THE GENOME ORGANIZATION OF THE BROAD BEAN NECROSIS VIRUS (BBNV)

The genome of the broad bean necrosis virus Oita-isolate (BBNV-O) [RNA 1 (6.0 kb), RNA2 (2.8 kb) and RNA3 (2.4 kb)] was cloned and sequenced. Computer analysis indicates that methyltransferase, helicase and RNA- dependent RNA polymerase (RdRp) motifs are present in RNA1. The viral capsid protein (CP) cistron is located at the 5' terminal end of RNA2 and the Mr of CP (20 K) is close to that determined by SDS-PAGE analys is. An ochre codon (UAA) in the CP cistron is thought to be partially suppressed to produce a large readthrough protein. RNA3 possesses typi cal motifs of triple gene block proteins, which are also reported in s everal other plant viruses. The furovirus genome organization and phyl ogenetic analysis using RdRp and CP amino acid sequences suggest that BBNV is closely related to potato mop-top virus (PMTV), but is relativ ely distantly related to other furoviruses. The data also suggest that the genus Furovirus should be separated into several genera: the prot otypical genus Furovirus, which excludes the following viruses: the PM TV group including BBNV; the beet necrotic yellow vein virus (BNYVV) g roup; and the peanut clump virus (PCV) group.