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 the germline of Caenorhabditis elegans, exogenous RNAi (exo-RNAi), the RNA-dependent RNA polymerases EGO-1 and RRF-1 play redundant roles in facilitating small RNA amplification. However, their coordination during the regulation of exo-RNAi processes in the germline remains unclear. Here, we examine non-null mutants of the ego-1 gene and find that ego-1(S1198L) animals exhibit 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) are partially restored by inhibiting hrde-1 and znfx-1. Germline exo-RNAi defects are observed in wild-type and ego-1(S1198L) heterozygous descendants derived from ego-1(S1198L), but these are suppressed by ancestral inhibition of rrf-1. Our 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 licenses exo-RNAi gene expression, which is antagonized by RRF-1.