2: Double-stranded RNA uptake in the western corn rootworm

The western corn rootworm (WCR) is a major pest of corn in the United States Corn Belt. WCR has the remarkable ability to evolve resistance to multiple management strategies, including synthetic insecticides, crop rotation, and transgenic corn expressing proteins from Bacillus thuringiensis. New management strategies relying on diverse modes of action are necessary for sustainable WCR control. The most recent development for WCR management involves in planta RNA interference (RNAi). The plant expresses insect-specific double-stranded RNAs (dsRNAs) of housekeeping genes, triggering an RNAi response that leads to insect death. Understanding RNAi mode of action is essential to predict potential mechanisms of resistance. RNAi mode of action can be divided into three parts, dsRNA uptake, processing (core RNAi machinery), and systemic spread. Several studies have investigated the core RNAi machinery in multiple insect species, including WCR, but uptake and spread have not been fully characterized. The first RNAi resistant WCR colony generated from a field selected population was shown to be deficient in dsRNA uptake. Therefore, characterizing cellular uptake in WCR will help identify potential mechanisms of resistance. In this study, we used a combination of RNAi-of-RNAi and chemical inhibitors to evaluate the roles of endocytic processes and pattern recognition receptors in cellular dsRNA uptake in WCR. Results from this work will further the understanding of RNAi mode of action in WCR and resistance evolution, and potentially identify limiting factors in other insects.