Abstract
Northern hybridization analyses using an RNA probe corresponding to the 3'-terminal region of apple stem grooving virus (ASGV) genome indicated that all dsRNA preparations from tissues infected with 10 ASGV isolates contained three virus-specific dsRNAs (6.5, 2.0 and 1.0 kbp). Using additional RNA probes corresponding to different parts of the genome, a dsRNA preparation from ASGV (isolate P-209)-infected tissues was found to contain five virus-specific dsRNAs of 6.5 kbp (G-ds), 5.5 kbp (ds1), 4.5 kbp (ds2), 2.0 kbp (SG-ds1) and 1.0 kbp (SG-ds2). G-ds was probably the replicative form of the ASGV-genome. Ds1 and ds2 were thought to be 5'-coterminal with the ASGV genome. In contrast, SG-ds1 and SG-ds2 were thought to be 3'-coterminal with the genome. Both the positions of these RNAs relative to the genome and their sizes suggest that SG-ds1 and SG-ds2 are ds forms of subgenomic RNAs for the ORF2-encoded protein and the coat protein (CP), respectively. The C-terminal regions of the ORF1-encoded protein including the CP were expressed in Escherichia coli. The size of the expressed protein, which starts with methionine (Met) at amino acid position 1869 agreed with that of ASGV-CP, suggesting this Met is the starting amino acid of the CP.
