“Megavirales”, a proposed new order for eukaryotic nucleocytoplasmic large DNA viruses
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The nucleocytoplasmic large DNA viruses (NCLDVs) comprise a monophyletic group of viruses that infect animals and diverse unicellular eukaryotes. The NCLDV group includes the families Poxviridae, Asfarviridae, Iridoviridae, Ascoviridae, Phycodnaviridae, Mimiviridae and the proposed family “Marseilleviridae”. The family Mimiviridae includes the largest known viruses, with genomes in excess of one megabase, whereas the genome size in the other NCLDV families varies from 100 to 400 kilobase pairs. Most of the NCLDVs replicate in the cytoplasm of infected cells, within so-called virus factories. The NCLDVs share a common ancient origin, as demonstrated by evolutionary reconstructions that trace approximately 50 genes encoding key proteins involved in viral replication and virion formation to the last common ancestor of all these viruses. Taken together, these characteristics lead us to propose assigning an official taxonomic rank to the NCLDVs as the order “Megavirales”, in reference to the large size of the virions and genomes of these viruses.
KeywordsMajor Capsid Protein Giant Virus Virion Morphogenesis Ancestral Virus Jelly Roll
Natalya Yutin and Eugene V. Koonin are supported by intramural funds of the US Department of Health and Human Services (to the National Library of Medicine). James Van Etten is partially supported by NIH Grant P20 RR15635 from the COBRE Program of the National Center for Research Resources.
Conflict of interest
There are no potential conflicts of interest or financial disclosures for any of the authors.
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