title: Welcome to pandoraviruses at the 'Fourth TRUC' club.
abstract: Nucleocytoplasmic large DNA viruses, or representatives of the proposed order Megavirales, belong to families of giant viruses that infect a broad range of eukaryotic hosts. Megaviruses have been previously described to comprise a fourth monophylogenetic TRUC (things resisting uncompleted classification) together with cellular domains in the universal tree of life. Recently described pandoraviruses have large (1.9-2.5 MB) and highly divergent genomes. In the present study, we updated the classification of pandoraviruses and other reported giant viruses. Phylogenetic trees were constructed based on six informational genes. Hierarchical clustering was performed based on a set of informational genes from Megavirales members and cellular organisms. Homologous sequences were selected from cellular organisms using TimeTree software, comprising comprehensive, and representative sets of members from Bacteria, Archaea, and Eukarya. Phylogenetic analyses based on three conserved core genes clustered pandoraviruses with phycodnaviruses, exhibiting their close relatedness. Additionally, hierarchical clustering analyses based on informational genes grouped pandoraviruses with Megavirales members as a super group distinct from cellular organisms. Thus, the analyses based on core conserved genes revealed that pandoraviruses are new genuine members of the 'Fourth TRUC' club, encompassing distinct life forms compared with cellular organisms.
authors.affiliation: Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes UM63 CNRS 7278, IRD 198, INSERM U1095, Faculté de Médecine, Aix-Marseille University Marseille, France ; I2M UMR 7373, CNRS équipe Evolution Biologique et Modélisation, Aix-Marseille University Marseille, France.
authors.forename: Vikas
authors.initials: V
authors.lastname: Sharma
authors.affiliation: Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes UM63 CNRS 7278, IRD 198, INSERM U1095, Faculté de Médecine, Aix-Marseille University Marseille, France ; Institut Hospitalo-Universitaire Méditerranée Infection, Pôle des Maladies Infectieuses et Tropicales Clinique et Biologique, Fédération de Bactériologie-Hygiène-Virologie, Centre Hospitalo-Universitaire Timone, Assistance Publique-Hôpitaux de Marseille Marseille, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Colson
authors.affiliation: I2M UMR 7373, CNRS équipe Evolution Biologique et Modélisation, Aix-Marseille University Marseille, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Chabrol
authors.affiliation: Medical Parasitology Laboratory, Laboratory Department I (Medicine), Diagnostics, Central Institute of the Bundeswehr Medical Service Koblenz, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Scheid
authors.affiliation: I2M UMR 7373, CNRS équipe Evolution Biologique et Modélisation, Aix-Marseille University Marseille, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Pontarotti
authors.affiliation: Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes UM63 CNRS 7278, IRD 198, INSERM U1095, Faculté de Médecine, Aix-Marseille University Marseille, France ; Institut Hospitalo-Universitaire Méditerranée Infection, Pôle des Maladies Infectieuses et Tropicales Clinique et Biologique, Fédération de Bactériologie-Hygiène-Virologie, Centre Hospitalo-Universitaire Timone, Assistance Publique-Hôpitaux de Marseille Marseille, France.
authors.forename: Didier
authors.initials: D
authors.lastname: Raoult
keywords: Megavirales; Pandoravirus; TRUC; domains of life; giant virus; informational genes; nucleocytoplasmic large DNA viruses; phylogeny