1
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Horton JS, Taylor TB. Mutation bias and adaptation in bacteria. MICROBIOLOGY (READING, ENGLAND) 2023; 169. [PMID: 37943288 DOI: 10.1099/mic.0.001404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
Genetic mutation, which provides the raw material for evolutionary adaptation, is largely a stochastic force. However, there is ample evidence showing that mutations can also exhibit strong biases, with some mutation types and certain genomic positions mutating more often than others. It is becoming increasingly clear that mutational bias can play a role in determining adaptive outcomes in bacteria in both the laboratory and the clinic. As such, understanding the causes and consequences of mutation bias can help microbiologists to anticipate and predict adaptive outcomes. In this review, we provide an overview of the mechanisms and features of the bacterial genome that cause mutational biases to occur. We then describe the environmental triggers that drive these mechanisms to be more potent and outline the adaptive scenarios where mutation bias can synergize with natural selection to define evolutionary outcomes. We conclude by describing how understanding mutagenic genomic features can help microbiologists predict areas sensitive to mutational bias, and finish by outlining future work that will help us achieve more accurate evolutionary forecasts.
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Affiliation(s)
- James S Horton
- Milner Centre for Evolution, Department of Life Sciences, University of Bath, BA2 7AY, UK
| | - Tiffany B Taylor
- Milner Centre for Evolution, Department of Life Sciences, University of Bath, BA2 7AY, UK
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2
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Beura PK, Sen P, Aziz R, Satapathy SS, Ray SK. Transcribed intergenic regions exhibit a lower frequency of nucleotide polymorphism than the untranscribed intergenic regions in the genomes of Escherichia coli and Salmonella enterica. J Genet 2023. [DOI: 10.1007/s12041-023-01418-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
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3
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Aziz R, Sen P, Beura PK, Das S, Tula D, Dash M, Namsa ND, Deka RC, Feil EJ, Satapathy SS, Ray SK. Incorporation of transition to transversion ratio and nonsense mutations, improves the estimation of the number of synonymous and non-synonymous sites in codons. DNA Res 2022; 29:6654588. [PMID: 35920776 PMCID: PMC9358017 DOI: 10.1093/dnares/dsac023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Indexed: 11/12/2022] Open
Abstract
Abstract
A common approach to estimate the strength and direction of selection acting on protein coding sequences is to calculate the dN/dS ratio. The method to calculate dN/dS has been widely used by many researchers and many critical reviews have been made on its application after the proposition by Nei and Gojobori in 1986. However, the method is still evolving considering the non-uniform substitution rates and pretermination codons. In our study of SNPs in 586 genes across 156 Escherichia coli strains, synonymous polymorphism in 2-fold degenerate codons were higher in comparison to that in 4-fold degenerate codons, which could be attributed to the difference between transition (Ti) and transversion (Tv) substitution rates where the average rate of a transition is four times more than that of a transversion in general. We considered both the Ti/Tv ratio, and nonsense mutation in pretermination codons, to improve estimates of synonymous (S) and non-synonymous (NS) sites. The accuracy of estimating dN/dS has been improved by considering the Ti/Tv ratio and nonsense substitutions in pretermination codons. We showed that applying the modified approach based on Ti/Tv ratio and pretermination codons results in higher values of dN/dS in 29 common genes of equal reading-frames between E. coli and Salmonella enterica. This study emphasizes the robustness of amino acid composition with varying codon degeneracy, as well as the pretermination codons when calculating dN/dS values.
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Affiliation(s)
- Ruksana Aziz
- Department of Molecular Biology and Biotechnology, Tezpur University , Tezpur, 784028 Assam, India
| | - Piyali Sen
- Department of Computer Science and Engineering, Tezpur University , Tezpur, 784028 Assam, India
| | - Pratyush Kumar Beura
- Department of Molecular Biology and Biotechnology, Tezpur University , Tezpur, 784028 Assam, India
| | - Saurav Das
- Department of Molecular Biology and Biotechnology, Tezpur University , Tezpur, 784028 Assam, India
| | - Debapriya Tula
- TCS Innovation, Tata Consultancy Services , Hyderabad, 500081 Telangana, India
| | - Madhusmita Dash
- Department of Electronics and Communication Engineering, NIT , Papum Pare, 791113 Arunachal Pradesh, India
| | - Nima Dondu Namsa
- Department of Molecular Biology and Biotechnology, Tezpur University , Tezpur, 784028 Assam, India
- Center for Multidisciplinary Research, Tezpur University , Tezpur, 784028 Assam, India
| | - Ramesh Chandra Deka
- Center for Multidisciplinary Research, Tezpur University , Tezpur, 784028 Assam, India
- Department of Chemical Sciences, Tezpur University , Tezpur, 784028 Assam, India
| | - Edward J Feil
- Department of Biology and Biochemistry, The Milner Centre for Evolution, University of Bath , Bath BA2 7AY, UK
| | - Siddhartha Sankar Satapathy
- Department of Computer Science and Engineering, Tezpur University , Tezpur, 784028 Assam, India
- Center for Multidisciplinary Research, Tezpur University , Tezpur, 784028 Assam, India
| | - Suvendra Kumar Ray
- Department of Molecular Biology and Biotechnology, Tezpur University , Tezpur, 784028 Assam, India
- Center for Multidisciplinary Research, Tezpur University , Tezpur, 784028 Assam, India
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4
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Coluzzi C, Garcillán-Barcia MP, de la Cruz F, Rocha EPC. Evolution of plasmid mobility: origin and fate of conjugative and non-conjugative plasmids. Mol Biol Evol 2022; 39:6593704. [PMID: 35639760 PMCID: PMC9185392 DOI: 10.1093/molbev/msac115] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Conjugation drives the horizontal transfer of adaptive traits across prokaryotes. One-fourth of the plasmids encode the functions necessary to conjugate autonomously, the others being eventually mobilizable by conjugation. To understand the evolution of plasmid mobility, we studied plasmid size, gene repertoires, and conjugation-related genes. Plasmid gene repertoires were found to vary rapidly in relation to the evolutionary rate of relaxases, for example, most pairs of plasmids with 95% identical relaxases have fewer than 50% of homologs. Among 249 recent transitions of mobility type, we observed a clear excess of plasmids losing the capacity to conjugate. These transitions are associated with even greater changes in gene repertoires, possibly mediated by transposable elements, including pseudogenization of the conjugation locus, exchange of replicases reducing the problem of incompatibility, and extensive loss of other genes. At the microevolutionary scale of plasmid taxonomy, transitions of mobility type sometimes result in the creation of novel taxonomic units. Interestingly, most transitions from conjugative to mobilizable plasmids seem to be lost in the long term. This suggests a source-sink dynamic, where conjugative plasmids generate nonconjugative plasmids that tend to be poorly adapted and are frequently lost. Still, in some cases, these relaxases seem to have evolved to become efficient at plasmid mobilization in trans, possibly by hijacking multiple conjugative systems. This resulted in specialized relaxases of mobilizable plasmids. In conclusion, the evolution of plasmid mobility is frequent, shapes the patterns of gene flow in bacteria, the dynamics of gene repertoires, and the ecology of plasmids.
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Affiliation(s)
- Charles Coluzzi
- Institut Pasteur, Université de Paris Cité, CNRS, UMR3525, Microbial Evolutionary Genomics, Paris, 75015, France
| | - M Pilar Garcillán-Barcia
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-CSIC, C/Albert Einstein 22, 39011, Santander, Spain
| | - Fernando de la Cruz
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-CSIC, C/Albert Einstein 22, 39011, Santander, Spain
| | - Eduardo P C Rocha
- Institut Pasteur, Université de Paris Cité, CNRS, UMR3525, Microbial Evolutionary Genomics, Paris, 75015, France
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5
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GRINS: Genetic elements that recode assembly-line polyketide synthases and accelerate their diversification. Proc Natl Acad Sci U S A 2021; 118:2100751118. [PMID: 34162709 PMCID: PMC8256042 DOI: 10.1073/pnas.2100751118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Assembly-line polyketide synthases (PKSs) are large and complex enzymatic machineries with a multimodular architecture, typically encoded in bacterial genomes by biosynthetic gene clusters. Their modularity has led to an astounding diversity of biosynthesized molecules, many with medical relevance. Thus, understanding the mechanisms that drive PKS evolution is fundamental for both functional prediction of natural PKSs as well as for the engineering of novel PKSs. Here, we describe a repetitive genetic element in assembly-line PKS genes which appears to play a role in accelerating the diversification of closely related biosynthetic clusters. We named this element GRINS: genetic repeats of intense nucleotide skews. GRINS appear to recode PKS protein regions with a biased nucleotide composition and to promote gene conversion. GRINS are present in a large number of assembly-line PKS gene clusters and are particularly widespread in the actinobacterial genus Streptomyces While the molecular mechanisms associated with GRINS appearance, dissemination, and maintenance are unknown, the presence of GRINS in a broad range of bacterial phyla and gene families indicates that these genetic elements could play a fundamental role in protein evolution.
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6
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Georgakopoulos-Soares I, Mouratidis I, Parada GE, Matharu N, Hemberg M, Ahituv N. Asymmetron: a toolkit for the identification of strand asymmetry patterns in biological sequences. Nucleic Acids Res 2021; 49:e4. [PMID: 33211865 PMCID: PMC7797064 DOI: 10.1093/nar/gkaa1052] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 10/15/2020] [Accepted: 10/20/2020] [Indexed: 11/23/2022] Open
Abstract
DNA strand asymmetries can have a major effect on several biological functions, including replication, transcription and transcription factor binding. As such, DNA strand asymmetries and mutational strand bias can provide information about biological function. However, a versatile tool to explore this does not exist. Here, we present Asymmetron, a user-friendly computational tool that performs statistical analysis and visualizations for the evaluation of strand asymmetries. Asymmetron takes as input DNA features provided with strand annotation and outputs strand asymmetries for consecutive occurrences of a single DNA feature or between pairs of features. We illustrate the use of Asymmetron by identifying transcriptional and replicative strand asymmetries of germline structural variant breakpoints. We also show that the orientation of the binding sites of 45% of human transcription factors analyzed have a significant DNA strand bias in transcribed regions, that is also corroborated in ChIP-seq analyses, and is likely associated with transcription. In summary, we provide a novel tool to assess DNA strand asymmetries and show how it can be used to derive new insights across a variety of biological disciplines.
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Affiliation(s)
- Ilias Georgakopoulos-Soares
- Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
- Institute for Human Genetics, University of California San Francisco, San Francisco, CA, USA
| | - Ioannis Mouratidis
- Aristotle University of Thessaloniki, Department of Mathematics, Thessaloniki, GR, Greece
| | - Guillermo E Parada
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, CB10 1SA, UK
- Wellcome Trust Cancer Research UK Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Navneet Matharu
- Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
- Institute for Human Genetics, University of California San Francisco, San Francisco, CA, USA
- Innovative Genomics Institute, University of California San Francisco, San Francisco, CA, USA
| | - Martin Hemberg
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, CB10 1SA, UK
- Wellcome Trust Cancer Research UK Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Nadav Ahituv
- Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
- Institute for Human Genetics, University of California San Francisco, San Francisco, CA, USA
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7
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Tang Y, Zheng X, Liu H, Sunxie F. Population genetics and comparative mitogenomic analyses reveal cryptic diversity of Amphioctopus neglectus (Cephalopoda: Octopodidae). Genomics 2020; 112:3893-3902. [PMID: 32603760 DOI: 10.1016/j.ygeno.2020.06.036] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 06/14/2020] [Accepted: 06/22/2020] [Indexed: 12/28/2022]
Abstract
This study presented 96 cox1 and 76 cox3 genes of Amphioctopus neglectus populations. Three distinct lineages were formed from phylogenetic trees and networks constructed using haplotypes. Mitogenomes of A. neglectus-a and A. neglectus-b as the representatives of two lineages separated from population genetics were sequenced to compare with A. neglectus at the genome-level. Amphioctopus neglectus-a showed significant differences with A. neglectus, mainly reflected in gene length, intergenic regions and the secondary structure of tandem repeat motifs. Notably, two sequence deletions in mitogenomes of the two representative species were detected in different positions of major non-coding regions, which were the most distinct differences with A. neglectus. Pairwise genetic distances and the phylogenetic analysis supported the relationship of (A. neglectus-a + (A. neglectus + A. neglectus-b)). This study suggested that A. neglectus-a should be considered as a potential cryptic species of this complex, while A. neglectus-b needed further verification to be defined.
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Affiliation(s)
- Yan Tang
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao 266003, China; Key Laboratory of Mariculture, Ocean University of China, Qingdao 266003, China
| | - Xiaodong Zheng
- Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao 266003, China; Key Laboratory of Mariculture, Ocean University of China, Qingdao 266003, China.
| | - Haijuan Liu
- Guangxi Key Laboratory of Marine Biotechnology, Guangxi Institute of Oceanology, Beihai 536000, China
| | - Feige Sunxie
- Dongshan Boguangtianxing Foods Co., Ltd., Zhangzhou 363000, China
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8
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Ohbayashi R, Hirooka S, Onuma R, Kanesaki Y, Hirose Y, Kobayashi Y, Fujiwara T, Furusawa C, Miyagishima SY. Evolutionary Changes in DnaA-Dependent Chromosomal Replication in Cyanobacteria. Front Microbiol 2020; 11:786. [PMID: 32411117 PMCID: PMC7198777 DOI: 10.3389/fmicb.2020.00786] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 04/02/2020] [Indexed: 12/02/2022] Open
Abstract
Replication of the circular bacterial chromosome is initiated at a unique origin (oriC) in a DnaA-dependent manner in which replication proceeds bidirectionally from oriC to ter. The nucleotide compositions of most bacteria differ between the leading and lagging DNA strands. Thus, the chromosomal DNA sequence typically exhibits an asymmetric GC skew profile. Further, free-living bacteria without genomes encoding dnaA were unknown. Thus, a DnaA-oriC-dependent replication initiation mechanism may be essential for most bacteria. However, most cyanobacterial genomes exhibit irregular GC skew profiles. We previously found that the Synechococcus elongatus chromosome, which exhibits a regular GC skew profile, is replicated in a DnaA-oriC-dependent manner, whereas chromosomes of Synechocystis sp. PCC 6803 and Nostoc sp. PCC 7120, which exhibit an irregular GC skew profile, are replicated from multiple origins in a DnaA-independent manner. Here we investigate the variation in the mechanisms of cyanobacterial chromosome replication. We found that the genomes of certain free-living species do not encode dnaA and such species, including Cyanobacterium aponinum PCC 10605 and Geminocystis sp. NIES-3708, replicate their chromosomes from multiple origins. Synechococcus sp. PCC 7002, which is phylogenetically closely related to dnaA-lacking free-living species as well as to dnaA-encoding but DnaA-oriC-independent Synechocystis sp. PCC 6803, possesses dnaA. In Synechococcus sp. PCC 7002, dnaA was not essential and its chromosomes were replicated from a unique origin in a DnaA-oriC independent manner. Our results also suggest that loss of DnaA-oriC-dependency independently occurred multiple times during cyanobacterial evolution and raises a possibility that the loss of dnaA or loss of DnaA-oriC dependency correlated with an increase in ploidy level.
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Affiliation(s)
- Ryudo Ohbayashi
- Department of Gene Function and Phenomics, National Institute of Genetics, Shizuoka, Japan
| | - Shunsuke Hirooka
- Department of Gene Function and Phenomics, National Institute of Genetics, Shizuoka, Japan
| | - Ryo Onuma
- Department of Gene Function and Phenomics, National Institute of Genetics, Shizuoka, Japan
| | - Yu Kanesaki
- Research Institute of Green Science and Technology, Shizuoka University, Shizuoka, Japan
| | - Yuu Hirose
- Department of Applied Chemistry and Life Science, Toyohashi University of Technology, Toyohashi, Japan
| | - Yusuke Kobayashi
- Department of Gene Function and Phenomics, National Institute of Genetics, Shizuoka, Japan
| | - Takayuki Fujiwara
- Department of Gene Function and Phenomics, National Institute of Genetics, Shizuoka, Japan.,Department of Genetics, The Graduate University for Advanced Studies (SOKENDAI), Shizuoka, Japan
| | - Chikara Furusawa
- Center for Biosystems Dynamics Research, RIKEN, Osaka, Japan.,Universal Biology Institute, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Shin-Ya Miyagishima
- Department of Gene Function and Phenomics, National Institute of Genetics, Shizuoka, Japan.,Department of Genetics, The Graduate University for Advanced Studies (SOKENDAI), Shizuoka, Japan
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9
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Syeda AH, Dimude JU, Skovgaard O, Rudolph CJ. Too Much of a Good Thing: How Ectopic DNA Replication Affects Bacterial Replication Dynamics. Front Microbiol 2020; 11:534. [PMID: 32351461 PMCID: PMC7174701 DOI: 10.3389/fmicb.2020.00534] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Accepted: 03/12/2020] [Indexed: 12/15/2022] Open
Abstract
Each cell division requires the complete and accurate duplication of the entire genome. In bacteria, the duplication process of the often-circular chromosomes is initiated at a single origin per chromosome, resulting in two replication forks that traverse the chromosome in opposite directions. DNA synthesis is completed once the two forks fuse in a region diametrically opposite the origin. In some bacteria, such as Escherichia coli, the region where forks fuse forms a specialized termination area. Polar replication fork pause sites flanking this area can pause the progression of replication forks, thereby allowing forks to enter but not to leave. Transcription of all required genes has to take place simultaneously with genome duplication. As both of these genome trafficking processes share the same template, conflicts are unavoidable. In this review, we focus on recent attempts to add additional origins into various ectopic chromosomal locations of the E. coli chromosome. As ectopic origins disturb the native replichore arrangements, the problems resulting from such perturbations can give important insights into how genome trafficking processes are coordinated and the problems that arise if this coordination is disturbed. The data from these studies highlight that head-on replication–transcription conflicts are indeed highly problematic and multiple repair pathways are required to restart replication forks arrested at obstacles. In addition, the existing data also demonstrate that the replication fork trap in E. coli imposes significant constraints to genome duplication if ectopic origins are active. We describe the current models of how replication fork fusion events can cause serious problems for genome duplication, as well as models of how such problems might be alleviated both by a number of repair pathways as well as the replication fork trap system. Considering the problems associated both with head-on replication-transcription conflicts as well as head-on replication fork fusion events might provide clues of how these genome trafficking issues have contributed to shape the distinct architecture of bacterial chromosomes.
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Affiliation(s)
- Aisha H Syeda
- Department of Biology, University of York, York, United Kingdom
| | - Juachi U Dimude
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge, United Kingdom
| | - Ole Skovgaard
- Department of Science and Environment, Roskilde University, Roskilde, Denmark
| | - Christian J Rudolph
- Division of Biosciences, College of Health and Life Sciences, Brunel University London, Uxbridge, United Kingdom
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10
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Kono N, Tomita M, Arakawa K. Accelerated Laboratory Evolution Reveals the Influence of Replication on the GC Skew in Escherichia coli. Genome Biol Evol 2018; 10:3110-3117. [PMID: 30371772 PMCID: PMC6263442 DOI: 10.1093/gbe/evy237] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/19/2018] [Indexed: 12/13/2022] Open
Abstract
Most bacterial genomes display contrasting strand asymmetry in a variety of features, such as nucleotide composition and gene orientation, of the two replichores separated by the replication origin and terminus. The cause for the polarization is often attributed to mutations arising from the asymmetric replication machinery. Notably, a base compositional bias known as a GC skew is focused on as a footprint of the bacterial genome evolution driven by DNA replication. Previously, although a replication driven mutation pattern responsible for the GC skew formation or the related mathematical models have been well reported, an exact impact of the replication-related elements on the genomic structure is yet actively debated, and not confirmed experimentally. However, the GC skew formation is very time consuming and challenging in the laboratory. We, therefore, used cytosine deaminase as a DNA mutator, and by monitoring the mutations during an accelerated laboratory evolution procedure with Illumina sequencing, we enabled the trial and error of the GC skew formation in high resolution. Using this technology, we succeeded in reconfirming the influence of bacterial replication machinery on the genomic structure at high resolution.
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Affiliation(s)
- Nobuaki Kono
- Institute for Advanced Biosciences, Keio University
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11
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Camiolo S, Toome-Heller M, Aime MC, Haridas S, Grigoriev IV, Porceddu A, Mannazzu I. An analysis of codon bias in six red yeast species. Yeast 2018; 36:53-64. [PMID: 30264407 DOI: 10.1002/yea.3359] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 09/10/2018] [Accepted: 09/23/2018] [Indexed: 11/11/2022] Open
Abstract
Red yeasts, primarily species of Rhodotorula, Sporobolomyces, and other genera of Pucciniomycotina, are traditionally considered proficient systems for lipid and terpene production, and only recently have also gained consideration for the production of a wider range of molecules of biotechnological potential. Improvements of transgene delivery protocols and regulated gene expression systems have been proposed, but a dearth of information on compositional and/or structural features of genes has prevented transgene sequence optimization efforts for high expression levels. Here, the codon compositional features of genes in six red yeast species were characterized, and the impact that evolutionary forces may have played in shaping this compositional bias was dissected by using several computational approaches. Results obtained are compatible with the hypothesis that mutational bias, although playing a significant role, cannot alone explain synonymous codon usage bias of genes. Nevertheless, several lines of evidences indicated a role for translational selection in driving the synonymous codons that allow high expression efficiency. These optimal synonymous codons are identified for each of the six species analyzed. Moreover, the presence of intragenic patterns of codon usage, which are thought to facilitate polyribosome formation, was highlighted. The information presented should be taken into consideration for transgene design for optimal expression in red yeast species.
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Affiliation(s)
- Salvatore Camiolo
- Dipartimento di Agraria, Università degli Studi di Sassari, Sassari, Italy
| | - Merje Toome-Heller
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, USA
| | - M Catherine Aime
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana, USA
| | - Sajeet Haridas
- US Department of Energy Joint Genome Institute, Walnut Creek, California, USA
| | - Igor V Grigoriev
- US Department of Energy Joint Genome Institute, Walnut Creek, California, USA
| | - Andrea Porceddu
- Dipartimento di Agraria, Università degli Studi di Sassari, Sassari, Italy
| | - Ilaria Mannazzu
- Dipartimento di Agraria, Università degli Studi di Sassari, Sassari, Italy
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12
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Guo Z, Jiang Z, Han L, Ding Y, Hou X. Characterisation of the complete mitochondrial genome of the black-footed abalone Haliotis iris. NEW ZEALAND JOURNAL OF ZOOLOGY 2018. [DOI: 10.1080/03014223.2018.1495655] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Zhansheng Guo
- Marine College, Shandong University at Weihai, Weihai, People’s Republic of China
| | - Zhaoyang Jiang
- Marine College, Shandong University at Weihai, Weihai, People’s Republic of China
| | - Leng Han
- Marine College, Shandong University at Weihai, Weihai, People’s Republic of China
| | - Yi Ding
- Marine College, Shandong University at Weihai, Weihai, People’s Republic of China
| | - Xuguang Hou
- Marine College, Shandong University at Weihai, Weihai, People’s Republic of China
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13
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Sun S, Li Q, Kong L, Yu H. Multiple reversals of strand asymmetry in molluscs mitochondrial genomes, and consequences for phylogenetic inferences. Mol Phylogenet Evol 2017; 118:222-231. [PMID: 29038046 DOI: 10.1016/j.ympev.2017.10.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2017] [Revised: 10/08/2017] [Accepted: 10/12/2017] [Indexed: 01/05/2023]
Abstract
Strand asymmetry in nucleotide composition is a remarkable feature of animal mitochondrial genomes. The strand-specific bias in the nucleotide composition of the mtDNA has been known to be highly problematic for phylogenetic analyses. Here, the strand asymmetry was compared across 140 mollusc species and analyzed for a mtDNA fragment including twelve protein-coding genes. The analyses show that almost all species in Gastropoda (except Heterobranchia) and all species in Bivalvia present reversals of strand bias. The skew values on individual genes for all codon positions (P123), third codon positions (P3), and fourfold redundant third codon positions (P4FD) indicated that CG skews are the best indicators of strand asymmetry. The differences in the patterns of strand asymmetry significantly influenced the amino acid composition of the encoded proteins. These biases are most striking for the amino acids Valine, Cysteine, Asparagine and Threonines, which appear to have evolved asymmetrical exchanges in response to shifts in nucleotide composition. Molluscs with strong variability of genome architectures (ARs) are usually characterized by a reversal of the usual strand bias. Phylogenetic analyses show that reversals of asymmetric mutational constraints have consequences on the phylogenetic inferences, as taxa characterized by reverse strand bias (Heterobranchia and Bivalvia) tend to group together due to long-branch attraction (LBA) artifacts. Neutral Transitions Excluded (NTE) model did not overcome the problem of heterogeneous biases present in molluscs mt genomes, suggested it may not be appropriate for molluscs mt genome data. Further refinement phylogenetic models may help us better understand internal relationships among these diverse organisms.
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Affiliation(s)
- Shao'e Sun
- Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, China
| | - Qi Li
- Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, China; Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, China.
| | - Lingfeng Kong
- Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, China
| | - Hong Yu
- Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, China
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14
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Mutator genomes decay, despite sustained fitness gains, in a long-term experiment with bacteria. Proc Natl Acad Sci U S A 2017; 114:E9026-E9035. [PMID: 29073099 DOI: 10.1073/pnas.1705887114] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Understanding the extreme variation among bacterial genomes remains an unsolved challenge in evolutionary biology, despite long-standing debate about the relative importance of natural selection, mutation, and random drift. A potentially important confounding factor is the variation in mutation rates between lineages and over evolutionary history, which has been documented in several species. Mutation accumulation experiments have shown that hypermutability can erode genomes over short timescales. These results, however, were obtained under conditions of extremely weak selection, casting doubt on their general relevance. Here, we circumvent this limitation by analyzing genomes from mutator populations that arose during a long-term experiment with Escherichia coli, in which populations have been adaptively evolving for >50,000 generations. We develop an analytical framework to quantify the relative contributions of mutation and selection in shaping genomic characteristics, and we validate it using genomes evolved under regimes of high mutation rates with weak selection (mutation accumulation experiments) and low mutation rates with strong selection (natural isolates). Our results show that, despite sustained adaptive evolution in the long-term experiment, the signature of selection is much weaker than that of mutational biases in mutator genomes. This finding suggests that relatively brief periods of hypermutability can play an outsized role in shaping extant bacterial genomes. Overall, these results highlight the importance of genomic draft, in which strong linkage limits the ability of selection to purge deleterious mutations. These insights are also relevant to other biological systems evolving under strong linkage and high mutation rates, including viruses and cancer cells.
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15
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Saffarian A, Touchon M, Mulet C, Tournebize R, Passet V, Brisse S, Rocha EPC, Sansonetti PJ, Pédron T. Comparative genomic analysis of Acinetobacter strains isolated from murine colonic crypts. BMC Genomics 2017; 18:525. [PMID: 28697749 PMCID: PMC5505149 DOI: 10.1186/s12864-017-3925-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 07/06/2017] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND A restricted set of aerobic bacteria dominated by the Acinetobacter genus was identified in murine intestinal colonic crypts. The vicinity of such bacteria with intestinal stem cells could indicate that they protect the crypt against cytotoxic and genotoxic signals. Genome analyses of these bacteria were performed to better appreciate their biodegradative capacities. RESULTS Two taxonomically different clusters of Acinetobacter were isolated from murine proximal colonic crypts, one was identified as A. modestus and the other as A. radioresistens. Their identification was performed through biochemical parameters and housekeeping gene sequencing. After selection of one strain of each cluster (A. modestus CM11G and A. radioresistens CM38.2), comparative genomic analysis was performed on whole-genome sequencing data. The antibiotic resistance pattern of these two strains is different, in line with the many genes involved in resistance to heavy metals identified in both genomes. Moreover whereas the operon benABCDE involved in benzoate metabolism is encoded by the two genomes, the operon antABC encoding the anthranilate dioxygenase, and the phenol hydroxylase gene cluster are absent in the A. modestus genomic sequence, indicating that the two strains have different capacities to metabolize xenobiotics. A common feature of the two strains is the presence of a type IV pili system, and the presence of genes encoding proteins pertaining to secretion systems such as Type I and Type II secretion systems. CONCLUSIONS Our comparative genomic analysis revealed that different Acinetobacter isolated from the same biological niche, even if they share a large majority of genes, possess unique features that could play a specific role in the protection of the intestinal crypt.
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Affiliation(s)
- Azadeh Saffarian
- Unité de Pathogénie Microbienne Moléculaire, INSERM U1202, Institut Pasteur, Paris, France
| | - Marie Touchon
- Unité de Génomique Evolutive des Microbes, CNRS, UMR3525, Institut Pasteur, Paris, France
| | - Céline Mulet
- Unité de Pathogénie Microbienne Moléculaire, INSERM U1202, Institut Pasteur, Paris, France
| | - Régis Tournebize
- Unité de Pathogénie Microbienne Moléculaire, INSERM U1202, Imagopole Citech, Institut Pasteur, Paris, France
| | - Virginie Passet
- Unité de Génomique Evolutive des Microbes, CNRS, UMR3525, Institut Pasteur, Paris, France
| | - Sylvain Brisse
- Unité de Génomique Evolutive des Microbes, CNRS, UMR3525, Institut Pasteur, Paris, France
| | - Eduardo P C Rocha
- Unité de Génomique Evolutive des Microbes, CNRS, UMR3525, Institut Pasteur, Paris, France
| | - Philippe J Sansonetti
- Unité de Pathogénie Microbienne Moléculaire, INSERM U1202, Institut Pasteur, Paris, France.,Chaire de Microbiologie et Maladies Infectieuses, Collège de France, Paris, France
| | - Thierry Pédron
- Unité de Pathogénie Microbienne Moléculaire, INSERM U1202, Institut Pasteur, Paris, France.
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16
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Błażej P, Mackiewicz D, Grabińska M, Wnętrzak M, Mackiewicz P. Optimization of amino acid replacement costs by mutational pressure in bacterial genomes. Sci Rep 2017; 7:1061. [PMID: 28432324 PMCID: PMC5430830 DOI: 10.1038/s41598-017-01130-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 03/27/2017] [Indexed: 12/17/2022] Open
Abstract
Mutations are considered a spontaneous and random process, which is important component of evolution because it generates genetic variation. On the other hand, mutations are deleterious leading to non-functional genes and energetically costly repairs. Therefore, one can expect that the mutational pressure is optimized to simultaneously generate genetic diversity and preserve genetic information. To check if empirical mutational pressures are optimized in these ways, we compared matrices of nucleotide mutation rates derived from bacterial genomes with their best possible alternatives that minimized or maximized costs of amino acid replacements associated with differences in their physicochemical properties (e.g. hydropathy and polarity). It should be noted that the studied empirical nucleotide substitution matrices and the costs of amino acid replacements are independent because these matrices were derived from sites free of selection on amino acid properties and the amino acid costs assumed only amino acid physicochemical properties without any information about mutation at the nucleotide level. Obtained results indicate that the empirical mutational matrices show a tendency to minimize costs of amino acid replacements. It implies that bacterial mutational pressures can evolve to decrease consequences of amino acid substitutions. However, the optimization is not full, which enables generation of some genetic variability.
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Affiliation(s)
- Paweł Błażej
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, ul. Joliot-Curie 14a, 50-383, Wrocław, Poland
| | - Dorota Mackiewicz
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, ul. Joliot-Curie 14a, 50-383, Wrocław, Poland
| | - Małgorzata Grabińska
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, ul. Joliot-Curie 14a, 50-383, Wrocław, Poland
| | - Małgorzata Wnętrzak
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, ul. Joliot-Curie 14a, 50-383, Wrocław, Poland
| | - Paweł Mackiewicz
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, ul. Joliot-Curie 14a, 50-383, Wrocław, Poland.
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17
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Shewaramani S, Finn TJ, Leahy SC, Kassen R, Rainey PB, Moon CD. Anaerobically Grown Escherichia coli Has an Enhanced Mutation Rate and Distinct Mutational Spectra. PLoS Genet 2017; 13:e1006570. [PMID: 28103245 PMCID: PMC5289635 DOI: 10.1371/journal.pgen.1006570] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 02/02/2017] [Accepted: 01/04/2017] [Indexed: 12/21/2022] Open
Abstract
Oxidative stress is a major cause of mutation but little is known about how growth in the absence of oxygen impacts the rate and spectrum of mutations. We employed long-term mutation accumulation experiments to directly measure the rates and spectra of spontaneous mutation events in Escherichia coli populations propagated under aerobic and anaerobic conditions. To detect mutations, whole genome sequencing was coupled with methods of analysis sufficient to identify a broad range of mutational classes, including structural variants (SVs) generated by movement of repetitive elements. The anaerobically grown populations displayed a mutation rate nearly twice that of the aerobic populations, showed distinct asymmetric mutational strand biases, and greater insertion element activity. Consistent with mutation rate and spectra observations, genes for transposition and recombination repair associated with SVs were up-regulated during anaerobic growth. Together, these results define differences in mutational spectra affecting the evolution of facultative anaerobes.
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Affiliation(s)
- Sonal Shewaramani
- AgResearch Ltd, Grasslands Research Centre, Palmerston North, New Zealand
- New Zealand Institute for Advanced Study, Massey University, Auckland, New Zealand
| | - Thomas J. Finn
- AgResearch Ltd, Grasslands Research Centre, Palmerston North, New Zealand
- New Zealand Institute for Advanced Study, Massey University, Auckland, New Zealand
| | - Sinead C. Leahy
- AgResearch Ltd, Grasslands Research Centre, Palmerston North, New Zealand
| | - Rees Kassen
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Paul B. Rainey
- New Zealand Institute for Advanced Study, Massey University, Auckland, New Zealand
- Department of Microbial Population Biology, Max Planck Institute for Evolutionary Biology, Plön, Germany
- Ecole Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI ParisTech), CNRS UMR 8231, PSL Research University, Paris, France
| | - Christina D. Moon
- AgResearch Ltd, Grasslands Research Centre, Palmerston North, New Zealand
- * E-mail:
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18
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Duchêne S, Holt KE, Weill FX, Le Hello S, Hawkey J, Edwards DJ, Fourment M, Holmes EC. Genome-scale rates of evolutionary change in bacteria. Microb Genom 2016; 2:e000094. [PMID: 28348834 PMCID: PMC5320706 DOI: 10.1099/mgen.0.000094] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 10/24/2016] [Indexed: 01/26/2023] Open
Abstract
Estimating the rates at which bacterial genomes evolve is critical to understanding major evolutionary and ecological processes such as disease emergence, long-term host–pathogen associations and short-term transmission patterns. The surge in bacterial genomic data sets provides a new opportunity to estimate these rates and reveal the factors that shape bacterial evolutionary dynamics. For many organisms estimates of evolutionary rate display an inverse association with the time-scale over which the data are sampled. However, this relationship remains unexplored in bacteria due to the difficulty in estimating genome-wide evolutionary rates, which are impacted by the extent of temporal structure in the data and the prevalence of recombination. We collected 36 whole genome sequence data sets from 16 species of bacterial pathogens to systematically estimate and compare their evolutionary rates and assess the extent of temporal structure in the absence of recombination. The majority (28/36) of data sets possessed sufficient clock-like structure to robustly estimate evolutionary rates. However, in some species reliable estimates were not possible even with ‘ancient DNA’ data sampled over many centuries, suggesting that they evolve very slowly or that they display extensive rate variation among lineages. The robustly estimated evolutionary rates spanned several orders of magnitude, from approximately 10−5 to 10−8 nucleotide substitutions per site year−1. This variation was negatively associated with sampling time, with this relationship best described by an exponential decay curve. To avoid potential estimation biases, such time-dependency should be considered when inferring evolutionary time-scales in bacteria.
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Affiliation(s)
- Sebastian Duchêne
- 1Marie Bashir Institute of Infectious Diseases and Biosecurity, Charles Perkins Centre, School of Life and Environmental Sciences and Sydney Medical School, The University of Sydney, Sydney, NSW 2006, Australia.,2Centre for Systems Genomics, The University of Melbourne, Melbourne, VIC 3010, Australia.,3Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - Kathryn E Holt
- 2Centre for Systems Genomics, The University of Melbourne, Melbourne, VIC 3010, Australia.,3Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, VIC 3010, Australia
| | | | - Simon Le Hello
- 4Institut Pasteur, Unité des Bactéries Pathogènes Entériques, Paris 75015, France
| | - Jane Hawkey
- 2Centre for Systems Genomics, The University of Melbourne, Melbourne, VIC 3010, Australia.,3Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - David J Edwards
- 2Centre for Systems Genomics, The University of Melbourne, Melbourne, VIC 3010, Australia.,3Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - Mathieu Fourment
- 1Marie Bashir Institute of Infectious Diseases and Biosecurity, Charles Perkins Centre, School of Life and Environmental Sciences and Sydney Medical School, The University of Sydney, Sydney, NSW 2006, Australia
| | - Edward C Holmes
- 1Marie Bashir Institute of Infectious Diseases and Biosecurity, Charles Perkins Centre, School of Life and Environmental Sciences and Sydney Medical School, The University of Sydney, Sydney, NSW 2006, Australia
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19
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Pouyet F, Bailly-Bechet M, Mouchiroud D, Guéguen L. SENCA: A Multilayered Codon Model to Study the Origins and Dynamics of Codon Usage. Genome Biol Evol 2016; 8:2427-41. [PMID: 27401173 PMCID: PMC5010899 DOI: 10.1093/gbe/evw165] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Gene sequences are the target of evolution operating at different levels, including the nucleotide, codon, and amino acid levels. Disentangling the impact of those different levels on gene sequences requires developing a probabilistic model with three layers. Here we present SENCA (site evolution of nucleotides, codons, and amino acids), a codon substitution model that separately describes 1) nucleotide processes which apply on all sites of a sequence such as the mutational bias, 2) preferences between synonymous codons, and 3) preferences among amino acids. We argue that most synonymous substitutions are not neutral and that SENCA provides more accurate estimates of selection compared with more classical codon sequence models. We study the forces that drive the genomic content evolution, intraspecifically in the core genome of 21 prokaryotes and interspecifically for five Enterobacteria. We retrieve the existence of a universal mutational bias toward AT, and that taking into account selection on synonymous codon usage has consequences on the measurement of selection on nonsynonymous substitutions. We also confirm that codon usage bias is mostly driven by selection on preferred codons. We propose new summary statistics to measure the relative importance of the different evolutionary processes acting on sequences.
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Affiliation(s)
- Fanny Pouyet
- Laboratoire de Biologie et Biométrie Evolutive, University Claude Bernard Lyon 1-University of Lyon, Villeurbanne, France
| | - Marc Bailly-Bechet
- Laboratoire de Biologie et Biométrie Evolutive, University Claude Bernard Lyon 1-University of Lyon, Villeurbanne, France
| | - Dominique Mouchiroud
- Laboratoire de Biologie et Biométrie Evolutive, University Claude Bernard Lyon 1-University of Lyon, Villeurbanne, France
| | - Laurent Guéguen
- Laboratoire de Biologie et Biométrie Evolutive, University Claude Bernard Lyon 1-University of Lyon, Villeurbanne, France
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20
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Apostolou-Karampelis K, Nikolaou C, Almirantis Y. A novel skew analysis reveals substitution asymmetries linked to genetic code GC-biases and PolIII a-subunit isoforms. DNA Res 2016; 23:353-63. [PMID: 27345720 PMCID: PMC4991834 DOI: 10.1093/dnares/dsw021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 05/09/2016] [Indexed: 11/30/2022] Open
Abstract
Strand biases reflect deviations from a null expectation of DNA evolution that assumes strand-symmetric substitution rates. Here, we present strong evidence that nearest-neighbour preferences are a strand-biased feature of bacterial genomes, indicating neighbour-dependent substitution asymmetries. To detect such asymmetries we introduce an alignment free index (relative abundance skews). The profiles of relative abundance skews along coding sequences can trace the phylogenetic relations of bacteria, suggesting that the patterns of neighbour-dependent substitution strand-biases are not common among different lineages, but are rather species-specific. Analysis of neighbour-dependent and codon-site skews sheds light on the origins of substitution asymmetries. Via a simple model we argue that the structure of the genetic code imposes position-dependent substitution strand-biases along coding sequences, as a response to GC mutation pressure. Thus, the organization of the genetic code per se can lead to an uneven distribution of nucleotides among different codon sites, even when requirements for specific codons and amino-acids are not accounted for. Moreover, our results suggest that strand-biases in replication fidelity of PolIII α-subunit induce substitution asymmetries, both neighbour-dependent and independent, on a genome scale. The role of DNA repair systems, such as transcription-coupled repair, is also considered.
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Affiliation(s)
| | - Christoforos Nikolaou
- Computational Genomics Group, Department of Biology, University of Crete, 71409 Heraklion, Greece
| | - Yannis Almirantis
- Institute of Biosciences and Applications, National Center for Scientific Research "Demokritos", 15310 Athens, Greece
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21
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Chen WH, Lu G, Bork P, Hu S, Lercher MJ. Energy efficiency trade-offs drive nucleotide usage in transcribed regions. Nat Commun 2016; 7:11334. [PMID: 27098217 PMCID: PMC4844684 DOI: 10.1038/ncomms11334] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 03/16/2016] [Indexed: 01/29/2023] Open
Abstract
Efficient nutrient usage is a trait under universal selection. A substantial part of cellular resources is spent on making nucleotides. We thus expect preferential use of cheaper nucleotides especially in transcribed sequences, which are often amplified thousand-fold compared with genomic sequences. To test this hypothesis, we derive a mutation-selection-drift equilibrium model for nucleotide skews (strand-specific usage of 'A' versus 'T' and 'G' versus 'C'), which explains nucleotide skews across 1,550 prokaryotic genomes as a consequence of selection on efficient resource usage. Transcription-related selection generally favours the cheaper nucleotides 'U' and 'C' at synonymous sites. However, the information encoded in mRNA is further amplified through translation. Due to unexpected trade-offs in the codon table, cheaper nucleotides encode on average energetically more expensive amino acids. These trade-offs apply to both strand-specific nucleotide usage and GC content, causing a universal bias towards the more expensive nucleotides 'A' and 'G' at non-synonymous coding sites.
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Affiliation(s)
- Wei-Hua Chen
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101, China
- Structural and Computational Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany
| | - Guanting Lu
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101, China
| | - Peer Bork
- Structural and Computational Unit, European Molecular Biology Laboratory, Heidelberg 69117, Germany
- Bioinformatics department, Max Delbrück Centre for Molecular Medicine, Berlin 13125, Germany
| | - Songnian Hu
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing 100101, China
| | - Martin J Lercher
- Institute for Computer Science and Cluster of Excellence on Plant Sciences, Heinrich Heine University, Düsseldorf 40225, Germany
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22
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Touchon M, Rocha EPC. Coevolution of the Organization and Structure of Prokaryotic Genomes. Cold Spring Harb Perspect Biol 2016; 8:a018168. [PMID: 26729648 DOI: 10.1101/cshperspect.a018168] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The cytoplasm of prokaryotes contains many molecular machines interacting directly with the chromosome. These vital interactions depend on the chromosome structure, as a molecule, and on the genome organization, as a unit of genetic information. Strong selection for the organization of the genetic elements implicated in these interactions drives replicon ploidy, gene distribution, operon conservation, and the formation of replication-associated traits. The genomes of prokaryotes are also very plastic with high rates of horizontal gene transfer and gene loss. The evolutionary conflicts between plasticity and organization lead to the formation of regions with high genetic diversity whose impact on chromosome structure is poorly understood. Prokaryotic genomes are remarkable documents of natural history because they carry the imprint of all of these selective and mutational forces. Their study allows a better understanding of molecular mechanisms, their impact on microbial evolution, and how they can be tinkered in synthetic biology.
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Affiliation(s)
- Marie Touchon
- Microbial Evolutionary Genomics, Institut Pasteur, 75015 Paris, France CNRS, UMR3525, 75015 Paris, France
| | - Eduardo P C Rocha
- Microbial Evolutionary Genomics, Institut Pasteur, 75015 Paris, France CNRS, UMR3525, 75015 Paris, France
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23
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Błażej P, Miasojedow B, Grabińska M, Mackiewicz P. Optimization of Mutation Pressure in Relation to Properties of Protein-Coding Sequences in Bacterial Genomes. PLoS One 2015; 10:e0130411. [PMID: 26121655 PMCID: PMC4488281 DOI: 10.1371/journal.pone.0130411] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 05/19/2015] [Indexed: 12/22/2022] Open
Abstract
Most mutations are deleterious and require energetically costly repairs. Therefore, it seems that any minimization of mutation rate is beneficial. On the other hand, mutations generate genetic diversity indispensable for evolution and adaptation of organisms to changing environmental conditions. Thus, it is expected that a spontaneous mutational pressure should be an optimal compromise between these two extremes. In order to study the optimization of the pressure, we compared mutational transition probability matrices from bacterial genomes with artificial matrices fulfilling the same general features as the real ones, e.g., the stationary distribution and the speed of convergence to the stationarity. The artificial matrices were optimized on real protein-coding sequences based on Evolutionary Strategies approach to minimize or maximize the probability of non-synonymous substitutions and costs of amino acid replacements depending on their physicochemical properties. The results show that the empirical matrices have a tendency to minimize the effects of mutations rather than maximize their costs on the amino acid level. They were also similar to the optimized artificial matrices in the nucleotide substitution pattern, especially the high transitions/transversions ratio. We observed no substantial differences between the effects of mutational matrices on protein-coding sequences in genomes under study in respect of differently replicated DNA strands, mutational cost types and properties of the referenced artificial matrices. The findings indicate that the empirical mutational matrices are rather adapted to minimize mutational costs in the studied organisms in comparison to other matrices with similar mathematical constraints.
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Affiliation(s)
- Paweł Błażej
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
| | - Błażej Miasojedow
- Section of Mathematical Statistics, The Faculty of Mathematics, Informatics and Mechanics, University of Warsaw, Warszawa, Poland
| | - Małgorzata Grabińska
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
| | - Paweł Mackiewicz
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
- * E-mail:
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24
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Merrikh CN, Brewer BJ, Merrikh H. The B. subtilis Accessory Helicase PcrA Facilitates DNA Replication through Transcription Units. PLoS Genet 2015; 11:e1005289. [PMID: 26070154 PMCID: PMC4466434 DOI: 10.1371/journal.pgen.1005289] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 05/18/2015] [Indexed: 11/18/2022] Open
Abstract
In bacteria the concurrence of DNA replication and transcription leads to potentially deleterious encounters between the two machineries, which can occur in either the head-on (lagging strand genes) or co-directional (leading strand genes) orientations. These conflicts lead to replication fork stalling and can destabilize the genome. Both eukaryotic and prokaryotic cells possess resolution factors that reduce the severity of these encounters. Though Escherichia coli accessory helicases have been implicated in the mitigation of head-on conflicts, direct evidence of these proteins mitigating co-directional conflicts is lacking. Furthermore, the endogenous chromosomal regions where these helicases act, and the mechanism of recruitment, have not been identified. We show that the essential Bacillus subtilis accessory helicase PcrA aids replication progression through protein coding genes of both head-on and co-directional orientations, as well as rRNA and tRNA genes. ChIP-Seq experiments show that co-directional conflicts at highly transcribed rRNA, tRNA, and head-on protein coding genes are major targets of PcrA activity on the chromosome. Partial depletion of PcrA renders cells extremely sensitive to head-on conflicts, linking the essential function of PcrA to conflict resolution. Furthermore, ablating PcrA’s ATPase/helicase activity simultaneously increases its association with conflict regions, while incapacitating its ability to mitigate conflicts, and leads to cell death. In contrast, disruption of PcrA’s C-terminal RNA polymerase interaction domain does not impact its ability to mitigate conflicts between replication and transcription, its association with conflict regions, or cell survival. Altogether, this work establishes PcrA as an essential factor involved in mitigating transcription-replication conflicts and identifies chromosomal regions where it routinely acts. As both conflicts and accessory helicases are found in all domains of life, these results are broadly relevant. In bacteria the concurrence of DNA replication and transcription leads to potentially deleterious encounters between the two machineries. These encounters can destabilize the genome and lead to mutations. Both eukaryotic and prokaryotic cells possess conflict resolution factors that reduce the detrimental effects of these collisions. In this study we show that without the essential Bacillus subtilis accessory DNA helicase, PcrA, the replication machinery slows down at certain regions of the chromosome in a transcription-dependent manner. PcrA is essential to life but incomplete depletion of PcrA only partially inhibits cell survival. We find that, under these conditions, partial survival defects are significantly exacerbated in the presence of a single severe conflict. In summary our work identifies a high degree of conservation for accessory helicase function in conflict resolution, directly establishes PcrA’s role in co-directional conflict resolution, and maps the natural chromosomal regions where such activities are routinely needed. Because both conflicts and accessory helicases are found in all domains of life, the results of this work are broadly relevant.
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Affiliation(s)
- Christopher N. Merrikh
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
| | - Bonita J. Brewer
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
| | - Houra Merrikh
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
- * E-mail:
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25
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Sung W, Ackerman MS, Gout JF, Miller SF, Williams E, Foster PL, Lynch M. Asymmetric Context-Dependent Mutation Patterns Revealed through Mutation-Accumulation Experiments. Mol Biol Evol 2015; 32:1672-83. [PMID: 25750180 DOI: 10.1093/molbev/msv055] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Despite the general assumption that site-specific mutation rates are independent of the local sequence context, a growing body of evidence suggests otherwise. To further examine context-dependent patterns of mutation, we amassed 5,645 spontaneous mutations in wild- type (WT) and mismatch-repair deficient (MMR(-)) mutation-accumulation (MA) lines of the gram-positive model organism Bacillus subtilis. We then analyzed>7,500 spontaneous base-substitution mutations across B. subtilis, Escherichia coli, and Mesoplasma florum WT and MMR(-) MA lines, finding a context-dependent mutation pattern that is asymmetric around the origin of replication. Different neighboring nucleotides can alter site-specific mutation rates by as much as 75-fold, with sites neighboring G:C base pairs or dimers involving alternating pyrimidine-purine and purine-pyrimidine nucleotides having significantly elevated mutation rates. The influence of context-dependent mutation on genome architecture is strongest in M. florum, consistent with the reduced efficiency of selection in organisms with low effective population size. If not properly accounted for, the disparities arising from patterns of context-dependent mutation can significantly influence interpretations of positive and purifying selection.
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Affiliation(s)
- Way Sung
- Department of Biology, Indiana University, Bloomington
| | | | | | | | | | | | - Michael Lynch
- Department of Biology, Indiana University, Bloomington
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26
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Maharjan R, Ferenci T. Mutational signatures indicative of environmental stress in bacteria. Mol Biol Evol 2014; 32:380-91. [PMID: 25389207 DOI: 10.1093/molbev/msu306] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Evolutionary innovations are dependent on mutations. Mutation rates are increased by adverse conditions in the laboratory, but there is no evidence that stressful environments that do not directly impact on DNA leave a mutational imprint on extant genomes. Mutational spectra in the laboratory are normally determined with unstressed cells but are unavailable with stressed bacteria. To by-pass problems with viability, selection effects, and growth rate differences due to stressful environments, in this study we used a set of genetically engineered strains to identify the mutational spectrum associated with nutritional stress. The strain set members each had a fixed level of the master regulator protein, RpoS, which controls the general stress response of Escherichia coli. By assessing mutations in cycA gene from 485 cycloserine resistant mutants collected from as many independent cultures with three distinct perceived stress (RpoS) levels, we were able establish a dose-dependent relationship between stress and mutational spectra. The altered mutational patterns included base pair substitutions, single base pair indels, longer indels, and transpositions of different insertion sequences. The mutational spectrum of low-RpoS cells closely matches the genome-wide spectrum previously generated in laboratory environments, while the spectra of high RpoS, high perceived stress cells more closely matches spectra found in comparisons of extant genomes. Our results offer an explanation of the uneven mutational profiles such as the transition-transversion biases observed in extant genomes and provide a framework for assessing the contribution of stress-induced mutagenesis to evolutionary transitions and the mutational emergence of antibiotic resistance and disease states.
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Affiliation(s)
- Ram Maharjan
- School of Molecular Bioscience, University of Sydney, Sydney, NSW, Australia
| | - Thomas Ferenci
- School of Molecular Bioscience, University of Sydney, Sydney, NSW, Australia
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27
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Gómez MJ, Díaz-Maldonado H, González-Tortuero E, López de Saro FJ. Chromosomal replication dynamics and interaction with the β sliding clamp determine orientation of bacterial transposable elements. Genome Biol Evol 2014; 6:727-40. [PMID: 24614824 PMCID: PMC3971601 DOI: 10.1093/gbe/evu052] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Insertion sequences (ISs) are small transposable elements widespread in bacterial genomes, where they play an essential role in chromosome evolution by stimulating recombination and genetic flow. Despite their ubiquity, it is unclear how ISs interact with the host. Here, we report a survey of the orientation patterns of ISs in bacterial chromosomes with the objective of gaining insight into the interplay between ISs and host chromosomal functions. We find that a significant fraction of IS families present a consistent and family-specific orientation bias with respect to chromosomal DNA replication, especially in Firmicutes. Additionally, we find that the transposases of up to nine different IS families with different transposition pathways interact with the β sliding clamp, an essential replication factor, suggesting that this is a widespread mechanism of interaction with the host. Although we find evidence that the interaction with the β sliding clamp is common to all bacterial phyla, it also could explain the observed strong orientation bias found in Firmicutes, because in this group β is asymmetrically distributed during synthesis of the leading or lagging strands. Besides the interaction with the β sliding clamp, other asymmetries also play a role in the biased orientation of some IS families. The utilization of the highly conserved replication sliding clamps suggests a mechanism for host regulation of IS proliferation and also a universal platform for IS dispersal and transmission within bacterial populations and among phylogenetically distant species.
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Affiliation(s)
- Manuel J Gómez
- Department of Molecular Evolution, Centro de Astrobiología (INTA-CSIC), Madrid, Spain
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28
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Abstract
Mutational heterogeneity must be taken into account when reconstructing evolutionary histories, calibrating molecular clocks, and predicting links between genes and disease. Selective pressures and various DNA transactions have been invoked to explain the heterogeneous distribution of genetic variation between species, within populations, and in tissue-specific tumors. To examine relationships between such heterogeneity and variations in leading- and lagging-strand replication fidelity and mismatch repair, we accumulated 40,000 spontaneous mutations in eight diploid yeast strains in the absence of selective pressure. We found that replicase error rates vary by fork direction, coding state, nucleosome proximity, and sequence context. Further, error rates and DNA mismatch repair efficiency both vary by mismatch type, responsible polymerase, replication time, and replication origin proximity. Mutation patterns implicate replication infidelity as one driver of variation in somatic and germline evolution, suggest mechanisms of mutual modulation of genome stability and composition, and predict future observations in specific cancers.
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29
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Oliveira PH, Touchon M, Rocha EPC. The interplay of restriction-modification systems with mobile genetic elements and their prokaryotic hosts. Nucleic Acids Res 2014; 42:10618-31. [PMID: 25120263 PMCID: PMC4176335 DOI: 10.1093/nar/gku734] [Citation(s) in RCA: 179] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 07/29/2014] [Accepted: 07/30/2014] [Indexed: 01/21/2023] Open
Abstract
The roles of restriction-modification (R-M) systems in providing immunity against horizontal gene transfer (HGT) and in stabilizing mobile genetic elements (MGEs) have been much debated. However, few studies have precisely addressed the distribution of these systems in light of HGT, its mechanisms and its vectors. We analyzed the distribution of R-M systems in 2261 prokaryote genomes and found their frequency to be strongly dependent on the presence of MGEs, CRISPR-Cas systems, integrons and natural transformation. Yet R-M systems are rare in plasmids, in prophages and nearly absent from other phages. Their abundance depends on genome size for small genomes where it relates with HGT but saturates at two occurrences per genome. Chromosomal R-M systems might evolve under cycles of purifying and relaxed selection, where sequence conservation depends on the biochemical activity and complexity of the system and total gene loss is frequent. Surprisingly, analysis of 43 pan-genomes suggests that solitary R-M genes rarely arise from the degradation of R-M systems. Solitary genes are transferred by large MGEs, whereas complete systems are more frequently transferred autonomously or in small MGEs. Our results suggest means of testing the roles for R-M systems and their associations with MGEs.
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Affiliation(s)
- Pedro H Oliveira
- Institut Pasteur, Microbial Evolutionary Genomics, Département Génomes et Génétique, Paris, France CNRS, UMR3525, Paris, France
| | - Marie Touchon
- Institut Pasteur, Microbial Evolutionary Genomics, Département Génomes et Génétique, Paris, France CNRS, UMR3525, Paris, France
| | - Eduardo P C Rocha
- Institut Pasteur, Microbial Evolutionary Genomics, Département Génomes et Génétique, Paris, France CNRS, UMR3525, Paris, France
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30
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Hyrien O, Rappailles A, Guilbaud G, Baker A, Chen CL, Goldar A, Petryk N, Kahli M, Ma E, d'Aubenton-Carafa Y, Audit B, Thermes C, Arneodo A. From simple bacterial and archaeal replicons to replication N/U-domains. J Mol Biol 2013; 425:4673-89. [PMID: 24095859 DOI: 10.1016/j.jmb.2013.09.021] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 09/15/2013] [Accepted: 09/19/2013] [Indexed: 10/26/2022]
Abstract
The Replicon Theory proposed 50 years ago has proven to apply for replicons of the three domains of life. Here, we review our knowledge of genome organization into single and multiple replicons in bacteria, archaea and eukarya. Bacterial and archaeal replicator/initiator systems are quite specific and efficient, whereas eukaryotic replicons show degenerate specificity and efficiency, allowing for complex regulation of origin firing time. We expand on recent evidence that ~50% of the human genome is organized as ~1,500 megabase-sized replication domains with a characteristic parabolic (U-shaped) replication timing profile and linear (N-shaped) gradient of replication fork polarity. These N/U-domains correspond to self-interacting segments of the chromatin fiber bordered by open chromatin zones and replicate by cascades of origin firing initiating at their borders and propagating to their center, possibly by fork-stimulated initiation. The conserved occurrence of this replication pattern in the germline of mammals has resulted over evolutionary times in the formation of megabase-sized domains with an N-shaped nucleotide compositional skew profile due to replication-associated mutational asymmetries. Overall, these results reveal an evolutionarily conserved but developmentally plastic organization of replication that is driving mammalian genome evolution.
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Affiliation(s)
- Olivier Hyrien
- Ecole Normale Supérieure, IBENS UMR8197 U1024, Paris 75005, France.
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31
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Feng Y, Chen HL, Chiu CH. Differential genomic variation between short- and long-term bacterial evolution revealed by ultradeep sequencing. Genome Biol Evol 2013; 5:572-7. [PMID: 23531725 PMCID: PMC3622303 DOI: 10.1093/gbe/evt031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Mutation and selection are both thought to impact significantly the nucleotide composition of bacterial genomes. Earlier studies have compared closely related strains to obtain mutation patterns based on the hypothesis that these bacterial strains had diverged so recently that selection will not have had enough time to play its role. In this study, we used a SOLiD autosequencer that was based on a dual-base encoding scheme to sequence the genome of Staphylococcus aureus with a mapping coverage of over 5,000×. By directly counting the variation obtained from these ultradeep sequencing reads, we found that A → G was the predominant single-base substitution and 1 bp deletions were the major small indel. These patterns are completely different from those obtained by comparison of closely related S. aureus strains, where C → T accounted for a larger proportion of mutations and deletions were shown to occur at an almost equal frequency to insertion. These findings suggest that the genomic differences between closely related bacterial strains have already undergone selection and are therefore not representative of spontaneous mutation.
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Affiliation(s)
- Ye Feng
- Genomics Research Center, Harbin Medical University, People's Republic of China.
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32
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Song TJ, Wang Y, Shen JG, Pan JP, Huang J. Genomic comparisons between paired bacterial strains with strong and weak GC skews. J Basic Microbiol 2013; 54:111-9. [PMID: 23457112 DOI: 10.1002/jobm.201200252] [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: 05/09/2012] [Accepted: 09/19/2012] [Indexed: 11/07/2022]
Abstract
A majority of known eubacterial genomes are characteristic of GC skew, i.e., the leading strand has exceeding number of G over C. The cause of this compositional bias is still not very clear. In this study, we chose five pairs of genomes from distantly related bacterial genera, i.e., Buchnera, Haemophilus, Mycoplasma, Mycobacterium, and Synechococcus, each containing one with strong GC skew and the other with weak GC skew. Through comparison of the orthologous genes in these genera, we found that neither chromosomal rearrangement nor CDS skew has direct relationship with GC skew.
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Affiliation(s)
- Tie-Jun Song
- Department of Clinic Lab, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China
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33
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Brito PH, Rocha EPC, Xavier KB, Gordo I. Natural genome diversity of AI-2 quorum sensing in Escherichia coli: conserved signal production but labile signal reception. Genome Biol Evol 2013; 5:16-30. [PMID: 23246794 PMCID: PMC3595036 DOI: 10.1093/gbe/evs122] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Quorum sensing (QS) regulates the onset of bacterial social responses in function to cell density having an important impact in virulence. Autoinducer-2 (AI-2) is a signal that has the peculiarity of mediating both intra- and interspecies bacterial QS. We analyzed the diversity of all components of AI-2 QS across 44 complete genomes of Escherichia coli and Shigella strains. We used phylogenetic tools to study its evolution and determined the phenotypes of single-deletion mutants to predict phenotypes of natural strains. Our analysis revealed many likely adaptive polymorphisms both in gene content and in nucleotide sequence. We show that all natural strains possess the signal emitter (the luxS gene), but many lack a functional signal receptor (complete lsr operon) and the ability to regulate extracellular signal concentrations. This result is in striking contrast with the canonical species-specific QS systems where one often finds orphan receptors, without a cognate synthase, but not orphan emitters. Our analysis indicates that selection actively maintains a balanced polymorphism for the presence/absence of a functional lsr operon suggesting diversifying selection on the regulation of signal accumulation and recognition. These results can be explained either by niche-specific adaptation or by selection for a coercive behavior where signal-blind emitters benefit from forcing other individuals in the population to haste in cooperative behaviors.
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de Carvalho MO, Loreto ELS. Methods for detection of horizontal transfer of transposable elements in complete genomes. Genet Mol Biol 2012; 35:1078-84. [PMID: 23411916 PMCID: PMC3571429 DOI: 10.1590/s1415-47572012000600024] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Recent advances in nucleic acid sequencing technology are creating a diverse landscape for the analysis of horizontal transfer in complete genomes. Previously limited to prokaryotes, the availability of complete genomes from close eukaryotic species presents an opportunity to validate hypotheses about the patterns of evolution and mechanisms that drive horizontal transfer. Many of those methods can be transported from methods previously used in prokaryotic genomes, as the assumptions for horizontal transfer can be interpreted as the same. Some methods, however, require a complete adaptation, while others need refinements in sensitivity and specificity to deal with the huge datasets generated from next-generation sequencing technologies. Here we list the types of methods used for horizontal transfer detection, as well as theirs strengths and weakness.
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Affiliation(s)
- Marcos Oliveira de Carvalho
- Programa de Pós-Graduação em Genética e Biologia Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
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35
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Marsolier-Kergoat MC. Asymmetry indices for analysis and prediction of replication origins in eukaryotic genomes. PLoS One 2012; 7:e45050. [PMID: 23028755 PMCID: PMC3459929 DOI: 10.1371/journal.pone.0045050] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 08/15/2012] [Indexed: 01/15/2023] Open
Abstract
DNA replication was recently shown to induce the formation of compositional skews in the genomes of the yeasts Saccharomyces cerevisiae and Kluyveromyces lactis. In this work, I have characterized further GC and TA skew variations in the vicinity of S. cerevisiae replication origins and termination sites, and defined asymmetry indices for origin analysis and prediction. The presence of skew jumps at some termination sites in the S. cerevisiae genome was established. The majority of S. cerevisiae replication origins are marked by an oriented consensus sequence called ACS, but no evidence could be found for asymmetric origin firing that would be linked to ACS orientation. Asymmetry indices related to GC and TA skews were defined, and a global asymmetry index IGC,TA was described. IGC,TA was found to strongly correlate with origin efficiency in S. cerevisiae and to allow the determination of sets of intergenes significantly enriched in origin loci. The generalized use of asymmetry indices for origin prediction in naive genomes implies the determination of the direction of the skews, i.e. the identification of which strand, leading or lagging, is enriched in G and which one is enriched in T. Recent work indicates that in Candida albicans and in several related species, centromeres contain early and efficient replication origins. It has been proposed that the skew jumps observed at these positions would reflect the activity of these origins, thus allowing to determine the direction of the skews in these genomes. However, I show here that the skew jumps at C. albicans centromeres are not related to replication and that replication-associated GC and TA skews in C. albicans have in fact the opposite directions of what was proposed.
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36
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Arakawa K, Tomita M. Measures of compositional strand bias related to replication machinery and its applications. Curr Genomics 2012; 13:4-15. [PMID: 22942671 PMCID: PMC3269016 DOI: 10.2174/138920212799034749] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2011] [Revised: 09/10/2011] [Accepted: 09/20/2011] [Indexed: 11/22/2022] Open
Abstract
The compositional asymmetry of complementary bases in nucleotide sequences implies the existence of a mutational or selectional bias in the two strands of the DNA duplex, which is commonly shaped by strand-specific mechanisms in transcription or replication. Such strand bias in genomes, frequently visualized by GC skew graphs, is used for the computational prediction of transcription start sites and replication origins, as well as for comparative evolutionary genomics studies. The use of measures of compositional strand bias in order to quantify the degree of strand asymmetry is crucial, as it is the basis for determining the applicability of compositional analysis and comparing the strength of the mutational bias in different biological machineries in various species. Here, we review the measures of strand bias that have been proposed to date, including the ∆GC skew, the B1 index, the predictability score of linear discriminant analysis for gene orientation, the signal-to-noise ratio of the oligonucleotide bias, and the GC skew index. These measures have been predominantly designed for and applied to the analysis of replication-related mutational processes in prokaryotes, but we also give research examples in eukaryotes.
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Affiliation(s)
- Kazuharu Arakawa
- Institute for Advanced Biosciences, Keio University, Fujisawa 252-8520, Japan
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Baker A, Julienne H, Chen CL, Audit B, d'Aubenton-Carafa Y, Thermes C, Arneodo A. Linking the DNA strand asymmetry to the spatio-temporal replication program. I. About the role of the replication fork polarity in genome evolution. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2012; 35:92. [PMID: 23001787 DOI: 10.1140/epje/i2012-12092-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Revised: 08/08/2012] [Accepted: 08/21/2012] [Indexed: 06/01/2023]
Abstract
Two key cellular processes, namely transcription and replication, require the opening of the DNA double helix and act differently on the two DNA strands, generating different mutational patterns (mutational asymmetry) that may result, after long evolutionary time, in different nucleotide compositions on the two DNA strands (compositional asymmetry). We elaborate on the simplest model of neutral substitution rates that takes into account the strand asymmetries generated by the transcription and replication processes. Using perturbation theory, we then solve the time evolution of the DNA composition under strand-asymmetric substitution rates. In our minimal model, the compositional and substitutional asymmetries are predicted to decompose into a transcription- and a replication-associated components. The transcription-associated asymmetry increases in magnitude with transcription rate and changes sign with gene orientation while the replication-associated asymmetry is proportional to the replication fork polarity. These results are confirmed experimentally in the human genome, using substitution rates obtained by aligning the human and chimpanzee genomes using macaca and orangutan as outgroups, and replication fork polarity determined in the HeLa cell line as estimated from the derivative of the mean replication timing. When further investigating the dynamics of compositional skew evolution, we show that it is not at equilibrium yet and that its evolution is an extremely slow process with characteristic time scales of several hundred Myrs.
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Affiliation(s)
- A Baker
- Université de Lyon, Lyon, France
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38
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Abstract
The codon composition of coding sequences plays an important role in the regulation of gene expression. Herein, we report systematic differences in the usage of synonymous codons among Arabidopsis thaliana genes that are expressed specifically in distinct tissues. Although we observed that both regionally and transcriptionally associated mutational biases were associated significantly with codon bias, they could not explain the observed differences fully. Similarly, given that transcript abundances did not account for the differences in codon usage, it is unlikely that selection for translational efficiency can account exclusively for the observed codon bias. Thus, we considered the possible evolution of codon bias as an adaptive response to the different abundances of tRNAs in different tissues. Our analysis demonstrated that in some cases, codon usage in genes that were expressed in a broad range of tissues was influenced primarily by the tissue in which the gene was expressed maximally. On the basis of this finding we propose that genes that are expressed in certain tissues might show a tissue-specific compositional signature in relation to codon usage. These findings might have implications for the design of transgenes in relation to optimizing their expression.
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Kono N, Arakawa K, Tomita M. Validation of bacterial replication termination models using simulation of genomic mutations. PLoS One 2012; 7:e34526. [PMID: 22509315 PMCID: PMC3317982 DOI: 10.1371/journal.pone.0034526] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Accepted: 03/05/2012] [Indexed: 11/21/2022] Open
Abstract
In bacterial circular chromosomes and most plasmids, the replication is known to be terminated when either of the following occurs: the forks progressing in opposite directions meet at the distal end of the chromosome or the replication forks become trapped by Tus proteins bound to Ter sites. Most bacterial genomes have various polarities in their genomic structures. The most notable feature is polar genomic compositional asymmetry of the bases G and C in the leading and lagging strands, called GC skew. This asymmetry is caused by replication-associated mutation bias, and this “footprint" of the replication machinery suggests that, in contrast to the two known mechanisms, replication termination occurs near the chromosome dimer resolution site dif. To understand this difference between the known replication machinery and genomic compositional bias, we undertook a simulation study of genomic mutations, and we report here how different replication termination models contribute to the generation of replication-related genomic compositional asymmetry. Contrary to naive expectations, our results show that a single finite termination site at dif or at the GC skew shift point is not sufficient to reconstruct the genomic compositional bias as observed in published sequences. The results also show that the known replication mechanisms are sufficient to explain the position of the GC skew shift point.
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Affiliation(s)
- Nobuaki Kono
- Institute for Advanced Biosciences, Keio University, Fujisawa, Kanagawa, Japan
| | - Kazuharu Arakawa
- Institute for Advanced Biosciences, Keio University, Fujisawa, Kanagawa, Japan
- * E-mail:
| | - Masaru Tomita
- Institute for Advanced Biosciences, Keio University, Fujisawa, Kanagawa, Japan
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Namouchi A, Didelot X, Schöck U, Gicquel B, Rocha EPC. After the bottleneck: Genome-wide diversification of the Mycobacterium tuberculosis complex by mutation, recombination, and natural selection. Genome Res 2012; 22:721-34. [PMID: 22377718 DOI: 10.1101/gr.129544.111] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Many of the most virulent bacterial pathogens show low genetic diversity and sexual isolation. Accordingly, Mycobacterium tuberculosis, the deadliest human pathogen, is thought to be clonal and evolve by genetic drift. Yet, its genome shows few of the concomitant signs of genome degradation. We analyzed 24 genomes and found an excess of genetic diversity in regions encoding key adaptive functions including the type VII secretion system and the ancient horizontally transferred virulence-related regions. Four different approaches showed evident signs of recombination in M. tuberculosis. Recombination tracts add a high density of polymorphisms, and many are thus predicted to arise from outside the clade. Some of these tracts match Mycobacterium canettii sequences. Recombination introduced an excess of non-synonymous diversity in general and even more in genes expected to be under positive or diversifying selection, e.g., cell wall component genes. Mutations leading to non-synonymous SNPs are effectively purged in MTBC, which shows dominance of purifying selection. MTBC mutation bias toward AT nucleotides is not compensated by biased gene conversion, suggesting the action of natural selection also on synonymous changes. Together, all of these observations point to a strong imprint of recombination and selection in the genome affecting both non-synonymous and synonymous positions. Hence, contrary to some other pathogens and previous proposals concerning M. tuberculosis, this lineage may have come out of its ancestral bottleneck as a very successful pathogen that is rapidly diversifying by the action of mutation, recombination, and natural selection.
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Affiliation(s)
- Amine Namouchi
- Unité de Génétique Mycobactérienne, Institut Pasteur, 75015 Paris, France.
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McLean MA, Tirosh I. Opposite GC skews at the 5' and 3' ends of genes in unicellular fungi. BMC Genomics 2011; 12:638. [PMID: 22208287 PMCID: PMC3315797 DOI: 10.1186/1471-2164-12-638] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Accepted: 12/30/2011] [Indexed: 11/24/2022] Open
Abstract
Background GC-skews have previously been linked to transcription in some eukaryotes. They have been associated with transcription start sites, with the coding strand G-biased in mammals and C-biased in fungi and invertebrates. Results We show a consistent and highly significant pattern of GC-skew within genes of almost all unicellular fungi. The pattern of GC-skew is asymmetrical: the coding strand of genes is typically C-biased at the 5' ends but G-biased at the 3' ends, with intermediate skews at the middle of genes. Thus, the initiation, elongation, and termination phases of transcription are associated with different skews. This pattern influences the encoded proteins by generating differential usage of amino acids at the 5' and 3' ends of genes. These biases also affect fourfold-degenerate positions and extend into promoters and 3' UTRs, indicating that skews cannot be accounted by selection for protein function or translation. Conclusions We propose two explanations, the mutational pressure hypothesis, and the adaptive hypothesis. The mutational pressure hypothesis is that different co-factors bind to RNA pol II at different phases of transcription, producing different mutational regimes. The adaptive hypothesis is that cytidine triphosphate deficiency may lead to C-avoidance at the 3' ends of transcripts to control the flow of RNA pol II molecules and reduce their frequency of collisions.
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Affiliation(s)
- Malcolm A McLean
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
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42
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Agier N, Fischer G. The Mutational Profile of the Yeast Genome Is Shaped by Replication. Mol Biol Evol 2011; 29:905-13. [DOI: 10.1093/molbev/msr280] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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43
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Marsolier-Kergoat MC, Goldar A. DNA replication induces compositional biases in yeast. Mol Biol Evol 2011; 29:893-904. [PMID: 21948086 DOI: 10.1093/molbev/msr240] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Asymmetries intrinsic to the process of DNA replication are expected to cause differences in the substitution patterns of the leading and the lagging strands and to induce compositional biases. These biases have been detected in the majority of eubacterial genomes but rarely in eukaryotes. Only in the human genome, the activity of a minority of replication origins seems to generate compositional biases. In this work, we provide evidence for replication-associated GC and TA skews in the genomes of two yeast species, Saccharomyces cerevisiae and Kluyveromyces lactis, whereas the data for the Schizosaccharomyces pombe genome are less conclusive. In contrast with the genomes of Homo sapiens and of the majority of eubacteria, the leading strand is enriched in cytosine and adenine in both S. cerevisiae and K. lactis. We observed significant variations across the interorigin intervals of several substitution rates in the S. cerevisiae lineage since its divergence from S. paradoxus. We also found that the S. cerevisiae genome is far from compositional equilibrium and that its present compositional biases are due to substitution rates operating before its divergence from S. paradoxus. Finally, we observed that replication and transcription tend to be cooriented in the S. cerevisiae genome, especially for genes encoding subunits of protein complexes. Taken together, our results suggest that replication-related compositional biases may be a feature of many eukaryotic genomes despite the stochastic nature of the firing of replication origins in these genomes.
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44
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Charneski CA, Honti F, Bryant JM, Hurst LD, Feil EJ. Atypical at skew in Firmicute genomes results from selection and not from mutation. PLoS Genet 2011; 7:e1002283. [PMID: 21935355 PMCID: PMC3174206 DOI: 10.1371/journal.pgen.1002283] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Accepted: 07/12/2011] [Indexed: 11/18/2022] Open
Abstract
The second parity rule states that, if there is no bias in mutation or selection, then within each strand of DNA complementary bases are present at approximately equal frequencies. In bacteria, however, there is commonly an excess of G (over C) and, to a lesser extent, T (over A) in the replicatory leading strand. The low G+C Firmicutes, such as Staphylococcus aureus, are unusual in displaying an excess of A over T on the leading strand. As mutation has been established as a major force in the generation of such skews across various bacterial taxa, this anomaly has been assumed to reflect unusual mutation biases in Firmicute genomes. Here we show that this is not the case and that mutation bias does not explain the atypical AT skew seen in S. aureus. First, recently arisen intergenic SNPs predict the classical replication-derived equilibrium enrichment of T relative to A, contrary to what is observed. Second, sites predicted to be under weak purifying selection display only weak AT skew. Third, AT skew is primarily associated with largely non-synonymous first and second codon sites and is seen with respect to their sense direction, not which replicating strand they lie on. The atypical AT skew we show to be a consequence of the strong bias for genes to be co-oriented with the replicating fork, coupled with the selective avoidance of both stop codons and costly amino acids, which tend to have T-rich codons. That intergenic sequence has more A than T, while at mutational equilibrium a preponderance of T is expected, points to a possible further unresolved selective source of skew. When considering a single strand of DNA, it is not necessarily the case that the frequency of each base should equal its complementary partner, such that A = T and G = C. For the leading strand, it is typically the case that Gs are more common than Cs, and Ts more common than As. This bias is widely thought to arise due to different mutational biases during replication. The Firmicutes exhibit an atypical preference for A over T on the leading strand, and here we show that selection, rather than mutation, can explain this exception. For those bases within coding regions, selection acts to inflate the frequency of A over T in order to avoid stop codons and to use metabolically cheap amino acids. Because genes are not orientated randomly, this manifests as an overall enrichment of A on the leading strand. Furthermore, a direct examination of mutational patterns is inconsistent with the observed enrichment of As. Curiously, our data also point to an unresolved source of selection on synonymous and intergenic sites, which are widely assumed to be neutral.
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Chen CL, Duquenne L, Audit B, Guilbaud G, Rappailles A, Baker A, Huvet M, d'Aubenton-Carafa Y, Hyrien O, Arneodo A, Thermes C. Replication-associated mutational asymmetry in the human genome. Mol Biol Evol 2011; 28:2327-37. [PMID: 21368316 DOI: 10.1093/molbev/msr056] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
During evolution, mutations occur at rates that can differ between the two DNA strands. In the human genome, nucleotide substitutions occur at different rates on the transcribed and non-transcribed strands that may result from transcription-coupled repair. These mutational asymmetries generate transcription-associated compositional skews. To date, the existence of such asymmetries associated with replication has not yet been established. Here, we compute the nucleotide substitution matrices around replication initiation zones identified as sharp peaks in replication timing profiles and associated with abrupt jumps in the compositional skew profile. We show that the substitution matrices computed in these regions fully explain the jumps in the compositional skew profile when crossing initiation zones. In intergenic regions, we observe mutational asymmetries measured as differences between complementary substitution rates; their sign changes when crossing initiation zones. These mutational asymmetries are unlikely to result from cryptic transcription but can be explained by a model based on replication errors and strand-biased repair. In transcribed regions, mutational asymmetries associated with replication superimpose on the previously described mutational asymmetries associated with transcription. We separate the substitution asymmetries associated with both mechanisms, which allows us to determine for the first time in eukaryotes, the mutational asymmetries associated with replication and to reevaluate those associated with transcription. Replication-associated mutational asymmetry may result from unequal rates of complementary base misincorporation by the DNA polymerases coupled with DNA mismatch repair (MMR) acting with different efficiencies on the leading and lagging strands. Replication, acting in germ line cells during long evolutionary times, contributed equally with transcription to produce the present abrupt jumps in the compositional skew. These results demonstrate that DNA replication is one of the major processes that shape human genome composition.
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Affiliation(s)
- Chun-Long Chen
- Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique (CNRS), Gif-sur-Yvette, France
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Treangen TJ, Rocha EPC. Horizontal transfer, not duplication, drives the expansion of protein families in prokaryotes. PLoS Genet 2011; 7:e1001284. [PMID: 21298028 PMCID: PMC3029252 DOI: 10.1371/journal.pgen.1001284] [Citation(s) in RCA: 306] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Accepted: 12/20/2010] [Indexed: 01/09/2023] Open
Abstract
Gene duplication followed by neo- or sub-functionalization deeply impacts the evolution of protein families and is regarded as the main source of adaptive functional novelty in eukaryotes. While there is ample evidence of adaptive gene duplication in prokaryotes, it is not clear whether duplication outweighs the contribution of horizontal gene transfer in the expansion of protein families. We analyzed closely related prokaryote strains or species with small genomes (Helicobacter, Neisseria, Streptococcus, Sulfolobus), average-sized genomes (Bacillus, Enterobacteriaceae), and large genomes (Pseudomonas, Bradyrhizobiaceae) to untangle the effects of duplication and horizontal transfer. After removing the effects of transposable elements and phages, we show that the vast majority of expansions of protein families are due to transfer, even among large genomes. Transferred genes--xenologs--persist longer in prokaryotic lineages possibly due to a higher/longer adaptive role. On the other hand, duplicated genes--paralogs--are expressed more, and, when persistent, they evolve slower. This suggests that gene transfer and gene duplication have very different roles in shaping the evolution of biological systems: transfer allows the acquisition of new functions and duplication leads to higher gene dosage. Accordingly, we show that paralogs share most protein-protein interactions and genetic regulators, whereas xenologs share very few of them. Prokaryotes invented most of life's biochemical diversity. Therefore, the study of the evolution of biology systems should explicitly account for the predominant role of horizontal gene transfer in the diversification of protein families.
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Affiliation(s)
- Todd J Treangen
- Institut Pasteur, Microbial Evolutionary Genomics, Département Génomes et Génétique, Paris, France.
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Wei SJ, Shi M, Chen XX, Sharkey MJ, van Achterberg C, Ye GY, He JH. New views on strand asymmetry in insect mitochondrial genomes. PLoS One 2010; 5:e12708. [PMID: 20856815 PMCID: PMC2939890 DOI: 10.1371/journal.pone.0012708] [Citation(s) in RCA: 188] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Accepted: 08/20/2010] [Indexed: 01/16/2023] Open
Abstract
Strand asymmetry in nucleotide composition is a remarkable feature of animal mitochondrial genomes. Understanding the mutation processes that shape strand asymmetry is essential for comprehensive knowledge of genome evolution, demographical population history and accurate phylogenetic inference. Previous studies found that the relative contributions of different substitution types to strand asymmetry are associated with replication alone or both replication and transcription. However, the relative contributions of replication and transcription to strand asymmetry remain unclear. Here we conducted a broad survey of strand asymmetry across 120 insect mitochondrial genomes, with special reference to the correlation between the signs of skew values and replication orientation/gene direction. The results show that the sign of GC skew on entire mitochondrial genomes is reversed in all species of three distantly related families of insects, Philopteridae (Phthiraptera), Aleyrodidae (Hemiptera) and Braconidae (Hymenoptera); the replication-related elements in the A+T-rich regions of these species are inverted, confirming that reversal of strand asymmetry (GC skew) was caused by inversion of replication origin; and finally, the sign of GC skew value is associated with replication orientation but not with gene direction, while that of AT skew value varies with gene direction, replication and codon positions used in analyses. These findings show that deaminations during replication and other mutations contribute more than selection on amino acid sequences to strand compositions of G and C, and that the replication process has a stronger affect on A and T content than does transcription. Our results may contribute to genome-wide studies of replication and transcription mechanisms.
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Affiliation(s)
- Shu-Jun Wei
- State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou, China
- Institute of Plant and Environmental Protection, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Min Shi
- State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou, China
| | - Xue-Xin Chen
- State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou, China
| | - Michael J. Sharkey
- Department of Entomology, University of Kentucky, Lexington, Kentucky, United States of America
| | | | - Gong-Yin Ye
- State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou, China
| | - Jun-Hua He
- State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences, Zhejiang University, Hangzhou, China
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Hershberg R, Petrov DA. Evidence that mutation is universally biased towards AT in bacteria. PLoS Genet 2010; 6:e1001115. [PMID: 20838599 PMCID: PMC2936535 DOI: 10.1371/journal.pgen.1001115] [Citation(s) in RCA: 296] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Accepted: 08/09/2010] [Indexed: 11/19/2022] Open
Abstract
Mutation is the engine that drives evolution and adaptation forward in that it generates the variation on which natural selection acts. Mutation is a random process that nevertheless occurs according to certain biases. Elucidating mutational biases and the way they vary across species and within genomes is crucial to understanding evolution and adaptation. Here we demonstrate that clonal pathogens that evolve under severely relaxed selection are uniquely suitable for studying mutational biases in bacteria. We estimate mutational patterns using sequence datasets from five such clonal pathogens belonging to four diverse bacterial clades that span most of the range of genomic nucleotide content. We demonstrate that across different types of sites and in all four clades mutation is consistently biased towards AT. This is true even in clades that have high genomic GC content. In all studied cases the mutational bias towards AT is primarily due to the high rate of C/G to T/A transitions. These results suggest that bacterial mutational biases are far less variable than previously thought. They further demonstrate that variation in nucleotide content cannot stem entirely from variation in mutational biases and that natural selection and/or a natural selection-like process such as biased gene conversion strongly affect nucleotide content.
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Affiliation(s)
- Ruth Hershberg
- Department of Biology, Stanford University, Stanford, California, United States of America.
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Polak P, Querfurth R, Arndt PF. The evolution of transcription-associated biases of mutations across vertebrates. BMC Evol Biol 2010; 10:187. [PMID: 20565875 PMCID: PMC2927911 DOI: 10.1186/1471-2148-10-187] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Accepted: 06/18/2010] [Indexed: 02/03/2024] Open
Abstract
Background The interplay between transcription and mutational processes can lead to particular mutation patterns in transcribed regions of the genome. Transcription introduces several biases in mutational patterns; in particular it invokes strand specific mutations. In order to understand the forces that have shaped transcripts during evolution, one has to study mutation patterns associated with transcription across animals. Results Using multiple alignments of related species we estimated the regional single-nucleotide substitution patterns along genes in four vertebrate taxa: primates, rodents, laurasiatheria and bony fishes. Our analysis is focused on intronic and intergenic regions and reveals differences in the patterns of substitution asymmetries between mammals and fishes. In mammals, the levels of asymmetries are stronger for genes starting within CpG islands than in genes lacking this property. In contrast to all other species analyzed, we found a mutational pressure in dog and stickleback, promoting an increase of GC-contents in the proximity to transcriptional start sites. Conclusions We propose that the asymmetric patterns in transcribed regions are results of transcription associated mutagenic processes and transcription coupled repair, which both seem to evolve in a taxon related manner. We also discuss alternative mechanisms that can generate strand biases and involves error prone DNA polymerases and reverse transcription. A localized increase of the GC content near the transcription start site is a signature of biased gene conversion (BGC) that occurs during recombination and heteroduplex formation. Since dog and stickleback are known to be subject to rapid adaptations due to population bottlenecks and breeding, we further hypothesize that an increase in recombination rates near gene starts has been part of an adaptive process.
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Affiliation(s)
- Paz Polak
- Department of Computational Molecular Biology, Max Planck Institute for Molecular Genetics, Berlin, Germany.
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Powdel BR, Borah M, Ray SK. Strand-specific mutational bias influences codon usage of weakly expressed genes in Escherichia coli. Genes Cells 2010; 15:773-82. [PMID: 20545764 DOI: 10.1111/j.1365-2443.2010.01417.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
According to the selection-mutation-drift theory of molecular evolution, mutation predominates in determining codon usage bias (CUB) in weakly expressed genes (WEG) whereas selection predominates in determining CUB in highly expressed genes (HEG). Strand-specific mutational bias causes compositional asymmetry of the nucleotides between leading and lagging strands (LaS) in bacterial chromosomes. Keeping in view the aforementioned points, CUB between the strands were compared in Escherichia coli chromosome. In comparison with HEG, codon usage of WEG was observed to be more biased toward strands: G ending codons were significantly more in leading strands than in LaS and the reverse was true for the C ending codons. In case of WEG, the GC(3) skews were found to be significantly different between the strands. This suggests that strand-specific mutational bias influences codon usage of WEG to a greater extent than that of HEG. The differential effect of strand-specific mutational bias in E. coli might be attributed to stronger purifying selection in the HEG than the WEG. The observation here in E. coli supports the SMD theory of molecular evolution.
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Affiliation(s)
- Bhesh Raj Powdel
- Department of Mathematical Sciences, Tezpur University, Assam, India
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