Genus - Benyvirus

Abstract

This chapter focuses on Benyvirus genus whose viral particles consist of four to five nonenveloped, helically constructed rod-shaped structures, with an axial canal. They have predominant lengths of about 390, 265, 100, 85 and 80 to 65 nm and a constant diameter of 20 nm. The right-handed helix with a pitch of 2.6 nm has an axial repeat of four turns, involving 49 CP subunits, each occupying four nucleotides. Their coat proteins constitute about 95% of the particle weight. The viral particles are sometimes unstable in sap with strong infectivity losses within one to five days at room temperature. In naturally infected plants, the viruses contain four to five linear positive sense ssRNAs of about 6.7, 4.6, 1.8, 1.4, and 1.3 kb, respectively. The minor capsid protein contains a KTER motif in its C terminal part that is necessary for the transmission of the virions by Polymyxa betae. The RNA-1 contains one large ORF coding for a replication-associated protein that is cleaved post-translationally. This proteolytic cleavage of the replicase distinguishes the benyviruses from all other viruses with rod-shaped particles, which have their replication-associated proteins encoded on two ORFs. The benyviruses are distinguished by coat protein sequence less than 90% identical, distant serological relations, and distinct host ranges. They are morphologically similar to other rod-shaped viruses that are classified in the family Virgaviridae. The Mtr, Hel and RdRp motifs in the replication-associated proteins show a higher degree of similarity to those of the viruses of the family Togaviridae (rubella virus) and of hepatitis virus E than to those of other rod-shaped plant viruses.