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Puntambekar S, Newhouse R, San-Miguel J, Chauhan R, Vernaz G, Willis T, Wayland MT, Umrania Y, Miska EA, Prabakaran S. Evolutionary divergence of novel open reading frames in cichlids speciation. Sci Rep 2020; 10:21570. [PMID: 33299045 PMCID: PMC7726158 DOI: 10.1038/s41598-020-78555-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 11/26/2020] [Indexed: 01/02/2023] Open
Abstract
Novel open reading frames (nORFs) with coding potential may arise from noncoding DNA. Not much is known about their emergence, functional role, fixation in a population or contribution to adaptive radiation. Cichlids fishes exhibit extensive phenotypic diversification and speciation. Encounters with new environments alone are not sufficient to explain this striking diversity of cichlid radiation because other taxa coexistent with the Cichlidae demonstrate lower species richness. Wagner et al. analyzed cichlid diversification in 46 African lakes and reported that both extrinsic environmental factors and intrinsic lineage-specific traits related to sexual selection have strongly influenced the cichlid radiation, which indicates the existence of unknown molecular mechanisms responsible for rapid phenotypic diversification, such as emergence of novel open reading frames (nORFs). In this study, we integrated transcriptomic and proteomic signatures from two tissues of two cichlids species, identified nORFs and performed evolutionary analysis on these nORF regions. Our results suggest that the time scale of speciation of the two species and evolutionary divergence of these nORF genomic regions are similar and indicate a potential role for these nORFs in speciation of the cichlid fishes.
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Affiliation(s)
- Shraddha Puntambekar
- Department of Biology, Indian Institute of Science Education and Research, Pune, Maharashtra, 411008, India
| | - Rachel Newhouse
- Department of Genetics, University of Cambridge, Downing Site, Cambridge, CB2 3EH, UK
| | - Jaime San-Miguel
- Department of Genetics, University of Cambridge, Downing Site, Cambridge, CB2 3EH, UK
| | - Ruchi Chauhan
- Department of Genetics, University of Cambridge, Downing Site, Cambridge, CB2 3EH, UK
| | - Grégoire Vernaz
- Department of Genetics, University of Cambridge, Downing Site, Cambridge, CB2 3EH, UK
- The Wellcome Trust/CRUK Gurdon Institute, University of Cambridge, Cambridge, CB2 1QN, UK
- Wellcome Sanger Institute, Wellcome Genome Campus, Cambridge, CB10 1SA, UK
| | - Thomas Willis
- Department of Genetics, University of Cambridge, Downing Site, Cambridge, CB2 3EH, UK
| | - Matthew T Wayland
- Department of Zoology, University of Cambridge, Downing Site, Cambridge, CB2 3EH, UK
| | - Yagnesh Umrania
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR, UK
| | - Eric A Miska
- Department of Genetics, University of Cambridge, Downing Site, Cambridge, CB2 3EH, UK
- Wellcome Sanger Institute, Wellcome Genome Campus, Cambridge, CB10 1SA, UK
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR, UK
| | - Sudhakaran Prabakaran
- Department of Biology, Indian Institute of Science Education and Research, Pune, Maharashtra, 411008, India.
- Department of Genetics, University of Cambridge, Downing Site, Cambridge, CB2 3EH, UK.
- St. Edmund's College, University of Cambridge, Cambridge, CB3 0BN, UK.
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Carruthers M, Yurchenko AA, Augley JJ, Adams CE, Herzyk P, Elmer KR. De novo transcriptome assembly, annotation and comparison of four ecological and evolutionary model salmonid fish species. BMC Genomics 2018; 19:32. [PMID: 29310597 PMCID: PMC5759245 DOI: 10.1186/s12864-017-4379-x] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 12/11/2017] [Indexed: 12/21/2022] Open
Abstract
Background Salmonid fishes exhibit high levels of phenotypic and ecological variation and are thus ideal model systems for studying evolutionary processes of adaptive divergence and speciation. Furthermore, salmonids are of major interest in fisheries, aquaculture, and conservation research. Improving understanding of the genetic mechanisms underlying traits in these species would significantly progress research in these fields. Here we generate high quality de novo transcriptomes for four salmonid species: Atlantic salmon (Salmo salar), brown trout (Salmo trutta), Arctic charr (Salvelinus alpinus), and European whitefish (Coregonus lavaretus). All species except Atlantic salmon have no reference genome publicly available and few if any genomic studies to date. Results We used paired-end RNA-seq on Illumina to generate high coverage sequencing of multiple individuals, yielding between 180 and 210 M reads per species. After initial assembly, strict filtering was used to remove duplicated, redundant, and low confidence transcripts. The final assemblies consisted of 36,505 protein-coding transcripts for Atlantic salmon, 35,736 for brown trout, 33,126 for Arctic charr, and 33,697 for European whitefish and are made publicly available. Assembly completeness was assessed using three approaches, all of which supported high quality of the assemblies: 1) ~78% of Actinopterygian single-copy orthologs were successfully captured in our assemblies, 2) orthogroup inference identified high overlap in the protein sequences present across all four species (40% shared across all four and 84% shared by at least two), and 3) comparison with the published Atlantic salmon genome suggests that our assemblies represent well covered (~98%) protein-coding transcriptomes. Thorough comparison of the generated assemblies found that 84-90% of transcripts in each assembly were orthologous with at least one of the other three species. We also identified 34-37% of transcripts in each assembly as paralogs. We further compare completeness and annotation statistics of our new assemblies to available related species. Conclusion New, high-confidence protein-coding transcriptomes were generated for four ecologically and economically important species of salmonids. This offers a high quality pipeline for such complex genomes, represents a valuable contribution to the existing genomic resources for these species and provides robust tools for future investigation of gene expression and sequence evolution in these and other salmonid species. Electronic supplementary material The online version of this article (10.1186/s12864-017-4379-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Madeleine Carruthers
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, G12 8QQ, Glasgow, UK
| | - Andrey A Yurchenko
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, G12 8QQ, Glasgow, UK
| | - Julian J Augley
- Glasgow Polyomics, Wolfson Wohl Cancer Research Centre, University of Glasgow, G61 1QH, Glasgow, UK.,Present Address: Fios Genomics Ltd., Nine Edinburgh Bioquarter, 9 Little France Road, Edinburgh, EH16 4UX, UK
| | - Colin E Adams
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, G12 8QQ, Glasgow, UK.,Scottish Centre for Ecology and the Natural Environment, University of Glasgow, Rowardennan, G63 0AW, UK
| | - Pawel Herzyk
- Glasgow Polyomics, Wolfson Wohl Cancer Research Centre, University of Glasgow, G61 1QH, Glasgow, UK.,Institute of Molecular, Cell & Systems Biology, College of Medical, Veterinary & Life Sciences, University of Glasgow, G12 8QQ, Glasgow, UK
| | - Kathryn R Elmer
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, G12 8QQ, Glasgow, UK.
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A microsatellite-based genetic linkage map and putative sex-determining genomic regions in Lake Victoria cichlids. Gene 2015; 560:156-64. [PMID: 25639358 DOI: 10.1016/j.gene.2015.01.057] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 01/26/2015] [Accepted: 01/28/2015] [Indexed: 01/06/2023]
Abstract
Cichlid fishes in East Africa have undergone extensive adaptive radiation, which has led to spectacular diversity in their morphology and ecology. To date, genetic linkage maps have been constructed for several tilapias (riverine), Astatotilapia burtoni (Lake Tanganyika), and hybrid lines of Lake Malawi cichlids to facilitate genome-wide comparative analyses. In the present study, we constructed a genetic linkage map of the hybrid line of Lake Victoria cichlids, so that maps of cichlids from all the major areas of East Africa will be available. The genetic linkage map shown here is derived from the F2 progeny of an interspecific cross between Haplochromis chilotes and Haplochromis sauvagei and is based on 184 microsatellite and two single-nucleotide polymorphism (SNP) markers. Most of the microsatellite markers used in the present study were originally designed for other genetic linkage maps, allowing us to directly compare each linkage group (LG) among different cichlid groups. We found 25 LGs, the total length of which was 1133.2cM with an average marker spacing of about 6.09cM. Our subsequent linkage mapping analysis identified two putative sex-determining loci in cichlids. Interestingly, one of these two loci is located on cichlid LG5, on which the female heterogametic ZW locus and several quantitative trait loci (QTLs) related to adaptive evolution have been reported in Lake Malawi cichlids. We also found that V1R1 and V1R2, candidate genes for the fish pheromone receptor, are located very close to the recently detected sex-determining locus on cichlid LG5. The genetic linkage map study presented here may provide a valuable foundation for studying the chromosomal evolution of East African cichlids and the possible role of sex chromosomes in generating their genomic diversity.
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Henning F, Meyer A. The evolutionary genomics of cichlid fishes: explosive speciation and adaptation in the postgenomic era. Annu Rev Genomics Hum Genet 2014; 15:417-41. [PMID: 24898042 DOI: 10.1146/annurev-genom-090413-025412] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
With more than 1,500 species, cichlid fishes provide textbook examples of recent and diverse adaptive radiations, rapid rates of speciation, and the parallel evolution of adaptive phenotypes among both recently and distantly related lineages. This extraordinary diversity has attracted considerable interest from researchers across several biological disciplines. Their broad phenotypic variation coupled with recent divergence makes cichlids an ideal model system for understanding speciation, adaptation, and phenotypic diversification. Genetic mapping, genome-wide analyses, and genome projects have flourished in the past decade and have added new insights on the question of why there are so many cichlids. These recent findings also show that the sharing of older DNA polymorphisms is extensive and suggest that linage sorting is incomplete and that adaptive introgression played a role in the African radiation. Here, we review the results of genetic and genomic research on cichlids in the past decade and suggest some potential avenues to further exploit the potential of the cichlid model system to provide a better understanding of the genomics of adaptation and speciation.
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Affiliation(s)
- Frederico Henning
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany;
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Mazzuchelli J, Kocher TD, Yang F, Martins C. Integrating cytogenetics and genomics in comparative evolutionary studies of cichlid fish. BMC Genomics 2012; 13:463. [PMID: 22958299 PMCID: PMC3463429 DOI: 10.1186/1471-2164-13-463] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Accepted: 08/09/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The availability of a large number of recently sequenced vertebrate genomes opens new avenues to integrate cytogenetics and genomics in comparative and evolutionary studies. Cytogenetic mapping can offer alternative means to identify conserved synteny shared by distinct genomes and also to define genome regions that are still not fine characterized even after wide-ranging nucleotide sequence efforts. An efficient way to perform comparative cytogenetic mapping is based on BAC clones mapping by fluorescence in situ hybridization. In this report, to address the knowledge gap on the genome evolution in cichlid fishes, BAC clones of an Oreochromis niloticus library covering the linkage groups (LG) 1, 3, 5, and 7 were mapped onto the chromosomes of 9 African cichlid species. The cytogenetic mapping data were also integrated with BAC-end sequences information of O. niloticus and comparatively analyzed against the genome of other fish species and vertebrates. RESULTS The location of BACs from LG1, 3, 5, and 7 revealed a strong chromosomal conservation among the analyzed cichlid species genomes, which evidenced a synteny of the markers of each LG. Comparative in silico analysis also identified large genomic blocks that were conserved in distantly related fish groups and also in other vertebrates. CONCLUSIONS Although it has been suggested that fishes contain plastic genomes with high rates of chromosomal rearrangements and probably low rates of synteny conservation, our results evidence that large syntenic chromosome segments have been maintained conserved during evolution, at least for the considered markers. Additionally, our current cytogenetic mapping efforts integrated with genomic approaches conduct to a new perspective to address important questions involving chromosome evolution in fishes.
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Affiliation(s)
- Juliana Mazzuchelli
- Department of Morphology, Bioscience Institute, UNESP - São Paulo State University, 18618-970, Botucatu, SP, Brazil
| | | | - Fengtang Yang
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - Cesar Martins
- Department of Morphology, Bioscience Institute, UNESP - São Paulo State University, 18618-970, Botucatu, SP, Brazil
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6
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Meyer BS, Salzburger W. A novel primer set for multilocus phylogenetic inference in East African cichlid fishes. Mol Ecol Resour 2012; 12:1097-104. [PMID: 22816488 DOI: 10.1111/j.1755-0998.2012.03169.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The cichlid fishes in the East African Great Lakes are a prime model system for the study of adaptive radiation. Therefore, the availability of an elaborate phylogenetic framework is an important prerequisite. Previous phylogenetic hypotheses on East African cichlids are mainly based on mitochondrial and/or fragment-based markers, and, to date, no taxon-rich phylogeny exists that is based on multilocus DNA sequence data. Here, we present the design of an extensive new primer set (24 nuclear makers) for East African cichlids that will be used for multilocus phylogenetic analyses in the future. The primers are designed to work for both Sanger sequencing and next-generation sequencing with the 454 technology. As a proof of principle, we validate these primers in a phylogenetically representative set of 16 cichlid species from Lake Tanganyika and main river systems in the area and provide a basic evaluation of the markers with respect to marker length and diversity indices.
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Affiliation(s)
- Britta S Meyer
- Zoological Institute, University of Basel, Basel, Switzerland
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7
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Fan S, Elmer KR, Meyer A. Positive Darwinian selection drives the evolution of the morphology-related gene, EPCAM, in particularly species-rich lineages of African cichlid fishes. J Mol Evol 2011; 73:1-9. [PMID: 21811860 DOI: 10.1007/s00239-011-9452-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Accepted: 07/07/2011] [Indexed: 12/23/2022]
Abstract
The study of genetic evolution within the context of adaptive radiations offers insights to genes and selection pressures that result in rapid morphological change. Cichlid fishes are very species-rich and variable in coloration, behavior, and morphology, and so provide a classical model system for studying the genetics of adaptive radiation. In this study, we researched the evolution of the epithelial cell adhesion molecule (EPCAM), a candidate gene for the adaptive evolution of morphology broadly, and skin development specifically, in fishes. We compared EPCAM gene sequences from a rapidly speciating African cichlid lineage (the haplochromines), a species-poor African lineage (Nile tilapia Oreochromis niloticus), and a very young adaptive radiation in the Neotropics (sympatric crater lake Midas cichlids, Amphilophus sp.). Our results, based on a hierarchy of evolutionary analyses of nucleotide substitution, demonstrate that there are different selection pressures on the EPCAM gene among the cichlid lineages. Several waves of positive natural selection were identified not only on the terminal branches, but also on ancestral branches. Interestingly, significant positive or directional selection was found in the haplochromine cichlids only but not the comparatively species-poor tilapia lineage. We hypothesize that the strong signal of selection in the ancestral African cichlid lineage coincided with the transition from riverine to lacustrine habitat. The two neotropical species for which we collected new sequence data were invariant in the EPCAM locus. Our results suggest that functional changes promoted by positive Darwinian selection are widespread in the EPCAM gene during African cichlid evolution.
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Affiliation(s)
- Shaohua Fan
- Lehrstuhl für Zoologie und Evolutionsbiologie, Department of Biology, University of Konstanz, Universitätstrasse 10, 78457 Constance, Germany
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8
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Baldo L, Santos ME, Salzburger W. Comparative transcriptomics of Eastern African cichlid fishes shows signs of positive selection and a large contribution of untranslated regions to genetic diversity. Genome Biol Evol 2011; 3:443-55. [PMID: 21617250 PMCID: PMC3296448 DOI: 10.1093/gbe/evr047] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The hundreds of endemic species of cichlid fishes in the East African Great Lakes
Tanganyika, Malawi, and Victoria are a prime model system in evolutionary biology. With
five genomes currently being sequenced, eastern African cichlids also represent a
forthcoming genomic model for evolutionary studies of genotype-to-phenotype processes in
adaptive radiations. Here we report the functional annotation and comparative analyses of
transcriptome data sets for two eastern African cichlid species, Astatotilapia
burtoni and Ophthalmotilapia ventralis, representatives of the
modern haplochromines and ectodines, respectively. Nearly 647,000 expressed sequence tags
were assembled in more than 46,000 contigs for each species using the 454 sequencing
technology, largely expanding the current sequence data set publicly available for these
cichlids. Total predicted coverage of their proteome diversity is approximately 50% for
both species. Comparative qualitative and quantitative analyses show very similar
transcriptome data for the two species in terms of both functional annotation and relative
abundance of gene ontology terms expressed. Average genetic distance between species is
1.75% when all transcript types are considered including nonannotated sequences, 1.33% for
annotated sequences only including untranslated regions, and decreases to nearly half,
0.95%, for coding sequences only, suggesting a large contribution of noncoding regions to
their genetic diversity. Comparative analyses across the two species, tilapia and the
outgroup medaka based on an overlapping data set of 1,216 genes (∼526 kb) demonstrate
cichlid-specific signature of disruptive selection and provide a set of candidate genes
that are putatively under positive selection. Overall, these data sets offer the genetic
platform for future comparative analyses in light of the upcoming genomes for this
taxonomic group.
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Affiliation(s)
- Laura Baldo
- Zoological Institute, University of Basel, Basel, Switzerland.
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9
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Soler L, Conte MA, Katagiri T, Howe AE, Lee BY, Amemiya C, Stuart A, Dossat C, Poulain J, Johnson J, Di Palma F, Lindblad-Toh K, Baroiller JF, D'Cotta H, Ozouf-Costaz C, Kocher TD. Comparative physical maps derived from BAC end sequences of tilapia (Oreochromis niloticus). BMC Genomics 2010; 11:636. [PMID: 21080946 PMCID: PMC3018143 DOI: 10.1186/1471-2164-11-636] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2010] [Accepted: 11/16/2010] [Indexed: 01/07/2023] Open
Abstract
Background The Nile tilapia is the second most important fish in aquaculture. It is an excellent laboratory model, and is closely related to the African lake cichlids famous for their rapid rates of speciation. A suite of genomic resources has been developed for this species, including genetic maps and ESTs. Here we analyze BAC end-sequences to develop comparative physical maps, and estimate the number of genome rearrangements, between tilapia and other model fish species. Results We obtained sequence from one or both ends of 106,259 tilapia BACs. BLAST analysis against the genome assemblies of stickleback, medaka and pufferfish allowed identification of homologies for approximately 25,000 BACs for each species. We calculate that rearrangement breakpoints between tilapia and these species occur about every 3 Mb across the genome. Analysis of 35,000 clones previously assembled into contigs by restriction fingerprints allowed identification of longer-range syntenies. Conclusions Our data suggest that chromosomal evolution in recent teleosts is dominated by alternate loss of gene duplicates, and by intra-chromosomal rearrangements (~one per million years). These physical maps are a useful resource for comparative positional cloning of traits in cichlid fishes. The paired BAC end sequences from these clones will be an important resource for scaffolding forthcoming shotgun sequence assemblies of the tilapia genome.
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Affiliation(s)
- Lucile Soler
- CIRAD-PERSYST, Aquaculture Research Unit, TA B-20/A, Campus International de Baillarguet, 34398 Montpellier cedex 5, France
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Elmer KR, Fan S, Gunter HM, Jones JC, Boekhoff S, Kuraku S, Meyer A. Rapid evolution and selection inferred from the transcriptomes of sympatric crater lake cichlid fishes. Mol Ecol 2010; 19 Suppl 1:197-211. [PMID: 20331780 DOI: 10.1111/j.1365-294x.2009.04488.x] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Crater lakes provide a natural laboratory to study speciation of cichlid fishes by ecological divergence. Up to now, there has been a dearth of transcriptomic and genomic information that would aid in understanding the molecular basis of the phenotypic differentiation between young species. We used next-generation sequencing (Roche 454 massively parallel pyrosequencing) to characterize the diversity of expressed sequence tags between ecologically divergent, endemic and sympatric species of cichlid fishes from crater lake Apoyo, Nicaragua: benthic Amphilophus astorquii and limnetic Amphilophus zaliosus. We obtained 24 174 A. astorquii and 21 382 A. zaliosus high-quality expressed sequence tag contigs, of which 13 106 pairs are orthologous between species. Based on the ratio of nonsynonymous to synonymous substitutions, we identified six sequences exhibiting signals of strong diversifying selection (K(a)/K(s) > 1). These included genes involved in biosynthesis, metabolic processes and development. This transcriptome sequence variation may be reflective of natural selection acting on the genomes of these young, sympatric sister species. Based on Ks ratios and p-distances between 3'-untranslated regions (UTRs) calibrated to previously published species divergence times, we estimated a neutral transcriptome-wide substitutional mutation rate of approximately 1.25 x 10(-6) per site per year. We conclude that next-generation sequencing technologies allow us to infer natural selection acting to diversify the genomes of young species, such as crater lake cichlids, with much greater scope than previously possible.
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Affiliation(s)
- K R Elmer
- Department of Biology, University of Konstanz, Germany
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Lee BY, Howe AE, Conte MA, D'Cotta H, Pepey E, Baroiller JF, di Palma F, Carleton KL, Kocher TD. An EST resource for tilapia based on 17 normalized libraries and assembly of 116,899 sequence tags. BMC Genomics 2010; 11:278. [PMID: 20433739 PMCID: PMC2874815 DOI: 10.1186/1471-2164-11-278] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2009] [Accepted: 04/30/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Large collections of expressed sequence tags (ESTs) are a fundamental resource for analysis of gene expression and annotation of genome sequences. We generated 116,899 ESTs from 17 normalized and two non-normalized cDNA libraries representing 16 tissues from tilapia, a cichlid fish widely used in aquaculture and biological research. RESULTS The ESTs were assembled into 20,190 contigs and 36,028 singletons for a total of 56,218 unique sequences and a total assembled length of 35,168,415 bp. Over the whole project, a unique sequence was discovered for every 2.079 sequence reads. 17,722 (31.5%) of these unique sequences had significant BLAST hits (e-value < 10(-10)) to the UniProt database. CONCLUSION Normalization of the cDNA pools with double-stranded nuclease allowed us to efficiently sequence a large collection of ESTs. These sequences are an important resource for studies of gene expression, comparative mapping and annotation of the forthcoming tilapia genome sequence.
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Affiliation(s)
- Bo-Young Lee
- Department of Biology, University of Maryland, College Park, Maryland 20742, USA
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Mzighani SI, Nikaido M, Takeda M, Seehausen O, Budeba YL, Ngatunga BP, Katunzi EFB, Aibara M, Mizoiri S, Sato T, Tachida H, Okada N. Genetic variation and demographic history of the Haplochromis laparogramma group of Lake Victoria-An analysis based on SINEs and mitochondrial DNA. Gene 2010; 450:39-47. [PMID: 19837145 DOI: 10.1016/j.gene.2009.10.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Revised: 09/28/2009] [Accepted: 10/02/2009] [Indexed: 11/30/2022]
Abstract
More than 500 endemic haplochromine cichlid species inhabit Lake Victoria. This striking species diversity is a classical example of recent explosive adaptive radiation thought to have happened within the last approximately 15,000 years. In this study, we examined the population structure and historical demography of 3 pelagic haplochromine cichlid species that resemble in morphology and have similar niche, Haplochromis (Yssichromis) laparogramma, Haplochromis (Y.) pyrrhocephalus, and Haplochromis (Y.) sp. "glaucocephalus". We investigated the sequences of the mitochondrial DNA control region and the insertion patterns of short interspersed elements (SINEs) of 759 individuals. We show that sympatric forms are genetically differentiated in 4 of 6 cases, but we also found apparent weakening of the genetic differentiation in areas with turbid water. We estimated the timings of population expansion and species divergence to coincide with the refilling of the lake at the Pleistocene/Holocene boundary. We also found that estimates can be altered significantly by the choice of the shape of the molecular clock. If we employ the nonlinear clock model of evolutionary rates in which the rates are higher towards the recent, the population expansion was dated at around the event of desiccation of the lake ca. 17,000 YBP. Thus, we succeeded in clarifying the species and population structure of closely related Lake Victoria cichlids and in showing the importance of applying appropriate clock calibrations in elucidating recent evolutionary events.
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Affiliation(s)
- Semvua I Mzighani
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8501, Japan
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