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R Marcelino V, Cremen MCM, Jackson CJ, Larkum AAW, Verbruggen H. Evolutionary Dynamics of Chloroplast Genomes in Low Light: A Case Study of the Endolithic Green Alga Ostreobium quekettii. Genome Biol Evol 2016; 8:2939-2951. [PMID: 27566760 PMCID: PMC5633697 DOI: 10.1093/gbe/evw206] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Some photosynthetic organisms live in extremely low light environments. Light limitation is associated with selective forces as well as reduced exposure to mutagens, and over evolutionary timescales it can leave a footprint on species’ genomes. Here, we present the chloroplast genomes of four green algae (Bryopsidales, Ulvophyceae), including the endolithic (limestone-boring) alga Ostreobium quekettii, which is a low light specialist. We use phylogenetic models and comparative genomic tools to investigate whether the chloroplast genome of Ostreobium corresponds to our expectations of how low light would affect genome evolution. Ostreobium has the smallest and most gene-dense chloroplast genome among Ulvophyceae reported to date, matching our expectation that light limitation would impose resource constraints reflected in the chloroplast genome architecture. Rates of molecular evolution are significantly slower along the phylogenetic branch leading to Ostreobium, in agreement with the expected effects of low light and energy levels on molecular evolution. We expected the ability of Ostreobium to perform photosynthesis in very low light to be associated with positive selection in genes related to the photosynthetic machinery, but instead, we observed that these genes may be under stronger purifying selection. Besides shedding light on the genome dynamics associated with a low light lifestyle, this study helps to resolve the role of environmental factors in shaping the diversity of genome architectures observed in nature.
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Affiliation(s)
| | | | | | - Anthony A W Larkum
- Plant Functional Biology and Climate Change Cluster, University of Technology Sydney, NSW 2007, Australia
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152
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Abstract
Bacteria and archaea typically possess small genomes that are tightly packed with protein-coding genes. The compactness of prokaryotic genomes is commonly perceived as evidence of adaptive genome streamlining caused by strong purifying selection in large microbial populations. In such populations, even the small cost incurred by nonfunctional DNA because of extra energy and time expenditure is thought to be sufficient for this extra genetic material to be eliminated by selection. However, contrary to the predictions of this model, there exists a consistent, positive correlation between the strength of selection at the protein sequence level, measured as the ratio of nonsynonymous to synonymous substitution rates, and microbial genome size. Here, by fitting the genome size distributions in multiple groups of prokaryotes to predictions of mathematical models of population evolution, we show that only models in which acquisition of additional genes is, on average, slightly beneficial yield a good fit to genomic data. These results suggest that the number of genes in prokaryotic genomes reflects the equilibrium between the benefit of additional genes that diminishes as the genome grows and deletion bias (i.e., the rate of deletion of genetic material being slightly greater than the rate of acquisition). Thus, new genes acquired by microbial genomes, on average, appear to be adaptive. The tight spacing of protein-coding genes likely results from a combination of the deletion bias and purifying selection that efficiently eliminates nonfunctional, noncoding sequences.
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153
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Abstract
Almost all cellular life forms are hosts to diverse genetic parasites with various levels of autonomy including plasmids, transposons and viruses. Theoretical modeling of the evolution of primordial replicators indicates that parasites (cheaters) necessarily evolve in such systems and can be kept at bay primarily via compartmentalization. Given the (near) ubiquity, abundance and diversity of genetic parasites, the question becomes pertinent: are such parasites intrinsic to life? At least in prokaryotes, the persistence of parasites is linked to the rate of horizontal gene transfer (HGT). We mathematically derive the threshold value of the minimal transfer rate required for selfish element persistence, depending on the element duplication and loss rates as well as the cost to the host. Estimation of the characteristic gene duplication, loss and transfer rates for transposons, plasmids and virus-related elements in multiple groups of diverse bacteria and archaea indicates that most of these rates are compatible with the long term persistence of parasites. Notably, a small but non-zero rate of HGT is also required for the persistence of non-parasitic genes. We hypothesize that cells cannot tune their horizontal transfer rates to be below the threshold required for parasite persistence without experiencing highly detrimental side-effects. As a lower boundary to the minimum DNA transfer rate that a cell can withstand, we consider the process of genome degradation and mutational meltdown of populations through Muller's ratchet. A numerical assessment of this hypothesis suggests that microbial populations cannot purge parasites while escaping Muller's ratchet. Thus, genetic parasites appear to be virtually inevitable in cellular organisms.
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Affiliation(s)
- Jaime Iranzo
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda
| | - Pere Puigbò
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda Present address: Department of Biology, University of Turku, Finland
| | - Alexander E Lobkovsky
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda
| | - Yuri I Wolf
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda
| | - Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda
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154
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Booth A, Mariscal C, Doolittle WF. The Modern Synthesis in the Light of Microbial Genomics. Annu Rev Microbiol 2016; 70:279-97. [DOI: 10.1146/annurev-micro-102215-095456] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Austin Booth
- Department of Philosophy, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada;
| | - Carlos Mariscal
- Department of Philosophy, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada;
- Department of Philosophy, University of Nevada, Reno, Nevada 89557
| | - W. Ford Doolittle
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax B3H 4R2, Nova Scotia, Canada;
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155
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Pinos S, Pontarotti P, Raoult D, Baudoin JP, Pagnier I. Compartmentalization in PVC super-phylum: evolution and impact. Biol Direct 2016; 11:38. [PMID: 27507008 PMCID: PMC4977879 DOI: 10.1186/s13062-016-0144-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 08/02/2016] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND The PVC super-phylum gathers bacteria from seven phyla (Planctomycetes, Verrucomicrobiae, Chlamydiae, Lentisphaera, Poribacteria, OP3, WWE2) presenting different lifestyles, cell plans and environments. Planctomyces and several Verrucomicrobiae exhibit a complex cell plan, with an intracytoplasmic membrane inducing the compartmentalization of the cytoplasm into two regions (pirellulosome and paryphoplasm). The evolution and function of this cell plan is still subject to debate. In this work, we hypothesized that it could play a role in protection of the bacterial DNA, especially against Horizontal Genes Transfers (HGT). Therefore, 64 bacterial genomes belonging to seven different phyla (whose four PVC phyla) were studied. We reconstructed the evolution of the cell plan as precisely as possible, thanks to information obtained by bibliographic study and electronic microscopy. We used a strategy based on comparative phylogenomic in order to determine the part occupied by the horizontal transfers for each studied genomes. RESULTS Our results show that the bacteria Simkania negevensis (Chlamydiae) and Coraliomargarita akajimensis (Verrucomicrobiae), whose cell plan were unknown before, are compartmentalized, as we can see on the micrographies. This is one of the first indication of the presence of an intracytoplasmic membrane in a Chlamydiae. The proportion of HGT does not seems to be related to the cell plan of bacteria, suggesting that compartmentalization does not induce a protection of bacterial DNA against HGT. Conversely, lifestyle of bacteria seems to impact the ability of bacteria to exchange genes. CONCLUSIONS Our study allows a best reconstruction of the evolution of intracytoplasmic membrane, but this structure seems to have no impact on HGT occurrences. REVIEWERS This article was reviewed by Mircea Podar and Olivier Tenaillon.
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Affiliation(s)
- Sandrine Pinos
- Aix Marseille Université, URMITE, UM63, CNRS 7278, IRD 198, INSERM 1095, 27 Bd Jean Moulin, 13385 Marseille Cedex 5, France
- Aix Marseille Université, CNRS, Centrale Marseille, I2M UMR 7373, Evolution Biologique et Modélisation, 13385 Marseille, Cedex 5, France
| | - Pierre Pontarotti
- Aix Marseille Université, CNRS, Centrale Marseille, I2M UMR 7373, Evolution Biologique et Modélisation, 13385 Marseille, Cedex 5, France
| | - Didier Raoult
- Aix Marseille Université, URMITE, UM63, CNRS 7278, IRD 198, INSERM 1095, 27 Bd Jean Moulin, 13385 Marseille Cedex 5, France
| | - Jean Pierre Baudoin
- Aix Marseille Université, URMITE, UM63, CNRS 7278, IRD 198, INSERM 1095, 27 Bd Jean Moulin, 13385 Marseille Cedex 5, France
| | - Isabelle Pagnier
- Aix Marseille Université, URMITE, UM63, CNRS 7278, IRD 198, INSERM 1095, 27 Bd Jean Moulin, 13385 Marseille Cedex 5, France
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156
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Soo VWC, Yosaatmadja Y, Squire CJ, Patrick WM. Mechanistic and Evolutionary Insights from the Reciprocal Promiscuity of Two Pyridoxal Phosphate-dependent Enzymes. J Biol Chem 2016; 291:19873-87. [PMID: 27474741 PMCID: PMC5025676 DOI: 10.1074/jbc.m116.739557] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Indexed: 11/06/2022] Open
Abstract
Enzymes that utilize the cofactor pyridoxal 5′-phosphate play essential roles in amino acid metabolism in all organisms. The cofactor is used by proteins that adopt at least five different folds, which raises questions about the evolutionary processes that might explain the observed distribution of functions among folds. In this study, we show that a representative of fold type III, the Escherichia coli alanine racemase (ALR), is a promiscuous cystathionine β-lyase (CBL). Furthermore, E. coli CBL (fold type I) is a promiscuous alanine racemase. A single round of error-prone PCR and selection yielded variant ALR(Y274F), which catalyzes cystathionine β-elimination with a near-native Michaelis constant (Km = 3.3 mm) but a poor turnover number (kcat ≈10 h−1). In contrast, directed evolution also yielded CBL(P113S), which catalyzes l-alanine racemization with a poor Km (58 mm) but a high kcat (22 s−1). The structures of both variants were solved in the presence and absence of the l-alanine analogue, (R)-1-aminoethylphosphonic acid. As expected, the ALR active site was enlarged by the Y274F substitution, allowing better access for cystathionine. More surprisingly, the favorable kinetic parameters of CBL(P113S) appear to result from optimizing the pKa of Tyr-111, which acts as the catalytic acid during l-alanine racemization. Our data emphasize the short mutational routes between the functions of pyridoxal 5′-phosphate-dependent enzymes, regardless of whether or not they share the same fold. Thus, they confound the prevailing model of enzyme evolution, which predicts that overlapping patterns of promiscuity result from sharing a common multifunctional ancestor.
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Affiliation(s)
- Valerie W C Soo
- From the Institute of Natural and Mathematical Sciences, Massey University, Auckland 0632
| | - Yuliana Yosaatmadja
- the School of Biological Sciences, University of Auckland, Auckland 1142, and
| | | | - Wayne M Patrick
- the Department of Biochemistry, University of Otago, Dunedin 9054, New Zealand
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157
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Koonin EV. Horizontal gene transfer: essentiality and evolvability in prokaryotes, and roles in evolutionary transitions. F1000Res 2016; 5. [PMID: 27508073 PMCID: PMC4962295 DOI: 10.12688/f1000research.8737.1] [Citation(s) in RCA: 96] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 07/18/2016] [Indexed: 01/01/2023] Open
Abstract
The wide spread of gene exchange and loss in the prokaryotic world has prompted the concept of ‘lateral genomics’ to the point of an outright denial of the relevance of phylogenetic trees for evolution. However, the pronounced coherence congruence of the topologies of numerous gene trees, particularly those for (nearly) universal genes, translates into the notion of a statistical tree of life (STOL), which reflects a central trend of vertical evolution. The STOL can be employed as a framework for reconstruction of the evolutionary processes in the prokaryotic world. Quantitatively, however, horizontal gene transfer (HGT) dominates microbial evolution, with the rate of gene gain and loss being comparable to the rate of point mutations and much greater than the duplication rate. Theoretical models of evolution suggest that HGT is essential for the survival of microbial populations that otherwise deteriorate due to the Muller’s ratchet effect. Apparently, at least some bacteria and archaea evolved dedicated vehicles for gene transfer that evolved from selfish elements such as plasmids and viruses. Recent phylogenomic analyses suggest that episodes of massive HGT were pivotal for the emergence of major groups of organisms such as multiple archaeal phyla as well as eukaryotes. Similar analyses appear to indicate that, in addition to donating hundreds of genes to the emerging eukaryotic lineage, mitochondrial endosymbiosis severely curtailed HGT. These results shed new light on the routes of evolutionary transitions, but caution is due given the inherent uncertainty of deep phylogenies.
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Affiliation(s)
- Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
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158
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Tocheva EI, Ortega DR, Jensen GJ. Sporulation, bacterial cell envelopes and the origin of life. Nat Rev Microbiol 2016; 14:535-542. [PMID: 28232669 DOI: 10.1038/nrmicro.2016.85] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Electron cryotomography (ECT) enables the 3D reconstruction of intact cells in a near-native state. Images produced by ECT have led to the proposal that an ancient sporulation-like event gave rise to the second membrane in diderm bacteria. Tomograms of sporulating monoderm and diderm bacterial cells show how sporulation can lead to the generation of diderm cells. Tomograms of Gram-negative and Gram-positive cell walls and purified sacculi suggest that they are more closely related than previously thought and support the hypothesis that they share a common origin. Mapping the distribution of cell envelope architectures onto a recent phylogenetic tree of life indicates that the diderm cell plan, and therefore the sporulation-like event that gave rise to it, must be very ancient. One explanation for this model is that during the cataclysmic transitions of the early Earth, cellular evolution may have gone through a bottleneck in which only spores survived, which implies that the last bacterial common ancestor was a spore.
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Affiliation(s)
- Elitza I Tocheva
- Department of Stomatology and the Department of Biochemistry and Molecular Medicine, Université de Montréal, P. O. Box 6128 Station Centre-Ville, Montreal, Québec H3C 3J7, Canada
| | - Davi R Ortega
- Department of Biology and Biological Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA
| | - Grant J Jensen
- Howard Hughes Medical Institute, Department of Biology and Biological Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA
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159
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Koonin EV. Origin of eukaryotes from within archaea, archaeal eukaryome and bursts of gene gain: eukaryogenesis just made easier? Philos Trans R Soc Lond B Biol Sci 2016; 370:20140333. [PMID: 26323764 PMCID: PMC4571572 DOI: 10.1098/rstb.2014.0333] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The origin of eukaryotes is a fundamental, forbidding evolutionary puzzle. Comparative genomic analysis clearly shows that the last eukaryotic common ancestor (LECA) possessed most of the signature complex features of modern eukaryotic cells, in particular the mitochondria, the endomembrane system including the nucleus, an advanced cytoskeleton and the ubiquitin network. Numerous duplications of ancestral genes, e.g. DNA polymerases, RNA polymerases and proteasome subunits, also can be traced back to the LECA. Thus, the LECA was not a primitive organism and its emergence must have resulted from extensive evolution towards cellular complexity. However, the scenario of eukaryogenesis, and in particular the relationship between endosymbiosis and the origin of eukaryotes, is far from being clear. Four recent developments provide new clues to the likely routes of eukaryogenesis. First, evolutionary reconstructions suggest complex ancestors for most of the major groups of archaea, with the subsequent evolution dominated by gene loss. Second, homologues of signature eukaryotic proteins, such as actin and tubulin that form the core of the cytoskeleton or the ubiquitin system, have been detected in diverse archaea. The discovery of this ‘dispersed eukaryome’ implies that the archaeal ancestor of eukaryotes was a complex cell that might have been capable of a primitive form of phagocytosis and thus conducive to endosymbiont capture. Third, phylogenomic analyses converge on the origin of most eukaryotic genes of archaeal descent from within the archaeal evolutionary tree, specifically, the TACK superphylum. Fourth, evidence has been presented that the origin of the major archaeal phyla involved massive acquisition of bacterial genes. Taken together, these findings make the symbiogenetic scenario for the origin of eukaryotes considerably more plausible and the origin of the organizational complexity of eukaryotic cells more readily explainable than they appeared until recently.
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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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160
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Katz LA. Recent events dominate interdomain lateral gene transfers between prokaryotes and eukaryotes and, with the exception of endosymbiotic gene transfers, few ancient transfer events persist. Philos Trans R Soc Lond B Biol Sci 2016; 370:20140324. [PMID: 26323756 DOI: 10.1098/rstb.2014.0324] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
While there is compelling evidence for the impact of endosymbiotic gene transfer (EGT; transfer from either mitochondrion or chloroplast to the nucleus) on genome evolution in eukaryotes, the role of interdomain transfer from bacteria and/or archaea (i.e. prokaryotes) is less clear. Lateral gene transfers (LGTs) have been argued to be potential sources of phylogenetic information, particularly for reconstructing deep nodes that are difficult to recover with traditional phylogenetic methods. We sought to identify interdomain LGTs by using a phylogenomic pipeline that generated 13 465 single gene trees and included up to 487 eukaryotes, 303 bacteria and 118 archaea. Our goals include searching for LGTs that unite major eukaryotic clades, and describing the relative contributions of LGT and EGT across the eukaryotic tree of life. Given the difficulties in interpreting single gene trees that aim to capture the approximately 1.8 billion years of eukaryotic evolution, we focus on presence-absence data to identify interdomain transfer events. Specifically, we identify 1138 genes found only in prokaryotes and representatives of three or fewer major clades of eukaryotes (e.g. Amoebozoa, Archaeplastida, Excavata, Opisthokonta, SAR and orphan lineages). The majority of these genes have phylogenetic patterns that are consistent with recent interdomain LGTs and, with the notable exception of EGTs involving photosynthetic eukaryotes, we detect few ancient interdomain LGTs. These analyses suggest that LGTs have probably occurred throughout the history of eukaryotes, but that ancient events are not maintained unless they are associated with endosymbiotic gene transfer among photosynthetic lineages.
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Affiliation(s)
- Laura A Katz
- Department of Biological Sciences, Smith College, Northampton, MA 01063, USA Program in Organismic and Evolutionary Biology, UMass-Amherst, Amherst, MA 01003, USA
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161
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Mariscal C, Doolittle WF. Eukaryotes first: how could that be? Philos Trans R Soc Lond B Biol Sci 2016; 370:20140322. [PMID: 26323754 DOI: 10.1098/rstb.2014.0322] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In the half century since the formulation of the prokaryote : eukaryote dichotomy, many authors have proposed that the former evolved from something resembling the latter, in defiance of common (and possibly common sense) views. In such 'eukaryotes first' (EF) scenarios, the last universal common ancestor is imagined to have possessed significantly many of the complex characteristics of contemporary eukaryotes, as relics of an earlier 'progenotic' period or RNA world. Bacteria and Archaea thus must have lost these complex features secondarily, through 'streamlining'. If the canonical three-domain tree in which Archaea and Eukarya are sisters is accepted, EF entails that Bacteria and Archaea are convergently prokaryotic. We ask what this means and how it might be tested.
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Affiliation(s)
- Carlos Mariscal
- Departments of Philosophy, Dalhousie University, PO Box 15000, Halifax, Nova Scotia, Canada B3H 4R2 Biochemistry and Molecular Biology, Dalhousie University, PO Box 15000, Halifax, Nova Scotia, Canada B3H 4R2
| | - W Ford Doolittle
- Biochemistry and Molecular Biology, Dalhousie University, PO Box 15000, Halifax, Nova Scotia, Canada B3H 4R2
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162
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Foflonker F, Ananyev G, Qiu H, Morrison A, Palenik B, Dismukes GC, Bhattacharya D. The unexpected extremophile: Tolerance to fluctuating salinity in the green alga Picochlorum. ALGAL RES 2016. [DOI: 10.1016/j.algal.2016.04.003] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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163
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Lees JG, Dawson NL, Sillitoe I, Orengo CA. Functional innovation from changes in protein domains and their combinations. Curr Opin Struct Biol 2016; 38:44-52. [DOI: 10.1016/j.sbi.2016.05.016] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 05/17/2016] [Accepted: 05/24/2016] [Indexed: 10/21/2022]
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164
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Jensen L, Grant JR, Laughinghouse HD, Katz LA. Assessing the effects of a sequestered germline on interdomain lateral gene transfer in Metazoa. Evolution 2016; 70:1322-33. [DOI: 10.1111/evo.12935] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 04/04/2016] [Accepted: 04/19/2016] [Indexed: 11/26/2022]
Affiliation(s)
- Lindy Jensen
- Department of Biological Sciences; Smith College; Northampton Massachusetts 01063
- Current Address: Department of Molecular and Integrative Physiology; University of Michigan; Ann Arbor Michigan 48109
| | - Jessica R. Grant
- Department of Biological Sciences; Smith College; Northampton Massachusetts 01063
| | | | - Laura A. Katz
- Department of Biological Sciences; Smith College; Northampton Massachusetts 01063
- Program in Organismic and Evolutionary Biology; University of Massachusetts; Amherst Massachusetts 01003
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165
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O'Malley MA, Wideman JG, Ruiz-Trillo I. Losing Complexity: The Role of Simplification in Macroevolution. Trends Ecol Evol 2016; 31:608-621. [PMID: 27212432 DOI: 10.1016/j.tree.2016.04.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 04/18/2016] [Accepted: 04/19/2016] [Indexed: 10/21/2022]
Abstract
Macroevolutionary patterns can be produced by combinations of diverse and even oppositional dynamics. A growing body of data indicates that secondary simplifications of molecular and cellular structures are common. Some major diversifications in eukaryotes have occurred because of loss and minimalisation; numerous episodes in prokaryote evolution have likewise been driven by the reduction of structure. After examining a range of examples of secondary simplification and its consequences across the tree of life, we address how macroevolutionary explanations might incorporate simplification as well as complexification, and adaptive as well as nonadaptive dynamics.
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Affiliation(s)
- Maureen A O'Malley
- UMR5164, University of Bordeaux, 146 Rue Léo Saignat, Bordeaux 33076, France.
| | | | - Iñaki Ruiz-Trillo
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain; Departament de Genètica, Universitat de Barcelona, 08028 Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats, Pg Lluis Companys 23, 08010 Barcelona, Spain
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166
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Sousa FL, Nelson-Sathi S, Martin WF. One step beyond a ribosome: The ancient anaerobic core. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1027-1038. [PMID: 27150504 PMCID: PMC4906156 DOI: 10.1016/j.bbabio.2016.04.284] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 02/03/2016] [Accepted: 04/05/2016] [Indexed: 11/23/2022]
Abstract
Life arose in a world without oxygen and the first organisms were anaerobes. Here we investigate the gene repertoire of the prokaryote common ancestor, estimating which genes it contained and to which lineages of modern prokaryotes it was most similar in terms of gene content. Using a phylogenetic approach we found that among trees for all 8779 protein families shared between 134 archaea and 1847 bacterial genomes, only 1045 have sequences from at least two bacterial and two archaeal groups and retain the ancestral archaeal–bacterial split. Among those, the genes shared by anaerobes were identified as candidate genes for the prokaryote common ancestor, which lived in anaerobic environments. We find that these anaerobic prokaryote common ancestor genes are today most frequently distributed among methanogens and clostridia, strict anaerobes that live from low free energy changes near the thermodynamic limit of life. The anaerobic families encompass genes for bifunctional acetyl-CoA-synthase/CO-dehydrogenase, heterodisulfide reductase subunits C and A, ferredoxins, and several subunits of the Mrp-antiporter/hydrogenase family, in addition to numerous S-adenosyl methionine (SAM) dependent methyltransferases. The data indicate a major role for methyl groups in the metabolism of the prokaryote common ancestor. The data furthermore indicate that the prokaryote ancestor possessed a rotor stator ATP synthase, but lacked cytochromes and quinones as well as identifiable redox-dependent ion pumping complexes. The prokaryote ancestor did possess, however, an Mrp-type H+/Na+ antiporter complex, capable of transducing geochemical pH gradients into biologically more stable Na+-gradients. The findings implicate a hydrothermal, autotrophic, and methyl-dependent origin of life. This article is part of a Special Issue entitled ‘EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2–6, 2016’, edited by Prof. Paolo Bernardi. Life arose without oxygen, the universal ancestor (Luca) was an anaerobe. We used phylogenetic and physiological criteria to identify genes present in Luca. An ancient core of 65 metabolic genes shed light on Luca's anaerobic lifestyle. Ancient core genes are most widespread among modern methanogens and clostridia. The data implicate a major role for methyl groups in Luca's anaerobic metabolism.
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Affiliation(s)
- Filipa L Sousa
- Institute for Molecular Evolution, Heinrich-Heine Universität Düsseldorf, Universitätstrasse 1, 40225 Düsseldorf, Germany.
| | - Shijulal Nelson-Sathi
- Institute for Molecular Evolution, Heinrich-Heine Universität Düsseldorf, Universitätstrasse 1, 40225 Düsseldorf, Germany
| | - William F Martin
- Institute for Molecular Evolution, Heinrich-Heine Universität Düsseldorf, Universitätstrasse 1, 40225 Düsseldorf, Germany
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167
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Ślesak I, Ślesak H, Zimak-Piekarczyk P, Rozpądek P. Enzymatic Antioxidant Systems in Early Anaerobes: Theoretical Considerations. ASTROBIOLOGY 2016; 16:348-58. [PMID: 27176812 PMCID: PMC4876498 DOI: 10.1089/ast.2015.1328] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 12/01/2015] [Indexed: 05/14/2023]
Abstract
UNLABELLED It is widely accepted that cyanobacteria-dependent oxygen that was released into Earth's atmosphere ca. 2.5 billion years ago sparked the evolution of the aerobic metabolism and the antioxidant system. In modern aerobes, enzymes such as superoxide dismutases (SODs), peroxiredoxins (PXs), and catalases (CATs) constitute the core of the enzymatic antioxidant system (EAS) directed against reactive oxygen species (ROS). In many anaerobic prokaryotes, the superoxide reductases (SORs) have been identified as the main force in counteracting ROS toxicity. We found that 93% of the analyzed strict anaerobes possess at least one antioxidant enzyme, and 50% have a functional EAS, that is, consisting of at least two antioxidant enzymes: one for superoxide anion radical detoxification and another for hydrogen peroxide decomposition. The results presented here suggest that the last universal common ancestor (LUCA) was not a strict anaerobe. O2 could have been available for the first microorganisms before oxygenic photosynthesis evolved, however, from the intrinsic activity of EAS, not solely from abiotic sources. KEY WORDS Archaea-Atmospheric gases-Evolution-H2O2 resistance-Oxygenic photosynthesis. Astrobiology 16, 348-358.
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Affiliation(s)
- Ireneusz Ślesak
- The Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Kraków, Poland
| | - Halina Ślesak
- Institute of Botany, Jagiellonian University, Kraków, Poland
| | | | - Piotr Rozpądek
- The Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Kraków, Poland
- Institute of Environmental Sciences, Jagiellonian University, Kraków, Poland
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168
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Abstract
The recent increase in genomic data is revealing an unexpected perspective of gene loss as a pervasive source of genetic variation that can cause adaptive phenotypic diversity. This novel perspective of gene loss is raising new fundamental questions. How relevant has gene loss been in the divergence of phyla? How do genes change from being essential to dispensable and finally to being lost? Is gene loss mostly neutral, or can it be an effective way of adaptation? These questions are addressed, and insights are discussed from genomic studies of gene loss in populations and their relevance in evolutionary biology and biomedicine.
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169
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Abstract
A universal Tree of Life (TOL) has long been a goal of molecular phylogeneticists, but reticulation at the level of genes and possibly at the levels of cells and species renders any simple interpretation of such a TOL, especially as applied to prokaryotes, problematic.
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Affiliation(s)
- W. Ford Doolittle
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
- * E-mail:
| | - Tyler D. P. Brunet
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
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170
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Zamani-Dahaj SA, Okasha M, Kosakowski J, Higgs PG. Estimating the Frequency of Horizontal Gene Transfer Using Phylogenetic Models of Gene Gain and Loss. Mol Biol Evol 2016; 33:1843-57. [DOI: 10.1093/molbev/msw062] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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171
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Genome of Leptomonas pyrrhocoris: a high-quality reference for monoxenous trypanosomatids and new insights into evolution of Leishmania. Sci Rep 2016; 6:23704. [PMID: 27021793 PMCID: PMC4810370 DOI: 10.1038/srep23704] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 02/24/2016] [Indexed: 01/22/2023] Open
Abstract
Many high-quality genomes are available for dixenous (two hosts) trypanosomatid species of the genera Trypanosoma, Leishmania, and Phytomonas, but only fragmentary information is available for monoxenous (single-host) trypanosomatids. In trypanosomatids, monoxeny is ancestral to dixeny, thus it is anticipated that the genome sequences of the key monoxenous parasites will be instrumental for both understanding the origin of parasitism and the evolution of dixeny. Here, we present a high-quality genome for Leptomonas pyrrhocoris, which is closely related to the dixenous genus Leishmania. The L. pyrrhocoris genome (30.4 Mbp in 60 scaffolds) encodes 10,148 genes. Using the L. pyrrhocoris genome, we pinpointed genes gained in Leishmania. Among those genes, 20 genes with unknown function had expression patterns in the Leishmania mexicana life cycle suggesting their involvement in virulence. By combining differential expression data for L. mexicana, L. major and Leptomonas seymouri, we have identified several additional proteins potentially involved in virulence, including SpoU methylase and U3 small nucleolar ribonucleoprotein IMP3. The population genetics of L. pyrrhocoris was also addressed by sequencing thirteen strains of different geographic origin, allowing the identification of 1,318 genes under positive selection. This set of genes was significantly enriched in components of the cytoskeleton and the flagellum.
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172
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Beyond the Black Queen Hypothesis. ISME JOURNAL 2016; 10:2085-91. [PMID: 26953598 DOI: 10.1038/ismej.2016.22] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Revised: 01/06/2016] [Accepted: 01/08/2016] [Indexed: 11/08/2022]
Abstract
The Black Queen Hypothesis, recently proposed to explain an evolution of dependency based on gene loss, is gaining ground. This paper focuses on how the evolution of dependency transforms interactions and the community. Using agent-based modeling we suggest that species specializing in the consumption of a common good escape competition and therefore favor coexistence. This evolutionary trajectory could open the way for novel long-lasting interactions and a need to revisit the classically accepted assembly rules. Such evolutionary events also reshape the structure and dynamics of communities, depending on the spatial heterogeneity of the common good production. Let Black be the new black!
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173
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El Karkouri K, Pontarotti P, Raoult D, Fournier PE. Origin and Evolution of Rickettsial Plasmids. PLoS One 2016; 11:e0147492. [PMID: 26866478 PMCID: PMC4750851 DOI: 10.1371/journal.pone.0147492] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Accepted: 01/05/2016] [Indexed: 11/21/2022] Open
Abstract
Background Rickettsia species are strictly intracellular bacteria that have undergone a reductive genomic evolution. Despite their allopatric lifestyle, almost half of the 26 currently validated Rickettsia species have plasmids. In order to study the origin, evolutionary history and putative roles of rickettsial plasmids, we investigated the evolutionary processes that have shaped 20 plasmids belonging to 11 species, using comparative genomics and phylogenetic analysis between rickettsial, microbial and non-microbial genomes. Results Plasmids were differentially present among Rickettsia species. The 11 species had 1 to 4 plasmid (s) with a size ranging from 12 kb to 83 kb. We reconstructed pRICO, the last common ancestor of the current rickettsial plasmids. pRICO was vertically inherited mainly from Rickettsia/Orientia chromosomes and diverged vertically into a single or multiple plasmid(s) in each species. These plasmids also underwent a reductive evolution by progressive gene loss, similar to that observed in rickettsial chromosomes, possibly leading to cryptic plasmids or complete plasmid loss. Moreover, rickettsial plasmids exhibited ORFans, recent gene duplications and evidence of horizontal gene transfer events with rickettsial and non-rickettsial genomes mainly from the α/γ-proteobacteria lineages. Genes related to maintenance and plasticity of plasmids, and to adaptation and resistance to stress mostly evolved under vertical and/or horizontal processes. Those involved in nucleotide/carbohydrate transport and metabolism were under the influence of vertical evolution only, whereas genes involved in cell wall/membrane/envelope biogenesis, cycle control, amino acid/lipid/coenzyme and secondary metabolites biosynthesis, transport and metabolism underwent mainly horizontal transfer events. Conclusion Rickettsial plasmids had a complex evolution, starting with a vertical inheritance followed by a reductive evolution associated with increased complexity via horizontal gene transfer as well as gene duplication and genesis. The plasmids are plastic and mosaic structures that may play biological roles similar to or distinct from their co-residing chromosomes in an obligate intracellular lifestyle.
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Affiliation(s)
- Khalid El Karkouri
- Unité de Recherche en Maladies Infectieuses et Tropicales Emergentes (URMITE), UM63, CNRS7278, IRD198, INSERMU1095, Institut Hospitalo-Universitaire Méditerranée-Infection, Aix-Marseille Université, Faculté de Médecine, 27 boulevard Jean Moulin, 13385 Marseille cedex 5, France
| | - Pierre Pontarotti
- Aix Marseille Université, CNRS, Centrale Marseille, I2M UMR 7373, Equipe Evolution Biologique et Modélisation, Marseille, France
| | - Didier Raoult
- Unité de Recherche en Maladies Infectieuses et Tropicales Emergentes (URMITE), UM63, CNRS7278, IRD198, INSERMU1095, Institut Hospitalo-Universitaire Méditerranée-Infection, Aix-Marseille Université, Faculté de Médecine, 27 boulevard Jean Moulin, 13385 Marseille cedex 5, France
| | - Pierre-Edouard Fournier
- Unité de Recherche en Maladies Infectieuses et Tropicales Emergentes (URMITE), UM63, CNRS7278, IRD198, INSERMU1095, Institut Hospitalo-Universitaire Méditerranée-Infection, Aix-Marseille Université, Faculté de Médecine, 27 boulevard Jean Moulin, 13385 Marseille cedex 5, France
- * E-mail:
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174
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A paneukaryotic genomic analysis of the small GTPase RABL2 underscores the significance of recurrent gene loss in eukaryote evolution. Biol Direct 2016; 11:5. [PMID: 26832778 PMCID: PMC4736243 DOI: 10.1186/s13062-016-0107-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Accepted: 01/27/2016] [Indexed: 12/30/2022] Open
Abstract
Background The cilium (flagellum) is a complex cellular structure inherited from the last eukaryotic common ancestor (LECA). A large number of ciliary proteins have been characterized in a few model organisms, but their evolutionary history often remains unexplored. One such protein is the small GTPase RABL2, recently implicated in the assembly of the sperm tail in mammals. Results Using the wealth of currently available genome and transcriptome sequences, including data from our on-going sequencing projects, we systematically analyzed the phylogenetic distribution and evolutionary history of RABL2 orthologs. Our dense taxonomic sampling revealed the presence of RABL2 genes in nearly all major eukaryotic lineages, including small “obscure” taxa such as breviates, ancyromonads, malawimonads, jakobids, picozoans, or palpitomonads. The phyletic pattern of RABL2 genes indicates that it was present already in the LECA. However, some organisms lack RABL2 as a result of secondary loss and our present sampling predicts well over 30 such independent events during the eukaryote evolution. The distribution of RABL2 genes correlates with the presence/absence of cilia: not a single well-established cilium-lacking species has retained a RABL2 ortholog. However, several ciliated taxa, most notably nematodes, some arthropods and platyhelminths, diplomonads, and ciliated subgroups of apicomplexans and embryophytes, lack RABL2 as well, suggesting some simplification in their cilium-associated functions. On the other hand, several algae currently unknown to form cilia, e.g., the “prasinophytes” of the genus Prasinoderma or the ochrophytes Pelagococcus subviridis and Pinguiococcus pyrenoidosus, turned out to encode not only RABL2, but also homologs of some hallmark ciliary proteins, suggesting the existence of a cryptic flagellated stage in their life cycles. We additionally obtained insights into the evolution of the RABL2 gene architecture, which seems to have ancestrally consisted of eight exons subsequently modified not only by lineage-specific intron loss and gain, but also by recurrent loss of the terminal exon encoding a poorly conserved C-terminal extension. Conclusions Our comparative analysis supports the notion that RABL2 is an ancestral component of the eukaryotic cilium and underscores the still underappreciated magnitude of recurrent gene loss, or reductive evolution in general, in the history of eukaryotic genomes and cells. Reviewers This article was reviewed by Berend Snel and James O. McInerney. Electronic supplementary material The online version of this article (doi:10.1186/s13062-016-0107-8) contains supplementary material, which is available to authorized users.
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175
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Bloomfield G. Atypical ploidy cycles, Spo11, and the evolution of meiosis. Semin Cell Dev Biol 2016; 54:158-64. [PMID: 26811992 DOI: 10.1016/j.semcdb.2016.01.026] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 01/20/2016] [Indexed: 12/14/2022]
Abstract
The Spo11 protein induces DNA double strand breaks before the first division of meiosis, enabling the formation of the chiasmata that physically link homologous chromosomes as they align. Spo11 is an ancient and well conserved protein, related in sequence and structure to a DNA topoisomerase subunit found in Archaea as well as a subset of eukaryotes. However the origins of its meiotic function are unclear. This review examines some apparent exceptions to the rule that Spo11 activity is specific to, and required for meiosis. Spo11 appears to function in the context of unusual forms of ploidy reduction in some protists and fungi. One lineage of amoebae, the dictyostelids, is thought to undergo meiosis during its sexual cycle despite having lost Spo11 entirely. Further experimental characterisation of these and other non-canonical ploidy cycling mechanisms may cast light of the evolution of meiosis.
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Affiliation(s)
- Gareth Bloomfield
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge, CB2 0QH, United Kingdom.
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176
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Guzman C, Conaco C. Comparative transcriptome analysis reveals insights into the streamlined genomes of haplosclerid demosponges. Sci Rep 2016; 6:18774. [PMID: 26738846 PMCID: PMC4704026 DOI: 10.1038/srep18774] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 11/26/2015] [Indexed: 11/23/2022] Open
Abstract
Sponges (Porifera) are one of the most ancestral metazoan groups. They are characterized by a simple body plan lacking the true tissues and organ systems found in other animals. Members of this phylum display a remarkable diversity of form and function and yet little is known about the composition and complexity of their genomes. In this study, we sequenced the transcriptomes of two marine haplosclerid sponges belonging to Demospongiae, the largest and most diverse class within phylum Porifera, and compared their gene content with members of other sponge classes. We recovered 44,693 and 50,067 transcripts expressed in adult tissues of Haliclona amboinensis and Haliclona tubifera, respectively. These transcripts translate into 20,280 peptides in H. amboinensis and 18,000 peptides in H. tubifera. Genes associated with important signaling and metabolic pathways, regulatory networks, as well as genes that may be important in the organismal stress response, were identified in the transcriptomes. Futhermore, lineage-specific innovations were identified that may be correlated with observed sponge characters and ecological adaptations. The core gene complement expressed within the tissues of adult haplosclerid demosponges may represent a streamlined and flexible genetic toolkit that underlies the ecological success and resilience of sponges to environmental stress.
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Affiliation(s)
- Christine Guzman
- Marine Science Institute, College of Science, University of the Philippines, Diliman, Quezon City, Philippines 1101
| | - Cecilia Conaco
- Marine Science Institute, College of Science, University of the Philippines, Diliman, Quezon City, Philippines 1101
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177
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van Dijk B, Hogeweg P. In Silico Gene-Level Evolution Explains Microbial Population Diversity through Differential Gene Mobility. Genome Biol Evol 2015; 8:176-88. [PMID: 26710854 PMCID: PMC4758251 DOI: 10.1093/gbe/evv255] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Microbial communities can show astonishing ecological and phylogenetic diversity. What is the role of pervasive horizontal gene transfer (HGT) in shaping this diversity in the presence of clonally expanding “killer strains”? Does HGT of antibiotic production and resistance genes erase phylogenetic structure? To answer these questions, we study a spatial eco-evolutionary model of prokaryotes, inspired by recent findings on antagonistic interactions in Vibrionaceae populations. We find toxin genes evolve to be highly mobile, whereas resistance genes minimize mobility. This differential gene mobility is a requirement to maintain a diverse and dynamic ecosystem. The resistance gene repertoire acts as a core genome that corresponds to the phylogeny of cells, whereas toxin genes do not follow this phylogeny and have a patchy distribution. We also show that interstrain HGT makes the emergent phylogenetic structure robust to selective sweeps. Finally, in this evolved ecosystem we observe antagonistic interactions between, rather than within, spatially structure subpopulations, as has been previously observed for prokaryotes in soils and oceans. In contrast to ascribing the diversification and evolution of microbial communities to clonal dynamics, we show that multilevel evolution can elegantly explain the observed phylogenetic structure and ecosystem diversity.
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Affiliation(s)
- Bram van Dijk
- Department of Theoretical Biology and Bioinformatics, Utrecht University, The Netherlands
| | - Paulien Hogeweg
- Department of Theoretical Biology and Bioinformatics, Utrecht University, The Netherlands
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178
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Comparison of Switching and Biofilm Formation between MTL-Homozygous Strains of Candida albicans and Candida dubliniensis. EUKARYOTIC CELL 2015; 14:1186-202. [PMID: 26432632 DOI: 10.1128/ec.00146-15] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 09/23/2015] [Indexed: 11/20/2022]
Abstract
Candida albicans and Candida dubliniensis are highly related species that share the same main developmental programs. In C. albicans, it has been demonstrated that the biofilms formed by strains heterozygous and homozygous at the mating type locus (MTL) differ functionally, but studies rarely identify the MTL configuration. This becomes a particular problem in studies of C. dubliniensis, given that one-third of natural strains are MTL homozygous. For that reason, we have analyzed MTL-homozygous strains of C. dubliniensis for their capacity to switch from white to opaque, the stability of the opaque phenotype, CO2 induction of switching, pheromone induction of adhesion, the effects of minority opaque cells on biofilm thickness and dry weight, and biofilm architecture in comparison with C. albicans. Our results reveal that C. dubliniensis strains switch to opaque at lower average frequencies, exhibit a far lower level of opaque phase stability, are not stimulated to switch by high CO2, exhibit more variability in biofilm architecture, and most notably, form mature biofilms composed predominately of pseudohyphae rather than true hyphae. Therefore, while several traits of MTL-homozygous strains of C. dubliniensis appear to be degenerating or have been lost, others, most notably several related to biofilm formation, have been conserved. Within this context, the possibility is considered that C. dubliniensis is transitioning from a hypha-dominated to a pseudohypha-dominated biofilm and that aspects of C. dubliniensis colonization may provide insights into the selective pressures that are involved.
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179
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Neglected Tropical Diseases in the Post-Genomic Era. Trends Genet 2015; 31:539-555. [DOI: 10.1016/j.tig.2015.06.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 06/01/2015] [Accepted: 06/03/2015] [Indexed: 01/22/2023]
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180
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Ku C, Nelson-Sathi S, Roettger M, Sousa FL, Lockhart PJ, Bryant D, Hazkani-Covo E, McInerney JO, Landan G, Martin WF. Endosymbiotic origin and differential loss of eukaryotic genes. Nature 2015; 524:427-32. [PMID: 26287458 DOI: 10.1038/nature14963] [Citation(s) in RCA: 191] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 07/20/2015] [Indexed: 01/11/2023]
Abstract
Chloroplasts arose from cyanobacteria, mitochondria arose from proteobacteria. Both organelles have conserved their prokaryotic biochemistry, but their genomes are reduced, and most organelle proteins are encoded in the nucleus. Endosymbiotic theory posits that bacterial genes in eukaryotic genomes entered the eukaryotic lineage via organelle ancestors. It predicts episodic influx of prokaryotic genes into the eukaryotic lineage, with acquisition corresponding to endosymbiotic events. Eukaryotic genome sequences, however, increasingly implicate lateral gene transfer, both from prokaryotes to eukaryotes and among eukaryotes, as a source of gene content variation in eukaryotic genomes, which predicts continuous, lineage-specific acquisition of prokaryotic genes in divergent eukaryotic groups. Here we discriminate between these two alternatives by clustering and phylogenetic analysis of eukaryotic gene families having prokaryotic homologues. Our results indicate (1) that gene transfer from bacteria to eukaryotes is episodic, as revealed by gene distributions, and coincides with major evolutionary transitions at the origin of chloroplasts and mitochondria; (2) that gene inheritance in eukaryotes is vertical, as revealed by extensive topological comparison, sparse gene distributions stemming from differential loss; and (3) that continuous, lineage-specific lateral gene transfer, although it sometimes occurs, does not contribute to long-term gene content evolution in eukaryotic genomes.
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Affiliation(s)
- Chuan Ku
- Institute of Molecular Evolution, Heinrich-Heine University, 40225 Düsseldorf, Germany
| | - Shijulal Nelson-Sathi
- Institute of Molecular Evolution, Heinrich-Heine University, 40225 Düsseldorf, Germany
| | - Mayo Roettger
- Institute of Molecular Evolution, Heinrich-Heine University, 40225 Düsseldorf, Germany
| | - Filipa L Sousa
- Institute of Molecular Evolution, Heinrich-Heine University, 40225 Düsseldorf, Germany
| | - Peter J Lockhart
- Institute of Fundamental Sciences, Massey University, Palmerston North 4474, New Zealand
| | - David Bryant
- Department of Mathematics and Statistics, University of Otago, Dunedin 9054, New Zealand
| | - Einat Hazkani-Covo
- Department of Natural and Life Sciences, The Open University of Israel, Ra'anana 43107, Israel
| | - James O McInerney
- Department of Biology, National University of Ireland, Maynooth, County Kildare, Ireland.,Michael Smith Building, The University of Manchester, Oxford Rd, Manchester M13 9PL, UK
| | - Giddy Landan
- Genomic Microbiology Group, Institute of Microbiology, Christian-Albrechts-University of Kiel, 24118 Kiel, Germany
| | - William F Martin
- Institute of Molecular Evolution, Heinrich-Heine University, 40225 Düsseldorf, Germany.,Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2780-157 Oeiras, Portugal
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181
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Black Queen evolution: the role of leakiness in structuring microbial communities. Trends Genet 2015; 31:475-82. [DOI: 10.1016/j.tig.2015.05.004] [Citation(s) in RCA: 141] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 05/11/2015] [Accepted: 05/12/2015] [Indexed: 11/21/2022]
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182
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Qiu H, Price DC, Yang EC, Yoon HS, Bhattacharya D. Evidence of ancient genome reduction in red algae (Rhodophyta). JOURNAL OF PHYCOLOGY 2015; 51:624-36. [PMID: 26986787 DOI: 10.1111/jpy.12294] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Accepted: 01/30/2015] [Indexed: 05/27/2023]
Abstract
Red algae (Rhodophyta) comprise a monophyletic eukaryotic lineage of ~6,500 species with a fossil record that extends back 1.2 billion years. A surprising aspect of red algal evolution is that sequenced genomes encode a relatively limited gene inventory (~5-10 thousand genes) when compared with other free-living algae or to other eukaryotes. This suggests that the common ancestor of red algae may have undergone extensive genome reduction, which can result from lineage specialization to a symbiotic or parasitic lifestyle or adaptation to an extreme or oligotrophic environment. We gathered genome and transcriptome data from a total of 14 red algal genera that represent the major branches of this phylum to study genome evolution in Rhodophyta. Analysis of orthologous gene gains and losses identifies two putative major phases of genome reduction: (i) in the stem lineage leading to all red algae resulting in the loss of major functions such as flagellae and basal bodies, the glycosyl-phosphatidylinositol anchor biosynthesis pathway, and the autophagy regulation pathway; and (ii) in the common ancestor of the extremophilic Cyanidiophytina. Red algal genomes are also characterized by the recruitment of hundreds of bacterial genes through horizontal gene transfer that have taken on multiple functions in shared pathways and have replaced eukaryotic gene homologs. Our results suggest that Rhodophyta may trace their origin to a gene depauperate ancestor. Unlike plants, it appears that a limited gene inventory is sufficient to support the diversification of a major eukaryote lineage that possesses sophisticated multicellular reproductive structures and an elaborate triphasic sexual cycle.
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Affiliation(s)
- Huan Qiu
- Department of Ecology, Evolution and Natural Resources, Rutgers University, New Brunswick, New Jersey, 08901, USA
| | - Dana C Price
- Department of Ecology, Evolution and Natural Resources, Rutgers University, New Brunswick, New Jersey, 08901, USA
| | - Eun Chan Yang
- Marine Ecosystem Research Division, Korea Institute of Ocean Sciences & Technology, 787 Haeanro, Ansan, 426-744, Korea
| | - Hwan Su Yoon
- Department of Biological Sciences, Sungkyunkwan University, Suwon, 440-746, Korea
| | - Debashish Bhattacharya
- Department of Ecology, Evolution and Natural Resources, Rutgers University, New Brunswick, New Jersey, 08901, USA
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183
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Goncearenco A, Shaytan AK, Shoemaker BA, Panchenko AR. Structural Perspectives on the Evolutionary Expansion of Unique Protein-Protein Binding Sites. Biophys J 2015. [PMID: 26213149 DOI: 10.1016/j.bpj.2015.06.056] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Structures of protein complexes provide atomistic insights into protein interactions. Human proteins represent a quarter of all structures in the Protein Data Bank; however, available protein complexes cover less than 10% of the human proteome. Although it is theoretically possible to infer interactions in human proteins based on structures of homologous protein complexes, it is still unclear to what extent protein interactions and binding sites are conserved, and whether protein complexes from remotely related species can be used to infer interactions and binding sites. We considered biological units of protein complexes and clustered protein-protein binding sites into similarity groups based on their structure and sequence, which allowed us to identify unique binding sites. We showed that the growth rate of the number of unique binding sites in the Protein Data Bank was much slower than the growth rate of the number of structural complexes. Next, we investigated the evolutionary roots of unique binding sites and identified the major phyletic branches with the largest expansion in the number of novel binding sites. We found that many binding sites could be traced to the universal common ancestor of all cellular organisms, whereas relatively few binding sites emerged at the major evolutionary branching points. We analyzed the physicochemical properties of unique binding sites and found that the most ancient sites were the largest in size, involved many salt bridges, and were the most compact and least planar. In contrast, binding sites that appeared more recently in the evolution of eukaryotes were characterized by a larger fraction of polar and aromatic residues, and were less compact and more planar, possibly due to their more transient nature and roles in signaling processes.
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Affiliation(s)
- Alexander Goncearenco
- Computational Biology Branch of the National Center for Biotechnology Information, Bethesda, Maryland
| | - Alexey K Shaytan
- Computational Biology Branch of the National Center for Biotechnology Information, Bethesda, Maryland
| | - Benjamin A Shoemaker
- Computational Biology Branch of the National Center for Biotechnology Information, Bethesda, Maryland
| | - Anna R Panchenko
- Computational Biology Branch of the National Center for Biotechnology Information, Bethesda, Maryland.
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184
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Koonin EV. The Turbulent Network Dynamics of Microbial Evolution and the Statistical Tree of Life. J Mol Evol 2015; 80:244-50. [PMID: 25894542 PMCID: PMC4472940 DOI: 10.1007/s00239-015-9679-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 04/08/2015] [Indexed: 08/30/2023]
Abstract
The wide spread and high rate of gene exchange and loss in the prokaryotic world translate into “network genomics”. The rates of gene gain and loss are comparable with the rate of point mutations but are substantially greater than the duplication rate. Thus, evolution of prokaryotes is primarily shaped by gene gain and loss. These processes are essential to prevent mutational meltdown of microbial populations by stopping Muller’s ratchet and appear to trigger emergence of major novel clades by opening up new ecological niches. At least some bacteria and archaea seem to have evolved dedicated devices for gene transfer. Despite the dominance of gene gain and loss, evolution of genes is intrinsically tree-like. The significant coherence between the topologies of numerous gene trees, particularly those for (nearly) universal genes, is compatible with the concept of a statistical tree of life, which forms the framework for reconstruction of the evolutionary processes in the prokaryotic world.
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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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185
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Metabolic Cycles in Yeast Share Features Conserved among Circadian Rhythms. Curr Biol 2015; 25:1056-62. [PMID: 25866393 PMCID: PMC4406945 DOI: 10.1016/j.cub.2015.02.035] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 12/17/2014] [Accepted: 02/09/2015] [Indexed: 01/22/2023]
Abstract
Cell-autonomous circadian rhythms allow organisms to temporally orchestrate their internal state to anticipate and/or resonate with the external environment [1, 2]. Although ∼24-hr periodicity is observed across aerobic eukaryotes, the central mechanism has been hard to dissect because few simple models exist, and known clock proteins are not conserved across phylogenetic kingdoms [1, 3, 4]. In contrast, contributions to circadian rhythmicity made by a handful of post-translational mechanisms, such as phosphorylation of clock proteins by casein kinase 1 (CK1) and glycogen synthase kinase 3 (GSK3), appear conserved among phyla [3, 5]. These kinases have many other essential cellular functions and are better conserved in their contribution to timekeeping than any of the clock proteins they phosphorylate [6]. Rhythmic oscillations in cellular redox state are another universal feature of circadian timekeeping, e.g., over-oxidation cycles of abundant peroxiredoxin proteins [7–9]. Here, we use comparative chronobiology to distinguish fundamental clock mechanisms from species and/or tissue-specific adaptations and thereby identify features shared between circadian rhythms in mammalian cells and non-circadian temperature-compensated respiratory oscillations in budding yeast [10]. We find that both types of oscillations are coupled with the cell division cycle, exhibit period determination by CK1 and GSK3, and have peroxiredoxin over-oxidation cycles. We also explore how peroxiredoxins contribute to YROs. Our data point to common mechanisms underlying both YROs and circadian rhythms and suggest two interpretations: either certain biochemical systems are simply permissive for cellular oscillations (with frequencies from hours to days) or this commonality arose via divergence from an ancestral cellular clock. Yeast respiratory oscillations (YROs) share features with circadian rhythms Changes that alter the period of circadian rhythms have the same effect on YROs Oxidation cycles of peroxiredoxins are a characteristic of both oscillations Mechanistic similarities between these cycles may reflect a common origin
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Endosymbiotic gene transfer from prokaryotic pangenomes: Inherited chimerism in eukaryotes. Proc Natl Acad Sci U S A 2015; 112:10139-46. [PMID: 25733873 DOI: 10.1073/pnas.1421385112] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Endosymbiotic theory in eukaryotic-cell evolution rests upon a foundation of three cornerstone partners--the plastid (a cyanobacterium), the mitochondrion (a proteobacterium), and its host (an archaeon)--and carries a corollary that, over time, the majority of genes once present in the organelle genomes were relinquished to the chromosomes of the host (endosymbiotic gene transfer). However, notwithstanding eukaryote-specific gene inventions, single-gene phylogenies have never traced eukaryotic genes to three single prokaryotic sources, an issue that hinges crucially upon factors influencing phylogenetic inference. In the age of genomes, single-gene trees, once used to test the predictions of endosymbiotic theory, now spawn new theories that stand to eventually replace endosymbiotic theory with descriptive, gene tree-based variants featuring supernumerary symbionts: prokaryotic partners distinct from the cornerstone trio and whose existence is inferred solely from single-gene trees. We reason that the endosymbiotic ancestors of mitochondria and chloroplasts brought into the eukaryotic--and plant and algal--lineage a genome-sized sample of genes from the proteobacterial and cyanobacterial pangenomes of their respective day and that, even if molecular phylogeny were artifact-free, sampling prokaryotic pangenomes through endosymbiotic gene transfer would lead to inherited chimerism. Recombination in prokaryotes (transduction, conjugation, transformation) differs from recombination in eukaryotes (sex). Prokaryotic recombination leads to pangenomes, and eukaryotic recombination leads to vertical inheritance. Viewed from the perspective of endosymbiotic theory, the critical transition at the eukaryote origin that allowed escape from Muller's ratchet--the origin of eukaryotic recombination, or sex--might have required surprisingly little evolutionary innovation.
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187
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Abstract
tRNAs are widely believed to segregate into two classes, I and II. Computational analysis of eukaryotic tRNA entries in Genomic tRNA Database, however, leads to new, albeit paradoxical, presence of more than a thousand class-I tRNAs with uncharacteristic long variable arms (V-arms), like in class-II. Out of 62,202 tRNAs from 69 eukaryotes, as many as 1431 class-I tRNAs have these novel extended V-arms, and we refer to them as paradoxical tRNAs (pxtRNAs). A great majority of these 1431 pxtRNA genes are located in intergenic regions, about 18% embedded in introns of genes or ESTs, and just one in 3'UTR. A check on the conservations of 2D and 3D base pairs for each position of these pxtRNAs reveals a few variations, but they seem to have almost all the known features (already known identity and conserved elements of tRNA). Analyses of the A-Box and B-Box of these pxtRNA genes in eukaryotes display salient deviations from the previously annotated conserved features of the standard promoters, whereas the transcription termination signals are just canonical and non-canonical runs of thymidine, similar to the ones in standard tRNA genes. There is just one such pxtRNA(ProAGG) gene in the entire human genome, and the availability of data allows epigenetic analysis of this human pxtRNA(ProAGG) in three different cell lines, H1 hESC, K562, and NHEK, to assess the level of its expression. Histone acetylation and methylation of this lone pxtRNA(ProAGG) gene in human differ from that of the nine standard human tRNA(ProAGG) genes. The V-arm nucleotide sequences and their secondary structures in pxtRNA differ from that of class-II tRNA. Considering these differences, hypotheses of alternative splicing, non-canonical intron and gene transfer are examined to partially improve the Cove scores of these pxtRNAs and to critically question their antecedence and novelty.
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Affiliation(s)
- Sanga Mitra
- a Computational Biology Group , Indian Association for the Cultivation of Science , Jadavpur, Kolkata 700032 , India
| | - Arpa Samadder
- a Computational Biology Group , Indian Association for the Cultivation of Science , Jadavpur, Kolkata 700032 , India
| | - Pijush Das
- b Cancer Biology & Inflammatory Disorder Division , Indian Institute of Chemical Biology , Kolkata , India
| | - Smarajit Das
- c Department of Medical Biochemistry and Cell Biology , Institute of Biomedicine, University of Gothenburg , Gothenburg , Sweden
| | - Jayprokas Chakrabarti
- a Computational Biology Group , Indian Association for the Cultivation of Science , Jadavpur, Kolkata 700032 , India.,d Gyanxet, BF 286 Salt Lake, Kolkata , India
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Genomic and proteomic characterization of "Candidatus Nitrosopelagicus brevis": an ammonia-oxidizing archaeon from the open ocean. Proc Natl Acad Sci U S A 2015; 112:1173-8. [PMID: 25587132 DOI: 10.1073/pnas.1416223112] [Citation(s) in RCA: 151] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Thaumarchaeota are among the most abundant microbial cells in the ocean, but difficulty in cultivating marine Thaumarchaeota has hindered investigation into the physiological and evolutionary basis of their success. We report here a closed genome assembled from a highly enriched culture of the ammonia-oxidizing pelagic thaumarchaeon CN25, originating from the open ocean. The CN25 genome exhibits strong evidence of genome streamlining, including a 1.23-Mbp genome, a high coding density, and a low number of paralogous genes. Proteomic analysis recovered nearly 70% of the predicted proteins encoded by the genome, demonstrating that a high fraction of the genome is translated. In contrast to other minimal marine microbes that acquire, rather than synthesize, cofactors, CN25 encodes and expresses near-complete biosynthetic pathways for multiple vitamins. Metagenomic fragment recruitment indicated the presence of DNA sequences >90% identical to the CN25 genome throughout the oligotrophic ocean. We propose the provisional name "Candidatus Nitrosopelagicus brevis" str. CN25 for this minimalist marine thaumarchaeon and suggest it as a potential model system for understanding archaeal adaptation to the open ocean.
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189
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Sebé-Pedrós A, Grau-Bové X, Richards TA, Ruiz-Trillo I. Evolution and classification of myosins, a paneukaryotic whole-genome approach. Genome Biol Evol 2015; 6:290-305. [PMID: 24443438 PMCID: PMC3942036 DOI: 10.1093/gbe/evu013] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Myosins are key components of the eukaryotic cytoskeleton, providing motility for a broad diversity of cargoes. Therefore, understanding the origin and evolutionary history of myosin classes is crucial to address the evolution of eukaryote cell biology. Here, we revise the classification of myosins using an updated taxon sampling that includes newly or recently sequenced genomes and transcriptomes from key taxa. We performed a survey of eukaryotic genomes and phylogenetic analyses of the myosin gene family, reconstructing the myosin toolkit at different key nodes in the eukaryotic tree of life. We also identified the phylogenetic distribution of myosin diversity in terms of number of genes, associated protein domains and number of classes in each taxa. Our analyses show that new classes (i.e., paralogs) and domain architectures were continuously generated throughout eukaryote evolution, with a significant expansion of myosin abundance and domain architectural diversity at the stem of Holozoa, predating the origin of animal multicellularity. Indeed, single-celled holozoans have the most complex myosin complement among eukaryotes, with paralogs of most myosins previously considered animal specific. We recover a dynamic evolutionary history, with several lineage-specific expansions (e.g., the myosin III-like gene family diversification in choanoflagellates), convergence in protein domain architectures (e.g., fungal and animal chitin synthase myosins), and important secondary losses. Overall, our evolutionary scheme demonstrates that the ancestral eukaryote likely had a complex myosin repertoire that included six genes with different protein domain architectures. Finally, we provide an integrative and robust classification, useful for future genomic and functional studies on this crucial eukaryotic gene family.
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Affiliation(s)
- Arnau Sebé-Pedrós
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Passeig Marítim de la Barceloneta, Barcelona, Catalonia, Spain
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190
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Grau-Bové X, Sebé-Pedrós A, Ruiz-Trillo I. The eukaryotic ancestor had a complex ubiquitin signaling system of archaeal origin. Mol Biol Evol 2014; 32:726-39. [PMID: 25525215 PMCID: PMC4327156 DOI: 10.1093/molbev/msu334] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The origin of the eukaryotic cell is one of the most important transitions in the history of life. However, the emergence and early evolution of eukaryotes remains poorly understood. Recent data have shown that the last eukaryotic common ancestor (LECA) was much more complex than previously thought. The LECA already had the genetic machinery encoding the endomembrane apparatus, spliceosome, nuclear pore, and myosin and kinesin cytoskeletal motors. It is unclear, however, when the functional regulation of these cellular components evolved. Here, we address this question by analyzing the origin and evolution of the ubiquitin (Ub) signaling system, one of the most important regulatory layers in eukaryotes. We delineated the evolution of the whole Ub, Small-Ub-related MOdifier (SUMO), and Ub-fold modifier 1 (Ufm1) signaling networks by analyzing representatives from all major eukaryotic, bacterial, and archaeal lineages. We found that the Ub toolkit had a pre-eukaryotic origin and is present in three extant archaeal groups. The pre-eukaryotic Ub toolkit greatly expanded during eukaryogenesis, through massive gene innovation and diversification of protein domain architectures. This resulted in a LECA with essentially all of the Ub-related genes, including the SUMO and Ufm1 Ub-like systems. Ub and SUMO signaling further expanded during eukaryotic evolution, especially labeling and delabeling enzymes responsible for substrate selection. Additionally, we analyzed protein domain architecture evolution and found that multicellular lineages have the most complex Ub systems in terms of domain architectures. Together, we demonstrate that the Ub system predates the origin of eukaryotes and that a burst of innovation during eukaryogenesis led to a LECA with complex posttranslational regulation.
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Affiliation(s)
- Xavier Grau-Bové
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Spain
| | - Arnau Sebé-Pedrós
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Spain
| | - Iñaki Ruiz-Trillo
- Institut de Biologia Evolutiva (CSIC-Universitat Pompeu Fabra), Barcelona, Spain Departament de Genètica, Universitat de Barcelona, Barcelona, Spain Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
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191
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Wuichet K, Søgaard-Andersen L. Evolution and diversity of the Ras superfamily of small GTPases in prokaryotes. Genome Biol Evol 2014; 7:57-70. [PMID: 25480683 PMCID: PMC4316618 DOI: 10.1093/gbe/evu264] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The Ras superfamily of small GTPases are single domain nucleotide-dependent molecular switches that act as highly tuned regulators of complex signal transduction pathways. Originally identified in eukaryotes for their roles in fundamental cellular processes including proliferation, motility, polarity, nuclear transport, and vesicle transport, recent studies have revealed that single domain GTPases also control complex functions such as cell polarity, motility, predation, development and antibiotic resistance in bacteria. Here, we used a computational genomics approach to understand the abundance, diversity, and evolution of small GTPases in prokaryotes. We collected 520 small GTPase sequences present in 17% of 1,611 prokaryotic genomes analyzed that cover diverse lineages. We identified two discrete families of small GTPases in prokaryotes that show evidence of three distinct catalytic mechanisms. The MglA family includes MglA homologs, which are typically associated with the MglB GTPase activating protein, whereas members of the Rup (Ras superfamily GTPase of unknown function in prokaryotes) family are not predicted to interact with MglB homologs. System classification and genome context analyses support the involvement of small GTPases in diverse prokaryotic signal transduction pathways including two component systems, laying the foundation for future experimental characterization of these proteins. Phylogenetic analysis of prokaryotic and eukaryotic GTPases supports that the last universal common ancestor contained ancestral MglA and Rup family members. We propose that the MglA family was lost from the ancestral eukaryote and that the Ras superfamily members in extant eukaryotes are the result of vertical and horizontal gene transfer events of ancestral Rup GTPases.
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Affiliation(s)
- Kristin Wuichet
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Lotte Søgaard-Andersen
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
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192
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The lineage-specific evolution of aquaporin gene clusters facilitated tetrapod terrestrial adaptation. PLoS One 2014; 9:e113686. [PMID: 25426855 PMCID: PMC4245216 DOI: 10.1371/journal.pone.0113686] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 10/27/2014] [Indexed: 01/02/2023] Open
Abstract
A major physiological barrier for aquatic organisms adapting to terrestrial life is dessication in the aerial environment. This barrier was nevertheless overcome by the Devonian ancestors of extant Tetrapoda, but the origin of specific molecular mechanisms that solved this water problem remains largely unknown. Here we show that an ancient aquaporin gene cluster evolved specifically in the sarcopterygian lineage, and subsequently diverged into paralogous forms of AQP2, -5, or -6 to mediate water conservation in extant Tetrapoda. To determine the origin of these apomorphic genomic traits, we combined aquaporin sequencing from jawless and jawed vertebrates with broad taxon assembly of >2,000 transcripts amongst 131 deuterostome genomes and developed a model based upon Bayesian inference that traces their convergent roots to stem subfamilies in basal Metazoa and Prokaryota. This approach uncovered an unexpected diversity of aquaporins in every lineage investigated, and revealed that the vertebrate superfamily consists of 17 classes of aquaporins (Aqp0 - Aqp16). The oldest orthologs associated with water conservation in modern Tetrapoda are traced to a cluster of three aqp2-like genes in Actinistia that likely arose >500 Ma through duplication of an aqp0-like gene present in a jawless ancestor. In sea lamprey, we show that aqp0 first arose in a protocluster comprised of a novel aqp14 paralog and a fused aqp01 gene. To corroborate these findings, we conducted phylogenetic analyses of five syntenic nuclear receptor subfamilies, which, together with observations of extensive genome rearrangements, support the coincident loss of ancestral aqp2-like orthologs in Actinopterygii. We thus conclude that the divergence of sarcopterygian-specific aquaporin gene clusters was permissive for the evolution of water conservation mechanisms that facilitated tetrapod terrestrial adaptation.
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193
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Stolzer M, Wasserman L, Durand D. Robustness of birth-death and gain models for inferring evolutionary events. BMC Genomics 2014; 15 Suppl 6:S9. [PMID: 25572914 PMCID: PMC4239551 DOI: 10.1186/1471-2164-15-s6-s9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Background Phylogenetic birth-death models are opening a new window on the processes of genome evolution in studies of the evolution of gene and protein families, protein-protein interaction networks, microRNAs, and copy number variation. Given a species tree and a set of genomic characters in present-day species, the birth-death approach estimates the most likely rates required to explain the observed data and returns the expected ancestral character states and the history of character state changes. Achieving a balance between model complexity and generalizability is a fundamental challenge in the application of birth-death models. While more parameters promise greater accuracy and more biologically realistic models, increasing model complexity can lead to overfitting and a heavy computational cost. Results Here we present a systematic, empirical investigation of these tradeoffs, using protein domain families in six metazoan genomes as a case study. We compared models of increasing complexity, implemented in the Count program, with respect to model fit, robustness, and stability. In addition, we used a bootstrapping procedure to assess estimator variability. The results show that the most complex model, which allows for both branch-specific and family-specific rate variation, achieves the best fit, without overfitting. Variance remains low with increasing complexity, except for family-specific loss rates. This variance is reduced when the number of discrete rate categories is increased. Model choice is of greatest concern when different models lead to fundamentally different outcomes. To investigate the extent to which model choice influences biological interpretation, ancestral states and expected events were inferred under each model. Disturbingly, the different models not only resulted in quantitatively different histories, but predicted qualitatively different patterns of domain family turnover and genome expansion and reduction. Conclusions The work presented here evaluates model choice for genomic birth-death models in a systematic way and presents the first use of bootstrapping to assess estimator variance in birth-death models. We find that a model incorporating both lineage and family rate variation yields more accurate estimators without sacrificing generality. Our results indicate that model choice can lead to fundamentally different evolutionary conclusions, emphasizing the importance of more biologically realistic and complex models.
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194
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Origins of major archaeal clades correspond to gene acquisitions from bacteria. Nature 2014; 517:77-80. [PMID: 25317564 PMCID: PMC4285555 DOI: 10.1038/nature13805] [Citation(s) in RCA: 164] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 08/28/2014] [Indexed: 01/28/2023]
Abstract
The mechanisms that underlie the origin of major prokaryotic groups are poorly understood. In principle, the origin of both species and higher taxa among prokaryotes should entail similar mechanisms — ecological interactions with the environment paired with natural genetic variation involving lineage-specific gene innovations and lineage-specific gene acquisitions1,2,3,4. To investigate the origin of higher taxa in archaea, we have determined gene distributions and gene phylogenies for the 267,568 protein coding genes of 134 sequenced archaeal genomes in the context of their homologs from 1,847 reference bacterial genomes. Archaea-specific gene families define 13 traditionally recognized archaeal higher taxa in our sample. Here we report that the origins of these 13 groups unexpectedly correspond to 2,264 group-specific gene acquisitions from bacteria. Interdomain gene transfer is highly asymmetric, transfers from bacteria to archaea are more than 5-fold more frequent than vice versa. Gene transfers identified at major evolutionary transitions among prokaryotes specifically implicate gene acquisitions for metabolic functions from bacteria as key innovations in the origin of higher archaeal taxa.
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195
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Adams J, Rosenzweig F. Experimental microbial evolution: history and conceptual underpinnings. Genomics 2014; 104:393-8. [PMID: 25315137 DOI: 10.1016/j.ygeno.2014.10.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 10/06/2014] [Indexed: 01/10/2023]
Abstract
We chronicle and dissect the history of the field of Experimental Microbial Evolution, beginning with work by Monod. Early research was largely carried out by microbiologists and biochemists, who used experimental evolutionary change as a tool to understand structure-function relationships. These studies attracted the interest of evolutionary biologists who recognized the power of the approach to address issues such as the tempo of adaptive change, the costs and benefits of sex, parallelism, and the role which contingency plays in the evolutionary process. In the 1980s and 1990s, an ever-expanding body of microbial, physiological and biochemical data, together with new technologies for manipulating microbial genomes, allowed such questions to be addressed in ever-increasing detail. Since then, technological advances leading to low-cost, high-throughput DNA sequencing have made it possible for these and other fundamental questions in evolutionary biology to be addressed at the molecular level.
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Affiliation(s)
- Julian Adams
- Department of Molecular, Cellular and Developmental Biology, Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Frank Rosenzweig
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
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196
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Zimorski V, Ku C, Martin WF, Gould SB. Endosymbiotic theory for organelle origins. Curr Opin Microbiol 2014; 22:38-48. [PMID: 25306530 DOI: 10.1016/j.mib.2014.09.008] [Citation(s) in RCA: 247] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 09/01/2014] [Accepted: 09/12/2014] [Indexed: 11/19/2022]
Abstract
Endosymbiotic theory goes back over 100 years. It explains the similarity of chloroplasts and mitochondria to free-living prokaryotes by suggesting that the organelles arose from prokaryotes through (endo)symbiosis. Gene trees provide important evidence in favour of symbiotic theory at a coarse-grained level, but the finer we get into the details of branches in trees containing dozens or hundreds of taxa, the more equivocal evidence for endosymbiotic events sometimes becomes. It seems that either the interpretation of some endosymbiotic events are wrong, or something is wrong with the interpretations of some gene trees having many leaves. There is a need for evidence that is independent of gene trees and that can help outline the course of symbiosis in eukaryote evolution. Protein import is the strongest evidence we have for the single origin of chloroplasts and mitochondria. It is probably also the strongest evidence we have to sort out the number and nature of secondary endosymbiotic events that have occurred in evolution involving the red plastid lineage. If we relax our interpretation of individual gene trees, endosymbiotic theory can tell us a lot.
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Affiliation(s)
- Verena Zimorski
- Institute of Molecular Evolution, Heinrich-Heine-University of Düsseldorf, 40225 Düsseldorf, Germany
| | - Chuan Ku
- Institute of Molecular Evolution, Heinrich-Heine-University of Düsseldorf, 40225 Düsseldorf, Germany
| | - William F Martin
- Institute of Molecular Evolution, Heinrich-Heine-University of Düsseldorf, 40225 Düsseldorf, Germany.
| | - Sven B Gould
- Institute of Molecular Evolution, Heinrich-Heine-University of Düsseldorf, 40225 Düsseldorf, Germany
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197
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Grant JR, Katz LA. Phylogenomic study indicates widespread lateral gene transfer in Entamoeba and suggests a past intimate relationship with parabasalids. Genome Biol Evol 2014; 6:2350-60. [PMID: 25146649 PMCID: PMC4217692 DOI: 10.1093/gbe/evu179] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/14/2014] [Indexed: 12/13/2022] Open
Abstract
Lateral gene transfer (LGT) has impacted the evolutionary history of eukaryotes, though to a lesser extent than in bacteria and archaea. Detecting LGT and distinguishing it from single gene tree artifacts is difficult, particularly when considering very ancient events (i.e., over hundreds of millions of years). Here, we use two independent lines of evidence--a taxon-rich phylogenetic approach and an assessment of the patterns of gene presence/absence--to evaluate the extent of LGT in the parasitic amoebozoan genus Entamoeba. Previous work has suggested that a number of genes in the genome of Entamoeba spp. were acquired by LGT. Our approach, using an automated phylogenomic pipeline to build taxon-rich gene trees, suggests that LGT is more extensive than previously thought. Our analyses reveal that genes have frequently entered the Entamoeba genome via nonvertical events, including at least 116 genes acquired directly from bacteria or archaea, plus an additional 22 genes in which Entamoeba plus one other eukaryote are nested among bacteria and/or archaea. These genes may make good candidates for novel therapeutics, as drugs targeting these genes are less likely to impact the human host. Although we recognize the challenges of inferring intradomain transfers given systematic errors in gene trees, we find 109 genes supporting LGT from a eukaryote to Entamoeba spp., and 178 genes unique to Entamoeba spp. and one other eukaryotic taxon (i.e., presence/absence data). Inspection of these intradomain LGTs provide evidence of a common sister relationship between genes of Entamoeba (Amoebozoa) and parabasalids (Excavata). We speculate that this indicates a past close relationship (e.g., symbiosis) between ancestors of these extant lineages.
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Affiliation(s)
- Jessica R Grant
- Department of Biological Sciences, Smith College, Northampton, MA
| | - Laura A Katz
- Department of Biological Sciences, Smith College, Northampton, MA Program in Organismic and Evolutionary Biology, University of Massachusetts
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198
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Puigbò P, Lobkovsky AE, Kristensen DM, Wolf YI, Koonin EV. Genomes in turmoil: quantification of genome dynamics in prokaryote supergenomes. BMC Biol 2014; 12:66. [PMID: 25141959 PMCID: PMC4166000 DOI: 10.1186/s12915-014-0066-4] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 07/31/2014] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND Genomes of bacteria and archaea (collectively, prokaryotes) appear to exist in incessant flux, expanding via horizontal gene transfer and gene duplication, and contracting via gene loss. However, the actual rates of genome dynamics and relative contributions of different types of event across the diversity of prokaryotes are largely unknown, as are the sizes of microbial supergenomes, i.e. pools of genes that are accessible to the given microbial species. RESULTS We performed a comprehensive analysis of the genome dynamics in 35 groups (34 bacterial and one archaeal) of closely related microbial genomes using a phylogenetic birth-and-death maximum likelihood model to quantify the rates of gene family gain and loss, as well as expansion and reduction. The results show that loss of gene families dominates the evolution of prokaryotes, occurring at approximately three times the rate of gain. The rates of gene family expansion and reduction are typically seven and twenty times less than the gain and loss rates, respectively. Thus, the prevailing mode of evolution in bacteria and archaea is genome contraction, which is partially compensated by the gain of new gene families via horizontal gene transfer. However, the rates of gene family gain, loss, expansion and reduction vary within wide ranges, with the most stable genomes showing rates about 25 times lower than the most dynamic genomes. For many groups, the supergenome estimated from the fraction of repetitive gene family gains includes about tenfold more gene families than the typical genome in the group although some groups appear to have vast, 'open' supergenomes. CONCLUSIONS Reconstruction of evolution for groups of closely related bacteria and archaea reveals an extremely rapid and highly variable flux of genes in evolving microbial genomes, demonstrates that extensive gene loss and horizontal gene transfer leading to innovation are the two dominant evolutionary processes, and yields robust estimates of the supergenome size.
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199
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Cissé OH, Pagni M, Hauser PM. Comparative genomics suggests that the human pathogenic fungus Pneumocystis jirovecii acquired obligate biotrophy through gene loss. Genome Biol Evol 2014; 6:1938-48. [PMID: 25062922 PMCID: PMC4159005 DOI: 10.1093/gbe/evu155] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Pneumocystis jirovecii is a fungal parasite that colonizes specifically humans and turns into an opportunistic pathogen in immunodeficient individuals. The fungus is able to reproduce extracellularly in host lungs without eliciting massive cellular death. The molecular mechanisms that govern this process are poorly understood, in part because of the lack of an in vitro culture system for Pneumocystis spp. In this study, we explored the origin and evolution of the putative biotrophy of P. jirovecii through comparative genomics and reconstruction of ancestral gene repertoires. We used the maximum parsimony method and genomes of related fungi of the Taphrinomycotina subphylum. Our results suggest that the last common ancestor of Pneumocystis spp. lost 2,324 genes in relation to the acquisition of obligate biotrophy. These losses may result from neutral drift and affect the biosyntheses of amino acids and thiamine, the assimilation of inorganic nitrogen and sulfur, and the catabolism of purines. In addition, P. jirovecii shows a reduced panel of lytic proteases and has lost the RNA interference machinery, which might contribute to its genome plasticity. Together with other characteristics, that is, a sex life cycle within the host, the absence of massive destruction of host cells, difficult culturing, and the lack of virulence factors, these gene losses constitute a unique combination of characteristics which are hallmarks of both obligate biotrophs and animal parasites. These findings suggest that Pneumocystis spp. should be considered as the first described obligate biotrophs of animals, whose evolution has been marked by gene losses.
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Affiliation(s)
- Ousmane H Cissé
- Institute of Microbiology, Centre Hospitalier Universitaire Vaudois and University of Lausanne, SwitzerlandVital-IT Group, SIB Swiss Institute of Bioinformatics, Lausanne, SwitzerlandPresent address: Department of Plant Pathology & Microbiology and Institute for Integrative Genome Biology, University of California, Riverside, CA
| | - Marco Pagni
- Vital-IT Group, SIB Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Philippe M Hauser
- Institute of Microbiology, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Switzerland
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Yutin N, Wolf YI, Koonin EV. Origin of giant viruses from smaller DNA viruses not from a fourth domain of cellular life. Virology 2014; 466-467:38-52. [PMID: 25042053 DOI: 10.1016/j.virol.2014.06.032] [Citation(s) in RCA: 116] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 06/14/2014] [Accepted: 06/21/2014] [Indexed: 11/27/2022]
Abstract
The numerous and diverse eukaryotic viruses with large double-stranded DNA genomes that at least partially reproduce in the cytoplasm of infected cells apparently evolved from a single virus ancestor. This major group of viruses is known as Nucleocytoplasmic Large DNA Viruses (NCLDV) or the proposed order Megavirales. Among the "Megavirales", there are three groups of giant viruses with genomes exceeding 500kb, namely Mimiviruses, Pithoviruses, and Pandoraviruses that hold the current record of viral genome size, about 2.5Mb. Phylogenetic analysis of conserved, ancestral NLCDV genes clearly shows that these three groups of giant viruses have three distinct origins within the "Megavirales". The Mimiviruses constitute a distinct family that is distantly related to Phycodnaviridae, Pandoraviruses originate from a common ancestor with Coccolithoviruses within the Phycodnaviridae family, and Pithoviruses are related to Iridoviridae and Marseilleviridae. Maximum likelihood reconstruction of gene gain and loss events during the evolution of the "Megavirales" indicates that each group of giant viruses evolved from viruses with substantially smaller and simpler gene repertoires. Initial phylogenetic analysis of universal genes, such as translation system components, encoded by some giant viruses, in particular Mimiviruses, has led to the hypothesis that giant viruses descend from a fourth, probably extinct domain of cellular life. The results of our comprehensive phylogenomic analysis of giant viruses refute the fourth domain hypothesis and instead indicate that the universal genes have been independently acquired by different giant viruses from their eukaryotic hosts.
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Affiliation(s)
- Natalya Yutin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
| | - Yuri I Wolf
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
| | - Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA.
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