@article{mbs:/content/journal/jgv/10.1099/0022-1317-72-10-2367, author = "Marsh, Loren E. and Pogue, Gregory P. and Szybiak, Urzula and Connell, James P. and Hall, Timothy C.", title = "Non-replicating deletion mutants of brome mosaic virus RNA-2 interfere with viral replication", journal= "Journal of General Virology", year = "1991", volume = "72", number = "10", pages = "2367-2374", doi = "https://doi.org/10.1099/0022-1317-72-10-2367", url = "https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-72-10-2367", publisher = "Microbiology Society", issn = "1465-2099", type = "Journal Article", abstract = "Naturally occurring defective interfering RNAs (DI-RNAs) and satellite RNAs greatly reduce the accumulation of their helper virus in vivo, but often modulate symptom expression in an unpredictable manner. Deletion mutants Nc/S, Na/M and Sa/Nc + M/S, derived from brome mosaic virus (BMV) RNA-2, failed to replicate when co-inoculated with BMV RNAs-1 and -2 to barley protoplasts. However, the inoculum RNA corresponding to these deletion mutants was extremely stable and could have been mistaken for plus-strand progeny had minus-strand progeny analysis been omitted. These results accentuate the need for such tests in evaluating the ability of mutant viral sequences to replicate. One of the mutants, Nc/S, effectively interfered with the accumulation of BMV RNAs-1 and -2 in barley protoplasts. This non-replicating interfering RNA was termed NRI RNA-2 Nc/S. When present with RNAs-1 and -2 at low inoculum amounts (1 µg), NRI RNA-2 Nc/S reduced replication of RNA-2, the parental RNA, by 63% and preferentially interfered with minus-strand RNA accumulation. At higher levels (4 µg), it completely displaced replication of both RNAs-1 and -2. Mutations eliminating translation of a truncated p2a protein from NRI RNA-2 Nc/S did not alleviate the interference effect, demonstrating that a defective replicase protein was not responsible for the decreased accumulation of genomic RNA. At an NRI RNA:genomic RNA inoculum molar ratio of 1:1, NRI RNA-2 Nc/S reduced the accumulation of all helper virus RNAs by 55%. Since this reduction was seen for both wild-type RNA-3 and ASGP RNA-3, a deletion mutant of RNA-3 that lacks the subgenomic promoter necessary for coat protein expression, it was evident that the effective interference mediated by NRI RNA-2 Nc/S was not mitigated by encapsidation. The ability of the NRI RNAs to mimic satellite DI RNAs in depressing helper virus replication suggests that their expression in transgenic plants may provide a new and widely applicable approach for inducing resistance to viral infection.", }