Double-stranded RNA-mediated interference with plant virus infection

Double-stranded RNA (dsRNA) has been shown to play a key role as an inducer of different interference phenomena occurring in both the plant and animal kingdoms. Here, we show that dsRNA derived from viral sequences can interf ere with virus infection in a sequence-specific manner by directly deliveri ng dsRNA to leaf cells either by mechanical inoculation or via an Agrobacte rium-mediated transient-expression assay. We have successfully interfered w ith the infection of plants by three viruses belonging to the tobamovirus, potyvirus, and alfamovirus groups, demonstrating the reliability of the app roach. We suggest that the effect mediated by dsRNA in plant virus infectio n resembles the analogous phenomenon of RNA interference observed in animal s. The interference observed is sequence specific, is dose dependent, and i s triggered by dsRNA but not single-stranded RNA. Our results support the v iew that a dsRNA intermediate in virus replication acts as efficient initia tor of posttranscriptional gene silencing (PTGS) in natural virus infection s, triggering the initiation step of PTGS that targets viral RNA for degrad ation.