Argonaute protein required for gene silencing in the endogenous RNA interference (RNAi) pathway (PubMed:17110334, PubMed:20133583). Involved in the 26G RNAi pathway and associates with both unmethylated and methylated 26G small interfering RNAs (26G-siRNAs), which are a class of 26 nucleotide siRNAs that possess a guanine residue at the 5'-end (PubMed:22102828, PubMed:22548001). Associated 26G-siRNAs are methylated by the methyltransferase henn-1, which stabilizes the siRNAs (PubMed:22548001). Association with 26G-siRNAs is required for the biogenesis of secondary 22G-siRNAs (a class of 22 nucleotide siRNAs that possess a triphosphorylated guanine residue at the 5'-end) (PubMed:22102828). May be involved in passenger strand cleavage of target 26G-siRNAs (PubMed:22102828). Interacts with rde-12 (PubMed:24684931). Interacts with rde-10 (PubMed:22542102). Highly expressed in the germline in hermaphrodites. Expressed in embryos and during larval development up to larval stage L2 (PubMed:20133583). Highly expressed in embryos (PubMed:22548001). Belongs to the argonaute family. Piwi subfamily.