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Matoulek D, Ježek B, Vohnoutová M, Symonová R. Advances in Vertebrate (Cyto)Genomics Shed New Light on Fish Compositional Genome Evolution. Genes (Basel) 2023; 14:genes14020244. [PMID: 36833171 PMCID: PMC9956151 DOI: 10.3390/genes14020244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 01/05/2023] [Indexed: 01/19/2023] Open
Abstract
Cytogenetic and compositional studies considered fish genomes rather poor in guanine-cytosine content (GC%) because of a putative "sharp increase in genic GC% during the evolution of higher vertebrates". However, the available genomic data have not been exploited to confirm this viewpoint. In contrast, further misunderstandings in GC%, mostly of fish genomes, originated from a misapprehension of the current flood of data. Utilizing public databases, we calculated the GC% in animal genomes of three different, technically well-established fractions: DNA (entire genome), cDNA (complementary DNA), and cds (exons). Our results across chordates help set borders of GC% values that are still incorrect in literature and show: (i) fish in their immense diversity possess comparably GC-rich (or even GC-richer) genomes as higher vertebrates, and fish exons are GC-enriched among vertebrates; (ii) animal genomes generally show a GC-enrichment from the DNA, over cDNA, to the cds level (i.e., not only the higher vertebrates); (iii) fish and invertebrates show a broad(er) inter-quartile range in GC%, while avian and mammalian genomes are more constrained in their GC%. These results indicate no sharp increase in the GC% of genes during the transition to higher vertebrates, as stated and numerously repeated before. We present our results in 2D and 3D space to explore the compositional genome landscape and prepared an online platform to explore the AT/GC compositional genome evolution.
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Affiliation(s)
- Dominik Matoulek
- Department of Physics, Faculty of Science, University of Hradec Králové, 500 03 Hradec Králové, Czech Republic
| | - Bruno Ježek
- Faculty of Informatics and Management, University of Hradec Králové, Rokitanského 62, 500 02 Hradec Králové, Czech Republic
| | - Marta Vohnoutová
- Department of Computer Science, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05 České Budějovice, Czech Republic
| | - Radka Symonová
- Department of Computer Science, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05 České Budějovice, Czech Republic
- Department of Bioinformatics, Wissenschaftszentrum Weihenstephan, Technische Universität München, 85354 Freising, Germany
- Institute of Hydrobiology, Biology Centre of the Czech Academy of Sciences, 370 05 České Budějovice, Czech Republic
- Correspondence:
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Whole genome assembly of the armored loricariid catfish Ancistrus triradiatus highlights herbivory signatures. Mol Genet Genomics 2022; 297:1627-1642. [PMID: 36006456 PMCID: PMC9596584 DOI: 10.1007/s00438-022-01947-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Accepted: 08/12/2022] [Indexed: 11/01/2022]
Abstract
The catfish Ancistrus triradiatus belongs to the species-rich family Loricariidae. Loricariids display remarkable traits such as herbivory, a benthic lifestyle, the absence of scales but the presence of dermal bony plates. They are exported as ornamental fish worldwide, with escaped fishes becoming a threat locally. Although genetic and phylogenetic studies are continuously increasing and developmental genetic investigations are underway, no genome assembly has been formally proposed for Loricariidae yet. We report a high-quality genome assembly of Ancistrus triradiatus using long and short reads, and a newly assembled transcriptome. The genome assembly is composed of 9530 scaffolds, including 85.6% of ray-finned fish BUSCOs, and 26,885 predicted protein-coding genes. The genomic GC content is higher than in other catfishes, reflecting the higher metabolism associated with herbivory. The examination of the SCPP gene family indicates that the genes presumably triggering scale loss when absent, are present in the scaleless A. triradiatus, questioning their explanatory role. The analysis of the opsin gene repertoire revealed that gene losses associated to the nocturnal lifestyle of catfishes were not entirely found in A. triradiatus, as the UV-sensitive opsin 5 is present. Finally, most gene family expansions were related to immunity except the gamma crystallin gene family which controls pupil shape and sub-aquatic vision. Thus, the genome of A. triradiatus reveals that fish herbivory may be related to the photic zone habitat, conditions metabolism, photoreception and visual functions. This genome is the first for the catfish suborder Loricarioidei and will serve as backbone for future genetic, developmental and conservation studies.
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Randhawa SS, Pawar R. Fish genomes and their evolution under the influence of ecology. ECOLOGICAL COMPLEXITY 2022. [DOI: 10.1016/j.ecocom.2022.100980] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Borůvková V, Howell WM, Matoulek D, Symonová R. Quantitative Approach to Fish Cytogenetics in the Context of Vertebrate Genome Evolution. Genes (Basel) 2021; 12:genes12020312. [PMID: 33671814 PMCID: PMC7926999 DOI: 10.3390/genes12020312] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 02/01/2021] [Accepted: 02/17/2021] [Indexed: 01/14/2023] Open
Abstract
Our novel Python-based tool EVANGELIST allows the visualization of GC and repeats percentages along chromosomes in sequenced genomes and has enabled us to perform quantitative large-scale analyses on the chromosome level in fish and other vertebrates. This is a different approach from the prevailing analyses, i.e., analyses of GC% in the coding sequences that make up not more than 2% in human. We identified GC content (GC%) elevations in microchromosomes in ancient fish lineages similar to avian microchromosomes and a large variability in the relationship between the chromosome size and their GC% across fish lineages. This raises the question as to what extent does the chromosome size drive GC% as posited by the currently accepted explanation based on the recombination rate. We ascribe the differences found across fishes to varying GC% of repetitive sequences. Generally, our results suggest that the GC% of repeats and proportion of repeats are independent of the chromosome size. This leaves an open space for another mechanism driving the GC evolution in vertebrates.
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Affiliation(s)
- Veronika Borůvková
- Faculty of Science, University of Hradec Kralove, 500 03 Hradec Kralove, Czech Republic; (V.B.); (D.M.)
| | - W. Mike Howell
- Department of Biological and Environmental Sciences, Samford University, Birmingham, AL 35226, USA;
| | - Dominik Matoulek
- Faculty of Science, University of Hradec Kralove, 500 03 Hradec Kralove, Czech Republic; (V.B.); (D.M.)
| | - Radka Symonová
- Department of Bioinformatics, Wissenschaftszentrum Weihenstephan, Technische Universität München, 85354 Freising, Germany
- Correspondence:
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5
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Genomes of major fishes in world fisheries and aquaculture: Status, application and perspective. AQUACULTURE AND FISHERIES 2020. [DOI: 10.1016/j.aaf.2020.05.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Canapa A, Biscotti MA, Barucca M, Carducci F, Carotti E, Olmo E. Shedding light upon the complex net of genome size, genome composition and environment in chordates. EUROPEAN ZOOLOGICAL JOURNAL 2020. [DOI: 10.1080/24750263.2020.1747558] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- A. Canapa
- Dipartimento di Scienze della Vita e dell’Ambiente, Università Politecnica delle Marche, Ancona, Italy
| | - M. A. Biscotti
- Dipartimento di Scienze della Vita e dell’Ambiente, Università Politecnica delle Marche, Ancona, Italy
| | - M. Barucca
- Dipartimento di Scienze della Vita e dell’Ambiente, Università Politecnica delle Marche, Ancona, Italy
| | - F. Carducci
- Dipartimento di Scienze della Vita e dell’Ambiente, Università Politecnica delle Marche, Ancona, Italy
| | - E. Carotti
- Dipartimento di Scienze della Vita e dell’Ambiente, Università Politecnica delle Marche, Ancona, Italy
| | - E. Olmo
- Dipartimento di Scienze della Vita e dell’Ambiente, Università Politecnica delle Marche, Ancona, Italy
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Wang Y, Zeng Z, Liu TL, Sun L, Yao Q, Chen KP. TA, GT and AC are significantly under-represented in open reading frames of prokaryotic and eukaryotic protein-coding genes. Mol Genet Genomics 2019; 294:637-647. [PMID: 30758669 DOI: 10.1007/s00438-019-01535-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 01/31/2019] [Indexed: 01/01/2023]
Abstract
Genomes can be considered a combination of 16 dinucleotides. Analysing the relative abundance of different dinucleotides may reveal important features of genome evolution. In present study, we conducted extensive surveys on the relative abundances of dinucleotides in various genomic components of 28 bacterial, 20 archaean, 19 fungal, 24 plant and 29 animal species. We found that TA, GT and AC are significantly under-represented in open reading frames of all organisms and in intergenic regions and introns of most organisms. Specific dinucleotides are of greatly varied usage at different codon positions. The significantly low representations of TA, GT and AC are considered the evolutionary consequences of preventing formation of pre-mature stop codons and of reducing intron-splicing options in candidate primary mRNA sequences. These data suggest that a reduction of TA and GT occurred on both strands of the DNA sequence at an early stage of de novo gene birth. Interestingly, GT and AC are also significantly under-represented in current prokaryotic genomes, suggesting that ancient prokaryotic protein-coding genes might have contained introns. The greatly varied usages of specific dinucleotides at different codon positions are considered evolutionary accommodations to compensate the unavailability of specific codons and to avoid formation of pre-mature stop codons. This is the first report presenting data of dinucleotide relative abundance to indicate the possible existence of spliceosomal introns in ancient prokaryotic genes and to hypothesize early steps of de novo gene birth.
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Affiliation(s)
- Yong Wang
- School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, 212013, China.
| | - Zhen Zeng
- Institute of Life Sciences, Jiangsu University, 301 Xuefu Road, Zhenjiang, 212013, China
| | - Tian-Lei Liu
- School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, 212013, China
| | - Ling Sun
- School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, 212013, China
| | - Qin Yao
- Institute of Life Sciences, Jiangsu University, 301 Xuefu Road, Zhenjiang, 212013, China
| | - Ke-Ping Chen
- Institute of Life Sciences, Jiangsu University, 301 Xuefu Road, Zhenjiang, 212013, China
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Li N, Bao L, Zhou T, Yuan Z, Liu S, Dunham R, Li Y, Wang K, Xu X, Jin Y, Zeng Q, Gao S, Fu Q, Liu Y, Yang Y, Li Q, Meyer A, Gao D, Liu Z. Genome sequence of walking catfish (Clarias batrachus) provides insights into terrestrial adaptation. BMC Genomics 2018; 19:952. [PMID: 30572844 PMCID: PMC6302426 DOI: 10.1186/s12864-018-5355-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 12/09/2018] [Indexed: 11/22/2022] Open
Abstract
Background Walking catfish (Clarias batrachus) is a freshwater fish capable of air-breathing and locomotion on land. It usually inhabits various low-oxygen habitats, burrows inside the mudflat, and sometimes “walks” to search for suitable environments during summer. It has evolved accessory air-breathing organs for respiring air and corresponding mechanisms to survive in such challenging environments. Thereby, it serves as a great model for understanding adaptations to terrestrial life. Results Comparative genomics with channel catfish (Ictalurus punctatus) revealed specific adaptations of C. batrachus in DNA repair, enzyme activator activity, and small GTPase regulator activity. Comparative analysis with 11 non-air-breathing fish species suggested adaptive evolution in gene expression and nitrogenous waste metabolic processes. Further, myoglobin, olfactory receptor related to class A G protein-coupled receptor 1, and sulfotransferase 6b1 genes were found to be expanded in the air-breathing walking catfish genome, with 15, 15, and 12 copies, respectively, compared to non-air-breathing fishes that possess only 1–2 copies of these genes. Additionally, we sequenced and compared the transcriptomes of the gill and the air-breathing organ to characterize the mechanism of aerial respiration involved in elastic fiber formation, oxygen binding and transport, angiogenesis, ion homeostasis and acid-base balance. The hemoglobin genes were expressed dramatically higher in the air-breathing organ than in the gill of walking catfish. Conclusions This study provides an important genomic resource for understanding the adaptive mechanisms of walking catfish to terrestrial environments. It is possible that the coupling of enhanced abilities for oxygen storage and oxygen transport through genomic expansion of myoglobin genes and transcriptomic up-regulation of hemoglobin and angiogenesis-related genes are important components of the molecular basis for adaptation of this aquatic species to terrestrial life. Electronic supplementary material The online version of this article (10.1186/s12864-018-5355-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ning Li
- Fish Molecular Genetics and Biotechnology Laboratory, School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA
| | - Lisui Bao
- Fish Molecular Genetics and Biotechnology Laboratory, School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA
| | - Tao Zhou
- Fish Molecular Genetics and Biotechnology Laboratory, School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA
| | - Zihao Yuan
- Fish Molecular Genetics and Biotechnology Laboratory, School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA
| | - Shikai Liu
- Fish Molecular Genetics and Biotechnology Laboratory, School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA
| | - Rex Dunham
- School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA
| | - Yuanning Li
- Department of Biological Sciences & Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University, Auburn, AL, 36849, USA
| | - Kun Wang
- Center for Ecological and Environmental Sciences, Northwestern Polytechnical University, Xi'an, 710072, China
| | - Xiaoyan Xu
- Fish Molecular Genetics and Biotechnology Laboratory, School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA
| | - Yulin Jin
- Fish Molecular Genetics and Biotechnology Laboratory, School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA
| | - Qifan Zeng
- Fish Molecular Genetics and Biotechnology Laboratory, School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA
| | - Sen Gao
- Fish Molecular Genetics and Biotechnology Laboratory, School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA
| | - Qiang Fu
- Fish Molecular Genetics and Biotechnology Laboratory, School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA
| | - Yang Liu
- Fish Molecular Genetics and Biotechnology Laboratory, School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA
| | - Yujia Yang
- Fish Molecular Genetics and Biotechnology Laboratory, School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA
| | - Qi Li
- Shellfish Genetics and Breeding Laboratory, Fisheries College, Ocean University of China, Qingdao, 266003, Shandong, China
| | - Axel Meyer
- Department of Biology, University of Konstanz, 78464, Konstanz, Germany
| | - Dongya Gao
- Fish Molecular Genetics and Biotechnology Laboratory, School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, AL, 36849, USA
| | - Zhanjiang Liu
- Department of Biology, College of Arts and Sciences, Syracuse University, Syracuse, NY, 13244, USA.
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Symonová R, Howell WM. Vertebrate Genome Evolution in the Light of Fish Cytogenomics and rDNAomics. Genes (Basel) 2018; 9:genes9020096. [PMID: 29443947 PMCID: PMC5852592 DOI: 10.3390/genes9020096] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 01/25/2018] [Accepted: 01/29/2018] [Indexed: 12/19/2022] Open
Abstract
To understand the cytogenomic evolution of vertebrates, we must first unravel the complex genomes of fishes, which were the first vertebrates to evolve and were ancestors to all other vertebrates. We must not forget the immense time span during which the fish genomes had to evolve. Fish cytogenomics is endowed with unique features which offer irreplaceable insights into the evolution of the vertebrate genome. Due to the general DNA base compositional homogeneity of fish genomes, fish cytogenomics is largely based on mapping DNA repeats that still represent serious obstacles in genome sequencing and assembling, even in model species. Localization of repeats on chromosomes of hundreds of fish species and populations originating from diversified environments have revealed the biological importance of this genomic fraction. Ribosomal genes (rDNA) belong to the most informative repeats and in fish, they are subject to a more relaxed regulation than in higher vertebrates. This can result in formation of a literal 'rDNAome' consisting of more than 20,000 copies with their high proportion employed in extra-coding functions. Because rDNA has high rates of transcription and recombination, it contributes to genome diversification and can form reproductive barrier. Our overall knowledge of fish cytogenomics grows rapidly by a continuously increasing number of fish genomes sequenced and by use of novel sequencing methods improving genome assembly. The recently revealed exceptional compositional heterogeneity in an ancient fish lineage (gars) sheds new light on the compositional genome evolution in vertebrates generally. We highlight the power of synergy of cytogenetics and genomics in fish cytogenomics, its potential to understand the complexity of genome evolution in vertebrates, which is also linked to clinical applications and the chromosomal backgrounds of speciation. We also summarize the current knowledge on fish cytogenomics and outline its main future avenues.
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Affiliation(s)
- Radka Symonová
- Faculty of Science, Department of Biology, University of Hradec Králové, 500 03 Hradec Králové, Czech Republic.
| | - W Mike Howell
- Department of Biological and Environmental Sciences, Samford University, Birmingham, AL 35229, USA.
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Symonová R, Majtánová Z, Arias-Rodriguez L, Mořkovský L, Kořínková T, Cavin L, Pokorná MJ, Doležálková M, Flajšhans M, Normandeau E, Ráb P, Meyer A, Bernatchez L. Genome Compositional Organization in Gars Shows More Similarities to Mammals than to Other Ray-Finned Fish. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2016; 328:607-619. [DOI: 10.1002/jez.b.22719] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 11/13/2016] [Accepted: 11/22/2016] [Indexed: 12/12/2022]
Affiliation(s)
- Radka Symonová
- Laboratory of Fish Genetics; Institute of Animal Physiology and Genetics; The Czech Academy of Sciences; Liběchov Czech Republic
- Department of Zoology; Faculty of Science; Charles University; Prague 2 Czech Republic
- Research Institute for Limnology; University of Innsbruck; Mondsee Austria
| | - Zuzana Majtánová
- Laboratory of Fish Genetics; Institute of Animal Physiology and Genetics; The Czech Academy of Sciences; Liběchov Czech Republic
- Department of Zoology; Faculty of Science; Charles University; Prague 2 Czech Republic
| | - Lenin Arias-Rodriguez
- División Académica de Ciencias Biológicas; Universidad Juárez Autónoma de Tabasco (UJAT); Villahermosa Tabasco México
| | - Libor Mořkovský
- Department of Zoology; Faculty of Science; Charles University; Prague 2 Czech Republic
| | - Tereza Kořínková
- Laboratory of Fish Genetics; Institute of Animal Physiology and Genetics; The Czech Academy of Sciences; Liběchov Czech Republic
| | - Lionel Cavin
- Muséum d'Histoire Naturelle; Geneva 6 Switzerland
| | - Martina Johnson Pokorná
- Laboratory of Fish Genetics; Institute of Animal Physiology and Genetics; The Czech Academy of Sciences; Liběchov Czech Republic
- Department of Ecology; Faculty of Science; Charles University; Prague 2 Czech Republic
| | - Marie Doležálková
- Laboratory of Fish Genetics; Institute of Animal Physiology and Genetics; The Czech Academy of Sciences; Liběchov Czech Republic
- Department of Zoology; Faculty of Science; Charles University; Prague 2 Czech Republic
| | - Martin Flajšhans
- Faculty of Fisheries and Protection of Waters; South Bohemian Research Centre of Aquaculture and Biodiversity of Hydrocenoses; University of South Bohemia in České Budějovice; Vodňany Czech Republic
| | - Eric Normandeau
- IBIS, Department of Biology, University Laval, Pavillon Charles-Eugène-Marchand; Avenue de la Médecine Quebec City; Canada
| | - Petr Ráb
- Laboratory of Fish Genetics; Institute of Animal Physiology and Genetics; The Czech Academy of Sciences; Liběchov Czech Republic
| | - Axel Meyer
- Chair in Zoology and Evolutionary Biology; Department of Biology; University of Konstanz; Konstanz Germany
| | - Louis Bernatchez
- IBIS, Department of Biology, University Laval, Pavillon Charles-Eugène-Marchand; Avenue de la Médecine Quebec City; Canada
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Tarallo A, Gambi MC, D'Onofrio G. Lifestyle and DNA base composition in polychaetes. Physiol Genomics 2016; 48:883-888. [PMID: 27764763 DOI: 10.1152/physiolgenomics.00018.2016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 09/27/2016] [Indexed: 11/22/2022] Open
Abstract
A comparative analysis of polychaete species, classified as motile and low-motile forms, highlighted that the former were characterized not only by a higher metabolic rate (MR), but also by a higher genomic GC content. The fluctuation of both variables was not affected by the phylogenetic relationship of the species. Thus, present results further support that a very active lifestyle affects MR and GC at the same time, showing an unexpected similarity between invertebrates and vertebrates. In teleosts, indeed, a similar pattern has been also observed in comparisons of migratory and nonmigratory species. A cause-effect link between MR and GC has not yet been proved, but the fact that the two variables are significantly linked in all the organisms so far analyzed is, most probably, of relevant biological and evolutionary meaning. The present results fit very well within the frame of the metabolic rate hypothesis proposed to explain the DNA base composition variability among organisms. On the contrary, the thermostability hypothesis was not supported. At present, no data about the recombination rate in polychaetes were available to test the biased gene conversion (BGC hypothesis).
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Affiliation(s)
- Andrea Tarallo
- Stazione Zoologica Anton Dohrn, Department of Biology and Evolution of Marine Organisms, Naples, Italy; and
| | - Maria Cristina Gambi
- Stazione Zoologica Anton Dohrn, Department of Integrative Marine Ecology (Villa Dohrn-Benthic Ecology Center), Ischia, Naples, Italy
| | - Giuseppe D'Onofrio
- Stazione Zoologica Anton Dohrn, Department of Biology and Evolution of Marine Organisms, Naples, Italy; and
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