RNA interference of endoglucanases in the formosan subterranean termite Coptotermes formosanus shiraki (Blattodea: Rhinotermitidae) by dsRNA injection or ingestion

Abstract Termites obtain energy and nutrition from wood and wood-related materials by utilizing endogenous and symbiotic cellulases. Endoglucanase is one of the key cellulases in cellulose digestion. Previous studies have shown that the inhibition of the cellulase enzyme system would be a plausible approach for termite control. In the present study, we studied the effect of RNAi on termites by targeting a conserved region of five endoglucanase genes from Coptotermes formosanus ( CfEG s). Both dsRNA injection and oral delivery resulted in significant gene silencing of CfEG s and consequently led to mortality, reduced enzyme activity, and reduced weight compared to control worker termites. An injection dose of 150 ng and a feeding dose of 2 μg/cm 2 provided for the best RNAi efficiency. ds CfEG was further combined with flufenoxuron, an insect growth regulator used to manage/suppress subterranean termites, and when fed to workers, caused a lower enzyme activity compared to the ds CfEG - or flufenoxuron-only treatment. The weight loss (∼0.598 mg) and mortality (∼28%) observed in the combined ds CfEG and flufenoxuron treatment differed significantly from those observed in the flufenoxuron-only treatment (∼0.208 mg and ∼16%, respectively). Although the effects of these ds CfEG treatments on mortality were insufficient to serve as termiticides, ds CfEG s could be used in combination with other treatments to increase efficacy. This study provides a research basis for the use of RNAi in termiticides.