C. elegans genes showing correlated conservation patterns with RDE-1 are predicted to function in small RNA pathways such as miRNA and siRNA-based gene silencing. The signature phylogenetic profile of the Argonaute proteins is that they are absent in 9 out of 31 Ascomycota species, 1 out of 3 Basidiomycota species, and 6 out of 14 protist species, but have not been lost in any of the 33 animal or 6 land plant species compared. High-confidence candidates from this analysis were tested for defects in RNAi silencing. RDE-1 was used to generate a rank-order list of proteins with the similar phylogenetic profiles.