RNA interference pathways can involve amplification of secondary siRNAs by RNA-dependent RNA polymerases. In plants, RDR6-dependent secondary siRNAs, including transacting siRNAs (tasiRNAs), arise from transcripts targeted by some microRNAs (miRNAs). In the case of TAS3 tasiRNA formation, ARGONAUTE7 (AGO7)-miR390 complexes interact with primary transcripts at two sites, resulting in recruitment...