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Najer T, Doña J, Buček A, Sweet AD, Sychra O, Johnson KP. Mitochondrial genome fragmentation is correlated with increased rates of molecular evolution. PLoS Genet 2024; 20:e1011266. [PMID: 38701107 PMCID: PMC11095710 DOI: 10.1371/journal.pgen.1011266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 05/15/2024] [Accepted: 04/20/2024] [Indexed: 05/05/2024] Open
Abstract
While mitochondrial genome content and organization is quite diverse across all Eukaryotes, most bilaterian animal mitochondrial genomes (mitogenomes) exhibit highly conserved gene content and organisation, with genes typically encoded on a single circular chromosome. However, many species of parasitic lice (Insecta: Phthiraptera) are among the notable exceptions, having mitogenomes fragmented into multiple circular chromosomes. To better understand the process of mitogenome fragmentation, we conducted a large-scale genomic study of a major group of lice, Amblycera, with extensive taxon sampling. Analyses of the evolution of mitogenome structure across a phylogenomic tree of 90 samples from 53 genera revealed evidence for multiple independent origins of mitogenome fragmentation, some inferred to have occurred less than five million years ago. We leveraged these many independent origins of fragmentation to compare the rates of DNA substitution and gene rearrangement, specifically contrasting branches with fragmented and non-fragmented mitogenomes. We found that lineages with fragmented mitochondrial genomes had significantly higher rates of mitochondrial sequence evolution. In addition, lineages with fragmented mitochondrial genomes were more likely to have mitogenome gene rearrangements than those with single-chromosome mitochondrial genomes. By combining phylogenomics and mitochondrial genomics we provide a detailed portrait of mitogenome evolution across this group of insects with a remarkably unstable mitogenome structure, identifying processes of molecular evolution that are correlated with mitogenome fragmentation.
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Affiliation(s)
- Tomáš Najer
- Department of Veterinary Sciences, Faculty of Agrobiology, Food, and Natural Resources, Czech University of Life Sciences Prague, Prague, Czechia
- Illinois Natural History Survey, Prairie Research Institute, University of Illinois Urbana-Champaign, Champaign, Illinois, United States of America
| | - Jorge Doña
- Illinois Natural History Survey, Prairie Research Institute, University of Illinois Urbana-Champaign, Champaign, Illinois, United States of America
- Departamento de Biología Animal, Universidad de Granada, Granada, Spain
| | - Aleš Buček
- Biology Centre, Czech Academy of Sciences, České Budějovice, Czechia
- Okinawa Institute of Science & Technology Graduate University, Onna-son, Okinawa, Japan
| | - Andrew D. Sweet
- Department of Biological Sciences, Arkansas State University, Jonesboro, Arkansas, United States of America
| | - Oldřich Sychra
- Department of Biology and Wildlife Diseases, Faculty of Veterinary Hygiene and Ecology, University of Veterinary Sciences Brno, Brno, Czechia
| | - Kevin P. Johnson
- Illinois Natural History Survey, Prairie Research Institute, University of Illinois Urbana-Champaign, Champaign, Illinois, United States of America
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2
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Fu YT, Shao R, Suleman, Wang W, Wang HM, Liu GH. The fragmented mitochondrial genomes of two Linognathus lice reveal active minichromosomal recombination and recombination hotspots. iScience 2023; 26:107351. [PMID: 37520725 PMCID: PMC10382929 DOI: 10.1016/j.isci.2023.107351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 06/04/2023] [Accepted: 07/06/2023] [Indexed: 08/01/2023] Open
Abstract
Evidence for recombination between mitochondrial (mt) minichromosomes has been reported in sucking lice, but it is still not clear how frequent mt minichromosomal recombination occurs. We sequenced the mt genomes of the cattle louse Linognathus vituli and the goat louse L. africanus. Both Linognathus species have 10 mt minichromosomes, and seven of them have the same gene content and gene arrangement. Comparison of mt karyotypes revealed numerous inter-minichromosomal recombination events in the evolution of Linognathus species. Minichromosome merger, gene duplication and gene translocation occurred in the lineage leading to Linognathus lice. After the divergence of L. vituli and L. africanus, duplication, degeneration, deletion and translocation of genes also occurred independently in each species. Most of the recombination events in the Linognathus species occurred upstream of either cox3 or nad2, indicating these two locations were hotspots for inter-minichromosomal recombination. Our results provide an important perspective on mt genome evolution in metazoans.
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Affiliation(s)
- Yi-Tian Fu
- Research Center for Parasites & Vectors, College of Veterinary Medicine, Hunan Agricultural University, Changsha 410128, China
| | - Renfu Shao
- Centre for Bioinnovation, School of Science, Technology and Engineering, University of the Sunshine Coast, Maroochydore, QLD 4556, Australia
| | - Suleman
- Department of Zoology, University of Swabi, Khyber Pakhtunkhwa 23430, Pakistan
| | - Wei Wang
- Centre for Bioinnovation, School of Science, Technology and Engineering, University of the Sunshine Coast, Maroochydore, QLD 4556, Australia
| | - Hui-Mei Wang
- Research Center for Parasites & Vectors, College of Veterinary Medicine, Hunan Agricultural University, Changsha 410128, China
| | - Guo-Hua Liu
- Research Center for Parasites & Vectors, College of Veterinary Medicine, Hunan Agricultural University, Changsha 410128, China
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3
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Lee Y, Cho CH, Noh C, Yang JH, Park SI, Lee YM, West JA, Bhattacharya D, Jo K, Yoon HS. Origin of minicircular mitochondrial genomes in red algae. Nat Commun 2023; 14:3363. [PMID: 37291154 PMCID: PMC10250338 DOI: 10.1038/s41467-023-39084-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 05/30/2023] [Indexed: 06/10/2023] Open
Abstract
Eukaryotic organelle genomes are generally of conserved size and gene content within phylogenetic groups. However, significant variation in genome structure may occur. Here, we report that the Stylonematophyceae red algae contain multipartite circular mitochondrial genomes (i.e., minicircles) which encode one or two genes bounded by a specific cassette and a conserved constant region. These minicircles are visualized using fluorescence microscope and scanning electron microscope, proving the circularity. Mitochondrial gene sets are reduced in these highly divergent mitogenomes. Newly generated chromosome-level nuclear genome assembly of Rhodosorus marinus reveals that most mitochondrial ribosomal subunit genes are transferred to the nuclear genome. Hetero-concatemers that resulted from recombination between minicircles and unique gene inventory that is responsible for mitochondrial genome stability may explain how the transition from typical mitochondrial genome to minicircles occurs. Our results offer inspiration on minicircular organelle genome formation and highlight an extreme case of mitochondrial gene inventory reduction.
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Affiliation(s)
- Yongsung Lee
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Korea
| | - Chung Hyun Cho
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Korea
| | - Chanyoung Noh
- Department of Chemistry, Sogang University, Seoul, 04107, Korea
| | - Ji Hyun Yang
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Korea
| | - Seung In Park
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Korea
| | - Yu Min Lee
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Korea
| | - John A West
- School of Biosciences 2, University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Debashish Bhattacharya
- Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, 08901, USA
| | - Kyubong Jo
- Department of Chemistry, Sogang University, Seoul, 04107, Korea.
| | - Hwan Su Yoon
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 16419, Korea.
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Sharbrough J, Bankers L, Cook E, Fields PD, Jalinsky J, McElroy KE, Neiman M, Logsdon JM, Boore JL. Single-molecule Sequencing of an Animal Mitochondrial Genome Reveals Chloroplast-like Architecture and Repeat-mediated Recombination. Mol Biol Evol 2023; 40:6980790. [PMID: 36625177 PMCID: PMC9874032 DOI: 10.1093/molbev/msad007] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 12/28/2022] [Accepted: 01/05/2023] [Indexed: 01/11/2023] Open
Abstract
Recent advances in long-read sequencing technology have allowed for single-molecule sequencing of entire mitochondrial genomes, opening the door for direct investigation of the mitochondrial genome architecture and recombination. We used PacBio sequencing to reassemble mitochondrial genomes from two species of New Zealand freshwater snails, Potamopyrgus antipodarum and Potamopyrgus estuarinus. These assemblies revealed a ∼1.7 kb structure within the mitochondrial genomes of both species that was previously undetected by an assembly of short reads and likely corresponding to a large noncoding region commonly present in the mitochondrial genomes. The overall architecture of these Potamopyrgus mitochondrial genomes is reminiscent of the chloroplast genomes of land plants, harboring a large single-copy (LSC) region and a small single-copy (SSC) region separated by a pair of inverted repeats (IRa and IRb). Individual sequencing reads that spanned across the Potamopyrgus IRa-SSC-IRb structure revealed the occurrence of a "flip-flop" recombination. We also detected evidence for two distinct IR haplotypes and recombination between them in wild-caught P. estuarinus, as well as extensive intermolecular recombination between single-nucleotide polymorphisms in the LSC region. The chloroplast-like architecture and repeat-mediated mitochondrial recombination we describe here raise fundamental questions regarding the origins and commonness of inverted repeats in cytoplasmic genomes and their role in mitochondrial genome evolution.
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Affiliation(s)
| | - Laura Bankers
- Department of Biology, University of Iowa, Iowa City, IA
| | - Emily Cook
- Department of Biology, New Mexico Institute of Mining and Technology, Socorro, NM 87801
| | - Peter D Fields
- Zoologisches Institut, University of Basel, Basel, Switzerland
| | | | - Kyle E McElroy
- Department of Biology, University of Iowa, Iowa City, IA,Department of Ecology, Evolution, and Organismal Biology, Iowa State University, IA
| | - Maurine Neiman
- Department of Biology, University of Iowa, Iowa City, IA
| | - John M Logsdon
- Department of Biology, University of Iowa, Iowa City, IA
| | - Jeffrey L Boore
- Phenome Health and Institute for Systems Biology, Seattle, WA
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Ghavami MB, Ghanbari M, Panahi S, Taghiloo B. Diversity of mitochondrial genes and predominance of Clade B in different head lice populations in the northwest of Iran. Parasit Vectors 2020; 13:485. [PMID: 32967705 PMCID: PMC7510113 DOI: 10.1186/s13071-020-04364-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Accepted: 09/15/2020] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The head louse, Pediculus humanus capitis, is the most important ectoparasite causing many health problems. Several linkages are presented for this parasite, each representing a particular geographical distribution, prevalence rate, vector competence, susceptibility to pediculicides, and infestation rate. Determining the genetic nature of these linkages is necessary to identify the population structure and also to develop and monitor control programmes against head lice. This study was designed to analyse cox1 and cytb genes and determine the mitochondrial clades in head lice populations in the northwest of Iran. METHODS Adult head lice were collected from infested females of Ardabil, East and West Azerbaijan, and Zanjan Provinces from 2016 to 2018. Partial fragments of the mitochondrial genes cox1 and cytb were amplified by PCR and some of the amplicons were sequenced. All confirmed sequences were analysed, and the frequency of each mitochondrial clade was determined in the studied areas. RESULTS A total of 6410 females were clinically examined, and 897 adult head lice were collected from 562 infested cases. Genomic DNA was extracted from 417 samples, and fragments of cox1 and cytb genes were amplified in 348 individuals. Analysis of the 116 sequences showed the 632-bp and 495-bp fragments for cox1 and cytb genes, respectively. The nucleotide and haplotype diversities of cytb and cox1 genes were 0.02261 and 0.589 and 0.01443 and 0.424, respectively. Sequence analysis indicated 6 haplotypes clustered in two clades, A and B. The relative prevalence of clade B was 73% for cytb and 82% for cox1 gene. Haplotypes of clade B were found in all the studied areas, while those of clade A were observed only in rural and suburban areas. CONCLUSIONS To our knowledge, this is the first study investigated deeply the field populations of Pediculus and documented two clades in the Middle East. The considerable prevalence of pediculosis in the studied areas requires authorities' attention to establish effective control and preventive measures. Given the role of cytb in monitoring population groups, application of this marker is suggested for future epigenetic studies to evaluate the factors affecting the abundance of these clades.
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Affiliation(s)
- Mohammad Bagher Ghavami
- Department of Medical Entomology and Vector Control, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran.
| | - Maryam Ghanbari
- Department of Medical Entomology and Vector Control, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran
| | - Sanaz Panahi
- Department of Medical Entomology and Vector Control, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran
| | - Behrooz Taghiloo
- Department of Medical Entomology and Vector Control, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran
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Song F, Li H, Liu GH, Wang W, James P, Colwell DD, Tran A, Gong S, Cai W, Shao R. Mitochondrial Genome Fragmentation Unites the Parasitic Lice of Eutherian Mammals. Syst Biol 2019; 68:430-440. [PMID: 30239978 PMCID: PMC6472445 DOI: 10.1093/sysbio/syy062] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 09/11/2018] [Accepted: 09/12/2018] [Indexed: 11/13/2022] Open
Abstract
Organelle genome fragmentation has been found in a wide range of eukaryotic lineages; however, its use in phylogenetic reconstruction has not been demonstrated. We explored the use of mitochondrial (mt) genome fragmentation in resolving the controversial suborder-level phylogeny of parasitic lice (order Phthiraptera). There are approximately 5000 species of parasitic lice in four suborders (Amblycera, Ischnocera, Rhynchophthirina, and Anoplura), which infest mammals and birds. The phylogenetic relationships among these suborders are unresolved despite decades of studies. We sequenced the mt genomes of eight species of parasitic lice and compared them with 17 other species of parasitic lice sequenced previously. We found that the typical single-chromosome mt genome is retained in the lice of birds but fragmented into many minichromosomes in the lice of eutherian mammals. The shared derived feature of mt genome fragmentation unites the eutherian mammal lice of Ischnocera (family Trichodectidae) with Anoplura and Rhynchophthirina to the exclusion of the bird lice of Ischnocera (family Philopteridae). The novel clade, namely Mitodivisia, is also supported by phylogenetic analysis of mt genome and cox1 gene sequences. Our results demonstrate, for the first time, that organelle genome fragmentation is informative for resolving controversial high-level phylogenies.
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Affiliation(s)
- Fan Song
- Key Laboratory of Pest Monitoring and Green Management, Ministry of Agriculture, Department of Entomology, College of Plant Protection, China Agricultural University, Beijing 100193, China
| | - Hu Li
- Key Laboratory of Pest Monitoring and Green Management, Ministry of Agriculture, Department of Entomology, College of Plant Protection, China Agricultural University, Beijing 100193, China
| | - Guo-Hua Liu
- Hunan Provincial Key Laboratory of Protein Engineering in Animal Vaccines, College of Veterinary Medicine, Hunan Agricultural University, Changsha, Hunan Province 410128, China
| | - Wei Wang
- School of Science and Engineering, GeneCology Research Centre, Animal Research Centre, University of the Sunshine Coast, Sippy Downs, Queensland 4556, Australia
| | - Peter James
- Queensland Alliance for Agriculture and Food Innovation, University of Queensland, Dutton Park, Queensland, Australia
| | - Douglas D Colwell
- Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada
| | - Anette Tran
- School of Science and Engineering, GeneCology Research Centre, Animal Research Centre, University of the Sunshine Coast, Sippy Downs, Queensland 4556, Australia
| | - Siyu Gong
- Key Laboratory of Pest Monitoring and Green Management, Ministry of Agriculture, Department of Entomology, College of Plant Protection, China Agricultural University, Beijing 100193, China
| | - Wanzhi Cai
- Key Laboratory of Pest Monitoring and Green Management, Ministry of Agriculture, Department of Entomology, College of Plant Protection, China Agricultural University, Beijing 100193, China
| | - Renfu Shao
- School of Science and Engineering, GeneCology Research Centre, Animal Research Centre, University of the Sunshine Coast, Sippy Downs, Queensland 4556, Australia
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Shao R, Li H, Barker SC, Song S. The Mitochondrial Genome of the Guanaco Louse, Microthoracius praelongiceps: Insights into the Ancestral Mitochondrial Karyotype of Sucking Lice (Anoplura, Insecta). Genome Biol Evol 2018; 9:431-445. [PMID: 28164215 PMCID: PMC5381627 DOI: 10.1093/gbe/evx007] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/31/2017] [Indexed: 11/13/2022] Open
Abstract
Fragmented mitochondrial (mt) genomes have been reported in 11 species of sucking lice (suborder Anoplura) that infest humans, chimpanzees, pigs, horses, and rodents. There is substantial variation among these lice in mt karyotype: the number of minichromosomes of a species ranges from 9 to 20; the number of genes in a minichromosome ranges from 1 to 8; gene arrangement in a minichromosome differs between species, even in the same genus. We sequenced the mt genome of the guanaco louse, Microthoracius praelongiceps, to help establish the ancestral mt karyotype for sucking lice and understand how fragmented mt genomes evolved. The guanaco louse has 12 mt minichromosomes; each minichromosome has 2-5 genes and a non-coding region. The guanaco louse shares many features with rodent lice in mt karyotype, more than with other sucking lice. The guanaco louse, however, is more closely related phylogenetically to human lice, chimpanzee lice, pig lice, and horse lice than to rodent lice. By parsimony analysis of shared features in mt karyotype, we infer that the most recent common ancestor of sucking lice, which lived ∼75 Ma, had 11 minichromosomes; each minichromosome had 1-6 genes and a non-coding region. As sucking lice diverged, split of mt minichromosomes occurred many times in the lineages leading to the lice of humans, chimpanzees, and rodents whereas merger of minichromosomes occurred in the lineage leading to the lice of pigs and horses. Together, splits and mergers of minichromosomes created a very complex and dynamic mt genome organization in the sucking lice.
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Affiliation(s)
- Renfu Shao
- GeneCology Research Centre, School of Science and Engineering, Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore, Queensland, Australia
| | - Hu Li
- Department of Entomology, China Agricultural University, Beijing, China
| | - Stephen C Barker
- Parasitology Section, School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, Queensland, Australia
| | - Simon Song
- GeneCology Research Centre, School of Science and Engineering, Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore, Queensland, Australia
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Yahalomi D, Haddas-Sasson M, Rubinstein ND, Feldstein T, Diamant A, Huchon D. The Multipartite Mitochondrial Genome of Enteromyxum leei (Myxozoa): Eight Fast-Evolving Megacircles. Mol Biol Evol 2017; 34:1551-1556. [PMID: 28333349 DOI: 10.1093/molbev/msx072] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Myxozoans are a large group of poorly characterized cnidarian parasites. To gain further insight into their evolution, we sequenced the mitochondrial (mt) genome of Enteromyxum leei and reevaluate the mt genome structure of Kudoa iwatai. Although the typical animal mt genome is a compact, 13-25 kb, circular chromosome, the mt genome of E. leei was found to be fragmented into eight circular chromosomes of ∼23 kb, making it the largest described animal mt genome. Each chromosome was found to harbor a large noncoding region (∼15 kb), nearly identical between chromosomes. The protein coding genes show an unusually high rate of sequence evolution and possess little similarity to their cnidarian homologs. Only five protein coding genes could be identified and no tRNA genes. Surprisingly, the mt genome of K. iwatai was also found to be composed of two chromosomes. These observations confirm the remarkable plasticity of myxozoan mt genomes.
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Affiliation(s)
- Dayana Yahalomi
- Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Michal Haddas-Sasson
- Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Nimrod D Rubinstein
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Tamar Feldstein
- Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.,The Steinhardt Museum of Natural History and Israel National Center for Biodiversity Studies, Tel Aviv University, Tel Aviv, Israel
| | - Arik Diamant
- National Center for Mariculture, Israel Oceanographic and Limnological Research, Eilat, Israel
| | - Dorothée Huchon
- Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.,The Steinhardt Museum of Natural History and Israel National Center for Biodiversity Studies, Tel Aviv University, Tel Aviv, Israel
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Fragmented mitochondrial genomes in two suborders of parasitic lice of eutherian mammals (Anoplura and Rhynchophthirina, Insecta). Sci Rep 2015; 5:17389. [PMID: 26617060 PMCID: PMC4663631 DOI: 10.1038/srep17389] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 10/29/2015] [Indexed: 11/26/2022] Open
Abstract
Parasitic lice (order Phthiraptera) infest birds and mammals. The typical animal mitochondrial (mt) genome organization, which consists of a single chromosome with 37 genes, was found in chewing lice in the suborders Amblycera and Ischnocera. The sucking lice (suborder Anoplura) known, however, have fragmented mt genomes with 9–20 minichromosomes. We sequenced the mt genome of the elephant louse, Haematomyzus elephantis – the first species of chewing lice investigated from the suborder Rhynchophthirina. We identified 33 mt genes in the elephant louse, which were on 10 minichromosomes. Each minichromosome is 3.5–4.2 kb in size and has 2–6 genes. Phylogenetic analyses of mt genome sequences confirm that the elephant louse is more closely related to sucking lice than to the chewing lice in the Amblycera and Ischnocera. Our results indicate that mt genome fragmentation is shared by the suborders Anoplura and Rhynchophthirina. Nine of the 10 mt minichromosomes of the elephant louse differ from those of the sucking lice (Anoplura) known in gene content and gene arrangement, indicating that distinct mt karyotypes have evolved in Anoplura and Rhynchophthirina since they diverged ~92 million years ago.
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Dickey AM, Kumar V, Morgan JK, Jara-Cavieres A, Shatters RG, McKenzie CL, Osborne LS. A novel mitochondrial genome architecture in thrips (Insecta: Thysanoptera): extreme size asymmetry among chromosomes and possible recent control region duplication. BMC Genomics 2015; 16:439. [PMID: 26055161 PMCID: PMC4460840 DOI: 10.1186/s12864-015-1672-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 05/29/2015] [Indexed: 11/19/2022] Open
Abstract
Background Multipartite mitochondrial genomes are very rare in animals but have been found previously in two insect orders with highly rearranged genomes, the Phthiraptera (parasitic lice), and the Psocoptera (booklice/barklice). Results We provide the first report of a multipartite mitochondrial genome architecture in a third order with highly rearranged genomes: Thysanoptera (thrips). We sequenced the complete mitochondrial genomes of two divergent members of the Scirtothrips dorsalis cryptic species complex. The East Asia 1 species has the single circular chromosome common to animals while the South Asia 1 species has a genome consisting of two circular chromosomes. The fragmented South Asia 1 genome exhibits extreme chromosome size asymmetry with the majority of genes on the large, 14.28 kb, chromosome and only nad6 and trnC on the 0.92 kb mini-circle chromosome. This genome also features paralogous control regions with high similarity suggesting a very recent origin of the nad6 mini-circle chromosome in the South Asia 1 cryptic species. Conclusions Thysanoptera, along with the other minor paraenopteran insect orders should be considered models for rapid mitochondrial genome evolution, including fragmentation. Continued use of these models will facilitate a greater understanding of recombination and other mitochondrial genome evolutionary processes across eukaryotes. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1672-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Aaron M Dickey
- Subtropical Insects Research Unit, US Horticultural Research Laboratory, Fort Pierce, USA. .,Mid-Florida Research & Education Center, University of Florida, Apopka, USA. .,Present Address: Agricultural Research Service, US Department of Agriculture, Clay Center, USA.
| | - Vivek Kumar
- Subtropical Insects Research Unit, US Horticultural Research Laboratory, Fort Pierce, USA. .,Mid-Florida Research & Education Center, University of Florida, Apopka, USA.
| | - J Kent Morgan
- Subtropical Insects Research Unit, US Horticultural Research Laboratory, Fort Pierce, USA. .,Present Address: J. Kent Morgan Consulting, Fort Pierce, USA.
| | | | - Robert G Shatters
- Subtropical Insects Research Unit, US Horticultural Research Laboratory, Fort Pierce, USA. .,US Department of Agriculture, Agricultural Research Service, Fort Pierce, USA.
| | - Cindy L McKenzie
- Subtropical Insects Research Unit, US Horticultural Research Laboratory, Fort Pierce, USA. .,US Department of Agriculture, Agricultural Research Service, Fort Pierce, USA.
| | - Lance S Osborne
- Mid-Florida Research & Education Center, University of Florida, Apopka, USA.
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Chen SC, Wei DD, Shao R, Shi JX, Dou W, Wang JJ. Evolution of multipartite mitochondrial genomes in the booklice of the genus Liposcelis (Psocoptera). BMC Genomics 2014; 15:861. [PMID: 25282613 PMCID: PMC4197233 DOI: 10.1186/1471-2164-15-861] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 09/29/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The genus Liposcelis (Psocoptera: Troctomorpha) has more than 120 species with a worldwide distribution and they pose a risk for global food security. The organization of mitochondrial (mt) genomes varies between the two species of booklice investigated in the genus Liposcelis. Liposcelis decolor has its mt genes on a single chromosome, like most other insects; L. bostrychophila, however, has a multipartite mt genome with genes on two chromosomes. RESULTS To understand how multipartite mt genome organization evolved in the genus Liposcelis, we sequenced the mt genomes of L. entomophila and L. paeta in this study. We found that these two species of booklice also have multipartite mt genomes, like L. bostrychophila, with the mt genes we identified on two chromosomes. Numerous pseudo mt genes and non-coding regions were found in the mt genomes of these two booklice, and account for 30% and 10% respectively of the entire length we sequenced. In L. bostrychophila, the mt genes are distributed approximately equally between the two chromosomes. In L. entomophila and L. paeta, however, one mt chromosome has most of the genes we identified whereas the other chromosome has largely pseudogenes and non-coding regions. L. entomophila and L. paeta differ substantially from each other and from L. bostrychophila in gene content and gene arrangement in their mt chromosomes. CONCLUSIONS Our results indicate unusually fast evolution in mt genome organization in the booklice of the genus Liposcelis, and reveal different patterns of mt genome fragmentation among L. bostrychophila, L. entomophila and L. paeta.
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Affiliation(s)
| | | | | | | | | | - Jin-Jun Wang
- Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing, P, R, China.
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Dong WG, Song S, Guo XG, Jin DC, Yang Q, Barker SC, Shao R. Fragmented mitochondrial genomes are present in both major clades of the blood-sucking lice (suborder Anoplura): evidence from two Hoplopleura rodent lice (family Hoplopleuridae). BMC Genomics 2014; 15:751. [PMID: 25179395 PMCID: PMC4158074 DOI: 10.1186/1471-2164-15-751] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 08/20/2014] [Indexed: 11/30/2022] Open
Abstract
Background The suborder Anoplura contains 540 species of blood-sucking lice that parasitize over 840 species of eutherian mammals. Fragmented mitochondrial (mt) genomes have been found in the lice of humans, pigs, horses and rats from four families: Pediculidae, Pthiridae, Haematopinidae and Polyplacidae. These lice, eight species in total, are from the same major clade of the Anoplura. The mt genomes of these lice consist of 9–20 minichromosomes; each minichromosome is 1.5–4 kb in size and has 1–8 genes. To understand mt genome fragmentation in the other major clade of the Anoplura, we sequenced the mt genomes of two species of rodent lice in the genus Hoplopleura (family Hoplopleuridae). Results We identified 28 mt genes on 10 minichromosomes in the mouse louse, Ho. akanezumi; each minichromosome is 1.7–2.7 kb long and has 1–6 genes. We identified 34 mt genes on 11 minichromosomes in the rat louse, Ho. kitti; each minichromosome is 1.8–2.8 kb long and has 1–5 genes. Ho. akanezumi also has a chimeric minichromosome with parts of two rRNA genes and a full-length tRNA gene for tyrosine. These two rodent lice share the same pattern for the distribution of all of the protein-coding and rRNA genes but differ in tRNA gene content and gene arrangement in four minichromosomes. Like the four genera of blood-sucking lice that have been investigated in previous studies, the Hoplopleura species have four minichromosomes that are only found in this genus. Conclusions Our results indicate that fragmented mt genomes were present in the most recent common ancestor of the two major clades of the blood-sucking lice, which lived ~75 million years ago. Intra-genus variation in the pattern of mt genome fragmentation is common in the blood-sucking lice (suborder Anoplura) and genus-specific minichromosomes are potential synapomorphies. Future studies should expand into more species, genera and families of blood-sucking lice to explore further the phylogenetic utility of the novel features associated with fragmented mt genomes. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-751) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | - Xian-Guo Guo
- Institute of Pathogens and Vectors, Dali University, and Yunnan Provincial Key Laboratory for Zoonosis Control, Dali, China.
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Song SD, Barker SC, Shao R. Variation in mitochondrial minichromosome composition between blood-sucking lice of the genus Haematopinus that infest horses and pigs. Parasit Vectors 2014; 7:144. [PMID: 24690192 PMCID: PMC4022054 DOI: 10.1186/1756-3305-7-144] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Accepted: 03/02/2014] [Indexed: 08/30/2023] Open
Abstract
BACKGROUND The genus Haematopinus contains 21 species of blood-sucking lice, parasitizing both even-toed ungulates (pigs, cattle, buffalo, antelopes, camels and deer) and odd-toed ungulates (horses, donkeys and zebras). The mitochondrial genomes of the domestic pig louse, Haematopinus suis, and the wild pig louse, Haematopinus apri, have been sequenced recently; both lice have fragmented mitochondrial genomes with 37 genes on nine minichromosomes. To understand whether the composition of mitochondrial minichromosomes and the gene content and gene arrangement of each minichromosome are stable within the genus, we sequenced the mitochondrial genome of the horse louse, Haematopinus asini. METHODS We used a PCR-based strategy to amplify four mitochondrial minichromosomes in near full-length, and then amplify the entire coding regions of all of the nine mitochondrial minichromosomes of the horse louse. These amplicons were sequenced with an Illumina Hiseq platform. RESULTS We identified all of the 37 mitochondrial genes typical of bilateral animals in the horse louse, Haematopinus asini; these genes are on nine circular minichromosomes. Each minichromosome is 3.5-5.0 kb in size and consists of a coding region and a non-coding region except R-nad4L-rrnS-C minichromosome, which contains two coding regions and two non-coding regions. Six of the nine minichromosomes of the horse louse have their counterparts in the pig lice with the same gene content and gene arrangement. However, the gene content and arrangement of the other three minichromosomes of the horse louse, including R-nad4L-rrnS-C, are different from that of the other three minichromosomes of the pig lice. CONCLUSIONS Comparison between the horse louse and the pig lice revealed variation in the composition of mitochondrial minichromosomes within the genus Haematopinus, which can be accounted for by gene translocation events between minichromosomes. The current study indicates that inter-minichromosome recombination plays a major role in generating the variation in the composition of mitochondrial minichromosomes and provides novel insights into the evolution of fragmented mitochondrial genomes in the blood-sucking lice.
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Affiliation(s)
- Simon D Song
- GeneCology Research Centre, Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore, Queensland 4556, Australia.
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Jiang H, Barker SC, Shao R. Substantial variation in the extent of mitochondrial genome fragmentation among blood-sucking lice of mammals. Genome Biol Evol 2013; 5:1298-308. [PMID: 23781098 PMCID: PMC3730346 DOI: 10.1093/gbe/evt094] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Blood-sucking lice of humans have extensively fragmented mitochondrial (mt) genomes. Human head louse and body louse have their 37 mt genes on 20 minichromosomes. In human pubic louse, the 34 mt genes known are on 14 minichromosomes. To understand the process of mt genome fragmentation in the blood-sucking lice of mammals, we sequenced the mt genomes of the domestic pig louse, Haematopinus suis, and the wild pig louse, H. apri, which diverged from human lice approximately 65 Ma. The 37 mt genes of the pig lice are on nine circular minichromosomes; each minichromosome is 3–4 kb in size. The pig lice have four genes per minichromosome on average, in contrast to two genes per minichromosome in the human lice. One minichromosome of the pig lice has eight genes and is the most gene-rich minichromosome found in the sucking lice. Our results indicate substantial variation in the rate and extent of mt genome fragmentation among different lineages of the sucking lice.
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Affiliation(s)
- Haowei Jiang
- Parasitology Section, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
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15
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Cameron SL. Insect mitochondrial genomics: implications for evolution and phylogeny. ANNUAL REVIEW OF ENTOMOLOGY 2013; 59:95-117. [PMID: 24160435 DOI: 10.1146/annurev-ento-011613-162007] [Citation(s) in RCA: 853] [Impact Index Per Article: 77.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The mitochondrial (mt) genome is, to date, the most extensively studied genomic system in insects, outnumbering nuclear genomes tenfold and representing all orders versus very few. Phylogenomic analysis methods have been tested extensively, identifying compositional bias and rate variation, both within and between lineages, as the principal issues confronting accurate analyses. Major studies at both inter- and intraordinal levels have contributed to our understanding of phylogenetic relationships within many groups. Genome rearrangements are an additional data type for defining relationships, with rearrangement synapomorphies identified across multiple orders and at many different taxonomic levels. Hymenoptera and Psocodea have greatly elevated rates of rearrangement offering both opportunities and pitfalls for identifying rearrangement synapomorphies in each group. Finally, insects are model systems for studying aberrant mt genomes, including truncated tRNAs and multichromosomal genomes. Greater integration of nuclear and mt genomic studies is necessary to further our understanding of insect genomic evolution.
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Affiliation(s)
- Stephen L Cameron
- Earth, Environmental & Biological Sciences School, Science & Engineering Faculty, Queensland University of Technology, Brisbane, QLD 4001, Australia;
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Shao R, Zhu XQ, Barker SC, Herd K. Evolution of extensively fragmented mitochondrial genomes in the lice of humans. Genome Biol Evol 2013; 4:1088-101. [PMID: 23042553 PMCID: PMC3514963 DOI: 10.1093/gbe/evs088] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Bilateral animals are featured by an extremely compact mitochondrial (mt) genome with 37 genes on a single circular chromosome. The human body louse, Pediculus humanus, however, has its mt genes on 20 minichromosomes. We sequenced the mt genomes of two other human lice: the head louse, P. capitis, and the pubic louse, Pthirus pubis. Comparison among the three human lice revealed the presence of fragmented mt genomes in their most recent common ancestor, which lived ∼7 Ma. The head louse has exactly the same set of mt minichromosomes as the body louse, indicating that the number of minichromosomes, and the gene content and gene arrangement in each minichromosome have remained unchanged since the body louse evolved from the head louse ∼107,000 years ago. The pubic louse has the same pattern of one protein-coding or rRNA gene per minichromosome (except one minichromosome with two protein-coding genes, atp6 and atp8) as the head louse and the body louse. This pattern is apparently ancestral to all human lice and has been stable for at least 7 Myr. Most tRNA genes of the pubic louse, however, are on different minichromosomes when compared with their counterparts in the head louse and the body louse. It is evident that rearrangement of four tRNA genes (for leucine, arginine and glycine) was due to gene-identity switch by point mutation at the third anticodon position or by homologous recombination, whereas rearrangement of other tRNA genes was by gene translocation between minichromosomes, likely caused by minichromosome split via gene degeneration and deletion.
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Affiliation(s)
- Renfu Shao
- GeneCology Research Group, School of Science, Education and Engineering, University of the Sunshine Coast, Maroochydore, Queensland, Australia.
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Bernt M, Braband A, Schierwater B, Stadler PF. Genetic aspects of mitochondrial genome evolution. Mol Phylogenet Evol 2012; 69:328-38. [PMID: 23142697 DOI: 10.1016/j.ympev.2012.10.020] [Citation(s) in RCA: 161] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2012] [Revised: 10/20/2012] [Accepted: 10/22/2012] [Indexed: 11/30/2022]
Abstract
Many years of extensive studies of metazoan mitochondrial genomes have established differences in gene arrangements and genetic codes as valuable phylogenetic markers. Understanding the underlying mechanisms of replication, transcription and the role of the control regions which cause e.g. different gene orders is important to assess the phylogenetic signal of such events. This review summarises and discusses, for the Metazoa, the general aspects of mitochondrial transcription and replication with respect to control regions as well as several proposed models of gene rearrangements. As whole genome sequencing projects accumulate, more and more observations about mitochondrial gene transfer to the nucleus are reported. Thus occurrence and phylogenetic aspects concerning nuclear mitochondrial-like sequences (NUMTS) is another aspect of this review.
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Affiliation(s)
- Matthias Bernt
- Parallel Computing and Complex Systems Group, Department of Computer Science, University of Leipzig, Augustusplatz 10, D-04109 Leipzig, Germany.
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Veracx A, Raoult D. Biology and genetics of human head and body lice. Trends Parasitol 2012; 28:563-71. [PMID: 23069652 DOI: 10.1016/j.pt.2012.09.003] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 09/13/2012] [Accepted: 09/15/2012] [Indexed: 10/27/2022]
Abstract
Head lice and body lice have distinct ecologies and differ slightly in morphology and biology, questioning their taxonomic status. Over the past 10 years many genetic studies have been undertaken. Controversial data suggest that not only body lice but also head lice can serve as vectors of Bartonella quintana, and a better understanding of louse epidemiology is crucial. Here, we review taxonomic studies based on biology and genetics, including genomic data on lice, lice endosymbionts, and louse-transmitted bacteria. We recommend that studies of human lice employ morphological and biological characteristics in conjunction with transcriptomic date because lice seem to differ mainly in gene expression (and not in gene content), leading to different phenotypes.
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Affiliation(s)
- Aurélie Veracx
- Aix Marseille Université, Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), Unité Mixte de Recherche (UMR) 63, Centre National de la Recherche Scientifique (CNRS) 7278, Institut de Recherche pour le Développement (IRD) 198, Institut National de la Santé et de la Recherche Médicale (INSERM) 1095, 13005 Marseille, France
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Boyd B, Reed D. Taxonomy of lice and their endosymbiotic bacteria in the post-genomic era. Clin Microbiol Infect 2012; 18:324-31. [DOI: 10.1111/j.1469-0691.2012.03782.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Georgiades K, Raoult D. The rhizome of Reclinomonas americana, Homo sapiens, Pediculus humanus and Saccharomyces cerevisiae mitochondria. Biol Direct 2011; 6:55. [PMID: 22014084 PMCID: PMC3214132 DOI: 10.1186/1745-6150-6-55] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Accepted: 10/20/2011] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Mitochondria are thought to have evolved from eubacteria-like endosymbionts; however, the origin of the mitochondrion remains a subject of debate. In this study, we investigated the phenomenon of chimerism in mitochondria to shed light on the origin of these organelles by determining which species played a role in their formation. We used the mitochondria of four distinct organisms, Reclinomonas americana, Homo sapiens, Saccharomyces cerevisiae and multichromosome Pediculus humanus, and attempted to identify the origin of each mitochondrial gene. RESULTS Our results suggest that the origin of mitochondrial genes is not limited to the Rickettsiales and that the creation of these genes did not occur in a single event, but through multiple successive events. Some of these events are very old and were followed by events that are more recent and occurred through the addition of elements originating from current species. The points in time that the elements were added and the parental species of each gene in the mitochondrial genome are different to the individual species. These data constitute strong evidence that mitochondria do not have a single common ancestor but likely have numerous ancestors, including proto-Rickettsiales, proto-Rhizobiales and proto-Alphaproteobacteria, as well as current alphaproteobacterial species. The analysis of the multichromosome P. humanus mitochondrion supports this mechanism. CONCLUSIONS The most plausible scenario of the origin of the mitochondrion is that ancestors of Rickettsiales and Rhizobiales merged in a proto-eukaryotic cell approximately one billion years ago. The fusion of the Rickettsiales and Rhizobiales cells was followed by gene loss, genomic rearrangements and the addition of alphaproteobacterial elements through ancient and more recent recombination events. Each gene of each of the four studied mitochondria has a different origin, while in some cases, multichromosomes may allow for enhanced gene exchange. Therefore, the tree of life is not sufficient to explain the chimeric structure of current genomes, and the theory of a single common ancestor and a top-down tree does not reflect our current state of knowledge. Mitochondrial evolution constitutes a rhizome, and it should be represented as such.
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Affiliation(s)
- Kalliopi Georgiades
- Unité de Recherche en Maladies Infectieuses Tropical Emergentes (URMITE) CNRS-IRD UMR 6236-198, Université de la Méditerranée, Faculté de Médecine La Timone, 27, Bd Jean Moulin, 13385, Marseille cedex 5, France
| | - Didier Raoult
- Unité de Recherche en Maladies Infectieuses Tropical Emergentes (URMITE) CNRS-IRD UMR 6236-198, Université de la Méditerranée, Faculté de Médecine La Timone, 27, Bd Jean Moulin, 13385, Marseille cedex 5, France
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Cameron SL, Yoshizawa K, Mizukoshi A, Whiting MF, Johnson KP. Mitochondrial genome deletions and minicircles are common in lice (Insecta: Phthiraptera). BMC Genomics 2011; 12:394. [PMID: 21813020 PMCID: PMC3199782 DOI: 10.1186/1471-2164-12-394] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Accepted: 08/04/2011] [Indexed: 01/16/2023] Open
Abstract
Background The gene composition, gene order and structure of the mitochondrial genome are remarkably stable across bilaterian animals. Lice (Insecta: Phthiraptera) are a major exception to this genomic stability in that the canonical single chromosome with 37 genes found in almost all other bilaterians has been lost in multiple lineages in favour of multiple, minicircular chromosomes with less than 37 genes on each chromosome. Results Minicircular mt genomes are found in six of the ten louse species examined to date and three types of minicircles were identified: heteroplasmic minicircles which coexist with full sized mt genomes (type 1); multigene chromosomes with short, simple control regions, we infer that the genome consists of several such chromosomes (type 2); and multiple, single to three gene chromosomes with large, complex control regions (type 3). Mapping minicircle types onto a phylogenetic tree of lice fails to show a pattern of their occurrence consistent with an evolutionary series of minicircle types. Analysis of the nuclear-encoded, mitochondrially-targetted genes inferred from the body louse, Pediculus, suggests that the loss of mitochondrial single-stranded binding protein (mtSSB) may be responsible for the presence of minicircles in at least species with the most derived type 3 minicircles (Pediculus, Damalinia). Conclusions Minicircular mt genomes are common in lice and appear to have arisen multiple times within the group. Life history adaptive explanations which attribute minicircular mt genomes in lice to the adoption of blood-feeding in the Anoplura are not supported by this expanded data set as minicircles are found in multiple non-blood feeding louse groups but are not found in the blood-feeding genus Heterodoxus. In contrast, a mechanist explanation based on the loss of mtSSB suggests that minicircles may be selectively favoured due to the incapacity of the mt replisome to synthesize long replicative products without mtSSB and thus the loss of this gene lead to the formation of minicircles in lice.
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Affiliation(s)
- Stephen L Cameron
- Discipline of Biogeosciences, Faculty of Science & Technology, Queensland University of Technology, Brisbane, QLD 4001, Australia.
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