Plays a role in germline RNA interference (RNAi), and in particular is required for piwi-interacting RNA (piRNA) gene silencing. Facilitates the binding of the argonaut protein hrde-1 to small interfering RNAs (siRNAs) targets that are required for transgenerational epigenetic inheritance and germline immortality. Expressed throughout the male and female germline. Mortal germline (Mrt) phenotype in which there is a progressive decline in fertility with each generation at 25 degrees Celsius, and after 2 to 3 generations the brood size is 25% that of wild-type counterparts. Fertility in these mutants may be restored when transferred to a 20 degrees Celsius environment. Defective RNAi inheritance.