The Big Bang of picorna-like virus evolution antedates the radiation of eukaryotic supergroups

• Published in: Nature reviews. Microbiology 2008-12, Vol.6 (12), p.925-939
• Main Authors: Koonin, Eugene V, Dolja, Valerian V, Wolf, Yuri I, Nagasaki, Keizo
• Format: Article
• Language: English
• Subjects: Analysis; Animals; Biological Evolution; Biomedical and Life Sciences; Deoxyribonucleic acid; DNA; Eukaryotes; Eukaryotic Cells - virology; Evolution; Fisheries; Genome, Viral; Genomes; Genomics; Host-Pathogen Interactions - genetics; Infectious Diseases; Life Sciences; Medical Microbiology; Microbiology; Models, Biological; Molecular evolution; Parasitology; Phylogeny; Physiological aspects; Picorna-like virus; Picornaviridae - classification; Picornaviridae - enzymology; Picornaviridae - genetics; Radiation; RNA Helicases - genetics; RNA viruses; RNA-Directed DNA Polymerase - genetics; Virology; Viruses
• ISSN: 1740-1526; 1740-1534
• DOI: 10.1038/nrmicro2030

Key Points RNA viruses, which are most common in eukaryotes, are among the simplest forms of life. Genomic and metagenomic studies have highlighted remarkable diversity of a major class of RNA viruses, the extended picornavirus-like superfamily. Phylogenetic analysis reveals close evolutionary relationships between RNA viruses infecting unicellular eukaryotes and distinct families of picorna-like viruses of plants and animals. This suggests that diversification of picorna-like viruses antedated radiation of the eukaryotes and probably occurred in a 'Big Bang' concomitant with the key events of eukaryogenesis. The origins of the conserved genes of picorna-like viruses can be traced to specific prokaryotic ancestors. The Big Bang of picorna-like virus evolution might have been triggered by chance assembly of these ancestral genes at the earliest stages of eukaryogenesis. The vast resource of viral genome sequences has been exploited to carry out a genomic comparison and phylogenetic analysis of the picorna-like superfamily. The authors conclude that the diverse groups of picorna-like viruses probably evolved in a 'Big Bang' that came after the evolution of the main groups of eukaryotes. The recent discovery of RNA viruses in diverse unicellular eukaryotes and developments in evolutionary genomics have provided the means for addressing the origin of eukaryotic RNA viruses. The phylogenetic analyses of RNA polymerases and helicases presented in this Analysis article reveal close evolutionary relationships between RNA viruses infecting hosts from the Chromalveolate and Excavate supergroups and distinct families of picorna-like viruses of plants and animals. Thus, diversification of picorna-like viruses probably occurred in a 'Big Bang' concomitant with key events of eukaryogenesis. The origins of the conserved genes of picorna-like viruses are traced to likely ancestors including bacterial group II retroelements, the family of HtrA proteases and DNA bacteriophages.