Rice stripe virus (RSV) causes one of the most serious viral diseases of rice. RNA interference is one of the most efficient ways to control viral disease. In this study, we constructed an amiRNA targeting the RSV MP gene (amiR MP) based on the backbone sequence of the osa-MIR528 precursor, and obtained marker-free transgenic rice plants constitutively expressing amiR MP by Agrobacterium tumefaciens-mediated transformation. A transient expression assay demonstrated that dimeric amiR MP could be effectively recognized and cleaved at the target MP gene in plants. Northern blot of miRNA indicated that amiR MP-mediated viral resistance could be stably inherited. The transgenic rice plants were highly resistant to RSV (73–90%). Our research provides novel rice germplasm for RSV control.

MicroRNAs play key regulatory roles in plant development. The changed pattern of miRNA expression is involved in the production of viral symptoms. Here, we showed that a small RNA, Seq119, a putative novel microRNA, is associated with the low seed setting rate, a viral symptom of rice stripe virus (RSV)-infected rice. The expression of Seq 119 was downregulated in RSV-infected rice. The overexpression of Seq119 in transgenic rice plants did not cause any obvious phenotypic changes in plant development. When the expression of Seq119 was suppressed in rice plants either by expressing a mimic target or by CRISPR/Cas editing, seed setting rates were extremely low, similar to the effects of RSV infection. The putative targets of Seq119 were then predicted. The overexpression of the target of Seq119 in rice caused a low seed setting rate, similar to that in Seq119-suppressed or edited rice plants. Consistently, the expression of the target was upregulated in Seq119-suppressed and edited rice plants. These results suggest that downregulated Seq119 is associated with the low seed setting rate symptom of the RSV in rice.