Validation of RNA interference in western corn rootworm Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) adults

Background: RNA interference (RNAi) is commonly used in insect functional genomics studies and usually involves direct injection of double-stranded RNA (dsRNA). Only a few studies have involved exposure to dsRNAs through feeding. For western corn rootworm (Diabrotica virgifera virgifera) larvae, ingestion of dsRNA designed from the housekeeping gene, vacuolar ATPase (vATPase) triggers RNAi causing growth inhibition and mortality; however, the effect of dsRNA feeding on adults has not been examined. In this research, WCR adults were fed with vATPase-dsRNA-treated artificial diet containing a cucurbitacin bait, which is a proven feeding stimulant for chrysomelid beetles of the subtribe Diabroticina to which rootworms belong. Results: Real-time PCR confirmed suppression of vATPase expression and western blot analysis indicated reduced signal of a protein that cross-reacted with a vATPase polyclonal antiserum in WCR adults exposed to artificial diet treated with dsRNA and cucurbitacin bait. Continuous feeding on cucurbitacin and dsRNA-treated artificial diet resulted in more than 95% adult mortality within 2 weeks while mortality in control treatments never exceeded 20%. Conclusions: This research clearly demonstrates the effect of RNAi on WCR adults that have been exposed to dsRNA by feeding and establishes a tool to screen dsRNAs of potential target genes in adults. This technique may serve as an alternative to target screening of larvae which are difficult to maintain on artificial diets.