Structure of plant-derived siRNAs. Analysis of siRNA by RPA on non-denaturing gels. Native RPA products from single synthetic c9si (o), Dc9si and three different Tc9 total RNA samples were analysed on a 15% non-denaturing PAGE gel (left hand side). Dc9si* that had been subjected to the Tc9 RNA extraction and purification regime (as described in Figure 4D) was also examined. Esi (-) or mEsi (m) (right hand side) were subjected to RPA analysis using increasing amounts of RNAses as indicated.