Combinatorial RNA interference (RNAi) can target two genes in the same animal. Exposing worms to a mixture of two double-stranded (ds)RNA-expressing bacterial clones, one targeting lin-31 and the other one targeting sma-4, resulted in small worms with multiple vulvae along their ventral side. Shown are RNAi-hypersensitive rrf-3 animals  fed on bacteria expressing (a) a nontargeting dsRNA (control) and (b) combined bacterial clones expressing dsRNA against lin-31 and sma-4 (magnified in (c)). Pseudovulvae are indicated by white arrowheads.
Tischler et al. Genome Biology 2006 7:R69 doi:10.1186/gb-2006-7-8-r69