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1.
DNA Cell Biol ; 38(11): 1257-1268, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31553224

RESUMO

Recent analyses suggest bacterial and/or mitochondrion-like ancestry for giant viruses (Megavirales sensu latu): amoeban mitochondrial gene arrangements resemble those of their candidate homologs in megaviral genomes. This presumed ancestral synteny decreases with genome size across megaviral families at large and within Poxviridae. In this study, analyses focus on Phycodnaviridae, a polyphyletic group of giant viruses infecting Haplophyta, Stramenopiles, and other algae, using syntenies between algal mitogene arrangements and chloroplast genomes and Rickettsia prowazekii as positive controls. Mitogene alignment qualities with Rickettsia are much higher than with viral genomes. Mitogenome synteny with some viruses is higher, for others lower than with Rickettsia, despite lower alignments qualities. In some algae, syntenies among cohosted chloroplast, virus, and mitochondrion are higher, in others lower than expected. This suggests gene order coevolution in cohosted genomes, different coregulations of organelle metabolisms for different algae, and viral mitogenome mimicry, to hijack organelle-committed cellular resources and/or escape cellular defenses/genetic immunity systems. This principle might explain high synteny between human mitochondria and the pathogenic endocellular alphaproteobacterium R. prowazekii beyond common ancestry. Results indicate that putative bacteria/mitochondrion-like genomic ancestors of Phycodnaviridae originated before or at the mitochondrion-bacteria split, and ulterior functional constraints on gene arrangements of cohosted genomes.


Assuntos
Cloroplastos/genética , Evolução Molecular , Mitocôndrias/genética , Mimetismo Molecular/fisiologia , Phycodnaviridae/genética , Sintenia/genética , Imunidade Adaptativa/genética , Genoma Mitocondrial/genética , Genoma Viral/genética , Interações Hospedeiro-Patógeno/genética , Interações Hospedeiro-Patógeno/imunologia , Evasão da Resposta Imune/genética , Organelas/genética , Filogenia , Análise de Sequência de DNA
2.
PLoS Pathog ; 15(4): e1007708, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-31017983

RESUMO

Infection by large dsDNA viruses can lead to a profound alteration of host transcriptome and metabolome in order to provide essential building blocks to support the high metabolic demand for viral assembly and egress. Host response to viral infection can typically lead to diverse phenotypic outcome that include shift in host life cycle and activation of anti-viral defense response. Nevertheless, there is a major bottleneck to discern between viral hijacking strategies and host defense responses when averaging bulk population response. Here we study the interaction between Emiliania huxleyi, a bloom-forming alga, and its specific virus (EhV), an ecologically important host-virus model system in the ocean. We quantified host and virus gene expression on a single-cell resolution during the course of infection, using automatic microfluidic setup that captures individual algal cells and multiplex quantitate PCR. We revealed high heterogeneity in viral gene expression among individual cells. Simultaneous measurements of expression profiles of host and virus genes at a single-cell level allowed mapping of infected cells into newly defined infection states and allowed detection specific host response in a subpopulation of infected cell which otherwise masked by the majority of the infected population. Intriguingly, resistant cells emerged during viral infection, showed unique expression profiles of metabolic genes which can provide the basis for discerning between viral resistant and susceptible cells within heterogeneous populations in the marine environment. We propose that resolving host-virus arms race at a single-cell level will provide important mechanistic insights into viral life cycles and will uncover host defense strategies.


Assuntos
Eutrofização , Genes Virais , Haptófitas/genética , Haptófitas/virologia , Phycodnaviridae/patogenicidade , Análise de Célula Única/métodos , Viroses/genética , Haptófitas/crescimento & desenvolvimento , Interações Hospedeiro-Patógeno , Phycodnaviridae/genética , Phycodnaviridae/isolamento & purificação , Transcriptoma , Viroses/virologia
3.
J Biol Chem ; 294(14): 5688-5699, 2019 04 05.
Artigo em Inglês | MEDLINE | ID: mdl-30737276

RESUMO

The chlorovirus Paramecium bursaria chlorella virus 1 (PBCV-1) is a large dsDNA virus that infects the microalga Chlorella variabilis NC64A. Unlike most other viruses, PBCV-1 encodes most, if not all, of the machinery required to glycosylate its major capsid protein (MCP). The structures of the four N-linked glycans from the PBCV-1 MCP consist of nonasaccharides, and similar glycans are not found elsewhere in the three domains of life. Here, we identified the roles of three virus-encoded glycosyltransferases (GTs) that have four distinct GT activities in glycan synthesis. Two of the three GTs were previously annotated as GTs, but the third GT was identified in this study. We determined the GT functions by comparing the WT glycan structures from PBCV-1 with those from a set of PBCV-1 spontaneous GT gene mutants resulting in antigenic variants having truncated glycan structures. According to our working model, the virus gene a064r encodes a GT with three domains: domain 1 has a ß-l-rhamnosyltransferase activity, domain 2 has an α-l-rhamnosyltransferase activity, and domain 3 is a methyltransferase that decorates two positions in the terminal α-l-rhamnose (Rha) unit. The a075l gene encodes a ß-xylosyltransferase that attaches the distal d-xylose (Xyl) unit to the l-fucose (Fuc) that is part of the conserved N-glycan core region. Last, gene a071r encodes a GT that is involved in the attachment of a semiconserved element, α-d-Rha, to the same l-Fuc in the core region. Our results uncover GT activities that assemble four of the nine residues of the PBCV-1 MCP N-glycans.


Assuntos
Antígenos Virais/metabolismo , Proteínas do Capsídeo/metabolismo , Chlorella/metabolismo , Glicosiltransferases/metabolismo , Phycodnaviridae/enzimologia , Polissacarídeos/metabolismo , Antígenos Virais/genética , Antígenos Virais/imunologia , Proteínas do Capsídeo/genética , Proteínas do Capsídeo/imunologia , Chlorella/genética , Chlorella/virologia , Glicosiltransferases/genética , Glicosiltransferases/imunologia , Phycodnaviridae/genética , Phycodnaviridae/imunologia , Polissacarídeos/genética , Polissacarídeos/imunologia
4.
J Virol ; 93(7)2019 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-30626679

RESUMO

Chloroviruses exist in aquatic systems around the planet and they infect certain eukaryotic green algae that are mutualistic endosymbionts in a variety of protists and metazoans. Natural chlorovirus populations are seasonally dynamic, but the precise temporal changes in these populations and the mechanisms that underlie them have heretofore been unclear. We recently reported the novel concept that predator/prey-mediated virus activation regulates chlorovirus population dynamics, and in the current study, we demonstrate virus-packaged chemotactic modulation of prey behavior.IMPORTANCE Viruses have not previously been reported to act as chemotactic/chemoattractive agents. Rather, viruses as extracellular entities are generally viewed as non-metabolically active spore-like agents that await further infection events upon collision with appropriate host cells. That a virus might actively contribute to its fate via chemotaxis and change the behavior of an organism independent of infection is unprecedented.


Assuntos
Vírus de DNA/genética , Interações entre Hospedeiro e Microrganismos/genética , Phycodnaviridae/genética , Dinâmica Populacional
5.
Viruses ; 10(12)2018 11 27.
Artigo em Inglês | MEDLINE | ID: mdl-30486388

RESUMO

The St. Lawrence hydrographic system includes freshwater, brackish, and marine habitats, and is the largest waterway in North America by volume. The food-webs in these habitats are ultimately dependent on phytoplankton. Viral lysis is believed to be responsible for a major part of phytoplankton mortality. To better understand their role, we characterized the diversity and distribution of two viral taxa infecting phytoplankton: the picornaviruses and phycodnaviruses. Our study focused on the estuary transition zone, which is an important nursery for invertebrates and fishes. Both viral taxa were investigated by PCR amplification of conserved molecular markers and next-generation sequencing at six sites, ranging from freshwater to marine. Our results revealed few shared viral phylotypes between saltwater and freshwater sites. Salinity appeared to be the primary determinant of viral community composition. Moreover, our analysis indicated that the viruses identified in this region of the St. Lawrence diverge from classified viruses and homologous published environmental virotypes. These results suggest that DNA and RNA viruses infecting phytoplankton are likely active in the estuary transition zone, and that this region harbors its own unique viral assemblages.


Assuntos
Estuários , Fitoplâncton/virologia , Microbiologia da Água , Biodiversidade , Ecossistema , Meio Ambiente , Evolução Molecular , Geografia , Metagenoma , Metagenômica/métodos , Phycodnaviridae/classificação , Phycodnaviridae/genética , Filogenia , RNA Ribossômico 18S
6.
Viruses ; 10(10)2018 10 20.
Artigo em Inglês | MEDLINE | ID: mdl-30347809

RESUMO

Chloroviruses (family Phycodnaviridae) are dsDNA viruses found throughout the world's inland waters. The open reading frames in the genomes of 41 sequenced chloroviruses (330 ± 40 kbp each) representing three virus types were analyzed for evidence of evolutionarily conserved local genomic "contexts", the organization of biological information into units of a scale larger than a gene. Despite a general loss of synteny between virus types, we informatically detected a highly conserved genomic context defined by groups of three or more genes that we have termed "gene gangs". Unlike previously described local genomic contexts, the definition of gene gangs requires only that member genes be consistently co-localized and are not constrained by strand, regulatory sites, or intervening sequences (and therefore represent a new type of conserved structural genomic element). An analysis of functional annotations and transcriptomic data suggests that some of the gene gangs may organize genes involved in specific biochemical processes, but that this organization does not involve their coordinated expression.


Assuntos
Família Multigênica , Phycodnaviridae/genética , Proteínas Virais/genética , Sequência de Bases , Evolução Molecular , Genoma Viral , Fases de Leitura Aberta , Phycodnaviridae/classificação , Filogenia , Sintenia
7.
Viruses ; 10(8)2018 08 19.
Artigo em Inglês | MEDLINE | ID: mdl-30126254

RESUMO

The motivation for focusing on a specific virus is often its importance in terms of impact on human interests. The chlorella viruses are a notable exception and 40 years of research has made them the undisputed model system for large icosahedral dsDNA viruses infecting eukaryotes. Their status has changed from inconspicuous and rather odd with no ecological relevance to being the Phycodnaviridae type strain possibly affecting humans and human cognitive functioning in ways that remain to be understood. The Van Etten legacy is the backbone for research on Phycodnaviridae. After highlighting some of the peculiarities of chlorella viruses, we point to some issues and questions related to the viruses we choose for our research, our prejudices, what we are still missing, and what we should be looking for.


Assuntos
Chlorella/virologia , Paramecium/fisiologia , Phycodnaviridae/genética , Phycodnaviridae/classificação , Phycodnaviridae/isolamento & purificação , Filogenia , Água do Mar , Simbiose , Terminologia como Assunto
8.
Environ Microbiol ; 20(8): 2898-2912, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29749714

RESUMO

Prasinophytes are widespread marine algae for which responses to nutrient limitation and viral infection are not well understood. We studied the picoprasinophyte, Micromonas pusilla, grown under phosphate-replete (0.65 ± 0.07 d-1 ) and 10-fold lower (low)-phosphate (0.11 ± 0.04 d-1 ) conditions, and infected by the phycodnavirus MpV-SP1. Expression of 17% of Micromonas genes in uninfected cells differed by >1.5-fold (q < 0.01) between nutrient conditions, with genes for P-metabolism and the uniquely-enriched Sel1-like repeat (SLR) family having higher relative transcript abundances, while phospholipid-synthesis genes were lower in low-P than P-replete. Approximately 70% (P-replete) and 30% (low-P) of cells were lysed 24 h post-infection, and expression of ≤5.8% of host genes changed relative to uninfected treatments. Host genes for CAZymes and glycolysis were activated by infection, supporting importance in viral production, which was significantly lower in slower growing (low-P) hosts. All MpV-SP1 genes were expressed, and our analyses suggest responses to differing host-phosphate backgrounds involve few viral genes, while the temporal program of infection involves many more, and is largely independent of host-phosphate background. Our study (i) identifies genes previously unassociated with nutrient acclimation or viral infection, (ii) provides insights into the temporal program of prasinovirus gene expression by hosts and (iii) establishes cell biological aspects of an ecologically important host-prasinovirus system that differ from other marine algal-virus systems.


Assuntos
Clorófitas/virologia , Regulação da Expressão Gênica de Plantas , Fosfatos/química , Phycodnaviridae/fisiologia , Transcrição Genética/fisiologia , Organismos Aquáticos , Clorófitas/metabolismo , Fosfatos/metabolismo , Phycodnaviridae/genética
9.
BMC Genomics ; 19(1): 49, 2018 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-29334892

RESUMO

BACKGROUND: Phycodnaviruses are widespread algae-infecting large dsDNA viruses and presently contain six genera: Chlorovirus, Prasinovirus, Prymnesiovirus, Phaeovirus, Coccolithovirus and Raphidovirus. The members in Prasinovirus are identified as marine viruses due to their marine algal hosts, while prasinovirus freshwater relatives remain rarely reported. RESULTS: Here we present the complete genomic sequence of a novel phycodnavirus, Dishui Lake Phycodnavirus 1 (DSLPV1), which was assembled from Dishui Lake metagenomic datasets. DSLPV1 harbors a linear genome of 181,035 bp in length (G + C content: 52.7%), with 227 predicted genes and 2 tRNA encoding regions. Both comparative genomic and phylogenetic analyses indicate that the freshwater algal virus DSLPV1 is closely related to the members in Prasinovirus, a group of marine algae infecting viruses. In addition, a complete eukaryotic histone H3 variant was identified in the genome of DSLPV1, which is firstly detected in phycodnaviruses and contributes to understand the interaction between algal virus and its eukaryotic hosts. CONCLUSION: It is in a freshwater ecosystem that a novel Prasinovirus-related viral complete genomic sequence is discovered, which sheds new light on the evolution and diversity of the algae infecting Phycodnaviridae.


Assuntos
Genoma Viral , Phycodnaviridae/genética , Biodiversidade , Água Doce/virologia , Genes Virais , Histonas/genética , Phycodnaviridae/classificação , Filogenia
10.
Proc Natl Acad Sci U S A ; 114(42): 11193-11198, 2017 10 17.
Artigo em Inglês | MEDLINE | ID: mdl-28973943

RESUMO

Ecosystems are complex food webs in which multiple species interact and ecological and evolutionary processes continuously shape populations and communities. Previous studies on eco-evolutionary dynamics have shown that the presence of intraspecific diversity affects community structure and function, and that eco-evolutionary feedback dynamics can be an important driver for its maintenance. Within communities, feedbacks are, however, often indirect, and they can feed back over many generations. Here, we studied eco-evolutionary feedbacks in evolving communities over many generations and compared two-species systems (virus-host and prey-predator) with a more complex three-species system (virus-host-predator). Both indirect density- and trait-mediated effects drove the dynamics in the complex system, where host-virus coevolution facilitated coexistence of predator and virus, and where coexistence, in return, lowered intraspecific diversity of the host population. Furthermore, ecological and evolutionary dynamics were significantly altered in the three-species system compared with the two-species systems. We found that the predator slowed host-virus coevolution in the complex system and that the virus' effect on the overall population dynamics was negligible when the three species coexisted. Overall, we show that a detailed understanding of the mechanism driving eco-evolutionary feedback dynamics is necessary for explaining trait and species diversity in communities, even in communities with only three species.


Assuntos
Coevolução Biológica , Chlorella/virologia , Cadeia Alimentar , Interações Hospedeiro-Patógeno , Phycodnaviridae/genética , Rotíferos , Animais , Chlorella/genética , Dinâmica Populacional , Seleção Genética
11.
Viruses ; 9(6)2017 06 02.
Artigo em Inglês | MEDLINE | ID: mdl-28574420

RESUMO

Global climate change-induced warming of the Artic seas is predicted to shift the phytoplankton community towards dominance of smaller-sized species due to global warming. Yet, little is known about their viral mortality agents despite the ecological importance of viruses regulating phytoplankton host dynamics and diversity. Here we report the isolation and basic characterization of four prasinoviruses infectious to the common Arctic picophytoplankter Micromonas. We furthermore assessed how temperature influenced viral infectivity and production. Phylogenetic analysis indicated that the putative double-stranded DNA (dsDNA) Micromonas polaris viruses (MpoVs) are prasinoviruses (Phycodnaviridae) of approximately 120 nm in particle size. One MpoV showed intrinsic differences to the other three viruses, i.e., larger genome size (205 ± 2 vs. 191 ± 3 Kb), broader host range, and longer latent period (39 vs. 18 h). Temperature increase shortened the latent periods (up to 50%), increased the burst size (up to 40%), and affected viral infectivity. However, the variability in response to temperature was high for the different viruses and host strains assessed, likely affecting the Arctic picoeukaryote community structure both in the short term (seasonal cycles) and long term (global warming).


Assuntos
Clorófitas/virologia , Phycodnaviridae/fisiologia , Phycodnaviridae/efeitos da radiação , Replicação Viral/efeitos da radiação , Regiões Árticas , DNA Viral/genética , Phycodnaviridae/genética , Temperatura Ambiente
12.
Viruses ; 9(5)2017 05 19.
Artigo em Inglês | MEDLINE | ID: mdl-28534829

RESUMO

Prasinophytes, a group of eukaryotic phytoplankton, has a global distribution and is infected by large double-stranded DNA viruses (prasinoviruses) in the family Phycodnaviridae. This study examines the genetic repertoire, phylogeny, and environmental distribution of phycodnaviruses infecting Micromonas pusilla, other prasinophytes and chlorophytes. Based on comparisons among the genomes of viruses infecting M. pusilla and other phycodnaviruses, as well as the genome from a host isolate of M. pusilla, viruses infecting M. pusilla (MpVs) share a limited set of core genes, but vary strongly in their flexible pan-genome that includes numerous metabolic genes, such as those associated with amino acid synthesis and sugar manipulation. Surprisingly, few of these presumably host-derived genes are shared with M. pusilla, but rather have their closest non-viral homologue in bacteria and other eukaryotes, indicating horizontal gene transfer. A comparative analysis of full-length DNA polymerase (DNApol) genes from prasinoviruses with their overall gene content, demonstrated that the phylogeny of DNApol gene fragments reflects the gene content of the viruses; hence, environmental DNApol gene sequences from prasinoviruses can be used to infer their overall genetic repertoire. Thus, the distribution of virus ecotypes across environmental samples based on DNApol sequences implies substantial underlying differences in gene content that reflect local environmental conditions. Moreover, the high diversity observed in the genetic repertoire of prasinoviruses has been driven by horizontal gene transfer throughout their evolutionary history, resulting in a broad suite of functional capabilities and a high diversity of prasinovirus ecotypes.


Assuntos
Clorófitas/genética , Clorófitas/virologia , Vírus de DNA/genética , Transferência Genética Horizontal/genética , Genoma Viral/genética , Phycodnaviridae/genética , Sequência de Bases , Clorófitas/classificação , DNA Polimerase Dirigida por DNA/genética , Meio Ambiente , Genes Virais , Variação Genética , Biologia Marinha , Phycodnaviridae/classificação , Phycodnaviridae/isolamento & purificação , Phycodnaviridae/patogenicidade , Filogenia , Fitoplâncton/virologia
13.
Viruses ; 9(4)2017 04 22.
Artigo em Inglês | MEDLINE | ID: mdl-28441734

RESUMO

Chloroviruses are large double-stranded DNA (dsDNA) viruses that infect certain isolates of chlorella-like green algae. They contain up to approximately 400 protein-encoding genes and 16 transfer RNA (tRNA) genes. This review summarizes the unexpected finding that many of the chlorovirus genes encode proteins involved in manipulating carbohydrates. These include enzymes involved in making extracellular polysaccharides, such as hyaluronan and chitin, enzymes that make nucleotide sugars, such as GDP-L-fucose and GDP-D-rhamnose and enzymes involved in the synthesis of glycans attached to the virus major capsid proteins. This latter process differs from that of all other glycoprotein containing viruses that traditionally use the host endoplasmic reticulum and Golgi machinery to synthesize and transfer the glycans.


Assuntos
Chlorella/virologia , Genes Virais , Redes e Vias Metabólicas , Phycodnaviridae/genética , Phycodnaviridae/fisiologia , Metabolismo dos Carboidratos
14.
J Virol ; 91(14)2017 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-28446675

RESUMO

Chrysochromulina ericina virus CeV-01B (CeV) was isolated from Norwegian coastal waters in 1998. Its icosahedral particle is 160 nm in diameter and encloses a 474-kb double-stranded DNA (dsDNA) genome. This virus, although infecting a microalga (the haptophyceae Haptolina ericina, formerly Chrysochromulina ericina), is phylogenetically related to members of the Mimiviridae family, initially established with the acanthamoeba-infecting mimivirus and megavirus as prototypes. This family was later split into two genera (Mimivirus and Cafeteriavirus) following the characterization of a virus infecting the heterotrophic stramenopile Cafeteria roenbergensis (CroV). CeV, as well as two of its close relatives, which infect the unicellular photosynthetic eukaryotes Phaeocystis globosa (Phaeocystis globosa virus [PgV]) and Aureococcus anophagefferens (Aureococcus anophagefferens virus [AaV]), are currently unclassified by the International Committee on Viral Taxonomy (ICTV). The detailed comparative analysis of the CeV genome presented here confirms the phylogenetic affinity of this emerging group of microalga-infecting viruses with the Mimiviridae but argues in favor of their classification inside a distinct clade within the family. Although CeV, PgV, and AaV share more common features among them than with the larger Mimiviridae, they also exhibit a large complement of unique genes, attesting to their complex evolutionary history. We identified several gene fusion events and cases of convergent evolution involving independent lateral gene acquisitions. Finally, CeV possesses an unusual number of inteins, some of which are closely related despite being inserted in nonhomologous genes. This appears to contradict the paradigm of allele-specific inteins and suggests that the Mimiviridae are especially efficient in spreading inteins while enlarging their repertoire of homing genes.IMPORTANCE Although it infects the microalga Chrysochromulina ericina, CeV is more closely related to acanthamoeba-infecting viruses of the Mimiviridae family than to any member of the Phycodnaviridae, the ICTV-approved family historically including all alga-infecting large dsDNA viruses. CeV, as well as its relatives that infect the microalgae Phaeocystic globosa (PgV) and Aureococcus anophagefferens (AaV), remains officially unclassified and a source of confusion in the literature. Our comparative analysis of the CeV genome in the context of this emerging group of alga-infecting viruses suggests that they belong to a distinct clade within the established Mimiviridae family. The presence of a large number of unique genes as well as specific gene fusion events, evolutionary convergences, and inteins integrated at unusual locations document the complex evolutionary history of the CeV lineage.


Assuntos
Evolução Molecular , Genoma Viral , Mimiviridae/classificação , Mimiviridae/genética , Phycodnaviridae/classificação , Phycodnaviridae/genética , Filogenia , Análise por Conglomerados , Análise de Sequência de DNA , Homologia de Sequência
15.
Viruses ; 9(3)2017 03 08.
Artigo em Inglês | MEDLINE | ID: mdl-28282890

RESUMO

Effects of elevated pCO2 on Emiliania huxleyi genetic diversity and the viruses that infect E. huxleyi (EhVs) have been investigated in large volume enclosures in a Norwegian fjord. Triplicate enclosures were bubbled with air enriched with CO2 to 760 ppmv whilst the other three enclosures were bubbled with air at ambient pCO2; phytoplankton growth was initiated by the addition of nitrate and phosphate. E. huxleyi was the dominant coccolithophore in all enclosures, but no difference in genetic diversity, based on DGGE analysis using primers specific to the calcium binding protein gene (gpa) were detected in any of the treatments. Chlorophyll concentrations and primary production were lower in the three elevated pCO2 treatments than in the ambient treatments. However, although coccolithophores numbers were reduced in two of the high-pCO2 treatments; in the third, there was no suppression of coccolithophores numbers, which were very similar to the three ambient treatments. In contrast, there was considerable variation in genetic diversity in the EhVs, as determined by analysis of the major capsid protein (mcp) gene. EhV diversity was much lower in the high-pCO2 treatment enclosure that did not show inhibition of E. huxleyi growth. Since virus infection is generally implicated as a major factor in terminating phytoplankton blooms, it is suggested that no study of the effect of ocean acidification in phytoplankton can be complete if it does not include an assessment of viruses.


Assuntos
Variação Genética/efeitos dos fármacos , Haptófitas/classificação , Haptófitas/isolamento & purificação , Phycodnaviridae/classificação , Phycodnaviridae/isolamento & purificação , Água do Mar/microbiologia , Água do Mar/virologia , Dióxido de Carbono/metabolismo , Clorofila/análise , Eletroforese em Gel de Gradiente Desnaturante , Haptófitas/genética , Haptófitas/virologia , Nitratos/metabolismo , Noruega , Fosfatos/metabolismo , Phycodnaviridae/genética , Phycodnaviridae/crescimento & desenvolvimento , Água do Mar/química
16.
Viruses ; 9(3)2017 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-28294997

RESUMO

Viruses play a crucial role in the marine environment, promoting nutrient recycling and biogeochemical cycling and driving evolutionary processes. Tiny marine phytoplankton called prasinophytes are ubiquitous and significant contributors to global primary production and biomass. A number of viruses (known as prasinoviruses) that infect these important primary producers have been isolated and characterised over the past decade. Here we review the current body of knowledge about prasinoviruses and their interactions with their algal hosts. Several genes, including those encoding for glycosyltransferases, methyltransferases and amino acid synthesis enzymes, which have never been identified in viruses of eukaryotes previously, have been detected in prasinovirus genomes. The host organisms are also intriguing; most recently, an immunity chromosome used by a prasinophyte in response to viral infection was discovered. In light of such recent, novel discoveries, we discuss why the cellular simplicity of prasinophytes makes for appealing model host organism-virus systems to facilitate focused and detailed investigations into the dynamics of marine viruses and their intimate associations with host species. We encourage the adoption of the prasinophyte Ostreococcus and its associated viruses as a model host-virus system for examination of cellular and molecular processes in the marine environment.


Assuntos
Organismos Aquáticos/virologia , Clorófitas/virologia , Interações Hospedeiro-Parasita , Phycodnaviridae/fisiologia , Fitoplâncton/virologia , Evolução Biológica , Phycodnaviridae/genética
17.
Viruses ; 9(3)2017 03 18.
Artigo em Inglês | MEDLINE | ID: mdl-28335465

RESUMO

Emiliania huxleyi is the main calcite producer on Earth and is routinely infected by a virus (EhV); a double stranded DNA (dsDNA) virus belonging to the family Phycodnaviridae. E. huxleyi exhibits a haplodiploid life cycle; the calcified diploid stage is non-motile and forms extensive blooms. The haploid phase is a non-calcified biflagellated cell bearing organic scales. Haploid cells are thought to resist infection, through a process deemed the "Cheshire Cat" escape strategy; however, a recent study detected the presence of viral lipids in the same haploid strain. Here we report on the application of an E. huxleyi CCMP1516 EhV-86 combined tiling array (TA) that further confirms an EhV infection in the RCC1217 haploid strain, which grew without any signs of cell lysis. Reverse transcription polymerase chain reaction (RT-PCR) and PCR verified the presence of viral RNA in the haploid cells, yet indicated an absence of viral DNA, respectively. These infected cells are an alternative stage of the virus life cycle deemed the haplococcolithovirocell. In this instance, the host is both resistant to and infected by EhV, i.e., the viral transcriptome is present in haploid cells whilst there is no evidence of viral lysis. This superimposed state is reminiscent of Schrödinger's cat; of being simultaneously both dead and alive.


Assuntos
Haptófitas/virologia , Phycodnaviridae/fisiologia , DNA Viral/análise , Haploidia , Haptófitas/genética , Phycodnaviridae/genética , RNA Viral/análise , Transcriptoma
18.
Viruses ; 9(3)2017 03 18.
Artigo em Inglês | MEDLINE | ID: mdl-28335474

RESUMO

Coccolithoviruses (Phycodnaviridae) infect and lyse the most ubiquitous and successful coccolithophorid in modern oceans, Emiliania huxleyi. So far, the genomes of 13 of these giant lytic viruses (i.e., Emiliania huxleyi viruses-EhVs) have been sequenced, assembled, and annotated. Here, we performed an in-depth comparison of their genomes to try and contextualize the ecological and evolutionary traits of these viruses. The genomes of these EhVs have from 444 to 548 coding sequences (CDSs). Presence/absence analysis of CDSs identified putative genes with particular ecological significance, namely sialidase, phosphate permease, and sphingolipid biosynthesis. The viruses clustered into distinct clades, based on their DNA polymerase gene as well as full genome comparisons. We discuss the use of such clustering and suggest that a gene-by-gene investigation approach may be more useful when the goal is to reveal differences related to functionally important genes. A multi domain "Best BLAST hit" analysis revealed that 84% of the EhV genes have closer similarities to the domain Eukarya. However, 16% of the EhV CDSs were very similar to bacterial genes, contributing to the idea that a significant portion of the gene flow in the planktonic world inter-crosses the domains of life.


Assuntos
Phycodnaviridae/genética , Ecossistema , Evolução Molecular , Transferência Genética Horizontal , Genes Bacterianos , Variação Genética , Tamanho do Genoma , Genoma Viral , Haptófitas/virologia , Phycodnaviridae/classificação , Phycodnaviridae/fisiologia , Filogenia , Análise de Sequência de DNA , Especificidade da Espécie
19.
ISME J ; 11(3): 601-612, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-28085157

RESUMO

The genus Micromonas comprises phytoplankton that show among the widest latitudinal distributions on Earth, and members of this genus are recurrently infected by prasinoviruses in contrasted thermal ecosystems. In this study, we assessed how temperature influences the interplay between the main genetic clades of this prominent microalga and their viruses. The growth of three Micromonas strains (Mic-A, Mic-B, Mic-C) and the stability of their respective lytic viruses (MicV-A, MicV-B, MicV-C) were measured over a thermal range of 4-32.5 °C. Similar growth temperature optima (Topt) were predicted for all three hosts but Mic-B exhibited a broader thermal tolerance than Mic-A and Mic-C, suggesting distinct thermoacclimation strategies. Similarly, the MicV-C virus displayed a remarkable thermal stability compared with MicV-A and MicV-B. Despite these divergences, infection dynamics showed that temperatures below Topt lengthened lytic cycle kinetics and reduced viral yield and, notably, that infection at temperatures above Topt did not usually result in cell lysis. Two mechanisms operated depending on the temperature and the biological system. Hosts either prevented the production of viral progeny or maintained their ability to produce virions with no apparent cell lysis, pointing to a possible switch in the viral life strategy. Hence, temperature changes critically affect the outcome of Micromonas infection and have implications for ocean biogeochemistry and evolution.


Assuntos
Clorófitas/virologia , Phycodnaviridae/fisiologia , Clorófitas/crescimento & desenvolvimento , Ecossistema , Interações Hospedeiro-Patógeno , Phycodnaviridae/classificação , Phycodnaviridae/genética , Fitoplâncton/crescimento & desenvolvimento , Fitoplâncton/virologia , Água do Mar , Temperatura Ambiente , Vírion/fisiologia
20.
FEMS Microbiol Ecol ; 93(1)2017 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-27815287

RESUMO

Rhodopsins are broadly distributed. In this work, we analyzed 23 metagenomes corresponding to marine sediment samples from four regions that share cold climate conditions (Norway; Sweden; Argentina and Antarctica). In order to investigate the genes evolution of viral rhodopsins, an initial set of 6224 bacterial rhodopsin sequences according to COG5524 were retrieved from the 23 metagenomes. After selection by the presence of transmembrane domains and alignment, 123 viral (51) and non-viral (72) sequences (>50 amino acids) were finally included in further analysis. Viral rhodopsin genes were homologs of Phaeocystis globosa virus and Organic lake Phycodnavirus. Non-viral microbial rhodopsin genes were ascribed to Bacteroidetes, Planctomycetes, Firmicutes, Actinobacteria, Cyanobacteria, Proteobacteria, Deinococcus-Thermus and Cryptophyta and Fungi. A rescreening using Blastp, using as queries the viral sequences previously described, retrieved 30 sequences (>100 amino acids). Phylogeographic analysis revealed a geographical clustering of the sequences affiliated to the viral group. This clustering was not observed for the microbial non-viral sequences. The phylogenetic reconstruction allowed us to propose the existence of a putative ancestor of viral rhodopsin genes related to Actinobacteria and Chloroflexi. This is the first report about the existence of a phylogeographic association of the viral rhodopsin sequences from marine sediments.


Assuntos
Bactérias/genética , Fungos/genética , Sedimentos Geológicos/microbiologia , Phycodnaviridae/genética , Água do Mar/microbiologia , Proteínas Virais/genética , Regiões Antárticas , Argentina , Bactérias/classificação , Evolução Molecular , Fungos/classificação , Sedimentos Geológicos/virologia , Metagenoma , Noruega , Phycodnaviridae/classificação , Filogenia , Rodopsina/genética , Água do Mar/virologia , Suécia
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