RNA DUPLEX UNWINDING ACTIVITY OF ALFALFA MOSAIC-VIRUS RNA-DEPENDENT RNA-POLYMERASE

An RNA-dependent RNA polymerase (RdRp) purified from alfalfa mosaic vi rus-infected tobacco is capable of synthesizing in vitro full-size RNA s of minus and plus polarities. However, the enzyme is not able to per form a complete replication cycle in vitro. The products were found to be completely base-paired to their templates. The enzyme was able to use double-stranded RNA as a template for RNA synthesis if it could in itiate from a single-stranded promoter, The inability (of most) of our enzyme preparations to create a single-stranded initiation site could explain why they could not perform a complete replication cycle in vi tro, This is the first report on duplex RNA unwinding activities by a plant viral RdRp.