Ingestion of bacteria expressing dsRNA triggers specific RNA silencing in shrimp

RNAi activation in shrimp through dsRNA injection has been well demonstrated but oral delivery of dsRNA remains controversial. Therefore, this study was conducted to determine whether RNAi was induced in shrimp by ingestion of bacteria expressing dsRNA. We fed shrimp, Penaeus monodon and Litopenaeus vannamei, with inactivated bacteria expressing dsRNA specific to the shrimp genes (Rab7 and STAT). Forty-eight hours after 6 day-continuous feeding, the level of the targeted gene transcript was measured by semi-quantitative RT-PCR. Significant reduction of Rab7 as well as STAT transcript was observed when compared to that of control shrimp fed with bacteria containing the empty vector or bacteria expressing non-related dsRNA (GFP). Moreover, the suppression was detected not only in the hepatopancreas but also in the gills indicating the successful systemic induction of RNAi via oral delivery of dsRNA. Our results suggested that RNAi in shrimp could be triggered by ingestion of dsRNA expressing bacteria. Therefore, oral feeding is a practical approach which can be used to deliver dsRNA for further viral inhibition in farmed shrimp.