Baum et al. [12] utilised a screening approach where
genes from WCR were identified in cDNA libraries, and
genes encoding polypeptides predicted to provide an essential
biological function were classified as ‘targets’. A total of
290 potential targets were identified, and corresponding
dsRNAs were synthesized in vitro; their effects on larval
performance were determined by delivery in artificial diet
feeding trials. Using this approach a total of 14 genes from
the initial list demonstrated specific downregulation
of target sequences at low dsRNA concentrations and
resulted in insect stunting and mortality. The most effective
dsRNA, directed against a gene encoding V-type
ATPase A, demonstrated rapid knockdown of endogenous
mRNA within 24 h of ingestion and triggered a specific
RNAi response with low concentrations of dsRNA. The
orally delivered dsRNA could produce systemic silencing
of genes (encoding both V-type ATPase subunits and btubulin)
throughout the insect.