Effectiveness of specific RNA-mediated interference through
ingested double-stranded RNA in Caenorhabditis elegans
Ravi S Kamath, Maruxa Martinez-Campos, Peder Zipperlen, Andrew G Fraser
and Julie Ahringer
Address: Wellcome/CRC Institute, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR, UK.
Correspondence: Julie Ahringer. E-mail: firstname.lastname@example.org
Background: In Caenorhabditis elegans, injection of double-stranded RNA (dsRNA) results in the
specific inactivation of genes containing homologous sequences, a technique termed RNA-
mediated interference (RNAi). It has previously been shown that RNAi can also be achieved by
feeding worms Escherichia coli expressing dsRNA corresponding to a specific gene; this mode of
dsRNA introduction is conventionally considered to be less efficient than direct injection,
however, and has therefore seen limited use, even though it is considerably less labor-intensive.
Results: Here we present an optimized feeding method that results in phenotypes at least as
strong as those produced by direct injection of dsRNA for embryonic lethal genes, and stronger
for genes with post-embryonic phenotypes. In addition, the interference effect generated by
feeding can be titrated to uncover a series of hypomorphic phenotypes informative about the