1
|
Gao P, Zhao Y, Xu G, Zhong Y, Sun C. Unique features of conventional and nonconventional introns in Euglena gracilis. BMC Genomics 2024; 25:595. [PMID: 38872102 PMCID: PMC11170887 DOI: 10.1186/s12864-024-10495-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Accepted: 06/05/2024] [Indexed: 06/15/2024] Open
Abstract
BACKGROUND Nuclear introns in Euglenida have been understudied. This study aimed to investigate nuclear introns in Euglenida by identifying a large number of introns in Euglena gracilis (E. gracilis), including cis-spliced conventional and nonconventional introns, as well as trans-spliced outrons. We also examined the sequence characteristics of these introns. RESULTS A total of 28,337 introns and 11,921 outrons were identified. Conventional and nonconventional introns have distinct splice site features; the former harbour canonical GT/C-AG splice sites, whereas the latter are capable of forming structured motifs with their terminal sequences. We observed that short introns had a preference for canonical GT-AG introns. Notably, conventional introns and outrons in E. gracilis exhibited a distinct cytidine-rich polypyrimidine tract, in contrast to the thymidine-rich tracts observed in other organisms. Furthermore, the SL-RNAs in E. gracilis, as well as in other trans-splicing species, can form a recently discovered motif called the extended U6/5' ss duplex with the respective U6s. We also describe a novel type of alternative splicing pattern in E. gracilis. The tandem repeat sequences of introns in this protist were determined, and their contents were comparable to those in humans. CONCLUSIONS Our findings highlight the unique features of E. gracilis introns and provide insights into the splicing mechanism of these introns, as well as the genomics and evolution of Euglenida.
Collapse
Affiliation(s)
- Pingwei Gao
- Scientific Research Center, Chengdu Medical College, Chengdu, 610500, China
| | - Yali Zhao
- Scientific Research Center, Chengdu Medical College, Chengdu, 610500, China
| | - Guangjie Xu
- Scientific Research Center, Chengdu Medical College, Chengdu, 610500, China
| | - Yujie Zhong
- Clinical Laboratory Department, Zigong Hospital of Women's and Children's Healthcare, Zigong, 643002, China.
| | - Chengfu Sun
- Scientific Research Center, Chengdu Medical College, Chengdu, 610500, China.
| |
Collapse
|
2
|
Heterotrophic euglenid Rhabdomonas costata resembles its phototrophic relatives in many aspects of molecular and cell biology. Sci Rep 2021; 11:13070. [PMID: 34158556 PMCID: PMC8219788 DOI: 10.1038/s41598-021-92174-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 05/28/2021] [Indexed: 02/05/2023] Open
Abstract
Euglenids represent a group of protists with diverse modes of feeding. To date, only a partial genomic sequence of Euglena gracilis and transcriptomes of several phototrophic and secondarily osmotrophic species are available, while primarily heterotrophic euglenids are seriously undersampled. In this work, we begin to fill this gap by presenting genomic and transcriptomic drafts of a primary osmotroph, Rhabdomonas costata. The current genomic assembly length of 100 Mbp is 14× smaller than that of E. gracilis. Despite being too fragmented for comprehensive gene prediction it provided fragments of the mitochondrial genome and comparison of the transcriptomic and genomic data revealed features of its introns, including several candidates for nonconventional types. A set of 39,456 putative R. costata proteins was predicted from the transcriptome. Annotation of the mitochondrial core metabolism provides the first data on the facultatively anaerobic mitochondrion of R. costata, which in most respects resembles the mitochondrion of E. gracilis with a certain level of streamlining. R. costata can synthetise thiamine by enzymes of heterogenous provenances and haem by a mitochondrial-cytoplasmic C4 pathway with enzymes orthologous to those found in E. gracilis. The low percentage of green algae-affiliated genes supports the ancestrally osmotrophic status of this species.
Collapse
|
3
|
Gumińska N, Zakryś B, Milanowski R. A New Type of Circular RNA derived from Nonconventional Introns in Nuclear Genes of Euglenids. J Mol Biol 2020; 433:166758. [PMID: 33316270 DOI: 10.1016/j.jmb.2020.166758] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 12/06/2020] [Accepted: 12/07/2020] [Indexed: 10/22/2022]
Abstract
Nuclear protein-coding genes of euglenids (Discoba, Euglenozoa, Euglenida) contain conventional (spliceosomal) and nonconventional introns. The latter have been found only in euglenozoans. A unique feature of nonconventional introns is the ability to form a stable and slightly conserved RNA secondary structure bringing together intron ends and placing adjacent exons in proximity. To date, little is known about the mechanism of their excision (e.g. whether it involves the spliceosome or not). The tubA gene of Euglena gracilis harbors three conventional and three nonconventional introns. While the conventional introns are excised as lariats, nonconventional introns are present in the cell solely as circular RNAs with full-length ends. Based on this discovery as well as on previous observations indicating that nonconventional introns are observed frequently at unique positions of genes, we suggest that this new type of intronic circRNA might play a role in intron mobility.
Collapse
Affiliation(s)
- Natalia Gumińska
- Institute of Evolutionary Biology, Faculty of Biology, Biological and Chemical Research Center, University of Warsaw, ul. Żwirki i Wigury 101, 02-089 Warsaw, Poland
| | - Bożena Zakryś
- Institute of Evolutionary Biology, Faculty of Biology, Biological and Chemical Research Center, University of Warsaw, ul. Żwirki i Wigury 101, 02-089 Warsaw, Poland
| | - Rafał Milanowski
- Institute of Evolutionary Biology, Faculty of Biology, Biological and Chemical Research Center, University of Warsaw, ul. Żwirki i Wigury 101, 02-089 Warsaw, Poland.
| |
Collapse
|
4
|
Butenko A, Hammond M, Field MC, Ginger ML, Yurchenko V, Lukeš J. Reductionist Pathways for Parasitism in Euglenozoans? Expanded Datasets Provide New Insights. Trends Parasitol 2020; 37:100-116. [PMID: 33127331 DOI: 10.1016/j.pt.2020.10.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 09/30/2020] [Accepted: 10/01/2020] [Indexed: 12/21/2022]
Abstract
The unicellular trypanosomatids belong to the phylum Euglenozoa and all known species are obligate parasites. Distinct lineages infect plants, invertebrates, and vertebrates, including humans. Genome data for marine diplonemids, together with freshwater euglenids and free-living kinetoplastids, the closest known nonparasitic relatives to trypanosomatids, recently became available. Robust phylogenetic reconstructions across Euglenozoa are now possible and place the results of parasite-focused studies into an evolutionary context. Here we discuss recent advances in identifying the factors shaping the evolution of Euglenozoa, focusing on ancestral features generally considered parasite-specific. Remarkably, most of these predate the transition(s) to parasitism, suggesting that the presence of certain preconditions makes a significant lifestyle change more likely.
Collapse
Affiliation(s)
- Anzhelika Butenko
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Science, University of Ostrava, Ostrava, Czech Republic.
| | - Michael Hammond
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic
| | - Mark C Field
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; School of Life Sciences, University of Dundee, Dundee, UK
| | - Michael L Ginger
- School of Applied Sciences, University of Huddersfield, Huddersfield, UK
| | - Vyacheslav Yurchenko
- Faculty of Science, University of Ostrava, Ostrava, Czech Republic; Martsinovsky Institute of Medical Parasitology, Sechenov University, Moscow, Russia
| | - Julius Lukeš
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovice (Budweis), Czech Republic; Faculty of Sciences, University of South Bohemia, České Budějovice (Budweis), Czech Republic.
| |
Collapse
|
5
|
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.
Collapse
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
| |
Collapse
|
6
|
Lax G, Lee WJ, Eglit Y, Simpson A. Ploeotids Represent Much of the Phylogenetic Diversity of Euglenids. Protist 2019; 170:233-257. [PMID: 31102975 DOI: 10.1016/j.protis.2019.03.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Revised: 02/19/2019] [Accepted: 03/01/2019] [Indexed: 11/26/2022]
Abstract
Ploeotids are an assemblage of rigid phagotrophic euglenids that have 10-12 pellicular strips and glide on their posterior flagellum. Molecular phylogenies place them as a poorly resolved, likely paraphyletic assemblage outside the Spirocuta clade of flexible euglenids, which includes the well-known phototrophs and primary osmotrophs. Here, we report SSU rRNA gene sequences from 38 ploeotids, using both single-cell and culture-based methods. Several contain group I or non-canonical introns. Our phylogenetic analyses place ploeotids in 8 distinct clades: Olkasia n. gen., Hemiolia n. gen., Liburna n. gen., Lentomonas, Decastava, Keelungia, Ploeotiidae, and Entosiphon. Ploeotia vitrea, the type of Ploeotia, is closely related to P. oblonga and Serpenomonas costata, but not to Lentomonas. Ploeotia cf. vitrea sensu Lax and Simpson 2013 is not related to P. vitrea and has a different pellicle strip architecture (as imaged by scanning electron microscopy): it instead represents a novel genus and species, Olkasia polycarbonata. We also describe new genera, Hemiolia and Liburna, for the morphospecies Anisonema trepidum and A. glaciale. A recent system proposing 13 suprafamilial taxa that include ploeotids is not supported by our phylogenies. The exact relationships between ploeotid groups remain unresolved and multigene phylogenetics or phylogenomics are needed to address this uncertainty.
Collapse
Affiliation(s)
- Gordon Lax
- Department of Biology, and Centre for Comparative Genomics and Evolutionary Bioinformatics, Dalhousie University, Halifax, NS, Canada
| | - Won Je Lee
- Department of Environment and Energy Engineering, Kyungnam University, Changwon, Republic of Korea
| | - Yana Eglit
- Department of Biology, and Centre for Comparative Genomics and Evolutionary Bioinformatics, Dalhousie University, Halifax, NS, Canada
| | - Alastair Simpson
- Department of Biology, and Centre for Comparative Genomics and Evolutionary Bioinformatics, Dalhousie University, Halifax, NS, Canada.
| |
Collapse
|
7
|
Ebenezer TE, Zoltner M, Burrell A, Nenarokova A, Novák Vanclová AMG, Prasad B, Soukal P, Santana-Molina C, O'Neill E, Nankissoor NN, Vadakedath N, Daiker V, Obado S, Silva-Pereira S, Jackson AP, Devos DP, Lukeš J, Lebert M, Vaughan S, Hampl V, Carrington M, Ginger ML, Dacks JB, Kelly S, Field MC. Transcriptome, proteome and draft genome of Euglena gracilis. BMC Biol 2019; 17:11. [PMID: 30732613 PMCID: PMC6366073 DOI: 10.1186/s12915-019-0626-8] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 01/08/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Photosynthetic euglenids are major contributors to fresh water ecosystems. Euglena gracilis in particular has noted metabolic flexibility, reflected by an ability to thrive in a range of harsh environments. E. gracilis has been a popular model organism and of considerable biotechnological interest, but the absence of a gene catalogue has hampered both basic research and translational efforts. RESULTS We report a detailed transcriptome and partial genome for E. gracilis Z1. The nuclear genome is estimated to be around 500 Mb in size, and the transcriptome encodes over 36,000 proteins and the genome possesses less than 1% coding sequence. Annotation of coding sequences indicates a highly sophisticated endomembrane system, RNA processing mechanisms and nuclear genome contributions from several photosynthetic lineages. Multiple gene families, including likely signal transduction components, have been massively expanded. Alterations in protein abundance are controlled post-transcriptionally between light and dark conditions, surprisingly similar to trypanosomatids. CONCLUSIONS Our data provide evidence that a range of photosynthetic eukaryotes contributed to the Euglena nuclear genome, evidence in support of the 'shopping bag' hypothesis for plastid acquisition. We also suggest that euglenids possess unique regulatory mechanisms for achieving extreme adaptability, through mechanisms of paralog expansion and gene acquisition.
Collapse
Affiliation(s)
- ThankGod E Ebenezer
- School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK.,Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QW, UK
| | - Martin Zoltner
- School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Alana Burrell
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Anna Nenarokova
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, and Faculty of Sciences, University of South Bohemia, 37005, České Budějovice, Czech Republic
| | - Anna M G Novák Vanclová
- Department of Parasitology, Faculty of Science,, Charles University, BIOCEV, 252 50, Vestec, Czech Republic
| | - Binod Prasad
- Cell Biology Division, Department of Biology, University of Erlangen-Nuremberg, 91058, Erlangen, Germany
| | - Petr Soukal
- Department of Parasitology, Faculty of Science,, Charles University, BIOCEV, 252 50, Vestec, Czech Republic
| | - Carlos Santana-Molina
- Centro Andaluz de Biología del Desarrollo (CABD)-CSIC, Pablo de Olavide University, Seville, Spain
| | - Ellis O'Neill
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | - Nerissa N Nankissoor
- Division of Infectious Disease, Department of Medicine, University of Alberta, Edmonton, Alberta, T6G, Canada
| | - Nithya Vadakedath
- Cell Biology Division, Department of Biology, University of Erlangen-Nuremberg, 91058, Erlangen, Germany
| | - Viktor Daiker
- Cell Biology Division, Department of Biology, University of Erlangen-Nuremberg, 91058, Erlangen, Germany
| | - Samson Obado
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY, 10065, USA
| | - Sara Silva-Pereira
- Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, Liverpool, UK
| | - Andrew P Jackson
- Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, Liverpool, UK
| | - Damien P Devos
- Centro Andaluz de Biología del Desarrollo (CABD)-CSIC, Pablo de Olavide University, Seville, Spain
| | - Julius Lukeš
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, and Faculty of Sciences, University of South Bohemia, 37005, České Budějovice, Czech Republic
| | - Michael Lebert
- Cell Biology Division, Department of Biology, University of Erlangen-Nuremberg, 91058, Erlangen, Germany
| | - Sue Vaughan
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Vladimίr Hampl
- Department of Parasitology, Faculty of Science,, Charles University, BIOCEV, 252 50, Vestec, Czech Republic
| | - Mark Carrington
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QW, UK
| | - Michael L Ginger
- Department of Biological and Geographical Sciences, School of Applied Sciences, University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, UK
| | - Joel B Dacks
- Division of Infectious Disease, Department of Medicine, University of Alberta, Edmonton, Alberta, T6G, Canada. .,Department of Life Sciences, The Natural History Museum, Cromwell Road, London, SW7 5BD, UK.
| | - Steven Kelly
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK.
| | - Mark C Field
- School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK. .,Biology Centre, Institute of Parasitology, Czech Academy of Sciences, and Faculty of Sciences, University of South Bohemia, 37005, České Budějovice, Czech Republic.
| |
Collapse
|
8
|
Order of removal of conventional and nonconventional introns from nuclear transcripts of Euglena gracilis. PLoS Genet 2018; 14:e1007761. [PMID: 30365503 PMCID: PMC6221363 DOI: 10.1371/journal.pgen.1007761] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 11/07/2018] [Accepted: 10/12/2018] [Indexed: 11/27/2022] Open
Abstract
Nuclear genes of euglenids and marine diplonemids harbor atypical, nonconventional introns which are not observed in the genomes of other eukaryotes. Nonconventional introns do not have the conserved borders characteristic for spliceosomal introns or the sequence complementary to U1 snRNA at the 5' end. They form a stable secondary structure bringing together both exon/intron junctions, nevertheless, this conformation does not resemble the form of self-splicing or tRNA introns. In the genes studied so far, frequent nonconventional introns insertions at new positions have been observed, whereas conventional introns have been either found at the conserved positions, or simply lost. In this work, we examined the order of intron removal from Euglena gracilis transcripts of the tubA and gapC genes, which contain two types of introns: nonconventional and spliceosomal. The relative order of intron excision was compared for pairs of introns belonging to different types. Furthermore, intermediate products of splicing were analyzed using the PacBio Next Generation Sequencing system. The analysis led to the main conclusion that nonconventional introns are removed in a rapid way but later than spliceosomal introns. Moreover, the observed accumulation of transcripts with conventional introns removed and nonconventional present may suggest the existence of a time gap between the two types of splicing. The existence of conventional spliceosomal introns in genes of eukaryotic organisms is a well-known theorem. However, genes of the unicellular algae group, euglenids, contain also another type of introns, so-called nonconventional ones. They lack canonical borders, a feature most characteristic for conventional introns and form a stable secondary structure bringing together their ends. Along with the increasing popularity of whole genome studies, nonconventional introns were also disclosed in the genes of other protists, diplonemids. In this study we were particularly interested which introns–conventional or nonconventional–are removed earlier from euglenids’ pre-mRNA. To track this process we analyzed transcripts of the two Euglena gracilis genes. The relative order of intron excision was compared for pairs of introns belonging to different types. We also surveyed thousands of intermediate products of splicing using the Next-Generation Sequencing system. Summarizing the results of both experiments, we proved that spliceosomal introns are removed at an earlier stage of pre-mRNA maturation than nonconventional ones.
Collapse
|
9
|
Ebenezer TE, Carrington M, Lebert M, Kelly S, Field MC. Euglena gracilis Genome and Transcriptome: Organelles, Nuclear Genome Assembly Strategies and Initial Features. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 979:125-140. [PMID: 28429320 DOI: 10.1007/978-3-319-54910-1_7] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Euglena gracilis is a major component of the aquatic ecosystem and together with closely related species, is ubiquitous worldwide. Euglenoids are an important group of protists, possessing a secondarily acquired plastid and are relatives to the Kinetoplastidae, which themselves have global impact as disease agents. To understand the biology of E. gracilis, as well as to provide further insight into the evolution and origins of the Kinetoplastidae, we embarked on sequencing the nuclear genome; the plastid and mitochondrial genomes are already in the public domain. Earlier studies suggested an extensive nuclear DNA content, with likely a high degree of repetitive sequence, together with significant extrachromosomal elements. To produce a list of coding sequences we have combined transcriptome data from both published and new sources, as well as embarked on de novo sequencing using a combination of 454, Illumina paired end libraries and long PacBio reads. Preliminary analysis suggests a surprisingly large genome approaching 2 Gbp, with a highly fragmented architecture and extensive repeat composition. Over 80% of the RNAseq reads from E. gracilis maps to the assembled genome sequence, which is comparable with the well assembled genomes of T. brucei and T. cruzi. In order to achieve this level of assembly we employed multiple informatics pipelines, which are discussed here. Finally, as a preliminary view of the genome architecture, we discuss the tubulin and calmodulin genes, which highlight potential novel splicing mechanisms.
Collapse
Affiliation(s)
- ThankGod Echezona Ebenezer
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QW, UK.,School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Mark Carrington
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QW, UK
| | - Michael Lebert
- Cell Biology Division, Department of Biology, University of Erlangen-Nuremberg, Staudtstraβe 5, Erlangen, 91058, Germany
| | - Steven Kelly
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
| | - Mark C Field
- School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK.
| |
Collapse
|
10
|
Morphological Identification and Single-Cell Genomics of Marine Diplonemids. Curr Biol 2016; 26:3053-3059. [DOI: 10.1016/j.cub.2016.09.013] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 08/25/2016] [Accepted: 09/07/2016] [Indexed: 11/19/2022]
|
11
|
Hadariová L, Vesteg M, Birčák E, Schwartzbach SD, Krajčovič J. An intact plastid genome is essential for the survival of colorless Euglena longa but not Euglena gracilis. Curr Genet 2016; 63:331-341. [PMID: 27553633 DOI: 10.1007/s00294-016-0641-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 08/02/2016] [Accepted: 08/13/2016] [Indexed: 12/18/2022]
Abstract
Euglena gracilis growth with antibacterial agents leads to bleaching, permanent plastid gene loss. Colorless Euglena (Astasia) longa resembles a bleached E. gracilis. To evaluate the role of bleaching in E. longa evolution, the effect of streptomycin, a plastid protein synthesis inhibitor, and ofloxacin, a plastid DNA gyrase inhibitor, on E. gracilis and E. longa growth and plastid DNA content were compared. E. gracilis growth was unaffected by streptomycin and ofloxacin. Quantitative PCR analyses revealed a time dependent loss of plastid genes in E. gracilis demonstrating that bleaching agents produce plastid gene deletions without affecting cell growth. Streptomycin and ofloxacin inhibited E. longa growth indicating that it requires plastid genes to survive. This suggests that evolutionary divergence of E. longa from E. gracilis was triggered by the loss of a cytoplasmic metabolic activity also occurring in the plastid. Plastid metabolism has become obligatory for E. longa cell growth. A process termed "intermittent bleaching", short term exposure to subsaturating concentrations of reversible bleaching agents followed by growth in the absence of a bleaching agent, is proposed as the molecular mechanism for E. longa plastid genome reduction. Various non-photosynthetic lineages could have independently arisen from their photosynthetic ancestors via a similar process.
Collapse
Affiliation(s)
- Lucia Hadariová
- Department of Genetics, Faculty of Natural Sciences, Comenius University, Mlynská dolina G-1, 842 15, Bratislava, Slovak Republic
| | - Matej Vesteg
- Department of Biology and Ecology, Faculty of Natural Sciences, Matej Bel University, 974 01, Banská Bystrica, Slovakia
| | - Erik Birčák
- Department of Genetics, Faculty of Natural Sciences, Comenius University, Mlynská dolina G-1, 842 15, Bratislava, Slovak Republic
| | | | - Juraj Krajčovič
- Department of Genetics, Faculty of Natural Sciences, Comenius University, Mlynská dolina G-1, 842 15, Bratislava, Slovak Republic. .,Department of Biology, Faculty of Natural Sciences, University of ss. Cyril and Methodius, 917 01, Trnava, Slovakia.
| |
Collapse
|
12
|
Bicudo CEDM, Menezes M. Phylogeny and Classification of Euglenophyceae: A Brief Review. Front Ecol Evol 2016. [DOI: 10.3389/fevo.2016.00017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
13
|
Milanowski R, Gumińska N, Karnkowska A, Ishikawa T, Zakryś B. Intermediate introns in nuclear genes of euglenids - are they a distinct type? BMC Evol Biol 2016; 16:49. [PMID: 26923034 PMCID: PMC4770533 DOI: 10.1186/s12862-016-0620-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 02/15/2016] [Indexed: 02/05/2023] Open
Abstract
Background Nuclear genes of euglenids contain two major types of introns: conventional spliceosomal and nonconventional introns. The latter are characterized by variable non-canonical borders, RNA secondary structure that brings intron ends together, and an unknown mechanism of removal. Some researchers also distinguish intermediate introns, which combine features of both types. They form a stable RNA secondary structure and are classified into two subtypes depending on whether they contain one (intermediate/nonconventional subtype) or both (conventional/intermediate subtype) canonical spliceosomal borders. However, it has been also postulated that most introns classified as intermediate could simply be special cases of conventional or nonconventional introns. Results Sequences of tubB, hsp90 and gapC genes from six strains of Euglena agilis were obtained. They contain four, six, and two or three introns, respectively (the third intron in the gapC gene is unique for just one strain). Conventional introns were present at three positions: two in the tubB gene (at one position conventional/intermediate introns were also found) and one in the gapC gene. Nonconventional introns are present at ten positions: two in the tubB gene (at one position intermediate/nonconventional introns were also found), six in hsp90 (at four positions intermediate/nonconventional introns were also found), and two in the gapC gene. Conclusions Sequence and RNA secondary structure analyses of nonconventional introns confirmed that their most strongly conserved elements are base pairing nucleotides at positions +4, +5 and +6/ -8, −7 and −6 (in most introns CAG/CTG nucleotides were observed). It was also confirmed that the presence of the 5' GT/C end in intermediate/nonconventional introns is not the result of kinship with conventional introns, but is due to evolutionary pressure to preserve the purine at the 5' end. However, an example of a nonconventional intron with GC-AG ends was shown, suggesting the possibility of intron type conversion between nonconventional and conventional. Furthermore, an analysis of conventional introns revealed that the ability to form a stable RNA secondary structure by some introns is probably not a result of their relationship with nonconventional introns. It was also shown that acquisition of new nonconventional introns is an ongoing process and can be observed at the level of a single species. In the recently acquired intron in the gapC gene an extended direct repeats at the intron-exon junctions are present, suggesting that double-strand break repair process could be the source of new nonconventional introns. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0620-5) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Rafał Milanowski
- Department of Molecular Phylogenetics and Evolution, Institute of Botany, Faculty of Biology, University of Warsaw, Warsaw, Poland.
| | - Natalia Gumińska
- Department of Molecular Phylogenetics and Evolution, Institute of Botany, Faculty of Biology, University of Warsaw, Warsaw, Poland.
| | - Anna Karnkowska
- Department of Molecular Phylogenetics and Evolution, Institute of Botany, Faculty of Biology, University of Warsaw, Warsaw, Poland. .,Department of Botany, University of British Columbia, Vancouver, Canada.
| | - Takao Ishikawa
- Department of Molecular Biology, Institute of Biochemistry, Faculty of Biology, University of Warsaw, Warsaw, Poland.
| | - Bożena Zakryś
- Department of Molecular Phylogenetics and Evolution, Institute of Botany, Faculty of Biology, University of Warsaw, Warsaw, Poland.
| |
Collapse
|
14
|
Piégu B, Bire S, Arensburger P, Bigot Y. A survey of transposable element classification systems--a call for a fundamental update to meet the challenge of their diversity and complexity. Mol Phylogenet Evol 2015; 86:90-109. [PMID: 25797922 DOI: 10.1016/j.ympev.2015.03.009] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 03/11/2015] [Accepted: 03/12/2015] [Indexed: 10/25/2022]
Abstract
The increase of publicly available sequencing data has allowed for rapid progress in our understanding of genome composition. As new information becomes available we should constantly be updating and reanalyzing existing and newly acquired data. In this report we focus on transposable elements (TEs) which make up a significant portion of nearly all sequenced genomes. Our ability to accurately identify and classify these sequences is critical to understanding their impact on host genomes. At the same time, as we demonstrate in this report, problems with existing classification schemes have led to significant misunderstandings of the evolution of both TE sequences and their host genomes. In a pioneering publication Finnegan (1989) proposed classifying all TE sequences into two classes based on transposition mechanisms and structural features: the retrotransposons (class I) and the DNA transposons (class II). We have retraced how ideas regarding TE classification and annotation in both prokaryotic and eukaryotic scientific communities have changed over time. This has led us to observe that: (1) a number of TEs have convergent structural features and/or transposition mechanisms that have led to misleading conclusions regarding their classification, (2) the evolution of TEs is similar to that of viruses by having several unrelated origins, (3) there might be at least 8 classes and 12 orders of TEs including 10 novel orders. In an effort to address these classification issues we propose: (1) the outline of a universal TE classification, (2) a set of methods and classification rules that could be used by all scientific communities involved in the study of TEs, and (3) a 5-year schedule for the establishment of an International Committee for Taxonomy of Transposable Elements (ICTTE).
Collapse
Affiliation(s)
- Benoît Piégu
- UMR INRA-CNRS 7247, PRC, Centre INRA de Nouzilly, 37380 Nouzilly, France
| | - Solenne Bire
- UMR INRA-CNRS 7247, PRC, Centre INRA de Nouzilly, 37380 Nouzilly, France; Institute of Biotechnology, University of Lausanne, Center for Biotechnology UNIL-EPFL, 1015 Lausanne, Switzerland
| | - Peter Arensburger
- UMR INRA-CNRS 7247, PRC, Centre INRA de Nouzilly, 37380 Nouzilly, France; Biological Sciences Department, California State Polytechnic University, Pomona, CA 91768, United States.
| | - Yves Bigot
- UMR INRA-CNRS 7247, PRC, Centre INRA de Nouzilly, 37380 Nouzilly, France.
| |
Collapse
|