Detection and assignment of proteins encoded by rice black streaked dwarf fijivirus S7, S8, S9 and S10

The proteins encoded by rice black streaked dwarf fijivirus (RBSDV) genomic segments 7-10 (S7-S10) were characterized. Open reading frames (ORFs) from these segments were expressed as fusion proteins in Escherichia coli. Antibodies raised against the expressed products were used as probes to determine whether the viral ORFs encode structural proteins. In Western blots, antibodies to the expressed S8 and S10 products reacted with a core capsid (65 kDa) and a major outer capsid (56 kDa) protein, respectively, while none of the antibodies to S7 and S9 products reacted with structural proteins. Antisera to RBSDV S7 ORF1 and S9 ORF1 each detected a single protein of the predicted size in total protein extracts from infected rice plants and viruliferous Laodelphax striatellus. Immunoelectron microscopy revealed that antibodies to RBSDV S7 ORF1 and RBSDV S9 ORF1 reacted with tubular structures and viroplasm, respectively, in sections of both infected maize plants and viruliferous L. striatellus. Antisera to ORF2 of S7 and S9 failed to detect any proteins in the infected tissue using either Western blotting or immune-electron microscopic techniques.