301
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Tsaousis AD, Gaston D, Stechmann A, Walker PB, Lithgow T, Roger AJ. A functional Tom70 in the human parasite Blastocystis sp.: implications for the evolution of the mitochondrial import apparatus. Mol Biol Evol 2010; 28:781-91. [PMID: 20871025 DOI: 10.1093/molbev/msq252] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Core proteins of mitochondrial protein import are found in all mitochondria, suggesting a common origin of this import machinery. Despite the presence of a universal core import mechanism, there are specific proteins found only in a few groups of organisms. One of these proteins is the translocase of outer membrane 70 (Tom70), a protein that is essential for the import of preproteins with internal targeting sequences into the mitochondrion. Until now, Tom70 has only been found in animals and Fungi. We have identified a tom70 gene in the human parasitic anaerobic stramenopile Blastocystis sp. that is neither an animal nor a fungus. Using a combination of bioinformatics, genetic complementation, and immunofluorescence microscopy analyses, we demonstrate that this protein functions as a typical Tom70 in Blastocystis mitochondrion-related organelles. Additionally, we identified putative tom70 genes in the genomes of other stramenopiles and a haptophyte, that, in phylogenies, form a monophyletic group distinct from the animal and the fungal homologues. The presence of Tom70 in these lineages significantly expands the evolutionary spectrum of eukaryotes that contain this protein and suggests that it may have been part of the core mitochondrial protein import apparatus of the last common ancestral eukaryote.
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Affiliation(s)
- Anastasios D Tsaousis
- Department of Biochemistry and Molecular Biology, Centre for Comparative Genomics and Evolutionary Bioinformatics, Dalhousie University, Halifax, Canada.
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302
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Worden AZ, Allen AE. The voyage of the microbial eukaryote. Curr Opin Microbiol 2010; 13:652-60. [PMID: 20832353 DOI: 10.1016/j.mib.2010.08.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Accepted: 08/03/2010] [Indexed: 01/01/2023]
Abstract
Although genome data from unicellular marine eukaryotes is sparse, sequences from several supergroups have initiated an era of genome-enabled research aimed at understanding gene function, evolution, and adaptation in non-traditional model protists. Trends in genomic content within and between different lineages are emerging, including phylogenetically anomalous patterns, sometimes resulting from horizontal gene transfer. Some such genes have nutrient uptake and metabolism roles suggesting that bacterial and eukaryotic microbes have similar cellular-mineral-environmental constraints. Many 'accessory genome' components are of unknown function, but low gene copy numbers combined with small genomes make protists ideal for systems biology. Cultured and uncultured protists are providing insights to ecology, ancestral features and the role of cooption in development of complex traits. Various protists harbor features important in sexuality and multicellularity once believed to have originated in metazoans or other multicellular taxa.
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Affiliation(s)
- Alexandra Z Worden
- Monterey Bay Aquarium Research Institute, 7700 Sandholdt Rd., Moss Landing, CA 95039, USA.
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303
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Kamikawa R, Sakaguchi M, Matsumoto T, Hashimoto T, Inagaki Y. Rooting for the root of elongation factor-like protein phylogeny. Mol Phylogenet Evol 2010; 56:1082-8. [DOI: 10.1016/j.ympev.2010.04.040] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Revised: 04/26/2010] [Accepted: 04/26/2010] [Indexed: 11/29/2022]
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304
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Targeted metagenomics and ecology of globally important uncultured eukaryotic phytoplankton. Proc Natl Acad Sci U S A 2010; 107:14679-84. [PMID: 20668244 DOI: 10.1073/pnas.1001665107] [Citation(s) in RCA: 159] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Among eukaryotes, four major phytoplankton lineages are responsible for marine photosynthesis; prymnesiophytes, alveolates, stramenopiles, and prasinophytes. Contributions by individual taxa, however, are not well known, and genomes have been analyzed from only the latter two lineages. Tiny "picoplanktonic" members of the prymnesiophyte lineage have long been inferred to be ecologically important but remain poorly characterized. Here, we examine pico-prymnesiophyte evolutionary history and ecology using cultivation-independent methods. 18S rRNA gene analysis showed pico-prymnesiophytes belonged to broadly distributed uncultivated taxa. Therefore, we used targeted metagenomics to analyze uncultured pico-prymnesiophytes sorted by flow cytometry from subtropical North Atlantic waters. The data reveal a composite nuclear-encoded gene repertoire with strong green-lineage affiliations, which contrasts with the evolutionary history indicated by the plastid genome. Measured pico-prymnesiophyte growth rates were rapid in this region, resulting in primary production contributions similar to the cyanobacterium Prochlorococcus. On average, pico-prymnesiophytes formed 25% of global picophytoplankton biomass, with differing contributions in five biogeographical provinces spanning tropical to subpolar systems. Elements likely contributing to success include high gene density and genes potentially involved in defense and nutrient uptake. Our findings have implications reaching beyond pico-prymnesiophytes, to the prasinophytes and stramenopiles. For example, prevalence of putative Ni-containing superoxide dismutases (SODs), instead of Fe-containing SODs, seems to be a common adaptation among eukaryotic phytoplankton for reducing Fe quotas in low-Fe modern oceans. Moreover, highly mosaic gene repertoires, although compositionally distinct for each major eukaryotic lineage, now seem to be an underlying facet of successful marine phytoplankton.
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305
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Parfrey LW, Grant J, Tekle YI, Lasek-Nesselquist E, Morrison HG, Sogin ML, Patterson DJ, Katz LA. Broadly sampled multigene analyses yield a well-resolved eukaryotic tree of life. Syst Biol 2010; 59:518-33. [PMID: 20656852 DOI: 10.1093/sysbio/syq037] [Citation(s) in RCA: 157] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
An accurate reconstruction of the eukaryotic tree of life is essential to identify the innovations underlying the diversity of microbial and macroscopic (e.g., plants and animals) eukaryotes. Previous work has divided eukaryotic diversity into a small number of high-level "supergroups," many of which receive strong support in phylogenomic analyses. However, the abundance of data in phylogenomic analyses can lead to highly supported but incorrect relationships due to systematic phylogenetic error. Furthermore, the paucity of major eukaryotic lineages (19 or fewer) included in these genomic studies may exaggerate systematic error and reduce power to evaluate hypotheses. Here, we use a taxon-rich strategy to assess eukaryotic relationships. We show that analyses emphasizing broad taxonomic sampling (up to 451 taxa representing 72 major lineages) combined with a moderate number of genes yield a well-resolved eukaryotic tree of life. The consistency across analyses with varying numbers of taxa (88-451) and levels of missing data (17-69%) supports the accuracy of the resulting topologies. The resulting stable topology emerges without the removal of rapidly evolving genes or taxa, a practice common to phylogenomic analyses. Several major groups are stable and strongly supported in these analyses (e.g., SAR, Rhizaria, Excavata), whereas the proposed supergroup "Chromalveolata" is rejected. Furthermore, extensive instability among photosynthetic lineages suggests the presence of systematic biases including endosymbiotic gene transfer from symbiont (nucleus or plastid) to host. Our analyses demonstrate that stable topologies of ancient evolutionary relationships can be achieved with broad taxonomic sampling and a moderate number of genes. Finally, taxon-rich analyses such as presented here provide a method for testing the accuracy of relationships that receive high bootstrap support (BS) in phylogenomic analyses and enable placement of the multitude of lineages that lack genome scale data.
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Affiliation(s)
- Laura Wegener Parfrey
- Program in Organismic and Evolutionary Biology, University of Massachusetts, 611 North Pleasant Street, Amherst, MA 01003, USA
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306
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A metazoan/plant-like capping enzyme and cap modified nucleotides in the unicellular eukaryote Trichomonas vaginalis. PLoS Pathog 2010; 6:e1000999. [PMID: 20664792 PMCID: PMC2904801 DOI: 10.1371/journal.ppat.1000999] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2009] [Accepted: 06/11/2010] [Indexed: 01/12/2023] Open
Abstract
The cap structure of eukaryotic messenger RNAs is initially elaborated through three enzymatic reactions: hydrolysis of the 5′-triphosphate, transfer of guanosine through a 5′-5′ triphosphate linkage and N7-methylation of the guanine cap. Three distinctive enzymes catalyze each reaction in various microbial eukaryotes, whereas the first two enzymes are fused into a single polypeptide in metazoans and plants. In addition to the guanosine cap, adjacent nucleotides are 2′-O-ribose methylated in metazoa and plants, but not in yeast. Analyses of various cap structures have suggested a linear phylogenetic trend of complexity. These findings have led to a model in which plants and metazoa evolved a two-component capping apparatus and modification of adjacent nucleotides while many microbial eukaryotes maintained the three-component system and did not develop modification of adjacent nucleotides. Here, we have characterized a bifunctional capping enzyme in the divergent microbial eukaryote Trichomonas vaginalis using biochemical and phylogenetic analyses. This unicellular parasite was found to harbor a metazoan/plant-like capping apparatus that is represented by a two-domain polypeptide containing a C-terminus guanylyltransferase and a cysteinyl phosphatase triphosphatase, distinct from its counterpart in other microbial eukaryotes. In addition, T. vaginalis mRNAs contain a cap 1 structure represented by m7GpppAmpUp or m7GpppCmpUp; a feature typical of metazoan and plant mRNAs but absent in yeast mRNAs. Phylogenetic and biochemical analyses of the origin of the T. vaginalis capping enzyme suggests a complex evolutionary model where differential gene loss and/or acquisition occurred in the development of the RNA capping apparatus and cap modified nucleotides during eukaryote diversification. The protozoan parasite Trichomonas vaginalis is the cause of the most common non-viral sexually transmitted disease worldwide. Evolutionary analyses place Trichomonas in a super group called the Excavata, which includes the kinetoplastids and is highly divergent from fungi, metazoa and plants. Despite the vast evolutionary distances that separate these different eukaryotic lineages, a simplified view of eukaryotic evolution based on the complexity of nucleotide modifications at the 5′ end of mRNAs and the distribution of different types of enzymatic apparatus that confer these modifications has been proposed. Our analyses of the T. vaginalis capping enzyme challenges this view and provides the first example of a two-component capping apparatus typically found in metazoa and plants in a protozoan. The 5′-end nucleotide structure of T. vaginalis mRNAs is also shown to contain additional modified nucleotides, similar to that observed for metazoan and plant mRNAs and unlike that found in most eukaryotic microbes and fungi. Evolutionary analyses of the T. vaginalis capping enzyme indicates that this multicellular type capping apparatus may have come into existence earlier than previously thought.
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307
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Sun G, Yang Z, Ishwar A, Huang J. Algal genes in the closest relatives of animals. Mol Biol Evol 2010; 27:2879-89. [PMID: 20627874 DOI: 10.1093/molbev/msq175] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The spread of photosynthesis is one of the most important but controversial topics in eukaryotic evolution. Because of massive gene transfer from plastids to the nucleus and because of the possibility that plastids have been lost in evolution, algal genes in aplastidic organisms often are interpreted as footprints of photosynthetic ancestors. These putative plastid losses, in turn, have been cited as support for scenarios involving the spread of plastids in broadscale eukaryotic evolution. Phylogenomic analyses identified more than 100 genes of possible algal origin in Monosiga, a unicellular species from choanoflagellates, a group considered to be the closest protozoan relatives of animals and to be primitively heterotrophic. The vast majority of these algal genes appear to be derived from haptophytes, diatoms, or green plants. Furthermore, more than 25% of these algal genes are ultimately of prokaryotic origin and were spread secondarily to Monosiga. Our results show that the presence of algal genes may be expected in many phagotrophs or taxa of phagotrophic ancestry and therefore does not necessarily represent evidence of plastid losses. The ultimate prokaryotic origin of some algal genes and their simultaneous presence in both primary and secondary photosynthetic eukaryotes either suggest recurrent gene transfer events under specific environments or support a more ancient origin of primary plastids.
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Affiliation(s)
- Guiling Sun
- Department of Biology, East Carolina University, Greenville, North Carolina, USA
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308
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Criscuolo A, Gribaldo S. BMGE (Block Mapping and Gathering with Entropy): a new software for selection of phylogenetic informative regions from multiple sequence alignments. BMC Evol Biol 2010; 10:210. [PMID: 20626897 PMCID: PMC3017758 DOI: 10.1186/1471-2148-10-210] [Citation(s) in RCA: 872] [Impact Index Per Article: 62.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Accepted: 07/13/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The quality of multiple sequence alignments plays an important role in the accuracy of phylogenetic inference. It has been shown that removing ambiguously aligned regions, but also other sources of bias such as highly variable (saturated) characters, can improve the overall performance of many phylogenetic reconstruction methods. A current scientific trend is to build phylogenetic trees from a large number of sequence datasets (semi-)automatically extracted from numerous complete genomes. Because these approaches do not allow a precise manual curation of each dataset, there exists a real need for efficient bioinformatic tools dedicated to this alignment character trimming step. RESULTS Here is presented a new software, named BMGE (Block Mapping and Gathering with Entropy), that is designed to select regions in a multiple sequence alignment that are suited for phylogenetic inference. For each character, BMGE computes a score closely related to an entropy value. Calculation of these entropy-like scores is weighted with BLOSUM or PAM similarity matrices in order to distinguish among biologically expected and unexpected variability for each aligned character. Sets of contiguous characters with a score above a given threshold are considered as not suited for phylogenetic inference and then removed. Simulation analyses show that the character trimming performed by BMGE produces datasets leading to accurate trees, especially with alignments including distantly-related sequences. BMGE also implements trimming and recoding methods aimed at minimizing phylogeny reconstruction artefacts due to compositional heterogeneity. CONCLUSIONS BMGE is able to perform biologically relevant trimming on a multiple alignment of DNA, codon or amino acid sequences. Java source code and executable are freely available at ftp://ftp.pasteur.fr/pub/GenSoft/projects/BMGE/.
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Affiliation(s)
- Alexis Criscuolo
- Institut Pasteur, Unité de Biologie Moléculaire du Gène chez les Extrêmophiles, Département de Microbiologie, 25 rue du Dr Roux, 75015 Paris, France
| | - Simonetta Gribaldo
- Institut Pasteur, Unité de Biologie Moléculaire du Gène chez les Extrêmophiles, Département de Microbiologie, 25 rue du Dr Roux, 75015 Paris, France
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309
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Balabaskaran Nina P, Dudkina NV, Kane LA, van Eyk JE, Boekema EJ, Mather MW, Vaidya AB. Highly divergent mitochondrial ATP synthase complexes in Tetrahymena thermophila. PLoS Biol 2010; 8:e1000418. [PMID: 20644710 PMCID: PMC2903591 DOI: 10.1371/journal.pbio.1000418] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Accepted: 06/01/2010] [Indexed: 12/28/2022] Open
Abstract
The F-type ATP synthase complex is a rotary nano-motor driven by proton motive force to synthesize ATP. Its F(1) sector catalyzes ATP synthesis, whereas the F(o) sector conducts the protons and provides a stator for the rotary action of the complex. Components of both F(1) and F(o) sectors are highly conserved across prokaryotes and eukaryotes. Therefore, it was a surprise that genes encoding the a and b subunits as well as other components of the F(o) sector were undetectable in the sequenced genomes of a variety of apicomplexan parasites. While the parasitic existence of these organisms could explain the apparent incomplete nature of ATP synthase in Apicomplexa, genes for these essential components were absent even in Tetrahymena thermophila, a free-living ciliate belonging to a sister clade of Apicomplexa, which demonstrates robust oxidative phosphorylation. This observation raises the possibility that the entire clade of Alveolata may have invented novel means to operate ATP synthase complexes. To assess this remarkable possibility, we have carried out an investigation of the ATP synthase from T. thermophila. Blue native polyacrylamide gel electrophoresis (BN-PAGE) revealed the ATP synthase to be present as a large complex. Structural study based on single particle electron microscopy analysis suggested the complex to be a dimer with several unique structures including an unusually large domain on the intermembrane side of the ATP synthase and novel domains flanking the c subunit rings. The two monomers were in a parallel configuration rather than the angled configuration previously observed in other organisms. Proteomic analyses of well-resolved ATP synthase complexes from 2-D BN/BN-PAGE identified orthologs of seven canonical ATP synthase subunits, and at least 13 novel proteins that constitute subunits apparently limited to the ciliate lineage. A mitochondrially encoded protein, Ymf66, with predicted eight transmembrane domains could be a substitute for the subunit a of the F(o) sector. The absence of genes encoding orthologs of the novel subunits even in apicomplexans suggests that the Tetrahymena ATP synthase, despite core similarities, is a unique enzyme exhibiting dramatic differences compared to the conventional complexes found in metazoan, fungal, and plant mitochondria, as well as in prokaryotes. These findings have significant implications for the origins and evolution of a central player in bioenergetics.
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Affiliation(s)
- Praveen Balabaskaran Nina
- Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Natalya V. Dudkina
- Department of Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands
| | - Lesley A. Kane
- Department of Medicine, The Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Biological Chemistry, The Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Jennifer E. van Eyk
- Department of Medicine, The Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Biological Chemistry, The Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Egbert J. Boekema
- Department of Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands
| | - Michael W. Mather
- Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Akhil B. Vaidya
- Center for Molecular Parasitology, Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America
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310
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Critical Taxonomic Revision of Parabasalids with Description of one New Genus and three New Species. Protist 2010; 161:400-33. [DOI: 10.1016/j.protis.2009.11.005] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Accepted: 11/21/2009] [Indexed: 11/17/2022]
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311
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Serfontein J, Nisbet RER, Howe CJ, de Vries PJ. Evolution of the TSC1/TSC2-TOR signaling pathway. Sci Signal 2010; 3:ra49. [PMID: 20587805 DOI: 10.1126/scisignal.2000803] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The TSC1/TSC2-TOR signaling pathway [the signaling pathway that includes the heterodimeric TSC1 (tuberous sclerosis 1 protein)-TSC2 (tuberous sclerosis 2 protein) complex and TOR (target of rapamycin)] regulates various cellular processes, including protein synthesis, in response to growth factors and nutrient availability. Homologs of some pathway components have been reported from animals, fungi, plants, and protozoa. These observations led to the perception that the whole pathway is evolutionarily conserved throughout eukaryotes. Using complete genome sequences, we show that, contrary to this view, the pathway was built up from a simpler one, present in the ancestral eukaryote, coupling cell growth to energy supplies. Additional elements, such as TSC1 and TSC2, were "bolted on" in particular eukaryotic lineages. Our results also suggest that unikonts [Opisthokonta (including animals and fungi) and Amoebozoa] form a monophyletic group with the Excavata and Chromalveolata. A previous proposal, that the root of the eukaryotic "tree of life" lies between the unikonts and other organisms, should therefore be reevaluated.
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Affiliation(s)
- Jaco Serfontein
- Cambridgeshire and Peterborough NHS Foundation Trust, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK
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312
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Koonin EV, Yutin N. Origin and evolution of eukaryotic large nucleo-cytoplasmic DNA viruses. Intervirology 2010; 53:284-92. [PMID: 20551680 DOI: 10.1159/000312913] [Citation(s) in RCA: 159] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND/AIMS The nucleo-cytoplasmic large DNA viruses (NCLDV) constitute an apparently monophyletic group that consists of 6 families of viruses infecting a broad variety of eukaryotes. A comprehensive genome comparison and maximum-likelihood reconstruction of NCLDV evolution reveal a set of approximately 50 conserved genes that can be tentatively mapped to the genome of the common ancestor of this class of eukaryotic viruses. We address the origins and evolution of NCLDV. RESULTS Phylogenetic analysis indicates that some of the major clades of NCLDV infect diverse animals and protists, suggestive of early radiation of the NCLDV, possibly concomitant with eukaryogenesis. The core NCLDV genes seem to have originated from different sources including homologous genes of bacteriophages, bacteria and eukaryotes. These observations are compatible with a scenario of the origin of the NCLDV at an early stage of the evolution of eukaryotes through extensive mixing of genes from widely different genomes. CONCLUSIONS The common ancestor of the NCLDV probably evolved from a bacteriophage as a result of recruitment of numerous eukaryotic and some bacterial genes, and concomitant loss of the majority of phage genes except for a small core of genes coding for proteins essential for virus genome replication and virion formation.
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Affiliation(s)
- Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA.
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313
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Cavalier-Smith T, Chao EE. Phylogeny and evolution of apusomonadida (protozoa: apusozoa): new genera and species. Protist 2010; 161:549-76. [PMID: 20537943 DOI: 10.1016/j.protis.2010.04.002] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2009] [Accepted: 03/20/2010] [Indexed: 11/25/2022]
Abstract
Apusomonadida (Apusomonas; Amastigomonas) are understudied gliding zooflagellates. We divide Amastigomonas into five genera, three new: Podomonas; Manchomonas; Multimonas. Microscopy and 18S rDNA sequences establish three new marine species (Podomonas magna; P. capensis; Multimonas media) and a new cyst-forming non-marine species from the surface of ivy leaves (Thecamonas oxoniensis). We consider the soil and freshwater Amastigomonas debruynei, caudata, and borokensis generically distinct from marine Thecamonas. We establish the new combination Multimonas marina (formerly Cercomonas or Amastigomonas). We studied by DIC microscopy and 18S rDNA sequencing three strains microscopically indistinguishable from marine Thecamonas trahens and argue that marine strains of almost identical sequence and appearance (visible largely acronematic cilia) were previously misidentified as Am. debruynei. We argue that 'Amastigomonas sp.' ATCC50062, whose 18S rRNA was sequenced previously and whose complete genome is being sequenced, is T. trahens. We include electron micrographs of T. aff. trahens, P. capensis and magna; ultrastructural cytoskeletal differences between P. capensis, Thecamonas, and Manchomonas (=Amastigomonas) bermudensis comb. n. allow novel functional interpretations of apusomonad evolution. On 18S rDNA trees Apusomonas and Manchomonas form a robust clade (Apusomonadinae), but Thecomonas trahens, T. oxoniensis, Multimonas, and Podomonas all branch deeply but unstably. Apusomonadida and Planomonas are weakly sister to opisthokonts.
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314
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BROWN MATTHEWW, SILBERMAN JEFFREYD, SPIEGEL FREDERICKW. A Morphologically Simple Species of Acrasis (Heterolobosea, Excavata), Acrasis helenhemmesae n. sp. J Eukaryot Microbiol 2010; 57:346-53. [DOI: 10.1111/j.1550-7408.2010.00481.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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315
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Abstract
Phylogenomics of eukaryote supergroups suggest a highly complex last common ancestor of eukaryotes and a key role of mitochondrial endosymbiosis in the origin of eukaryotes.
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Affiliation(s)
- Eugene V Koonin
- National Center for Biotechnology Information, National Institutes of Health, Bethesda, MD 20894, USA.
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316
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Wickstead B, Gull K, Richards TA. Patterns of kinesin evolution reveal a complex ancestral eukaryote with a multifunctional cytoskeleton. BMC Evol Biol 2010; 10:110. [PMID: 20423470 PMCID: PMC2867816 DOI: 10.1186/1471-2148-10-110] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Accepted: 04/27/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The genesis of the eukaryotes was a pivotal event in evolution and was accompanied by the acquisition of numerous new cellular features including compartmentalization by cytoplasmic organelles, mitosis and meiosis, and ciliary motility. Essential for the development of these features was the tubulin cytoskeleton and associated motors. It is therefore possible to map ancient cell evolution by reconstructing the evolutionary history of motor proteins. Here, we have used the kinesin motor repertoire of 45 extant eukaryotes to infer the ancestral state of this superfamily in the last common eukaryotic ancestor (LCEA). RESULTS We bioinformatically identified 1624 putative kinesin proteins, determined their protein domain architectures and calculated a comprehensive Bayesian phylogeny for the kinesin superfamily with statistical support. These data enabled us to define 51 anciently-derived kinesin paralogs (including three new kinesin families) and 105 domain architectures. We then mapped these characters across eukaryotes, accounting for secondary loss within established eukaryotic groupings, and alternative tree topologies. CONCLUSIONS We show that a minimum of 11 kinesin families and 3 protein domain architectures were present in the LCEA. This demonstrates that the microtubule-based cytoskeleton of the LCEA was surprisingly highly developed in terms of kinesin motor types, but that domain architectures have been extensively modified during the diversification of the eukaryotes. Our analysis provides molecular evidence for the existence of several key cellular functions in the LCEA, and shows that a large proportion of motor family diversity and cellular complexity had already arisen in this ancient cell.
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317
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Ginger ML, McFadden GI, Michels PAM. Rewiring and regulation of cross-compartmentalized metabolism in protists. Philos Trans R Soc Lond B Biol Sci 2010; 365:831-45. [PMID: 20124348 DOI: 10.1098/rstb.2009.0259] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Plastid acquisition, endosymbiotic associations, lateral gene transfer, organelle degeneracy or even organelle loss influence metabolic capabilities in many different protists. Thus, metabolic diversity is sculpted through the gain of new metabolic functions and moderation or loss of pathways that are often essential in the majority of eukaryotes. What is perhaps less apparent to the casual observer is that the sub-compartmentalization of ubiquitous pathways has been repeatedly remodelled during eukaryotic evolution, and the textbook pictures of intermediary metabolism established for animals, yeast and plants are not conserved in many protists. Moreover, metabolic remodelling can strongly influence the regulatory mechanisms that control carbon flux through the major metabolic pathways. Here, we provide an overview of how core metabolism has been reorganized in various unicellular eukaryotes, focusing in particular on one near universal catabolic pathway (glycolysis) and one ancient anabolic pathway (isoprenoid biosynthesis). For the example of isoprenoid biosynthesis, the compartmentalization of this process in protists often appears to have been influenced by plastid acquisition and loss, whereas for glycolysis several unexpected modes of compartmentalization have emerged. Significantly, the example of trypanosomatid glycolysis illustrates nicely how mathematical modelling and systems biology can be used to uncover or understand novel modes of pathway regulation.
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Affiliation(s)
- Michael L Ginger
- Division of Biomedical and Life Sciences, School of Health and Medicine, Lancaster University, Lancaster LA1 4YQ, UK.
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318
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Ginger ML, McFadden GI, Michels PAM. The evolution of organellar metabolism in unicellular eukaryotes. Philos Trans R Soc Lond B Biol Sci 2010; 365:693-8. [PMID: 20124338 DOI: 10.1098/rstb.2009.0260] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Metabolic innovation has facilitated the radiation of microbes into almost every niche environment on the Earth, and over geological time scales transformed the planet on which we live. A notable example of innovation is the evolution of oxygenic photosynthesis which was a prelude to the gradual transformation of an anoxic Earth into a world with oxygenated oceans and an oxygen-rich atmosphere capable of supporting complex multicellular organisms. The influence of microbial innovation on the Earth's history and the timing of pivotal events have been addressed in other recent themed editions of Philosophical Transactions of Royal Society B (Cavalier-Smith et al. 2006; Bendall et al. 2008). In this issue, our contributors provide a timely history of metabolic innovation and adaptation within unicellular eukaryotes. In eukaryotes, diverse metabolic portfolios are compartmentalized across multiple membrane-bounded compartments (or organelles). However, as a consequence of pathway retargeting, organelle degeneration or novel endosymbiotic associations, the metabolic repertoires of protists often differ extensively from classic textbook descriptions of intermediary metabolism. These differences are often important in the context of niche adaptation or the structure of microbial communities. Fundamentally interesting in its own right, the biochemical, cell biological and phylogenomic investigation of organellar metabolism also has wider relevance. For instance, in some pathogens, notably those causing some of the most significant tropical diseases, including malaria, unusual organellar metabolism provides important new drug targets. Moreover, the study of organellar metabolism in protists continues to provide critical insight into our understanding of eukaryotic evolution.
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Affiliation(s)
- Michael L Ginger
- School of Health and Medicine, Division of Biomedical and Life Sciences, Lancaster University, Lancaster LA1 4YQ, UK.
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Keeling PJ. The endosymbiotic origin, diversification and fate of plastids. Philos Trans R Soc Lond B Biol Sci 2010; 365:729-48. [PMID: 20124341 DOI: 10.1098/rstb.2009.0103] [Citation(s) in RCA: 373] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Plastids and mitochondria each arose from a single endosymbiotic event and share many similarities in how they were reduced and integrated with their host. However, the subsequent evolution of the two organelles could hardly be more different: mitochondria are a stable fixture of eukaryotic cells that are neither lost nor shuffled between lineages, whereas plastid evolution has been a complex mix of movement, loss and replacement. Molecular data from the past decade have substantially untangled this complex history, and we now know that plastids are derived from a single endosymbiotic event in the ancestor of glaucophytes, red algae and green algae (including plants). The plastids of both red algae and green algae were subsequently transferred to other lineages by secondary endosymbiosis. Green algal plastids were taken up by euglenids and chlorarachniophytes, as well as one small group of dinoflagellates. Red algae appear to have been taken up only once, giving rise to a diverse group called chromalveolates. Additional layers of complexity come from plastid loss, which has happened at least once and probably many times, and replacement. Plastid loss is difficult to prove, and cryptic, non-photosynthetic plastids are being found in many non-photosynthetic lineages. In other cases, photosynthetic lineages are now understood to have evolved from ancestors with a plastid of different origin, so an ancestral plastid has been replaced with a new one. Such replacement has taken place in several dinoflagellates (by tertiary endosymbiosis with other chromalveolates or serial secondary endosymbiosis with a green alga), and apparently also in two rhizarian lineages: chlorarachniophytes and Paulinella (which appear to have evolved from chromalveolate ancestors). The many twists and turns of plastid evolution each represent major evolutionary transitions, and each offers a glimpse into how genomes evolve and how cells integrate through gene transfers and protein trafficking.
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Affiliation(s)
- Patrick J Keeling
- Botany Department, Canadian Institute for Advanced Research, University of British Columbia, 3529-6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4.
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320
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Zhou X, Lin Z, Ma H. Phylogenetic detection of numerous gene duplications shared by animals, fungi and plants. Genome Biol 2010; 11:R38. [PMID: 20370904 PMCID: PMC2884541 DOI: 10.1186/gb-2010-11-4-r38] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 02/04/2010] [Accepted: 04/06/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Gene duplication is considered a major driving force for evolution of genetic novelty, thereby facilitating functional divergence and organismal diversity, including the process of speciation. Animals, fungi and plants are major eukaryotic kingdoms and the divergences between them are some of the most significant evolutionary events. Although gene duplications in each lineage have been studied extensively in various contexts, the extent of gene duplication prior to the split of plants and animals/fungi is not clear. RESULTS Here, we have studied gene duplications in early eukaryotes by phylogenetic relative dating. We have reconstructed gene families (with one or more orthogroups) with members from both animals/fungi and plants by using two different clustering strategies. Extensive phylogenetic analyses of the gene families show that, among nearly 2,600 orthogroups identified, at least 300 of them still retain duplication that occurred before the divergence of the three kingdoms. We further found evidence that such duplications were also detected in some highly divergent protists, suggesting that these duplication events occurred in the ancestors of most major extant eukaryotic groups. CONCLUSIONS Our phylogenetic analyses show that numerous gene duplications happened at the early stage of eukaryotic evolution, probably before the separation of known major eukaryotic lineages. We discuss the implication of our results in the contexts of different models of eukaryotic phylogeny. One possible explanation for the large number of gene duplication events is one or more large-scale duplications, possibly whole genome or segmental duplication(s), which provides a genomic basis for the successful radiation of early eukaryotes.
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Affiliation(s)
- Xiaofan Zhou
- Department of Biology, the Pennsylvania State University, University Park, Pennsylvania 16802, USA
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321
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Mentel M, Martin W. Anaerobic animals from an ancient, anoxic ecological niche. BMC Biol 2010; 8:32. [PMID: 20370917 PMCID: PMC2859860 DOI: 10.1186/1741-7007-8-32] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Accepted: 04/06/2010] [Indexed: 11/10/2022] Open
Abstract
Tiny marine animals that complete their life cycle in the total absence of light and oxygen are reported by Roberto Danovaro and colleagues in this issue of BMC Biology. These fascinating animals are new members of the phylum Loricifera and possess mitochondria that in electron micrographs look very much like hydrogenosomes, the H2-producing mitochondria found among several unicellular eukaryotic lineages. The discovery of metazoan life in a permanently anoxic and sulphidic environment provides a glimpse of what a good part of Earth's past ecology might have been like in 'Canfield oceans', before the rise of deep marine oxygen levels and the appearance of the first large animals in the fossil record roughly 550-600 million years ago. The findings underscore the evolutionary significance of anaerobic deep sea environments and the anaerobic lifestyle among mitochondrion-bearing cells. They also testify that a fuller understanding of eukaryotic and metazoan evolution will come from the study of modern anoxic and hypoxic habitats.
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Affiliation(s)
- Marek Mentel
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina CH-1, Bratislava, Slovakia
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322
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Kellmann R, Stüken A, Orr RJS, Svendsen HM, Jakobsen KS. Biosynthesis and molecular genetics of polyketides in marine dinoflagellates. Mar Drugs 2010; 8:1011-48. [PMID: 20479965 PMCID: PMC2866473 DOI: 10.3390/md8041011] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Revised: 03/17/2010] [Accepted: 03/26/2010] [Indexed: 11/20/2022] Open
Abstract
Marine dinoflagellates are the single most important group of algae that produce toxins, which have a global impact on human activities. The toxins are chemically diverse, and include macrolides, cyclic polyethers, spirolides and purine alkaloids. Whereas there is a multitude of studies describing the pharmacology of these toxins, there is limited or no knowledge regarding the biochemistry and molecular genetics involved in their biosynthesis. Recently, however, exciting advances have been made. Expressed sequence tag sequencing studies have revealed important insights into the transcriptomes of dinoflagellates, whereas other studies have implicated polyketide synthase genes in the biosynthesis of cyclic polyether toxins, and the molecular genetic basis for the biosynthesis of paralytic shellfish toxins has been elucidated in cyanobacteria. This review summarises the recent progress that has been made regarding the unusual genomes of dinoflagellates, the biosynthesis and molecular genetics of dinoflagellate toxins. In addition, the evolution of these metabolic pathways will be discussed, and an outlook for future research and possible applications is provided.
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Affiliation(s)
- Ralf Kellmann
- University of Bergen, Department of Molecular Biology, 5020 Bergen, Norway; E-Mail:
| | - Anke Stüken
- University of Oslo, Department of Biology, Centre for Ecological and Evolutionary Synthesis (CEES), 0316 Oslo, Norway; E-Mails:
(A.S.);
(K.S.J.)
- University of Oslo, Department of Biology, Microbial Evolution Research Group (MERG), 0316 Oslo, Norway; E-Mail:
| | - Russell J. S. Orr
- University of Oslo, Department of Biology, Microbial Evolution Research Group (MERG), 0316 Oslo, Norway; E-Mail:
| | - Helene M. Svendsen
- University of Bergen, Department of Molecular Biology, 5020 Bergen, Norway; E-Mail:
| | - Kjetill S. Jakobsen
- University of Oslo, Department of Biology, Centre for Ecological and Evolutionary Synthesis (CEES), 0316 Oslo, Norway; E-Mails:
(A.S.);
(K.S.J.)
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Fritz-Laylin LK, Prochnik SE, Ginger ML, Dacks JB, Carpenter ML, Field MC, Kuo A, Paredez A, Chapman J, Pham J, Shu S, Neupane R, Cipriano M, Mancuso J, Tu H, Salamov A, Lindquist E, Shapiro H, Lucas S, Grigoriev IV, Cande WZ, Fulton C, Rokhsar DS, Dawson SC. The genome of Naegleria gruberi illuminates early eukaryotic versatility. Cell 2010; 140:631-42. [PMID: 20211133 DOI: 10.1016/j.cell.2010.01.032] [Citation(s) in RCA: 341] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 11/17/2009] [Accepted: 01/15/2010] [Indexed: 12/18/2022]
Abstract
Genome sequences of diverse free-living protists are essential for understanding eukaryotic evolution and molecular and cell biology. The free-living amoeboflagellate Naegleria gruberi belongs to a varied and ubiquitous protist clade (Heterolobosea) that diverged from other eukaryotic lineages over a billion years ago. Analysis of the 15,727 protein-coding genes encoded by Naegleria's 41 Mb nuclear genome indicates a capacity for both aerobic respiration and anaerobic metabolism with concomitant hydrogen production, with fundamental implications for the evolution of organelle metabolism. The Naegleria genome facilitates substantially broader phylogenomic comparisons of free-living eukaryotes than previously possible, allowing us to identify thousands of genes likely present in the pan-eukaryotic ancestor, with 40% likely eukaryotic inventions. Moreover, we construct a comprehensive catalog of amoeboid-motility genes. The Naegleria genome, analyzed in the context of other protists, reveals a remarkably complex ancestral eukaryote with a rich repertoire of cytoskeletal, sexual, signaling, and metabolic modules.
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Affiliation(s)
- Lillian K Fritz-Laylin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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324
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Tekle YI, Grant JR, Kovner AM, Townsend JP, Katz LA. Identification of new molecular markers for assembling the eukaryotic tree of life. Mol Phylogenet Evol 2010; 55:1177-82. [PMID: 20302952 DOI: 10.1016/j.ympev.2010.03.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 02/08/2010] [Accepted: 03/09/2010] [Indexed: 10/19/2022]
Abstract
Six eukaryotic supergroups have been proposed based on both morphological and molecular data. However, some of these supergroups are contentious and the deep relationships among them are poorly resolved. This is due to a limited number of morphological characters and few molecular markers in current use. The lack of resolution in most multigene analyses, including phylogenomic analyses, necessitates a search for additional, appropriate molecular markers to enable targeted sampling of taxa in key phylogenetic positions. We evaluated the phylogenetic signal of 860 proteins obtained from the Clusters of Orthologous Groups of proteins (COGs) database. We report a total of 17 markers that resulted in well-resolved topologies that are congruent with well-established components of the eukaryotic tree. To establish their utility, we designed universal degenerate primers for six markers, some of which showed promising results in unicellular eukaryotes. Finally, we present phylogenetic informativeness profiles for seven selected markers, revealing that the markers contain phylogenetic signal that spans the whole tree including the deeper branches.
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Affiliation(s)
- Yonas I Tekle
- Department of Biological Sciences, Smith College, Northampton, MA, USA.
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325
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Cavalier-Smith T. Origin of the cell nucleus, mitosis and sex: roles of intracellular coevolution. Biol Direct 2010; 5:7. [PMID: 20132544 PMCID: PMC2837639 DOI: 10.1186/1745-6150-5-7] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Accepted: 02/04/2010] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND The transition from prokaryotes to eukaryotes was the most radical change in cell organisation since life began, with the largest ever burst of gene duplication and novelty. According to the coevolutionary theory of eukaryote origins, the fundamental innovations were the concerted origins of the endomembrane system and cytoskeleton, subsequently recruited to form the cell nucleus and coevolving mitotic apparatus, with numerous genetic eukaryotic novelties inevitable consequences of this compartmentation and novel DNA segregation mechanism. Physical and mutational mechanisms of origin of the nucleus are seldom considered beyond the long-standing assumption that it involved wrapping pre-existing endomembranes around chromatin. Discussions on the origin of sex typically overlook its association with protozoan entry into dormant walled cysts and the likely simultaneous coevolutionary, not sequential, origin of mitosis and meiosis. RESULTS I elucidate nuclear and mitotic coevolution, explaining the origins of dicer and small centromeric RNAs for positionally controlling centromeric heterochromatin, and how 27 major features of the cell nucleus evolved in four logical stages, making both mechanisms and selective advantages explicit: two initial stages (origin of 30 nm chromatin fibres, enabling DNA compaction; and firmer attachment of endomembranes to heterochromatin) protected DNA and nascent RNA from shearing by novel molecular motors mediating vesicle transport, division, and cytoplasmic motility. Then octagonal nuclear pore complexes (NPCs) arguably evolved from COPII coated vesicle proteins trapped in clumps by Ran GTPase-mediated cisternal fusion that generated the fenestrated nuclear envelope, preventing lethal complete cisternal fusion, and allowing passive protein and RNA exchange. Finally, plugging NPC lumens by an FG-nucleoporin meshwork and adopting karyopherins for nucleocytoplasmic exchange conferred compartmentation advantages. These successive changes took place in naked growing cells, probably as indirect consequences of the origin of phagotrophy. The first eukaryote had 1-2 cilia and also walled resting cysts; I outline how encystation may have promoted the origin of meiotic sex. I also explain why many alternative ideas are inadequate. CONCLUSION Nuclear pore complexes are evolutionary chimaeras of endomembrane- and mitosis-related chromatin-associated proteins. The keys to understanding eukaryogenesis are a proper phylogenetic context and understanding organelle coevolution: how innovations in one cell component caused repercussions on others.
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326
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Birky CW. Giardia Sex? Yes, but how and how much? Trends Parasitol 2010; 26:70-4. [DOI: 10.1016/j.pt.2009.11.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Revised: 11/11/2009] [Accepted: 11/20/2009] [Indexed: 11/25/2022]
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327
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Verbruggen H, Maggs CA, Saunders GW, Le Gall L, Yoon HS, De Clerck O. Data mining approach identifies research priorities and data requirements for resolving the red algal tree of life. BMC Evol Biol 2010; 10:16. [PMID: 20089168 PMCID: PMC2826327 DOI: 10.1186/1471-2148-10-16] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Accepted: 01/20/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The assembly of the tree of life has seen significant progress in recent years but algae and protists have been largely overlooked in this effort. Many groups of algae and protists have ancient roots and it is unclear how much data will be required to resolve their phylogenetic relationships for incorporation in the tree of life. The red algae, a group of primary photosynthetic eukaryotes of more than a billion years old, provide the earliest fossil evidence for eukaryotic multicellularity and sexual reproduction. Despite this evolutionary significance, their phylogenetic relationships are understudied. This study aims to infer a comprehensive red algal tree of life at the family level from a supermatrix containing data mined from GenBank. We aim to locate remaining regions of low support in the topology, evaluate their causes and estimate the amount of data required to resolve them. RESULTS Phylogenetic analysis of a supermatrix of 14 loci and 98 red algal families yielded the most complete red algal tree of life to date. Visualization of statistical support showed the presence of five poorly supported regions. Causes for low support were identified with statistics about the age of the region, data availability and node density, showing that poor support has different origins in different parts of the tree. Parametric simulation experiments yielded optimistic estimates of how much data will be needed to resolve the poorly supported regions (ca. 103 to ca. 104 nucleotides for the different regions). Nonparametric simulations gave a markedly more pessimistic image, some regions requiring more than 2.8 105 nucleotides or not achieving the desired level of support at all. The discrepancies between parametric and nonparametric simulations are discussed in light of our dataset and known attributes of both approaches. CONCLUSIONS Our study takes the red algae one step closer to meaningful inclusion in the tree of life. In addition to the recovery of stable relationships, the recognition of five regions in need of further study is a significant outcome of this work. Based on our analyses of current availability and future requirements of data, we make clear recommendations for forthcoming research.
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Affiliation(s)
- Heroen Verbruggen
- Phycology Research Group and Center for Molecular Phylogenetics and Evolution, Ghent University, Krijgslaan 281, 9000 Ghent, Belgium.
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328
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de Graaf RM, Duarte I, van Alen TA, Kuiper JWP, Schotanus K, Rosenberg J, Huynen MA, Hackstein JHP. The hydrogenosomes of Psalteriomonas lanterna. BMC Evol Biol 2009; 9:287. [PMID: 20003182 PMCID: PMC2796672 DOI: 10.1186/1471-2148-9-287] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Accepted: 12/09/2009] [Indexed: 11/10/2022] Open
Abstract
Background Hydrogenosomes are organelles that produce molecular hydrogen and ATP. The broad phylogenetic distribution of their hosts suggests that the hydrogenosomes of these organisms evolved several times independently from the mitochondria of aerobic progenitors. Morphology and 18S rRNA phylogeny suggest that the microaerophilic amoeboflagellate Psalteriomonas lanterna, which possesses hydrogenosomes and elusive "modified mitochondria", belongs to the Heterolobosea, a taxon that consists predominantly of aerobic, mitochondriate organisms. This taxon is rather unrelated to taxa with hitherto studied hydrogenosomes. Results Electron microscopy of P. lanterna flagellates reveals a large globule in the centre of the cell that is build up from stacks of some 20 individual hydrogenosomes. The individual hydrogenosomes are surrounded by a double membrane that encloses a homogeneous, dark staining matrix lacking cristae. The "modified mitochondria" are found in the cytoplasm of the cell and are surrounded by 1-2 cisterns of rough endoplasmatic reticulum, just as the mitochondria of certain related aerobic Heterolobosea. The ultrastructure of the "modified mitochondria" and hydrogenosomes is very similar, and they have the same size distribution as the hydrogenosomes that form the central stack. The phylogenetic analysis of selected EST sequences (Hsp60, Propionyl-CoA carboxylase) supports the phylogenetic position of P. lanterna close to aerobic Heterolobosea (Naegleria gruberi). Moreover, this analysis also confirms the identity of several mitochondrial or hydrogenosomal key-genes encoding proteins such as a Hsp60, a pyruvate:ferredoxin oxidoreductase, a putative ADP/ATP carrier, a mitochondrial complex I subunit (51 KDa), and a [FeFe] hydrogenase. Conclusion Comparison of the ultrastructure of the "modified mitochondria" and hydrogenosomes strongly suggests that both organelles are just two morphs of the same organelle. The EST studies suggest that the hydrogenosomes of P. lanterna are physiologically similar to the hydrogenosomes of Trichomonas vaginalis and Trimastix pyriformis. Phylogenetic analysis of the ESTs confirms the relationship of P. lanterna with its aerobic relative, the heterolobosean amoeboflagellate Naegleria gruberi, corroborating the evolution of hydrogenosomes from a common, mitochondriate ancestor.
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Affiliation(s)
- Rob M de Graaf
- Department of Evolutionary Microbiology, IWWR, Radboud University Nijmegen, The Netherlands
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Liu Y, Steenkamp ET, Brinkmann H, Forget L, Philippe H, Lang BF. Phylogenomic analyses predict sistergroup relationship of nucleariids and fungi and paraphyly of zygomycetes with significant support. BMC Evol Biol 2009; 9:272. [PMID: 19939264 PMCID: PMC2789072 DOI: 10.1186/1471-2148-9-272] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2009] [Accepted: 11/25/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Resolving the evolutionary relationships among Fungi remains challenging because of their highly variable evolutionary rates, and lack of a close phylogenetic outgroup. Nucleariida, an enigmatic group of amoeboids, have been proposed to emerge close to the fungal-metazoan divergence and might fulfill this role. Yet, published phylogenies with up to five genes are without compelling statistical support, and genome-level data should be used to resolve this question with confidence. RESULTS Our analyses with nuclear (118 proteins) and mitochondrial (13 proteins) data now robustly associate Nucleariida and Fungi as neighbors, an assemblage that we term 'Holomycota'. With Nucleariida as an outgroup, we revisit unresolved deep fungal relationships. CONCLUSION Our phylogenomic analysis provides significant support for the paraphyly of the traditional taxon Zygomycota, and contradicts a recent proposal to include Mortierella in a phylum Mucoromycotina. We further question the introduction of separate phyla for Glomeromycota and Blastocladiomycota, whose phylogenetic positions relative to other phyla remain unresolved even with genome-level datasets. Our results motivate broad sampling of additional genome sequences from these phyla.
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Affiliation(s)
- Yu Liu
- Robert Cedergren Centre, Département de biochimie, Université de Montréal, Montréal, Québec, Canada
- Present address: Donnelly Centre for Cellular and Bio-molecular Research, Department of Molecular Genetics, University of Toronto, 160 College Street, Toronto, ON, M5S 3E1, Canada
| | - Emma T Steenkamp
- Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa
| | - Henner Brinkmann
- Robert Cedergren Centre, Département de biochimie, Université de Montréal, Montréal, Québec, Canada
| | - Lise Forget
- Robert Cedergren Centre, Département de biochimie, Université de Montréal, Montréal, Québec, Canada
| | - Hervé Philippe
- Robert Cedergren Centre, Département de biochimie, Université de Montréal, Montréal, Québec, Canada
| | - B Franz Lang
- Robert Cedergren Centre, Département de biochimie, Université de Montréal, Montréal, Québec, Canada
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331
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Mowbrey K, Dacks JB. Evolution and diversity of the Golgi body. FEBS Lett 2009; 583:3738-45. [PMID: 19837068 DOI: 10.1016/j.febslet.2009.10.025] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Accepted: 10/11/2009] [Indexed: 01/15/2023]
Abstract
Often considered a defining eukaryotic feature, the Golgi body is one of the most recognizable and functionally integrated cellular organelles. It is therefore surprising that some unicellular eukaryotes do not, at first glance, appear to possess Golgi stacks. Here we review the molecular evolutionary, genomic and cell biological evidence for Golgi bodies in these organisms, with the organelle likely present in some form in all cases. This, along with the overwhelming prevalence of stacked cisternae in most eukaryotes, implies that the ancestral eukaryote possessed a stacked Golgi body, with at least eight independent instances of Golgi unstacking in our cellular history.
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Affiliation(s)
- Kevin Mowbrey
- Department of Cell Biology, University of Alberta, Edmonton, Canada T6G 2H7
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332
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Le Corguillé G, Pearson G, Valente M, Viegas C, Gschloessl B, Corre E, Bailly X, Peters AF, Jubin C, Vacherie B, Cock JM, Leblanc C. Plastid genomes of two brown algae, Ectocarpus siliculosus and Fucus vesiculosus: further insights on the evolution of red-algal derived plastids. BMC Evol Biol 2009; 9:253. [PMID: 19835607 PMCID: PMC2765969 DOI: 10.1186/1471-2148-9-253] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2009] [Accepted: 10/16/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Heterokont algae, together with cryptophytes, haptophytes and some alveolates, possess red-algal derived plastids. The chromalveolate hypothesis proposes that the red-algal derived plastids of all four groups have a monophyletic origin resulting from a single secondary endosymbiotic event. However, due to incongruence between nuclear and plastid phylogenies, this controversial hypothesis remains under debate. Large-scale genomic analyses have shown to be a powerful tool for phylogenetic reconstruction but insufficient sequence data have been available for red-algal derived plastid genomes. RESULTS The chloroplast genomes of two brown algae, Ectocarpus siliculosus and Fucus vesiculosus, have been fully sequenced. These species represent two distinct orders of the Phaeophyceae, which is a major group within the heterokont lineage. The sizes of the circular plastid genomes are 139,954 and 124,986 base pairs, respectively, the size difference being due principally to the presence of longer inverted repeat and intergenic regions in E. siliculosus. Gene contents of the two plastids are similar with 139-148 protein-coding genes, 28-31 tRNA genes, and 3 ribosomal RNA genes. The two genomes also exhibit very similar rearrangements compared to other sequenced plastid genomes. The tRNA-Leu gene of E. siliculosus lacks an intron, in contrast to the F. vesiculosus and other heterokont plastid homologues, suggesting its recent loss in the Ectocarpales. Most of the brown algal plastid genes are shared with other red-algal derived plastid genomes, but a few are absent from raphidophyte or diatom plastid genomes. One of these regions is most similar to an apicomplexan nuclear sequence. The phylogenetic relationship between heterokonts, cryptophytes and haptophytes (collectively referred to as chromists) plastids was investigated using several datasets of concatenated proteins from two cyanobacterial genomes and 18 plastid genomes, including most of the available red algal and chromist plastid genomes. CONCLUSION The phylogenetic studies using concatenated plastid proteins still do not resolve the question of the monophyly of all chromist plastids. However, these results support both the monophyly of heterokont plastids and that of cryptophyte and haptophyte plastids, in agreement with nuclear phylogenies.
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Affiliation(s)
- Gildas Le Corguillé
- CNRS, FR2424, Computer and Genomics Resource Centre, Station Biologique, Roscoff, France
- UPMC Univ. Paris 06, FR2424, Computer and Genomics Resource Centre, Station Biologique, Roscoff, France
| | - Gareth Pearson
- Centre of Marine Sciences, University of Algarve, Marine Ecology and Evolution, Faro, Portugal
| | - Marta Valente
- Centre of Marine Sciences, University of Algarve, Marine Ecology and Evolution, Faro, Portugal
| | - Carla Viegas
- Centre of Marine Sciences, University of Algarve, Marine Ecology and Evolution, Faro, Portugal
| | - Bernhard Gschloessl
- CNRS, UMR7139, Marine Plants and Biomolecules, Station Biologique, Roscoff, France
- UPMC Univ. Paris 06, UMR7139, Marine Plants and Biomolecules, Station Biologique, Roscoff, France
| | - Erwan Corre
- CNRS, FR2424, Computer and Genomics Resource Centre, Station Biologique, Roscoff, France
- UPMC Univ. Paris 06, FR2424, Computer and Genomics Resource Centre, Station Biologique, Roscoff, France
| | - Xavier Bailly
- CNRS, FR2424, Computer and Genomics Resource Centre, Station Biologique, Roscoff, France
- UPMC Univ. Paris 06, FR2424, Computer and Genomics Resource Centre, Station Biologique, Roscoff, France
| | - Akira F Peters
- CNRS, UMR7139, Marine Plants and Biomolecules, Station Biologique, Roscoff, France
- UPMC Univ. Paris 06, UMR7139, Marine Plants and Biomolecules, Station Biologique, Roscoff, France
| | - Claire Jubin
- CEA, DSV, Institut de Génomique, Genoscope, Evry, France
- CNRS, UMR 8030, Evry, France
- Université d'Evry, Evry, France
| | | | - J Mark Cock
- CNRS, UMR7139, Marine Plants and Biomolecules, Station Biologique, Roscoff, France
- UPMC Univ. Paris 06, UMR7139, Marine Plants and Biomolecules, Station Biologique, Roscoff, France
| | - Catherine Leblanc
- CNRS, UMR7139, Marine Plants and Biomolecules, Station Biologique, Roscoff, France
- UPMC Univ. Paris 06, UMR7139, Marine Plants and Biomolecules, Station Biologique, Roscoff, France
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333
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Hug LA, Stechmann A, Roger AJ. Phylogenetic Distributions and Histories of Proteins Involved in Anaerobic Pyruvate Metabolism in Eukaryotes. Mol Biol Evol 2009; 27:311-24. [DOI: 10.1093/molbev/msp237] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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334
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Orosz F. Apicortin, a unique protein, with a putative cytoskeletal role, shared only by apicomplexan parasites and the placozoan Trichoplax adhaerens. INFECTION GENETICS AND EVOLUTION 2009; 9:1275-86. [PMID: 19778640 DOI: 10.1016/j.meegid.2009.09.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Revised: 09/11/2009] [Accepted: 09/14/2009] [Indexed: 11/25/2022]
Abstract
A new protein, termed apicortin, has been identified, which contains a DCX (doublecortin) and a partial p25-alpha domain. The DCX domains of the doublecortin superfamily are responsible for their microtubule binding and stabilizing properties. The p25-alpha domain occurs in TPPPs (Tubulin Polymerization Promoting Proteins) exhibiting Microtubule Associated Protein (MAP)-like functions. TPPP orthologs can be classified as long- and short-type ones. The latter ones do not contain the partial p25-alpha domain, which is the most conservative part of the long-type TPPPs and was evolutionary-preserved independently from the whole domain. Apicortin seems to occur only in the placozoan animal Trichoplax adhaerens and in each of the apicomplexan parasites, the genomes of which are available. The function of the novel protein can be predicted from the fact that it contains two different microtubule-binding domains. Apicomplexans, important pathogens of humans and animals, possess unique cytoskeletal elements, as subpellicular microtubules and apical polar rings, which are specific for this phylum, extremely stabilized by unknown MAPs. One of the candidates can be the apicortin, which is supported by a recent experimental proteomics analysis. The role of the new protein in T. adhaerens may be similar but needs clarification.
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Affiliation(s)
- Ferenc Orosz
- Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, Karolina út 29, H-1113 Budapest, Hungary.
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335
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Elias M, Patron NJ, Keeling PJ. The RAB family GTPase Rab1A from Plasmodium falciparum defines a unique paralog shared by chromalveolates and rhizaria. J Eukaryot Microbiol 2009; 56:348-56. [PMID: 19602080 DOI: 10.1111/j.1550-7408.2009.00408.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The RAB GTPases, which are involved in regulation of endomembrane trafficking, exhibit a complex but incompletely understood evolutionary history. We elucidated the evolution of the RAB1 subfamily ancestrally implicated in the endoplasmic reticulum-to-Golgi traffic. We found that RAB1 paralogs have been generated over the course of eukaryotic evolution, with some duplications coinciding with the advent of major eukaryotic lineages (e.g. Metazoa, haptophytes). We also identified a unique, derived RAB1 paralog, orthologous to the Plasmodium Rab1A, that occurs in stramenopiles, alveolates, and Rhizaria, represented by the chlorarachniophyte Gymnochlora stellata. This finding is consistent with the recently documented existence of a major eukaryotic clade ("SAR") comprising these three lineages. We further found a Rab1A-like protein in the cryptophyte Guillardia theta, but it exhibits unusual features among RAB proteins: absence of a C-terminal prenylation motif and an N-terminal extension with two MSP domains; and its phylogenetic relationships could not be established convincingly due to its divergent nature. Our results nevertheless point to a unique membrane trafficking pathway shared by at least some lineages of chromalveolates and Rhizaria, an insight that has implications towards interpreting the early evolution of eukaryotes and the endomembrane system.
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Affiliation(s)
- Marek Elias
- Department of Botany, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
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336
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Okamoto N, Chantangsi C, Horák A, Leander BS, Keeling PJ. Molecular phylogeny and description of the novel katablepharid Roombia truncata gen. et sp. nov., and establishment of the Hacrobia taxon nov. PLoS One 2009; 4:e7080. [PMID: 19759916 PMCID: PMC2741603 DOI: 10.1371/journal.pone.0007080] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Accepted: 08/10/2009] [Indexed: 11/18/2022] Open
Abstract
Background Photosynthetic eukaryotes with a secondary plastid of red algal origin (cryptophytes, haptophytes, stramenopiles, dinoflagellates, and apicomplexans) are hypothesized to share a single origin of plastid acquisition according to Chromalveolate hypothesis. Recent phylogenomic analyses suggest that photosynthetic “chromalveolates” form a large clade with inclusion of several non-photosynthetic protist lineages. Katablepharids are one such non-photosynthetic lineage closely related to cryptophytes. Despite their evolutionary and ecological importance, katablepharids are poorly investigated. Methodology/Principal Findings Here, we report a newly discovered flagellate, Roombia truncata gen. et sp. nov., that is related to katablepharids, but is morphologically distinct from othermembers of the group in the following ways: (1) two flagella emerge from a papilla-like subapical protrusion, (2) conspicuous ejectisomes are aligned in multiple (5–11) rows, (3) each ejectisome increases in size towards the posterior end of the rows, and (4) upon feeding, a part of cytoplasm elastically stretch to engulf whole prey cell. Molecular phylogenies inferred from Hsp90, SSU rDNA, and LSU rDNA sequences consistently and strongly show R. truncata as the sister lineage to all other katablepharids, including lineages known only from environmental sequence surveys. A close association between katablepharids and cryptophytes was also recovered in most analyses. Katablepharids and cryptophytes are together part of a larger, more inclusive, group that also contains haptophytes, telonemids, centrohelids and perhaps biliphytes. The monophyly of this group is supported by several different molecular phylogenetic datasets and one shared lateral gene transfer; therefore, we formally establish this diverse clade as the “Hacrobia.” Conclusions/Significance Our discovery of R. truncata not only expands our knowledge in the less studied flagellate group, but provide a better understanding of phylogenetic relationship and evolutionary view of plastid acquisition/losses of Hacrobia. Being an ancestral to all katablepharids, and readily cultivable, R. truncata is a good candidate for multiple gene analyses that will contribute to future phylogenetic studies of Hacrobia.
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Affiliation(s)
- Noriko Okamoto
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
| | - Chitchai Chantangsi
- Departments of Botany and Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Aleš Horák
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
| | - Brian S. Leander
- Departments of Botany and Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Patrick J. Keeling
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
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337
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Liu H, Aris-Brosou S, Probert I, de Vargas C. A Time line of the Environmental Genetics of the Haptophytes. Mol Biol Evol 2009; 27:161-76. [DOI: 10.1093/molbev/msp222] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
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338
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Desmond E, Gribaldo S. Phylogenomics of sterol synthesis: insights into the origin, evolution, and diversity of a key eukaryotic feature. Genome Biol Evol 2009; 1:364-81. [PMID: 20333205 PMCID: PMC2817430 DOI: 10.1093/gbe/evp036] [Citation(s) in RCA: 173] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/04/2009] [Indexed: 12/17/2022] Open
Abstract
The availability of complete genomes from a wide sampling of eukaryotic diversity has allowed the application of phylogenomics approaches to study the origin and evolution of unique eukaryotic cellular structures, but these are still poorly applied to study unique eukaryotic metabolic pathways. Sterols are a good example because they are an essential feature of eukaryotic membranes. The sterol pathway has been well dissected in vertebrates, fungi, and land plants. However, although different types of sterols have been identified in other eukaryotic lineages, their pathways have not been fully characterized. We have carried out an extensive analysis of the taxonomic distribution and phylogeny of the enzymes of the sterol pathway in a large sampling of eukaryotic lineages. This allowed us to tentatively indicate features of the sterol pathway in organisms where this has not been characterized and to point out a number of steps for which yet-to-discover enzymes may be at work. We also inferred that the last eukaryotic common ancestor already harbored a large panel of enzymes for sterol synthesis and that subsequent evolution over the eukaryotic tree occurred by tinkering, mainly by gene losses. We highlight a high capacity of sterol synthesis in the myxobacterium Plesiocystis pacifica, and we support the hypothesis that the few bacteria that harbor homologs of the sterol pathway have likely acquired these via horizontal gene transfer from eukaryotes. Finally, we propose a potential candidate for the elusive enzyme performing C-3 ketoreduction (ERG27 equivalent) in land plants and probably in other eukaryotic phyla.
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Affiliation(s)
- Elie Desmond
- Institut Pasteur, Unité de Biologie Moléculaire du gène chez les Extrêmophiles, Paris, France
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339
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Wang HC, Susko E, Roger AJ. PROCOV: maximum likelihood estimation of protein phylogeny under covarion models and site-specific covarion pattern analysis. BMC Evol Biol 2009; 9:225. [PMID: 19737395 PMCID: PMC2758850 DOI: 10.1186/1471-2148-9-225] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2009] [Accepted: 09/08/2009] [Indexed: 11/12/2022] Open
Abstract
Background The covarion hypothesis of molecular evolution holds that selective pressures on a given amino acid or nucleotide site are dependent on the identity of other sites in the molecule that change throughout time, resulting in changes of evolutionary rates of sites along the branches of a phylogenetic tree. At the sequence level, covarion-like evolution at a site manifests as conservation of nucleotide or amino acid states among some homologs where the states are not conserved in other homologs (or groups of homologs). Covarion-like evolution has been shown to relate to changes in functions at sites in different clades, and, if ignored, can adversely affect the accuracy of phylogenetic inference. Results PROCOV (protein covarion analysis) is a software tool that implements a number of previously proposed covarion models of protein evolution for phylogenetic inference in a maximum likelihood framework. Several algorithmic and implementation improvements in this tool over previous versions make computationally expensive tree searches with covarion models more efficient and analyses of large phylogenomic data sets tractable. PROCOV can be used to identify covarion sites by comparing the site likelihoods under the covarion process to the corresponding site likelihoods under a rates-across-sites (RAS) process. Those sites with the greatest log-likelihood difference between a 'covarion' and an RAS process were found to be of functional or structural significance in a dataset of bacterial and eukaryotic elongation factors. Conclusion Covarion models implemented in PROCOV may be especially useful for phylogenetic estimation when ancient divergences between sequences have occurred and rates of evolution at sites are likely to have changed over the tree. It can also be used to study lineage-specific functional shifts in protein families that result in changes in the patterns of site variability among subtrees.
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Affiliation(s)
- Huai-Chun Wang
- Department of Mathematics and Statistics, Dalhousie University, Halifax, NS, Canada.
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340
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Nozaki H, Maruyama S, Matsuzaki M, Nakada T, Kato S, Misawa K. Phylogenetic positions of Glaucophyta, green plants (Archaeplastida) and Haptophyta (Chromalveolata) as deduced from slowly evolving nuclear genes. Mol Phylogenet Evol 2009; 53:872-80. [PMID: 19698794 DOI: 10.1016/j.ympev.2009.08.015] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Revised: 06/15/2009] [Accepted: 08/13/2009] [Indexed: 11/16/2022]
Abstract
The phylogenetic positions of the primary photosynthetic eukaryotes, or Archaeplastida (green plants, red algae, and glaucophytes) and the secondary photosynthetic chromalveolates, Haptophyta, vary depending on the data matrices used in the previous nuclear multigene phylogenetic studies. Here, we deduced the phylogeny of three groups of Archaeplastida and Haptophyta on the basis of sequences of the multiple slowly evolving nuclear genes and reduced the gaps or missing data, especially in glaucophyte operational taxonomic units (OTUs). The present multigene phylogenetic analyses resolved that Haptophyta and two other groups of Chromalveolata, stramenopiles and Alveolata, form a monophyletic group that is sister to the green plants and that the glaucophytes and red algae are basal to the clade composed of green plants and Chromalveolata. The bootstrap values supporting these phylogenetic relationships increased with the exclusion of long-branched OTUs. The close relationship between green plants and Chromalveolata is further supported by the common replacement in two plastid-targeted genes.
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Affiliation(s)
- Hisayoshi Nozaki
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
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341
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Maruyama S, Matsuzaki M, Misawa K, Nozaki H. Cyanobacterial contribution to the genomes of the plastid-lacking protists. BMC Evol Biol 2009; 9:197. [PMID: 19664294 PMCID: PMC3087521 DOI: 10.1186/1471-2148-9-197] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Accepted: 08/11/2009] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Eukaryotic genes with cyanobacterial ancestry in plastid-lacking protists have been regarded as important evolutionary markers implicating the presence of plastids in the early evolution of eukaryotes. Although recent genomic surveys demonstrated the presence of cyanobacterial and algal ancestry genes in the genomes of plastid-lacking protists, comparative analyses on the origin and distribution of those genes are still limited. RESULTS We identified 12 gene families with cyanobacterial ancestry in the genomes of a taxonomically wide range of plastid-lacking eukaryotes (Phytophthora [Chromalveolata], Naegleria [Excavata], Dictyostelium [Amoebozoa], Saccharomyces and Monosiga [Opisthokonta]) using a novel phylogenetic pipeline. The eukaryotic gene clades with cyanobacterial ancestry were mostly composed of genes from bikonts (Archaeplastida, Chromalveolata, Rhizaria and Excavata). We failed to find genes with cyanobacterial ancestry in Saccharomyces and Dictyostelium, except for a photorespiratory enzyme conserved among fungi. Meanwhile, we found several Monosiga genes with cyanobacterial ancestry, which were unrelated to other Opisthokonta genes. CONCLUSION Our data demonstrate that a considerable number of genes with cyanobacterial ancestry have contributed to the genome composition of the plastid-lacking protists, especially bikonts. The origins of those genes might be due to lateral gene transfer events, or an ancient primary or secondary endosymbiosis before the diversification of bikonts. Our data also show that all genes identified in this study constitute multi-gene families with punctate distribution among eukaryotes, suggesting that the transferred genes could have survived through rounds of gene family expansion and differential reduction.
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Affiliation(s)
- Shinichiro Maruyama
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
| | - Motomichi Matsuzaki
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
- Current address: Department of Biomedical Chemistry, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
- Current address: Research Program for Computational Science, Riken, 4-6-1 Shirokane-dai, Minato-ku, Tokyo 108-8639, Japan
| | - Kazuharu Misawa
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
- Current address: Research Program for Computational Science, Riken, 4-6-1 Shirokane-dai, Minato-ku, Tokyo 108-8639, Japan
| | - Hisayoshi Nozaki
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
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342
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Torruella G, Suga H, Riutort M, Peretó J, Ruiz-Trillo I. The Evolutionary History of Lysine Biosynthesis Pathways Within Eukaryotes. J Mol Evol 2009; 69:240-8. [DOI: 10.1007/s00239-009-9266-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Revised: 07/09/2009] [Accepted: 07/15/2009] [Indexed: 11/30/2022]
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343
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Burki F, Inagaki Y, Bråte J, Archibald JM, Keeling PJ, Cavalier-Smith T, Sakaguchi M, Hashimoto T, Horak A, Kumar S, Klaveness D, Jakobsen KS, Pawlowski J, Shalchian-Tabrizi K. Large-scale phylogenomic analyses reveal that two enigmatic protist lineages, telonemia and centroheliozoa, are related to photosynthetic chromalveolates. Genome Biol Evol 2009; 1:231-8. [PMID: 20333193 PMCID: PMC2817417 DOI: 10.1093/gbe/evp022] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/20/2009] [Indexed: 12/03/2022] Open
Abstract
Understanding the early evolution and diversification of eukaryotes relies on a fully resolved phylogenetic tree. In recent years, most eukaryotic diversity has been assigned to six putative supergroups, but the evolutionary origin of a few major “orphan” lineages remains elusive. Two ecologically important orphan groups are the heterotrophic Telonemia and Centroheliozoa. Telonemids have been proposed to be related to the photosynthetic cryptomonads or stramenopiles and centrohelids to haptophytes, but molecular phylogenies have failed to provide strong support for any phylogenetic hypothesis. Here, we investigate the origins of Telonema subtilis (a telonemid) and Raphidiophrys contractilis (a centrohelid) by large-scale 454 pyrosequencing of cDNA libraries and including new genomic data from two cryptomonads (Guillardia theta and Plagioselmis nannoplanctica) and a haptophyte (Imantonia rotunda). We demonstrate that 454 sequencing of cDNA libraries is a powerful and fast method of sampling a high proportion of protist genes, which can yield ample information for phylogenomic studies. Our phylogenetic analyses of 127 genes from 72 species indicate that telonemids and centrohelids are members of an emerging major group of eukaryotes also comprising cryptomonads and haptophytes. Furthermore, this group is possibly closely related to the SAR clade comprising stramenopiles (heterokonts), alveolates, and Rhizaria. Our results link two additional heterotrophic lineages to the predominantly photosynthetic chromalveolate supergroup, providing a new framework for interpreting the evolution of eukaryotic cell structures and the diversification of plastids.
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344
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Chen XS, Collins LJ, Biggs PJ, Penny D. High throughput genome-wide survey of small RNAs from the parasitic protists Giardia intestinalis and Trichomonas vaginalis. Genome Biol Evol 2009; 1:165-75. [PMID: 20333187 PMCID: PMC2817412 DOI: 10.1093/gbe/evp017] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/30/2009] [Indexed: 12/26/2022] Open
Abstract
RNA interference (RNAi) is a set of mechanisms which regulate gene expression in eukaryotes. Key elements of RNAi are small sense and antisense RNAs from 19 to 26 nt generated from double-stranded RNAs. MicroRNAs (miRNAs) are a major type of RNAi-associated small RNAs and are found in most eukaryotes studied to date. To investigate whether small RNAs associated with RNAi appear to be present in all eukaryotic lineages, and therefore present in the ancestral eukaryote, we studied two deep-branching protozoan parasites, Giardia intestinalis and Trichomonas vaginalis. Little is known about endogenous small RNAs involved in RNAi of these organisms. Using Illumina Solexa sequencing and genome-wide analysis of small RNAs from these distantly related deep-branching eukaryotes, we identified 10 strong miRNA candidates from Giardia and 11 from Trichomonas. We also found evidence of Giardia short-interfering RNAs potentially involved in the expression of variant-specific surface proteins. In addition, eight new small nucleolar RNAs from Trichomonas are identified. Our results indicate that miRNAs are likely to be general in ancestral eukaryotes and therefore are likely to be a universal feature of eukaryotes.
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Affiliation(s)
- Xiaowei Sylvia Chen
- Allan Wilson Centre for Molecular Ecology and Evolution, Massey University, Palmerston North, New Zealand.
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345
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Cascades of convergent evolution: the corresponding evolutionary histories of euglenozoans and dinoflagellates. Proc Natl Acad Sci U S A 2009; 106 Suppl 1:9963-70. [PMID: 19528647 DOI: 10.1073/pnas.0901004106] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The majority of eukaryotic diversity is hidden in protists, yet our current knowledge of processes and structures in the eukaryotic cell is almost exclusively derived from multicellular organisms. The increasing sensitivity of molecular methods and growing interest in microeukaryotes has only recently demonstrated that many features so far considered to be universal for eukaryotes actually exist in strikingly different versions. In other words, during their long evolutionary histories, protists have solved general biological problems in many more ways than previously appreciated. Interestingly, some groups have broken more rules than others, and the Euglenozoa and the Alveolata stand out in this respect. A review of the numerous odd features in these 2 groups allows us to draw attention to the high level of convergent evolution in protists, which perhaps reflects the limits that certain features can be altered. Moreover, the appearance of one deviation in an ancestor can constrain the set of possible downstream deviations in its descendents, so features that might be independent functionally, can still be evolutionarily linked. What functional advantage may be conferred by the excessive complexity of euglenozoan and alveolate gene expression, organellar genome structure, and RNA editing and processing has been thoroughly debated, but we suggest these are more likely the products of constructive neutral evolution, and as such do not necessarily confer any selective advantage at all.
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346
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Rogozin IB, Basu MK, Csürös M, Koonin EV. Analysis of rare genomic changes does not support the unikont-bikont phylogeny and suggests cyanobacterial symbiosis as the point of primary radiation of eukaryotes. Genome Biol Evol 2009; 1:99-113. [PMID: 20333181 PMCID: PMC2817406 DOI: 10.1093/gbe/evp011] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/21/2009] [Indexed: 11/29/2022] Open
Abstract
The deep phylogeny of eukaryotes is an important but extremely difficult problem of evolutionary biology. Five eukaryotic supergroups are relatively well established but the relationship between these supergroups remains elusive, and their divergence seems to best fit a “Big Bang” model. Attempts were made to root the tree of eukaryotes by using potential derived shared characters such as unique fusions of conserved genes. One popular model of eukaryotic evolution that emerged from this type of analysis is the unikont–bikont phylogeny: The unikont branch consists of Metazoa, Choanozoa, Fungi, and Amoebozoa, whereas bikonts include the rest of eukaryotes, namely, Plantae (green plants, Chlorophyta, and Rhodophyta), Chromalveolata, excavates, and Rhizaria. We reexamine the relationships between the eukaryotic supergroups using a genome-wide analysis of rare genomic changes (RGCs) associated with multiple, conserved amino acids (RGC_CAMs and RGC_CAs), to resolve trifurcations of major eukaryotic lineages. The results do not support the basal position of Chromalveolata with respect to Plantae and unikonts or the monophyly of the bikont group and appear to be best compatible with the monophyly of unikonts and Chromalveolata. Chromalveolata show a distinct, additional signal of affinity with Plantae, conceivably, owing to genes transferred from the secondary, red algal symbiont. Excavates are derived forms, with extremely long branches that complicate phylogenetic inference; nevertheless, the RGC analysis suggests that they are significantly more likely to cluster with the unikont–Chromalveolata assemblage than with the Plantae. Thus, the first split in eukaryotic evolution might lie between photosynthetic and nonphotosynthetic forms and so could have been triggered by the endosymbiosis between an ancestral unicellular eukaryote and a cyanobacterium that gave rise to the chloroplast.
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Affiliation(s)
- Igor B Rogozin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
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347
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Abstract
The long polycistronic transcription units of trypanosomes do not appear to be demarcated by the usual DNA motifs that punctuate transcription in familiar eukaryotes. In this issue of Genes & Development, Siegel and colleagues (pp. 1063-1076) describe a system for the demarcation of trypanosome transcription units based on the deposition and turnover of histone variants rather than on the binding of transcription factors. Replication-independent incorporation of histone variants and destabilization of nucleosomes is an emerging theme at promoters of more familiar eukaryotes, and it now appears that this system is an evolutionarily conserved mode of transcriptional punctuation.
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Affiliation(s)
- Paul B Talbert
- Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.
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