Family: Rhabdoviridae

Genus: Betapaprhavirus

Distinguishing features

Viruses assigned to the genus Betapaprhavirus form a distinct monophyletic group based on well-supported Maximum Likelihood or Maximum Clade Credibility trees inferred from complete L sequences. Members of the genus have been detected in moths and butterflies (Lepidoptera). They are distant phylogenetically from viruses assigned to the genus Alphapaprhavirus.

Virion

Morphology

Bullet-shaped particles (approximately 80 nm × 180 nm) have been observed in insect cells infected with Spodoptera frugiperda rhabdovirus (SfRV; species Betapaprhavirus frugiperda) (Ma et al., 2014). Other particles of different morphology observed in the cells may be artifactual.

Nucleic acid

Betapaprhavirus genomes consist of a single molecule of negative-sense, single-stranded RNA of approximately 13.3–13.5 kb (Ma et al., 2014, Käfer et al., 2019).

Proteins

Betapaprhavirus N, P, M, G and L proteins share sequence homology and/or structural characteristics with the cognate proteins of other rhabdoviruses. Betapaprhavirus G proteins are class I transmembrane glycoproteins. Alignment with the G protein of vesicular stomatitis Indiana virus (species Vesiculovirus indiana) indicates likely conservation of only 6 of the 12 conserved cysteine residues that are typical of animal rhabdovirus G proteins (Walker and Kongsuwan 1999, Roche et al., 2006).

Genome organisation and replication

Betapaprhavirus genomes include the five genes (N, P, M, G and L) encoding the structural proteins (Figure 1.Betapaprhavirus). They also have an additional gene (U1) between the G and L genes encoding a small basic protein.

Figure 1.Betapaprhavirus. Schematic representation of betapaprhavirus genomes shown in reverse (positive-sense) polarity. The five long open reading frames (ORFs) in the N, P, M, G and L genes are shown (open arrows). In each virus, the U1 gene (green) between the G gene and L gene encodes a small basic protein.

Biology

SfRV was detected initially in the Sf9 cell line derived from the fall armyworm moth (Spodoptera frugiperda) and then in the corresponding parental cell line (Sf21) (Ma et al., 2014). Wild populations of this moth in the eastern United States and Caribbean have been shown to be infected with genetically diverse strains of the virus which is also capable of infecting cells of other moths (Spodoptera exigua, Heliothis subflexa, Bombyx mori) (Schroeder et al., 2019). Lepidopteran rhabdo-related virus 34 (species Betapaprhavirus sylvina) was detected in orange moths (Triodia sylvina) collected in Germany, in 2011 (Käfer et al., 2019).

Species demarcation criteria

Viruses assigned to different species within the genus have several of the following characteristics: A) minimum amino acid sequence divergence of 10% in N proteins; B) minimum amino acid sequence divergence of 10% in the L proteins; C) minimum amino acid sequence divergence of 15% in G proteins; D) significant differences in genome organisation 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 invertebrate hosts.

Related, unclassified viruses

Virus names and virus abbreviations are not official ICTV designations.

* Coding region sequence incomplete, transcriptome shotgun assembly