Fig. 2.

C. elegans RdRp RRF-1 enhances dsRNA-triggered silencing of exogenous target genes, whereas silencing of exogenous genes by EGO-1 under the control of UAST is dsRNA-independent. Crosses for obtaining the larvae illustrated above are shown in Supplementary Methods S2, online supplement. Each cross was set up in at least for four replicates, and about 12 1° instar larvae from each cross were randomly selected and checked for consistency of the fluorescence signal; three of these were randomly selected for photography. a, h, and n are positive controls for fluorescence from NaChbac.eGFP, syt.eGFP, or Rab4-mRFP, respectively; b and i show a reduction of green fluorescence signals, indicating that the EGFP transgenes were partially silenced with the introduction of the corresponding EGFP dsRNA; c and j show a dramatic further reduction in the green fluorescence signal after combination with the RdRp gene, rrf-1, indicating a dramatic enhancement of silencing of the EGFP gene. Addition of the rrf-1 gene resulted in no silencing enhancement in the absence of the dsRNA trigger for either GFP [d, k or for the RFP line (o)]. In contrast, total silencing of fluorescent protein gene expression was observed in the presence of ego-1, irrespective of whether the EGFP dsRNA hairpin was present (e, l) or not (g, m); the RFP gene was also silenced totally in the absence of any dsRNA trigger (p). Expression of the EGFP-linked NaChBac gene resulted in suspended larval development at the 1° instar stage (k). f is the negative control from w¹¹¹⁸ under a GFP filter (using a Leica MZ11 fluorescence microscope); for the RFP gene a TXR filter was used