title: Hijacking of an autophagy-like process is critical for the life cycle of a DNA virus infecting oceanic algal blooms.
abstract: Marine photosynthetic microorganisms are the basis of marine food webs and are responsible for nearly 50% of the global primary production. Emiliania huxleyi forms massive oceanic blooms that are routinely terminated by large double-stranded DNA coccolithoviruses. The cellular mechanisms that govern the replication cycle of these giant viruses are largely unknown. We used diverse techniques, including fluorescence microscopy, transmission electron microscopy, cryoelectron tomography, immunolabeling and biochemical methodologies to investigate the role of autophagy in host-virus interactions. Hallmarks of autophagy are induced during the lytic phase of E. huxleyi viral infection, concomitant with up-regulation of autophagy-related genes (ATG genes). Pretreatment of the infected cells with an autophagy inhibitor causes a major reduction in the production of extracellular viral particles, without reducing viral DNA replication within the cell. The host-encoded Atg8 protein was detected within purified virions, demonstrating the pivotal role of the autophagy-like process in viral assembly and egress. We show that autophagy, which is classically considered as a defense mechanism, is essential for viral propagation and for facilitating a high burst size. This cellular mechanism may have a major impact on the fate of the viral-infected blooms, and therefore on the cycling of nutrients within the marine ecosystem.
authors.affiliation: Department of Plant Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel.
authors.forename: Daniella
authors.initials: D
authors.lastname: Schatz
authors.forename: Adva
authors.initials: A
authors.lastname: Shemi
authors.forename: Shilo
authors.initials: S
authors.lastname: Rosenwasser
authors.forename: Helena
authors.initials: H
authors.lastname: Sabanay
authors.forename: Sharon G
authors.initials: SG
authors.lastname: Wolf
authors.forename: Shifra
authors.initials: S
authors.lastname: Ben-Dor
authors.forename: Assaf
authors.initials: A
authors.lastname: Vardi
mesh_terms: D001343:Autophagy; D004267:DNA Viruses / Q000472:pathogenicity* / Q000502:physiology* / Q000648:ultrastructure; D005068:Eutrophication / Q000502:physiology*; D005786:Gene Expression Regulation; D058087:Haptophyta / Q000648:ultrastructure / Q000821:virology*; D054884:Host-Pathogen Interactions; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D012623:Seawater; D015854:Up-Regulation; D014771:Virion / Q000302:isolation & purification / Q000378:metabolism; D014779:Virus Replication
chemical_list: D008869:Microtubule-Associated Proteins
keywords: Atg8; Emiliani huxleyi; Emiliania huxleyi virus; algal blooms; autophagy; coccolithophores; nucleocytoplasmic large DNA Virus