation in mating success and to determine whether mating success to Zimbabwe females is associated with other quantitative traits previously measured in the DGRP. Incipient sexual isolation is highly polygenic and associated with the common African inversion In(3R)K and the amount of the sex pheromone 5,9-heptacosadiene in DGRP females. We functionally validated the effect of eight candidate genes using RNA interference to provide testable hypotheses for future studies investigating the molecular genetic basis of incipient sexual isolation in D. melanogaster.
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Affiliation(s)
- Akihiko Yamamoto
- Program in Genetics, W. M. Keck Center for Behavioral Biology and Department of Biological Sciences, North Carolina State University, Raleigh NC, Raleigh, NC27695-7614, USA
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC, USA
| | - Wen Huang
- Program in Genetics, W. M. Keck Center for Behavioral Biology and Department of Biological Sciences, North Carolina State University, Raleigh NC, Raleigh, NC27695-7614, USA
- Department of Animal Science, Michigan State University, 474 S Shaw Lane, East Lansing, MI, USA
| | - Mary Anna Carbone
- Program in Genetics, W. M. Keck Center for Behavioral Biology and Department of Biological Sciences, North Carolina State University, Raleigh NC, Raleigh, NC27695-7614, USA
- Center for Fungal Research and Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, USA
| | - Robert R. H. Anholt
- Program in Genetics, W. M. Keck Center for Behavioral Biology and Department of Biological Sciences, North Carolina State University, Raleigh NC, Raleigh, NC27695-7614, USA
- Center for Human Genetics and Department of Genetics and Biochemistry, Clemson University, 114 Gregor Mendel Circle, Greenwood, SC, USA
| | - Trudy F. C. Mackay
- Program in Genetics, W. M. Keck Center for Behavioral Biology and Department of Biological Sciences, North Carolina State University, Raleigh NC, Raleigh, NC27695-7614, USA
- Center for Human Genetics and Department of Genetics and Biochemistry, Clemson University, 114 Gregor Mendel Circle, Greenwood, SC, USA
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Lyman RF, Lyman RA, Yamamoto A, Huang W, Harbison ST, Zhou S, Anholt RRH, Mackay TFC. Natural genetic variation in a dopamine receptor is associated with variation in female fertility in Drosophila melanogaster. Proc Biol Sci 2023; 290:20230375. [PMID: 37040806 PMCID: PMC10089713 DOI: 10.1098/rspb.2023.0375] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 03/15/2023] [Indexed: 04/13/2023] Open
Abstract
Fertility is a major component of fitness but its genetic architecture remains poorly understood. Using a full diallel cross of 50 Drosophila Genetic Reference Panel inbred lines with whole genome sequences, we found substantial genetic variation in fertility largely attributable to females. We mapped genes associated with variation in female fertility by genome-wide association analysis of common variants in the fly genome. Validation of candidate genes by RNAi knockdown confirmed the role of the dopamine 2-like receptor (Dop2R) in promoting egg laying. We replicated the Dop2R effect in an independently collected productivity dataset and showed that the effect of the Dop2R variant was mediated in part by regulatory gene expression variation. This study demonstrates the strong potential of genome-wide association analysis in this diverse panel of inbred strains and subsequent functional analyses for understanding the genetic architecture of fitness traits.
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Affiliation(s)
- Richard F. Lyman
- Program in Genetics, W. M. Keck Center for Behavioral Biology and Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Rachel A. Lyman
- Program in Genetics, W. M. Keck Center for Behavioral Biology and Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Akihiko Yamamoto
- Program in Genetics, W. M. Keck Center for Behavioral Biology and Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Wen Huang
- Program in Genetics, W. M. Keck Center for Behavioral Biology and Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Susan T. Harbison
- Program in Genetics, W. M. Keck Center for Behavioral Biology and Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Shanshan Zhou
- Program in Genetics, W. M. Keck Center for Behavioral Biology and Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Robert R. H. Anholt
- Program in Genetics, W. M. Keck Center for Behavioral Biology and Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
| | - Trudy F. C. Mackay
- Program in Genetics, W. M. Keck Center for Behavioral Biology and Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, USA
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Winbush A, Singh ND. Variation in fine-scale recombination rate in temperature-evolved Drosophila melanogaster populations in response to selection. G3 GENES|GENOMES|GENETICS 2022; 12:6663992. [PMID: 35961026 PMCID: PMC9526048 DOI: 10.1093/g3journal/jkac208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 08/05/2022] [Indexed: 11/16/2022]
Abstract
Meiotic recombination plays a critical evolutionary role in maintaining fitness in response to selective pressures due to changing environments. Variation in recombination rate has been observed amongst and between species and populations and within genomes across numerous taxa. Studies have demonstrated a link between changes in recombination rate and selection, but the extent to which fine-scale recombination rate varies between evolved populations during the evolutionary period in response to selection is under active research. Here, we utilize a set of 3 temperature-evolved Drosophila melanogaster populations that were shown to have diverged in several phenotypes, including recombination rate, based on the temperature regime in which they evolved. Using whole-genome sequencing data from these populations, we generated linkage disequilibrium-based fine-scale recombination maps for each population. With these maps, we compare recombination rates and patterns among the 3 populations and show that they have diverged at fine scales but are conserved at broader scales. We further demonstrate a correlation between recombination rates and genomic variation in the 3 populations. Lastly, we show variation in localized regions of enhanced recombination rates, termed warm spots, between the populations with these warm spots and associated genes overlapping areas previously shown to have diverged in the 3 populations due to selection. These data support the existence of recombination modifiers in these populations which are subject to selection during evolutionary change.
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Affiliation(s)
- Ari Winbush
- Department of Biology, Institute of Ecology and Evolution, University of Oregon , Eugene, OR 97403, USA
| | - Nadia D Singh
- Department of Biology, Institute of Ecology and Evolution, University of Oregon , Eugene, OR 97403, USA
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5
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Winbush A, Singh ND. Genomics of Recombination Rate Variation in Temperature-Evolved Drosophila melanogaster Populations. Genome Biol Evol 2020; 13:6008691. [PMID: 33247719 PMCID: PMC7851596 DOI: 10.1093/gbe/evaa252] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/24/2020] [Indexed: 12/14/2022] Open
Abstract
Meiotic recombination is a critical process that ensures proper segregation of chromosome homologs through DNA double-strand break repair mechanisms. Rates of recombination are highly variable among various taxa, within species, and within genomes with far-reaching evolutionary and genomic consequences. The genetic basis of recombination rate variation is therefore crucial in the study of evolutionary biology but remains poorly understood. In this study, we took advantage of a set of experimental temperature-evolved populations of Drosophila melanogaster with heritable differences in recombination rates depending on the temperature regime in which they evolved. We performed whole-genome sequencing and identified several chromosomal regions that appear to be divergent depending on temperature regime. In addition, we identify a set of single-nucleotide polymorphisms and associated genes with significant differences in allele frequency when the different temperature populations are compared. Further refinement of these gene candidates emphasizing those expressed in the ovary and associated with DNA binding reveals numerous potential candidate genes such as Hr38, EcR, and mamo responsible for observed differences in recombination rates in these experimental evolution lines thus providing insight into the genetic basis of recombination rate variation.
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Affiliation(s)
- Ari Winbush
- Department of Biology, Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon, USA
| | - Nadia D Singh
- Department of Biology, Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon, USA
- Corresponding author: E-mail:
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Pannebakker BA, Cook N, van den Heuvel J, van de Zande L, Shuker DM. Genomics of sex allocation in the parasitoid wasp Nasonia vitripennis. BMC Genomics 2020; 21:499. [PMID: 32689940 PMCID: PMC7372847 DOI: 10.1186/s12864-020-06904-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 07/10/2020] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Whilst adaptive facultative sex allocation has been widely studied at the phenotypic level across a broad range of organisms, we still know remarkably little about its genetic architecture. Here, we explore the genome-wide basis of sex ratio variation in the parasitoid wasp Nasonia vitripennis, perhaps the best studied organism in terms of sex allocation, and well known for its response to local mate competition. RESULTS We performed a genome-wide association study (GWAS) for single foundress sex ratios using iso-female lines derived from the recently developed outbred N. vitripennis laboratory strain HVRx. The iso-female lines capture a sample of the genetic variation in HVRx and we present them as the first iteration of the Nasonia vitripennis Genome Reference Panel (NVGRP 1.0). This panel provides an assessment of the standing genetic variation for sex ratio in the study population. Using the NVGRP, we discovered a cluster of 18 linked SNPs, encompassing 9 annotated loci associated with sex ratio variation. Furthermore, we found evidence that sex ratio has a shared genetic basis with clutch size on three different chromosomes. CONCLUSIONS Our approach provides a thorough description of the quantitative genetic basis of sex ratio variation in Nasonia at the genome level and reveals a number of inter-related candidate loci underlying sex allocation regulation.
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Affiliation(s)
- Bart A Pannebakker
- Laboratory of Genetics, Wageningen University & Research, Wageningen, The Netherlands.
| | - Nicola Cook
- School of Biology, University of St Andrews, Fife, UK
| | - Joost van den Heuvel
- Laboratory of Genetics, Wageningen University & Research, Wageningen, The Netherlands
| | - Louis van de Zande
- Evolutionary Genetics, Development and Behaviour, Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands
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Abstract
Here we describe a collection of re-sequenced inbred lines of Drosophila serrata, sampled from a natural population situated deep within the species endemic distribution in Brisbane, Australia. D. serrata is a member of the speciose montium group whose members inhabit much of south east Asia and has been well studied for aspects of climatic adaptation, sexual selection, sexual dimorphism, and mate recognition. We sequenced 110 lines that were inbred via 17-20 generations of full-sib mating at an average coverage of 23.5x with paired-end Illumina reads. 15,228,692 biallelic SNPs passed quality control after being called using the Joint Genotyper for Inbred Lines (JGIL). Inbreeding was highly effective and the average levels of residual heterozygosity (0.86%) were well below theoretical expectations. As expected, linkage disequilibrium decayed rapidly, with r2 dropping below 0.1 within 100 base pairs. With the exception of four closely related pairs of lines which may have been due to technical errors, there was no statistical support for population substructure. Consistent with other endemic populations of other Drosophila species, preliminary population genetic analyses revealed high nucleotide diversity and, on average, negative Tajima’s D values. A preliminary GWAS was performed on a cuticular hydrocarbon trait, 2-Me-C28 revealing 4 SNPs passing Bonferroni significance residing in or near genes. One gene Cht9 may be involved in the transport of CHCs from the site of production (oenocytes) to the cuticle. Our panel will facilitate broader population genomic and quantitative genetic studies of this species and serve as an important complement to existing D. melanogaster panels that can be used to test for the conservation of genetic architectures across the Drosophila genus.
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8
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Jackson BC, Campos JL, Haddrill PR, Charlesworth B, Zeng K. Variation in the Intensity of Selection on Codon Bias over Time Causes Contrasting Patterns of Base Composition Evolution in Drosophila. Genome Biol Evol 2017; 9:102-123. [PMID: 28082609 PMCID: PMC5381600 DOI: 10.1093/gbe/evw291] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/07/2016] [Indexed: 12/11/2022] Open
Abstract
Four-fold degenerate coding sites form a major component of the genome, and are often used to make inferences about selection and demography, so that understanding their evolution is important. Despite previous efforts, many questions regarding the causes of base composition changes at these sites in Drosophila remain unanswered. To shed further light on this issue, we obtained a new whole-genome polymorphism data set from D. simulans. We analyzed samples from the putatively ancestral range of D. simulans, as well as an existing polymorphism data set from an African population of D. melanogaster. By using D. yakuba as an outgroup, we found clear evidence for selection on 4-fold sites along both lineages over a substantial period, with the intensity of selection increasing with GC content. Based on an explicit model of base composition evolution, we suggest that the observed AT-biased substitution pattern in both lineages is probably due to an ancestral reduction in selection intensity, and is unlikely to be the result of an increase in mutational bias towards AT alone. By using two polymorphism-based methods for estimating selection coefficients over different timescales, we show that the selection intensity on codon usage has been rather stable in D. simulans in the recent past, but the long-term estimates in D. melanogaster are much higher than the short-term ones, indicating a continuing decline in selection intensity, to such an extent that the short-term estimates suggest that selection is only active in the most GC-rich parts of the genome. Finally, we provide evidence for complex evolutionary patterns in the putatively neutral short introns, which cannot be explained by the standard GC-biased gene conversion model. These results reveal a dynamic picture of base composition evolution.
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Affiliation(s)
- Benjamin C Jackson
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, United Kingdom
| | - José L Campos
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Penelope R Haddrill
- Centre for Forensic Science, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, United Kingdom
| | - Brian Charlesworth
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Kai Zeng
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield, United Kingdom
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Guo Y, Fudali S, Gimeno J, DiGennaro P, Chang S, Williamson VM, Bird DM, Nielsen DM. Networks Underpinning Symbiosis Revealed Through Cross-Species eQTL Mapping. Genetics 2017; 206:2175-2184. [PMID: 28642272 PMCID: PMC5560814 DOI: 10.1534/genetics.117.202531] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2017] [Accepted: 06/09/2017] [Indexed: 12/13/2022] Open
Abstract
Organisms engage in extensive cross-species molecular dialog, yet the underlying molecular actors are known for only a few interactions. Many techniques have been designed to uncover genes involved in signaling between organisms. Typically, these focus on only one of the partners. We developed an expression quantitative trait locus (eQTL) mapping-based approach to identify cause-and-effect relationships between genes from two partners engaged in an interspecific interaction. We demonstrated the approach by assaying expression of 98 isogenic plants (Medicago truncatula), each inoculated with a genetically distinct line of the diploid parasitic nematode Meloidogyne hapla With this design, systematic differences in gene expression across host plants could be mapped to genetic polymorphisms of their infecting parasites. The effects of parasite genotypes on plant gene expression were often substantial, with up to 90-fold (P = 3.2 × 10-52) changes in expression levels caused by individual parasite loci. Mapped loci included a number of pleiotropic sites, including one 87-kb parasite locus that modulated expression of >60 host genes. The 213 host genes identified were substantially enriched for transcription factors. We distilled higher-order connections between polymorphisms and genes from both species via network inference. To replicate our results and test whether effects were conserved across a broader host range, we performed a confirmatory experiment using M. hapla-infected tomato. This revealed that homologous genes were similarly affected. Finally, to validate the broader utility of cross-species eQTL mapping, we applied the strategy to data from a Salmonella infection study, successfully identifying polymorphisms in the human genome affecting bacterial expression.
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Affiliation(s)
- Yuelong Guo
- Bioinformatics Research Center, North Carolina State University, Raleigh, North Carolina 27695
| | - Sylwia Fudali
- Department of Plant Pathology, University of California, Davis, California 95616
| | - Jacinta Gimeno
- Department of Plant Pathology, University of California, Davis, California 95616
| | - Peter DiGennaro
- Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina 27695
| | - Stella Chang
- Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina 27695
| | - Valerie M Williamson
- Department of Plant Pathology, University of California, Davis, California 95616
| | - David McK Bird
- Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina 27695
| | - Dahlia M Nielsen
- Bioinformatics Research Center, North Carolina State University, Raleigh, North Carolina 27695
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27695
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Yassin A, Delaney EK, Reddiex AJ, Seher TD, Bastide H, Appleton NC, Lack JB, David JR, Chenoweth SF, Pool JE, Kopp A. The pdm3 Locus Is a Hotspot for Recurrent Evolution of Female-Limited Color Dimorphism in Drosophila. Curr Biol 2016; 26:2412-2422. [PMID: 27546577 DOI: 10.1016/j.cub.2016.07.016] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 06/24/2016] [Accepted: 07/08/2016] [Indexed: 12/30/2022]
Abstract
Sex-limited polymorphisms are an intriguing form of sexual dimorphism that offer unique opportunities to reconstruct the evolutionary changes that decouple male and female traits encoded by a shared genome. We investigated the genetic basis of a Mendelian female-limited color dimorphism (FLCD) that segregates in natural populations of more than 20 species of the Drosophila montium subgroup. In these species, females have alternative abdominal color morphs, light and dark, whereas males have only one color morph in each species. A comprehensive molecular phylogeny of the montium subgroup supports multiple origins of FLCD. Despite this, we mapped FLCD to the same locus in four distantly related species-the transcription factor POU domain motif 3 (pdm3), which acts as a repressor of abdominal pigmentation in D. melanogaster. In D. serrata, FLCD maps to a structural variant in the first intron of pdm3; however, this variant is not found in the three other species-D. kikkawai, D. leontia, and D. burlai-and sequence analysis strongly suggests the pdm3 alleles responsible for FLCD originated independently at least three times. We propose that cis-regulatory changes in pdm3 form sexually dimorphic and monomorphic alleles that segregate within species and are preserved, at least in one species, by structural variation. Surprisingly, pdm3 has not been implicated in the evolution of sex-specific pigmentation outside the montium subgroup, suggesting that the genetic paths to sexual dimorphism may be constrained within a clade but variable across clades.
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Affiliation(s)
- Amir Yassin
- Laboratory of Genetics, University of Wisconsin-Madison, 425-G Henry Mall, Madison, WI 53705, USA
| | - Emily K Delaney
- Department of Evolution and Ecology, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA
| | - Adam J Reddiex
- School of Biological Sciences, University of Queensland, St. Lucia, Brisbane 4072, Australia
| | - Thaddeus D Seher
- Department of Evolution and Ecology, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA; Department of Quantitative and Systems Biology, University of California, Merced, 5200 North Lake Road, Merced, CA 95343, USA
| | - Héloïse Bastide
- Laboratory of Genetics, University of Wisconsin-Madison, 425-G Henry Mall, Madison, WI 53705, USA
| | - Nicholas C Appleton
- School of Biological Sciences, University of Queensland, St. Lucia, Brisbane 4072, Australia
| | - Justin B Lack
- Laboratory of Genetics, University of Wisconsin-Madison, 425-G Henry Mall, Madison, WI 53705, USA
| | - Jean R David
- Laboratoire Evolution, Génomes, Comportement, Ecologie (EGCE), CNRS, IRD, Université Paris Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
| | - Stephen F Chenoweth
- School of Biological Sciences, University of Queensland, St. Lucia, Brisbane 4072, Australia
| | - John E Pool
- Laboratory of Genetics, University of Wisconsin-Madison, 425-G Henry Mall, Madison, WI 53705, USA.
| | - Artyom Kopp
- Department of Evolution and Ecology, University of California, Davis, 1 Shields Avenue, Davis, CA 95616, USA.
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Najarro MA, Hackett JL, Smith BR, Highfill CA, King EG, Long AD, Macdonald SJ. Identifying Loci Contributing to Natural Variation in Xenobiotic Resistance in Drosophila. PLoS Genet 2015; 11:e1005663. [PMID: 26619284 PMCID: PMC4664282 DOI: 10.1371/journal.pgen.1005663] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 10/21/2015] [Indexed: 12/12/2022] Open
Abstract
Natural populations exhibit a great deal of interindividual genetic variation in the response to toxins, exemplified by the variable clinical efficacy of pharmaceutical drugs in humans, and the evolution of pesticide resistant insects. Such variation can result from several phenomena, including variable metabolic detoxification of the xenobiotic, and differential sensitivity of the molecular target of the toxin. Our goal is to genetically dissect variation in the response to xenobiotics, and characterize naturally-segregating polymorphisms that modulate toxicity. Here, we use the Drosophila Synthetic Population Resource (DSPR), a multiparent advanced intercross panel of recombinant inbred lines, to identify QTL (Quantitative Trait Loci) underlying xenobiotic resistance, and employ caffeine as a model toxic compound. Phenotyping over 1,700 genotypes led to the identification of ten QTL, each explaining 4.5-14.4% of the broad-sense heritability for caffeine resistance. Four QTL harbor members of the cytochrome P450 family of detoxification enzymes, which represent strong a priori candidate genes. The case is especially strong for Cyp12d1, with multiple lines of evidence indicating the gene causally impacts caffeine resistance. Cyp12d1 is implicated by QTL mapped in both panels of DSPR RILs, is significantly upregulated in the presence of caffeine, and RNAi knockdown robustly decreases caffeine tolerance. Furthermore, copy number variation at Cyp12d1 is strongly associated with phenotype in the DSPR, with a trend in the same direction observed in the DGRP (Drosophila Genetic Reference Panel). No additional plausible causative polymorphisms were observed in a full genomewide association study in the DGRP, or in analyses restricted to QTL regions mapped in the DSPR. Just as in human populations, replicating modest-effect, naturally-segregating causative variants in an association study framework in flies will likely require very large sample sizes.
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Affiliation(s)
- Michael A. Najarro
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
| | - Jennifer L. Hackett
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
| | - Brittny R. Smith
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
| | - Chad A. Highfill
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
| | - Elizabeth G. King
- Division of Biological Sciences, University of Missouri, Columbia, Missouri, United States of America
| | - Anthony D. Long
- Department of Ecology and Evolutionary Biology, University of California Irvine, Irvine, California, United States of America
| | - Stuart J. Macdonald
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
- Center for Computational Biology, University of Kansas, Lawrence, Kansas, United States of America
- * E-mail:
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Accounting for genetic architecture improves sequence based genomic prediction for a Drosophila fitness trait. PLoS One 2015; 10:e0126880. [PMID: 25950439 PMCID: PMC4423967 DOI: 10.1371/journal.pone.0126880] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 04/08/2015] [Indexed: 12/01/2022] Open
Abstract
The ability to predict quantitative trait phenotypes from molecular polymorphism data will revolutionize evolutionary biology, medicine and human biology, and animal and plant breeding. Efforts to map quantitative trait loci have yielded novel insights into the biology of quantitative traits, but the combination of individually significant quantitative trait loci typically has low predictive ability. Utilizing all segregating variants can give good predictive ability in plant and animal breeding populations, but gives little insight into trait biology. Here, we used the Drosophila Genetic Reference Panel to perform both a genome wide association analysis and genomic prediction for the fitness-related trait chill coma recovery time. We found substantial total genetic variation for chill coma recovery time, with a genetic architecture that differs between males and females, a small number of molecular variants with large main effects, and evidence for epistasis. Although the top additive variants explained 36% (17%) of the genetic variance among lines in females (males), the predictive ability using genomic best linear unbiased prediction and a relationship matrix using all common segregating variants was very low for females and zero for males. We hypothesized that the low predictive ability was due to the mismatch between the infinitesimal genetic architecture assumed by the genomic best linear unbiased prediction model and the true genetic architecture of chill coma recovery time. Indeed, we found that the predictive ability of the genomic best linear unbiased prediction model is markedly improved when we combine quantitative trait locus mapping with genomic prediction by only including the top variants associated with main and epistatic effects in the relationship matrix. This trait-associated prediction approach has the advantage that it yields biologically interpretable prediction models.
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Huang W, Massouras A, Inoue Y, Peiffer J, Ràmia M, Tarone AM, Turlapati L, Zichner T, Zhu D, Lyman RF, Magwire MM, Blankenburg K, Carbone MA, Chang K, Ellis LL, Fernandez S, Han Y, Highnam G, Hjelmen CE, Jack JR, Javaid M, Jayaseelan J, Kalra D, Lee S, Lewis L, Munidasa M, Ongeri F, Patel S, Perales L, Perez A, Pu L, Rollmann SM, Ruth R, Saada N, Warner C, Williams A, Wu YQ, Yamamoto A, Zhang Y, Zhu Y, Anholt RR, Korbel JO, Mittelman D, Muzny DM, Gibbs RA, Barbadilla A, Johnston JS, Stone EA, Richards S, Deplancke B, Mackay TF. Natural variation in genome architecture among 205 Drosophila melanogaster Genetic Reference Panel lines. Genome Res 2014; 24:1193-208. [PMID: 24714809 PMCID: PMC4079974 DOI: 10.1101/gr.171546.113] [Citation(s) in RCA: 434] [Impact Index Per Article: 39.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 04/01/2014] [Indexed: 12/30/2022]
Abstract
The Drosophila melanogaster Genetic Reference Panel (DGRP) is a community resource of 205 sequenced inbred lines, derived to improve our understanding of the effects of naturally occurring genetic variation on molecular and organismal phenotypes. We used an integrated genotyping strategy to identify 4,853,802 single nucleotide polymorphisms (SNPs) and 1,296,080 non-SNP variants. Our molecular population genomic analyses show higher deletion than insertion mutation rates and stronger purifying selection on deletions. Weaker selection on insertions than deletions is consistent with our observed distribution of genome size determined by flow cytometry, which is skewed toward larger genomes. Insertion/deletion and single nucleotide polymorphisms are positively correlated with each other and with local recombination, suggesting that their nonrandom distributions are due to hitchhiking and background selection. Our cytogenetic analysis identified 16 polymorphic inversions in the DGRP. Common inverted and standard karyotypes are genetically divergent and account for most of the variation in relatedness among the DGRP lines. Intriguingly, variation in genome size and many quantitative traits are significantly associated with inversions. Approximately 50% of the DGRP lines are infected with Wolbachia, and four lines have germline insertions of Wolbachia sequences, but effects of Wolbachia infection on quantitative traits are rarely significant. The DGRP complements ongoing efforts to functionally annotate the Drosophila genome. Indeed, 15% of all D. melanogaster genes segregate for potentially damaged proteins in the DGRP, and genome-wide analyses of quantitative traits identify novel candidate genes. The DGRP lines, sequence data, genotypes, quality scores, phenotypes, and analysis and visualization tools are publicly available.
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Affiliation(s)
- Wen Huang
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27595, USA
| | - Andreas Massouras
- Laboratory of Systems Biology and Genetics, Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
- Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Yutaka Inoue
- Center for Education in Liberal Arts and Sciences, Osaka University, Osaka-fu, 560-0043 Japan
| | - Jason Peiffer
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27595, USA
| | - Miquel Ràmia
- Genomics, Bioinformatics and Evolution Group, Institut de Biotecnologia i de Biomedicina (IBB), Department of Genetics and Microbiology, Campus Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
| | - Aaron M. Tarone
- Department of Entomology, Texas A&M University, College Station, Texas 77843, USA
| | - Lavanya Turlapati
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27595, USA
| | - Thomas Zichner
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
| | - Dianhui Zhu
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Richard F. Lyman
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27595, USA
| | - Michael M. Magwire
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27595, USA
| | - Kerstin Blankenburg
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Mary Anna Carbone
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27595, USA
| | - Kyle Chang
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Lisa L. Ellis
- Department of Entomology, Texas A&M University, College Station, Texas 77843, USA
| | - Sonia Fernandez
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Yi Han
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Gareth Highnam
- Virginia Tech Virginia Bioinformatics Institute and Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Carl E. Hjelmen
- Department of Entomology, Texas A&M University, College Station, Texas 77843, USA
| | - John R. Jack
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27595, USA
| | - Mehwish Javaid
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Joy Jayaseelan
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Divya Kalra
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Sandy Lee
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Lora Lewis
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Mala Munidasa
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Fiona Ongeri
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Shohba Patel
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Lora Perales
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Agapito Perez
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - LingLing Pu
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Stephanie M. Rollmann
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27595, USA
| | - Robert Ruth
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Nehad Saada
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Crystal Warner
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Aneisa Williams
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Yuan-Qing Wu
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Akihiko Yamamoto
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27595, USA
| | - Yiqing Zhang
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Yiming Zhu
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Robert R.H. Anholt
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27595, USA
| | - Jan O. Korbel
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
| | - David Mittelman
- Virginia Tech Virginia Bioinformatics Institute and Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Donna M. Muzny
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Richard A. Gibbs
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Antonio Barbadilla
- Genomics, Bioinformatics and Evolution Group, Institut de Biotecnologia i de Biomedicina (IBB), Department of Genetics and Microbiology, Campus Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
| | - J. Spencer Johnston
- Department of Entomology, Texas A&M University, College Station, Texas 77843, USA
| | - Eric A. Stone
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27595, USA
| | - Stephen Richards
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030 USA
| | - Bart Deplancke
- Laboratory of Systems Biology and Genetics, Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
- Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Trudy F.C. Mackay
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27595, USA
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A conserved suppressor mutation in a tryptophan auxotroph results in dysregulation of Pseudomonas quinolone signal synthesis. J Bacteriol 2014; 196:2413-22. [PMID: 24748618 DOI: 10.1128/jb.01635-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa is a common nosocomial pathogen that relies on three cell-to-cell signals to regulate multiple virulence factors. The Pseudomonas quinolone signal (PQS; 2-heptyl-3-hydroxy-4-quinolone) is one of these signals, and it is known to be important for P. aeruginosa pathogenesis. PQS is synthesized in a multistep reaction that condenses anthranilate and a fatty acid. In P. aeruginosa, anthranilate is produced via the kynurenine pathway and two separate anthranilate synthases, TrpEG and PhnAB, the latter of which is important for PQS synthesis. Others have previously shown that a P. aeruginosa tryptophan auxotroph could grow on tryptophan-depleted medium with a frequency of 10(-5) to 10(-6). These revertants produced more pyocyanin and had increased levels of phnA transcript. In this study, we constructed similar tryptophan auxotroph revertants and found that the reversion resulted from a synonymous G-to-A nucleotide mutation within pqsC. This change resulted in increased pyocyanin and decreased PQS, along with an increase in the level of the pqsD, pqsE, and phnAB transcripts. Reporter fusion and reverse transcriptase PCR studies indicated that a novel transcript containing pqsD, pqsE, and phnAB occurs in these revertants, and quantitative real-time PCR experiments suggested that the same transcript appears in the wild-type strain under nutrient-limiting conditions. These results imply that the PQS biosynthetic operon can produce an internal transcript that increases anthranilate production and greatly elevates the expression of the PQS signal response protein PqsE. This suggests a novel mechanism to ensure the production of both anthranilate and PQS-controlled virulence factors.
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Robinson MC, Stone EA, Singh ND. Population genomic analysis reveals no evidence for GC-biased gene conversion in Drosophila melanogaster. Mol Biol Evol 2013; 31:425-33. [PMID: 24214536 DOI: 10.1093/molbev/mst220] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Gene conversion is the nonreciprocal exchange of genetic material between homologous chromosomes. Multiple lines of evidence from a variety of taxa strongly suggest that gene conversion events are biased toward GC-bearing alleles. However, in Drosophila, the data have largely been indirect and unclear, with some studies supporting the predictions of a GC-biased gene conversion model and other data showing contradictory findings. Here, we test whether gene conversion events are GC-biased in Drosophila melanogaster using whole-genome polymorphism and divergence data. Our results provide no support for GC-biased gene conversion and thus suggest that this process is unlikely to significantly contribute to patterns of polymorphism and divergence in this system.
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Affiliation(s)
- Matthew C Robinson
- Department of Biological Sciences, Program in Genetics, North Carolina State University
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16
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Kenigsberg E, Tanay A. Drosophila functional elements are embedded in structurally constrained sequences. PLoS Genet 2013; 9:e1003512. [PMID: 23750124 PMCID: PMC3671938 DOI: 10.1371/journal.pgen.1003512] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 03/04/2013] [Indexed: 12/22/2022] Open
Abstract
Modern functional genomics uncovered numerous functional elements in metazoan genomes. Nevertheless, only a small fraction of the typical non-exonic genome contains elements that code for function directly. On the other hand, a much larger fraction of the genome is associated with significant evolutionary constraints, suggesting that much of the non-exonic genome is weakly functional. Here we show that in flies, local (30–70 bp) conserved sequence elements that are associated with multiple regulatory functions serve as focal points to a pattern of punctuated regional increase in G/C nucleotide frequencies. We show that this pattern, which covers a region tenfold larger than the conserved elements themselves, is an evolutionary consequence of a shift in the balance between gain and loss of G/C nucleotides and that it is correlated with nucleosome occupancy across multiple classes of epigenetic state. Evidence for compensatory evolution and analysis of SNP allele frequencies show that the evolutionary regime underlying this balance shift is likely to be non-neutral. These data suggest that current gaps in our understanding of genome function and evolutionary dynamics are explicable by a model of sparse sequence elements directly encoding for function, embedded into structural sequences that help to define the local and global epigenomic context of such functional elements. A key challenge in functional genomics is to predict evolutionary dynamics from functional annotation of the genome and vice versa. Modern epigenomic studies helped assign function to numerous new sequence elements, but left most of the genome essentially uncharacterized. Evolutionary genomics, on the other hand, consistently suggests that a much larger fraction of the un-annotated genome evolves under selective pressure. We hypothesize that this function-selection gap can be attributed to sequences that facilitate the physical organization of functional elements, such as transcription factor binding sites, within chromosomes. We exemplify this by studying in detail the sequences embedding small conserved elements (CEs) in Drosophila. We show that, while CEs have typically high AT content, high GC content levels around them are maintained by a non-neutral evolutionary balance between gain and loss of GC nucleotides. This non-uniform pattern is highly correlated with nucleosome organization around CEs, potentially imposing an evolutionary constraint on as much as one quarter of the genome. We suggest this can at least partly explain the above function-selection gap. Weak evolutionary constraints on “structural” sequences (at scales ranging from one nucleosome to recently described multi-megabase topological domains) may affect genome evolution just like structural motifs shape protein evolution.
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Affiliation(s)
- Ephraim Kenigsberg
- Department of Computer Science and Applied Mathematics and Department of Biological Regulation, Weizmann Institute, Rehovot, Israel
| | - Amos Tanay
- Department of Computer Science and Applied Mathematics and Department of Biological Regulation, Weizmann Institute, Rehovot, Israel
- * E-mail:
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17
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Haerty W, Ponting CP. Mutations within lncRNAs are effectively selected against in fruitfly but not in human. Genome Biol 2013; 14:R49. [PMID: 23710818 PMCID: PMC4053968 DOI: 10.1186/gb-2013-14-5-r49] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 05/27/2013] [Indexed: 02/07/2023] Open
Abstract
Background Previous studies in Drosophila and mammals have revealed levels of long non-coding RNAs (lncRNAs) sequence conservation that are intermediate between neutrally evolving and protein-coding sequence. These analyses compared conservation between species that diverged up to 75 million years ago. However, analysis of sequence polymorphisms within a species' population can provide an understanding of essentially contemporaneous selective constraints that are acting on lncRNAs and can quantify the deleterious effect of mutations occurring within these loci. Results We took advantage of polymorphisms derived from the genome sequences of 163 Drosophila melanogaster strains and 174 human individuals to calculate the distribution of fitness effects of single nucleotide polymorphisms occurring within intergenic lncRNAs and compared this to distributions for SNPs present within putatively neutral or protein-coding sequences. Our observations show that in D.melanogaster there is a significant excess of rare frequency variants within intergenic lncRNAs relative to neutrally evolving sequences, whereas selection on human intergenic lncRNAs appears to be effectively neutral. Approximately 30% of mutations within these fruitfly lncRNAs are estimated as being weakly deleterious. Conclusions These contrasting results can be attributed to the large difference in effective population sizes between the two species. Our results suggest that while the sequences of lncRNAs will be well conserved across insect species, such loci in mammals will accumulate greater proportions of deleterious changes through genetic drift.
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18
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Zichner T, Garfield DA, Rausch T, Stütz AM, Cannavó E, Braun M, Furlong EEM, Korbel JO. Impact of genomic structural variation in Drosophila melanogaster based on population-scale sequencing. Genome Res 2012; 23:568-79. [PMID: 23222910 PMCID: PMC3589545 DOI: 10.1101/gr.142646.112] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Genomic structural variation (SV) is a major determinant for phenotypic variation. Although it has been extensively studied in humans, the nucleotide resolution structure of SVs within the widely used model organism Drosophila remains unknown. We report a highly accurate, densely validated map of unbalanced SVs comprising 8962 deletions and 916 tandem duplications in 39 lines derived from short-read DNA sequencing in a natural population (the “Drosophila melanogaster Genetic Reference Panel,” DGRP). Most SVs (>90%) were inferred at nucleotide resolution, and a large fraction was genotyped across all samples. Comprehensive analyses of SV formation mechanisms using the short-read data revealed an abundance of SVs formed by mobile element and nonhomologous end-joining-mediated rearrangements, and clustering of variants into SV hotspots. We further observed a strong depletion of SVs overlapping genes, which, along with population genetics analyses, suggests that these SVs are often deleterious. We inferred several gene fusion events also highlighting the potential role of SVs in the generation of novel protein products. Expression quantitative trait locus (eQTL) mapping revealed the functional impact of our high-resolution SV map, with quantifiable effects at >100 genic loci. Our map represents a resource for population-level studies of SVs in an important model organism.
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Affiliation(s)
- Thomas Zichner
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
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Inferences of demography and selection in an African population of Drosophila melanogaster. Genetics 2012; 193:215-28. [PMID: 23105013 DOI: 10.1534/genetics.112.145318] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
It remains a central problem in population genetics to infer the past action of natural selection, and these inferences pose a challenge because demographic events will also substantially affect patterns of polymorphism and divergence. Thus it is imperative to explicitly model the underlying demographic history of the population whenever making inferences about natural selection. In light of the considerable interest in adaptation in African populations of Drosophila melanogaster, which are considered ancestral to the species, we generated a large polymorphism data set representing 2.1 Mb from each of 20 individuals from a Ugandan population of D. melanogaster. In contrast to previous inferences of a simple population expansion in eastern Africa, our demographic modeling of this ancestral population reveals a strong signature of a population bottleneck followed by population expansion, which has significant implications for future demographic modeling of derived populations of this species. Taking this more complex underlying demographic history into account, we also estimate a mean X-linked region-wide rate of adaptation of 6 × 10(-11)/site/generation and a mean selection coefficient of beneficial mutations of 0.0009. These inferences regarding the rate and strength of selection are largely consistent with most other estimates from D. melanogaster and indicate a relatively high rate of adaptation driven by weakly beneficial mutations.
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Abstract
A major challenge of biology is understanding the relationship between molecular genetic variation and variation in quantitative traits, including fitness. This relationship determines our ability to predict phenotypes from genotypes and to understand how evolutionary forces shape variation within and between species. Previous efforts to dissect the genotype-phenotype map were based on incomplete genotypic information. Here, we describe the Drosophila melanogaster Genetic Reference Panel (DGRP), a community resource for analysis of population genomics and quantitative traits. The DGRP consists of fully sequenced inbred lines derived from a natural population. Population genomic analyses reveal reduced polymorphism in centromeric autosomal regions and the X chromosome, evidence for positive and negative selection, and rapid evolution of the X chromosome. Many variants in novel genes, most at low frequency, are associated with quantitative traits and explain a large fraction of the phenotypic variance. The DGRP facilitates genotype-phenotype mapping using the power of Drosophila genetics.
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