Induction of viral resistance in plants by dsRNA interference

Double-stranded RNA (dsRNA) has been shown to promote interference of gene expression of endogenous genes that contain homologous sequences. This interference is referred to as post-transcriptional gene silencing or PTGS. PTGS appears to be a nucleotide sequence specific defense mechanism that can target both endogenous and exogenous messenger RNA (mRNA). PTGS employs a yet unexplained RNA degradation mechanism.

In this research, in vitro synthesized dsRNA homologous to two different segments of the genome of the bean common mosaic necrosis virus (BCMNV) was applied to bean plants to determine if the dsRNA affected the susceptibility of the plant to BCMNV infection. The results indicated that the application of dsRNA reduced the number of local lesions per leaf and reduced plant death by approximately 20%. Using dsRNA that expressed homology to different regions of BCMNV did not result in any difference in the ability of dsRNA to inhibit viral replication. Within the parameters of concentration of dsRNA used, no difference in the effectiveness of viral inhibition of the dsRNA was observed. A relationship was observed between the time interval between the application of dsRNA and viral local lesions. The greater reduction of local lesions was observed on leaves that had the greater time interval between the application of the dsRNA and viral inoculation. Systemic viral resistance was observed when the primary leaf was treated with dsRNA and trifoliate leaf was inoculated with the virus. No viral resistance was observed in plants that developed from seeds produced by dsRNA treated plants that survived viral inoculation.