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Williams SK, Jerlström Hultqvist J, Eglit Y, Salas-Leiva DE, Curtis B, Orr RJS, Stairs CW, Atalay TN, MacMillan N, Simpson AGB, Roger AJ. Extreme mitochondrial reduction in a novel group of free-living metamonads. Nat Commun 2024; 15:6805. [PMID: 39122691 DOI: 10.1038/s41467-024-50991-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 07/15/2024] [Indexed: 08/12/2024] Open
Abstract
Metamonads are a diverse group of heterotrophic microbial eukaryotes adapted to living in hypoxic environments. All metamonads but one harbour metabolically altered 'mitochondrion-related organelles' (MROs) with reduced functions, however the degree of reduction varies. Here, we generate high-quality draft genomes, transcriptomes, and predicted proteomes for five recently discovered free-living metamonads. Phylogenomic analyses placed these organisms in a group we name the 'BaSk' (Barthelonids+Skoliomonads) clade, a deeply branching sister group to the Fornicata, a phylum that includes parasitic and free-living flagellates. Bioinformatic analyses of gene models shows that these organisms are predicted to have extremely reduced MRO proteomes in comparison to other free-living metamonads. Loss of the mitochondrial iron-sulfur cluster assembly system in some organisms in this group appears to be linked to the acquisition in their common ancestral lineage of a SUF-like minimal system Fe/S cluster pathway by lateral gene transfer. One of the isolates, Skoliomonas litria, appears to have lost all other known MRO pathways. No proteins were confidently assigned to the predicted MRO proteome of this organism suggesting that the organelle has been lost. The extreme mitochondrial reduction observed within this free-living anaerobic protistan clade demonstrates that mitochondrial functions may be completely lost even in free-living organisms.
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Affiliation(s)
- Shelby K Williams
- Institute for Comparative Genomics, Dalhousie University, Halifax, NS, Canada
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada
| | - Jon Jerlström Hultqvist
- Institute for Comparative Genomics, Dalhousie University, Halifax, NS, Canada
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Yana Eglit
- Institute for Comparative Genomics, Dalhousie University, Halifax, NS, Canada
- Department of Biology, Dalhousie University, Halifax, Canada
| | - Dayana E Salas-Leiva
- Institute for Comparative Genomics, Dalhousie University, Halifax, NS, Canada
- Department of Biochemistry, Cambridge University, Cambridge, UK
| | - Bruce Curtis
- Institute for Comparative Genomics, Dalhousie University, Halifax, NS, Canada
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada
| | - Russell J S Orr
- Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, Oslo, Norway
| | | | - Tuğba N Atalay
- Institute for Comparative Genomics, Dalhousie University, Halifax, NS, Canada
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada
| | - Naomi MacMillan
- Institute for Comparative Genomics, Dalhousie University, Halifax, NS, Canada
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada
| | - Alastair G B Simpson
- Institute for Comparative Genomics, Dalhousie University, Halifax, NS, Canada
- Department of Biology, Dalhousie University, Halifax, Canada
| | - Andrew J Roger
- Institute for Comparative Genomics, Dalhousie University, Halifax, NS, Canada.
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada.
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Keeling PJ. Horizontal gene transfer in eukaryotes: aligning theory with data. Nat Rev Genet 2024; 25:416-430. [PMID: 38263430 DOI: 10.1038/s41576-023-00688-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/06/2023] [Indexed: 01/25/2024]
Abstract
Horizontal gene transfer (HGT), or lateral gene transfer, is the non-sexual movement of genetic information between genomes. It has played a pronounced part in bacterial and archaeal evolution, but its role in eukaryotes is less clear. Behaviours unique to eukaryotic cells - phagocytosis and endosymbiosis - have been proposed to increase the frequency of HGT, but nuclear genomes encode fewer HGTs than bacteria and archaea. Here, I review the existing theory in the context of the growing body of data on HGT in eukaryotes, which suggests that any increased chance of acquiring new genes through phagocytosis and endosymbiosis is offset by a reduced need for these genes in eukaryotes, because selection in most eukaryotes operates on variation not readily generated by HGT.
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Affiliation(s)
- Patrick J Keeling
- Department of Botany, University of British Columbia, Vancouver, BC, Canada.
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The Genome of the Mitochondrion-Related Organelle in Cepedea longa, a Large Endosymbiotic Opalinid Inhabiting the Recta of Frogs. Int J Mol Sci 2022; 23:ijms232113472. [DOI: 10.3390/ijms232113472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 10/13/2022] [Accepted: 11/01/2022] [Indexed: 11/06/2022] Open
Abstract
Mitochondrion-related organelles (MROs) are loosely defined as degenerated mitochondria in anaerobic and microaerophilic lineages. Opalinids are commonly regarded as commensals in the guts of cold-blooded amphibians. It may represent an intermediate adaptation stage between the conventional aerobic mitochondria and derived anaerobic MROs. In the present study, we sequenced and analyzed the MRO genome of Cepedea longa. It has a linear MRO genome with large inverted repeat gene regions at both ends. Compared to Blastocystis and Proteromonas lacertae, the MRO genome of C. longa has a higher G + C content and repeat sequences near the central region. Although three Opalinata species have different morphological characteristics, phylogenetic analyses based on eight concatenated nad genes indicate that they are close relatives. The phylogenetic analysis showed that C. longa clustered with P. lacertae with strong support. The 18S rRNA gene-based phylogeny resolved the Opalinea clade as a sister clade to Karotomorpha, which then further grouped with Proteromonas. The paraphyly of Proteromonadea needs to be verified due to the lack of MRO genomes for key species, such as Karotomorpha, Opalina and Protoopalina. Besides, our dataset and analyses offered slight support for the paraphyly of Bigyra.
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Cornet L, Baurain D. Contamination detection in genomic data: more is not enough. Genome Biol 2022; 23:60. [PMID: 35189924 PMCID: PMC8862208 DOI: 10.1186/s13059-022-02619-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 01/18/2022] [Indexed: 12/20/2022] Open
Abstract
The decreasing cost of sequencing and concomitant augmentation of publicly available genomes have created an acute need for automated software to assess genomic contamination. During the last 6 years, 18 programs have been published, each with its own strengths and weaknesses. Deciding which tools to use becomes more and more difficult without an understanding of the underlying algorithms. We review these programs, benchmarking six of them, and present their main operating principles. This article is intended to guide researchers in the selection of appropriate tools for specific applications. Finally, we present future challenges in the developing field of contamination detection.
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Affiliation(s)
- Luc Cornet
- BCCM/IHEM, Mycology and Aerobiology, Sciensano, Bruxelles, Belgium
| | - Denis Baurain
- InBioS-PhytoSYSTEMS, Eukaryotic Phylogenomics, University of Liège, Liège, Belgium.
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Gawryluk RMR, Stairs CW. Diversity of electron transport chains in anaerobic protists. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1862:148334. [PMID: 33159845 DOI: 10.1016/j.bbabio.2020.148334] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 10/21/2020] [Accepted: 10/30/2020] [Indexed: 01/06/2023]
Abstract
Eukaryotic microbes (protists) that occupy low-oxygen environments often have drastically different mitochondrial metabolism compared to their aerobic relatives. A common theme among many anaerobic protists is the serial loss of components of the electron transport chain (ETC). Here, we discuss the diversity of the ETC across the tree of eukaryotes and review hypotheses for how ETCs are modified, and ultimately lost, in protists. We find that while protists have converged to some of the same metabolism as anaerobic animals, there are clear protist-specific strategies to thrive without oxygen.
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Affiliation(s)
- Ryan M R Gawryluk
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada
| | - Courtney W Stairs
- Department of Biology, Lund University, Sölvegatan 35, 223 62 Lund, Sweden; Department of Cell and Molecular Biology, Science for Life Laboratory, Uppsala University, SE-75123 Uppsala, Sweden.
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Roberts WR, Downey KM, Ruck EC, Traller JC, Alverson AJ. Improved Reference Genome for Cyclotella cryptica CCMP332, a Model for Cell Wall Morphogenesis, Salinity Adaptation, and Lipid Production in Diatoms (Bacillariophyta). G3 (BETHESDA, MD.) 2020; 10:2965-2974. [PMID: 32709619 PMCID: PMC7466962 DOI: 10.1534/g3.120.401408] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 07/22/2020] [Indexed: 01/13/2023]
Abstract
The diatom, Cyclotella cryptica, is a well-established model species for physiological studies and biotechnology applications of diatoms. To further facilitate its use as a model diatom, we report an improved reference genome assembly and annotation for C. cryptica strain CCMP332. We used a combination of long- and short-read sequencing to assemble a high-quality and contaminant-free genome. The genome is 171 Mb in size and consists of 662 scaffolds with a scaffold N50 of 494 kb. This represents a 176-fold decrease in scaffold number and 41-fold increase in scaffold N50 compared to the previous assembly. The genome contains 21,250 predicted genes, 75% of which were assigned putative functions. Repetitive DNA comprises 59% of the genome, and an improved classification of repetitive elements indicated that a historically steady accumulation of transposable elements has contributed to the relatively large size of the C. cryptica genome. The high-quality C. cryptica genome will serve as a valuable reference for ecological, genetic, and biotechnology studies of diatoms.
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Affiliation(s)
- Wade R Roberts
- University of Arkansas, Department of Biological Sciences, Fayetteville, AR 72701
| | - Kala M Downey
- University of Arkansas, Department of Biological Sciences, Fayetteville, AR 72701
| | - Elizabeth C Ruck
- University of Arkansas, Department of Biological Sciences, Fayetteville, AR 72701
| | | | - Andrew J Alverson
- University of Arkansas, Department of Biological Sciences, Fayetteville, AR 72701
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