title: Host-virus dynamics and subcellular controls of cell fate in a natural coccolithophore population.
abstract: Marine viruses are major evolutionary and biogeochemical drivers in marine microbial foodwebs. However, an in-depth understanding of the cellular mechanisms and the signal transduction pathways mediating host-virus interactions during natural bloom dynamics has remained elusive. We used field-based mesocosms to examine the "arms race" between natural populations of the coccolithophore Emiliania huxleyi and its double-stranded DNA-containing coccolithoviruses (EhVs). Specifically, we examined the dynamics of EhV infection and its regulation of cell fate over the course of bloom development and demise using a diverse suite of molecular tools and in situ fluorescent staining to target different levels of subcellular resolution. We demonstrate the concomitant induction of reactive oxygen species, caspase-specific activity, metacaspase expression, and programmed cell death in response to the accumulation of virus-derived glycosphingolipids upon infection of natural E. huxleyi populations. These subcellular responses to viral infection simultaneously resulted in the enhanced production of transparent exopolymer particles, which can facilitate aggregation and stimulate carbon flux. Our results not only corroborate the critical role for glycosphingolipids and programmed cell death in regulating E. huxleyi-EhV interactions, but also elucidate promising molecular biomarkers and lipid-based proxies for phytoplankton host-virus interactions in natural systems.
authors.affiliation: Environmental Biophysics and Molecular Ecology Group, Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ 08901, USA.
authors.forename: Assaf
authors.initials: A
authors.lastname: Vardi
authors.forename: Liti
authors.initials: L
authors.lastname: Haramaty
authors.forename: Benjamin A S
authors.initials: BA
authors.lastname: Van Mooy
authors.forename: Helen F
authors.initials: HF
authors.lastname: Fredricks
authors.forename: Susan A
authors.initials: SA
authors.lastname: Kimmance
authors.forename: Aud
authors.initials: A
authors.lastname: Larsen
authors.forename: Kay D
authors.initials: KD
authors.lastname: Bidle
mesh_terms: D001704:Biopolymers / Q000096:biosynthesis; D020169:Caspases / Q000378:metabolism; D019070:Cell Lineage; D004789:Enzyme Activation; D005068:Eutrophication; D058087:Haptophyta / Q000166:cytology* / Q000201:enzymology / Q000821:virology*; D054884:Host-Pathogen Interactions / Q000502:physiology*; D009664:Norway; D017862:Phycodnaviridae / Q000502:physiology*; D013347:Subcellular Fractions / Q000821:virology; D013997:Time Factors
chemical_list: D001704:Biopolymers; D020169:Caspases