1
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Baril T, Pym A, Bass C, Hayward A. Transposon accumulation at xenobiotic gene family loci in aphids. Genome Res 2023; 33:1718-1733. [PMID: 37852781 PMCID: PMC10691553 DOI: 10.1101/gr.277820.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 08/29/2023] [Indexed: 10/20/2023]
Abstract
The evolution of resistance is a major challenge for the sustainable control of pests and pathogens. Thus, a deeper understanding of the evolutionary and genomic mechanisms underpinning resistance evolution is required to safeguard health and food production. Several studies have implicated transposable elements (TEs) in xenobiotic-resistance evolution in insects. However, analyses are generally restricted to one insect species and/or one or a few xenobiotic gene families (XGFs). We examine evidence for TE accumulation at XGFs by performing a comparative genomic analysis across 20 aphid genomes, considering major subsets of XGFs involved in metabolic resistance to insecticides: cytochrome P450s, glutathione S-transferases, esterases, UDP-glucuronosyltransferases, and ABC transporters. We find that TEs are significantly enriched at XGFs compared with other genes. XGFs show similar levels of TE enrichment to those of housekeeping genes. But unlike housekeeping genes, XGFs are not constitutively expressed in germline cells, supporting the selective enrichment of TEs at XGFs rather than enrichment owing to chromatin availability. Hotspots of extreme TE enrichment occur around certain XGFs. We find, in aphids of agricultural importance, particular enrichment of TEs around cytochrome P450 genes with known functions in the detoxification of synthetic insecticides. Our results provide evidence supporting a general role for TEs as a source of genomic variation at host XGFs and highlight the existence of considerable variability in TE content across XGFs and host species. These findings show the need for detailed functional verification analyses to clarify the significance of individual TE insertions and elucidate underlying mechanisms at TE-XGF hotspots.
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Affiliation(s)
- Tobias Baril
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, United Kingdom
| | - Adam Pym
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, United Kingdom
| | - Chris Bass
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, United Kingdom
| | - Alex Hayward
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9FE, United Kingdom
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2
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Sadler KC. Epigenetics across the evolutionary tree: New paradigms from non-model animals. Bioessays 2023; 45:e2200036. [PMID: 36403219 DOI: 10.1002/bies.202200036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 10/28/2022] [Accepted: 11/03/2022] [Indexed: 11/21/2022]
Abstract
All animals have evolved solutions to manage their genomes, enabling the efficient organization of meters of DNA strands in the nucleus and allowing for nuanced regulation of gene expression while keeping transposable elements suppressed. Epigenetic modifications are central to accomplishing all these. Recent advances in sequencing technologies and the development of techniques that profile epigenetic marks and chromatin accessibility using reagents that can be used in any species has catapulted epigenomic studies in diverse animal species, shedding light on the multitude of epigenomic mechanisms utilized across the evolutionary tree. Now, comparative epigenomics is a rapidly growing field that is uncovering mechanistic aspects of epigenetic modifications and chromatin organization in non-model invertebrates, ranging from octopus to sponges. This review puts recent discoveries in the epigenetics of non-model invertebrates in historical context, and describes new insight into the patterning and functions of DNA methylation and other highly conserved epigenetic modifications.
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Affiliation(s)
- Kirsten C Sadler
- Program in Biology, New York University, Abu Dhabi, United Arab Emirates
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3
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Chang NC, Rovira Q, Wells J, Feschotte C, Vaquerizas JM. Zebrafish transposable elements show extensive diversification in age, genomic distribution, and developmental expression. Genome Res 2022; 32:1408-1423. [PMID: 34987056 PMCID: PMC9341512 DOI: 10.1101/gr.275655.121] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 12/30/2021] [Indexed: 12/02/2022]
Abstract
There is considerable interest in understanding the effect of transposable elements (TEs) on embryonic development. Studies in humans and mice are limited by the difficulty of working with mammalian embryos and by the relative scarcity of active TEs in these organisms. The zebrafish is an outstanding model for the study of vertebrate development, and over half of its genome consists of diverse TEs. However, zebrafish TEs remain poorly characterized. Here we describe the demography and genomic distribution of zebrafish TEs and their expression throughout embryogenesis using bulk and single-cell RNA sequencing data. These results reveal a highly dynamic genomic ecosystem comprising nearly 2000 distinct TE families, which vary in copy number by four orders of magnitude and span a wide range of ages. Longer retroelements tend to be retained in intergenic regions, whereas short interspersed nuclear elements (SINEs) and DNA transposons are more frequently found nearby or within genes. Locus-specific mapping of TE expression reveals extensive TE transcription during development. Although two-thirds of TE transcripts are likely driven by nearby gene promoters, we still observe stage- and tissue-specific expression patterns in self-regulated TEs. Long terminal repeat (LTR) retroelements are most transcriptionally active immediately following zygotic genome activation, whereas DNA transposons are enriched among transcripts expressed in later stages of development. Single-cell analysis reveals several endogenous retroviruses expressed in specific somatic cell lineages. Overall, our study provides a valuable resource for using zebrafish as a model to study the impact of TEs on vertebrate development.
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Affiliation(s)
- Ni-Chen Chang
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14850, USA
| | - Quirze Rovira
- Max Planck Institute for Molecular Biomedicine, 48149 Muenster, Germany
| | - Jonathan Wells
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14850, USA
| | - Cédric Feschotte
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14850, USA
| | - Juan M Vaquerizas
- Max Planck Institute for Molecular Biomedicine, 48149 Muenster, Germany
- MRC London Institute of Medical Sciences, London W12 0NN, United Kingdom
- Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London W12 0NN, United Kingdom
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4
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On the Base Composition of Transposable Elements. Int J Mol Sci 2022; 23:ijms23094755. [PMID: 35563146 PMCID: PMC9099904 DOI: 10.3390/ijms23094755] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 04/22/2022] [Accepted: 04/23/2022] [Indexed: 01/27/2023] Open
Abstract
Transposable elements exhibit a base composition that is often different from the genomic average and from hosts’ genes. The most common compositional bias is towards Adenosine and Thymine, although this bias is not universal, and elements with drastically different base composition can coexist within the same genome. The AT-richness of transposable elements is apparently maladaptive because it results in poor transcription and sub-optimal translation of proteins encoded by the elements. The cause(s) of this unusual base composition remain unclear and have yet to be investigated. Here, I review what is known about the nucleotide content of transposable elements and how this content can affect the genome of their host as well as their own replication. The compositional bias of transposable elements could result from several non-exclusive processes including horizontal transfer, mutational bias, and selection. It appears that mutation alone cannot explain the high AT-content of transposons and that selection plays a major role in the evolution of the compositional bias. The reason why selection would favor a maladaptive nucleotide content remains however unexplained and is an area of investigation that clearly deserves attention.
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5
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Baril T, Hayward A. Migrators within migrators: exploring transposable element dynamics in the monarch butterfly, Danaus plexippus. Mob DNA 2022; 13:5. [PMID: 35172896 PMCID: PMC8848866 DOI: 10.1186/s13100-022-00263-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 02/06/2022] [Indexed: 01/10/2023] Open
Abstract
Background Lepidoptera (butterflies and moths) are an important model system in ecology and evolution. A high-quality chromosomal genome assembly is available for the monarch butterfly (Danaus plexippus), but it lacks an in-depth transposable element (TE) annotation, presenting an opportunity to explore monarch TE dynamics and the impact of TEs on shaping the monarch genome. Results We find 6.21% of the monarch genome is comprised of TEs, a reduction of 6.85% compared to the original TE annotation performed on the draft genome assembly. Monarch TE content is low compared to two closely related species with available genomes, Danaus chrysippus (33.97% TE) and Danaus melanippus (11.87% TE). The biggest TE contributions to genome size in the monarch are LINEs and Penelope-like elements, and three newly identified families, r2-hero_dPle (LINE), penelope-1_dPle (Penelope-like), and hase2-1_dPle (SINE), collectively contribute 34.92% of total TE content. We find evidence of recent TE activity, with two novel Tc1 families rapidly expanding over recent timescales (tc1-1_dPle, tc1-2_dPle). LINE fragments show signatures of genomic deletions indicating a high rate of TE turnover. We investigate associations between TEs and wing colouration and immune genes and identify a three-fold increase in TE content around immune genes compared to other host genes. Conclusions We provide a detailed TE annotation and analysis for the monarch genome, revealing a considerably smaller TE contribution to genome content compared to two closely related Danaus species with available genome assemblies. We identify highly successful novel DNA TE families rapidly expanding over recent timescales, and ongoing signatures of both TE expansion and removal highlight the dynamic nature of repeat content in the monarch genome. Our findings also suggest that insect immune genes are promising candidates for future interrogation of TE-mediated host adaptation. Supplementary Information The online version contains supplementary material available at 10.1186/s13100-022-00263-5.
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Affiliation(s)
- Tobias Baril
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, UK.
| | - Alexander Hayward
- Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, UK.
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6
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Tusso S, Suo F, Liang Y, Du LL, Wolf JBW. Reactivation of transposable elements following hybridization in fission yeast. Genome Res 2021; 32:324-336. [PMID: 34907076 PMCID: PMC8805722 DOI: 10.1101/gr.276056.121] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 12/09/2021] [Indexed: 11/29/2022]
Abstract
Hybridization is thought to reactivate transposable elements (TEs) that were efficiently suppressed in the genomes of the parental hosts. Here, we provide evidence for this “genomic shock hypothesis” in the fission yeast Schizosaccharomyces pombe. In this species, two divergent lineages (Sp and Sk) have experienced recent, likely human-induced, hybridization. We used long-read sequencing data to assemble genomes of 37 samples derived from 31 S. pombe strains spanning a wide range of ancestral admixture proportions. A comprehensive TE inventory revealed exclusive presence of long terminal repeat (LTR) retrotransposons. Sequence analysis of active full-length elements, as well as solo LTRs, revealed a complex history of homologous recombination. Population genetic analyses of syntenic sequences placed insertion of many solo LTRs before the split of the Sp and Sk lineages. Most full-length elements were inserted more recently, after hybridization. With the exception of a single full-length element with signs of positive selection, both solo LTRs and, in particular, full-length elements carry signatures of purifying selection indicating effective removal by the host. Consistent with reactivation upon hybridization, the number of full-length LTR retrotransposons, varying extensively from zero to 87 among strains, significantly increases with the degree of genomic admixture. This study gives a detailed account of global TE diversity in S. pombe, documents complex recombination histories within TE elements, and provides evidence for the “genomic shock hypothesis.”
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Affiliation(s)
| | - Fang Suo
- National Institute of Biological Sciences
| | - Yue Liang
- National Institute of Biological Sciences
| | - Li-Lin Du
- National Institute of Biological Sciences
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7
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Almojil D, Bourgeois Y, Falis M, Hariyani I, Wilcox J, Boissinot S. The Structural, Functional and Evolutionary Impact of Transposable Elements in Eukaryotes. Genes (Basel) 2021; 12:genes12060918. [PMID: 34203645 PMCID: PMC8232201 DOI: 10.3390/genes12060918] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Revised: 06/04/2021] [Accepted: 06/07/2021] [Indexed: 12/22/2022] Open
Abstract
Transposable elements (TEs) are nearly ubiquitous in eukaryotes. The increase in genomic data, as well as progress in genome annotation and molecular biology techniques, have revealed the vast number of ways mobile elements have impacted the evolution of eukaryotes. In addition to being the main cause of difference in haploid genome size, TEs have affected the overall organization of genomes by accumulating preferentially in some genomic regions, by causing structural rearrangements or by modifying the recombination rate. Although the vast majority of insertions is neutral or deleterious, TEs have been an important source of evolutionary novelties and have played a determinant role in the evolution of fundamental biological processes. TEs have been recruited in the regulation of host genes and are implicated in the evolution of regulatory networks. They have also served as a source of protein-coding sequences or even entire genes. The impact of TEs on eukaryotic evolution is only now being fully appreciated and the role they may play in a number of biological processes, such as speciation and adaptation, remains to be deciphered.
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Affiliation(s)
- Dareen Almojil
- New York University Abu Dhabi, Saadiyat Island, Abu Dhabi P.O. Box 129188, United Arab Emirates; (D.A.); (M.F.); (I.H.); (J.W.)
| | - Yann Bourgeois
- School of Biological Sciences, University of Portsmouth, Portsmouth, UK;
| | - Marcin Falis
- New York University Abu Dhabi, Saadiyat Island, Abu Dhabi P.O. Box 129188, United Arab Emirates; (D.A.); (M.F.); (I.H.); (J.W.)
| | - Imtiyaz Hariyani
- New York University Abu Dhabi, Saadiyat Island, Abu Dhabi P.O. Box 129188, United Arab Emirates; (D.A.); (M.F.); (I.H.); (J.W.)
| | - Justin Wilcox
- New York University Abu Dhabi, Saadiyat Island, Abu Dhabi P.O. Box 129188, United Arab Emirates; (D.A.); (M.F.); (I.H.); (J.W.)
- Center for Genomics and Systems Biology, New York University Abu Dhabi, Saadiyat Island, Abu Dhabi P.O. Box 129188, United Arab Emirates
| | - Stéphane Boissinot
- New York University Abu Dhabi, Saadiyat Island, Abu Dhabi P.O. Box 129188, United Arab Emirates; (D.A.); (M.F.); (I.H.); (J.W.)
- Center for Genomics and Systems Biology, New York University Abu Dhabi, Saadiyat Island, Abu Dhabi P.O. Box 129188, United Arab Emirates
- Correspondence:
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8
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Impact of transposable elements on genome size variation between two closely related crustacean species. Anal Biochem 2020; 600:113770. [DOI: 10.1016/j.ab.2020.113770] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 04/13/2020] [Accepted: 05/05/2020] [Indexed: 12/19/2022]
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9
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Ruggiero RP, Boissinot S. Variation in base composition underlies functional and evolutionary divergence in non-LTR retrotransposons. Mob DNA 2020; 11:14. [PMID: 32280379 PMCID: PMC7140322 DOI: 10.1186/s13100-020-00209-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 03/24/2020] [Indexed: 12/03/2022] Open
Abstract
Background Non-LTR retrotransposons often exhibit base composition that is markedly different from the nucleotide content of their host’s gene. For instance, the mammalian L1 element is AT-rich with a strong A bias on the positive strand, which results in a reduced transcription. It is plausible that the A-richness of mammalian L1 is a self-regulatory mechanism reflecting a trade-off between transposition efficiency and the deleterious effect of L1 on its host. We examined if the A-richness of L1 is a general feature of non-LTR retrotransposons or if different clades of elements have evolved different nucleotide content. We also investigated if elements belonging to the same clade evolved towards different base composition in different genomes or if elements from different clades evolved towards similar base composition in the same genome. Results We found that non-LTR retrotransposons differ in base composition among clades within the same host but also that elements belonging to the same clade differ in base composition among hosts. We showed that nucleotide content remains constant within the same host over extended period of evolutionary time, despite mutational patterns that should drive nucleotide content away from the observed base composition. Conclusions Our results suggest that base composition is evolving under selection and may be reflective of the long-term co-evolution between non-LTR retrotransposons and their host. Finally, the coexistence of elements with drastically different base composition suggests that these elements may be using different strategies to persist and multiply in the genome of their host.
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Affiliation(s)
- Robert P Ruggiero
- New York University Abu Dhabi, Saadiyat Island, Abu Dhabi, United Arab Emirates PO 129188
| | - Stéphane Boissinot
- New York University Abu Dhabi, Saadiyat Island, Abu Dhabi, United Arab Emirates PO 129188
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10
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Ni Z, Zhou XY, Aslam S, Niu DK. Characterization of Human Dosage-Sensitive Transcription Factor Genes. Front Genet 2019; 10:1208. [PMID: 31867040 PMCID: PMC6904359 DOI: 10.3389/fgene.2019.01208] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Accepted: 11/01/2019] [Indexed: 11/13/2022] Open
Abstract
Copy number changes in protein-coding genes are detrimental if the consequent changes in protein concentrations disrupt essential cellular functions. The dosage sensitivity of transcription factor (TF) genes is particularly interesting because their products are essential in regulating the expression of genetic information. From four recently curated data sets of dosage-sensitive genes (genes with conserved copy numbers across mammals, ohnologs, and two data sets of haploinsufficient genes), we compiled a data set of the most reliable dosage-sensitive (MRDS) genes and a data set of the most reliable dosage-insensitive (MRDIS) genes. The MRDS genes were those present in all four data sets, while the MRDIS genes were those absent from any one of the four data sets and with the probability of being loss of function-intolerant (pLI) values < 0.5 in both of the haploinsufficient gene data sets. Enrichment analysis of TF genes among the MRDS and MRDIS gene data sets showed that TF genes are more likely to be dosage-sensitive than other genes in the human genome. The nuclear receptor family was the most enriched TF family among the dosage-sensitive genes. TF families with very few members were also deemed more likely to be dosage-sensitive than TF families with more members. In addition, we found a certain number of dosage-insensitive TFs. The most typical were the Krüppel-associated box domain-containing zinc-finger proteins (KZFPs). Gene ontology (GO) enrichment analysis showed that the MRDS TFs were enriched for many more terms than the MRDIS TFs; however, the proteins interacting with these two groups of TFs did not show such sharp differences. Furthermore, we found that the MRDIS KZFPs were not significantly enriched for any GO terms, whereas their interacting proteins were significantly enriched for thousands of GO terms. Further characterizations revealed significant differences between MRDS TFs and MRDIS TFs in the lengths and nucleotide compositions of DNA-binding sites as well as in expression level, protein size, and selective force.
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Affiliation(s)
- Zhihua Ni
- MOE Key Laboratory for Biodiversity Science and Ecological Engineering and Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
- College of Life Sciences, Hebei University, Baoding, China
| | - Xiao-Yu Zhou
- MOE Key Laboratory for Biodiversity Science and Ecological Engineering and Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Sidra Aslam
- MOE Key Laboratory for Biodiversity Science and Ecological Engineering and Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Deng-Ke Niu
- MOE Key Laboratory for Biodiversity Science and Ecological Engineering and Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
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11
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Expansion of LINEs and species-specific DNA repeats drives genome expansion in Asian Gypsy Moths. Sci Rep 2019; 9:16413. [PMID: 31712581 PMCID: PMC6848174 DOI: 10.1038/s41598-019-52840-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 10/18/2019] [Indexed: 01/16/2023] Open
Abstract
Two subspecies of Asian gypsy moth (AGM), Lymantria dispar asiatica and L. dispar japonica, pose a serious alien invasive threat to North American forests. Despite decades of research on the ecology and biology of this pest, limited AGM-specific genomic resources are currently available. Here, we report on the genome sequences and functional content of these AGM subspecies. The genomes of L.d. asiatica and L.d. japonica are the largest lepidopteran genomes sequenced to date, totaling 921 and 999 megabases, respectively. Large genome size in these subspecies is driven by the accumulation of specific classes of repeats. Genome-wide metabolic pathway reconstructions suggest strong genomic signatures of energy-related pathways in both subspecies, dominated by metabolic functions related to thermogenesis. The genome sequences reported here will provide tools for probing the molecular mechanisms underlying phenotypic traits that are thought to enhance AGM invasiveness.
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12
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Varadharajan S, Rastas P, Löytynoja A, Matschiner M, Calboli FCF, Guo B, Nederbragt AJ, Jakobsen KS, Merilä J. A High-Quality Assembly of the Nine-Spined Stickleback (Pungitius pungitius) Genome. Genome Biol Evol 2019; 11:3291-3308. [PMID: 31687752 PMCID: PMC7145574 DOI: 10.1093/gbe/evz240] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/30/2019] [Indexed: 12/22/2022] Open
Abstract
The Gasterosteidae fish family hosts several species that are important models for eco-evolutionary, genetic, and genomic research. In particular, a wealth of genetic and genomic data has been generated for the three-spined stickleback (Gasterosteus aculeatus), the "ecology's supermodel," whereas the genomic resources for the nine-spined stickleback (Pungitius pungitius) have remained relatively scarce. Here, we report a high-quality chromosome-level genome assembly of P. pungitius consisting of 5,303 contigs (N50 = 1.2 Mbp) with a total size of 521 Mbp. These contigs were mapped to 21 linkage groups using a high-density linkage map, yielding a final assembly with 98.5% BUSCO completeness. A total of 25,062 protein-coding genes were annotated, and about 23% of the assembly was found to consist of repetitive elements. A comprehensive analysis of repetitive elements uncovered centromere-specific tandem repeats and provided insights into the evolution of retrotransposons. A multigene phylogenetic analysis inferred a divergence time of about 26 million years ago (Ma) between nine- and three-spined sticklebacks, which is far older than the commonly assumed estimate of 13 Ma. Compared with the three-spined stickleback, we identified an additional duplication of several genes in the hemoglobin cluster. Sequencing data from populations adapted to different environments indicated potential copy number variations in hemoglobin genes. Furthermore, genome-wide synteny comparisons between three- and nine-spined sticklebacks identified chromosomal rearrangements underlying the karyotypic differences between the two species. The high-quality chromosome-scale assembly of the nine-spined stickleback genome obtained with long-read sequencing technology provides a crucial resource for comparative and population genomic investigations of stickleback fishes and teleosts.
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Affiliation(s)
- Srinidhi Varadharajan
- Department of Biology, Centre for Ecological and Evolutionary Synthesis, University of Oslo, Norway
| | - Pasi Rastas
- Ecological Genetics Research Unit, Research Programme in Organismal and Evolutionary Biology, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland
| | - Ari Löytynoja
- Institute of Biotechnology, University of Helsinki, Finland
| | - Michael Matschiner
- Department of Biology, Centre for Ecological and Evolutionary Synthesis, University of Oslo, Norway
- Department of Paleontology and Museum, University of Zurich, Switzerland
| | - Federico C F Calboli
- Ecological Genetics Research Unit, Research Programme in Organismal and Evolutionary Biology, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland
- Laboratory of Biodiversity and Evolutionary Genomics, KU Leuven, Leuven, Belgium
| | - Baocheng Guo
- Ecological Genetics Research Unit, Research Programme in Organismal and Evolutionary Biology, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology Chinese Academy of Sciences, Beijing, China
| | - Alexander J Nederbragt
- Department of Biology, Centre for Ecological and Evolutionary Synthesis, University of Oslo, Norway
- Biomedical Informatics Research Group, Department of Informatics, University of Oslo, Norway
| | - Kjetill S Jakobsen
- Department of Biology, Centre for Ecological and Evolutionary Synthesis, University of Oslo, Norway
| | - Juha Merilä
- Ecological Genetics Research Unit, Research Programme in Organismal and Evolutionary Biology, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland
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13
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Varadharajan S, Rastas P, Löytynoja A, Matschiner M, Calboli FCF, Guo B, Nederbragt AJ, Jakobsen KS, Merilä J. A High-Quality Assembly of the Nine-Spined Stickleback (Pungitius pungitius) Genome. Genome Biol Evol 2019. [PMID: 31687752 DOI: 10.1101/741751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023] Open
Abstract
The Gasterosteidae fish family hosts several species that are important models for eco-evolutionary, genetic, and genomic research. In particular, a wealth of genetic and genomic data has been generated for the three-spined stickleback (Gasterosteus aculeatus), the "ecology's supermodel," whereas the genomic resources for the nine-spined stickleback (Pungitius pungitius) have remained relatively scarce. Here, we report a high-quality chromosome-level genome assembly of P. pungitius consisting of 5,303 contigs (N50 = 1.2 Mbp) with a total size of 521 Mbp. These contigs were mapped to 21 linkage groups using a high-density linkage map, yielding a final assembly with 98.5% BUSCO completeness. A total of 25,062 protein-coding genes were annotated, and about 23% of the assembly was found to consist of repetitive elements. A comprehensive analysis of repetitive elements uncovered centromere-specific tandem repeats and provided insights into the evolution of retrotransposons. A multigene phylogenetic analysis inferred a divergence time of about 26 million years ago (Ma) between nine- and three-spined sticklebacks, which is far older than the commonly assumed estimate of 13 Ma. Compared with the three-spined stickleback, we identified an additional duplication of several genes in the hemoglobin cluster. Sequencing data from populations adapted to different environments indicated potential copy number variations in hemoglobin genes. Furthermore, genome-wide synteny comparisons between three- and nine-spined sticklebacks identified chromosomal rearrangements underlying the karyotypic differences between the two species. The high-quality chromosome-scale assembly of the nine-spined stickleback genome obtained with long-read sequencing technology provides a crucial resource for comparative and population genomic investigations of stickleback fishes and teleosts.
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Affiliation(s)
- Srinidhi Varadharajan
- Department of Biology, Centre for Ecological and Evolutionary Synthesis, University of Oslo, Norway
| | - Pasi Rastas
- Ecological Genetics Research Unit, Research Programme in Organismal and Evolutionary Biology, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland
| | - Ari Löytynoja
- Institute of Biotechnology, University of Helsinki, Finland
| | - Michael Matschiner
- Department of Biology, Centre for Ecological and Evolutionary Synthesis, University of Oslo, Norway
- Department of Paleontology and Museum, University of Zurich, Switzerland
| | - Federico C F Calboli
- Ecological Genetics Research Unit, Research Programme in Organismal and Evolutionary Biology, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland
- Laboratory of Biodiversity and Evolutionary Genomics, KU Leuven, Leuven, Belgium
| | - Baocheng Guo
- Ecological Genetics Research Unit, Research Programme in Organismal and Evolutionary Biology, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland
- Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology Chinese Academy of Sciences, Beijing, China
| | - Alexander J Nederbragt
- Department of Biology, Centre for Ecological and Evolutionary Synthesis, University of Oslo, Norway
- Biomedical Informatics Research Group, Department of Informatics, University of Oslo, Norway
| | - Kjetill S Jakobsen
- Department of Biology, Centre for Ecological and Evolutionary Synthesis, University of Oslo, Norway
| | - Juha Merilä
- Ecological Genetics Research Unit, Research Programme in Organismal and Evolutionary Biology, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland
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14
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Bourgeois Y, Boissinot S. On the Population Dynamics of Junk: A Review on the Population Genomics of Transposable Elements. Genes (Basel) 2019; 10:genes10060419. [PMID: 31151307 PMCID: PMC6627506 DOI: 10.3390/genes10060419] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 05/05/2019] [Accepted: 05/21/2019] [Indexed: 01/18/2023] Open
Abstract
Transposable elements (TEs) play an important role in shaping genomic organization and structure, and may cause dramatic changes in phenotypes. Despite the genetic load they may impose on their host and their importance in microevolutionary processes such as adaptation and speciation, the number of population genetics studies focused on TEs has been rather limited so far compared to single nucleotide polymorphisms (SNPs). Here, we review the current knowledge about the dynamics of transposable elements at recent evolutionary time scales, and discuss the mechanisms that condition their abundance and frequency. We first discuss non-adaptive mechanisms such as purifying selection and the variable rates of transposition and elimination, and then focus on positive and balancing selection, to finally conclude on the potential role of TEs in causing genomic incompatibilities and eventually speciation. We also suggest possible ways to better model TEs dynamics in a population genomics context by incorporating recent advances in TEs into the rich information provided by SNPs about the demography, selection, and intrinsic properties of genomes.
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Affiliation(s)
- Yann Bourgeois
- New York University Abu Dhabi, P.O. 129188, Saadiyat Island, Abu Dhabi, United Arab Emirates.
| | - Stéphane Boissinot
- New York University Abu Dhabi, P.O. 129188, Saadiyat Island, Abu Dhabi, United Arab Emirates.
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15
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Pasquesi GIM, Adams RH, Card DC, Schield DR, Corbin AB, Perry BW, Reyes-Velasco J, Ruggiero RP, Vandewege MW, Shortt JA, Castoe TA. Squamate reptiles challenge paradigms of genomic repeat element evolution set by birds and mammals. Nat Commun 2018; 9:2774. [PMID: 30018307 PMCID: PMC6050309 DOI: 10.1038/s41467-018-05279-1] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 06/25/2018] [Indexed: 12/14/2022] Open
Abstract
Broad paradigms of vertebrate genomic repeat element evolution have been largely shaped by analyses of mammalian and avian genomes. Here, based on analyses of genomes sequenced from over 60 squamate reptiles (lizards and snakes), we show that patterns of genomic repeat landscape evolution in squamates challenge such paradigms. Despite low variance in genome size, squamate genomes exhibit surprisingly high variation among species in abundance (ca. 25–73% of the genome) and composition of identifiable repeat elements. We also demonstrate that snake genomes have experienced microsatellite seeding by transposable elements at a scale unparalleled among eukaryotes, leading to some snake genomes containing the highest microsatellite content of any known eukaryote. Our analyses of transposable element evolution across squamates also suggest that lineage-specific variation in mechanisms of transposable element activity and silencing, rather than variation in species-specific demography, may play a dominant role in driving variation in repeat element landscapes across squamate phylogeny. Large-scale patterns of genomic repeat element evolution have been studied mainly in birds and mammals. Here, the authors analyze the genomes of over 60 squamate reptiles and show high variation in repeat elements compared to mammals and birds, and particularly high microsatellite seeding in snakes.
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Affiliation(s)
- Giulia I M Pasquesi
- Department of Biology, University of Texas at Arlington, 501S. Nedderman Drive, Arlington, TX, 76019, USA
| | - Richard H Adams
- Department of Biology, University of Texas at Arlington, 501S. Nedderman Drive, Arlington, TX, 76019, USA
| | - Daren C Card
- Department of Biology, University of Texas at Arlington, 501S. Nedderman Drive, Arlington, TX, 76019, USA
| | - Drew R Schield
- Department of Biology, University of Texas at Arlington, 501S. Nedderman Drive, Arlington, TX, 76019, USA
| | - Andrew B Corbin
- Department of Biology, University of Texas at Arlington, 501S. Nedderman Drive, Arlington, TX, 76019, USA
| | - Blair W Perry
- Department of Biology, University of Texas at Arlington, 501S. Nedderman Drive, Arlington, TX, 76019, USA
| | - Jacobo Reyes-Velasco
- Department of Biology, University of Texas at Arlington, 501S. Nedderman Drive, Arlington, TX, 76019, USA.,Department of Biology, New York University Abu Dhabi, Saadiyat Island, United Arab Emirates
| | - Robert P Ruggiero
- Department of Biology, New York University Abu Dhabi, Saadiyat Island, United Arab Emirates
| | - Michael W Vandewege
- Department of Biology, Institute for Genomics and Evolutionary Medicine, Temple University, Philadelphia, PA, 19122, USA
| | - Jonathan A Shortt
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO, 80045, USA
| | - Todd A Castoe
- Department of Biology, University of Texas at Arlington, 501S. Nedderman Drive, Arlington, TX, 76019, USA.
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16
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Xue AT, Ruggiero RP, Hickerson MJ, Boissinot S. Differential Effect of Selection against LINE Retrotransposons among Vertebrates Inferred from Whole-Genome Data and Demographic Modeling. Genome Biol Evol 2018; 10:1265-1281. [PMID: 29688421 PMCID: PMC5963298 DOI: 10.1093/gbe/evy083] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/20/2018] [Indexed: 12/30/2022] Open
Abstract
Variation in LINE composition is one of the major determinants for the substantial size and structural differences among vertebrate genomes. In particular, the larger genomes of mammals are characterized by hundreds of thousands of copies from a single LINE clade, L1, whereas nonmammalian vertebrates possess a much greater diversity of LINEs, yet with orders of magnitude less in copy number. It has been proposed that such variation in copy number among vertebrates is due to differential effect of LINE insertions on host fitness. To investigate LINE selection, we deployed a framework of demographic modeling, coalescent simulations, and probabilistic inference against population-level whole-genome data sets for four model species: one population each of threespine stickleback, green anole, and house mouse, as well as three human populations. Specifically, we inferred a null demographic background utilizing SNP data, which was then exploited to simulate a putative null distribution of summary statistics that was compared with LINE data. Subsequently, we applied the inferred null demographic model with an additional exponential size change parameter, coupled with model selection, to test for neutrality as well as estimate the strength of either negative or positive selection. We found a robust signal for purifying selection in anole and mouse, but a lack of clear evidence for selection in stickleback and human. Overall, we demonstrated LINE insertion dynamics that are not in accordance to a mammalian versus nonmammalian dichotomy, and instead the degree of existing LINE activity together with host-specific demographic history may be the main determinants of LINE abundance.
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Affiliation(s)
- Alexander T Xue
- Department of Biology: Subprogram in Ecology, Evolutionary Biology, and Behavior, City College and Graduate Center of City University of New York
- Human Genetics Institute of New Jersey and Department of Genetics, Rutgers University, Piscataway
| | - Robert P Ruggiero
- New York University Abu Dhabi, Saadiyat Island Campus, United Arab Emirates
| | - Michael J Hickerson
- Department of Biology: Subprogram in Ecology, Evolutionary Biology, and Behavior, City College and Graduate Center of City University of New York
- Division of Invertebrate Zoology, American Museum of Natural History, New York, New York
| | - Stéphane Boissinot
- New York University Abu Dhabi, Saadiyat Island Campus, United Arab Emirates
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17
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Sookdeo A, Hepp CM, Boissinot S. Contrasted patterns of evolution of the LINE-1 retrotransposon in perissodactyls: the history of a LINE-1 extinction. Mob DNA 2018; 9:12. [PMID: 29610583 PMCID: PMC5872511 DOI: 10.1186/s13100-018-0117-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 03/22/2018] [Indexed: 12/30/2022] Open
Abstract
Background LINE-1 (L1) is the dominant autonomously replicating non-LTR retrotransposon in mammals. Although our knowledge of L1 evolution across the tree of life has considerably improved in recent years, what we know of L1 evolution in mammals is biased and comes mostly from studies in primates (mostly human) and rodents (mostly mouse). It is unclear if patterns of evolution that are shared between those two groups apply to other mammalian orders. Here we performed a detailed study on the evolution of L1 in perissodactyls by making use of the complete genome of the domestic horse and of the white rhinoceros. This mammalian order offers an excellent model to study the extinction of L1 since the rhinoceros is one of the few mammalian species to have lost active L1. Results We found that multiple L1 lineages, carrying different 5’UTRs, have been simultaneously active during the evolution of perissodactyls. We also found that L1 has continuously amplified and diversified in horse. In rhinoceros, L1 was very prolific early on. Two successful families were simultaneously active until ~20my ago but became extinct suddenly at exactly the same time. Conclusions The general pattern of L1 evolution in perissodactyls is very similar to what was previously described in mouse and human, suggesting some commonalities in the way mammalian genomes interact with L1. We confirmed the extinction of L1 in rhinoceros and we discuss several possible mechanisms. Electronic supplementary material The online version of this article (10.1186/s13100-018-0117-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Akash Sookdeo
- 1Department of Biology, New York University, New York, NY USA
| | - Crystal M Hepp
- 2School of Informatics, Computing, and Cyber Systems, Northern Arizona University, Flagstaff, AZ USA
| | - Stéphane Boissinot
- 3New York University Abu Dhabi, Saadiyat Island, Abu Dhabi, United Arab Emirates
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18
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Boissinot S, Sookdeo A. The Evolution of LINE-1 in Vertebrates. Genome Biol Evol 2018; 8:3485-3507. [PMID: 28175298 PMCID: PMC5381506 DOI: 10.1093/gbe/evw247] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/03/2016] [Indexed: 12/21/2022] Open
Abstract
The abundance and diversity of the LINE-1 (L1) retrotransposon differ greatly among vertebrates. Mammalian genomes contain hundreds of thousands L1s that have accumulated since the origin of mammals. A single group of very similar elements is active at a time in mammals, thus a single lineage of active families has evolved in this group. In contrast, non-mammalian genomes (fish, amphibians, reptiles) harbor a large diversity of concurrently transposing families, which are all represented by very small number of recently inserted copies. Why the pattern of diversity and abundance of L1 is so different among vertebrates remains unknown. To address this issue, we performed a detailed analysis of the evolution of active L1 in 14 mammals and in 3 non-mammalian vertebrate model species. We examined the evolution of base composition and codon bias, the general structure, and the evolution of the different domains of L1 (5′UTR, ORF1, ORF2, 3′UTR). L1s differ substantially in length, base composition, and structure among vertebrates. The most variation is found in the 5′UTR, which is longer in amniotes, and in the ORF1, which tend to evolve faster in mammals. The highly divergent L1 families of lizard, frog, and fish share species-specific features suggesting that they are subjected to the same functional constraints imposed by their host. The relative conservation of the 5′UTR and ORF1 in non-mammalian vertebrates suggests that the repression of transposition by the host does not act in a sequence-specific manner and did not result in an arms race, as is observed in mammals.
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19
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Talla V, Suh A, Kalsoom F, Dincă V, Vila R, Friberg M, Wiklund C, Backström N. Rapid Increase in Genome Size as a Consequence of Transposable Element Hyperactivity in Wood-White (Leptidea) Butterflies. Genome Biol Evol 2017; 9:2491-2505. [PMID: 28981642 PMCID: PMC5737376 DOI: 10.1093/gbe/evx163] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/22/2016] [Indexed: 12/14/2022] Open
Abstract
Characterizing and quantifying genome size variation among organisms and understanding if genome size evolves as a consequence of adaptive or stochastic processes have been long-standing goals in evolutionary biology. Here, we investigate genome size variation and association with transposable elements (TEs) across lepidopteran lineages using a novel genome assembly of the common wood-white (Leptidea sinapis) and population re-sequencing data from both L. sinapis and the closely related L. reali and L. juvernica together with 12 previously available lepidopteran genome assemblies. A phylogenetic analysis confirms established relationships among species, but identifies previously unknown intraspecific structure within Leptidea lineages. The genome assembly of L. sinapis is one of the largest of any lepidopteran taxon so far (643 Mb) and genome size is correlated with abundance of TEs, both in Lepidoptera in general and within Leptidea where L. juvernica from Kazakhstan has considerably larger genome size than any other Leptidea population. Specific TE subclasses have been active in different Lepidoptera lineages with a pronounced expansion of predominantly LINEs, DNA elements, and unclassified TEs in the Leptidea lineage after the split from other Pieridae. The rate of genome expansion in Leptidea in general has been in the range of four Mb/Million year (My), with an increase in a particular L. juvernica population to 72 Mb/My. The considerable differences in accumulation rates of specific TE classes in different lineages indicate that TE activity plays a major role in genome size evolution in butterflies and moths.
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Affiliation(s)
- Venkat Talla
- Department of Evolutionary Biology, Evolutionary Biology Centre (EBC), Uppsala University, Sweden
| | - Alexander Suh
- Department of Evolutionary Biology, Evolutionary Biology Centre (EBC), Uppsala University, Sweden
| | - Faheema Kalsoom
- Department of Evolutionary Biology, Evolutionary Biology Centre (EBC), Uppsala University, Sweden
| | - Vlad Dincă
- Animal Biodiversity and Evolution Program, Institut de Biologia Evolutiva (CSIC-UPF), Barcelona, Spain
| | - Roger Vila
- Animal Biodiversity and Evolution Program, Institut de Biologia Evolutiva (CSIC-UPF), Barcelona, Spain
| | - Magne Friberg
- Department of Plant Ecology and Evolution, Evolutionary Biology Centre (EBC), Uppsala University, Sweden
| | - Christer Wiklund
- Division of Ecology, Department of Zoology, Stockholm University, Sweden
| | - Niclas Backström
- Department of Evolutionary Biology, Evolutionary Biology Centre (EBC), Uppsala University, Sweden
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20
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Ruggiero RP, Bourgeois Y, Boissinot S. LINE Insertion Polymorphisms are Abundant but at Low Frequencies across Populations of Anolis carolinensis. Front Genet 2017; 8:44. [PMID: 28450881 PMCID: PMC5389967 DOI: 10.3389/fgene.2017.00044] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 03/29/2017] [Indexed: 12/30/2022] Open
Abstract
Vertebrate genomes differ considerably in size and structure. Among the features that show the most variation is the abundance of Long Interspersed Nuclear Elements (LINEs). Mammalian genomes contain 100,000s LINEs that belong to a single clade, L1, and in most species a single family is usually active at a time. In contrast, non-mammalian vertebrates (fish, amphibians and reptiles) contain multiple active families, belonging to several clades, but each of them is represented by a small number of recently inserted copies. It is unclear why vertebrate genomes harbor such drastic differences in LINE composition. To address this issue, we conducted whole genome resequencing to investigate the population genomics of LINEs across 13 genomes of the lizard Anolis carolinensis sampled from two geographically and genetically distinct populations in the Eastern Florida and the Gulf Atlantic regions of the United States. We used the Mobile Element Locator Tool to identify and genotype polymorphic insertions from five major clades of LINEs (CR1, L1, L2, RTE and R4) and the 41 subfamilies that constitute them. Across these groups we found large variation in the frequency of polymorphic insertions and the observed length distributions of these insertions, suggesting these groups vary in their activity and how frequently they successfully generate full-length, potentially active copies. Though we found an abundance of polymorphic insertions (over 45,000) most of these were observed at low frequencies and typically appeared as singletons. Site frequency spectra for most LINEs showed a significant shift toward low frequency alleles compared to the spectra observed for total genomic single nucleotide polymorphisms. Using Tajima's D, FST and the mean number of pairwise differences in LINE insertion polymorphisms, we found evidence that negative selection is acting on LINE families in a length-dependent manner, its effects being stronger in the larger Eastern Florida population. Our results suggest that a large effective population size and negative selection limit the expansion of polymorphic LINE insertions across these populations and that the probability of LINE polymorphisms reaching fixation is extremely low.
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21
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Abstract
Genome size in mammals and birds shows remarkably little interspecific variation compared with other taxa. However, genome sequencing has revealed that many mammal and bird lineages have experienced differential rates of transposable element (TE) accumulation, which would be predicted to cause substantial variation in genome size between species. Thus, we hypothesize that there has been covariation between the amount of DNA gained by transposition and lost by deletion during mammal and avian evolution, resulting in genome size equilibrium. To test this model, we develop computational methods to quantify the amount of DNA gained by TE expansion and lost by deletion over the last 100 My in the lineages of 10 species of eutherian mammals and 24 species of birds. The results reveal extensive variation in the amount of DNA gained via lineage-specific transposition, but that DNA loss counteracted this expansion to various extents across lineages. Our analysis of the rate and size spectrum of deletion events implies that DNA removal in both mammals and birds has proceeded mostly through large segmental deletions (>10 kb). These findings support a unified "accordion" model of genome size evolution in eukaryotes whereby DNA loss counteracting TE expansion is a major determinant of genome size. Furthermore, we propose that extensive DNA loss, and not necessarily a dearth of TE activity, has been the primary force maintaining the greater genomic compaction of flying birds and bats relative to their flightless relatives.
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22
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Sotero-Caio CG, Platt RN, Suh A, Ray DA. Evolution and Diversity of Transposable Elements in Vertebrate Genomes. Genome Biol Evol 2017; 9:161-177. [PMID: 28158585 PMCID: PMC5381603 DOI: 10.1093/gbe/evw264] [Citation(s) in RCA: 147] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/06/2016] [Indexed: 12/21/2022] Open
Abstract
Transposable elements (TEs) are selfish genetic elements that mobilize in genomes via transposition or retrotransposition and often make up large fractions of vertebrate genomes. Here, we review the current understanding of vertebrate TE diversity and evolution in the context of recent advances in genome sequencing and assembly techniques. TEs make up 4-60% of assembled vertebrate genomes, and deeply branching lineages such as ray-finned fishes and amphibians generally exhibit a higher TE diversity than the more recent radiations of birds and mammals. Furthermore, the list of taxa with exceptional TE landscapes is growing. We emphasize that the current bottleneck in genome analyses lies in the proper annotation of TEs and provide examples where superficial analyses led to misleading conclusions about genome evolution. Finally, recent advances in long-read sequencing will soon permit access to TE-rich genomic regions that previously resisted assembly including the gigantic, TE-rich genomes of salamanders and lungfishes.
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Affiliation(s)
| | - Roy N. Platt
- Department of Biological Sciences, Texas Tech University, Lubbock, TX
| | - Alexander Suh
- Department of Evolutionary Biology (EBC), Uppsala University, Uppsala, Sweden
| | - David A. Ray
- Department of Biological Sciences, Texas Tech University, Lubbock, TX
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23
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Ivancevic AM, Kortschak RD, Bertozzi T, Adelson DL. LINEs between Species: Evolutionary Dynamics of LINE-1 Retrotransposons across the Eukaryotic Tree of Life. Genome Biol Evol 2016; 8:3301-3322. [PMID: 27702814 PMCID: PMC5203782 DOI: 10.1093/gbe/evw243] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
LINE-1 (L1) retrotransposons are dynamic elements. They have the potential to cause great genomic change because of their ability to ‘jump’ around the genome and amplify themselves, resulting in the duplication and rearrangement of regulatory DNA. Active L1, in particular, are often thought of as tightly constrained, homologous and ubiquitous elements with well-characterized domain organization. For the past 30 years, model organisms have been used to define L1s as 6–8 kb sequences containing a 5′-UTR, two open reading frames working harmoniously in cis, and a 3′-UTR with a polyA tail. In this study, we demonstrate the remarkable and overlooked diversity of L1s via a comprehensive phylogenetic analysis of elements from over 500 species from widely divergent branches of the tree of life. The rapid and recent growth of L1 elements in mammalian species is juxtaposed against the diverse lineages found in other metazoans and plants. In fact, some of these previously unexplored mammalian species (e.g. snub-nosed monkey, minke whale) exhibit L1 retrotranspositional ‘hyperactivity’ far surpassing that of human or mouse. In contrast, non-mammalian L1s have become so varied that the current classification system seems to inadequately capture their structural characteristics. Our findings illustrate how both long-term inherited evolutionary patterns and random bursts of activity in individual species can significantly alter genomes, highlighting the importance of L1 dynamics in eukaryotes.
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Affiliation(s)
- Atma M Ivancevic
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia
| | - R Daniel Kortschak
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia
| | - Terry Bertozzi
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia.,Evolutionary Biology Unit, South Australian Museum, Adelaide, South Australia, Australia
| | - David L Adelson
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia
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24
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Warren IA, Naville M, Chalopin D, Levin P, Berger CS, Galiana D, Volff JN. Evolutionary impact of transposable elements on genomic diversity and lineage-specific innovation in vertebrates. Chromosome Res 2016; 23:505-31. [PMID: 26395902 DOI: 10.1007/s10577-015-9493-5] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Since their discovery, a growing body of evidence has emerged demonstrating that transposable elements are important drivers of species diversity. These mobile elements exhibit a great variety in structure, size and mechanisms of transposition, making them important putative actors in organism evolution. The vertebrates represent a highly diverse and successful lineage that has adapted to a wide range of different environments. These animals also possess a rich repertoire of transposable elements, with highly diverse content between lineages and even between species. Here, we review how transposable elements are driving genomic diversity and lineage-specific innovation within vertebrates. We discuss the large differences in TE content between different vertebrate groups and then go on to look at how they affect organisms at a variety of levels: from the structure of chromosomes to their involvement in the regulation of gene expression, as well as in the formation and evolution of non-coding RNAs and protein-coding genes. In the process of doing this, we highlight how transposable elements have been involved in the evolution of some of the key innovations observed within the vertebrate lineage, driving the group's diversity and success.
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Affiliation(s)
- Ian A Warren
- Institut de Génomique Fonctionnelle de Lyon, CNRS UMR5242, Ecole Normale Supérieure de Lyon, Lyon, France
| | - Magali Naville
- Institut de Génomique Fonctionnelle de Lyon, CNRS UMR5242, Ecole Normale Supérieure de Lyon, Lyon, France
| | - Domitille Chalopin
- Institut de Génomique Fonctionnelle de Lyon, CNRS UMR5242, Ecole Normale Supérieure de Lyon, Lyon, France.,Department of Genetics, University of Georgia, Athens, Georgia, 30602, USA
| | - Perrine Levin
- Institut de Génomique Fonctionnelle de Lyon, CNRS UMR5242, Ecole Normale Supérieure de Lyon, Lyon, France
| | - Chloé Suzanne Berger
- Institut de Génomique Fonctionnelle de Lyon, CNRS UMR5242, Ecole Normale Supérieure de Lyon, Lyon, France
| | - Delphine Galiana
- Institut de Génomique Fonctionnelle de Lyon, CNRS UMR5242, Ecole Normale Supérieure de Lyon, Lyon, France
| | - Jean-Nicolas Volff
- Institut de Génomique Fonctionnelle de Lyon, CNRS UMR5242, Ecole Normale Supérieure de Lyon, Lyon, France.
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25
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Li M, Yang LR, Xu G, Wu JP. Cloning and characterization of a novel lipase from Stenotrophomonas maltophilia GS11: The first member of a new bacterial lipase family XVI. J Biotechnol 2016; 228:30-36. [PMID: 27117245 DOI: 10.1016/j.jbiotec.2016.04.034] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 04/18/2016] [Accepted: 04/19/2016] [Indexed: 12/24/2022]
Abstract
Bacterial lipases are an important group of enzymes that offer enormous potential in organic synthesis, and there is considerable interest in identifying and developing novel bacterial lipases. In previous studies, strains of the genus Stenotrophomonas were proved to be potential source of lipases, but there is little genetic information describing lipase from the genus Stenotrophomonas. We have cloned and characterized a novel lipase (LipSM54), the first lipase described from the genus Stenotrophomonas. Enzymatic study showed that LipSM54 was a cold-active, solvent-tolerant and alkaline lipase. Using bioinformatics tools, LipSM54 was found to be related only to several putative lipases from different bacterial origins, none of which could be assigned to any previously described bacterial lipase family. LipSM54 and these related putative lipases share four conserved motifs around the catalytic residues. These motifs clearly distinguish them from the known bacterial lipase families. Consequently, LipSM54 is the first characterized member of the novel bacterial lipase family.
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Affiliation(s)
- Mu Li
- Key Laboratory of Environment Correlative Dietology, Huazhong Agricultural University, Ministry of Education, Wuhan, 430070, Hubei, People's Republic of China; College of Food Science and Technology, Huazhong Agricultural University, Wuhan, 430070, People's Republic of China; Institute of Bioengineering, Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, People's Republic of China
| | - Li-Rong Yang
- Institute of Bioengineering, Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, People's Republic of China
| | - Gang Xu
- Institute of Bioengineering, Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, People's Republic of China
| | - Jian-Ping Wu
- Institute of Bioengineering, Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, People's Republic of China.
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26
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Kelly LJ, Renny‐Byfield S, Pellicer J, Macas J, Novák P, Neumann P, Lysak MA, Day PD, Berger M, Fay MF, Nichols RA, Leitch AR, Leitch IJ. Analysis of the giant genomes of Fritillaria (Liliaceae) indicates that a lack of DNA removal characterizes extreme expansions in genome size. THE NEW PHYTOLOGIST 2015; 208:596-607. [PMID: 26061193 PMCID: PMC4744688 DOI: 10.1111/nph.13471] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Accepted: 04/20/2015] [Indexed: 05/18/2023]
Abstract
Plants exhibit an extraordinary range of genome sizes, varying by > 2000-fold between the smallest and largest recorded values. In the absence of polyploidy, changes in the amount of repetitive DNA (transposable elements and tandem repeats) are primarily responsible for genome size differences between species. However, there is ongoing debate regarding the relative importance of amplification of repetitive DNA versus its deletion in governing genome size. Using data from 454 sequencing, we analysed the most repetitive fraction of some of the largest known genomes for diploid plant species, from members of Fritillaria. We revealed that genomic expansion has not resulted from the recent massive amplification of just a handful of repeat families, as shown in species with smaller genomes. Instead, the bulk of these immense genomes is composed of highly heterogeneous, relatively low-abundance repeat-derived DNA, supporting a scenario where amplified repeats continually accumulate due to infrequent DNA removal. Our results indicate that a lack of deletion and low turnover of repetitive DNA are major contributors to the evolution of extremely large genomes and show that their size cannot simply be accounted for by the activity of a small number of high-abundance repeat families.
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Affiliation(s)
- Laura J. Kelly
- School of Biological and Chemical SciencesQueen Mary University of LondonLondonE1 4NSUK
- Jodrell LaboratoryRoyal Botanic GardensKewRichmondTW9 3DSUK
| | - Simon Renny‐Byfield
- School of Biological and Chemical SciencesQueen Mary University of LondonLondonE1 4NSUK
- Department of Plant SciencesUniversity of California DavisDavisCA95616USA
| | - Jaume Pellicer
- Jodrell LaboratoryRoyal Botanic GardensKewRichmondTW9 3DSUK
| | - Jiří Macas
- Biology Centre CASInstitute of Plant Molecular BiologyCZ‐37005České BudějoviceCzech Republic
| | - Petr Novák
- Biology Centre CASInstitute of Plant Molecular BiologyCZ‐37005České BudějoviceCzech Republic
| | - Pavel Neumann
- Biology Centre CASInstitute of Plant Molecular BiologyCZ‐37005České BudějoviceCzech Republic
| | - Martin A. Lysak
- Plant Cytogenomics Research GroupCEITEC – Central European Institute of TechnologyMasaryk UniversityKamenice 5CZ‐62500BrnoCzech Republic
| | - Peter D. Day
- School of Biological and Chemical SciencesQueen Mary University of LondonLondonE1 4NSUK
- Jodrell LaboratoryRoyal Botanic GardensKewRichmondTW9 3DSUK
| | - Madeleine Berger
- Jodrell LaboratoryRoyal Botanic GardensKewRichmondTW9 3DSUK
- School of Biological and Biomedical SciencesDurham UniversitySouth RoadDurhamDH1 3LEUK
- Rothamsted ResearchWest CommonHarpendenHertfordshireAL5 2JQUK
| | - Michael F. Fay
- Jodrell LaboratoryRoyal Botanic GardensKewRichmondTW9 3DSUK
| | - Richard A. Nichols
- School of Biological and Chemical SciencesQueen Mary University of LondonLondonE1 4NSUK
| | - Andrew R. Leitch
- School of Biological and Chemical SciencesQueen Mary University of LondonLondonE1 4NSUK
| | - Ilia J. Leitch
- Jodrell LaboratoryRoyal Botanic GardensKewRichmondTW9 3DSUK
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27
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Wang Y, Jiang F, Wang H, Song T, Wei Y, Yang M, Zhang J, Kang L. Evidence for the expression of abundant microRNAs in the locust genome. Sci Rep 2015; 5:13608. [PMID: 26329925 PMCID: PMC4556993 DOI: 10.1038/srep13608] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 07/30/2015] [Indexed: 12/20/2022] Open
Abstract
Substantial accumulation of neutral sequences accounts for genome size expansion in animal genomes. Numerous novel microRNAs (miRNAs), which evolve in a birth and death manner, are considered evolutionary neutral sequences. The migratory locust is an ideal model to determine whether large genomes contain abundant neutral miRNAs because of its large genome size. A total of 833 miRNAs were discovered, and several miRNAs were randomly chosen for validation by Northern blot and RIP-qPCR. Three additional verification methods, namely, processing-dependent methods of miRNA biogenesis using RNAi, evolutionary comparison with closely related species, and evidence supported by tissue-specific expression, were applied to provide compelling results that support the authenticity of locust miRNAs. We observed that abundant local duplication events of miRNAs, which were unique in locusts compared with those in other insects with small genome sizes, may be responsible for the substantial acquisition of miRNAs in locusts. Together, multiple evidence showed that the locust genome experienced a burst of miRNA acquisition, suggesting that genome size expansion may have considerable influences of miRNA innovation. These results provide new insight into the genomic dynamics of miRNA repertoires under genome size evolution.
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Affiliation(s)
- Yanli Wang
- Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi, China
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, China
| | - Feng Jiang
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, China
| | - Huimin Wang
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, China
| | - Tianqi Song
- Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi, China
| | - Yuanyuan Wei
- Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Meiling Yang
- Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Jianzhen Zhang
- Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi, China
| | - Le Kang
- Beijing Institutes of Life Science, Chinese Academy of Sciences, Beijing, China
- Institute of Zoology, Chinese Academy of Sciences, Beijing, China
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28
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Seear PJ, Rosato E, Goodall-Copestake WP, Barber I. The molecular evolution of spiggin nesting glue in sticklebacks. Mol Ecol 2015; 24:4474-88. [PMID: 26173374 PMCID: PMC4989455 DOI: 10.1111/mec.13317] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 07/06/2015] [Accepted: 07/09/2015] [Indexed: 11/26/2022]
Abstract
Gene duplication and subsequent divergence can lead to the evolution of new functions and lineage-specific traits. In sticklebacks, the successive duplication of a mucin gene (MUC19) into a tandemly arrayed, multigene family has enabled the production of copious amounts of 'spiggin', a secreted adhesive protein essential for nest construction. Here, we examine divergence between spiggin genes among three-spined sticklebacks (Gasterosteus aculeatus) from ancestral marine and derived freshwater populations, and propose underpinning gene duplication mechanisms. Sanger sequencing revealed substantial diversity among spiggin transcripts, including alternatively spliced variants and interchromosomal spiggin chimeric genes. Comparative analysis of the sequenced transcripts and all other spiggin genes in the public domain support the presence of three main spiggin lineages (spiggin A, spiggin B and spiggin C) with further subdivisions within spiggin B (B1, B2) and spiggin C (C1, C2). Spiggin A had diverged least from the ancestral MUC19, while the spiggin C duplicates had diversified most substantially. In silico translations of the spiggin gene open reading frames predicted that spiggins A and B are secreted as long mucin-like polymers, while spiggins C1 and C2 are secreted as short monomers, with putative antimicrobial properties. We propose that diversification of duplicated spiggin genes has facilitated local adaptation of spiggin to a range of aquatic habitats.
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Affiliation(s)
- P J Seear
- Department of Neuroscience, Psychology and Behaviour, College of Medicine, Biological Sciences and Psychology, University of Leicester, Leicester, LE1 7RH, UK
| | - E Rosato
- Department of Genetics, College of Medicine, Biological Sciences and Psychology, University of Leicester, Leicester, LE1 7RH, UK
| | | | - I Barber
- Department of Neuroscience, Psychology and Behaviour, College of Medicine, Biological Sciences and Psychology, University of Leicester, Leicester, LE1 7RH, UK
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29
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Henriet S, Sumic S, Doufoundou-Guilengui C, Jensen MF, Grandmougin C, Fal K, Thompson E, Volff JN, Chourrout D. Embryonic expression of endogenous retroviral RNAs in somatic tissues adjacent to the Oikopleura germline. Nucleic Acids Res 2015; 43:3701-11. [PMID: 25779047 PMCID: PMC4402516 DOI: 10.1093/nar/gkv169] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 02/20/2015] [Indexed: 11/19/2022] Open
Abstract
Selective pressure to maintain small genome size implies control of transposable elements, and most old classes of retrotransposons are indeed absent from the very compact genome of the tunicate Oikopleura dioica. Nonetheless, two families of retrotransposons are present, including the Tor elements. The gene organization within Tor elements is similar to that of LTR retrotransposons and retroviruses. In addition to gag and pol, many Tor elements carry a third gene encoding viral envelope-like proteins (Env) that may mediate infection. We show that the Tor family contains distinct classes of elements. In some classes, env mRNA is transcribed from the 5′LTR as in retroviruses. In others, env is transcribed from an additional promoter located downstream of the 5′LTR. Tor Env proteins are membrane-associated glycoproteins which exhibit some features of viral membrane fusion proteins. Whereas some elements are expressed in the adult testis, many others are specifically expressed in embryonic somatic cells adjacent to primordial germ cells. Such embryonic expression depends on determinants present in the Tor elements and not on their surrounding genomic environment. Our study shows that unusual modes of transcription and expression close to the germline may contribute to the proliferation of Tor elements.
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Affiliation(s)
- Simon Henriet
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway
| | - Sara Sumic
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway
| | | | - Marit Flo Jensen
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway
| | - Camille Grandmougin
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway
| | - Kateryna Fal
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway
| | - Eric Thompson
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway Department of Biology, University of Bergen, Bergen, N-5020, Norway
| | - Jean-Nicolas Volff
- Institut de Génomique Fonctionnelle de Lyon, Ecole Normale Supérieure de Lyon - CNRS UMR 5242 - INRA USC 1370, Lyon, 69364 Lyon cedex 07, France
| | - Daniel Chourrout
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway
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30
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Frahry MB, Sun C, Chong RA, Mueller RL. Low levels of LTR retrotransposon deletion by ectopic recombination in the gigantic genomes of salamanders. J Mol Evol 2015; 80:120-9. [PMID: 25608479 DOI: 10.1007/s00239-014-9663-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 12/30/2014] [Indexed: 11/25/2022]
Abstract
Across the tree of life, species vary dramatically in nuclear genome size. Mutations that add or remove sequences from genomes-insertions or deletions, or indels-are the ultimate source of this variation. Differences in the tempo and mode of insertion and deletion across taxa have been proposed to contribute to evolutionary diversity in genome size. Among vertebrates, most of the largest genomes are found within the salamanders, an amphibian clade with genome sizes ranging from ~14 to ~120 Gb. Salamander genomes have been shown to experience slower rates of DNA loss through small (i.e., <30 bp) deletions than do other vertebrate genomes. However, no studies have addressed DNA loss from salamander genomes resulting from larger deletions. Here, we focus on one type of large deletion-ectopic-recombination-mediated removal of LTR retrotransposon sequences. In ectopic recombination, double-strand breaks are repaired using a "wrong" (i.e., ectopic, or non-allelic) template sequence-typically another locus of similar sequence. When breaks occur within the LTR portions of LTR retrotransposons, ectopic-recombination-mediated repair can produce deletions that remove the internal transposon sequence and the equivalent of one of the two LTR sequences. These deletions leave a signature in the genome-a solo LTR sequence. We compared levels of solo LTRs in the genomes of four salamander species with levels present in five vertebrates with smaller genomes. Our results demonstrate that salamanders have low levels of solo LTRs, suggesting that ectopic-recombination-mediated deletion of LTR retrotransposons occurs more slowly than in other vertebrates with smaller genomes.
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Affiliation(s)
- Matthew Blake Frahry
- Department of Biology, Colorado State University, Fort Collins, CO, 80523-1878, USA
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31
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Chalopin D, Naville M, Plard F, Galiana D, Volff JN. Comparative analysis of transposable elements highlights mobilome diversity and evolution in vertebrates. Genome Biol Evol 2015; 7:567-80. [PMID: 25577199 PMCID: PMC4350176 DOI: 10.1093/gbe/evv005] [Citation(s) in RCA: 225] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Transposable elements (TEs) are major components of vertebrate genomes, with major roles in genome architecture and evolution. In order to characterize both common patterns and lineage-specific differences in TE content and TE evolution, we have compared the mobilomes of 23 vertebrate genomes, including 10 actinopterygian fish, 11 sarcopterygians, and 2 nonbony vertebrates. We found important variations in TE content (from 6% in the pufferfish tetraodon to 55% in zebrafish), with a more important relative contribution of TEs to genome size in fish than in mammals. Some TE superfamilies were found to be widespread in vertebrates, but most elements showed a more patchy distribution, indicative of multiple events of loss or gain. Interestingly, loss of major TE families was observed during the evolution of the sarcopterygian lineage, with a particularly strong reduction in TE diversity in birds and mammals. Phylogenetic trends in TE composition and activity were detected: Teleost fish genomes are dominated by DNA transposons and contain few ancient TE copies, while mammalian genomes have been predominantly shaped by nonlong terminal repeat retrotransposons, along with the persistence of older sequences. Differences were also found within lineages: The medaka fish genome underwent more recent TE amplification than the related platyfish, as observed for LINE retrotransposons in the mouse compared with the human genome. This study allows the identification of putative cases of horizontal transfer of TEs, and to tentatively infer the composition of the ancestral vertebrate mobilome. Taken together, the results obtained highlight the importance of TEs in the structure and evolution of vertebrate genomes, and demonstrate their major impact on genome diversity both between and within lineages.
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Affiliation(s)
- Domitille Chalopin
- Institut de Génomique Fonctionnelle de Lyon, Ecole Normale Supérieure de Lyon, Centre National de la Recherche Scientifique UMR5242, Université Claude Bernard Lyon 1, Lyon Cedex 07, France
| | - Magali Naville
- Institut de Génomique Fonctionnelle de Lyon, Ecole Normale Supérieure de Lyon, Centre National de la Recherche Scientifique UMR5242, Université Claude Bernard Lyon 1, Lyon Cedex 07, France
| | - Floriane Plard
- Laboratoire "Biométrie et Biologie Évolutive," Unité Mixte de Recherche 5558, Université Claude Bernard Lyon 1, Lyon, France
| | - Delphine Galiana
- Institut de Génomique Fonctionnelle de Lyon, Ecole Normale Supérieure de Lyon, Centre National de la Recherche Scientifique UMR5242, Université Claude Bernard Lyon 1, Lyon Cedex 07, France
| | - Jean-Nicolas Volff
- Institut de Génomique Fonctionnelle de Lyon, Ecole Normale Supérieure de Lyon, Centre National de la Recherche Scientifique UMR5242, Université Claude Bernard Lyon 1, Lyon Cedex 07, France
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32
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Tollis M, Boissinot S. Lizards and LINEs: selection and demography affect the fate of L1 retrotransposons in the genome of the green anole (Anolis carolinensis). Genome Biol Evol 2014; 5:1754-68. [PMID: 24013105 PMCID: PMC3787681 DOI: 10.1093/gbe/evt133] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Autonomous retrotransposons lacking long terminal repeats (LTR) account for much of the variation in genome size and structure among vertebrates. Mammalian genomes contain hundreds of thousands of non-LTR retrotransposon copies, mostly resulting from the amplification of a single clade known as L1. The genomes of teleost fish and squamate reptiles contain a much more diverse array of non-LTR retrotransposon families, whereas copy number is relatively low. The majority of non-LTR retrotransposon insertions in nonmammalian vertebrates also appear to be very recent, suggesting strong purifying selection limits the accumulation of non-LTR retrotransposon copies. It is however unclear whether this turnover model, originally proposed in Drosophila, applies to nonmammalian vertebrates. Here, we studied the population dynamics of L1 in the green anole lizard (Anolis carolinensis). We found that although most L1 elements are recent in this genome, truncated insertions accumulate readily, and many are fixed at both the population and species level. In contrast, full-length L1 insertions are found at lower population frequencies, suggesting that the turnover model only applies to longer L1 elements in Anolis. We also found that full-length L1 inserts are more likely to be fixed in populations of small effective size, suggesting that the strength of purifying selection against deleterious alleles is highly dependent on host demographic history. Similar mechanisms seem to be controlling the fate of non-LTR retrotransposons in both Anolis and teleostean fish, which suggests that mammals have considerably diverged from the ancestral vertebrate in terms of how they interact with their intragenomic parasites.
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Affiliation(s)
- Marc Tollis
- Biology Department, Queens College, City University of New York, Flushing
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33
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Lavoie CA, Platt RN, Novick PA, Counterman BA, Ray DA. Transposable element evolution in Heliconius suggests genome diversity within Lepidoptera. Mob DNA 2013; 4:21. [PMID: 24088337 PMCID: PMC4016481 DOI: 10.1186/1759-8753-4-21] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 09/27/2013] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Transposable elements (TEs) have the potential to impact genome structure, function and evolution in profound ways. In order to understand the contribution of transposable elements (TEs) to Heliconius melpomene, we queried the H. melpomene draft sequence to identify repetitive sequences. RESULTS We determined that TEs comprise ~25% of the genome. The predominant class of TEs (~12% of the genome) was the non-long terminal repeat (non-LTR) retrotransposons, including a novel SINE family. However, this was only slightly higher than content derived from DNA transposons, which are diverse, with several families having mobilized in the recent past. Compared to the only other well-studied lepidopteran genome, Bombyx mori, H. melpomene exhibits a higher DNA transposon content and a distinct repertoire of retrotransposons. We also found that H. melpomene exhibits a high rate of TE turnover with few older elements accumulating in the genome. CONCLUSIONS Our analysis represents the first complete, de novo characterization of TE content in a butterfly genome and suggests that, while TEs are able to invade and multiply, TEs have an overall deleterious effect and/or that maintaining a small genome is advantageous. Our results also hint that analysis of additional lepidopteran genomes will reveal substantial TE diversity within the group.
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Affiliation(s)
- Christine A Lavoie
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State, MS 39762, USA
- Institute for Genomics, Biocomputing and Biotechnology, Mississippi, MS 39762, USA
| | - Roy N Platt
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State, MS 39762, USA
- Institute for Genomics, Biocomputing and Biotechnology, Mississippi, MS 39762, USA
| | - Peter A Novick
- Department of Biological Sciences and Geology, Queensborough Community College, Bayside, New York, NY 11364, USA
| | | | - David A Ray
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State, MS 39762, USA
- Institute for Genomics, Biocomputing and Biotechnology, Mississippi, MS 39762, USA
- Current Address: Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA
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34
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Schneider CH, Gross MC, Terencio ML, do Carmo EJ, Martins C, Feldberg E. Evolutionary dynamics of retrotransposable elements Rex1, Rex3 and Rex6 in neotropical cichlid genomes. BMC Evol Biol 2013; 13:152. [PMID: 23865932 PMCID: PMC3728117 DOI: 10.1186/1471-2148-13-152] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 07/15/2013] [Indexed: 01/27/2023] Open
Abstract
Background Transposable elements (TEs) have the potential to produce broad changes in the genomes of their hosts, acting as a type of evolutionary toolbox and generating a collection of new regulatory and coding sequences. Several TE classes have been studied in Neotropical cichlids; however, the information gained from these studies is restricted to the physical chromosome mapping, whereas the genetic diversity of the TEs remains unknown. Therefore, the genomic organization of the non-LTR retrotransposons Rex1, Rex3, and Rex6 in five Amazonian cichlid species was evaluated using physical chromosome mapping and DNA sequencing to provide information about the role of TEs in the evolution of cichlid genomes. Results Physical mapping revealed abundant TE clusters dispersed throughout the chromosomes. Furthermore, several species showed conspicuous clusters accumulation in the centromeric and terminal portions of the chromosomes. These TE chromosomal sites are associated with both heterochromatic and euchromatic regions. A higher number of Rex1 clusters were observed among the derived species. The Rex1 and Rex3 nucleotide sequences were more conserved in the basal species than in the derived species; however, this pattern was not observed in Rex6. In addition, it was possible to observe conserved blocks corresponding to the reverse transcriptase fragment of the Rex1 and Rex3 clones and to the endonuclease of Rex6. Conclusion Our data showed no congruence between the Bayesian trees generated for Rex1, Rex3 and Rex6 of cichlid species and phylogenetic hypothesis described for the group. Rex1 and Rex3 nucleotide sequences were more conserved in the basal species whereas Rex6 exhibited high substitution rates in both basal and derived species. The distribution of Rex elements in cichlid genomes suggests that such elements are under the action of evolutionary mechanisms that lead to their accumulation in particular chromosome regions, mostly in heterochromatins.
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Affiliation(s)
- Carlos Henrique Schneider
- Laboratório de Genética Animal, Instituto Nacional de Pesquisas da Amazônia, Av. André Araújo, 2936, Petrópolis, 69011-970, Manaus, Amazonas, Brazil.
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35
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Sun C, López Arriaza JR, Mueller RL. Slow DNA loss in the gigantic genomes of salamanders. Genome Biol Evol 2013; 4:1340-8. [PMID: 23175715 PMCID: PMC3542557 DOI: 10.1093/gbe/evs103] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Evolutionary changes in genome size result from the combined effects of mutation, natural
selection, and genetic drift. Insertion and deletion mutations (indels) directly impact
genome size by adding or removing sequences. Most species lose more DNA through small
indels (i.e., ∼1–30 bp) than they gain, which can result in genome reduction
over time. Because this rate of DNA loss varies across species, small indel dynamics have
been suggested to contribute to genome size evolution. Species with extremely large
genomes provide interesting test cases for exploring the link between small indels and
genome size; however, most large genomes remain relatively unexplored. Here, we examine
rates of DNA loss in the tetrapods with the largest genomes—the salamanders. We used
low-coverage genomic shotgun sequence data from four salamander species to examine
patterns of insertion, deletion, and substitution in neutrally evolving non-long terminal
repeat (LTR) retrotransposon sequences. For comparison, we estimated genome-wide DNA loss
rates in non-LTR retrotransposon sequences from five other vertebrate genomes:
Anolis carolinensis, Danio rerio, Gallus
gallus, Homo sapiens, and Xenopus tropicalis.
Our results show that salamanders have significantly lower rates of DNA loss than do other
vertebrates. More specifically, salamanders experience lower numbers of deletions relative
to insertions, and both deletions and insertions are skewed toward smaller sizes. On the
basis of these patterns, we conclude that slow DNA loss contributes to genomic gigantism
in salamanders. We also identify candidate molecular mechanisms underlying these
differences and suggest that natural variation in indel dynamics provides a unique
opportunity to study the basis of genome stability.
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Affiliation(s)
- Cheng Sun
- Department of Biology, Colorado State University, CO, USA
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36
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Kitano J, Yoshida K, Suzuki Y. RNA sequencing reveals small RNAs differentially expressed between incipient Japanese threespine sticklebacks. BMC Genomics 2013; 14:214. [PMID: 23547919 PMCID: PMC3637797 DOI: 10.1186/1471-2164-14-214] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Accepted: 03/20/2013] [Indexed: 01/01/2023] Open
Abstract
Background Non-coding small RNAs, ranging from 20 to 30 nucleotides in length, mediate the regulation of gene expression and play important roles in many biological processes. One class of small RNAs, microRNAs (miRNAs), are highly conserved across taxa and mediate the regulation of the chromatin state and the post-transcriptional regulation of messenger RNA (mRNA). Another class of small RNAs is the Piwi-interacting RNAs, which play important roles in the silencing of transposons and other functional genes. Although the biological functions of the different small RNAs have been elucidated in several laboratory animals, little is known regarding naturally occurring variation in small RNA transcriptomes among closely related species. Results We employed next-generation sequencing technology to compare the expression profiles of brain small RNAs between sympatric species of the Japanese threespine stickleback (Gasterosteus aculeatus). We identified several small RNAs that were differentially expressed between sympatric Pacific Ocean and Japan Sea sticklebacks. Potential targets of several small RNAs were identified as repetitive sequences. Female-biased miRNA expression from the old X chromosome was also observed, and it was attributed to the degeneration of the Y chromosome. Conclusions Our results suggest that expression patterns of small RNA can differ between incipient species and may be a potential mechanism underlying differential mRNA expression and transposon activity.
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Affiliation(s)
- Jun Kitano
- Ecological Genetics Laboratory, National Institute of Genetics, Yata 1111, Mishima, Shizuoka, Japan.
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