Fig. 1.

A model for the quelling and qiRNA pathway in vegetative cells in N. crassa repetitive transgenes (quelling) or the rDNA locus after DNA-damage induce the synthesis of aberrant RNAs by the DdRP activity of QDE-1 facilitated by QDE-3. The aberrant RNA is converted into dsRNAs by the RdRP activity of QDE-1. The Dicer proteins DCL-1 and DCL-2 cleave the dsRNAs into siRNAs or qiRNAs, which are then loaded onto the RNA-induced silencing complex (RISC) containing QDE-2 and QIP. QDE-2 and QIP convert the siRNA duplex into the mature siRNA, resulting in RISC activation and gene silencing of homologous RNAs