Cheravirus and Sadwavirus: two unassigned genera of plant positive-sense single-stranded RNA viruses formerly considered atypical members of the genus Nepovirus (family Comoviridae)

Abstract

The genus Nepovirus (family Comoviridae) was known both for a good level of homogeneity and for the presence of atypical members. In particular, the atypical members of the genus differed by the number of capsid protein (CP) subunits. While typical nepoviruses have a single CP subunit with three structural domains, atypical nepoviruses have either three small CP subunits, probably corresponding to the three individual domains, or a large and a small subunit, probably containing two and one structural domains, respectively. These differences are corroborated by hierarchical clustering based on sequences derived from both genomic RNAs. Therefore, these atypical viruses are now classified in two distinct genera, Cheravirus (three CP subunits; type species Cherry rasp leaf virus) and Sadwavirus (two CP subunits; type species Satsuma dwarf virus).