A protein chimera for dsRNA binding and delivery into oocytes for large-scale gene silencing in crustacean aquaculture

RNA interference (RNAi) is one of the most intensively used gene silencing techniques for gene function studies and biotechnology applications. However, the gonads, specifically the ovary, of arthropods appear to be intractable to efficient gene silencing. In this article, we report the development of a tool for specific binding and delivery of double-stranded (ds) RNA to the crustacean oocyte for gene silencing. The tool, an oocyte-specific silencing protein chimera, which we designated OSSCot, is composed of a dsRNA-binding domain retrieved from a specific Macrobrachium rosenbergii dsRNA binding protein and 24-amino acid peptide derived from the yolk protein, vitellogenin. The results of the in vitro and in vivo examinations carried out in this study indicate that an OSSCot-piggybacked dsRNA specifically enters the oocytes. The results also indicate that the OSSCot protein protects the dsRNA from degradation by endonucleases in the ovary. When OSSCot was linked to the specific PAX6-like dsRNA of M. rosenbergii (where PAX6 is the master gene for eye development) and injected into the hemolymph of vitellogenic females, the expression of the RNAi enzyme machinery was enhanced, and eye development was impaired in the embryos of the treated females. These findings validate the concept of exploiting OSSCot to piggyback a functional dsRNA into crustacean oocytes for gene silencing. The newly developed tool will find application for oocyte-specific gene silencing in other crustacean species and for research and biotechnology applications.