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Pohuang T, Jittimanee S, Junnu S. Pathology and molecular characterization of Leucocytozoon caulleryi from backyard chickens in Khon Kaen Province, Thailand. Vet World 2021; 14:2634-2639. [PMID: 34903919 PMCID: PMC8654759 DOI: 10.14202/vetworld.2021.2634-2639] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 08/27/2021] [Indexed: 12/03/2022] Open
Abstract
Aim: The aim of this study was to characterize Leucocytozoon caulleryi from backyard chickens in Khon Kaen Province, Thailand. Materials and Methods: Tissue samples were collected from backyard chickens suspected to have leucocytozoonosis and subjected to histopathology examination. The BLAST Tool at NCBI GenBank (Basic Local Alignment Research Tools) (http://www.ncbi.nlm.nih.gov/BLAST) was used to identify the nucleotide sequence of the partial cytochrome c oxidase subunit I (cox I) gene. A Phylogenetic tree for analysis of L. caulleryi was constructed by using MEGA 7.0 software (https://www.megasoftware.net/). Results: The necropsy results revealed the subcutaneous hemorrhages of pectoral muscles, multifocal hemorrhages of the thymus and pectoral muscles, hemorrhage of the proventriculus and peritoneal cavity, and megaloschizonts of the pancreas and intestine, including subcapsular hemorrhages of the liver. Microscopic examination revealed numerous megaloschizonts of Leucocytozoon spp. in the pectoral muscles, intestine, pancreas, and thymus. Molecular analysis of the partial cox I gene showed that the causal agent was closely related to L. caulleryi reported in Japan. Conclusion: From these results, L. caulleryi was determined to be the causal agent of leucocytozoonosis and was closely associated with L. caulleryi reported in Japan.
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Affiliation(s)
- Tawatchai Pohuang
- Division of Livestock Medicine, Faculty of Veterinary Medicine, Khon Kaen University, Khon Kaen 40002, Thailand.,Research Group for Emerging and Re-emerging Infectious Diseases in Animals and Zoonotic Diseases, Faculty of Veterinary Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Suphattra Jittimanee
- Research Group for Emerging and Re-emerging Infectious Diseases in Animals and Zoonotic Diseases, Faculty of Veterinary Medicine, Khon Kaen University, Khon Kaen 40002, Thailand.,Division of Pathobiology, Faculty of Veterinary Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Sucheeva Junnu
- Division of Livestock Medicine, Faculty of Veterinary Medicine, Khon Kaen University, Khon Kaen 40002, Thailand.,Research Group for Emerging and Re-emerging Infectious Diseases in Animals and Zoonotic Diseases, Faculty of Veterinary Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
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2
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Galen SC, Borner J, Williamson JL, Witt CC, Perkins SL. Metatranscriptomics yields new genomic resources and sensitive detection of infections for diverse blood parasites. Mol Ecol Resour 2019; 20:14-28. [PMID: 31507097 DOI: 10.1111/1755-0998.13091] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Revised: 08/22/2019] [Accepted: 09/03/2019] [Indexed: 12/22/2022]
Abstract
Metatranscriptomics is a powerful method for studying the composition and function of complex microbial communities. The application of metatranscriptomics to multispecies parasite infections is of particular interest, as research on parasite evolution and diversification has been hampered by technical challenges to genome-scale DNA sequencing. In particular, blood parasites of vertebrates are abundant and diverse although they often occur at low infection intensities and exist as multispecies infections, rendering the isolation of genomic sequence data challenging. Here, we use birds and their diverse haemosporidian parasites to illustrate the potential for metatranscriptome sequencing to generate large quantities of genome-wide sequence data from multiple blood parasite species simultaneously. We used RNA-sequencing of 24 blood samples from songbirds in North America to show that metatranscriptomes can yield large proportions of haemosporidian protein-coding gene repertoires even when infections are of low intensity (<0.1% red blood cells infected) and consist of multiple parasite taxa. By bioinformatically separating host and parasite transcripts and assigning them to the haemosporidian genus of origin, we found that transcriptomes detected ~23% more total parasite infections across all samples than were identified using microscopy and DNA barcoding. For single-species infections, we obtained data for >1,300 loci from samples with as low as 0.03% parasitaemia, with the number of loci increasing with infection intensity. In total, we provide data for 1,502 single-copy orthologous loci from a phylogenetically diverse set of 33 haemosporidian mitochondrial lineages. The metatranscriptomic approach described here has the potential to accelerate ecological and evolutionary research on haemosporidians and other diverse parasites.
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Affiliation(s)
- Spencer C Galen
- Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, NY, USA.,Richard Gilder Graduate School, American Museum of Natural History, New York, NY, USA
| | - Janus Borner
- Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, NY, USA.,Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Ulm, Germany
| | - Jessie L Williamson
- Department of Biology, Museum of Southwestern Biology, University of New Mexico, Albuquerque, NM, USA
| | - Christopher C Witt
- Department of Biology, Museum of Southwestern Biology, University of New Mexico, Albuquerque, NM, USA
| | - Susan L Perkins
- Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, NY, USA
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3
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Lack of mitochondrial MutS homolog 1 in Toxoplasma gondii disrupts maintenance and fidelity of mitochondrial DNA and reveals metabolic plasticity. PLoS One 2017; 12:e0188040. [PMID: 29141004 PMCID: PMC5687708 DOI: 10.1371/journal.pone.0188040] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Accepted: 10/31/2017] [Indexed: 11/19/2022] Open
Abstract
The importance of maintaining the fidelity of the mitochondrial genome is underscored by the presence of various repair pathways within this organelle. Presumably, the repair of mitochondrial DNA would be of particular importance in organisms that possess only a single mitochondrion, like the human pathogens Plasmodium falciparum and Toxoplasma gondii. Understanding the machinery that maintains mitochondrial DNA in these parasites is of particular relevance, as mitochondrial function is a validated and effective target for anti-parasitic drugs. We previously determined that the Toxoplasma MutS homolog TgMSH1 localizes to the mitochondrion. MutS homologs are key components of the nuclear mismatch repair system in mammalian cells, and both yeast and plants possess MutS homologs that localize to the mitochondria where they regulate DNA stability. Here we show that the lack of TgMSH1 results in accumulation of single nucleotide variations in mitochondrial DNA and a reduction in mitochondrial DNA content. Additionally, parasites lacking TgMSH1 function can survive treatment with the cytochrome b inhibitor atovaquone. While the Tgmsh1 knockout strain has several missense mutations in cytochrome b, none affect amino acids known to be determinants of atovaquone sensitivity and atovaquone is still able to inhibit electron transport in the Tgmsh1 mutants. Furthermore, culture of Tgmsh1 mutant in the presence atovaquone leads to parasites with enhanced atovaquone resistance and complete shutdown of respiration. Thus, parasites lacking TgMSH1 overcome the disruption of mitochondrial DNA by adapting their physiology allowing them to forgo the need for oxidative phosphorylation. Consistent with this idea, the Tgmsh1 mutant is resistant to mitochondrial inhibitors with diverse targets and exhibits reduced ability to grow in the absence of glucose. This work shows TgMSH1 as critical for the maintenance and fidelity of the mitochondrial DNA in Toxoplasma, reveals a novel mechanism for atovaquone resistance, and exposes the physiological plasticity of this important human pathogen.
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4
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Schreeg ME, Marr HS, Griffith EH, Tarigo JL, Bird DM, Reichard MV, Cohn LA, Levy MG, Birkenheuer AJ. PCR amplification of a multi-copy mitochondrial gene (cox3) improves detection of Cytauxzoon felis infection as compared to a ribosomal gene (18S). Vet Parasitol 2016; 225:123-30. [PMID: 27369587 DOI: 10.1016/j.vetpar.2016.06.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Revised: 06/02/2016] [Accepted: 06/08/2016] [Indexed: 11/19/2022]
Abstract
Cytauxzoon felis is a tick-transmitted protozoan parasite that infects felids. Clinical disease caused by acute C. felis infection rapidly progresses in domestic cats, leading to high morbidity and mortality. Accurately diagnosing cytauxzoonosis as soon as possible during acute infection would allow for earlier initiation of antiprotozoal therapy which could lead to higher survival rates. Molecular detection of parasite rRNA genes (18S) by PCR has previously been shown to be a sensitive method of diagnosing C. felis infections. Based on evidence from related apicomplexan species, we hypothesized that C. felis mitochondrial genes would exist at higher copy numbers than 18S and would be a more sensitive diagnostic target. In this study we have designed a PCR assay targeting the C. felis mitochondrial gene cytochrome c oxidase subunit III (cox3). Herein we demonstrate that (1) the cox3 PCR can detect as low as 1 copy of DNA target and can detect C. felis in samples with known mitochondrial sequence heterogeneity, (2) cox3 copy number is increased relative to 18S in blood and tissue samples from acutely infected cats, and (3) the cox3 PCR is more sensitive than 18S PCR for detection of C. felis during early infections.
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Affiliation(s)
- Megan E Schreeg
- North Carolina State University, College of Veterinary Medicine, 1060 William Moore Dr., Raleigh, NC 27607, United States
| | - Henry S Marr
- North Carolina State University, College of Veterinary Medicine, 1060 William Moore Dr., Raleigh, NC 27607, United States
| | - Emily H Griffith
- North Carolina State University, College of Sciences, Campus Box 8201/4216, Broughton Hall, Raleigh, NC 27695, United States
| | - Jaime L Tarigo
- North Carolina State University, College of Veterinary Medicine, 1060 William Moore Dr., Raleigh, NC 27607, United States
| | - David M Bird
- North Carolina State University, College of Agriculture and Life Sciences, 317A Ricks Hall 1, Lampe Dr., Raleigh, NC 27695, United States
| | - Mason V Reichard
- Oklahoma State University, Center for Veterinary Health Sciences, 205 McElroy Hall, Stillwater, OK 74078, United States
| | - Leah A Cohn
- University of Missouri, College of Veterinary Medicine, 900 E. Campus Dr., Columbia, MO, 65211, United States
| | - Michael G Levy
- North Carolina State University, College of Veterinary Medicine, 1060 William Moore Dr., Raleigh, NC 27607, United States
| | - Adam J Birkenheuer
- North Carolina State University, College of Veterinary Medicine, 1060 William Moore Dr., Raleigh, NC 27607, United States.
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5
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Pattaradilokrat S, Tiyamanee W, Simpalipan P, Kaewthamasorn M, Saiwichai T, Li J, Harnyuttanakorn P. Molecular detection of the avian malaria parasite Plasmodium gallinaceum in Thailand. Vet Parasitol 2015; 210:1-9. [DOI: 10.1016/j.vetpar.2015.03.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Revised: 03/17/2015] [Accepted: 03/23/2015] [Indexed: 01/21/2023]
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Maier UG, Zauner S, Woehle C, Bolte K, Hempel F, Allen JF, Martin WF. Massively convergent evolution for ribosomal protein gene content in plastid and mitochondrial genomes. Genome Biol Evol 2014; 5:2318-29. [PMID: 24259312 PMCID: PMC3879969 DOI: 10.1093/gbe/evt181] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Plastid and mitochondrial genomes have undergone parallel evolution to encode the same functional set of genes. These encode conserved protein components of the electron transport chain in their respective bioenergetic membranes and genes for the ribosomes that express them. This highly convergent aspect of organelle genome evolution is partly explained by the redox regulation hypothesis, which predicts a separate plastid or mitochondrial location for genes encoding bioenergetic membrane proteins of either photosynthesis or respiration. Here we show that convergence in organelle genome evolution is far stronger than previously recognized, because the same set of genes for ribosomal proteins is independently retained by both plastid and mitochondrial genomes. A hitherto unrecognized selective pressure retains genes for the same ribosomal proteins in both organelles. On the Escherichia coli ribosome assembly map, the retained proteins are implicated in 30S and 50S ribosomal subunit assembly and initial rRNA binding. We suggest that ribosomal assembly imposes functional constraints that govern the retention of ribosomal protein coding genes in organelles. These constraints are subordinate to redox regulation for electron transport chain components, which anchor the ribosome to the organelle genome in the first place. As organelle genomes undergo reduction, the rRNAs also become smaller. Below size thresholds of approximately 1,300 nucleotides (16S rRNA) and 2,100 nucleotides (26S rRNA), all ribosomal protein coding genes are lost from organelles, while electron transport chain components remain organelle encoded as long as the organelles use redox chemistry to generate a proton motive force.
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Affiliation(s)
- Uwe-G Maier
- LOEWE Centre for Synthetic Microbiology (SYNMIKRO), Philipps-Universität, Marburg, Germany
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7
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Feagin JE, Harrell MI, Lee JC, Coe KJ, Sands BH, Cannone JJ, Tami G, Schnare MN, Gutell RR. The fragmented mitochondrial ribosomal RNAs of Plasmodium falciparum. PLoS One 2012; 7:e38320. [PMID: 22761677 PMCID: PMC3382252 DOI: 10.1371/journal.pone.0038320] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 05/03/2012] [Indexed: 11/18/2022] Open
Abstract
Background The mitochondrial genome in the human malaria parasite Plasmodium falciparum is most unusual. Over half the genome is composed of the genes for three classic mitochondrial proteins: cytochrome oxidase subunits I and III and apocytochrome b. The remainder encodes numerous small RNAs, ranging in size from 23 to 190 nt. Previous analysis revealed that some of these transcripts have significant sequence identity with highly conserved regions of large and small subunit rRNAs, and can form the expected secondary structures. However, these rRNA fragments are not encoded in linear order; instead, they are intermixed with one another and the protein coding genes, and are coded on both strands of the genome. This unorthodox arrangement hindered the identification of transcripts corresponding to other regions of rRNA that are highly conserved and/or are known to participate directly in protein synthesis. Principal Findings The identification of 14 additional small mitochondrial transcripts from P. falcipaurm and the assignment of 27 small RNAs (12 SSU RNAs totaling 804 nt, 15 LSU RNAs totaling 1233 nt) to specific regions of rRNA are supported by multiple lines of evidence. The regions now represented are highly similar to those of the small but contiguous mitochondrial rRNAs of Caenorhabditis elegans. The P. falciparum rRNA fragments cluster on the interfaces of the two ribosomal subunits in the three-dimensional structure of the ribosome. Significance All of the rRNA fragments are now presumed to have been identified with experimental methods, and nearly all of these have been mapped onto the SSU and LSU rRNAs. Conversely, all regions of the rRNAs that are known to be directly associated with protein synthesis have been identified in the P. falciparum mitochondrial genome and RNA transcripts. The fragmentation of the rRNA in the P. falciparum mitochondrion is the most extreme example of any rRNA fragmentation discovered.
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Affiliation(s)
- Jean E Feagin
- Seattle Biomedical Research Institute, Seattle, Washington, United States of America.
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8
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Perkins SL. Molecular systematics of the three mitochondrial protein-coding genes of malaria parasites: corroborative and new evidence for the origins of human malaria. ACTA ACUST UNITED AC 2009; 19:471-8. [PMID: 19489133 DOI: 10.1080/19401730802570926] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
BACKGROUND AND AIMS The mitochondrial genomes of malaria parasites (Plasmodium and related genera) are extremely small and contain just three protein-coding genes. These short linear genomes are tandemly repeated, allowing for amplification of the entire unit using a single pair of outwardly facing primers. MATERIALS AND METHODS Using this approach, I sequenced full mitochondrial genomes for seven new lineages of these parasites belonging to four genera and then, combining these new sequences with other published ones, I examined the phylogenetic utility of each of the three protein-coding genes, alone and when concatenated into a data-set of 3315 nucleotides. RESULTS Most relationships recovered are consistent with previous studies of the group. CONCLUSION Support for an Asian origin of Plasmodium vivax and a sister relationship of Plasmodium falciparum to the rodent malaria parasites was observed in this study. However, if a broad understanding of the evolutionary relationships of this group is to truly be understood, it is clear that loci outside the mitochondrial genome should be explored.
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Affiliation(s)
- Susan L Perkins
- Sackler Institute for Comparative Genomics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA.
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Oborník M, Janouškovec J, Chrudimský T, Lukeš J. Evolution of the apicoplast and its hosts: From heterotrophy to autotrophy and back again. Int J Parasitol 2009; 39:1-12. [DOI: 10.1016/j.ijpara.2008.07.010] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2008] [Revised: 07/23/2008] [Accepted: 07/25/2008] [Indexed: 10/21/2022]
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Sibley LD, Ajioka JW. Population structure of Toxoplasma gondii: clonal expansion driven by infrequent recombination and selective sweeps. Annu Rev Microbiol 2008; 62:329-51. [PMID: 18544039 DOI: 10.1146/annurev.micro.62.081307.162925] [Citation(s) in RCA: 183] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Toxoplasma gondii is among the most successful parasites. It is capable of infecting all warm-blooded animals and causing opportunistic disease in humans. T. gondii has a striking clonal population structure consisting of three predominant lineages in North America and Europe. Clonality is associated with the recent emergence of a monomorphic version of Chr1a, which drove a selective genetic sweep within the past 10,000 years. Strains from South America diverged from those in North America some 1-2 mya; recently, however, the monomorphic Chr1a has extended into regions of South America, where it is also associated with clonality. The recent spread of a few dominant lineages has dramatically shaped the population structure of T. gondii and has resulted in most lineages sharing a highly pathogenic nature. Understanding the factors that have shaped the population structure of T. gondii has implications for the emergence and transmission of human pathogens.
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Affiliation(s)
- L David Sibley
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, 63130, USA.
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Omori S, Sato Y, Hirakawa S, Isobe T, Yukawa M, Murata K. Two extra chromosomal genomes of Leucocytozoon caulleryi; complete nucleotide sequences of the mitochondrial genome and existence of the apicoplast genome. Parasitol Res 2008; 103:953-7. [PMID: 18581140 DOI: 10.1007/s00436-008-1083-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Accepted: 06/05/2008] [Indexed: 11/27/2022]
Abstract
We analyzed extra chromosomal genomes of avian blood protozoa, Leucocytozoon caulleryi. One of the genomes, the mitochondrial genome was completely sequenced resulting 5,959 bp in length. This genome contained the identical gene organization and contents to that of other avian blood protozoa previously analyzed: three functional genes for cytochrome c oxidase subunit I, III, and cytochrome b with following sets of discontinuous and scrambled 15 ribosomal subunit RNA genes. In addition, the mitochondrial genome was estimated to have the tandem repeated structure as well as previously found in avian Plasmodium species. Furthermore, we found partial gene sequences of apicoplast DNA, another extra chromosomal genome, from L. caulleryi. These sequences were estimated as partial caseinolytic protease C and elongation factor Tu A genes. This report is the first description of two extra chromosomal genomes of L. caulleryi.
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Affiliation(s)
- Sumie Omori
- Laboratory of Biomedical Science, Department of Veterinary Medicine, College of Bioresource Sciences, Nihon University, Fujisawa 252-8510, Japan
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Omori S, Sato Y, Isobe T, Yukawa M, Murata K. Complete nucleotide sequences of the mitochondrial genomes of two avian malaria protozoa, Plasmodium gallinaceum and Plasmodium juxtanucleare. Parasitol Res 2006; 100:661-4. [PMID: 17047998 DOI: 10.1007/s00436-006-0333-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2006] [Accepted: 09/01/2006] [Indexed: 11/25/2022]
Abstract
We analyzed mitochondrial genomes of two avian malaria protozoa, Plasmodium gallinaceum and Plasmodium juxtanucleare. Both mitochondrial genomes were estimated to be 6,002 and 6,014 bp in length, respectively, and to have the identical gene organization and contents to that of other Plasmodium species previously analyzed; three functional genes for cytochrome c oxidase subunit I, III, and cytochrome (cyt b), with following sets of discontinuous and scrambled 15 ribosomal subunit RNA (rRNA) genes. Similarities of the three protein-coding genes showed closer relationship within avian malaria protozoa rather than mammalian Plasmodium species. In addition, we showed the tandem repeated structure of each mitochondrial genome of both P. gallinaceum and P. juxtanucleare as well as previously found in mammalian Plasmodium species. This study revealed the complete sequences and structure of the mitochondrial genomes of avian malaria protozoa for the first time.
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Affiliation(s)
- Sumie Omori
- Laboratory of Biomedical Science, Department of Veterinary Medicine, College of Bioresource Sciences, Nihon University, Fujisawa, 252-8510, Japan
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Tian X, Zheng J, Hu S, Yu J. The rice mitochondrial genomes and their variations. PLANT PHYSIOLOGY 2006; 140:401-10. [PMID: 16384910 PMCID: PMC1361312 DOI: 10.1104/pp.105.070060] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Based on highly redundant and high-quality sequences, we assembled rice (Oryza sativa) mitochondrial genomes for two cultivars, 93-11 (an indica variety) and PA64S (an indica-like variety with maternal origin of japonica), which are paternal and maternal strains of an elite superhybrid rice Liang-You-Pei-Jiu (LYP-9), respectively. Following up with a previous analysis on rice chloroplast genomes, we divided mitochondrial sequence variations into two basic categories, intravarietal and intersubspecific. Intravarietal polymorphisms are variations within mitochondrial genomes of an individual variety. Intersubspecific polymorphisms are variations between subspecies among their major genotypes. In this study, we identified 96 single nucleotide polymorphisms (SNPs), 25 indels, and three segmental sequence variations as intersubspecific polymorphisms. A signature sequence fragment unique to indica varieties was confirmed experimentally and found in two wild rice samples, but absent in japonica varieties. The intersubspecific polymorphism rate for mitochondrial genomes is 0.02% for SNPs and 0.006% for indels, nearly 2.5 and 3 times lower than that of their chloroplast counterparts and 21 and 38 times lower than corresponding rates of the rice nuclear genome, respectively. The intravarietal polymorphism rates among analyzed mitochondrial genomes, such as 93-11 and PA64S, are 1.26% and 1.38% for SNPs and 1.13% and 1.09% for indels, respectively. Based on the total number of SNPs between the two mitochondrial genomes, we estimate that the divergence of indica and japonica mitochondrial genomes occurred approximately 45,000 to 250,000 years ago.
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Affiliation(s)
- Xiangjun Tian
- James D. Watson Institute of Genome Sciences, Zhejiang University and Hangzhou Genomics Institute, Zhejiang Provincial Key Laboratory of Genomic Bioinformatics, Hangzhou 310008, China
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Musset L, Pradines B, Parzy D, Durand R, Bigot P, Le Bras J. Apparent absence of atovaquone/proguanil resistance in 477 Plasmodium falciparum isolates from untreated French travellers. J Antimicrob Chemother 2005; 57:110-5. [PMID: 16319183 DOI: 10.1093/jac/dki420] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES We examined the atovaquone in vitro susceptibility and the cytochrome b (cytb) gene polymorphism of African Plasmodium falciparum isolates during the first years of atovaquone/proguanil use. PATIENTS AND METHODS Between 1999 and 2004, we collected blood samples from French P. falciparum-infected patients returning from African countries. Atovaquone susceptibility was determined using an in vitro isotopic test and cytb genotyping was performed by restriction fragment length polymorphism analysis and sequencing. These results were analysed according to the clinical response to atovaquone/proguanil treatment. RESULTS No in vitro atovaquone resistance (IC50 > 1900 nM) and no cytb mutation leading to the Y268S substitution were detected among 477 unexposed African P. falciparum isolates. Eight cytb polymorphisms were found outside the ubiquinone reduction site by sequencing the entire gene of 270 isolates. One atovaquone/proguanil treatment failure was documented; the post-treatment isolate had an atovaquone susceptibility of 8230 nM and the Ser268 Cytb change; the pre-treatment isolate, obtained 4 weeks previously, was Cytb Tyr268 (wild-type). CONCLUSIONS No atovaquone/proguanil resistance was detected by phenotyping or genotyping among 477 unexposed African P. falciparum isolates. Atovaquone/proguanil-resistant parasite was detectable only in the post-treatment isolate from a treatment failure.
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Affiliation(s)
- Lise Musset
- Centre National de Référence pour la Chimiosensibilité du Paludisme, APHP, Hôpital Bichat-Claude Bernard, Paris, France
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Williamson DH, Preiser PR, Wilson RJ. Organelle DNAs: The bit players in malaria parasite DNA replication. ACTA ACUST UNITED AC 2005; 12:357-62. [PMID: 15275174 DOI: 10.1016/0169-4758(96)10053-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The replication mechanics of the extrachromosomal DNAs of the malaria parasite are beginning to be anravelled. At 6 kb, the mitochondrial genome is the smallest known and, unlike higher eukaryotes, its multiple copies per cell occur as polydisperse linear concatemers. Here, Don Williamson, Peter Preiser and Iain Wilson discuss recent evidence that this DNA replicates by a process akin to those of certain bacteriophages, which make use of extensive recombination coupled with rolling circles. The parasite's second extrachromosomal DNA, a 35 kb circular molecule thought to be a plastid remnant inherited from a remote photoautotroph, probably replicates in a more familiar fashion from conventional origins or D loops. Improved understanding of both organelle's replicative mechanisms could give new leads to malaria chemotherapy.
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Affiliation(s)
- D H Williamson
- Parasitology Division, National Institute for Medical Research, Mill Hill, London, UK.
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Abstract
Mitochondria of the malaria parasitePlasmodium falciparumare morphologically different between the asexual and sexual blood stages (gametocytes). In this paper recent findings of mitochondrial heterogeneity are reviewed based on their ultrastructural characteristics, metabolic activities and the differential expression of their genes in these 2 blood stages of the parasite. The existence of NADH dehydrogenase (complex I), succinate dehydrogenase (complex II), cytochrome c reductase (complex III) and cytochrome c oxidase (complex IV) suggests that the biochemically active electron transport system operates in this parasite. There is also an alternative electron transport branch pathway, including an anaerobic function of complex II. One of the functional roles of the mitochondrion in the parasite is the coordination of pyrimidine biosynthesis, the electron transport system and oxygen utilization via dihydroorotate dehydrogenase and coenzyme Q. Complete sets of genes encoding enzymes of the tricarboxylic acid cycle and the ATP synthase complex are predicted fromP. falciparumgenomics information. Other metabolic roles of this organelle include membrane potential maintenance, haem and coenzyme Q biosynthesis, and oxidative phosphorylation. Furthermore, the mitochondrion may be a chemotherapeutic target for antimalarial drug development. The antimalarial drug atovaquone targets the mitochondrion.
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Affiliation(s)
- J Krungkrai
- Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand.
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17
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Williamson DH, Denny PW, Moore PW, Sato S, McCready S, Wilson RJ. The in vivo conformation of the plastid DNA of Toxoplasma gondii: implications for replication. J Mol Biol 2001; 306:159-68. [PMID: 11237591 DOI: 10.1006/jmbi.2000.4385] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Phylum Apicomplexa comprises thousands of obligate intracellular parasites, some of which cause serious disease in man and other animals. Though not photosynthetic, some of them, including the malaria parasites (Plasmodium spp.) and the causative organism of Toxoplasmosis, Toxoplasma gondii, possess a remnant plastid partially determined by a highly derived residual genome encoded in 35 kb DNA. The genetic maps of the plastid genomes of these two organisms are extremely similar in nucleotide sequence, gene function and gene order. However, a study using pulsed field gel electrophoresis and electron microscopy has shown that in contrast to the malarial version, only a minority of the plastid DNA of Toxoplasma occurs as circular 35 kb molecules. The majority consists of a precise oligomeric series of linear tandem arrays of the genome, each oligomer terminating at the same site in the genetic map, i.e. in the centre of a large inverted repeat (IR) which encodes duplicated tRNA and rRNA genes. This overall topology strongly suggests that replication occurs by a rolling circle mechanism initiating at the centre of the IR, which is also the site at which the linear tails of the rolling circles are processed to yield the oligomers. A model is proposed which accounts for the quantitative structure of the molecular population. It is relevant that a somewhat similar structure has been reported for at least three land plant chloroplast genomes.
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MESH Headings
- Animals
- DNA Replication
- DNA Restriction Enzymes/metabolism
- DNA, Circular/biosynthesis
- DNA, Circular/chemistry
- DNA, Circular/genetics
- DNA, Circular/ultrastructure
- DNA, Protozoan/biosynthesis
- DNA, Protozoan/chemistry
- DNA, Protozoan/genetics
- DNA, Protozoan/ultrastructure
- Electrophoresis, Gel, Pulsed-Field
- Gamma Rays
- Microscopy, Electron
- Models, Genetic
- Nucleic Acid Conformation
- Plastids/genetics
- Toxoplasma/genetics
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Affiliation(s)
- D H Williamson
- National Institute for Medical Research, Mill Hill, London, NW7 1AA, UK.
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18
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Abstract
An extrachromosomal genome of between 27 and 35 kb has been described in several apicomplexan parasites including Plasmodium falciparum and Toxoplasma gondii. Examination of sequence data proved the genomes to be a remnant plastid genome, from which all genes encoding photosynthetic functions had been lost. Localisation studies had shown that the genome was located within a multi-walled organelle, anterior to the nucleus. This organelle had been previously described in ultrastructural studies of several genera of apicomplexa, but no function had been attributed to it. This invited review describes the evolution of knowledge on the apicomplexan plastid, then discusses current research findings on the likely role of the plastid in the Apicomplexa. How the plastid may be used to effect better drug treatments for apicomplexan diseases, and its potential as a marker for investigating phylogenetic relationships among the Apicomplexa, are discussed.
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Affiliation(s)
- M T Gleeson
- Department of Cell and Molecular Biology, Faculty of Science, University of Technology, Westbourne Street, Gore Hill NSW 2065, Sydney, Australia.
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19
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Abstract
Mitochondrial genomes have been sequenced from a wide variety of organisms, including an increasing number of parasites. They maintain some characteristics in common across the spectrum of life-a common core of genes related to mitochondrial respiration being most prominent-but have also developed a great diversity of gene content, organisation, and expression machineries. The characteristics of mitochondrial genomes vary widely among the different groups of protozoan parasites, from the minute genomes of the apicomplexans to amoebae with 20 times as many genes. Kinetoplastid protozoa have a similar number of genes to metazoans, but the details of gene organisation and expression in kinetoplastids require extraordinary mechanisms. Mitochondrial genes in nematodes and trematodes appear quite sedate in comparison, but a closer look shows a strong tendency to unusual tRNA structure and alternative initiation codons among these groups. Mitochondrial genes are increasingly coming into play as aids to phylogenetic and epidemiologic analyses, and mitochondrial functions are being recognised as potential drug targets. In addition, examination of mitochondrial genomes is producing further insights into the diversity of the wide-ranging group of organisms comprising the general category of parasites.
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Affiliation(s)
- J E Feagin
- Seattle Biomedical Research Institute, 4 Nickerson St., Seattle, WA 98109-1651, USA.
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20
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Learngaramkul P, Petmitr S, Krungkrai SR, Prapunwattana P, Krungkrai J. Molecular characterization of mitochondria in asexual and sexual blood stages of Plasmodium falciparum. MOLECULAR CELL BIOLOGY RESEARCH COMMUNICATIONS : MCBRC 1999; 2:15-20. [PMID: 10527885 DOI: 10.1006/mcbr.1999.0145] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Molecular mechanisms that regulate gene expression during development of asexual stage to sexual stage of Plasmodium falciparum in the human erythrocyte are largely unknown. There were apparent variations in ultrastructural characteristics of the mitochondrion between the two developing stages. The asexual stage's mitochondrion had developed less than that of the sexual stage. The respiratory complexes of the mitochondrial electron transport system in the asexual stage were approximately 8-10 times less active than those in the sexual stage. Using quantitative polymerase chain reaction to amplify the cytochrome b gene encoding a subunit of mitochondrial cytochrome c reductase, the amount of the cytochrome b gene of the sexual stage was calculated to be approximately 3 times higher than that obtained from the asexual stage. Moreover, using quantitative reverse-transcription polymerase chain reaction, a relatively high level of approximately 1.3-kb transcript mRNA of the cytochrome b gene was observed in the sexual stage compared to the asexual stage. A known single-copy chromosomal dihydrofolate reductase gene was found to have a similar amount in the two stages. These results suggest that the copy number of the mitochondrial gene, including transcriptional and translational mechanisms, plays a major regulatory role in differential expression during the development of the asexual to sexual stage of P. falciparum in the human cell.
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Affiliation(s)
- P Learngaramkul
- Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
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21
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Gillespie DE, Salazar NA, Rehkopf DH, Feagin JE. The fragmented mitochondrial ribosomal RNAs of Plasmodium falciparum have short A tails. Nucleic Acids Res 1999; 27:2416-22. [PMID: 10325433 PMCID: PMC148810 DOI: 10.1093/nar/27.11.2416] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The mitochondrial genome of Plasmodium falciparum encodes highly fragmented rRNAs. Twenty small RNAs which are putative rRNA fragments have been found and 15 of them have been identified as corresponding to specific regions of rRNA sequence. To investigate the possible interactions between the fragmented rRNAs in the ribosome, we have mapped the ends of many of the small transcripts using primer extension and RNase protection analysis. Results obtained from these studies revealed that some of the rRNA transcripts were longer than the sequences which encode them. To investigate these size discrepancies, we performed 3' RACE PCR analysis and RNase H mapping. These analyses revealed non-encoded oligo(A) tails on some but not all of these small rRNAs. The approximate length of the oligo(A) tail appears to be transcript-specific, with some rRNAs consistently showing longer oligo(A) tails than others. The oligoadenylation of the rRNAs may provide a buffer zone against 3' exonucleolytic attack, thereby preserving the encoded sequences necessary for secondary structure interactions in the ribosome.
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Affiliation(s)
- D E Gillespie
- Seattle Biomedical Research Institute, 4 Nickerson Street, Seattle, WA 98109-1651, USA
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22
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Preiser PR, Wilson RJ, Moore PW, McCready S, Hajibagheri MA, Blight KJ, Strath M, Williamson DH. Recombination associated with replication of malarial mitochondrial DNA. EMBO J 1996; 15:684-93. [PMID: 8599952 PMCID: PMC449987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Mitochondrial DNA of the malarial parasite Plasmodium falciparum comprises approximately 20 copies per cell of a 6 kb genome, arranged mainly as polydisperse linear concatemers. In synchronous blood cultures, initiation of mtDNA replication coincides with the start of the 4-5 doublings in nuclear DNA that mark the reproductive phase of the erythrocytic cycle. We show that mtDNA replication coincides with a recombination process reminiscent of the replication mechanism used by certain bacteriophages and plasmids. The few circular forms of mtDNA which are also present do not replicate by a theta mechanism, but are themselves the product of recombination, and we propose they undergo rolling circle activity to generate the linear concatemers.
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MESH Headings
- Animals
- DNA Replication
- DNA, Circular/biosynthesis
- DNA, Circular/genetics
- DNA, Circular/isolation & purification
- DNA, Mitochondrial/biosynthesis
- DNA, Mitochondrial/genetics
- DNA, Mitochondrial/isolation & purification
- DNA, Protozoan/biosynthesis
- DNA, Protozoan/genetics
- DNA, Protozoan/isolation & purification
- Electrophoresis, Gel, Two-Dimensional
- Kinetics
- Microscopy, Electron
- Multigene Family
- Plasmodium falciparum/genetics
- Plasmodium falciparum/growth & development
- Plasmodium falciparum/metabolism
- Recombination, Genetic
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Affiliation(s)
- P R Preiser
- The National Institute for Medical Research, London, UK
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23
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Affiliation(s)
- Shuja ALI
- Present address: Animal Science Institute, National Agricultural Research Center, P.O. NARC, Islamabad 45500, Pakistan
| | - Chihiro SUGIMOTO
- Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060, Japan
| | - Misao ONUMA
- Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060, Japan
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24
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Egea N, Lang-Unnasch N. Phylogeny of the large extrachromosomal DNA of organisms in the phylum Apicomplexa. J Eukaryot Microbiol 1995; 42:679-84. [PMID: 8520581 DOI: 10.1111/j.1550-7408.1995.tb01615.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Organisms in the phylum Apicomplexa appear to have a large extrachromosomal DNA which is unrelated to the mitochondrial DNA. Based on the apparent gene content of the large (35 kb) extrachromosomal DNA of Plasmodium falciparum, it has been suggested that it is a plastid-like DNA, which may be related to the plastid DNA of rhodophytes. However, phylogenetic analyses have been inconclusive. It has been suggested that this is due to the unusually high A+T content of the Plasmodium falciparum large extrachromosomal DNA. To further investigate the evolution of the apicomplexan large extrachromosomal DNA, the DNA sequence of the organellar ribosomal RNA gene from Toxoplasma gondii, was determined. The Toxoplasma gondii rDNA sequence was most similar to the large extrachromosomal rDNA of Plasmodium falciparum, but was much less A+T rich. Phylogenetic analyses were carried out using the LogDet transformation to minimize the impact of nucleotide bias. These studies support the evolutionary relatedness of the Toxoplasma gondii rDNA with the large extrachromosomal rDNA of Plasmodium falciparum and with the organellar rDNA of another parasite in the phylum Apicomplexa, Babesia bovis. These analyses also suggest that the apicomplexan large extrachromosomal DNA may be more closely related to the plastid DNA of euglenoids than those of rhodophytes.
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Affiliation(s)
- N Egea
- Department of Medicine, University of Alabama at Birmingham 35294-2170, USA
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25
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Gozar MM, Bagnara AS. An organelle-like small subunit ribosomal RNA gene from Babesia bovis: nucleotide sequence, secondary structure of the transcript and preliminary phylogenetic analysis. Int J Parasitol 1995; 25:929-38. [PMID: 8550293 DOI: 10.1016/0020-7519(95)00022-t] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Investigations aimed at identifying the mitochondrial genome of Babesia bovis using the polymerase chain reaction (PCR) have established the existence of an organelle-like small subunit ribosomal RNA (SSU rRNA) gene in the parasite. The sequence, compiled from three main PCR products, was 1448 bp in length (including the primer regions), had a 73% A+T content and showed significant similarity (68% sequence identity) to the "organellar" SSU rRNA gene from Plasmodium falciparum. The proposed secondary structure of the transcript showed several features which were consistent with a eubacterial origin for the organelle-like gene. The presence of putative binding sites for streptomycin and tetracycline also supported an "organellar" location for the gene and suggested that the SSU rRNA transcript is functional in protein synthesis because tetracycline has anti-babesial activity. Phylogenetic analyses based on the conserved regions of the SSU-like rRNA genes from a wide variety of organisms showed only a weak association of the babesial sequence with its mitochondrial homologues and an even weaker association with the corresponding genes of plastid origin. The origin of this organelle-like gene in B. bovis therefore remains unresolved, as is the case for its homologue from P. falciparum.
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Affiliation(s)
- M M Gozar
- School of Biochemistry and Molecular Genetics, University of New South Wales, Sydney, Australia
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26
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Hotzel I, Kabakoff R, Ozaki LS. Small extrachromosomal nucleic acid segments in protozoan parasites. Vet Parasitol 1995; 57:57-60. [PMID: 7597793 DOI: 10.1016/0304-4017(94)03110-i] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Viruses have been described in the following protozoa: Babesia spp., Trichomonas vaginalis, Giardia lamblia, Leishmania braziliensis and Eimeria spp. In order to study the Babesia bovis virus, merozoites have been prepared from the blood of infected cattle. Agarose gel electrophoresis of nucleic extracts from the bovine protozoa B. bovis and Babesia bigemina were separated into genomic DNA and at least two additional nucleic acids. One molecule with a relative mobility of 5.5 kilobase pairs (kbp) was identified as a double-stranded RNA virus-like particle. Another 6.2 kbp DNA molecule had sequences related to mitochondrial genome.
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Affiliation(s)
- I Hotzel
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
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27
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[1] Forward and reverse genetics in the study of the obligate, intracellular parasite Toxoplasma gondii. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s1067-2389(06)80004-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
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28
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Feagin JE. The 6-kb element of Plasmodium falciparum encodes mitochondrial cytochrome genes. Mol Biochem Parasitol 1992; 52:145-8. [PMID: 1320735 DOI: 10.1016/0166-6851(92)90046-m] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- J E Feagin
- Seattle Biomedical Research Institute, WA 98109-1651
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29
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Wilson RJ, Fry M, Gardner MJ, Feagin JE, Williamson DH. Subcellular fractionation of the two organelle DNAs of malaria parasites. Curr Genet 1992; 21:405-8. [PMID: 1525866 DOI: 10.1007/bf00351702] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Malaria parasites contain two extrachromosomal DNAs, a 6 kb repetitive linear molecule which is assigned on the basis of its genetic content to the mitochondria, and a 35 kb transcriptionally active circular molecule whose intracellular location is not known. We used the polymerase chain reaction to detect and estimate the numbers of both molecules in sub-cellular fractions derived from the rodent parasite Plasmodium yoelii. The two DNA molecules were not coordinately partitioned by the fractionation process, the 6 kb molecule being more abundant, relative to the 35 kb circle, in a fraction enriched for mitochondria, the converse being true for a less dense fraction of unknown identity. This implies that the two molecules are located in different cellular compartments, and is consistent with other evidence suggesting they have different evolutionary origins.
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Affiliation(s)
- R J Wilson
- Parasitology Division, National Institute for Medical Research, Mill Hill, London, UK
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30
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Schelp C, Böse R, Friedhoff KT. Demonstration of extrachromosomal DNA from Babesia equi merozoites. Parasitol Res 1992; 78:707-8. [PMID: 1480611 DOI: 10.1007/bf00931526] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
An extrachromosomal nucleic acid element was detected in high-molecular-weight DNA preparations form Babesia equi merozoites. This extrachromosomal element was shown to be DNA rather than RNA and had an apparent fragment size of about 9 kilobase-pairs (kb). Hybridization experiments using purified 9-kb DNA as a probe revealed sequence homologies with extrachromosomal DNA from two other Babesia species.
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Affiliation(s)
- C Schelp
- Institute of Parasitology, Hannover School of Veterinary Medicine, Federal Republic of Germany
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31
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Ossorio PN, Sibley LD, Boothroyd JC. Mitochondrial-like DNA sequences flanked by direct and inverted repeats in the nuclear genome of Toxoplasma gondii. J Mol Biol 1991; 222:525-36. [PMID: 1660924 DOI: 10.1016/0022-2836(91)90494-q] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In the course of our genetic studies on Toxoplasma gondii, it was discovered that one cosmid hybridized to a repetitive element. The hybridization pattern observed for the enzyme BglII indicated that this cosmid hybridized to a large number of discrete, but related elements. Four BglII fragments were subcloned from the cosmid, and each was shown to hybridize with all the others, as well as to numerous dispersed sequences in genomic DNA. Three subclones were sequenced in their entirety, and shown to contain fragments of the genes for cytochrome oxidase subunit I and apocytochrome b, complete and functional copies of which have been found in only mitochondrial genomes. All the subcloned fragments were bounded at both ends by a 91 base-pair sequence, which contains a site for BglII. This 91 base-pair sequence could be found as either a direct or inverted repeat. It was determined that the BglII elements are arrayed downstream from a single copy nuclear gene. Comparison of genomic and cosmid DNAs confirmed that the cosmid faithfully reflects the nuclear genome. Although the mitochondrial genome of Toxoplasma has not been characterized, these nuclear mitochondrial-like sequences appear to be internally rearranged with respect to known, functional mitochondrial genomes, and with respect to each other. The finding of short repeated sequences flanking these elements may be a clue to the mechanism of their dissemination.
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Affiliation(s)
- P N Ossorio
- Department of Microbiology and Immunology, Stanford University School of Medicine, CA 94305-5402
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32
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Gardner MJ, Feagin JE, Moore DJ, Spencer DF, Gray MW, Williamson DH, Wilson RJ. Organisation and expression of small subunit ribosomal RNA genes encoded by a 35-kilobase circular DNA in Plasmodium falciparum. Mol Biochem Parasitol 1991; 48:77-88. [PMID: 1779991 DOI: 10.1016/0166-6851(91)90166-4] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A restriction map of the 35-kb circular DNA molecule of Plasmodium falciparum showed that a region of about 6 kb, encoding both a large and a small subunit ribosomal RNA gene, has been duplicated in inverted orientation. The complete sequence of one small subunit rRNA gene is presented as well as an analysis of transcripts from erythrocytic stage parasites. Comparative sequence analysis of the rRNA gene and the proposed secondary structure of the rRNA suggest that it is of organellar origin. Intriguingly, while some characteristics of the small subunit rRNA gene are similar to mitochondrial sequences, others are more like those of plastids. The origin of the circular DNA molecule and evolutionary implications of its genetic content are discussed.
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Affiliation(s)
- M J Gardner
- Division of Parasitology, National Institute for Medical Research, Mill Hill, London, U.K
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33
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Feagin JE, Gardner MJ, Williamson DH, Wilson RJ. The putative mitochondrial genome of Plasmodium falciparum. THE JOURNAL OF PROTOZOOLOGY 1991; 38:243-5. [PMID: 1880762 DOI: 10.1111/j.1550-7408.1991.tb04436.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Intraerythrocytic stages of mammalian malarial parasites employ glycolysis for energy production but some aspects of mitochondrial function appear crucial to their survival since inhibitors of mitochondrial protein synthesis and electron transport have antimalarial effects. Investigations of the putative mitochondrial genome of Plasmodium falciparum have detected organellar rRNAs and tRNAs encoded by a 35 kb circular DNA. Some features of the organization and sequence of the rRNA genes are reminiscent of chloroplast DNAs. The 35 kb DNA also encodes open reading frames for proteins normally found in chloroplast but not mitochondrial genomes. An apparently unrelated 6 kb tandemly repeated element which encodes two mitochondrial protein coding genes and fragments of rRNA genes is also found in malarial parasites. The malarial mitochondrial genome thus appears quite unusual. Further investigations are expected to provide insights into the possible functional relationships between these molecules and perhaps their evolutionary history.
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Affiliation(s)
- J E Feagin
- Seattle Biomedical Research Institute, Washington 98109-1651
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34
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Abstract
During the past few years the characterization of several Plasmodium falciparum RNA polymerase subunits has revealed potentially significant differences between the corresponding subunits of the host and parasite enzymes(1-3). The largest subunits of P. falciparum RNA polymerase II and III contain enlarged variable domains that separate conserved domains in these subunits. The partially characterized beta and beta '-like subunits of an organellar P. falciparum RNA polymerase also appear to be distinct from the host RNA polymerases. In this review David Bzik discusses the structure and role of RNA polymerases in Plasmodium.
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Affiliation(s)
- D J Bzik
- Department of Microbiology, Dartmouth Medical School, Hanover, NH 03756, USA
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