Cucumovirus Satellite RNAs Cannot Replicate Autonomously in Cowpea Protoplasts

Abstract

SUMMARYPurified preparations of peanut stunt virus-associated RNA 5 (PARNA 5) and cucumber mosaic virus-associated RNA 5 (CARNA 5) were used to inoculate cowpea protoplasts, alone or together with their respective helper viruses. After incubation of the protoplasts for up to 5 days, total nucleic acid was extracted, denatured, electrophoresed, transferred to nitrocellulose membranes and hybridized to cDNA probes specific for satellite and viral RNA. Satellite replication could be detected only in protoplasts infected with mixtures of satellite and viral RNA, not in those inoculated with satellite RNA alone. These results suggest that the dependence of cucumovirus satellite RNAs on their helpers is on the replication function rather than on the spreading and/or encapsidation functions of the helper virus.

Anti-sense regions in satellite RNA of cucumber mosaic virus form stable complexes with the viral coat protein gene

“…It appears that in the CMV plus satellite RNA system specific mechanisms have evolved for the replication and regulation of RNA components. The satellite RNA cannot replicate in the absence of CMV genomic RNAs in whole plants or isolated protoplasts (23), it shows a varying degree of specificity to various strains (24), it specifically reduces the level of RNA 1 and 2 synthesis (24), it has a small "anti-sense" sequence to a conserved region of RNA 1 and 2 (1), it forms a similar hairpin structure at the 5'-end as the structure in RNA 1 and 2 (1), it has a partial 3'-terminal homology to CMV genomal RNAs (7) and, finally, it specifically binds to the coat protein gene (Fig. 4B).…”