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Application of insect genomics in the identification of resistance mechanisms and novel target sites
Damage caused by the Western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, and the costs associated with its control in North American corn fields place this insect species as perhaps the most important pest throughout the U.S. Corn Belt. The unlimited capacity of WCR to sequentially evolve resistance to chemical insecticides and cultural control practices has made its control increasingly difficult. Seed treatment with neonicotinoid insecticides and transgenic corn hybrids expressing Bacillus thuringiensis toxins represent the two most recent novel control techniques currently used in rootworm management. However, the limited number of alternative control strategies and the remarkable history of rootworm adaptation call for the discovery of new biopesticide targets. Because of the success of Bt transgenic plants in controlling WCR, we believe that WCR gut represents a good target site for developing novel control agents. ^ The long term goal of this project is to develop the tools that will help reduce the importance of WCR as a pest in corn production by identifying novel receptors and enzymes within the WCR midgut as potential targets for alternative novel toxins. Specific objectives were to develop a system to identify genes and pathways important in conferring insecticide resistance to WCR, establish a system to disrupt WCR specific genes and identify WCR midgut genes as potential targets for novel insecticides. ^ Results from cDNA microarray hybridizations identified significant over-expression of one cytochrome P450 and two esterase genes in an organophosphate resistant strain, which were confirmed by qRT-PCR. This is the first report of specific genes related to organophosphate resistance in WCR populations. RNAi experiments involving silencing of laccase, chitin synthase 2, and a cellulase gene demonstrated that RNAi is a viable tool for gene silencing both epidermal and midgut tissues in WCR larvae. Successful silencing of WCR chitin synthase 2 through injection of dsRNA establishes the utility of RNAi as a tool to suppress midgut-specific genes, and provides an indication on the systemic nature of RNAi in this insect. Significant developmental effects on 2nd and 3rd instars upon cellulase dsRNA injection suggest that this gene could possibly serve as a putative novel target site. ^
Biology, Molecular|Biology, Entomology
Alves, Analiza P, "Application of insect genomics in the identification of resistance mechanisms and novel target sites" (2008). ETD collection for University of Nebraska - Lincoln. AAI3315331.