A serious shortcoming of many insecticides is that they can kill non-target species.
To address this issue, we harnessed the sequence specificity of RNA interference (RNAi)
to design orally-delivered double-stranded (ds) RNAs that selectively killed target
species. Fruit flies (Drosophila melanogaster), flour beetles (Tribolium castaneum),
pea aphids (Acyrthosiphon pisum), and tobacco hornworms (Manduca sexta) were selectively
killed when fed species-specific dsRNA targeting vATPase transcripts. We also demonstrate
that even closely related species can be selectively killed by feeding on dsRNAs that
target the more variable regions of genes, such as the 3' untranslated regions (UTRs):
four species of the genus Drosophila were selectively killed by feeding on short (<40
nt) dsRNAs that targeted the 3' UTR of the gamma-tubulin gene. For the aphid nymphs
and beetle and moth larvae, dsRNA could simply be dissolved into their diets, but
to induce RNAi in the drosophilid species, the dsRNAs needed to be encapsulated in
liposomes to help facilitate uptake of the dsRNA. This is the first demonstration
of RNAi following ingestion of dsRNA in all of the species tested, and the method
offers promise of both higher throughput RNAi screens and the development of a new
generation of species-specific insecticides.