Search

RNA interference (RNAi) utilizes a conserved cellular autoimmune defense mechanism involving the internalization of dsRNA into cells and the activation of a set of RNAi related genes. Using RNAi, complete sex reversal is achievable in males of the prawnMacrobrachium rosenbergiiby knocking down the transcript level of an insulin-like androgenic gland hormone (Mr-IAG) through injections of dsRNA of the entireMr-IAGORF sequence (dsMr-IAG– 518bp). Interestingly,in-vivoknockdown success and dsMr-IAGlengths seemed to correlate, with long dsRNA being the most effective and short dsRNA fragments showing no effect. However, little is known about the RNAi machinery inM. rosenbergii. We discovered theMr-DicerandMr-Argonautegene families, associated with the major knockdown pathways, in ourM. rosenbergiitranscriptomic library. In response to dsMr-IAGadministration, only post-transcriptional pathway-related gene transcript levels were upregulated. In addition, a passive dsRNA channel (aSID1gene ortholog) that allows external dsRNA to enter cells was found. Its function was validated by observingMr-SID1specific upregulation dependent on dsRNA lengths, while attempted loss-of-function experiments were lethal. Our results, which suggest differential systemic responses to dsRNA lengths, provide evidence that the above RNAi-based manipulation occurs via the post-transcriptional pathway. The temporal nature of the latter pathway supports the safety of using such RNAi-based biotechnologies in aquaculture and environmental applications. Unlike reports of RNAi driven by the administration of small dsRNA fragmentsin-vitro, the case presented here demonstrates length dependencyin-vivo, suggesting further complexity in the context of the entire organism. [ABSTRACT FROM PUBLISHER]