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Valach M, Moreira S, Petitjean C, Benz C, Butenko A, Flegontova O, Nenarokova A, Prokopchuk G, Batstone T, Lapébie P, Lemogo L, Sarrasin M, Stretenowich P, Tripathi P, Yazaki E, Nara T, Henrissat B, Lang BF, Gray MW, Williams TA, Lukeš J, Burger G. Recent expansion of metabolic versatility in Diplonema papillatum, the model species of a highly speciose group of marine eukaryotes. BMC Biol 2023; 21:99. [PMID: 37143068 PMCID: PMC10161547 DOI: 10.1186/s12915-023-01563-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 03/10/2023] [Indexed: 05/06/2023] Open
Abstract
BACKGROUND Diplonemid flagellates are among the most abundant and species-rich of known marine microeukaryotes, colonizing all habitats, depths, and geographic regions of the world ocean. However, little is known about their genomes, biology, and ecological role. RESULTS We present the first nuclear genome sequence from a diplonemid, the type species Diplonema papillatum. The ~ 280-Mb genome assembly contains about 32,000 protein-coding genes, likely co-transcribed in groups of up to 100. Gene clusters are separated by long repetitive regions that include numerous transposable elements, which also reside within introns. Analysis of gene-family evolution reveals that the last common diplonemid ancestor underwent considerable metabolic expansion. D. papillatum-specific gains of carbohydrate-degradation capability were apparently acquired via horizontal gene transfer. The predicted breakdown of polysaccharides including pectin and xylan is at odds with reports of peptides being the predominant carbon source of this organism. Secretome analysis together with feeding experiments suggest that D. papillatum is predatory, able to degrade cell walls of live microeukaryotes, macroalgae, and water plants, not only for protoplast feeding but also for metabolizing cell-wall carbohydrates as an energy source. The analysis of environmental barcode samples shows that D. papillatum is confined to temperate coastal waters, presumably acting in bioremediation of eutrophication. CONCLUSIONS Nuclear genome information will allow systematic functional and cell-biology studies in D. papillatum. It will also serve as a reference for the highly diverse diplonemids and provide a point of comparison for studying gene complement evolution in the sister group of Kinetoplastida, including human-pathogenic taxa.
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Affiliation(s)
- Matus Valach
- Department of Biochemistry, Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, QC, Canada.
| | - Sandrine Moreira
- Department of Biochemistry, Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, QC, Canada
| | - Celine Petitjean
- School of Biological Sciences, University of Bristol, Bristol, UK
| | - Corinna Benz
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic
| | - Anzhelika Butenko
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
- Faculty of Science, University of Ostrava, Ostrava, Czech Republic
| | - Olga Flegontova
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic
- Faculty of Science, University of Ostrava, Ostrava, Czech Republic
| | - Anna Nenarokova
- School of Biological Sciences, University of Bristol, Bristol, UK
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic
| | - Galina Prokopchuk
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Tom Batstone
- School of Biological Sciences, University of Bristol, Bristol, UK
- Present address: High Performance Computing Centre, Bristol, UK
| | - Pascal Lapébie
- Architecture et Fonction des Macromolécules Biologiques (AFMB), CNRS, Aix Marseille Université, Marseille, France
| | - Lionnel Lemogo
- Department of Biochemistry, Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, QC, Canada
- Present address: Environment Climate Change Canada, Dorval, QC, Canada
| | - Matt Sarrasin
- Department of Biochemistry, Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, QC, Canada
| | - Paul Stretenowich
- Department of Biochemistry, Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, QC, Canada
- Present address: Canadian Centre for Computational Genomics; McGill Genome Centre, McGill University, Montreal, QC, Canada
| | - Pragya Tripathi
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Euki Yazaki
- RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS), Hirosawa, Wako, Saitama, Japan
| | - Takeshi Nara
- Laboratory of Molecular Parasitology, Graduate School of Life Science and Technology, Iryo Sosei University, Iwaki City, Fukushima, Japan
| | - Bernard Henrissat
- Architecture et Fonction des Macromolécules Biologiques (AFMB), CNRS, Aix Marseille Université, Marseille, France
- Present address: DTU Bioengineering, Technical University of Denmark, Lyngby, Denmark
- Department of Biological Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
| | - B Franz Lang
- Department of Biochemistry, Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, QC, Canada
| | - Michael W Gray
- Department of Biochemistry and Molecular Biology, Institute for Comparative Genomics, Dalhousie University, Halifax, NS, Canada
| | - Tom A Williams
- School of Biological Sciences, University of Bristol, Bristol, UK
| | - Julius Lukeš
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Gertraud Burger
- Department of Biochemistry, Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, QC, Canada.
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2
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Guerra-Slompo E, Cesaro G, Guimarães B, Zanchin N. Dissecting Trypanosoma brucei RRP44 function in the maturation of segmented ribosomal RNA using a regulated genetic complementation system. Nucleic Acids Res 2023; 51:396-419. [PMID: 36610751 PMCID: PMC9841430 DOI: 10.1093/nar/gkac1217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 11/29/2022] [Accepted: 01/03/2023] [Indexed: 01/09/2023] Open
Abstract
Trypanosoma brucei belongs to a group of protozoans presenting fragmented large subunit rRNA. Its LSU rRNA equivalent to the 25S/28S rRNA of other eukaryotes is split into six fragments, requiring additional processing for removal of the extra spacer sequences. We have used a genetic complementation strategy to further investigate the T. brucei RRP44 nuclease in pre-rRNA maturation. TbRRP44 contains both a PIN and a RNB domain whose homologues are found in association with the exosome complex. We found that the exonucleolytic activity of the RNB domain as well as the physical presence of the PIN domain are essential for TbRRP44 function, while a catalytic site mutation in the PIN domain has no detectable effect on cell growth. A new endonucleolytic cleavage site in ITS1 was identified. In addition to the 5.8S rRNA 3'-end maturation, TbRRP44 is required for degradation of the excised 5'-ETS and for removal of part of ITS1 during maturation of the 18S rRNA 3'-end. TbRRP44 deficiency leads to accumulation of many LSU intermediate precursors, most of them not detected in control cells. TbRRP44 is also required for U3 snoRNA and spliced leader processing, indicating that TbRRP44 may have a wide role in RNA processing in T. brucei.
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Affiliation(s)
- Eloise Pavão Guerra-Slompo
- Carlos Chagas Institute, Oswaldo Cruz Foundation, FIOCRUZ, R. Prof. Algacyr Munhoz Mader 3775, 81350-010, Curitiba-PR, Brazil
| | - Giovanna Cesaro
- Carlos Chagas Institute, Oswaldo Cruz Foundation, FIOCRUZ, R. Prof. Algacyr Munhoz Mader 3775, 81350-010, Curitiba-PR, Brazil,Biochemistry Postgraduate Program, Federal University of Paraná, Curitiba-PR, Brazil
| | - Beatriz Gomes Guimarães
- Carlos Chagas Institute, Oswaldo Cruz Foundation, FIOCRUZ, R. Prof. Algacyr Munhoz Mader 3775, 81350-010, Curitiba-PR, Brazil,Biochemistry Postgraduate Program, Federal University of Paraná, Curitiba-PR, Brazil
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3
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Tashyreva D, Simpson A, Prokopchuk G, Škodová-Sveráková I, Butenko A, Hammond M, George EE, Flegontova O, Záhonová K, Faktorová D, Yabuki A, Horák A, Keeling PJ, Lukeš J. Diplonemids – A Review on “New“ Flagellates on the Oceanic Block. Protist 2022; 173:125868. [DOI: 10.1016/j.protis.2022.125868] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 02/26/2022] [Accepted: 02/28/2022] [Indexed: 11/15/2022]
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4
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Tikhonenkov DV, Gawryluk RMR, Mylnikov AP, Keeling PJ. First finding of free-living representatives of Prokinetoplastina and their nuclear and mitochondrial genomes. Sci Rep 2021; 11:2946. [PMID: 33536456 PMCID: PMC7859406 DOI: 10.1038/s41598-021-82369-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 01/19/2021] [Indexed: 01/30/2023] Open
Abstract
Kinetoplastids are heterotrophic flagellated protists, including important parasites of humans and animals (trypanosomatids), and ecologically important free-living bacterial consumers (bodonids). Phylogenies have shown that the earliest-branching kinetoplastids are all parasites or obligate endosymbionts, whose highly-derived state makes reconstructing the ancestral state of the group challenging. We have isolated new strains of unusual free-living flagellates that molecular phylogeny shows to be most closely related to endosymbiotic and parasitic Perkinsela and Ichthyobodo species that, together with unidentified environmental sequences, form the clade at the base of kinetoplastids. These strains are therefore the first described free-living prokinetoplastids, and potentially very informative in understanding the evolution and ancestral states of morphological and molecular characteristics described in other kinetoplastids. Overall, we find that these organisms morphologically and ultrastructurally resemble some free-living bodonids and diplonemids, and possess nuclear genomes with few introns, polycistronic mRNA expression, high coding density, and derived traits shared with other kinetoplastids. Their genetic repertoires are more diverse than the best-studied free-living kinetoplastids, which is likely a reflection of their higher metabolic potential. Mitochondrial RNAs of these new species undergo the most extensive U insertion/deletion editing reported so far, and limited deaminative C-to-U and A-to-I editing, but we find no evidence for mitochondrial trans-splicing.
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Affiliation(s)
- Denis V. Tikhonenkov
- grid.4886.20000 0001 2192 9124Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, 152742 Russia ,grid.446209.d0000 0000 9203 3563AquaBioSafe Laboratory, University of Tyumen, 625003 Tyumen, Russia
| | - Ryan M. R. Gawryluk
- grid.143640.40000 0004 1936 9465Department of Biology, University of Victoria, Victoria, British Columbia V8W 2Y2 Canada
| | - Alexander P. Mylnikov
- grid.4886.20000 0001 2192 9124Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, Borok, 152742 Russia
| | - Patrick J. Keeling
- grid.17091.3e0000 0001 2288 9830Department of Botany, University of British Columbia, Vancouver, British Columbia V6T 1Z4 Canada
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5
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Faktorová D, Kaur B, Valach M, Graf L, Benz C, Burger G, Lukeš J. Targeted integration by homologous recombination enables in situ tagging and replacement of genes in the marine microeukaryote Diplonema papillatum. Environ Microbiol 2020; 22:3660-3670. [PMID: 32548939 DOI: 10.1111/1462-2920.15130] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 06/07/2020] [Accepted: 06/13/2020] [Indexed: 12/17/2022]
Abstract
Diplonemids are a group of highly diverse and abundant marine microeukaryotes that belong to the phylum Euglenozoa and form a sister clade to the well-studied, mostly parasitic kinetoplastids. Very little is known about the biology of diplonemids, as few species have been formally described and just one, Diplonema papillatum, has been studied to a decent extent at the molecular level. Following up on our previous results showing stable but random integration of delivered extraneous DNA, we demonstrate here homologous recombination in D. papillatum. Targeting various constructs to the intended position in the nuclear genome was successful when 5' and 3' homologous regions longer than 1 kbp were used, achieving N-terminal tagging with mCherry and gene replacement of α- and β-tubulins. For more convenient genetic manipulation, we designed a modular plasmid, pDP002, which bears a protein-A tag and used it to generate and express a C-terminally tagged mitoribosomal protein. Lastly, we developed an improved transformation protocol for broader applicability across laboratories. Our robust methodology allows the replacement, integration as well as endogenous tagging of D. papillatum genes, thus opening the door to functional studies in this species and establishing a basic toolkit for reverse genetics of diplonemids in general.
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Affiliation(s)
- Drahomíra Faktorová
- Czech Academy of Sciences, Institute of Parasitology, Biology Centre, Czech Republic.,Faculty of Sciences, University of South Bohemia, Cˇeské Budějovice (Budweis), Czech Republic
| | - Binnypreet Kaur
- Czech Academy of Sciences, Institute of Parasitology, Biology Centre, Czech Republic.,Faculty of Sciences, University of South Bohemia, Cˇeské Budějovice (Budweis), Czech Republic
| | - Matus Valach
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, Canada
| | - Lena Graf
- Faculty of Sciences, University of South Bohemia, Cˇeské Budějovice (Budweis), Czech Republic.,Present address: Johannes Kepler University, Linz, Austria
| | - Corinna Benz
- Czech Academy of Sciences, Institute of Parasitology, Biology Centre, Czech Republic
| | - Gertraud Burger
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, Canada
| | - Julius Lukeš
- Czech Academy of Sciences, Institute of Parasitology, Biology Centre, Czech Republic.,Faculty of Sciences, University of South Bohemia, Cˇeské Budějovice (Budweis), Czech Republic
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6
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Kaur B, Záhonová K, Valach M, Faktorová D, Prokopchuk G, Burger G, Lukeš J. Gene fragmentation and RNA editing without borders: eccentric mitochondrial genomes of diplonemids. Nucleic Acids Res 2020; 48:2694-2708. [PMID: 31919519 PMCID: PMC7049700 DOI: 10.1093/nar/gkz1215] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 12/14/2019] [Accepted: 01/08/2020] [Indexed: 11/20/2022] Open
Abstract
Diplonemids are highly abundant heterotrophic marine protists. Previous studies showed that their strikingly bloated mitochondrial genome is unique because of systematic gene fragmentation and manifold RNA editing. Here we report a comparative study of mitochondrial genome architecture, gene structure and RNA editing of six recently isolated, phylogenetically diverse diplonemid species. Mitochondrial gene fragmentation and modes of RNA editing, which include cytidine-to-uridine (C-to-U) and adenosine-to-inosine (A-to-I) substitutions and 3′ uridine additions (U-appendage), are conserved across diplonemids. Yet as we show here, all these features have been pushed to their extremes in the Hemistasiidae lineage. For example, Namystynia karyoxenos has its genes fragmented into more than twice as many modules than other diplonemids, with modules as short as four nucleotides. Furthermore, we detected in this group multiple A-appendage and guanosine-to-adenosine (G-to-A) substitution editing events not observed before in diplonemids and found very rarely elsewhere. With >1,000 sites, C-to-U and A-to-I editing in Namystynia is nearly 10 times more frequent than in other diplonemids. The editing density of 12% in coding regions makes Namystynia’s the most extensively edited transcriptome described so far. Diplonemid mitochondrial genome architecture, gene structure and post-transcriptional processes display such high complexity that they challenge all other currently known systems.
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Affiliation(s)
- Binnypreet Kaur
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, 37005 České Budějovice (Budweis), Czech Republic.,Faculty of Sciences, University of South Bohemia, 37005 České Budějovice (Budweis), Czech Republic
| | - Kristína Záhonová
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, 37005 České Budějovice (Budweis), Czech Republic.,Faculty of Science, Charles University, BIOCEV, 25250 Vestec, Czech Republic
| | - Matus Valach
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, H3T 1J4 Montreal, Canada
| | - Drahomíra Faktorová
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, 37005 České Budějovice (Budweis), Czech Republic.,Faculty of Sciences, University of South Bohemia, 37005 České Budějovice (Budweis), Czech Republic
| | - Galina Prokopchuk
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, 37005 České Budějovice (Budweis), Czech Republic
| | - Gertraud Burger
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, H3T 1J4 Montreal, Canada
| | - Julius Lukeš
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, 37005 České Budějovice (Budweis), Czech Republic.,Faculty of Sciences, University of South Bohemia, 37005 České Budějovice (Budweis), Czech Republic
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7
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Vesteg M, Hadariová L, Horváth A, Estraño CE, Schwartzbach SD, Krajčovič J. Comparative molecular cell biology of phototrophic euglenids and parasitic trypanosomatids sheds light on the ancestor of Euglenozoa. Biol Rev Camb Philos Soc 2019; 94:1701-1721. [PMID: 31095885 DOI: 10.1111/brv.12523] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 04/30/2019] [Accepted: 05/02/2019] [Indexed: 01/23/2023]
Abstract
Parasitic trypanosomatids and phototrophic euglenids are among the most extensively studied euglenozoans. The phototrophic euglenid lineage arose relatively recently through secondary endosymbiosis between a phagotrophic euglenid and a prasinophyte green alga that evolved into the euglenid secondary chloroplast. The parasitic trypanosomatids (i.e. Trypanosoma spp. and Leishmania spp.) and the freshwater phototrophic euglenids (i.e. Euglena gracilis) are the most evolutionary distant lineages in the Euglenozoa phylogenetic tree. The molecular and cell biological traits they share can thus be considered as ancestral traits originating in the common euglenozoan ancestor. These euglenozoan ancestral traits include common mitochondrial presequence motifs, respiratory chain complexes containing various unique subunits, a unique ATP synthase structure, the absence of mitochondria-encoded transfer RNAs (tRNAs), a nucleus with a centrally positioned nucleolus, closed mitosis without dissolution of the nuclear membrane and nucleoli, a nuclear genome containing the unusual 'J' base (β-D-glucosyl-hydroxymethyluracil), processing of nucleus-encoded precursor messenger RNAs (pre-mRNAs) via spliced-leader RNA (SL-RNA) trans-splicing, post-transcriptional gene silencing by the RNA interference (RNAi) pathway and the absence of transcriptional regulation of nuclear gene expression. Mitochondrial uridine insertion/deletion RNA editing directed by guide RNAs (gRNAs) evolved in the ancestor of the kinetoplastid lineage. The evolutionary origin of other molecular features known to be present only in either kinetoplastids (i.e. polycistronic transcripts, compaction of nuclear genomes) or euglenids (i.e. monocistronic transcripts, huge genomes, many nuclear cis-spliced introns, polyproteins) is unclear.
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Affiliation(s)
- Matej Vesteg
- Department of Biology and Ecology, Faculty of Natural Sciences, Matej Bel University, 974 01, Banská Bystrica, Slovakia
| | - Lucia Hadariová
- Biotechnology and Biomedicine Center of the Academy of Sciences and Charles University in Vestec (BIOCEV), 252 50, Vestec, Czech Republic.,Department of Parasitology, Faculty of Science, Charles University in Prague, 128 44, Prague, Czech Republic
| | - Anton Horváth
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, 842 15, Bratislava, Slovakia
| | - Carlos E Estraño
- Department of Biological Sciences, University of Memphis, Memphis, TN, 38152-3560, USA
| | - Steven D Schwartzbach
- Department of Biological Sciences, University of Memphis, Memphis, TN, 38152-3560, USA
| | - Juraj Krajčovič
- Department of Biology, Faculty of Natural Sciences, University of ss. Cyril and Methodius, 917 01, Trnava, Slovakia
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8
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Burger G, Valach M. Perfection of eccentricity: Mitochondrial genomes of diplonemids. IUBMB Life 2018; 70:1197-1206. [PMID: 30304578 DOI: 10.1002/iub.1927] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 07/09/2018] [Accepted: 07/10/2018] [Indexed: 01/14/2023]
Abstract
Mitochondria are the sandbox of evolution as exemplified most particularly by the diplonemids, a group of marine microeukaryotes. These protists are uniquely characterized by their highly multipartite mitochondrial genome and systematically fragmented genes whose pieces are spread out over several dozens of chromosomes. The type species Diplonema papillatum was the first member of this group in which the expression of fragmented mitochondrial genes was investigated experimentally. We now know that gene expression involves separate transcription of gene pieces (modules), RNA editing of module transcripts, and module joining to mature mRNAs and rRNAs. The mechanism of cognate module recognition and ligation is distinct from known intron splicing and remains to be uncovered. Here, we review the current status of research on mitochondrial genome architecture, as well as gene complement, structure, and expression modes in diplonemids. Further, we discuss the potential molecular mechanisms of posttranscriptional processing, and finally reflect on the evolutionary trajectories and trends of mtDNA evolution as seen in this protist group. © 2018 IUBMB Life, 70(12):1197-1206, 2018.
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Affiliation(s)
- Gertraud Burger
- Département de Biochimie, Robert Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montréal, Québec, Canada
| | - Matus Valach
- Département de Biochimie, Robert Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montréal, Québec, Canada
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9
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Yan Y, Acevedo M, Mignacca L, Desjardins P, Scott N, Imane R, Quenneville J, Robitaille J, Feghaly A, Gagnon E, Ferbeyre G, Major F. The sequence features that define efficient and specific hAGO2-dependent miRNA silencing guides. Nucleic Acids Res 2018; 46:8181-8196. [PMID: 30239883 PMCID: PMC6144789 DOI: 10.1093/nar/gky546] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Revised: 05/10/2018] [Accepted: 06/05/2018] [Indexed: 01/18/2023] Open
Abstract
MicroRNAs (miRNAs) are ribonucleic acids (RNAs) of ∼21 nucleotides that interfere with the translation of messenger RNAs (mRNAs) and play significant roles in development and diseases. In bilaterian animals, the specificity of miRNA targeting is determined by sequence complementarity involving the seed. However, the role of the remaining nucleotides (non-seed) is only vaguely defined, impacting negatively on our ability to efficiently use miRNAs exogenously to control gene expression. Here, using reporter assays, we deciphered the role of the base pairs formed between the non-seed region and target mRNA. We used molecular modeling to reveal that this mechanism corresponds to the formation of base pairs mediated by ordered motions of the miRNA-induced silencing complex. Subsequently, we developed an algorithm based on this distinctive recognition to predict from sequence the levels of mRNA downregulation with high accuracy (r2 > 0.5, P-value < 10-12). Overall, our discovery improves the design of miRNA-guide sequences used to simultaneously downregulate the expression of multiple predetermined target genes.
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Affiliation(s)
- Yifei Yan
- Département de biochimie et médecine moléculaire, Université de Montréal, Montréal, Québec H3C 3J7, Canada
- Institut de recherche en immunologie et en cancérologie (IRIC), Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Mariana Acevedo
- Département de biochimie et médecine moléculaire, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Lian Mignacca
- Département de biochimie et médecine moléculaire, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Philippe Desjardins
- Institut de recherche en immunologie et en cancérologie (IRIC), Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Nicolas Scott
- Institut de recherche en immunologie et en cancérologie (IRIC), Université de Montréal, Montréal, Québec H3C 3J7, Canada
- Département d’informatique et de recherche opérationnelle, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Roqaya Imane
- Institut de recherche en immunologie et en cancérologie (IRIC), Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Jordan Quenneville
- Institut de recherche en immunologie et en cancérologie (IRIC), Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Julie Robitaille
- Département de biochimie et médecine moléculaire, Université de Montréal, Montréal, Québec H3C 3J7, Canada
- Institut de recherche en immunologie et en cancérologie (IRIC), Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Albert Feghaly
- Institut de recherche en immunologie et en cancérologie (IRIC), Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Etienne Gagnon
- Institut de recherche en immunologie et en cancérologie (IRIC), Université de Montréal, Montréal, Québec H3C 3J7, Canada
- Département de microbiologie, infectiologie et immunologie, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Gerardo Ferbeyre
- Département de biochimie et médecine moléculaire, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - François Major
- Institut de recherche en immunologie et en cancérologie (IRIC), Université de Montréal, Montréal, Québec H3C 3J7, Canada
- Département d’informatique et de recherche opérationnelle, Université de Montréal, Montréal, Québec H3C 3J7, Canada
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10
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Valach M, Léveillé-Kunst A, Gray MW, Burger G. Respiratory chain Complex I of unparalleled divergence in diplonemids. J Biol Chem 2018; 293:16043-16056. [PMID: 30166340 DOI: 10.1074/jbc.ra118.005326] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2018] [Indexed: 12/14/2022] Open
Abstract
Mitochondrial genes of Euglenozoa (Kinetoplastida, Diplonemea, and Euglenida) are notorious for being barely recognizable, raising the question of whether such divergent genes actually code for functional proteins. Here we demonstrate the translation and identify the function of five previously unassigned y genes encoded by mitochondrial DNA (mtDNA) of diplonemids. As is the rule in diplonemid mitochondria, y genes are fragmented, with gene pieces transcribed separately and then trans-spliced to form contiguous mRNAs. Further, y transcripts undergo massive RNA editing, including uridine insertions that generate up to 16-residue-long phenylalanine tracts, a feature otherwise absent from conserved mitochondrial proteins. By protein sequence analyses, MS, and enzymatic assays in Diplonema papillatum, we show that these y genes encode the subunits Nad2, -3, -4L, -6, and -9 of the respiratory chain Complex I (CI; NADH:ubiquinone oxidoreductase). The few conserved residues of these proteins are essentially those involved in proton pumping across the inner mitochondrial membrane and in coupling ubiquinone reduction to proton pumping (Nad2, -3, -4L, and -6) and in interactions with subunits containing electron-transporting Fe-S clusters (Nad9). Thus, in diplonemids, 10 CI subunits are mtDNA-encoded. Further, MS of D. papillatum CI allowed identification of 26 conventional and 15 putative diplonemid-specific nucleus-encoded components. Most conventional accessory subunits are well-conserved but unusually long, possibly compensating for the streamlined mtDNA-encoded components and for missing, otherwise widely distributed, conventional subunits. Finally, D. papillatum CI predominantly exists as a supercomplex I:III:IV that is exceptionally stable, making this protist an organism of choice for structural studies.
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Affiliation(s)
- Matus Valach
- From the Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, Quebec H3T 1J4, Canada and
| | - Alexandra Léveillé-Kunst
- From the Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, Quebec H3T 1J4, Canada and
| | - Michael W Gray
- the Department of Biochemistry and Molecular Biology and Centre for Comparative Genomics and Evolutionary Bioinformatics, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Gertraud Burger
- From the Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, Quebec H3T 1J4, Canada and
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11
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Okamoto N, Gawryluk RMR, Del Campo J, Strassert JFH, Lukeš J, Richards TA, Worden AZ, Santoro AE, Keeling PJ. A Revised Taxonomy of Diplonemids Including the Eupelagonemidae n. fam. and a Type Species, Eupelagonema oceanica n. gen. & sp. J Eukaryot Microbiol 2018; 66:519-524. [PMID: 30080299 DOI: 10.1111/jeu.12679] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Revised: 06/16/2018] [Accepted: 07/12/2018] [Indexed: 12/20/2022]
Abstract
Recent surveys of marine microbial diversity have identified a previously unrecognized lineage of diplonemid protists as being among the most diverse heterotrophic eukaryotes in global oceans. Despite their monophyly (and assumed importance), they lack a formal taxonomic description, and are informally known as deep-sea pelagic diplonemids (DSPDs) or marine diplonemids. Recently, we documented morphology and molecular sequences from several DSPDs, one of which is particularly widespread and abundant in environmental sequence data. To simplify the communication of future work on this important group, here we formally propose to erect the family Eupelagonemidae to encompass this clade, as well as a formal genus and species description for the apparently most abundant phylotype, Eupelagonema oceanica, for which morphological information and single-cell amplified genome data are currently available.
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Affiliation(s)
- Noriko Okamoto
- Department of Botany, University of British Columbia, 3529-6270 University Boulevard, Boulevard, British Columbia, Canada
| | - Ryan M R Gawryluk
- Department of Botany, University of British Columbia, 3529-6270 University Boulevard, Boulevard, British Columbia, Canada
| | - Javier Del Campo
- Department of Botany, University of British Columbia, 3529-6270 University Boulevard, Boulevard, British Columbia, Canada
| | - Jürgen F H Strassert
- Department of Botany, University of British Columbia, 3529-6270 University Boulevard, Boulevard, British Columbia, Canada
| | - Julius Lukeš
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Faculty of Sciences, University of South Bohemia, Branišovská 31, 370 05, České Budějovice (Budweis), Czech Republic
| | - Thomas A Richards
- Biosciences, University of Exeter, Geoffrey Pope Building, Exeter, EX4 4QD, United Kingdom
| | - Alexandra Z Worden
- Monterey Bay Aquarium Research Institute, Moss Landing, California, 95039, USA
| | - Alyson E Santoro
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, California, 93106, USA
| | - Patrick J Keeling
- Department of Botany, University of British Columbia, 3529-6270 University Boulevard, Boulevard, British Columbia, Canada
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12
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Tashyreva D, Prokopchuk G, Yabuki A, Kaur B, Faktorová D, Votýpka J, Kusaka C, Fujikura K, Shiratori T, Ishida KI, Horák A, Lukeš J. Phylogeny and Morphology of New Diplonemids from Japan. Protist 2018; 169:158-179. [PMID: 29604574 DOI: 10.1016/j.protis.2018.02.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 02/02/2018] [Accepted: 02/05/2018] [Indexed: 10/18/2022]
Abstract
Diplonemids were recently found to be the most species-rich group of marine planktonic protists. Based on phylogenetic analysis of 18S rRNA gene sequences and morphological observations, we report the description of new members of the genus Rhynchopus - R. humris sp. n. and R. serpens sp. n., and the establishment of two new genera - Lacrimia gen. n. and Sulcionema gen. n., represented by L. lanifica sp. n. and S. specki sp. n., respectively. In addition, we describe the organism formerly designated as Diplonema sp. 2 (ATCC 50224) as Flectonema neradi gen. n., sp. n. The newly described diplonemids share a common set of traits. Cells are sac-like but variable in shape and size, highly metabolic, and surrounded by a naked cell membrane, which is supported by a tightly packed corset of microtubules. They carry a single highly reticulated peripheral mitochondrion containing a large amount of mitochondrial DNA, with lamellar cristae. The cytopharyngeal complex and flagellar pocket are contiguous and have separate openings. Two parallel flagella are inserted sub-apically into a pronounced flagellar pocket. Rhynchopus species have their flagella concealed in trophic stages and fully developed in swimming stages, while they permanently protrude in all other known diplonemid species.
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Affiliation(s)
- Daria Tashyreva
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic
| | - Galina Prokopchuk
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic
| | - Akinori Yabuki
- Department of Marine Diversity, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Binnypreet Kaur
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Science, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Drahomíra Faktorová
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Science, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Jan Votýpka
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Sciences, Charles University, Prague, Czech Republic
| | - Chiho Kusaka
- Department of Marine Diversity, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Katsunori Fujikura
- Department of Marine Diversity, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | | | - Ken-Ichiro Ishida
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Aleš Horák
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Science, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Julius Lukeš
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Science, University of South Bohemia, České Budějovice (Budweis), Czech Republic.
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13
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Kaur B, Valach M, Peña-Diaz P, Moreira S, Keeling PJ, Burger G, Lukeš J, Faktorová D. Transformation of Diplonema papillatum, the type species of the highly diverse and abundant marine microeukaryotes Diplonemida (Euglenozoa). Environ Microbiol 2018; 20:1030-1040. [PMID: 29318727 DOI: 10.1111/1462-2920.14041] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 12/13/2017] [Accepted: 12/15/2017] [Indexed: 11/30/2022]
Abstract
Diplonema papillatum is the type species of diplonemids, which are among the most abundant and diverse heterotrophic microeukaryotes in the world's oceans. Diplonemids are also known for a unique form of post-transcriptional processing in mitochondria. However, the lack of reverse genetics methodologies in these protists has hampered elucidation of their cellular and molecular biology. Here we report a protocol for D. papillatum transformation. We have identified several antibiotics to which D. papillatum is sensitive and thus are suitable selectable markers, and focus in particular on puromycin. Constructs were designed encoding antibiotic resistance markers, fluorescent tags, and additional genomic sequences from D. papillatum to facilitate vector integration into chromosomes. We established conditions for effective electroporation, and demonstrate that electroporated constructs can be stably integrated in the D. papillatum nuclear genome. In D. papillatum transformants, the heterologous puromycin resistance gene is transcribed into mRNA and translated into protein, as determined by Southern hybridization, reverse transcription, and Western blot analyses. This is the first documented case of transformation in a euglenozoan protist outside the well-studied kinetoplastids, making D. papillatum a genetically tractable organism and potentially a model system for marine microeukaryotes.
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Affiliation(s)
- Binnypreet Kaur
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic.,Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Matus Valach
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, Canada
| | - Priscila Peña-Diaz
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic
| | - Sandrine Moreira
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, Canada
| | - Patrick J Keeling
- Botany Department, University of British Columbia, Vancouver, Canada
| | - Gertraud Burger
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, Canada
| | - Julius Lukeš
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic.,Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Drahomíra Faktorová
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic.,Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
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14
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Faktorová D, Valach M, Kaur B, Burger G, Lukeš J. Mitochondrial RNA Editing and Processing in Diplonemid Protists. RNA METABOLISM IN MITOCHONDRIA 2018. [DOI: 10.1007/978-3-319-78190-7_6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
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15
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Valach M, Moreira S, Hoffmann S, Stadler PF, Burger G. Keeping it complicated: Mitochondrial genome plasticity across diplonemids. Sci Rep 2017; 7:14166. [PMID: 29074957 PMCID: PMC5658414 DOI: 10.1038/s41598-017-14286-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 10/06/2017] [Indexed: 01/30/2023] Open
Abstract
Chromosome rearrangements are important drivers in genome and gene evolution, with implications ranging from speciation to development to disease. In the flagellate Diplonema papillatum (Euglenozoa), mitochondrial genome rearrangements have resulted in nearly hundred chromosomes and a systematic dispersal of gene fragments across the multipartite genome. Maturation into functional RNAs involves separate transcription of gene pieces, joining of precursor RNAs via trans-splicing, and RNA editing by substitution and uridine additions both reconstituting crucial coding sequence. How widespread these unusual features are across diplonemids is unclear. We have analyzed the mitochondrial genomes and transcriptomes of four species from the Diplonema/Rhynchopus clade, revealing a considerable genomic plasticity. Although gene breakpoints, and thus the total number of gene pieces (~80), are essentially conserved across this group, the number of distinct chromosomes varies by a factor of two, with certain chromosomes combining up to eight unrelated gene fragments. Several internal protein-coding gene pieces overlap substantially, resulting, for example, in a stretch of 22 identical amino acids in cytochrome c oxidase subunit 1 and NADH dehydrogenase subunit 5. Finally, the variation of post-transcriptional editing patterns across diplonemids indicates compensation of two adverse trends: rapid sequence evolution and loss of genetic information through unequal chromosome segregation.
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Affiliation(s)
- Matus Valach
- Department of biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, 2900 Edouard-Montpetit, Montreal, H3T 1J4, QC, Canada.
| | - Sandrine Moreira
- Department of biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, 2900 Edouard-Montpetit, Montreal, H3T 1J4, QC, Canada.,Department of Biochemistry and Molecular Biophysics, Columbia University, Hammer Health Science Center, 701 W 168th St, New York, NY, 10031, USA
| | - Steve Hoffmann
- Leipzig University, LIFE - Leipzig Research Center for Civilization Diseases, Haertelstrasse 16-18, Leipzig, D-04107, Germany
| | - Peter F Stadler
- Bioinformatics Group, Department Computer Science, and Interdisciplinary Center for Bioinformatics, University Leipzig, Härtelstrasse 16-18, D-04107, Leipzig, Germany.,German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Competence Center for Scalable Data Services and Solutions, and Leipzig Research Center for Civilization Diseases, University Leipzig, D-04107, Leipzig, Germany.,Max Planck Institute for Mathematics in the Sciences, Inselstrasse 22, D-04103, Leipzig, Germany.,Fraunhofer Institute for Cell Therapy and Immunology, Perlickstrasse 1, D-04103, Leipzig, Germany.,Department of Theoretical Chemistry of the University of Vienna, Währingerstrasse 17, A-1090, Vienna, Austria.,Center for RNA in Technology and Health, University of Copenhagen, Grønnegårdsvej 3, 1870, Frederiksberg C, Denmark.,Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM, 87501, USA
| | - Gertraud Burger
- Department of biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, 2900 Edouard-Montpetit, Montreal, H3T 1J4, QC, Canada.
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16
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Yang J, Harding T, Kamikawa R, Simpson AGB, Roger AJ. Mitochondrial Genome Evolution and a Novel RNA Editing System in Deep-Branching Heteroloboseids. Genome Biol Evol 2017; 9:1161-1174. [PMID: 28453770 PMCID: PMC5421314 DOI: 10.1093/gbe/evx086] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/25/2017] [Indexed: 12/20/2022] Open
Abstract
Discoba (Excavata) is an evolutionarily important group of eukaryotes that includes Jakobida, with the most bacterial-like mitochondrial genomes known, and Euglenozoa, many of which have extensively fragmented mitochondrial genomes. However, little is known about the mitochondrial genomes of Heterolobosea, the third main group of Discoba. Here, we studied two heteroloboseids—an undescribed amoeba “BB2” and Pharyngomonas kirbyi. Phylogenomic analysis revealed that they form a clade that is a sister group to all other Heterolobosea. We characterized the mitochondrial genomes of BB2 and P. kirbyi, which encoded 44 and 48 putative protein-coding genes respectively. Their gene contents were similar to that of Naegleria. In BB2, mitochondrially encoded RNAs were heavily edited, with ∼500 mononucleotide insertion events, mostly guanosines. These insertions always have the same identity as an adjacent nucleotide. Editing occurs in all ribosomal RNAs and protein-coding transcripts except one, and half of the transfer RNAs. Analysis of Illumina deep-sequencing data suggested that this RNA editing is very accurate and efficient, and most likely co-transcriptional. The dissimilarity of this editing process to other RNA editing phenomena in discobids, as well as its apparent absence in P. kirbyi, suggest that this remarkably extensive system of insertional editing evolved independently in the BB2 lineage, after its divergence from the P. kirbyi lineage.
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Affiliation(s)
- Jiwon Yang
- Centre for Comparative Genomics and Evolutionary Bioinformatics, Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Tommy Harding
- Centre for Comparative Genomics and Evolutionary Bioinformatics, Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Ryoma Kamikawa
- Graduate School of Human and Environmental Studies, Graduate School of Global Environmental Studies, Kyoto University, Japan
| | - Alastair G B Simpson
- Centre for Comparative Genomics and Evolutionary Bioinformatics and Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada.,Program in Integrated Microbial Biodiversity, Canadian Institute for Advanced Research, Toronto, Ontario, Canada
| | - Andrew J Roger
- Centre for Comparative Genomics and Evolutionary Bioinformatics, Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada.,Program in Integrated Microbial Biodiversity, Canadian Institute for Advanced Research, Toronto, Ontario, Canada
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17
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Valach M, Moreira S, Faktorová D, Lukeš J, Burger G. Post-transcriptional mending of gene sequences: Looking under the hood of mitochondrial gene expression in diplonemids. RNA Biol 2016; 13:1204-1211. [PMID: 27715490 DOI: 10.1080/15476286.2016.1240143] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
The instructions to make proteins and structural RNAs are laid down in gene sequences. Yet, in certain instances, these primary instructions need to be modified considerably during gene expression, most often at the transcript level. Here we review a case of massive post-transcriptional revisions via trans-splicing and RNA editing, a phenomenon occurring in mitochondria of a recently recognized protist group, the diplonemids. As of now, the various post-transcriptional steps have been cataloged in detail, but how these processes function is still unknown. Since genetic manipulation techniques such as gene replacement and RNA interference have not yet been established for these organisms, alternative strategies have to be deployed. Here, we discuss the experimental and bioinformatics approaches that promise to unravel the molecular machineries of trans-splicing and RNA editing in Diplonema mitochondria.
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Affiliation(s)
- Matus Valach
- a Department of Biochemistry and Robert-Cedergren , Center for Bioinformatics and Genomics, Université de Montréal , Montreal , Canada
| | - Sandrine Moreira
- a Department of Biochemistry and Robert-Cedergren , Center for Bioinformatics and Genomics, Université de Montréal , Montreal , Canada
| | - Drahomíra Faktorová
- b Institute of Parasitology, Biology Center and Faculty of Sciences, University of South Bohemia , České Budějovice , Czech Republic
| | - Julius Lukeš
- b Institute of Parasitology, Biology Center and Faculty of Sciences, University of South Bohemia , České Budějovice , Czech Republic.,c Canadian Institute for Advanced Research , Toronto , Canada
| | - Gertraud Burger
- a Department of Biochemistry and Robert-Cedergren , Center for Bioinformatics and Genomics, Université de Montréal , Montreal , Canada
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18
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Yabuki A, Tanifuji G, Kusaka C, Takishita K, Fujikura K. Hyper-eccentric structural genes in the mitochondrial genome of the algal parasite Hemistasia phaeocysticola. Genome Biol Evol 2016; 8:2870-2878. [PMID: 27566761 PMCID: PMC5630924 DOI: 10.1093/gbe/evw207] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Diplonemid mitochondria are considered to have very eccentric structural genes. Coding regions of individual diplonemid mitochondrial genes are fragmented into small pieces and found on different circular DNAs. Short RNAs transcribed from each DNA molecule mature through a unique RNA maturation process involving assembly and three types of RNA editing (i.e., U insertion and A-to-I and C-to-U substitutions), although the molecular mechanism(s) of RNA maturation and the evolutionary history of these eccentric structural genes still remain to be understood. Since the gene fragmentation pattern is generally conserved among the diplonemid species studied to date, it was considered that their structural complexity has plateaued and further gene fragmentation could not occur. Here, we show the mitochondrial gene structure of Hemistasia phaeocysticola, which was recently identified as a member of a novel lineage in diplonemids, by comparison of the mitochondrial DNA sequences with cDNA sequences synthesized from mature mRNA. The genes of H. phaeocysticola are fragmented much more finely than those of other diplonemids studied to date. Furthermore, in addition to all known types of RNA editing, it is suggested that a novel processing step (i.e., secondary RNA insertion) is involved in the RNA maturation in the mitochondria of H. phaeocysticola. Our findings demonstrate the tremendous plasticity of mitochondrial gene structures.
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Affiliation(s)
- Akinori Yabuki
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa 237-0061, Japan
| | - Goro Tanifuji
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan
| | - Chiho Kusaka
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa 237-0061, Japan
| | - Kiyotaka Takishita
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa 237-0061, Japan
| | - Katsunori Fujikura
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa 237-0061, Japan
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19
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Burger G, Moreira S, Valach M. Genes in Hiding. Trends Genet 2016; 32:553-565. [PMID: 27460648 DOI: 10.1016/j.tig.2016.06.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 06/23/2016] [Accepted: 06/24/2016] [Indexed: 12/25/2022]
Abstract
Unrecognizable genes are an unsettling problem in genomics. Here, we survey the various types of cryptic genes and the corresponding deciphering strategies employed by cells. Encryption that renders genes substantially different from homologs in other species includes sequence substitution, insertion, deletion, fragmentation plus scrambling, and invasion by mobile genetic elements. Cells decode cryptic genes at the DNA, RNA or protein level. We will focus on a recently discovered case of unparalleled encryption involving massive gene fragmentation and nucleotide deletions and substitutions, occurring in the mitochondrial genome of a poorly understood protist group, the diplonemids. This example illustrates that comprehensive gene detection requires not only auxiliary sequence information - transcriptome and proteome data - but also knowledge about a cell's deciphering arsenal.
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Affiliation(s)
- Gertraud Burger
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, Canada.
| | - Sandrine Moreira
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, Canada
| | - Matus Valach
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montreal, Canada
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20
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Burger G. Non-functional genes repaired at the RNA level. C R Biol 2016; 339:289-95. [PMID: 27180109 DOI: 10.1016/j.crvi.2016.04.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 04/12/2016] [Indexed: 11/29/2022]
Abstract
Genomes and genes continuously evolve. Gene sequences undergo substitutions, deletions or nucleotide insertions; mobile genetic elements invade genomes and interleave in genes; chromosomes break, even within genes, and pieces reseal in reshuffled order. To maintain functional gene products and assure an organism's survival, two principal strategies are used - either repair of the gene itself or of its product. I will introduce common types of gene aberrations and how gene function is restored secondarily, and then focus on systematically fragmented genes found in a poorly studied protist group, the diplonemids. Expression of their broken genes involves restitching of pieces at the RNA-level, and substantial RNA editing, to compensate for point mutations. I will conclude with thoughts on how such a grotesquely unorthodox system may have evolved, and why this group of organisms persists and thrives since tens of millions of years.
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Affiliation(s)
- Gertraud Burger
- Department of Biochemistry, Robert-Cedergren Centre for Bioinformatics and Genomics, Université de Montréal, Montréal, Canada.
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21
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Faktorová D, Dobáková E, Peña-Diaz P, Lukeš J. From simple to supercomplex: mitochondrial genomes of euglenozoan protists. F1000Res 2016. [PMID: 27018240 DOI: 10.12688/f1000research.8040.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mitochondria are double membrane organelles of endosymbiotic origin, best known for constituting the centre of energetics of a eukaryotic cell. They contain their own mitochondrial genome, which as a consequence of gradual reduction during evolution typically contains less than two dozens of genes. In this review, we highlight the extremely diverse architecture of mitochondrial genomes and mechanisms of gene expression between the three sister groups constituting the phylum Euglenozoa - Euglenida, Diplonemea and Kinetoplastea. The earliest diverging euglenids possess a simplified mitochondrial genome and a conventional gene expression, whereas both are highly complex in the two other groups. The expression of their mitochondrial-encoded proteins requires extensive post-transcriptional modifications guided by complex protein machineries and multiple small RNA molecules. Moreover, the least studied diplonemids, which have been recently discovered as a highly abundant component of the world ocean plankton, possess one of the most complicated mitochondrial genome organisations known to date.
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Affiliation(s)
- Drahomíra Faktorová
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Eva Dobáková
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Departments of Biochemistry and Genetics, Faculty of Natural Sciences, Comenius Universtity, Bratislava, Slovakia
| | - Priscila Peña-Diaz
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic
| | - Julius Lukeš
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic; Canadian Institute for Adavanced Research, Toronto, Ontario, Canada
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22
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Faktorová D, Dobáková E, Peña-Diaz P, Lukeš J. From simple to supercomplex: mitochondrial genomes of euglenozoan protists. F1000Res 2016; 5. [PMID: 27018240 PMCID: PMC4806707 DOI: 10.12688/f1000research.8040.2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/15/2016] [Indexed: 01/06/2023] Open
Abstract
Mitochondria are double membrane organelles of endosymbiotic origin, best known for constituting the centre of energetics of a eukaryotic cell. They contain their own mitochondrial genome, which as a consequence of gradual reduction during evolution typically contains less than two dozens of genes. In this review, we highlight the extremely diverse architecture of mitochondrial genomes and mechanisms of gene expression between the three sister groups constituting the phylum Euglenozoa - Euglenida, Diplonemea and Kinetoplastea. The earliest diverging euglenids possess a simplified mitochondrial genome and a conventional gene expression, whereas both are highly complex in the two other groups. The expression of their mitochondrial-encoded proteins requires extensive post-transcriptional modifications guided by complex protein machineries and multiple small RNA molecules. Moreover, the least studied diplonemids, which have been recently discovered as a highly abundant component of the world ocean plankton, possess one of the most complicated mitochondrial genome organisations known to date.
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Affiliation(s)
- Drahomíra Faktorová
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Eva Dobáková
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Departments of Biochemistry and Genetics, Faculty of Natural Sciences, Comenius Universtity, Bratislava, Slovakia
| | - Priscila Peña-Diaz
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic
| | - Julius Lukeš
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic; Canadian Institute for Adavanced Research, Toronto, Ontario, Canada
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23
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Moreira S, Valach M, Aoulad-Aissa M, Otto C, Burger G. Novel modes of RNA editing in mitochondria. Nucleic Acids Res 2016; 44:4907-19. [PMID: 27001515 PMCID: PMC4889940 DOI: 10.1093/nar/gkw188] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 03/10/2016] [Indexed: 11/20/2022] Open
Abstract
Gene structure and expression in diplonemid mitochondria are unparalleled. Genes are fragmented in pieces (modules) that are separately transcribed, followed by the joining of module transcripts to contiguous RNAs. Some instances of unique uridine insertion RNA editing at module boundaries were noted, but the extent and potential occurrence of other editing types remained unknown. Comparative analysis of deep transcriptome and genome data from Diplonema papillatum mitochondria reveals ∼220 post-transcriptional insertions of uridines, but no insertions of other nucleotides nor deletions. In addition, we detect in total 114 substitutions of cytosine by uridine and adenosine by inosine, amassed into unusually compact clusters. Inosines in transcripts were confirmed experimentally. This is the first report of adenosine-to-inosine editing of mRNAs and ribosomal RNAs in mitochondria. In mRNAs, editing causes mostly amino-acid additions and non-synonymous substitutions; in ribosomal RNAs, it permits formation of canonical secondary structures. Two extensively edited transcripts were compared across four diplonemids. The pattern of uridine-insertion editing is strictly conserved, whereas substitution editing has diverged dramatically, but still rendering diplonemid proteins more similar to other eukaryotic orthologs. We posit that RNA editing not only compensates but also sustains, or even accelerates, ultra-rapid evolution of genome structure and sequence in diplonemid mitochondria.
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Affiliation(s)
- Sandrine Moreira
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics; Université de Montréal, Montreal, H3C 3J7, Canada
| | - Matus Valach
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics; Université de Montréal, Montreal, H3C 3J7, Canada
| | - Mohamed Aoulad-Aissa
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics; Université de Montréal, Montreal, H3C 3J7, Canada
| | - Christian Otto
- Bioinformatics Group, Department of Computer Science, University of Leipzig, Leipzig, D-04109, Germany
| | - Gertraud Burger
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics; Université de Montréal, Montreal, H3C 3J7, Canada
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24
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Gene Loss and Error-Prone RNA Editing in the Mitochondrion of Perkinsela, an Endosymbiotic Kinetoplastid. mBio 2015; 6:e01498-15. [PMID: 26628723 PMCID: PMC4669381 DOI: 10.1128/mbio.01498-15] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Perkinsela is an enigmatic early-branching kinetoplastid protist that lives as an obligate endosymbiont inside Paramoeba (Amoebozoa). We have sequenced the highly reduced mitochondrial genome of Perkinsela, which possesses only six protein-coding genes (cox1, cox2, cox3, cob, atp6, and rps12), despite the fact that the organelle itself contains more DNA than is present in either the host or endosymbiont nuclear genomes. An in silico analysis of two Perkinsela strains showed that mitochondrial RNA editing and processing machineries typical of kinetoplastid flagellates are generally conserved, and all mitochondrial transcripts undergo U-insertion/deletion editing. Canonical kinetoplastid mitochondrial ribosomes are also present. We have developed software tools for accurate and exhaustive mapping of transcriptome sequencing (RNA-seq) reads with extensive U-insertions/deletions, which allows detailed investigation of RNA editing via deep sequencing. With these methods, we show that up to 50% of reads for a given edited region contain errors of the editing system or, less likely, correspond to alternatively edited transcripts. Uridine insertion/deletion-type RNA editing, which occurs in the mitochondrion of kinetoplastid protists, has been well-studied in the model parasite genera Trypanosoma, Leishmania, and Crithidia. Perkinsela provides a unique opportunity to broaden our knowledge of RNA editing machinery from an evolutionary perspective, as it represents the earliest kinetoplastid branch and is an obligatory endosymbiont with extensive reductive trends. Interestingly, up to 50% of mitochondrial transcripts in Perkinsela contain errors. Our study was complemented by use of newly developed software designed for accurate mapping of extensively edited RNA-seq reads obtained by deep sequencing.
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25
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Dobáková E, Flegontov P, Skalický T, Lukeš J. Unexpectedly Streamlined Mitochondrial Genome of the Euglenozoan Euglena gracilis. Genome Biol Evol 2015; 7:3358-67. [PMID: 26590215 PMCID: PMC4700960 DOI: 10.1093/gbe/evv229] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/13/2015] [Indexed: 11/29/2022] Open
Abstract
In this study, we describe the mitochondrial genome of the excavate flagellate Euglena gracilis. Its gene complement is reduced as compared with the well-studied sister groups Diplonemea and Kinetoplastea. We have identified seven protein-coding genes: Three subunits of respiratory complex I (nad1, nad4, and nad5), one subunit of complex III (cob), and three subunits of complex IV (cox1, cox2, and a highly divergent cox3). Moreover, fragments of ribosomal RNA genes have also been identified. Genes encoding subunits of complex V, ribosomal proteins and tRNAs were missing, and are likely located in the nuclear genome. Although mitochondrial genomes of diplonemids and kinetoplastids possess the most complex RNA processing machineries known, including trans-splicing and editing of the uridine insertion/deletion type, respectively, our transcriptomic data suggest their total absence in E. gracilis. This finding supports a scenario in which the complex mitochondrial processing machineries of both sister groups evolved relatively late in evolution from a streamlined genome and transcriptome of their common predecessor.
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Affiliation(s)
- Eva Dobáková
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic Departments of Biochemistry and Genetics, Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia
| | - Pavel Flegontov
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic Life Science Research Centre, Faculty of Science, University of Ostrava, Ostrava, Czech Republic
| | - Tomáš Skalický
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic Faculty of Science, University of South Bohemia, České Budějovice (Budweis), Czech Republic
| | - Julius Lukeš
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic Faculty of Science, University of South Bohemia, České Budějovice (Budweis), Czech Republic Canadian Institute for Advanced Research, Toronto, Ontario, Canada
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26
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Gawronski AR, Turcotte M. RiboFSM: frequent subgraph mining for the discovery of RNA structures and interactions. BMC Bioinformatics 2014; 15 Suppl 13:S2. [PMID: 25434643 PMCID: PMC4248650 DOI: 10.1186/1471-2105-15-s13-s2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Frequent subgraph mining is a useful method for extracting meaningful patterns from a set of graphs or a single large graph. Here, the graph represents all possible RNA structures and interactions. Patterns that are significantly more frequent in this graph over a random graph are extracted. We hypothesize that these patterns are most likely to represent biological mechanisms. The graph representation used is a directed dual graph, extended to handle intermolecular interactions. The graph is sampled for subgraphs, which are labeled using a canonical labeling method and counted. The resulting patterns are compared to those created from a randomized dataset and scored. The algorithm was applied to the mitochondrial genome of the kinetoplastid species Trypanosoma brucei, which has a unique RNA editing mechanism. The most significant patterns contain two stem-loops, indicative of gRNA, and represent interactions of these structures with target mRNA.
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27
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Klimeš V, Gentekaki E, Roger AJ, Eliáš M. A large number of nuclear genes in the human parasite blastocystis require mRNA polyadenylation to create functional termination codons. Genome Biol Evol 2014; 6:1956-61. [PMID: 25015079 PMCID: PMC4159000 DOI: 10.1093/gbe/evu146] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Termination codons in mRNA molecules are typically specified directly by the sequence of the corresponding gene. However, in mitochondria of a few eukaryotic groups, some mRNAs contain the termination codon UAA deriving one or both adenosines from transcript polyadenylation. Here, we show that a similar phenomenon occurs for a substantial number of nuclear genes in Blastocystis spp., divergent unicellular eukaryote gut parasites. Our analyses of published genomic data from Blastocystis sp. subtype 7 revealed that polyadenylation-mediated creation of termination codons occurs in approximately 15% of all nuclear genes. As this phenomenon has not been noticed before, the procedure previously employed to annotate the Blastocystis nuclear genome sequence failed to correctly define the structure of the 3'-ends of hundreds of genes. From sequence data we have obtained from the distantly related Blastocystis sp. subtype 1 strain, we show that this phenomenon is widespread within the Blastocystis genus. Polyadenylation in Blastocystis appears to be directed by a conserved GU-rich element located four nucleotides downstream of the polyadenylation site. Thus, the highly precise positioning of the polyadenylation in Blastocystis has allowed reduction of the 3'-untranslated regions to the point that, in many genes, only one or two nucleotides of the termination codon are left.
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Affiliation(s)
- Vladimír Klimeš
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, Czech Republic
| | - Eleni Gentekaki
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Andrew J Roger
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, CanadaIntegrated Microbial Biodiversity Program, Canadian Institute for Advanced Research, Halifax, Nova Scotia, Canada
| | - Marek Eliáš
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, Czech Republic
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Gray MW. The pre-endosymbiont hypothesis: a new perspective on the origin and evolution of mitochondria. Cold Spring Harb Perspect Biol 2014; 6:6/3/a016097. [PMID: 24591518 DOI: 10.1101/cshperspect.a016097] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Mitochondrial DNA (mtDNA) is unquestionably the remnant of an α-proteobacterial genome, yet only ~10%-20% of mitochondrial proteins are demonstrably α-proteobacterial in origin (the "α-proteobacterial component," or APC). The evolutionary ancestry of the non-α-proteobacterial component (NPC) is obscure and not adequately accounted for in current models of mitochondrial origin. I propose that in the host cell that accommodated an α-proteobacterial endosymbiont, much of the NPC was already present, in the form of a membrane-bound metabolic organelle (the premitochondrion) that compartmentalized many of the non-energy-generating functions of the contemporary mitochondrion. I suggest that this organelle also possessed a protein import system and various ion and small-molecule transporters. In such a scenario, an α-proteobacterial endosymbiont could have been converted relatively directly and rapidly into an energy-generating organelle that incorporated the extant metabolic functions of the premitochondrion. This model (the "pre-endosymbiont hypothesis") effectively represents a synthesis of previous, contending mitochondrial origin hypotheses, with the bulk of the mitochondrial proteome (much of the NPC) having an endogenous origin and the minority component (the APC) having a xenogenous origin.
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Affiliation(s)
- Michael W Gray
- Centre for Comparative Genomics and Evolutionary Bioinformatics, Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3M 4R2, Canada
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29
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Valach M, Moreira S, Kiethega GN, Burger G. Trans-splicing and RNA editing of LSU rRNA in Diplonema mitochondria. Nucleic Acids Res 2013; 42:2660-72. [PMID: 24259427 PMCID: PMC3936708 DOI: 10.1093/nar/gkt1152] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Mitochondrial ribosomal RNAs (rRNAs) often display reduced size and deviant secondary structure, and sometimes are fragmented, as are their corresponding genes. Here we report a mitochondrial large subunit rRNA (mt-LSU rRNA) with unprecedented features. In the protist Diplonema, the rnl gene is split into two pieces (modules 1 and 2, 534- and 352-nt long) that are encoded by distinct mitochondrial chromosomes, yet the rRNA is continuous. To reconstruct the post-transcriptional maturation pathway of this rRNA, we have catalogued transcript intermediates by deep RNA sequencing and RT-PCR. Gene modules are transcribed separately. Subsequently, transcripts are end-processed, the module-1 transcript is polyuridylated and the module-2 transcript is polyadenylated. The two modules are joined via trans-splicing that retains at the junction ∼26 uridines, resulting in an extent of insertion RNA editing not observed before in any system. The A-tail of trans-spliced molecules is shorter than that of mono-module 2, and completely absent from mitoribosome-associated mt-LSU rRNA. We also characterize putative antisense transcripts. Antisense-mono-modules corroborate bi-directional transcription of chromosomes. Antisense-mt-LSU rRNA, if functional, has the potential of guiding concomitantly trans-splicing and editing of this rRNA. Together, these findings open a window on the investigation of complex regulatory networks that orchestrate multiple and biochemically diverse post-transcriptional events.
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Affiliation(s)
- Matus Valach
- Department of Biochemistry and Robert-Cedergren Centre for Bioinformatics and Genomics; Université de Montréal, Montreal, H3C 3J7, Canada
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