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Exploration into the Western Corn Rootworm, Diabrotica virgifera virgifera, RNA Interference Mechanism
The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is a significant insect pest of corn in the United States (U.S.) Corn Belt. Various pest management tactics have been deployed to control WCR. However, WCR's ability to evolve resistance has challenged insect management capabilities over the years, necessitating the development of novel modes of action (M.O.A.) to maintain populations to acceptable levels. The next M.O.A. for WCR management relies on the insect's RNA interference (RNAi) pathway. RNAi is a post-transcriptional gene silencing mechanism triggered by double-stranded RNA (dsRNA). The first commercially approved dsRNA-based insecticide targets WCR larvae and was released in 2022. Characterizing insecticidal M.O.A. is essential for identifying, monitoring, and mitigating resistance. This research aimed to further our understanding of the WCR RNAi mechanism, focusing on cellular uptake of dsRNA, physiological factors influencing dsRNA susceptibility, and the effect of life stage on RNAi response. The first objective identified a role for scavenger receptors in dsRNA cellular internalization in adult WCR and reiterated previous findings that clathrin-mediated endocytosis is the primary route dsRNA takes to cross the plasma membrane. The second objective concluded that WCR DvSnf7 dsRNA susceptibility is affected by life stage, sexual dimorphism, and geographical location. Gene expression analysis determined that exogenous dsRNA alters the expression of siRNA, miRNA, and piRNA RNAi-related genes, suggesting crosstalk between the three RNAi pathways in WCR. The third objective characterized physiological differences that may influence dsRNA susceptibility between life stages within the genus Diabrotica through RNA-seq. Life stage and species significantly impacted RNAi, endocytosis, and immunity-related transcript expression. This objective also provided novel RNAi M.O.A. targets warranting further examination in WCR, spanning dsRNA transport, ancillary silencing components, and vesicle-mediated transport. This research provides novel physiological data related to RNAi, endocytosis, and immunity in the WCR, an agriculturally important insect species. These results can be used to further our understanding of the biological response to dsRNA and inform innovative pest management targets.
Darlington, Molly, "Exploration into the Western Corn Rootworm, Diabrotica virgifera virgifera, RNA Interference Mechanism" (2022). ETD collection for University of Nebraska - Lincoln. AAI30000248.