Abstract:The genus Coccolithovirus is a recently discovered group of viruses that infect the globally important marine calcifying microalga Emiliania huxleyi. Among the 472 predicted genes of the 407,339-base pair genome are a variety of unexpected genes, most notably those involved in biosynthesis of ceramide, a sphingolipid known to induce apoptosis. Uniquely for algal viruses, it also contains six RNA polymerase subunits and a novel promoter, suggesting this virus encodes its own transcription machinery. Microarray … Show more
“…It is intriguing that, so far, not much interest has been devoted to the lipid inventory of viruses, much in contrast to viral genomes and proteins. This is largely due to the fact that only very few virus encoded lipid enzymes are known [6]. Instead, viruses derive their lipids from the host.…”
The cell biology of intracellular pathogens (viruses, bacteria, eukaryotic parasites) has provided us with molecular information of host-pathogen interactions. As a result it is becoming increasingly evident that lipids play important roles at various stages of host-pathogen interactions. They act in first line recognition and host cell signaling during pathogen docking, invasion and intracellular trafficking. Lipid metabolism is a housekeeping function in energy homeostasis and biomembrane synthesis during pathogen replication and persistence. Lipids of enormous chemical diversity play roles as immunomodulatory factors. Thus, novel biochemical analytics in combination with cell and molecular biology are a promising recipe for dissecting the roles of lipids in host-pathogen interactions.
“…It is intriguing that, so far, not much interest has been devoted to the lipid inventory of viruses, much in contrast to viral genomes and proteins. This is largely due to the fact that only very few virus encoded lipid enzymes are known [6]. Instead, viruses derive their lipids from the host.…”
The cell biology of intracellular pathogens (viruses, bacteria, eukaryotic parasites) has provided us with molecular information of host-pathogen interactions. As a result it is becoming increasingly evident that lipids play important roles at various stages of host-pathogen interactions. They act in first line recognition and host cell signaling during pathogen docking, invasion and intracellular trafficking. Lipid metabolism is a housekeeping function in energy homeostasis and biomembrane synthesis during pathogen replication and persistence. Lipids of enormous chemical diversity play roles as immunomodulatory factors. Thus, novel biochemical analytics in combination with cell and molecular biology are a promising recipe for dissecting the roles of lipids in host-pathogen interactions.
“…A range of different viruses that infect E. huxleyi (EhV) were isolated from the English Channel and off the coast of Bergen, Norway (Castberg et al, 2002, Wilson et al, 2002b and were analysed for their phylogeny (Schroeder et al, 2002), ecological successions in mesocosm experiment (Schroeder et al, 2003) and genome structure (EhV-86) (Allen et al, 2006, Wilson et al, 2005. Characterization of their sequences revealed that the E. huxleyi viruses are large double-stranded DNA viruses with genomes approximately 410 kbp in size and that they belong to a new virus genus termed Coccolithovirus based on the phylogeny of their DNA-polymerase gene (Schroeder et al, 2002).…”
Section: Introductionmentioning
confidence: 99%
“…Characterization of their sequences revealed that the E. huxleyi viruses are large double-stranded DNA viruses with genomes approximately 410 kbp in size and that they belong to a new virus genus termed Coccolithovirus based on the phylogeny of their DNA-polymerase gene (Schroeder et al, 2002). Coccolithoviruses belong to the Phycodnaviridae (Wilson et al, 2005), a diverse family of large icosahedral viruses that infect marine or freshwater eukaryotic algae. They all contain dsDNA genomes ranging from 180-560 kb (Van Etten et al, 2002).…”
Blooms of the coccolithophorid Emiliania huxleyi can be infected by viruses, which can lead to bloom-termination. This pilot study used an expressed sequence tag (EST) approach to get a first view of gene-expression changes that occur during viral infection of E. huxleyi. cDNA libraries were constructed from uninfected cultures and 6, 12, and 24 h after infection with E. huxleyi-specific virus 86 (EhV-86). From each library 60-90 ESTs were randomly selected and annotated manually with PhyloGena. Viral genes were identified using BLAST-Search of the known viral genome. The data of this study show, that 6 h after viral infection the algal transcriptome changed significantly although few viral transcripts were present. At this point, changes mainly concerned transcripts related to photosynthesis and protein metabolism. However, after 24 h viral transcripts were most abundant. Viral transcripts found at this stage of viral infection encode proteins involved in protein degradation, nucleic acid degradation, transcription and replication.
“…E. huxleyi blooms are routinely infected and terminated by specific giant double-stranded DNA coccolithoviruses (Phycodnaviridae) (Bratbak et al, 1993;Brussaard et al, 1996;Schroeder et al, 2002;Wilson et al, 2002;Lehahn et al, 2014), the E. huxleyi virus (EhV), which is part of the nucleocytoplasmic large DNA virus (Asfarviridae, Ascoviridae, Iridoviridae, Marseilleviridae, Megaviridae, Mimiviridae, Pandoraviridae, Phycodnaviridae, Pithoviridae and Poxviridae) clade. EhV encodes for an almost complete de-novo biosynthetic pathway for ceramide (Wilson et al, 2005), a sphingolipid known to induce apoptosis in animals and plants (Pettus et al, 2002;Liang et al, 2003). This pathway was recently shown to have a critical role in EhV replication and in induction of E. huxleyi programmed cell death in cultures and during natural bloom demise (Pagarete et al, 2009;Vardi et al, 2009Vardi et al, , 2012.…”
The cosmopolitan coccolithophore Emiliania huxleyi is a unicellular eukaryotic alga responsible for vast blooms in the ocean. These blooms have immense impact on large biogeochemical cycles and are terminated by a specific large double-stranded DNA E. huxleyi virus (EhV, Phycodnaviridae). EhV infection is accompanied by induction of hallmarks of programmed cell death and production of reactive oxygen species (ROS). Here we characterized alterations in ROS metabolism and explored its role during infection. Transcriptomic analysis of ROS-related genes predicted an increase in glutathione (GSH) and H 2 O 2 production during infection. In accordance, using biochemical assays and specific fluorescent probes we demonstrated the overproduction of GSH during lytic infection. We also showed that H 2 O 2 production, rather than superoxide, is the predominant ROS during the onset of the lytic phase of infection. Using flow cytometry, confocal microscopy and multispectral imaging flow cytometry, we showed that the profound co-production of H 2 O 2 and GSH occurred in the same subpopulation of cells but at different subcellular localization. Positively stained cells for GSH and H 2 O 2 were highly infected compared with negatively stained cells. Inhibition of ROS production by application of a peroxidase inhibitor or an H 2 O 2 scavenger inhibited host cell death and reduced viral production. We conclude that viral infection induced remodeling of the host antioxidant network that is essential for a successful viral replication cycle. This study provides insight into viral replication strategy and suggests the use of specific cellular markers to identify and quantify the extent of active viral infection during E. huxleyi blooms in the ocean.
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