Dejima, K.; Yoshida, K.; Mitani, S.

RNA interference (RNAi) is widely used in life science research and is critical for diverse biological processes, such as germline development and antiviral defense. In Caenorhabditis elegans, RNA-dependent RNA polymerases, with redundant involvement of EGO-1 and RRF-1, facilitate small RNA amplification in germline exogenous RNAi (exo-RNAi). However, their coordination during the regulation of exo-RNAi processes in the germline remains unclear. Here, we examined non-null mutants of the ego-1 gene and found that ego-1(S1198L) animals exhibited germline exo-RNAi defects with normal fertility, abnormalities in germ granules, and synthetic temperature-dependent sterility with rrf-1. The exo-RNAi defects in ego-1(S1198L) were partially restored by inhibiting hrde-1, cde-1, and znfx-1. Similar defects were observed in wild-type and ego-1(S1198L) heterozygous descendants derived from ego-1(S1198L), but these were suppressed by ancestral inhibition of rrf-1. These data reveal a dual role for EGO-1 in the positive regulation of germline exo-RNAi: it not only mediates target silencing through its RNA-dependent RNA polymerase activity, but also fine-tunes germ granule function or downstream processes, which are antagonized by RRF-1.