Is nuclease activity limiting succesful RNAi gene silencing in Heliothis virescens larvae?

RNA interference (RNAi) is a gene silencing mechanism that involves targeted degradation of gene transcripts.  An effective RNAi gene silencing response can be obtained by delivery of double stranded RNA (dsRNA) into cultured insect cells, yet RNAi experiments in lepidopteran larvae are not always successful.  Our goal was to determine potential limitations hindering succesful in vivo RNAi in larvae of Heliothis virescens.  Using a bacterial system we adapted a protocol to produce purified dsRNA.  We tested stability of this dsRNA in midgut fluids from H. virescens larvae.  Our results suggest the existence of a nuclease activity that may hinder successful RNAi in H. virescens.  We are considering alternative approaches to in vivo RNAi for functional gene analyses in H. virescens.