title: Picornavirales, a proposed order of positive-sense single-stranded RNA viruses with a pseudo-T = 3 virion architecture.
abstract: Despite the apparent natural grouping of "picorna-like" viruses, the taxonomical significance of this putative "supergroup" was never addressed adequately. We recently proposed to the ICTV that an order should be created and named Picornavirales, to include viruses infecting eukaryotes that share similar properties: (i) a positive-sense RNA genome, usually with a 5'-bound VPg and 3'-polyadenylated, (ii) genome translation into autoproteolytically processed polyprotein(s), (iii) capsid proteins organized in a module containing three related jelly-roll domains which form small icosahedral, non-enveloped particles with a pseudo-T = 3 symmetry, and (iv) a three-domain module containing a superfamily III helicase, a (cysteine) proteinase with a chymotrypsin-like fold and an RNA-dependent RNA polymerase. According to the above criteria, the order Picornavirales includes the families Picornaviridae, Comoviridae, Dicistroviridae, Marnaviridae, Sequiviridae and the unassigned genera Cheravirus, Iflavirus and Sadwavirus. Other taxa of "picorna-like" viruses, e.g. Potyviridae, Caliciviridae, Hypoviridae, do not conform to several of the above criteria and are more remotely related: therefore they are not being proposed as members of the new order. Newly described viruses, not yet assigned to an existing taxon by ICTV, may belong to the proposed order.
authors.affiliation: UMR GDPP INRA University Victor Segalen Bordeaux 2, INRA, BP 81, 33883, Villenave d'Ornon Cedex, France. olegall@bordeaux.inra.fr
authors.forename: Olivier
authors.initials: O
authors.lastname: Le Gall
authors.forename: Peter
authors.initials: P
authors.lastname: Christian
authors.forename: Claude M
authors.initials: CM
authors.lastname: Fauquet
authors.forename: Andrew M Q
authors.initials: AM
authors.lastname: King
authors.forename: Nick J
authors.initials: NJ
authors.lastname: Knowles
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Nakashima
authors.forename: Glyn
authors.initials: G
authors.lastname: Stanway
authors.forename: Alexander E
authors.initials: AE
authors.lastname: Gorbalenya
mesh_terms: D036022:Capsid Proteins / Q000737:chemistry; D003546:Cysteine Endopeptidases; D016679:Genome, Viral / Q000235:genetics; D010849:Picornaviridae / Q000145:classification / Q000235:genetics; D020815:Polyproteins / Q000737:chemistry; D012328:RNA Viruses / Q000737:chemistry / Q000145:classification* / Q000235:genetics / Q000648:ultrastructure; D012367:RNA, Viral / Q000737:chemistry / Q000648:ultrastructure; D012324:RNA-Dependent RNA Polymerase; D014771:Virion / Q000737:chemistry / Q000648:ultrastructure; D014773:Virology / Q000379:methods
chemical_list: D036022:Capsid Proteins; D020815:Polyproteins; D012367:RNA, Viral; D012324:RNA-Dependent RNA Polymerase; D003546:Cysteine Endopeptidases