title: Untangling the origin of viruses and their impact on cellular evolution.
abstract: The origin and evolution of viruses remain mysterious. Here, we focus on the distribution of viral replicons in host organisms, their morphological features, and the evolution of highly conserved protein and nucleic acid structures. The apparent inability of RNA viral replicons to infect contemporary akaryotic species suggests an early origin of RNA viruses and their subsequent loss in akaryotes. A census of virion morphotypes reveals that advanced forms were unique to viruses infecting a specific supergroup, while simpler forms were observed in viruses infecting organisms in all forms of cellular life. Results hint toward an ancient origin of viruses from an ancestral virus harboring either filamentous or spherical virions. Finally, phylogenetic trees built from protein domain and tRNA structures in thousands of genomes suggest that viruses evolved via reductive evolution from ancient cells. The analysis presents a complete account of the evolutionary history of cells and viruses and identifies viruses as crucial agents influencing cellular evolution.
authors.affiliation: Evolutionary Bioinformatics Laboratory, Department of Crop Sciences and Illinois Informatics Institute, University of Illinois, Urbana, Illinois.
authors.forename: Arshan
authors.initials: A
authors.lastname: Nasir
authors.forename: Feng-Jie
authors.initials: FJ
authors.lastname: Sun
authors.forename: Kyung Mo
authors.initials: KM
authors.lastname: Kim
authors.forename: Gustavo
authors.initials: G
authors.lastname: Caetano-Anollés
mesh_terms: D001105:Archaea / Q000235:genetics* / Q000821:virology; D001419:Bacteria / Q000235:genetics* / Q000821:virology; D056890:Eukaryota / Q000235:genetics* / Q000821:virology; D019143:Evolution, Molecular; D054884:Host-Pathogen Interactions / Q000235:genetics; D008957:Models, Genetic; D010802:Phylogeny; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D014779:Virus Replication / Q000235:genetics; D014780:Viruses / Q000145:classification / Q000235:genetics* / Q000378:metabolism
chemical_list: D014764:Viral Proteins
keywords: evolution; parasitism; protein domains; structure; transfer RNA; viruses