ICTV Virus Taxonomy Profile: Rhabdoviridae

1N, nucleocapsid protein; L, large polymerase protein; P, phosphoprotein; M, matrix protein; G, glycoprotein; RdRP, RNA-dependent RNA polymerase; RNP, ribonucleoprotein.

2Virions are usually enveloped and bullet-shaped or bacilliform (i.e. with two rounded ends) and contain five structural proteins (Table 1, Fig. 1). The nucleocapsid protein (N), the large multi-functional RNA-dependent RNA polymerase (L) and the polymerase-associated phosphoprotein (P) together with the RNA genome form the ribonucleoprotein (RNP) complex. The nucleocapsid is encased in the matrix protein (M) layer which also interacts with the envelope containing the transmembrane glycoprotein (G). Plant rhabdoviruses assigned to the genus Varicosavirus are filamentous and lack an envelope.

3Rhabdovirus negative sense single-stranded RNA genomes range from 10.8 to 16.1 kb. Almost all rhabdovirus genomes are unsegmented but rhabdoviruses with bi-segmented genomes are also known. Terminal non-coding regions are partially complementary. Genomes usually encode five major structural proteins but may also encode additional (accessory) proteins either in additional genes or as alternative ORFs within the structural protein genes (Fig. 2).

4Rhabdovirus replication generally occurs in the cytoplasm following receptor-mediated endocytosis. Primary transcription is initiated from the incomingRNP complex by the RNA-dependent RNA polymerase (RdRP). Stop–start transcription occurs 3′ to 5′ using gene start and gene end sequences, separated by non-transcribed intergenic sequences, to generate capped and polyadenylated mRNAs. Replication is initiated by the RdRP from a single promoter at the 3' end, ignoring gene start and end sequences to generate a (+)RNP. This is the template to generate nascentRNPs which are assembled with M and G into enveloped virions. Budding can occur at either the plasma membrane or internal membranes. Some plant rhabdoviruses replicate in the nucleus.

5The Rhabdoviridae includes 18 genera and one unassigned species (Moussa virus). Viruses assigned to each genus form a monophyletic clade based on phylogenetic analyses of L protein sequences and usually have similar genome organizations, including the number and locations of accessory genes. Rhabdoviruses have been isolated from a wide range of vertebrates and plants; many have been isolated from arthropods. Members of the genus Lyssavirus infect only mammals, including humans in which they can cause fatal encephalitis (rabies). Members of the genera Vesiculovirus, Ephemerovirus, Tibrovirus, Hapavirus, Curiovirus, Sripuvirus and Ledantevirus infect vertebrates (mammals, birds or reptiles) and are transmitted by arthropods. Some arthropod-borne rhabdoviruses are associated with diseases of livestock; some may cause disease in humans. Members of the genus Tupavirus have only been isolated from vertebrates. Members of the genera Novirhabdovirus, Sprivivirus and Perhabdovirus infect only fish, some causing economically important diseases. Rhabdoviruses assigned to the genus Sigmavirus each infect only dipteran flies of a single species and they are transmitted vertically. Members of the genus Almendravirus replicate only in insects. Plant rhabdoviruses are assigned to the genera Cytorhabdovirus, Nucleorhabdovirus, Dichorhavirus and Varicosavirus and are transmitted by either arthropods or chytrid fungi. Many are associated with diseases of agricultural or horticultural importance.

6Full ICTV Online (10th) Report: www.ictv.global/report/rhabdoviridae.