Triatovirus: A new genus in the family Dicistroviridae

ECHEVERRÍA M. G; METZ, G.E; SUSEVICH, M. L; BALSALOBRE, A; MARTI G. A

ARCHIVES OF VIROLOGY

SPRINGER WIEN

Lugar: Viena; Año: 2016 vol. . p. 1 - 7

0304-8608

Triatoma virus (TrV)differs substantially in surface features fromCricket paralysis virus (CrPV),in the absence of an ordered VP4 molecule in thecapsid interior and in thepresence in VP3 of a structurally conserved catalyticmotif involving the sameDDF sequence as in VP1.The twomain differences betweenthe TrV and CrPV capsids are the projections at theTrV surface, which areabsent in CrPV. These projections are made from aninserted sequence element, andthe presence of the same insertion in othermembers of the proposed genus (Plautiastaliintestine virus ?PSIV-,, Himetobi P virus ?HiPV-, and Black queen cellvirus-BQCV-) suggest that they are also likely to have the same structuralfeatures (Agirreet al., 2011, Squirreset al., 2013). The structure suggests that theexposed residues in theseprojections are likely to play a role in theinteractions with the host; forinstance, an entry receptor. Theseconddifference is the presence of a DDF motif in the homologous location inVP3,where it is also exposed to the capsid interior, whereas in CrPV, Aphidlethalparalysis virus ?ALPV-, Drosophila C virus  -DCV-  andRhopalosiphum padi virus ?RhPV-, thismotif is only found in VP1, where it isbelieved to account for cleavage of theVP0 precursor. This difference mayaccount for additional proteolysis in VP1during RNA release. Intriguingly, asecond DDFmotif (3254?3256) is present in VP3 at the same location in thestructure atthe corner between the BIDG sheet and the βx1βx2sheet,which is equivalent to the βx3βx4 sheet in VP1.Thismotif is also conserved in BQCV, HiPV, PSIV and TrVbutis not found in CrPV or in DCV, APLV or RhPV, which is the closestneighbour toCrPV in the current Dicistroviridae phylogenetic tree. Finally, themoststriking difference is the absence of ordered VP4. The fact that thisproteinis not part of the ordered capsid in fully infectious TrV virions is insharpcontrast to what occurs with the same protein in CrPV, where it is foundto bewell structured around the fivefold axis. Such differences precludeassignmentof a general function to VP4 in the Dicistroviridae family, and thisalsoremains to be further elucidated (Squireset al, 2013). Sequencealignment. Taking into account that in thephylogenetic tree of thedicistrovirus family TrV belongs to a different branchfrom that of ABPV andCrPV (Bonning and Miller, 2010), aswell as the biological, genetic, andstructural knowledge regarding this virus,it is reasonable to propose TrV asthe reference for a third Dicistroviridaefamily genus named Triatovirus (Agirre et al., 2011). Phylogeneticanalysis of deduced amino-acidsequences of the three major coat proteins (ORF2) from thefollowing dicistroviruses were done. The criterion employed for theselectionof the viruses was based on the availability of seqeuences in GenBank.Thealignment was performed using the Clustal2 phylogeny. Homalodiscacoagulatavirus (HocV-1) do not have any DDF motif, but in the phylogenetic treeisnearest the Triatovirus genus proposed.