REPLICATION OF IN-VITRO TOBRAVIRUS RECOMBINANTS SHOWS THAT THE SPECIFICITY OF TEMPLATE RECOGNITION IS DETERMINED BY 5'-NONCODING BUT NOT 3'-NONCODING SEQUENCES

Natural recombinant tobacco rattle tobravirus (TRV) isolates contain s equences from a different tobravirus, pea early browning virus (PEBV), To characterize the sequence requirements for viable recombinant form ation hybrid cDNA clones of RNA2 of PEBV and TRV were assembled. Inclu sion of 320 nt from the 5' terminus of PEBV or 335 nt from the 5' term inus of TRV in the hybrid RNAs was sufficient to permit their replicat ion by, respectively, PEBV RNA1 or TRV RNA1 regardless of the origin o f the 3' terminal region. However, PEBV RNA1 but not TRV RNA1 was some times able to support low level replication of RNA2 containing the het erologous 5' terminal region, In vitro translation of PEBV transcripts containing 5' noncoding region deletions supported the hypothesis tha t in vivo the PEBV coat protein (CP) is expressed from a subgenomic RN A and that, therefore, in the recombinants the CP subgenomic promoter probably is recognized by the replicase of the heterologous virus.