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Viruses assigned to the genus Alphanemrhavirus form a distinct monophyletic group based on well-supported Maximum Likelihood trees inferred from complete L sequences. Viruses assigned to the genus have been detected in parasitic nematodes (roundworms of the phylum Nematoda).
Viruses assigned to the genus have not yet been isolated or visualized by electron microscopy.
Alphanemrhavirus genomes consist of a single molecule of negative-sense, single-stranded RNA and range from approximately 11.5–11.7 kb (Shi et al., 2016).
Alphanemrhavirus N, P, M, G and L proteins share sequence homology and/or structural characteristics with the cognate proteins of other rhabdoviruses. In Xinzhou nematode virus 4 (XzNV-4), ORF Mx overlaps the M ORF and encodes a putative 67 amino acid (7.6 kDa) protein of unknown function. This putative protein has not yet been identified in infected cells and it is not known if it is expressed.
Alphanemrhavirus genomes include five genes (N, P, M, G and L) encoding the structural proteins and concise intergenic regions. In XzNV-4, an additional ORF (Mx) overlaps the end of the M ORF within the M gene.
Figure 1.Alphanemrhavirus. Schematic representation of alphanemrhavirus genome organisations. N, P, M, G and L represent ORFs encoding the structural proteins. XzRV-4 ORF Mx, overlapping the end of the M ORF, is highlighted (purple).
Alphanemrhaviruses have been detected only by high-throughput sequencing of pooled mixtures of parasitic nematodes (roundworms) (Shi et al., 2016). Xinshan nematode virus 4 (XsNV-4) was detected in a pool of spirurian nematodes (subclass Spiruria) that includes important mammalian parasites. XzNV-4 was detected in a pool of snake-associated nematode parasites (Shi et al., 2016). Each was detected in China.
Viruses assigned to different species within the genus Alphanemrhavirus have several of the following characteristics: A) minimum amino acid sequence divergence of 10% in N proteins; B) minimum sequence divergence of 10% in the L proteins; C) minimum amino acid sequence divergence of 15% in G proteins; D) significant differences in genome organization as evidenced by numbers and locations of ORFs; E) can be distinguished in virus neutralisation tests; and F) occupy different ecological niches as evidenced by differences in vertebrate hosts and or arthropod vectors. Each member of the genus meets demarcation criteria A, B, C, D and F.
Alphanemrhavirus is derived from the alpha group of nematode rhabdoviruses.
Xinzhou dimarhabdovirus 1*
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