Figure 1.

The small interfering RNA (siRNA) pathway in Drosophila melanogaster. Double-stranded RNA precursors of different sources are processed by Dicer-2 into short interfering RNAs of ~21 nt in size. The siRNA duplex is loaded into an Argonaute2 containing RISC complex, where one strand (passenger) is degraded, and the guide strand is retained. The guide strand mediates target RNA recognition through Watson-Crick base pairing, followed by target cleavage (slicing) by Argonaute. Loqs-PD is required for endo-siRNA biogenesis, but dispensable for viral siRNA (vsiRNA) biogenesis.