Synthesis in vitro of infectious RNA copies of the virulent satellite of turnip crinkle virus.

RNA copies, synthesized in vitro, of the virulent satellite (RNA C) of turnip crinkle virus (TCV) infect plants when coinoculated with helper virus RNA. RNA C is a small linear RNA of about 355 bases which intensifies TCV symptoms in infected plants. Full-length cDNA copies of the satellite were inserted in an expression vector (for RNA synthesis in vitro) in such a way that RNA synthesized in vitro had the same 5'-end as the native satellite. Plus-strand RNA copies of the satellite in near-monomer and multimer form infected plants, while minus-strand RNA copies and DNA copies of the satellite RNA did not do so under the conditions tested. When plants were inoculated with RNAs synthesized in vitro from two independently cloned satellite cDNAs with base sequence and length differences, the products of infection corresponded in sequence to the different cRNAs used in the inocula. Satellite RNAs synthesized in vitro from either cDNA produced the same symptoms as the native satellite RNA.