Abstract

Northern blot analysis with cDNA probes to RNA-3 (1 kb) of RBDV revealed extensive sequence homology with RBDV RNA-2 (2.2 kb). Nucleotide sequencing showed that RNA-2 contains 2 large open reading frames (ORFs), of 1074 (5′ ORF) and 822 (3′ ORF) bases. The 3′ ORF is virtually identical in sequence to RNA-3, which encodes the M_r 30 509 (30 kDa) coat protein. The 5′ ORF encodes an M_r 38 860 (39 kDa) protein which slightly resembles the 32 kDa protein encoded by RNA-3 of alfalfa mosaic virus (AlMV). RBDV RNA-2 resembles AlMV RNA-3 in being bicistronic and encoding a coat protein at the 3′ end. Comparing RNA-1 and RNA-2 of RBDV, only the 18 3′-terminal nucleotides are identical in sequence but the 3′-terminal 71 nucleotides of each RNA species have the potential to form similar stem-loop structures.