Rewiring Host Lipid Metabolism by Large Viruses Determines the Fate of Emiliania huxleyi, a Bloom-Forming Alga in the Ocean    

Abstract

Marine viruses are major ecological and evolutionary drivers of microbial food webs regulating the fate of carbon in the ocean. We combined transcriptomic and metabolomic analyses to explore the cellular pathways mediating the interaction between the bloom-forming coccolithophore Emiliania huxleyi and its specific coccolithoviruses (E. huxleyi virus [EhV]). We show that EhV induces profound transcriptome remodeling targeted toward fatty acid synthesis to support viral assembly. A metabolic shift toward production of viral-derived sphingolipids was detected during infection and coincided with downregulation of host de novo sphingolipid genes and induction of the viral-encoded homologous pathway. The depletion of host-specific sterols during lytic infection and their detection in purified virions revealed their novel role in viral life cycle. We identify an essential function of the mevalonate-isoprenoid branch of sterol biosynthesis during infection and propose its downregulation as an antiviral mechanism. We demonstrate how viral replication depends on the hijacking of host lipid metabolism during the chemical "arms race" in the ocean.

Bridging the Gap between Knowing and Modeling Viruses in Marine Systems—An Upcoming Frontier

“…But until quantitative data on virus-host interaction becomes available, in silico studies will keep on being a valid way, and possible the only, to test hypothesis and to increase our knowledge on the roles of viruses in microbial food webs. Finally, the specificity host-virus relationships and their complexity (Schroeder et al, 2003;Pagarete et al, 2009;Rosenwasser et al, 2014) means that the simple inclusion of viruses as a collective pool in models may be considered too simplistic, or even unrealistic. An objective implication of these relationships is that viruses can only be modeled against their specific hosts, meaning that both viruses and hosts needs to be explicitly modeled.…”

“…As elegant as these solutions may be, their realism can be questioned. As studies reveal new details on virus-host dynamics (Schroeder et al, 2003;Martínez et al, 2007;Rosenwasser et al, 2014), the simple assumption that it is possible to mimic host infection and lysis, using only a density-dependent term is being replaced by a more elaborated view of viral dynamics. Environmental conditions are known to influence viral decay rates and latent period between infection and lysis, for example, thus shaping virus-host interactions.…”

Host-derived viral transporter protein for nitrogen uptake in infected marine phytoplankton

“…lipid biosynthesis of eukaryotic algal cells (25)(26)(27). AMGs are thought to modulate host function to improve fitness of the virus and, in some cases, temporarily the host.…”

Modulation of host ROS metabolism is essential for viral infection of a bloom-forming coccolithophore in the ocean

“…TBlastN hits on the E. huxleyi genome were manually defined, aligned and compared with different closely related sequences as previously described by Feldmesser et al (2014). Expression data for putative genes participating in ROS and antioxidant metabolism was extracted from the database produced by Rosenwasser et al (2014) and presented as the calculated log2 of the expression relative to uninfected control in the same time point.…”

“…Complete DNA sequences of the target genes were manually defined based on genomic sequences, expressed sequence tags and RNA sequencing data as described in the Materials and Methods section. Expression data for each of the defined genes was generated based on RNA sequencing transcriptome analysis of RNA derived from E. huxleyi cells at 1 and 24 h post infection (hpi) with the lytic virus EhV201 or the non-lytic virus EhV163, and normalized to expression levels in uninfected cells at the same time point (Feldmesser et al, 2014;Rosenwasser et al, 2014). Changes were observed in expression levels of several transcripts involved in the biosynthesis and recycling of GSH and ascorbate, important low-molecular-weight antioxidants (Foyer and Noctor, 2005).…”