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Lievens EJP, Kühn S, Horas EL, Le Pennec G, Peter S, Petrosky AD, Künzel S, Feulner PGD, Becks L. High parasite diversity maintained after an alga-virus coevolutionary arms race. J Evol Biol 2024; 37:795-806. [PMID: 38699979 DOI: 10.1093/jeb/voae053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 02/27/2024] [Accepted: 05/02/2024] [Indexed: 05/05/2024]
Abstract
Arms race dynamics are a common outcome of host-parasite coevolution. While they can theoretically be maintained indefinitely, realistic arms races are expected to be finite. Once an arms race has ended, for example due to the evolution of a generalist-resistant host, the system may transition into coevolutionary dynamics that favour long-term diversity. In microbial experiments, host-parasite arms races often transition into a stable coexistence of generalist-resistant hosts, (semi-)susceptible hosts, and parasites. While long-term host diversity is implicit in these cases, parasite diversity is usually overlooked. In this study, we examined parasite diversity after the end of an experimental arms race between a unicellular alga (Chlorella variabilis) and its lytic virus (PBCV-1). First, we isolated virus genotypes from multiple time points from two replicate microcosms. A time-shift experiment confirmed that the virus isolates had escalating host ranges, i.e., that arms races had occurred. We then examined the phenotypic and genetic diversity of virus isolates from the post-arms race phase. Post-arms race virus isolates had diverse host ranges, survival probabilities, and growth rates; they also clustered into distinct genetic groups. Importantly, host range diversity was maintained throughout the post-arms race phase, and the frequency of host range phenotypes fluctuated over time. We hypothesize that this dynamic polymorphism was maintained by a combination of fluctuating selection and demographic stochasticity. Together with previous work in prokaryotic systems, our results link experimental observations of arms races to natural observations of long-term host and parasite diversity.
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Affiliation(s)
- Eva J P Lievens
- Aquatic Ecology and Evolution Group, Department of Biology, University of Konstanz, Konstanz, Germany
| | - Samuel Kühn
- Aquatic Ecology and Evolution Group, Department of Biology, University of Konstanz, Konstanz, Germany
| | - Elena L Horas
- Aquatic Ecology and Evolution Group, Department of Biology, University of Konstanz, Konstanz, Germany
| | - Guénolé Le Pennec
- Department of Fish Ecology and Evolution, EAWAG, Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland
| | - Sarah Peter
- Aquatic Ecology and Evolution Group, Department of Biology, University of Konstanz, Konstanz, Germany
| | - Azade D Petrosky
- Aquatic Ecology and Evolution Group, Department of Biology, University of Konstanz, Konstanz, Germany
| | - Sven Künzel
- Department of Evolutionary Genetics, Max Planck Institute for Evolutionary Biology, Plön, Germany
| | - Philine G D Feulner
- Department of Fish Ecology and Evolution, EAWAG, Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland
- Department of Biology, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
| | - Lutz Becks
- Aquatic Ecology and Evolution Group, Department of Biology, University of Konstanz, Konstanz, Germany
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2
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Lievens EJP, Agarkova IV, Dunigan DD, Van Etten JL, Becks L. Efficient assays to quantify the life history traits of algal viruses. Appl Environ Microbiol 2023; 89:e0165923. [PMID: 38092674 PMCID: PMC10734466 DOI: 10.1128/aem.01659-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 09/27/2023] [Indexed: 12/22/2023] Open
Abstract
IMPORTANCE Viruses play a crucial role in microbial ecosystems by liberating nutrients and regulating the growth of their hosts. These effects are governed by viral life history traits, i.e., by the traits determining viral reproduction and survival. Understanding these traits is essential to predicting viral effects, but measuring them is generally labor intensive. In this study, we present efficient methods to quantify the full life cycle of lytic viruses. We developed these methods for viruses infecting unicellular Chlorella algae but expect them to be applicable to other lytic viruses that can be quantified by flow cytometry. By making viral phenotypes accessible, our methods will support research into the diversity and ecological effects of microbial viruses.
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Affiliation(s)
- Eva J. P. Lievens
- Aquatic Ecology and Evolution Group, Limnological Institute, University of Konstanz, Konstanz, Germany
| | - Irina V. Agarkova
- Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
- Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
| | - David D. Dunigan
- Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
- Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
| | - James L. Van Etten
- Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
- Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
| | - Lutz Becks
- Aquatic Ecology and Evolution Group, Limnological Institute, University of Konstanz, Konstanz, Germany
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3
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de Oliveira EG, Filho CADC, Rodrigues RAL. An overview of viral chitinases: General properties and biotechnological potential. Exp Biol Med (Maywood) 2023; 248:2053-2061. [PMID: 38057942 PMCID: PMC10800131 DOI: 10.1177/15353702231208408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2023] Open
Abstract
Chitin is a biopolymer profusely present in nature and of pivotal importance as a structural component in cells. It is degraded by chitinases, enzymes naturally produced by different organisms. Chitinases are proteins enrolled in many cellular mechanisms, including the remodeling process of the fungal cell wall, the cell growth process, the autolysis of filamentous fungi, and cell separation of yeasts, among others. These enzymes also have properties with different biotechnological applications. They are used to produce polymers, for biological control, biofilm formation, and as antitumor and anti-inflammatory target molecules. Chitinases are classified into different glycoside hydrolase (GH) families and are widespread in microorganisms, including viruses. Among them, the GH18 family is highly predominant in the viral genomes, being present and active enzymes in baculoviruses and nucleocytoplasmic large DNA viruses (NCLDV), especially chloroviruses from the Phycodnaviridae family. These viral enzymes contain one or more GH domains and seem to be involved during the viral replication cycle. Curiously, only a few DNA viruses have these enzymes, and studying their properties could be a key feature for biological and biotechnological novelties. Here, we provide an overview of viral chitinases and their probable function in viral infection, showing evidence of at least two distinct origins for these enzymes. Finally, we discuss how these enzymes can be applied as biotechnological tools and what one can expect for the coming years on these GHs.
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Affiliation(s)
- Ellen Gonçalves de Oliveira
- Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte 31270-901, Brazil
| | - Clécio Alonso da Costa Filho
- Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte 31270-901, Brazil
| | - Rodrigo Araújo Lima Rodrigues
- Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte 31270-901, Brazil
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4
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Sultana Q, Banerjee S, Agrawal V, Mukherjee D, Sah R, Jaiswal V. Virovore: A Breakthrough in Virology. Microbiol Insights 2023; 16:11786361231190333. [PMID: 37621408 PMCID: PMC10446875 DOI: 10.1177/11786361231190333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Accepted: 07/10/2023] [Indexed: 08/26/2023] Open
Affiliation(s)
- Qamar Sultana
- Deccan College of Medical Sciences, Hyderabad, Telangana, India
| | | | - Vibhor Agrawal
- King George’s Medical University, Lucknow, Uttar Pradesh, India
| | | | - Ranjit Sah
- Department of Microbiology, Tribhuvan University Teaching Hospital, Institute of Medicine, Kathmandu, Nepal
- Department of Microbiology, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pune, India
- Department of Public Health Dentistry, Dr. D.Y. Patil Dental College and Hospital, Dr. D.Y. Patil Vidyapeeth, Pune, India
| | - Vikash Jaiswal
- Department of Cardiovascular Research, Larkin Community Hospital, South Miami, FL, USA
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5
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DeLong JP, Van Etten JL, Dunigan DD. Lessons from Chloroviruses: the Complex and Diverse Roles of Viruses in Food Webs. J Virol 2023; 97:e0027523. [PMID: 37133447 PMCID: PMC10231191 DOI: 10.1128/jvi.00275-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023] Open
Abstract
Viruses can have large effects on the ecological communities in which they occur. Much of this impact comes from the mortality of host cells, which simultaneously alters microbial community composition and causes the release of matter that can be used by other organisms. However, recent studies indicate that viruses may be even more deeply integrated into the functioning of ecological communities than their effect on nutrient cycling suggests. In particular, chloroviruses, which infect chlorella-like green algae that typically occur as endosymbionts, participate in three types of interactions with other species. Chlororviruses (i) can lure ciliates from a distance, using them as a vector; (ii) depend on predators for access to their hosts; and (iii) get consumed as a food source by, at least, a variety of protists. Therefore, chloroviruses both depend on and influence the spatial structures of communities as well as the flows of energy through those communities, driven by predator-prey interactions. The emergence of these interactions are an eco-evolutionary puzzle, given the interdependence of these species and the many costs and benefits that these interactions generate.
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Affiliation(s)
- John P. DeLong
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
| | - James L. Van Etten
- Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
- Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln Nebraska, USA
| | - David D. Dunigan
- Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
- Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln Nebraska, USA
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6
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Lobb B, Shapter A, Doxey AC, Nissimov JI. Functional Profiling and Evolutionary Analysis of a Marine Microalgal Virus Pangenome. Viruses 2023; 15:v15051116. [PMID: 37243202 DOI: 10.3390/v15051116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 05/04/2023] [Indexed: 05/28/2023] Open
Abstract
Phycodnaviridae are large double-stranded DNA viruses, which facilitate studies of host-virus interactions and co-evolution due to their prominence in algal infection and their role in the life cycle of algal blooms. However, the genomic interpretation of these viruses is hampered by a lack of functional information, stemming from the surprising number of hypothetical genes of unknown function. It is also unclear how many of these genes are widely shared within the clade. Using one of the most extensively characterized genera, Coccolithovirus, as a case study, we combined pangenome analysis, multiple functional annotation tools, AlphaFold structural modeling, and literature analysis to compare the core and accessory pangenome and assess support for novel functional predictions. We determined that the Coccolithovirus pangenome shares 30% of its genes with all 14 strains, making up the core. Notably, 34% of its genes were found in at most three strains. Core genes were enriched in early expression based on a transcriptomic dataset of Coccolithovirus EhV-201 algal infection, were more likely to be similar to host proteins than the non-core set, and were more likely to be involved in vital functions such as replication, recombination, and repair. In addition, we generated and collated annotations for the EhV representative EhV-86 from 12 different annotation sources, building up information for 142 previously hypothetical and putative membrane proteins. AlphaFold was further able to predict structures for 204 EhV-86 proteins with a modelling accuracy of good-high. These functional clues, combined with generated AlphaFold structures, provide a foundational framework for the future characterization of this model genus (and other giant viruses) and a further look into the evolution of the Coccolithovirus proteome.
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Affiliation(s)
- Briallen Lobb
- Department of Biology, University of Waterloo, 200 University Ave. West., Waterloo, ON N2L 3G1, Canada
| | - Anson Shapter
- Department of Biology, University of Waterloo, 200 University Ave. West., Waterloo, ON N2L 3G1, Canada
| | - Andrew C Doxey
- Department of Biology, University of Waterloo, 200 University Ave. West., Waterloo, ON N2L 3G1, Canada
| | - Jozef I Nissimov
- Department of Biology, University of Waterloo, 200 University Ave. West., Waterloo, ON N2L 3G1, Canada
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7
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Widespread Distribution and Evolution of Poxviral Entry-Fusion Complex Proteins in Giant Viruses. Microbiol Spectr 2023:e0494422. [PMID: 36912656 PMCID: PMC10100723 DOI: 10.1128/spectrum.04944-22] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/14/2023] Open
Abstract
Poxviruses are known to encode a set of proteins that form an entry-fusion complex (EFC) to mediate virus entry. However, the diversity, evolution, and origin of these EFC proteins remain poorly understood. Here, we identify the EFC protein homologs in poxviruses and other giant viruses of the phylum Nucleocytoviricota. The 11 EFC genes are present in almost all poxviruses, with the two smallest, G3 and O3, being absent in Entomopoxvirinae and basal lineages of Chordopoxvirinae. Five of the EFC genes are further grouped into two families, A16/G9/J5 and F9/L1, which are widely distributed across other major lineages of Nucleocytoviricota, including metagenome-assembled genomes, but are generally absent in viruses infecting algae or nonamoebozoan heterotrophic protists. The A16/G9/J5 and F9/L1 families cooccur, mostly as single copies, in 93% of the non-Poxviridae giant viruses that have at least one of them. Distribution and phylogenetic patterns suggest that both families originated in the ancestor of Nucleocytoviricota. In addition to the Poxviridae genes, homologs from each of the other Nucleocytoviricota families are largely clustered together, suggesting their ancient presence and vertical inheritance. Despite deep sequence divergences, we observed noticeable conservation of cysteine residues and predicted structures between EFC proteins of Poxviridae and other families. Overall, our study reveals widespread distribution of these EFC protein homologs beyond poxviruses, implies the existence of a conserved membrane fusion mechanism, and sheds light on host range and ancient evolution of Nucleocytoviricota. IMPORTANCE Fusion between virus and host membranes is critical for viruses to release genetic materials and to initiate infection. Whereas most viruses use a single protein for membrane fusion, poxviruses employ a multiprotein entry-fusion complex (EFC). We report that two major families of the EFC proteins are widely distributed within the virus phylum Nucleocytoviricota, which includes poxviruses and other double-stranded (dsDNA) giant viruses that infect animals, amoebozoans, algae, and various microbial eukaryotes. Each of these two protein families is structurally conserved, traces its origin to the root of Nucleocytoviricota, was passed down to the major subclades of Nucleocytoviricota, and is retained in most giant viruses known to infect animals and amoebozoans. The EFC proteins therefore represent a potential mechanism for virus entry in diverse giant viruses. We hypothesize that they may have facilitated the infection of an animal/amoebozoan-like host by the last Nucleocytoviricota common ancestor.
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8
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The Role of Chloroviruses as Possible Infectious Agents for Human Health: Putative Mechanisms of ATCV-1 Infection and Potential Routes of Transmission. Trop Med Infect Dis 2023; 8:tropicalmed8010040. [PMID: 36668947 PMCID: PMC9863483 DOI: 10.3390/tropicalmed8010040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 12/27/2022] [Accepted: 12/28/2022] [Indexed: 01/06/2023] Open
Abstract
The Chlorovirus genus of the Phycodnaviridae family includes large viruses with a double-stranded DNA genome. Chloroviruses are widely distributed in freshwater bodies around the world and have been isolated from freshwater sources in Europe, Asia, Australia, and North and South America. One representative of chloroviruses is Acanthocystis turfacea chlorella virus 1 (ATCV-1), which is hosted by Chlorella heliozoae. A few publications in the last ten years about the potential effects of ATCV-1 on the human brain sparked interest among specialists in the field of human infectious pathology. The goal of our viewpoint was to compile the scant research on the effects of ATCV-1 on the human body, to demonstrate the role of chloroviruses as new possible infectious agents for human health, and to indicate potential routes of virus transmission. We believe that ATCV-1 transmission routes remain unexplored. We also question whether chlorella-based nutritional supplements are dangerous for ATCV-1 infections. Further research will help to identify the routes of infection, the cell types in which ATCV-1 can persist, and the pathological mechanisms of the virus's effect on the human body.
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9
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Giant Viruses as a Source of Novel Enzymes for Biotechnological Application. Pathogens 2022; 11:pathogens11121453. [PMID: 36558786 PMCID: PMC9787589 DOI: 10.3390/pathogens11121453] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 11/24/2022] [Accepted: 11/28/2022] [Indexed: 12/05/2022] Open
Abstract
The global demand for industrial enzymes has been increasing in recent years, and the search for new sources of these biological products is intense, especially in microorganisms. Most known viruses have limited genetic machinery and, thus, have been overlooked by the enzyme industry for years. However, a peculiar group of viruses breaks this paradigm. Giant viruses of the phylum Nucleocytoviricota infect protists (i.e., algae and amoebae) and have complex genomes, reaching up to 2.7 Mb in length and encoding hundreds of genes. Different giant viruses have robust metabolic machinery, especially those in the Phycodnaviridae and Mimiviridae families. In this review, we present some peculiarities of giant viruses that infect protists and discuss why they should be seen as an outstanding source of new enzymes. We revisited the genomes of representatives of different groups of giant viruses and put together information about their enzymatic machinery, highlighting several genes to be explored in biotechnology involved in carbohydrate metabolism, DNA replication, and RNA processing, among others. Finally, we present additional evidence based on structural biology using chitinase as a model to reinforce the role of giant viruses as a source of novel enzymes for biotechnological application.
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10
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Shao Q, Agarkova IV, Noel EA, Dunigan DD, Liu Y, Wang A, Guo M, Xie L, Zhao X, Rossmann MG, Van Etten JL, Klose T, Fang Q. Near-atomic, non-icosahedrally averaged structure of giant virus Paramecium bursaria chlorella virus 1. Nat Commun 2022; 13:6476. [PMID: 36309542 PMCID: PMC9617893 DOI: 10.1038/s41467-022-34218-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 10/18/2022] [Indexed: 12/25/2022] Open
Abstract
Giant viruses are a large group of viruses that infect many eukaryotes. Although components that do not obey the overall icosahedral symmetry of their capsids have been observed and found to play critical roles in the viral life cycles, identities and high-resolution structures of these components remain unknown. Here, by determining a near-atomic-resolution, five-fold averaged structure of Paramecium bursaria chlorella virus 1, we unexpectedly found the viral capsid possesses up to five major capsid protein variants and a penton protein variant. These variants create varied capsid microenvironments for the associations of fibers, a vesicle, and previously unresolved minor capsid proteins. Our structure reveals the identities and atomic models of the capsid components that do not obey the overall icosahedral symmetry and leads to a model for how these components are assembled and initiate capsid assembly, and this model might be applicable to many other giant viruses.
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Affiliation(s)
- Qianqian Shao
- Scholl of Public Health (Shenzhen), Sun Yat-sen University, Shenzhen, Guangdong, 518107, China
| | - Irina V Agarkova
- Department of Plant Pathology and Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE, 68583-0900, USA
| | - Eric A Noel
- Department of Plant Pathology and Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE, 68583-0900, USA
| | - David D Dunigan
- Department of Plant Pathology and Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE, 68583-0900, USA
| | - Yunshu Liu
- Scholl of Public Health (Shenzhen), Sun Yat-sen University, Shenzhen, Guangdong, 518107, China
| | - Aohan Wang
- Scholl of Public Health (Shenzhen), Sun Yat-sen University, Shenzhen, Guangdong, 518107, China
| | - Mingcheng Guo
- Scholl of Public Health (Shenzhen), Sun Yat-sen University, Shenzhen, Guangdong, 518107, China
| | - Linlin Xie
- Scholl of Public Health (Shenzhen), Sun Yat-sen University, Shenzhen, Guangdong, 518107, China
| | - Xinyue Zhao
- Scholl of Public Health (Shenzhen), Sun Yat-sen University, Shenzhen, Guangdong, 518107, China
| | - Michael G Rossmann
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907, USA
| | - James L Van Etten
- Department of Plant Pathology and Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE, 68583-0900, USA.
| | - Thomas Klose
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907, USA.
| | - Qianglin Fang
- Scholl of Public Health (Shenzhen), Sun Yat-sen University, Shenzhen, Guangdong, 518107, China.
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907, USA.
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11
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Rosario K, Van Bogaert N, López-Figueroa NB, Paliogiannis H, Kerr M, Breitbart M. Freshwater macrophytes harbor viruses representing all five major phyla of the RNA viral kingdom Orthornavirae. PeerJ 2022; 10:e13875. [PMID: 35990902 PMCID: PMC9390326 DOI: 10.7717/peerj.13875] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 07/19/2022] [Indexed: 01/18/2023] Open
Abstract
Research on aquatic plant viruses is lagging behind that of their terrestrial counterparts. To address this knowledge gap, here we identified viruses associated with freshwater macrophytes, a taxonomically diverse group of aquatic phototrophs that are visible with the naked eye. We surveyed pooled macrophyte samples collected at four spring sites in Florida, USA through next generation sequencing of RNA extracted from purified viral particles. Sequencing efforts resulted in the detection of 156 freshwater macrophyte associated (FMA) viral contigs, 37 of which approximate complete genomes or segments. FMA viral contigs represent putative members from all five major phyla of the RNA viral kingdom Orthornavirae. Similar to viral types found in land plants, viral sequences identified in macrophytes were dominated by positive-sense RNA viruses. Over half of the FMA viral contigs were most similar to viruses reported from diverse hosts in aquatic environments, including phototrophs, invertebrates, and fungi. The detection of FMA viruses from orders dominated by plant viruses, namely Patatavirales and Tymovirales, indicate that members of these orders may thrive in aquatic hosts. PCR assays confirmed the presence of putative FMA plant viruses in asymptomatic vascular plants, indicating that viruses with persistent lifestyles are widespread in macrophytes. The detection of potato virus Y and oat blue dwarf virus in submerged macrophytes suggests that terrestrial plant viruses infect underwater plants and highlights a potential terrestrial-freshwater plant virus continuum. Defining the virome of unexplored macrophytes will improve our understanding of virus evolution in terrestrial and aquatic primary producers and reveal the potential ecological impacts of viral infection in macrophytes.
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Affiliation(s)
- Karyna Rosario
- College of Marine Science, University of South Florida, St Petersburg, Florida, United States
| | - Noémi Van Bogaert
- College of Marine Science, University of South Florida, St Petersburg, Florida, United States,Present Address: FVPHouse, Berlare, Belgium
| | | | - Haris Paliogiannis
- College of Marine Science, University of South Florida, St Petersburg, Florida, United States,Present Address: MIO-ECSDE, Athens, Greece
| | - Mason Kerr
- College of Marine Science, University of South Florida, St Petersburg, Florida, United States
| | - Mya Breitbart
- College of Marine Science, University of South Florida, St Petersburg, Florida, United States
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12
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Schulz F, Abergel C, Woyke T. Giant virus biology and diversity in the era of genome-resolved metagenomics. Nat Rev Microbiol 2022; 20:721-736. [PMID: 35902763 DOI: 10.1038/s41579-022-00754-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/25/2022] [Indexed: 11/09/2022]
Abstract
The discovery of giant viruses, with capsids as large as some bacteria, megabase-range genomes and a variety of traits typically found only in cellular organisms, was one of the most remarkable breakthroughs in biology. Until recently, most of our knowledge of giant viruses came from ~100 species-level isolates for which genome sequences were available. However, these isolates were primarily derived from laboratory-based co-cultivation with few cultured protists and algae and, thus, did not reflect the true diversity of giant viruses. Although virus co-cultures enabled valuable insights into giant virus biology, many questions regarding their origin, evolution and ecological importance remain unanswered. With advances in sequencing technologies and bioinformatics, our understanding of giant viruses has drastically expanded. In this Review, we summarize our understanding of giant virus diversity and biology based on viral isolates as laboratory cultivation has enabled extensive insights into viral morphology and infection strategies. We then explore how cultivation-independent approaches have heightened our understanding of the coding potential and diversity of the Nucleocytoviricota. We discuss how metagenomics has revolutionized our perspective of giant viruses by revealing their distribution across our planet's biomes, where they impact the biology and ecology of a wide range of eukaryotic hosts and ultimately affect global nutrient cycles.
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Affiliation(s)
- Frederik Schulz
- DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
| | - Chantal Abergel
- Aix Marseille University, CNRS, IGS UMR7256, IMM FR3479, IM2B, IO, Marseille, France
| | - Tanja Woyke
- DOE Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA. .,University of California Merced, Merced, CA, USA.
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13
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Speciale I, Notaro A, Abergel C, Lanzetta R, Lowary TL, Molinaro A, Tonetti M, Van Etten JL, De Castro C. The Astounding World of Glycans from Giant Viruses. Chem Rev 2022; 122:15717-15766. [PMID: 35820164 PMCID: PMC9614988 DOI: 10.1021/acs.chemrev.2c00118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
![]()
Viruses are a heterogeneous ensemble of entities, all
sharing the
need for a suitable host to replicate. They are extremely diverse,
varying in morphology, size, nature, and complexity of their genomic
content. Typically, viruses use host-encoded glycosyltransferases
and glycosidases to add and remove sugar residues from their glycoproteins.
Thus, the structure of the glycans on the viral proteins have, to
date, typically been considered to mimick those of the host. However,
the more recently discovered large and giant viruses differ from this
paradigm. At least some of these viruses code for an (almost) autonomous
glycosylation pathway. These viral genes include those that encode
the production of activated sugars, glycosyltransferases, and other
enzymes able to manipulate sugars at various levels. This review focuses
on large and giant viruses that produce carbohydrate-processing enzymes.
A brief description of those harboring these features at the genomic
level will be discussed, followed by the achievements reached with
regard to the elucidation of the glycan structures, the activity of
the proteins able to manipulate sugars, and the organic synthesis
of some of these virus-encoded glycans. During this progression, we
will also comment on many of the challenging questions on this subject
that remain to be addressed.
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Affiliation(s)
- Immacolata Speciale
- Department of Agricultural Sciences, University of Napoli, Via Università 100, 80055 Portici, Italy
| | - Anna Notaro
- Department of Agricultural Sciences, University of Napoli, Via Università 100, 80055 Portici, Italy.,Centre National de la Recherche Scientifique, Information Génomique & Structurale, Aix-Marseille University, Unité Mixte de Recherche 7256, IMM, IM2B, 13288 Marseille, Cedex 9, France
| | - Chantal Abergel
- Centre National de la Recherche Scientifique, Information Génomique & Structurale, Aix-Marseille University, Unité Mixte de Recherche 7256, IMM, IM2B, 13288 Marseille, Cedex 9, France
| | - Rosa Lanzetta
- Department of Chemical Sciences, University of Napoli, Via Cintia 4, 80126 Napoli, Italy
| | - Todd L Lowary
- Institute of Biological Chemistry, Academia Sinica, Academia Road, Section 2, Nangang 11529, Taipei, Taiwan
| | - Antonio Molinaro
- Department of Chemical Sciences, University of Napoli, Via Cintia 4, 80126 Napoli, Italy
| | - Michela Tonetti
- Department of Experimental Medicine and Center of Excellence for Biomedical Research, University of Genova, 16132 Genova, Italy
| | - James L Van Etten
- Nebraska Center for Virology, University of Nebraska, Lincoln, Nebraska 68583-0900, United States.,Department of Plant Pathology, University of Nebraska, Lincoln, Nebraska 68583-0722, United States
| | - Cristina De Castro
- Department of Agricultural Sciences, University of Napoli, Via Università 100, 80055 Portici, Italy
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14
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Queiroz VF, Rodrigues RAL, Boratto PVDM, La Scola B, Andreani J, Abrahão JS. Amoebae: Hiding in Plain Sight: Unappreciated Hosts for the Very Large Viruses. Annu Rev Virol 2022; 9:79-98. [DOI: 10.1146/annurev-virology-100520-125832] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
For decades, viruses have been isolated primarily from humans and other organisms. Interestingly, one of the most complex sides of the virosphere was discovered using free-living amoebae as hosts. The discovery of giant viruses in the early twenty-first century opened a new chapter in the field of virology. Giant viruses are included in the phylum Nucleocytoviricota and harbor large and complex DNA genomes (up to 2.7 Mb) encoding genes never before seen in the virosphere and presenting gigantic particles (up to 1.5 μm). Different amoebae have been used to isolate and characterize a plethora of new viruses with exciting details about novel viral biology. Through distinct isolation techniques and metagenomics, the diversity and complexity of giant viruses have astonished the scientific community. Here, we discuss the latest findings on amoeba viruses and how using these single-celled organisms as hosts has revealed entities that have remained hidden in plain sight for ages. Expected final online publication date for the Annual Review of Virology, Volume 9 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Victória Fulgêncio Queiroz
- Laboratório de Vírus, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Rodrigo Araújo Lima Rodrigues
- Laboratório de Vírus, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | | | - Bernard La Scola
- Department of Microbes, Evolution, Phylogeny and Infection, Institut de Recherche pour le Développement, Assistance Publique-Hôpitaux de Marseille, Aix-Marseille Université, Marseille, France
- Institut Hospitalo-Universitaire Méditerranée Infection, Marseille, France
| | - Julien Andreani
- Department of Microbes, Evolution, Phylogeny and Infection, Institut de Recherche pour le Développement, Assistance Publique-Hôpitaux de Marseille, Aix-Marseille Université, Marseille, France
- Institut Hospitalo-Universitaire Méditerranée Infection, Marseille, France
- Laboratoire de Virologie, Centre Hospitalier Universitaire Grenoble-Alpes, Grenoble, France
| | - Jônatas Santos Abrahão
- Laboratório de Vírus, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
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15
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Isolation and Identification of a Large Green Alga Virus ( Chlorella Virus XW01) of Mimiviridae and Its Virophage ( Chlorella Virus Virophage SW01) by Using Unicellular Green Algal Cultures. J Virol 2022; 96:e0211421. [PMID: 35262372 DOI: 10.1128/jvi.02114-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Virophages are a group of small double-stranded DNA viruses that infect protist hosts and parasitize the viral factory of host giant/large viruses to propagate. Here, we discover a novel cell-virus-virophage (CVv) tripartite interaction system by using unicellular micro-green algae (Chlorella sp.) as eukaryotic hosts for the first time. Viral particles, resembling known virophages and large alga viruses, are detected in culture supernatants and inside algal cells. Complete genomic sequences of the virophage (Chlorella virus virophage SW01 [CVv-SW01]; 24,744 bp) and large virus (Chlorella virus XW01 [CV-XW01]; 407,612 bp) are obtained from the cocultures. Both genomic and phylogenetic analyses show that CVv-SW01 is closely related to virophages previously found in Dishui Lake. CV-XW01 shares the greatest number of homologous genes (n = 82) with Cafeteria roenbergensis virus (CroV) and phylogenetically represents the closest relative to CroV. This is the first report of a large green alga virus being affiliated with a heterotrophic zooplankton-infecting Cafeteriavirus of the family Mimiviridae. Moreover, the codon usage preferences of CV-XW01 and CVv-SW01 are highly similar to those of CroV and its virophage Mavirus, respectively. The discovery of such a novel CVv system with the green alga Chlorella sp. as the single cellular eukaryotic host paves a way to further investigate the potential interaction mechanism of CVv and its significance in the ecology of green algae and the evolution of large/giant viruses and their parasitic viruses. IMPORTANCE Parasitic virophages are small unicellular eukaryotic dsDNA viruses that rely on the viral factories of coinfecting giant/large dsDNA viruses for propagation. Presently, the identified eukaryotic hosts of isolated virophages were restricted to a free-living amoeba, Acanthamoeba polyphaga, and a widespread marine heterotrophic flagellate, Cafeteria roenbergensis. In this study, we successfully discovered and identified a novel tripartite interaction system comprised of a micro-green alga (Chlorella sp.), Mimiviridae large green alga virus, and virophage at the coculture level, with Chlorella sp. as the eukaryotic host, based on combination analysis of infection, morphotype, genome, and phylogeny. The large green alga virus CV-XW01 represents the closest relative to the Mimiviridae giant virus Cafeteria roenbergensis virus, host virus of the virophage Mavirus, as well as a novel large virus of Mimiviridae that infects a non-protozoan protist host. The virophage CVv-SW01 highly resembles Mavirus in its codon usage frequency and preference, although they are phylogenetically distantly related. These findings give novel insights into the diversity of large/giant viruses and their virophages.
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16
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New Insights from the High-Resolution Monitoring of Microalgae–Virus Infection Dynamics. Viruses 2022; 14:v14030466. [PMID: 35336873 PMCID: PMC8954724 DOI: 10.3390/v14030466] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 02/21/2022] [Accepted: 02/22/2022] [Indexed: 12/10/2022] Open
Abstract
Investigation of virus-induced microalgal host lysis and the associated infection dynamics typically requires sampling of infected cultures at multiple timepoints, visually monitoring the state of infected cells, or determining virus titration within the culture media. Such approaches require intensive effort and are prone to low sensitivity and high error rates. Furthermore, natural physiological variations can become magnified by poor environmental control, which is often compounded by variability in virus stock efficacy and relatively long infection cycles. We introduce a new method that closely monitors host health and integrity to learn about the infection strategy of Chloroviruses. Our approach combines aspects of spectrometry, plaque assays, and infection dose assessment to monitor algal cells under conditions more representative of the natural environment. Our automated method exploits the continuous monitoring of infected microalgae cultures in highly controlled lab-scale photobioreactors that provide the opportunity for environmental control, technical replication, and intensive culture monitoring without external intervention or culture disruption. This approach has enabled the development of a protocol to investigate molecular signalling impacting the virus life cycle and particle release, accurate determination of virus lysis time under multiple environmental conditions, and assessment of the functional diversity of multiple virus isolates.
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17
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Petro TM, Agarkova IV, Esmael A, Dunigan DD, Van Etten JL, Pattee GL. Chlorovirus ATCV-1 Accelerates Motor Deterioration in SOD1-G93A Transgenic Mice and Its SOD1 Augments Induction of Inflammatory Factors From Murine Macrophages. Front Neurol 2022; 13:821166. [PMID: 35280283 PMCID: PMC8908019 DOI: 10.3389/fneur.2022.821166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 01/31/2022] [Indexed: 11/25/2022] Open
Abstract
Background Genetically polymorphic Superoxide Dismutase 1 G93A (SOD1-G93A) underlies one form of familial Amyotrophic Lateral Sclerosis (ALS). Exposures from viruses may also contribute to ALS, possibly by stimulating immune factors, such as IL-6, Interferon Stimulated Genes, and Nitric Oxide. Recently, chlorovirus ATCV-1, which encodes a SOD1, was shown to replicate in macrophages and induce inflammatory factors. Objective This study aimed to determine if ATCV-1 influences development of motor degeneration in an ALS mouse model and to assess whether SOD1 of ATCV-1 influences production of inflammatory factors from macrophages. Methods Sera from sporadic ALS patients were screened for antibody to ATCV-1. Active or inactivated ATCV-1, saline, or a viral mimetic, polyinosinic:polycytidylic acid (poly I:C) were injected intracranially into transgenic mice expressing human SOD1-G93A- or C57Bl/6 mice. RAW264.7 mouse macrophage cells were transfected with a plasmid vector expressing ATCV-1 SOD1 or an empty vector prior to stimulation with poly I:C with or without Interferon-gamma (IFN-γ). Results Serum from sporadic ALS patients had significantly more IgG1 antibody directed against ATCV-1 than healthy controls. Infection of SOD1-G93A mice with active ATCV-1 significantly accelerated onset of motor loss, as measured by tail paralysis, hind limb tucking, righting reflex, and latency to fall in a hanging cage-lid test, but did not significantly affect mortality when compared to saline-treated transgenics. By contrast, poly I:C treatment significantly lengthened survival time but only minimally slowed onset of motor loss, while heat-inactivated ATCV-1 did not affect motor loss or survival. ATCV-1 SOD1 significantly increased expression of IL-6, IL-10, ISG promoter activity, and production of Nitric Oxide from RAW264.7 cells. Conclusion ATCV-1 chlorovirus encoding an endogenous SOD1 accelerates pathogenesis but not mortality, while poly I:C that stimulates antiviral immune responses delays mortality in an ALS mouse model. ATCV-1 SOD1 enhances induction of inflammatory factors from macrophages.
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Affiliation(s)
- Thomas M. Petro
- Department of Oral Biology, University of Nebraska Medical Center, Lincoln, NE, United States
- Nebraska Center for Virology, University of Nebraska Lincoln, Lincoln, NE, United States
- *Correspondence: Thomas M. Petro
| | - Irina V. Agarkova
- Nebraska Center for Virology, University of Nebraska Lincoln, Lincoln, NE, United States
- Department Plant Pathology, University of Nebraska Lincoln, Lincoln, NE, United States
| | - Ahmed Esmael
- Nebraska Center for Virology, University of Nebraska Lincoln, Lincoln, NE, United States
- Botany and Microbiology Department, Faculty of Science, Benha University, Benha, Egypt
| | - David D. Dunigan
- Nebraska Center for Virology, University of Nebraska Lincoln, Lincoln, NE, United States
- Department Plant Pathology, University of Nebraska Lincoln, Lincoln, NE, United States
| | - James L. Van Etten
- Nebraska Center for Virology, University of Nebraska Lincoln, Lincoln, NE, United States
- Department Plant Pathology, University of Nebraska Lincoln, Lincoln, NE, United States
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18
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Nwokolo NL, Enebe MC. Shotgun metagenomics evaluation of soil fertilization effect on the rhizosphere viral community of maize plants. Antonie van Leeuwenhoek 2021; 115:69-78. [PMID: 34762236 DOI: 10.1007/s10482-021-01679-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 10/19/2021] [Indexed: 11/30/2022]
Abstract
The need for sustainability in food supply has led to progressive increase in soil nutrient enrichment. Fertilizer application effects both biological and abiotic processes in the soil, of which the bacterial community that support viral multiplication are equally influenced. Nevertheless, little is known on the effect of soil fertilization on the Soil viral community composition and dynamics. In this study, we evaluated the influence of soil fertilization on the maize rhizosphere viral community growing in Luvisolic soil. The highest abundance of bacteriophages were detected in soil treated with 8 tons/ha compost manure (Cp8), 60 kg/ha inorganic fertilizer (N1), 4 tons/ha compost manure (Cp4) and the unfertilized control (Cn0). Our result showed higher relative abundance of Myoviridae, Podoviridae and Siphoviridae in 8 tons/ha organic manure (Cp8) fertilized compared to others. While Inoviridae and Microviridae were the most relative abundant phage families in 4 tons/ha organic manure (Cp4) fertilized soil. This demonstrate that soil fertilization with organic manure increases the abundance and diversity of viruses in the soil due to its soil conditioning effects.
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Affiliation(s)
| | - Matthew Chekwube Enebe
- Food Security and Safety Niche Area, Faculty of Natural and Agricultural Sciences, North-West University, Private Bag X2046, Mmabatho, 2735, South Africa.
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19
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Speciale I, Di Lorenzo F, Notaro A, Noel E, Agarkova I, Molinaro A, Van Etten JL, De Castro C. N-glycans from Paramecium bursaria chlorella virus MA-1D: Re-evaluation of the oligosaccharide common core structure. Glycobiology 2021; 32:260-273. [DOI: 10.1093/glycob/cwab113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 10/29/2021] [Accepted: 10/30/2021] [Indexed: 11/12/2022] Open
Abstract
Abstract
Paramecium bursaria chlorella virus MA-1D is a chlorovirus that infects Chlorella variabilis strain NC64A, a symbiont of the protozoan Paramecium bursaria. MA-1D has a 339-kb genome encoding ca. 366 proteins and 11 tRNAs. Like other chloroviruses, its major capsid protein (MCP) is decorated with N-glycans, whose structures have been solved in this work by using nuclear magnetic (NMR) spectroscopy and MALDI-TOF mass spectrometry along with MS/MS experiments. This analysis identified three N-linked oligosaccharides that differ in the non-stoichiometric presence of three monosaccharides, with the largest oligosaccharide composed of eight residues organized in a highly branched fashion. The N-glycans described here share several features with those of the other chloroviruses except that they lack a distal xylose unit that was believed to be part of a conserved core region for all the chloroviruses. Examination of the MA-1D genome detected a gene with strong homology to the putative xylosyltransferase in the reference chlorovirus PBCV-1 and in virus NY-2A, albeit mutated with a premature stop codon. This discovery means that we need to reconsider the essential features of the common core glycan region in the chloroviruses.
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Affiliation(s)
- Immacolata Speciale
- Department of Agricultural Sciences, University of Napoli Federico II, Via Università 100, 80055, Portici, Italy
| | - Flaviana Di Lorenzo
- Department of Agricultural Sciences, University of Napoli Federico II, Via Università 100, 80055, Portici, Italy
| | - Anna Notaro
- Department of Agricultural Sciences, University of Napoli Federico II, Via Università 100, 80055, Portici, Italy
| | - Eric Noel
- Nebraska Center for Virology, University of Nebraska, Lincoln, NE, 68583-0900, USA
- School of Biological Sciences, University of Nebraska, Lincoln, NE, 68588-0118, USA
- Innovative Genomics Institute, University of California, Berkeley, CA, 94720, USA
| | - Irina Agarkova
- Nebraska Center for Virology, University of Nebraska, Lincoln, NE, 68583-0900, USA
- Department of Plant Pathology, University of Nebraska, Lincoln, NE, 68583-0722, USA
| | - Antonio Molinaro
- Department of Chemical Sciences, University of Napoli Federico II, Via Cintia 26, 80126, Napoli, Italy
| | - James L Van Etten
- Nebraska Center for Virology, University of Nebraska, Lincoln, NE, 68583-0900, USA
- Department of Plant Pathology, University of Nebraska, Lincoln, NE, 68583-0722, USA
| | - Cristina De Castro
- Department of Agricultural Sciences, University of Napoli Federico II, Via Università 100, 80055, Portici, Italy
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20
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Viruses infecting a warm water picoeukaryote shed light on spatial co-occurrence dynamics of marine viruses and their hosts. THE ISME JOURNAL 2021; 15:3129-3147. [PMID: 33972727 PMCID: PMC8528832 DOI: 10.1038/s41396-021-00989-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 03/08/2021] [Accepted: 04/14/2021] [Indexed: 02/03/2023]
Abstract
The marine picoeukaryote Bathycoccus prasinos has been considered a cosmopolitan alga, although recent studies indicate two ecotypes exist, Clade BI (B. prasinos) and Clade BII. Viruses that infect Bathycoccus Clade BI are known (BpVs), but not that infect BII. We isolated three dsDNA prasinoviruses from the Sargasso Sea against Clade BII isolate RCC716. The BII-Vs do not infect BI, and two (BII-V2 and BII-V3) have larger genomes (~210 kb) than BI-Viruses and BII-V1. BII-Vs share ~90% of their proteins, and between 65% to 83% of their proteins with sequenced BpVs. Phylogenomic reconstructions and PolB analyses establish close-relatedness of BII-V2 and BII-V3, yet BII-V2 has 10-fold higher infectivity and induces greater mortality on host isolate RCC716. BII-V1 is more distant, has a shorter latent period, and infects both available BII isolates, RCC716 and RCC715, while BII-V2 and BII-V3 do not exhibit productive infection of the latter in our experiments. Global metagenome analyses show Clade BI and BII algal relative abundances correlate positively with their respective viruses. The distributions delineate BI/BpVs as occupying lower temperature mesotrophic and coastal systems, whereas BII/BII-Vs occupy warmer temperature, higher salinity ecosystems. Accordingly, with molecular diagnostic support, we name Clade BII Bathycoccus calidus sp. nov. and propose that molecular diversity within this new species likely connects to the differentiated host-virus dynamics observed in our time course experiments. Overall, the tightly linked biogeography of Bathycoccus host and virus clades observed herein supports species-level host specificity, with strain-level variations in infection parameters.
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21
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Aylward FO, Moniruzzaman M, Ha AD, Koonin EV. A phylogenomic framework for charting the diversity and evolution of giant viruses. PLoS Biol 2021; 19:e3001430. [PMID: 34705818 PMCID: PMC8575486 DOI: 10.1371/journal.pbio.3001430] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 11/08/2021] [Accepted: 09/29/2021] [Indexed: 11/22/2022] Open
Abstract
Large DNA viruses of the phylum Nucleocytoviricota have recently emerged as important members of ecosystems around the globe that challenge traditional views of viral complexity. Numerous members of this phylum that cannot be classified within established families have recently been reported, and there is presently a strong need for a robust phylogenomic and taxonomic framework for these viruses. Here, we report a comprehensive phylogenomic analysis of the Nucleocytoviricota, present a set of giant virus orthologous groups (GVOGs) together with a benchmarked reference phylogeny, and delineate a hierarchical taxonomy within this phylum. We show that the majority of Nucleocytoviricota diversity can be partitioned into 6 orders, 32 families, and 344 genera, substantially expanding the number of currently recognized taxonomic ranks for these viruses. We integrate our results within a taxonomy that has been adopted for all viruses to establish a unifying framework for the study of Nucleocytoviricota diversity, evolution, and environmental distribution. Giant viruses have transformed our understanding of viral complexity, but we lack a framework for examining their diversity in the biosphere. This study presents a phylogenomic resource for charting the diversity, ecology, and evolution of giant viruses.
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Affiliation(s)
- Frank O. Aylward
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
- Center for Emerging, Zoonotic, and Arthropod-borne Pathogens, Virginia Tech, Blacksburg, Virginia, United States of America
- * E-mail:
| | - Mohammad Moniruzzaman
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Anh D. Ha
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Eugene V. Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland, United States of America
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22
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Noel EA, Weeks DP, Van Etten JL. Pursuit of chlorovirus genetic transformation and CRISPR/Cas9-mediated gene editing. PLoS One 2021; 16:e0252696. [PMID: 34673785 PMCID: PMC8530361 DOI: 10.1371/journal.pone.0252696] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 09/29/2021] [Indexed: 11/18/2022] Open
Abstract
Genetic and molecular modifications of the large dsDNA chloroviruses, with genomes of 290 to 370 kb, would expedite studies to elucidate the functions of both identified and unidentified virus-encoded proteins. These plaque-forming viruses replicate in certain unicellular, eukaryotic chlorella-like green algae. However, to date, only a few of these algal species and virtually none of their viruses have been genetically manipulated due to lack of practical methods for genetic transformation and genome editing. Attempts at using Agrobacterium-mediated transfection of chlorovirus host Chlorella variabilis NC64A with a specially-designed binary vector resulted in successful transgenic cell selection based on expression of a hygromycin-resistance gene, initial expression of a green fluorescence gene and demonstration of integration of Agrobacterium T-DNA. However, expression of the integrated genes was soon lost. To develop gene editing tools for modifying specific chlorovirus CA-4B genes using preassembled Cas9 protein-sgRNA ribonucleoproteins (RNPs), we tested multiple methods for delivery of Cas9/sgRNA RNP complexes into infected cells including cell wall-degrading enzymes, electroporation, silicon carbide (SiC) whiskers, and cell-penetrating peptides (CPPs). In one experiment two independent virus mutants were isolated from macerozyme-treated NC64A cells incubated with Cas9/sgRNA RNPs targeting virus CA-4B-encoded gene 034r, which encodes a glycosyltransferase. Analysis of DNA sequences from the two mutant viruses showed highly targeted nucleotide sequence modifications in the 034r gene of each virus that were fully consistent with Cas9/RNP-directed gene editing. However, in ten subsequent experiments, we were unable to duplicate these results and therefore unable to achieve a reliable system to genetically edit chloroviruses. Nonetheless, these observations provide strong initial suggestions that Cas9/RNPs may function to promote editing of the chlorovirus genome, and that further experimentation is warranted and worthwhile.
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Affiliation(s)
- Eric A. Noel
- Nebraska Center for Virology, University of Nebraska, Lincoln, Nebraska, United States of America
- School of Biological Sciences, University of Nebraska, Lincoln, Nebraska, United States of America
| | - Donald P. Weeks
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska, United States of America
| | - James L. Van Etten
- Nebraska Center for Virology, University of Nebraska, Lincoln, Nebraska, United States of America
- Department of Plant Pathology, University of Nebraska, Lincoln, Nebraska, United States of America
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23
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Functional genomic analyses reveal an open pan-genome for the chloroviruses and a potential for genetic innovation in new isolates. J Virol 2021; 96:e0136721. [PMID: 34669449 DOI: 10.1128/jvi.01367-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chloroviruses (family Phycodnaviridae) are large dsDNA viruses that infect unicellular green algae present in inland waters. These viruses have been isolated using three main chlorella-like green algal host cells, traditionally called NC64A, SAG and Pbi, revealing extensive genetic diversity. In this study, we performed a functional genomic analysis on 36 chloroviruses that infected the three different hosts. Phylogenetic reconstruction based on the DNA polymerase B family gene clustered the chloroviruses into three distinct clades. The viral pan-genome consists of 1,345 clusters of orthologous groups of genes (COGs), with 126 COGs conserved in all viruses. 368, 268 and 265 COGs are found exclusively in viruses that infect NC64A, SAG, and Pbi algal hosts, respectively. Two-thirds of the COGs have no known function, constituting the "dark pan-genome" of chloroviruses, and further studies focusing on these genes may identify important novelties. The proportion of functionally characterized COGs composing the pan- and the core-genome are similar, but those related to transcription and RNA processing, protein metabolism, and virion morphogenesis are at least 4-fold more represented in the core-genome. Bipartite network construction evidencing the COG-sharing among host-specific viruses identified 270 COGs shared by at least one virus from each of the different host groups. Finally, our results reveal an open pan-genome for chloroviruses and a well-established core-genome, indicating that the isolation of new chloroviruses can be a valuable source of genetic discovery. Importance Chloroviruses are large dsDNA viruses that infect unicellular green algae distributed worldwide in freshwater environments. They comprise a genetically diverse group of viruses; however, a comprehensive investigation of the genomic evolution of these viruses is still missing. Here we performed a functional pan-genome analysis comprising 36 chloroviruses associated with three different algal hosts in the family Chlorellaceae, referred to as zoochlorellae because of their endosymbiotic lifestyle. We identified a set of 126 highly conserved genes, most of which are related to essential functions in the viral replicative cycle. Several genes are unique to distinct isolates, resulting in an open pan-genome for chloroviruses. This profile is associated with generalist organisms, and new insights into the evolution and ecology of chloroviruses are presented. Ultimately, our results highlight the potential for genetic diversity in new isolates.
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24
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Catalysis of Chlorovirus Production by the Foraging of Bursaria truncatella on Paramecia bursaria Containing Endosymbiotic Algae. Microorganisms 2021; 9:microorganisms9102170. [PMID: 34683491 PMCID: PMC8540807 DOI: 10.3390/microorganisms9102170] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 10/13/2021] [Accepted: 10/15/2021] [Indexed: 11/16/2022] Open
Abstract
Chloroviruses are large viruses that replicate in chlorella-like green algae and normally exist as mutualistic endosymbionts (referred to as zoochlorellae) in protists such as Paramecium bursaria. Chlorovirus populations rise and fall in indigenous waters through time; however, the factors involved in these virus fluctuations are still under investigation. Chloroviruses attach to the surface of P. bursaria but cannot infect their zoochlorellae hosts because the viruses cannot reach the zoochlorellae as long as they are in the symbiotic phase. Predators of P. bursaria, such as copepods and didinia, can bring chloroviruses into contact with zoochlorellae by disrupting the paramecia, which results in an increase in virus titers in microcosm experiments. Here, we report that another predator of P. bursaria, Bursaria truncatella, can also increase chlorovirus titers. After two days of foraging on P. bursaria, B. truncatella increased infectious chlorovirus abundance about 20 times above the controls. Shorter term foraging (3 h) resulted in a small increase of chlorovirus titers over the controls and more foraging generated more chloroviruses. Considering that B. truncatella does not release viable zoochlorellae either during foraging or through fecal pellets, where zoochlorellae could be infected by chlorovirus, we suggest a third pathway of predator virus catalysis. By engulfing the entire protist and digesting it slowly, virus replication can occur within the predator and some of the virus is passed out through a waste vacuole. These results provide additional support for the hypothesis that predators of P. bursaria are important drivers of chlorovirus population sizes and dynamics.
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25
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DeLong JP, Al-Sammak MA, Al-Ameeli ZT, Dunigan DD, Edwards KF, Fuhrmann JJ, Gleghorn JP, Li H, Haramoto K, Harrison AO, Marston MF, Moore RM, Polson SW, Ferrell BD, Salsbery ME, Schvarcz CR, Shirazi J, Steward GF, Van Etten JL, Wommack KE. Towards an integrative view of virus phenotypes. Nat Rev Microbiol 2021; 20:83-94. [PMID: 34522049 DOI: 10.1038/s41579-021-00612-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/26/2021] [Indexed: 12/25/2022]
Abstract
Understanding how phenotypes emerge from genotypes is a foundational goal in biology. As challenging as this task is when considering cellular life, it is further complicated in the case of viruses. During replication, a virus as a discrete entity (the virion) disappears and manifests itself as a metabolic amalgam between the virus and the host (the virocell). Identifying traits that unambiguously constitute a virus's phenotype is straightforward for the virion, less so for the virocell. Here, we present a framework for categorizing virus phenotypes that encompasses both virion and virocell stages and considers functional and performance traits of viruses in the context of fitness. Such an integrated view of virus phenotype is necessary for comprehensive interpretation of viral genome sequences and will advance our understanding of viral evolution and ecology.
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Affiliation(s)
- John P DeLong
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA.
| | - Maitham A Al-Sammak
- Tropical Biological Research Unit, College of Science, University of Baghdad, Baghdad, Iraq.,Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Zeina T Al-Ameeli
- Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE, USA.,Medical Technical Institutes, Middle Technical University, Baghdad, Iraq
| | - David D Dunigan
- Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE, USA.,Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Kyle F Edwards
- Department of Oceanography, University of Hawai'i at Mānoa, Honolulu, HI, USA
| | - Jeffry J Fuhrmann
- Department of Plant and Soil Sciences, University of Delaware, Newark, DE, USA.,Department of Biological Sciences, University of Delaware, Newark, DE, USA
| | - Jason P Gleghorn
- Department of Biological Sciences, University of Delaware, Newark, DE, USA.,Department of Biomedical Engineering, University of Delaware, Newark, DE, USA
| | - Hanqun Li
- Department of Biological Sciences, University of Delaware, Newark, DE, USA.,Delaware Biotechnology Institute, University of Delaware, Newark, DE, USA
| | - Kona Haramoto
- Department of Plant and Soil Sciences, University of Delaware, Newark, DE, USA.,Delaware Biotechnology Institute, University of Delaware, Newark, DE, USA
| | - Amelia O Harrison
- Department of Plant and Soil Sciences, University of Delaware, Newark, DE, USA.,Delaware Biotechnology Institute, University of Delaware, Newark, DE, USA
| | - Marcia F Marston
- Department of Biology and Marine Biology, Roger Williams University, Bristol, RI, USA
| | - Ryan M Moore
- Delaware Biotechnology Institute, University of Delaware, Newark, DE, USA.,Center for Bioinformatics and Computational Biology, University of Delaware, Newark, DE, USA
| | - Shawn W Polson
- Department of Plant and Soil Sciences, University of Delaware, Newark, DE, USA.,Department of Biological Sciences, University of Delaware, Newark, DE, USA.,Delaware Biotechnology Institute, University of Delaware, Newark, DE, USA.,Center for Bioinformatics and Computational Biology, University of Delaware, Newark, DE, USA
| | - Barbra D Ferrell
- Delaware Biotechnology Institute, University of Delaware, Newark, DE, USA.,Center for Bioinformatics and Computational Biology, University of Delaware, Newark, DE, USA
| | - Miranda E Salsbery
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA
| | | | - Jasmine Shirazi
- Department of Biomedical Engineering, University of Delaware, Newark, DE, USA
| | - Grieg F Steward
- Department of Oceanography, University of Hawai'i at Mānoa, Honolulu, HI, USA
| | - James L Van Etten
- Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE, USA.,Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - K Eric Wommack
- Department of Plant and Soil Sciences, University of Delaware, Newark, DE, USA. .,Department of Biological Sciences, University of Delaware, Newark, DE, USA. .,Delaware Biotechnology Institute, University of Delaware, Newark, DE, USA.
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26
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Abstract
Giant DNA viruses of eukaryotes are notable for their extraordinary genome size and coding capacity. Once thought to be oddities in the virus world, these elusive microbes have turned out to be widely occurring in marine, freshwater, and terrestrial ecosystems and are commonly associated with diverse hosts, in particular microbial eukaryotes. This commentary discusses how new sequencing techniques and information can inform us about the interactions between giant viruses and eukaryotic hosts during the viral replication cycle and their implications for ecological and evolutionary processes across different spatiotemporal scales.
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27
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de Souza FG, Abrahão JS, Rodrigues RAL. Comparative Analysis of Transcriptional Regulation Patterns: Understanding the Gene Expression Profile in Nucleocytoviricota. Pathogens 2021; 10:935. [PMID: 34451399 PMCID: PMC8400408 DOI: 10.3390/pathogens10080935] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 07/21/2021] [Accepted: 07/23/2021] [Indexed: 12/13/2022] Open
Abstract
The nucleocytoplasmic large DNA viruses (NCLDV) possess unique characteristics that have drawn the attention of the scientific community, and they are now classified in the phylum Nucleocytoviricota. They are characterized by sharing many genes and have their own transcriptional apparatus, which provides certain independence from their host's machinery. Thus, the presence of a robust transcriptional apparatus has raised much discussion about the evolutionary aspects of these viruses and their genomes. Understanding the transcriptional process in NCLDV would provide information regarding their evolutionary history and a better comprehension of the biology of these viruses and their interaction with hosts. In this work, we reviewed NCLDV transcription and performed a comparative functional analysis of the groups of genes expressed at different times of infection of representatives of six different viral families of giant viruses. With this analysis, it was possible to observe a temporal profile of their gene expression and set of genes activated in specific phases throughout the multiplication cycle as a common characteristic of this group. Due to the lack of information regarding the transcriptional regulation process of this group of pathogens, we sought to provide information that contributes to and opens up the field for transcriptional studies of other viruses belonging to Nucleocytoviricota.
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Affiliation(s)
| | - Jônatas Santos Abrahão
- Laboratório de Vírus, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais 31270-901, Brazil;
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28
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Zhong ZP, Tian F, Roux S, Gazitúa MC, Solonenko NE, Li YF, Davis ME, Van Etten JL, Mosley-Thompson E, Rich VI, Sullivan MB, Thompson LG. Glacier ice archives nearly 15,000-year-old microbes and phages. MICROBIOME 2021; 9:160. [PMID: 34281625 PMCID: PMC8290583 DOI: 10.1186/s40168-021-01106-w] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 05/31/2021] [Indexed: 05/05/2023]
Abstract
BACKGROUND Glacier ice archives information, including microbiology, that helps reveal paleoclimate histories and predict future climate change. Though glacier-ice microbes are studied using culture or amplicon approaches, more challenging metagenomic approaches, which provide access to functional, genome-resolved information and viruses, are under-utilized, partly due to low biomass and potential contamination. RESULTS We expand existing clean sampling procedures using controlled artificial ice-core experiments and adapted previously established low-biomass metagenomic approaches to study glacier-ice viruses. Controlled sampling experiments drastically reduced mock contaminants including bacteria, viruses, and free DNA to background levels. Amplicon sequencing from eight depths of two Tibetan Plateau ice cores revealed common glacier-ice lineages including Janthinobacterium, Polaromonas, Herminiimonas, Flavobacterium, Sphingomonas, and Methylobacterium as the dominant genera, while microbial communities were significantly different between two ice cores, associating with different climate conditions during deposition. Separately, ~355- and ~14,400-year-old ice were subject to viral enrichment and low-input quantitative sequencing, yielding genomic sequences for 33 vOTUs. These were virtually all unique to this study, representing 28 novel genera and not a single species shared with 225 environmentally diverse viromes. Further, 42.4% of the vOTUs were identifiable temperate, which is significantly higher than that in gut, soil, and marine viromes, and indicates that temperate phages are possibly favored in glacier-ice environments before being frozen. In silico host predictions linked 18 vOTUs to co-occurring abundant bacteria (Methylobacterium, Sphingomonas, and Janthinobacterium), indicating that these phages infected ice-abundant bacterial groups before being archived. Functional genome annotation revealed four virus-encoded auxiliary metabolic genes, particularly two motility genes suggest viruses potentially facilitate nutrient acquisition for their hosts. Finally, given their possible importance to methane cycling in ice, we focused on Methylobacterium viruses by contextualizing our ice-observed viruses against 123 viromes and prophages extracted from 131 Methylobacterium genomes, revealing that the archived viruses might originate from soil or plants. CONCLUSIONS Together, these efforts further microbial and viral sampling procedures for glacier ice and provide a first window into viral communities and functions in ancient glacier environments. Such methods and datasets can potentially enable researchers to contextualize new discoveries and begin to incorporate glacier-ice microbes and their viruses relative to past and present climate change in geographically diverse regions globally. Video Abstract.
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Affiliation(s)
- Zhi-Ping Zhong
- Byrd Polar and Climate Research Center, Ohio State University, Columbus, OH, USA
- Department of Microbiology, Ohio State University, Columbus, OH, USA
- Center of Microbiome Science, Ohio State University, Columbus, OH, USA
| | - Funing Tian
- Department of Microbiology, Ohio State University, Columbus, OH, USA
- Center of Microbiome Science, Ohio State University, Columbus, OH, USA
| | - Simon Roux
- Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | | | - Natalie E Solonenko
- Department of Microbiology, Ohio State University, Columbus, OH, USA
- Center of Microbiome Science, Ohio State University, Columbus, OH, USA
| | - Yueh-Fen Li
- Department of Microbiology, Ohio State University, Columbus, OH, USA
- Center of Microbiome Science, Ohio State University, Columbus, OH, USA
| | - Mary E Davis
- Byrd Polar and Climate Research Center, Ohio State University, Columbus, OH, USA
| | - James L Van Etten
- Department of Plant Pathology and Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Ellen Mosley-Thompson
- Byrd Polar and Climate Research Center, Ohio State University, Columbus, OH, USA
- Center of Microbiome Science, Ohio State University, Columbus, OH, USA
- Department of Geography, Ohio State University, Columbus, OH, USA
| | - Virginia I Rich
- Byrd Polar and Climate Research Center, Ohio State University, Columbus, OH, USA
- Department of Microbiology, Ohio State University, Columbus, OH, USA
- Center of Microbiome Science, Ohio State University, Columbus, OH, USA
| | - Matthew B Sullivan
- Byrd Polar and Climate Research Center, Ohio State University, Columbus, OH, USA.
- Department of Microbiology, Ohio State University, Columbus, OH, USA.
- Center of Microbiome Science, Ohio State University, Columbus, OH, USA.
- Department of Civil, Environmental and Geodetic Engineering, Ohio State University, Columbus, OH, USA.
| | - Lonnie G Thompson
- Byrd Polar and Climate Research Center, Ohio State University, Columbus, OH, USA.
- Center of Microbiome Science, Ohio State University, Columbus, OH, USA.
- School of Earth Sciences, Ohio State University, Columbus, OH, USA.
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29
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Muñoz-Gómez SA, Kreutz M, Hess S. A microbial eukaryote with a unique combination of purple bacteria and green algae as endosymbionts. SCIENCE ADVANCES 2021; 7:eabg4102. [PMID: 34117067 PMCID: PMC8195481 DOI: 10.1126/sciadv.abg4102] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 04/27/2021] [Indexed: 05/08/2023]
Abstract
Oxygenic photosynthesizers (cyanobacteria and eukaryotic algae) have repeatedly become endosymbionts throughout evolution. In contrast, anoxygenic photosynthesizers (e.g., purple bacteria) are exceedingly rare as intracellular symbionts. Here, we report on the morphology, ultrastructure, lifestyle, and metagenome of the only "purple-green" eukaryote known. The ciliate Pseudoblepharisma tenue harbors green algae and hundreds of genetically reduced purple bacteria. The latter represent a new candidate species of the Chromatiaceae that lost known genes for sulfur dissimilation. The tripartite consortium is physiologically complex because of the versatile energy metabolism of each partner but appears to be ecologically specialized as it prefers hypoxic sediments. The emergent niche of this complex symbiosis is predicted to be a partial overlap of each partners' niches and may be largely defined by anoxygenic photosynthesis and possibly phagotrophy. This purple-green ciliate thus represents an extraordinary example of how symbiosis merges disparate physiologies and allows emergent consortia to create novel ecological niches.
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Affiliation(s)
- Sergio A Muñoz-Gómez
- Institute for Zoology, Cologne Biocenter, University of Cologne, Zülpicher Str. 47b, 50674 Cologne, Germany.
- Center for Mechanism of Evolution, The Biodesign Institute, School of Life Sciences, Arizona State University, 727 E. Tyler St., Tempe, AZ 85281-5001, USA
| | - Martin Kreutz
- Private Laboratory, Am See 27, 78465 Constance, Germany
| | - Sebastian Hess
- Institute for Zoology, Cologne Biocenter, University of Cologne, Zülpicher Str. 47b, 50674 Cologne, Germany.
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30
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Dos Santos Oliveira J, Lavell AA, Essus VA, Souza G, Nunes GHP, Benício E, Guimarães AJ, Parent KN, Cortines JR. Structure and physiology of giant DNA viruses. Curr Opin Virol 2021; 49:58-67. [PMID: 34051592 DOI: 10.1016/j.coviro.2021.04.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 04/27/2021] [Accepted: 04/29/2021] [Indexed: 02/02/2023]
Abstract
Although giant viruses have existed for millennia and possibly exerted great evolutionary influence in their environment. Their presence has only been noticed by virologists recently with the discovery of Acanthamoeba polyphaga mimivirus in 2003. Its virion with a diameter of 500 nm and its genome larger than 1 Mpb shattered preconceived standards of what a virus is and triggered world-wide prospection studies. Thanks to these investigations many giant virus families were discovered, each with its own morphological peculiarities and genomes ranging from 0.4 to 2.5 Mpb that possibly encode more than 400 viral proteins. This review aims to present the morphological diversity, the different aspects observed in host-virus interactions during replication, as well as the techniques utilized during their investigation.
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Affiliation(s)
- Juliana Dos Santos Oliveira
- Departamento de Virologia, Instituto de Mcirobiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21590-902, Rio de Janeiro, Brazil
| | - Anastasiya A Lavell
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Victor Alejandro Essus
- Departamento de Virologia, Instituto de Mcirobiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21590-902, Rio de Janeiro, Brazil
| | - Getúlio Souza
- Departamento de Virologia, Instituto de Mcirobiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21590-902, Rio de Janeiro, Brazil
| | - Gabriel Henrique Pereira Nunes
- Departamento de Virologia, Instituto de Mcirobiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21590-902, Rio de Janeiro, Brazil
| | - Eduarda Benício
- Departamento de Virologia, Instituto de Mcirobiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21590-902, Rio de Janeiro, Brazil
| | - Allan Jefferson Guimarães
- Departamento de Microbiologia e Parasitologia, Instituto Biomédico, Universidade Federal Fluminense, Niterói, Brazil
| | - Kristin N Parent
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
| | - Juliana R Cortines
- Departamento de Virologia, Instituto de Mcirobiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21590-902, Rio de Janeiro, Brazil.
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31
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Identification of a Chlorovirus PBCV-1 Protein Involved in Degrading the Host Cell Wall during Virus Infection. Viruses 2021; 13:v13050782. [PMID: 33924931 PMCID: PMC8145301 DOI: 10.3390/v13050782] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 04/25/2021] [Accepted: 04/26/2021] [Indexed: 12/22/2022] Open
Abstract
Chloroviruses are unusual among viruses infecting eukaryotic organisms in that they must, like bacteriophages, penetrate a rigid cell wall to initiate infection. Chlorovirus PBCV-1 infects its host, Chlorella variabilis NC64A by specifically binding to and degrading the cell wall of the host at the point of contact by a virus-packaged enzyme(s). However, PBCV-1 does not use any of the five previously characterized virus-encoded polysaccharide degrading enzymes to digest the Chlorella host cell wall during virus entry because none of the enzymes are packaged in the virion. A search for another PBCV-1-encoded and virion-associated protein identified protein A561L. The fourth domain of A561L is a 242 amino acid C-terminal domain, named A561LD4, with cell wall degrading activity. An A561LD4 homolog was present in all 52 genomically sequenced chloroviruses, infecting four different algal hosts. A561LD4 degraded the cell walls of all four chlorovirus hosts, as well as several non-host Chlorella spp. Thus, A561LD4 was not cell-type specific. Finally, we discovered that exposure of highly purified PBCV-1 virions to A561LD4 increased the specific infectivity of PBCV-1 from about 25–30% of the particles forming plaques to almost 50%. We attribute this increase to removal of residual host receptor that attached to newly replicated viruses in the cell lysates.
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32
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Chlorovirus PBCV-1 Multidomain Protein A111/114R Has Three Glycosyltransferase Functions Involved in the Synthesis of Atypical N-Glycans. Viruses 2021; 13:v13010087. [PMID: 33435207 PMCID: PMC7826918 DOI: 10.3390/v13010087] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 01/03/2021] [Accepted: 01/08/2021] [Indexed: 12/04/2022] Open
Abstract
The structures of the four N-linked glycans from the prototype chlorovirus PBCV-1 major capsid protein do not resemble any other glycans in the three domains of life. All known chloroviruses and antigenic variants (or mutants) share a unique conserved central glycan core consisting of five sugars, except for antigenic mutant virus P1L6, which has four of the five sugars. A combination of genetic and structural analyses indicates that the protein coded by PBCV-1 gene a111/114r, conserved in all chloroviruses, is a glycosyltransferase with three putative domains of approximately 300 amino acids each. Here, in addition to in silico sequence analysis and protein modeling, we measured the hydrolytic activity of protein A111/114R. The results suggest that domain 1 is a galactosyltransferase, domain 2 is a xylosyltransferase and domain 3 is a fucosyltransferase. Thus, A111/114R is the protein likely responsible for the attachment of three of the five conserved residues of the core region of this complex glycan, and, if biochemically corroborated, it would be the second three-domain protein coded by PBCV-1 that is involved in glycan synthesis. Importantly, these findings provide additional support that the chloroviruses do not use the canonical host endoplasmic reticulum–Golgi glycosylation pathway to glycosylate their glycoproteins; instead, they perform glycosylation independent of cellular organelles using virus-encoded enzymes.
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33
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Rozenberg A, Oppermann J, Wietek J, Fernandez Lahore RG, Sandaa RA, Bratbak G, Hegemann P, Béjà O. Lateral Gene Transfer of Anion-Conducting Channelrhodopsins between Green Algae and Giant Viruses. Curr Biol 2020; 30:4910-4920.e5. [DOI: 10.1016/j.cub.2020.09.056] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 08/31/2020] [Accepted: 09/17/2020] [Indexed: 12/15/2022]
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34
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Krupovic M, Yutin N, Koonin E. Evolution of a major virion protein of the giant pandoraviruses from an inactivated bacterial glycoside hydrolase. Virus Evol 2020; 6:veaa059. [PMID: 33686356 DOI: 10.1093/ve/veaa059] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The diverse viruses in the phylum Nucleocytoviricota (also known as NLCDVs, Nucleo-cytoplasmic Large DNA Viruses) typically possess large icosahedral virions. However, in several families of Nucleocytoviricota, the icosahedral capsid was replaced by irregular particle shapes, most notably, the amphora-like virions of pandoraviruses and pithoviruses, the largest known virus particles in the entire virosphere. Pandoraviruses appear to be the most highly derived viruses in this phylum because their evolution involved not only the change in the virion shape, but also, the actual loss of the gene encoding double-jelly roll major capsid protein (DJR MCP), the main building block of icosahedral capsids in this virus assemblage. Instead, pandoravirus virions are built of unrelated abundant proteins. Here we show that the second most abundant virion protein of pandoraviruses, major virion protein 2 (MVP2), evolved from an inactivated derivative of a bacterial glycoside hydrolase of the GH16 family. The ancestral form of MVP2 was apparently acquired early in the evolution of the Nucleocytoviricota, to become a minor virion protein. After a duplication in the common ancestor of pandoraviruses and molliviruses, one of the paralogs displaces DJR MCP in pandoraviruses, conceivably, opening the way for a major increase in the size of the virion and the genome. Exaptation of a carbohydrate-binding protein for the function of the MVP is a general trend in virus evolution and might underlie the transformation of the virion shape in other groups of the Nucleocytoviricota as well.
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Affiliation(s)
- Mart Krupovic
- Department of Microbiology, Archaeal Virology Unit, Institut Pasteur, Paris 75015, France
| | - Natalya Yutin
- National Library of Medicine, National Center for Biotechnology Information, National Institutes of Health, Bethesda, MD 20894, USA
| | - Eugene Koonin
- National Library of Medicine, National Center for Biotechnology Information, National Institutes of Health, Bethesda, MD 20894, USA
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35
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Sun TW, Yang CL, Kao TT, Wang TH, Lai MW, Ku C. Host Range and Coding Potential of Eukaryotic Giant Viruses. Viruses 2020; 12:E1337. [PMID: 33233432 PMCID: PMC7700475 DOI: 10.3390/v12111337] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Revised: 11/19/2020] [Accepted: 11/19/2020] [Indexed: 12/11/2022] Open
Abstract
Giant viruses are a group of eukaryotic double-stranded DNA viruses with large virion and genome size that challenged the traditional view of virus. Newly isolated strains and sequenced genomes in the last two decades have substantially advanced our knowledge of their host diversity, gene functions, and evolutionary history. Giant viruses are now known to infect hosts from all major supergroups in the eukaryotic tree of life, which predominantly comprises microbial organisms. The seven well-recognized viral clades (taxonomic families) have drastically different host range. Mimiviridae and Phycodnaviridae, both with notable intrafamilial genome variation and high abundance in environmental samples, have members that infect the most diverse eukaryotic lineages. Laboratory experiments and comparative genomics have shed light on the unprecedented functional potential of giant viruses, encoding proteins for genetic information flow, energy metabolism, synthesis of biomolecules, membrane transport, and sensing that allow for sophisticated control of intracellular conditions and cell-environment interactions. Evolutionary genomics can illuminate how current and past hosts shape viral gene repertoires, although it becomes more obscure with divergent sequences and deep phylogenies. Continued works to characterize giant viruses from marine and other environments will further contribute to our understanding of their host range, coding potential, and virus-host coevolution.
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Affiliation(s)
- Tsu-Wang Sun
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan; (T.-W.S.); (C.-L.Y.); (T.-T.K.); (T.-H.W.); (M.-W.L.)
- Genome and Systems Biology Degree Program, National Taiwan University and Academia Sinica, Taipei 10617, Taiwan
| | - Chia-Ling Yang
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan; (T.-W.S.); (C.-L.Y.); (T.-T.K.); (T.-H.W.); (M.-W.L.)
| | - Tzu-Tong Kao
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan; (T.-W.S.); (C.-L.Y.); (T.-T.K.); (T.-H.W.); (M.-W.L.)
| | - Tzu-Haw Wang
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan; (T.-W.S.); (C.-L.Y.); (T.-T.K.); (T.-H.W.); (M.-W.L.)
| | - Ming-Wei Lai
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan; (T.-W.S.); (C.-L.Y.); (T.-T.K.); (T.-H.W.); (M.-W.L.)
| | - Chuan Ku
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan; (T.-W.S.); (C.-L.Y.); (T.-T.K.); (T.-H.W.); (M.-W.L.)
- Genome and Systems Biology Degree Program, National Taiwan University and Academia Sinica, Taipei 10617, Taiwan
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36
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Speciale I, Laugieri ME, Noel E, Lin S, Lowary TL, Molinaro A, Duncan GA, Agarkova IV, Garozzo D, Tonetti MG, Van Etten JL, De Castro C. Chlorovirus PBCV-1 protein A064R has three of the transferase activities necessary to synthesize its capsid protein N-linked glycans. Proc Natl Acad Sci U S A 2020; 117:28735-28742. [PMID: 33139538 PMCID: PMC7682578 DOI: 10.1073/pnas.2016626117] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Paramecium bursaria chlorella virus-1 (PBCV-1) is a large double-stranded DNA (dsDNA) virus that infects the unicellular green alga Chlorella variabilis NC64A. Unlike many other viruses, PBCV-1 encodes most, if not all, of the enzymes involved in the synthesis of the glycans attached to its major capsid protein. Importantly, these glycans differ from those reported from the three domains of life in terms of structure and asparagine location in the sequon of the protein. Previous data collected from 20 PBCV-1 spontaneous mutants (or antigenic variants) suggested that the a064r gene encodes a glycosyltransferase (GT) with three domains, each with a different function. Here, we demonstrate that: domain 1 is a β-l-rhamnosyltransferase; domain 2 is an α-l-rhamnosyltransferase resembling only bacterial proteins of unknown function, and domain 3 is a methyltransferase that methylates the C-2 hydroxyl group of the terminal α-l-rhamnose (Rha) unit. We also establish that methylation of the C-3 hydroxyl group of the terminal α-l-Rha is achieved by another virus-encoded protein A061L, which requires an O-2 methylated substrate. This study, thus, identifies two of the glycosyltransferase activities involved in the synthesis of the N-glycan of the viral major capsid protein in PBCV-1 and establishes that a single protein A064R possesses the three activities needed to synthetize the 2-OMe-α-l-Rha-(1→2)-β-l-Rha fragment. Remarkably, this fragment can be attached to any xylose unit.
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Affiliation(s)
- Immacolata Speciale
- Department of Chemical Sciences, University of Napoli Federico II, 80126 Napoli, Italy
- Department of Agricultural Sciences, University of Napoli Federico II, 80055 Portici NA, Italy
| | - Maria Elena Laugieri
- Department of Experimental Medicine and Center of Excellence for Biomedical Research, University of Genova, 16132 Genova, Italy
| | - Eric Noel
- Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68583-0900
- School of Biological Sciences, University of Nebraska, Lincoln, NE 68588-0118
| | - Sicheng Lin
- Department of Chemistry, University of Alberta, Gunning-Lemieux Chemistry Centre, Edmonton, AB T6G 2G2 , Canada
| | - Todd L Lowary
- Department of Chemistry, University of Alberta, Gunning-Lemieux Chemistry Centre, Edmonton, AB T6G 2G2 , Canada
- Institute of Biological Chemistry, Academia Sinica, Nangang, 11529 Taipei, Taiwan
| | - Antonio Molinaro
- Department of Chemical Sciences, University of Napoli Federico II, 80126 Napoli, Italy
| | - Garry A Duncan
- Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68583-0900
| | - Irina V Agarkova
- Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68583-0900
- Department of Plant Pathology, University of Nebraska, Lincoln, NE 68583-0722
| | - Domenico Garozzo
- CNR, Institute for Polymers, Composites and Biomaterials, 95126 Catania, Italy
| | - Michela G Tonetti
- Department of Experimental Medicine and Center of Excellence for Biomedical Research, University of Genova, 16132 Genova, Italy;
| | - James L Van Etten
- Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68583-0900;
- Department of Plant Pathology, University of Nebraska, Lincoln, NE 68583-0722
| | - Cristina De Castro
- Department of Agricultural Sciences, University of Napoli Federico II, 80055 Portici NA, Italy;
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Duncan GA, Dunigan DD, Van Etten JL. Diversity of tRNA Clusters in the Chloroviruses. Viruses 2020; 12:v12101173. [PMID: 33081353 PMCID: PMC7589089 DOI: 10.3390/v12101173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 10/12/2020] [Accepted: 10/12/2020] [Indexed: 11/25/2022] Open
Abstract
Viruses rely on their host’s translation machinery for the synthesis of their own proteins. Problems belie viral translation when the host has a codon usage bias (CUB) that is different from an infecting virus due to differences in the GC content between the host and virus genomes. Here, we examine the hypothesis that chloroviruses adapted to host CUB by acquisition and selection of tRNAs that at least partially favor their own CUB. The genomes of 41 chloroviruses comprising three clades, each infecting a different algal host, have been sequenced, assembled and annotated. All 41 viruses not only encode tRNAs, but their tRNA genes are located in clusters. While differences were observed between clades and even within clades, seven tRNA genes were common to all three clades of chloroviruses, including the tRNAArg gene, which was found in all 41 chloroviruses. By comparing the codon usage of one chlorovirus algal host, in which the genome has been sequenced and annotated (67% GC content), to that of two of its viruses (40% GC content), we found that the viruses were able to at least partially overcome the host’s CUB by encoding tRNAs that recognize AU-rich codons. Evidence presented herein supports the hypothesis that a chlorovirus tRNA cluster was present in the most recent common ancestor (MRCA) prior to divergence into three clades. In addition, the MRCA encoded a putative isoleucine lysidine synthase (TilS) that remains in 39/41 chloroviruses examined herein, suggesting a strong evolutionary pressure to retain the gene. TilS alters the anticodon of tRNAMet that normally recognizes AUG to then recognize AUA, a codon for isoleucine. This is advantageous to the chloroviruses because the AUA codon is 12–13 times more common in the chloroviruses than their host, further helping the chloroviruses to overcome CUB. Among large DNA viruses infecting eukaryotes, the presence of tRNA genes and tRNA clusters appear to be most common in the Phycodnaviridae and, to a lesser extent, in the Mimiviridae.
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Affiliation(s)
- Garry A. Duncan
- Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE 68583-0900, USA; (G.A.D.); (D.D.D.)
| | - David D. Dunigan
- Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE 68583-0900, USA; (G.A.D.); (D.D.D.)
- Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE 68583-0833, USA
| | - James L. Van Etten
- Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE 68583-0900, USA; (G.A.D.); (D.D.D.)
- Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE 68583-0833, USA
- Correspondence: ; Tel.: +1-402-472-3168
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Claverie JM. Fundamental Difficulties Prevent the Reconstruction of the Deep Phylogeny of Viruses. Viruses 2020; 12:E1130. [PMID: 33036160 PMCID: PMC7600955 DOI: 10.3390/v12101130] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 10/01/2020] [Accepted: 10/03/2020] [Indexed: 12/11/2022] Open
Abstract
The extension of virology beyond its traditional medical, veterinary, or agricultural applications, now called environmental virology, has shown that viruses are both the most numerous and diverse biological entities on Earth. In particular, virus isolations from unicellular eukaryotic hosts (heterotrophic and photosynthetic protozoans) revealed numerous viral types previously unexpected in terms of virion structure, gene content, or mode of replication. Complemented by large-scale metagenomic analyses, these discoveries have rekindled interest in the enigma of the origin of viruses, for which a description encompassing all their diversity remains not available. Several laboratories have repeatedly tackled the deep reconstruction of the evolutionary history of viruses, using various methods of molecular phylogeny applied to the few shared "core" genes detected in certain virus groups (e.g., the Nucleocytoviricota). Beyond the practical difficulties of establishing reliable homology relationships from extremely divergent sequences, I present here conceptual arguments highlighting several fundamental limitations plaguing the reconstruction of the deep evolutionary history of viruses, and even more the identification of their unique or multiple origin(s). These arguments also underline the risk of establishing premature high level viral taxonomic classifications. Those limitations are direct consequences of the random mechanisms governing the reductive/retrogressive evolution of all obligate intracellular parasites.
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Affiliation(s)
- Jean-Michel Claverie
- Structural & Genomic Information Laboratory (IGS, UMR 7256), Mediterranean Institute of Microbiology (FR3479), Aix-Marseille University and CNRS, 13288 Marseille, France
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Dolja VV, Krupovic M, Koonin EV. Deep Roots and Splendid Boughs of the Global Plant Virome. ANNUAL REVIEW OF PHYTOPATHOLOGY 2020; 58:23-53. [PMID: 32459570 DOI: 10.1146/annurev-phyto-030320-041346] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Land plants host a vast and diverse virome that is dominated by RNA viruses, with major additional contributions from reverse-transcribing and single-stranded (ss) DNA viruses. Here, we introduce the recently adopted comprehensive taxonomy of viruses based on phylogenomic analyses, as applied to the plant virome. We further trace the evolutionary ancestry of distinct plant virus lineages to primordial genetic mobile elements. We discuss the growing evidence of the pivotal role of horizontal virus transfer from invertebrates to plants during the terrestrialization of these organisms, which was enabled by the evolution of close ecological associations between these diverse organisms. It is our hope that the emerging big picture of the formation and global architecture of the plant virome will be of broad interest to plant biologists and virologists alike and will stimulate ever deeper inquiry into the fascinating field of virus-plant coevolution.
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Affiliation(s)
- Valerian V Dolja
- Department of Botany and Plant Pathology and Center for Genome Research and Biocomputing, Oregon State University, Corvallis, Oregon 97331-2902, USA;
| | - Mart Krupovic
- Archaeal Virology Unit, Department of Microbiology, Institut Pasteur, 75015 Paris, France
| | - Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland 20894, USA
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Genetic Diversity of Potassium Ion Channel Proteins Encoded by Chloroviruses That Infect Chlorella heliozoae. Viruses 2020; 12:v12060678. [PMID: 32585987 PMCID: PMC7354518 DOI: 10.3390/v12060678] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 06/18/2020] [Accepted: 06/19/2020] [Indexed: 12/17/2022] Open
Abstract
Chloroviruses are large, plaque-forming, dsDNA viruses that infect chlorella-like green algae that live in a symbiotic relationship with protists. Chloroviruses have genomes from 290 to 370 kb, and they encode as many as 400 proteins. One interesting feature of chloroviruses is that they encode a potassium ion (K+) channel protein named Kcv. The Kcv protein encoded by SAG chlorovirus ATCV-1 is one of the smallest known functional K+ channel proteins consisting of 82 amino acids. The KcvATCV-1 protein has similarities to the family of two transmembrane domain K+ channel proteins; it consists of two transmembrane α-helixes with a pore region in the middle, making it an ideal model for studying K+ channels. To assess their genetic diversity, kcv genes were sequenced from 103 geographically distinct SAG chlorovirus isolates. Of the 103 kcv genes, there were 42 unique DNA sequences that translated into 26 new Kcv channels. The new predicted Kcv proteins differed from KcvATCV-1 by 1 to 55 amino acids. The most conserved region of the Kcv protein was the filter, the turret and the pore helix were fairly well conserved, and the outer and the inner transmembrane domains of the protein were the most variable. Two of the new predicted channels were shown to be functional K+ channels.
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