Family: Secoviridae
Genus: Cheravirus
Distinguishing features
Members of the genus Cheravirus have bipartite genomes and encode three capsid proteins and are transmitted by nematodes and through seeds.
Virion
See discussion under family description.
Genome organisation and replication
Cheraviruses have three capsid proteins (CP) of similar sizes (Le Gall et al., 2007). In some cases, these proteins are not fully or reproducibly resolved from each other by electrophoresis. The genome of cheraviruses is bipartite and the genomic organization is similar to that of comoviruses, although a N-terminus coding domain seems to be lacking within the polyprotein encoded by RNA2 (Figure 3.Secoviridae). The RNA2-encoded movement protein of apple latent spherical virus (ALSV) is 42 kDa, suggesting that translation initiation occurs at the second AUG, which is in a better context. Tubular structures containing virus-like particles are observed in infected cells and are likely involved in cell-to-cell movement of the virus. The movement protein and all three CPs are necessary for cell-to-cell movement of the virus (Yoshikawa et al., 2006). The MP binds to VP25, one of the three CPs (Isogai et al., 2006). VP20 of ALSV, another CP, is a suppressor of silencing that interferes with systemic movement of the silencing signal (Yaegashi et al., 2007).
Biology
The host range is broad or narrow, depending on the virus, and includes weed plants found in the vicinity of infected crops. Symptoms are usually mild or absent. Cherry rasp leaf virus is transmitted by nematodes (Xiphinema americanum) in the field (Nyland et al., 1969), and is readily seed-transmitted (Hansen et al., 1974). ALSV is also seed-transmitted through both embryo and pollen in apple (Nakamura et al., 2011). In potato, Arracacha virus B is transmitted through true seed and pollen (Jones 1982). Currant latent virus has been detected in oligophagous viviparous females and in nymphs of red blister aphid Cryptomyzus ribis and circulates in the aphid (Petrzik et al., 2015).
Species demarcation criteria
See discussion under family description.