Who watches the watchmen? RNAi pathway-derived ribosomal small RNAs burgeon in absence of piRNAs.

Instead of causing immediate sterility, loss of the C. elegans PIWI protein PRG-1 leads to accumulated infertility after tens of generations. In this issue of Developmental Cell, Wahba et al. show that this correlates with aberrant RNA interference pathway-dependent feed forward amplification of ribosomal siRNAs-the proposed accumulative sterility factor.