Dual roles of EGO-1 and RRF-1 in regulating germline exo-RNAi efficiency in Caenorhabditis elegans

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.