| 61. |
- Künstner, Axel, et al.
(författare)
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Significant Selective Constraint at 4-Fold Degenerate Sites in the Avian Genome and Its Consequence for Detection of Positive Selection
- 2011
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Ingår i: Genome Biology and Evolution. - : Oxford University Press (OUP). - 1759-6653 .- 1759-6653. ; 3, s. 1381-1389
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Tidskriftsartikel (refereegranskat)abstract
- A major conclusion from comparative genomics is that many sequences that do not code for proteins are conserved beyond neutral expectations, indicating that they evolve under the influence of purifying selection and are likely to have functional roles. Due to the degeneracy of the genetic code, synonymous sites within protein-coding genes have previously been seen as "silent" with respect to function and thereby invisible to selection. However, there are indications that synonymous sites of vertebrate genomes are also subject to selection and this is not necessarily because of potential codon bias. We used divergence in ancestral repeats as a neutral reference to estimate the constraint on 4-fold degenerate sites of avian genes in a whole-genome approach. In the pairwise comparison of chicken and zebra finch, constraint was estimated at 24-32%. Based on three-species alignments of chicken, turkey, and zebra finch, lineage-specific estimates of constraint were 43%, 29%, and 24%, respectively. The finding of significant constraint at 4-fold degenerate sites from data on interspecific divergence was replicated in an analysis of intraspecific diversity in the chicken genome. These observations corroborate recent data from mammalian genomes and call for a reappraisal of the use of synonymous substitution rates as neutral standards in molecular evolutionary analysis, for example, in the use of the well-known d(N)/d(S) ratio and in inferences on positive selection. We show by simulations that the rate of false positives in the detection of positively selected genes and sites increases several-fold at the levels of constraint at 4-fold degenerate sites found in this study.
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| 62. |
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| 63. |
- Laine, Veronika N., et al.
(författare)
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Whole-genome Analysis Reveals Contrasting Relationships Among Nuclear and Mitochondrial Genomes Between Three Sympatric Bat Species
- 2023
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Ingår i: Genome Biology and Evolution. - : Oxford University Press (OUP). - 1759-6653. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Understanding mechanisms involved in speciation can be challenging, especially when hybridization or introgression blurs species boundaries. In bats, resolving relationships of some closely related groups has proved difficult due subtle interspecific variation both in morphometrics and molecular data sets. The endemic South American Histiotus bats, currently considered a subgenus of Eptesicus, harbor unresolved phylogenetic relationships and of those is a trio consisting of two closely related species: Eptesicus (Histiotus) macrotus and Eptesicus (Histiotus) montanus, and their relationship with a third, Eptesicus (Histiotus) magellanicus. The three sympatric species bear marked resemblance to each other, but can be differentiated morphologically. Furthermore, previous studies have been unable to differentiate the species from each other at a molecular level. In order to disentangle the phylogenetic relationships of these species, we examined the differentiation patterns and evolutionary history of the three Eptesicus (H.) species at the whole-genome level. The nuclear DNA statistics between the species suggest strong gene flow and recent hybridization between E. (H.) montanus and E. (H.) macrotus, whereas E. (H.) magellanicus shows a higher degree of isolation. In contrast, mitochondrial DNA shows a closer relationship between E. (H.) magellanicus and E. (H.) montanus. Opposing patterns in mtDNA and nuclear markers are often due to differences in dispersal, and here it could be both as a result of isolation in refugia during the last glacial maximum and female philopatry and male-biased dispersal. In conclusion, this study shows the importance of both the nuclear and mitochondrial DNA in resolving phylogenetic relationships and species histories.
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| 64. |
- Li, Zhen, et al.
(författare)
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Single-Copy Genes as Molecular Markers for Phylogenomic Studies in Seed Plants
- 2017
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Ingår i: Genome Biology and Evolution. - : Oxford University Press. - 1759-6653 .- 1759-6653. ; 9:5, s. 1130-1147
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Tidskriftsartikel (refereegranskat)abstract
- Phylogenetic relationships among seed plant taxa, especially within the gymnosperms, remain contested. In contrast to angio-sperms, for which several genomic, transcriptomic and phylogenetic resources are available, there are few, if any, molecular markers that allow broad comparisons among gymnosperm species. With few gymnosperm genomes available, recently obtained transcriptomes in gymnosperms are a great addition to identifying single-copy gene families as molecular markers for phylogenomic analysis in seed plants. Taking advantage of an increasing number of available genomes and transcriptomes, we identified single-copy genes in a broad collection of seed plants and used these to infer phylogenetic relationships between major seed plant taxa. This study aims at extending the current phylogenetic toolkit for seed plants, assessing its ability for resolving seed plant phylogeny, and discussing potential factors affecting phylogenetic reconstruction. In total, we identified 3,072 single-copy genes in 31 gymnosperms and 2,156 single-copy genes in 34 angiosperms. All studied seed plants shared 1,469 single-copy genes, which are generally involved in functions like DNA metabolism, cell cycle, and photosynthesis. A selected set of 106 single-copy genes provided good resolution for the seed plant phylogeny except for gnetophytes. Although some of our analyses support a sister relationship between gnetophytes and other gymnosperms, phylogenetic trees from concatenated alignments without 3rd codon positions and amino acid alignments under the CAT + GTR model, support gnetophytes as a sister group to Pinaceae. Our phylogenomic analyses demonstrate that, in general, single-copy genes can uncover both recent and deep divergences of seed plant phylogeny.
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| 65. |
- Linde, Anna-Malin, et al.
(författare)
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Genome Evolution in Plants: Complex Thalloid Liverworts (Marchantiopsida)
- 2023
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Ingår i: Genome Biology and Evolution. - : Oxford University Press (OUP). - 1759-6653. ; 15:3
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Tidskriftsartikel (refereegranskat)abstract
- Why do some genomes stay small and simple, while others become huge, and why are some genomes more stable? In contrast to angiosperms and gymnosperms, liverworts are characterized by small genomes with low variation in size and conserved chromosome numbers. We quantified genome evolution among five Marchantiophyta (liverworts), measuring gene characteristics, transposable element (TE) landscape, collinearity, and sex chromosome evolution that might explain the small size and limited variability of liverwort genomes. No genome duplications were identified among examined liverworts and levels of duplicated genes are low. Among the liverwort species, Lunularia cruciata stands out with a genome size almost twice that of the other liverwort species investigated here, and most of this increased size is due to bursts of Ty3/Gypsy retrotransposons. Intrachromosomal rearrangements between examined liverworts are abundant but occur at a slower rate compared with angiosperms. Most genes on L. cruciata scaffolds have their orthologs on homologous Marchantia polymorpha chromosomes, indicating a low degree of rearrangements between chromosomes. Still, translocation of a fragment of the female U chromosome to an autosome was predicted from our data, which might explain the uniquely small U chromosome in L. cruciata. Low levels of gene duplication, TE activity, and chromosomal rearrangements might contribute to the apparent slow rate of morphological evolution in liverworts.
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| 66. |
- Liu, Yang, et al.
(författare)
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Genome Assembly of the Common Pheasant Phasianus colchicus : A Model for Speciation and Ecological Genomics
- 2019
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Ingår i: Genome Biology and Evolution. - : Oxford University Press (OUP). - 1759-6653 .- 1759-6653. ; 11:12, s. 3326-3331
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Tidskriftsartikel (refereegranskat)abstract
- The commonpheasant (Phasianus colchicus) in the order Galliformes and the family Phasianidae, has 30 subspecies distributed across its native range in the Palearctic realm and has been introduced to Europe, NorthAmerica, and Australia. It is an important game bird often subjected to wildlife management as well as a model species to study speciation, biogeography, and local adaptation. However, the genomic resources for the commonpheasant are generally lacking. We sequenced a male individual of the subspecies torquatus of the common pheasant with the Illumina HiSeq platform. We obtained 94.88Gb of usable sequences by filtering out low-quality reads of the raw data generated. This resulted in a 1.02Gb final assembly, which equals the estimated genome size. BUSCO analysis using chicken as a model showed that 93.3% of genes were complete. The contig N50 and scaffold N50 sizes were 178 kb and 10.2 Mb, respectively. All these indicate that we obtained a high-quality genome assembly. We annotated 16,485 protein-coding genes and 123.3 Mb (12.05% of the genome) of repetitive sequences by ab initio and homology-based prediction. Furthermore, we applied a RAD-sequencing approach for another 45 individuals of seven representative subspecies in China and identified 4,376,351 novel single nucleotide polymorphism (SNPs) markers. Using this unprecedented data set, we uncovered the geographic population structure and genetic introgression among common pheasants in China. Our results provide the first high-quality reference genome for the common pheasant and a valuable genome-wide SNP database for studying population genomics and demographic history.
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| 67. |
- Mafessoni, Fabrizio, et al.
(författare)
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Turning vice into virtue : Using Batch-Effects to Detect Errors in Large Genomic Datasets
- 2018
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Ingår i: Genome Biology and Evolution. - : Oxford University Press (OUP). - 1759-6653. ; 10:10, s. 2697-2708
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Tidskriftsartikel (refereegranskat)abstract
- It is often unavoidable to combine data from different sequencing centers or sequencing platforms when compiling datasets with a large number of individuals. However, the different data are likely to contain specific systematic errors that will appear as SNPs. Here, we devise a method to detect systematic errors in combined datasetIs. To measure quality differences between individual genomes, we study pairs of variants that reside on different chromosomes and co-occur in individuals. The abundance of these pairs of variants in different genomes is then used to detect systematic errors due to batch effects. Applying our method to the 1000 Genomes dataset, we find that coding regions are enriched for errors, where about 1% of the higher-frequency variants are predicted to be erroneous, whereas errors outside of coding regions are much rarer (<0.001%).As expected, predicted errors are found less often than other variants in a dataset that was generated with a different sequencing technology, indicating that many of the candidates are indeed errors. However, predicted 1000 Genomes errors are also found in other large datasets; our observation is thus not specific to the 1000 Genomes dataset. Our results show that batch effects can be turned into a virtue by using the resulting variation in large scale datasets to detect systematic errors.
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| 68. |
- Mahajan, Mayank, et al.
(författare)
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Evolutionary Remodeling of the Cell Envelope in Bacteria of the Planctomycetes Phylum
- 2020
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Ingår i: Genome Biology and Evolution. - : Oxford University Press (OUP). - 1759-6653 .- 1759-6653. ; 12:9, s. 1528-1548
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Tidskriftsartikel (refereegranskat)abstract
- Bacteria of the Planctomycetes phylum have many unique cellular features, such as extensive membrane invaginations and the ability to import macromolecules. These features raise intriguing questions about the composition of their cell envelopes. In this study, we have used microscopy, phylogenomics, and proteomics to examine the composition and evolution of cell envelope proteins in Tuwongella immobilis and other members of the Planctomycetes. Cryo-electron tomography data indicated a distance of 45 nm between the inner and outer membranes in T. immobilis. Consistent with the wide periplasmic space, our bioinformatics studies showed that the periplasmic segments of outer-membrane proteins in type II secretion systems are extended in bacteria of the order Planctomycetales. Homologs of two highly abundant cysteine-rich cell wall proteins in T. immobilis were identified in all members of the Planctomycetales, whereas genes for peptidoglycan biosynthesis and cell elongation have been lost in many members of this bacterial group. The cell wall proteins contain multiple copies of the YTV motif, which is the only domain that is conserved and unique to the Planctomycetales. Earlier diverging taxa in the Planctomycetes phylum contain genes for peptidoglycan biosynthesis but no homologs to the YTV cell wall proteins. The major remodeling of the cell envelope in the ancestor of the Planctomycetales coincided with the emergence of budding and other unique cellular phenotypes. The results have implications for hypotheses about the process whereby complex cellular features evolve in bacteria.
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| 69. |
- Makino, Takashi, et al.
(författare)
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Elevated proportions of deleterious genetic variation in domestic animals and plants
- 2018
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Ingår i: Genome Biology and Evolution. - : Oxford University Press. - 1759-6653 .- 1759-6653. ; 10:1, s. 276-290
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Tidskriftsartikel (refereegranskat)abstract
- A fraction of genetic variants segregating in any population are deleterious, which negatively impacts individual fitness. The domestication of animals and plants is associated with population bottlenecks and artificial selection, which are predicted to increase the proportion of deleterious variants. However, the extent to which this is a general feature of domestic species is unclear. Here we examine the effects of domestication on the prevalence of deleterious variation using pooled whole-genome resequencing data from five domestic animal species (dog, pig, rabbit, chicken and silkworm) and two domestic plant species (rice and soybean) compared to their wild ancestors. We find significantly reduced genetic variation and increased proportion of nonsynonymous amino acid changes in all but one of the domestic species. These differences are observable across a range of allele frequencies, both common and rare. We find proportionally more SNPs in highly conserved elements in domestic species and a tendency for domestic species to harbour a higher proportion of changes classified as damaging. Our findings most likely reflect an increased incidence of deleterious variants in domestic species, which is most likely attributable to population bottlenecks that lead to a reduction in the efficacy of selection. An exception to this pattern is displayed by European domestic pigs, which do not show traces of a strong population bottleneck and probably continued to exchange genes with wild boar populations after domestication. The results presented here indicate that an elevated proportion of deleterious variants is a common, but not ubiquitous, feature of domestic species.
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| 70. |
- Morrow, Jennifer L., et al.
(författare)
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Parallel Sequencing of Wolbachia wCer2 from Donor and Novel Hosts Reveals Multiple Incompatibility Factors and Genome Stability after Host Transfers
- 2020
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Ingår i: Genome Biology and Evolution. - : OXFORD UNIV PRESS. - 1759-6653 .- 1759-6653. ; 12:5, s. 720-735
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Tidskriftsartikel (refereegranskat)abstract
- The application of Wolbachia in insect pest and vector control requires the establishment of genotypically stable host associations. The cytoplasmic incompatibility (CI) inducing Wolbachia strain wCer2 naturally occurs in the cherry fruit fly Rhagoletis cerasi as co-infection with other strains and was transferred to other fruit fly species by embryonic microinjections. We obtained wCer2 genome data from its native and three novel hosts, Drosophila simulans, Drosophila melanogaster, and Ceratitis capitata and assessed its genome stability, characteristics, and CI factor (cit) genes. De novo assembly was successful from Wolbachia cell-enriched singly infected D. simulans embryos, with minimal host and other bacterial genome traces. The lowyield of Wolbachia sequence reads from total genomic extracts of one multiply infected R. cerasi pupa and one singly infected C. capitata adult limited de novo assemblies but was sufficient for comparative analyses. Across hosts wCer2 was stable in genome synteny and content. Polymorphic nucleotide sites were found in wCer2 of each host; however, only one nucleotide was different between R. cerasi and C capitata, and none between replicated D. simulans lines. The wCer2 genome is highly similar to wAu (D. simulans), wMel (D. melanogaster), and wRec (Drosophila recens). In contrast to wMel and wRec (each with one cif gene pair) and wAu (without any cif genes), wCer2 has three pairs of Type I cif genes, and one Type V cifB gene without a cifA complement. This may explain previously reported CI patterns of wCer2, including incomplete rescue of its own CI modification in three novel host species.
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