Ingested RNAi triggers can silence target genes in animals that lack SID-1 in the gut. (A) Expression of sid-1(+) in bwm is sufficient to silence gfp expression in bwm of sid-1(−) animals by feeding RNAi. Representative adult animals that express nuclear-localized gfp in all somatic cells (sur-5::gfp) and that are wild-type (Left), sid-1(−) (Middle), or mosaic sid-1(−) animals that express sid-1(+) only in the bwm (Right) are shown. Animals were fed E. coli that express gfp-hpRNA with an unc-22 loop sequence. bwm nuclei that express GFP (arrowheads) or that show silencing of GFP expression (circle) and gut nuclei (dashed outline), which do not show detectable silencing in sid-1(−) animals, are indicated. Most neuronal nuclei are not detectably silenced in all cases. (Insets): DIC and Red channel images. (Scale bar, 25 μm.) (B) Expression of sid-1(+) in bwm is sufficient to silence unc-22 expression in sid-1(−) animals by feeding RNAi. Wild-type, sid-1(−), and mosaic sid-1(−) animals that express sid-1(+) under the control of a bwm promoter (bwm::sid-1(+)) were fed either E. coli (white bar) or E. coli that express gfp-hpRNA with an unc-22 loop sequence (black bar) and were scored for unc-22 silencing (% twitching). All animals also express sur-5::gfp (as in A). n = 60 animals, error bars indicate 95% confidence intervals.