Recognition of cis-acting sequences in RNA 3 of Prunus necrotic ringspot virus by the replicase of Alfalfa mosaic virus

Alfalfa mosaic virus (AMV) and Prunus necrotic ringspot virus (PNRSV) belon g to the genera Alfamovirus and Ilarvirus, respectively, of the family Brom oviridae. Initiation of infection by AMV and PNRSV requires binding of a fe w molecules of coat protein (CP) to the 3' termini of the inoculum RNAs and the CPs of the two viruses are interchangeable in this early step of the r eplication cycle. Cis-acting sequences in PNRSV RNA 3 that are recognized b y the AMV replicase were studied in in vitro replicase assays and by inocul ation of AMV-PNRSV RNA 3 chimeras to tobacco plants and protoplasts transfo rmed with the AMV replicase genes (P12 plants). The results showed that the AMV replicase recognized the promoter for minus-strand RNA synthesis in PN RSV RNA 3 but not the promoter for plus-strand RNA synthesis. A chimeric RN A with PNRSV movement protein and CP genes accumulated in tobacco, which is a non-host for PNRSV.