Entomology, Department of


Date of this Version

Summer 8-2013


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Entomology, Under the Supervision of Nicholas J. Miller. Lincoln, Nebraska: August 2013

Copyright (c) 2013 Zixiao Zhao


The objectives of this research were to evaluate the effects of hydroxamic acids, a group of corn root defense substances on western corn rootworm (Diabrotica virgifera virgifera LeConte) larvae and identify putative molecular mechanisms for hydroxamic acid detoxification. Corn line 428G carries a homozygous mutant bx1 gene, which makes it unable to synthesis hydroxamic acids. In contrast, H88 is the wild type parental line of 428G and is able to synthesize hydroxamic acids. Larvae were fed on 428G and H88 roots for 7 days for comparison. No significant difference was observed in growth, development, or survival rate. A RNA-Sequencing study was conducted to identify the differentially expressed genes that responded to dietary hydroxamic acids. A larval transcriptome sequence was assembled de novo from RNA-Sequencing data. Nine gene sequences were declared significantly differentially expressed. A putative cytochrome P450 gene was up regulated in the larvae feeding on hydroxamic acid-containing corn roots (H88). The results of this research suggested that hydroxamic acids do not have a significant inhibitory effect on western corn rootworm larvae. An inducible mechanism, mediated by cytochrome P450s, may be involved in hydroxamic acid detoxification. The results of this research advanced current understanding of western corn rootworm-corn interactions, and also provided a foundation for further study of the molecular mechanisms of hydroxamic acid detoxification by western corn rootworm.

Advisor: Nicholas J. Miller

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