Dimeric artificial microRNAs mediate high resistance to RSV and RBSDV in transgenic rice plants

Infection of rice with Rice stripe virus (RSV) and Rice black streaked dwarf virus (RBSDV) causes a significant loss of grain production. Due to the lack of natural resistance resources against these viruses, it is imperative to discover a biotechnological approach that will provide effective and safe immunity to RSV and RBSDV. In this study, we constructed three dimeric artificial microRNA (amiRNA) precursor expression vectors (pamiR-M, pamiR-3 and pamiR-U) that simultaneously target the CP genes of RSV and RBSDV based on the structure of the rice (Oryza sativa L.) osa-MIR528 precursor. The transgenic plants were obtained by Agrobacterium tumefaciens-mediated transformation and were shown to express amiRNAs successfully. Viral challenge assays revealed that these transgenic plants demonstrated different resistance (26.66–54.17 %) against RSV and RBSDV infection simultaneously. The amiRNA-targeting 3′-UTR region of CP gene (pamiR-U) induced higher virus resistance: 54.17 % against RSV and 45.83 % against RBSDV. A northern blot assay indicated that there was a good correlation between the resistance level and amiRNAs accumulation. The RNA silencing induced by the original amiRNAs could be bilaterally extended by the siRNA pathway. The amiRNAs, together with the secondary siRNAs, mediated the degradation of viral RNAs. A genetic stability assay showed that transgenes and amiRNA-mediated virus resistance could be stably inherited in the transgenic plants.