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Ralf G. Dietzgen, Dàohóng Jiāng, Jens H. Kuhn and Nikos Vasilakis
A summary of this ICTV Report chapter has been published as an ICTV Virus Taxonomy Profile article in the Journal of General Virology, and should be cited when referencing this online chapter as follows:
Ralf G. Dietzgen, Dàohóng Jiāng, Jens H. Kuhn, Nikos Vasilakis, and ICTV Report Consortium. 2019, ICTV Virus Taxonomy Profile: Artoviridae, Journal of General Virology, 100, 1202–1203.
The family Artoviridae was created in 2018 for the established monospecific genus Peropuvirus (moved from Nyamiviridae (Dietzgen et al., 2017)) and six new species for invertebrate viruses all discovered by high throughput sequencing (Li et al., 2015, Shi et al., 2016). Artoviruses form a family in the haploviricotine order Mononegavirales (Amarasinghe et al., 2019).
Table 1.Artoviridae. Characteristics of members of the family Artoviridae.
Pteromalus puparum negative-strand RNA virus 1 (KX431032), species Pteromalus puparum peropuvirus, genus Peropuvirus
Enveloped, spherical particles,100–130 nm in diameter
Negative-sense, unsegmented RNA of about 12 kb
Nuclear: the RNA-directed RNA polymerase engages with the ribonucleoprotein complex at the genome 3′-end
Individual, putatively polyadenylated, mRNAs are translated in the cytoplasm
Barnacles, copepods, odonates, parasitoid wasps, pillworms, woodlice
Realm Riboviria, phylum Negarnaviricota, subphylum Haploviricotina, class Monjiviricetes, order Mononegavirales. The single genus Peropuvirus includes 7 species
Virions of Pteromalus puparum negative-strand RNA virus 1 (PpNSRV-1) are enveloped and spherical with a diameter of 100–130 nm (Figure 1.Artoviridae). Virion information is not available for other artoviruses, which are only known from genomic sequence data.
Figure 1.Artoviridae. Electron micrographs of purified PpNSRV-1 particles from follicular cells. (A) Electron micrographs of purified PpNSRV-1 virions. (B) and (C) are the magnification pictures. Red arrows indicate viral particles. From 28278298, figure S3.
Spherically shaped PpNSRV-1 particles are present in follicular cells of the ovaries of infected parasitoid wasps (Figure 1.Artoviridae). Similarly, virion-like particles stacked in intracellular vesicles have been observed in cells of the digestive tract. The spherical particles of PpNSRV-1 are similar to particles produced by nyamiviruses (Dietzgen et al., 2017, Wang et al., 2017).
Unsegmented, single-stranded RNA genome of 11–12 kb.
Artoviruses encode up to 5 structural proteins. Among them are the nucleocapsid protein (N), glycoprotein (G) and RNA-directed RNA polymerase (RdRP) domain-containing large protein (L) that are identified based on sequence similarity and structural properties shared with mononegavirus homologues. Functions of the other encoded proteins are largely unknown but may be those of matrix and polymerase cofactor proteins.
The amino acid sequence of the PpNSRV-1 L protein is 26% identical to that of Midway virus (MIDWV, Nyamiviridae). The PpNSRV-1 ORF IV protein contains 7 potential O-linked and 4 potential N-linked glycosylation sites and 29 potential phosphorylation sites, suggesting that ORF IV may encode the viral glycoprotein G. The U1 protein is predicted to have 37 potential phosphorylation sites, whereas the U2 protein has 9 potential phosphorylation sites. The U3 protein contains 37 potential O-linked glycosylation sites. Thus, U3 may encode a glycosylated matrix protein M and U1 may encode the viral nucleoprotein N. Based on the conserved genomic organization of mononegaviruses, U2 is suggested to encode a phosphoprotein (P) (Wang et al., 2017).
Artovirus single-stranded RNA genomes are up to 12 kb (Figure 2.Artoviridae). All known artoviruses have unsegmented genomes. The number of open reading frames (ORFs) varies. Genomes usually encode hypothetical proteins of unknown function (U1, U2 and U3), a putative glycoprotein (G) protein and a large protein (L) encoding a RNA-directed RNA polymerase domain: in the gene order 3'-U1-U2-U3-(G)-L-5'. The complete L gene sequences for all known members are known. Knowledge of artovirus replication is limited.
The PpNSRV-1 genome contains five large, independently-transcribed, non-overlapping ORFs flanked by 3′-leader and 5′-trailer regions whose terminal nucleotides do not exhibit obvious complementarity. Typical conserved transcription initiation and termination motifs are identified upstream and downstream, respectively, of each putative ORF.
Figure 2.Artoviridae. Artovirus genome organization. Some virus genome sequences may be incomplete.
Members of the genus Peropuvirus infect parasitoid wasps, barnacles, pillworms, woodlice odonates, or copepods.
PpNSRV-1 was originally isolated from a laboratory parasitoid strain of a pteromalid wasp (Pteromalus puparum Linnaeus, 1758). PpNSRV-1 is present in various tissues and life stages of the parasitoid and is transmitted vertically through females and males. PpNSRV-1 increases adult longevity and impairs several fitness parameters of the wasp but has no influence on successful parasitism. PpNSRV1 moderates the offspring sex ratio by decreasing female offspring numbers (Wang et al., 2017).
Arto: from arthropod
Peropu: from Pteromalus puparum, the species to which the pteromalid wasp belongs, from which the family’s typical member, PpNSRV-1, was first isolated.
Phylogenetic relationships between the RdRP amino acid sequences of artoviruses and members of related mononegavirus families are shown in Figure 3.Artoviridae.
Figure 3.Artoviridae. Phylogenetic maximum likelihood tree of members of the family Artoviridae classified in the single genus Peropuvirus (formerly Nyamiviridae) and the unclassified Lepeophtheirus salmonis negative-stranded RNA virus 1 from copepods based on RdRP domain amino acid sequences. Representative members of related mononegavirus families are included for comparison. The ML tree was produced using an LG + G + I model in Mega7 (Kumar et al., 2016). This phylogenetic tree and corresponding sequence alignment are available to download from the Resources page.
Members of the family Artoviridae are phylogenetically related to members of the families Bornaviridae, Lispiviridae, Mymonaviridae, and Nyamiviridae (Figure 3.Artoviridae).
Since only one genus (Peropuvirus) is currently recognized in the family Artoviridae, the family description above corresponds to the genus description. For clarity, the additional information that can be found on the genus page is also presented below.
No species demarcation criteria have been established beyond virus phylogeny and hosts. Members of different Peropuvirus species differ by about 52–75% in L amino acid sequence, although sequence divergence is not currently used as a formal species demarcation criterion.
Exemplar isolate of the speciesSpeciesVirus nameIsolateAccession numberRefSeq numberAvailable sequenceVirus Abbrev.Barnacle peropuvirusBěihǎi barnacle virus 8BHTH14652KX884410NC_032430Complete coding genomeBhBV-8Beihai peropuvirusBěihǎi rhabdo-like virus 1BHTSS15727KX884412NC_032555Complete coding genomeBhRLV-1Hubei peropuvirusHúběi rhabdo-like virus 6QTM24798KX884421partial genomeHbRLV-6Odonate peropuvirusHúběi rhabdo-like virus 8QTM19395KX884420partial genomeHbRLV-8Pillworm peropuvirusHúběi rhabdo-like virus 5WHSFII19440KX884446partial genomeHbRLV-5Pteromalus puparum peropuvirusPteromalus puparum negative-strand RNA virus 11KX431032NC_038269Complete genomePpNSRV-1Woodlouse peropuvirusBěihǎi rhabdo-like virus 2BHTSS7258KX884413NC_032558Complete coding genomeBhRLV-2
Lepeophtheirus salmonis negative-stranded RNA virus 1
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