Gene Expression and Behaviors Relating to Rotation Resistance in the Western Corn Rootworm, Diabrotica Virgifera Virgifera (Coleoptera: Chrysomelidae)
Knolhoff, Lisa Marie
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https://hdl.handle.net/2142/86467
Description
Title
Gene Expression and Behaviors Relating to Rotation Resistance in the Western Corn Rootworm, Diabrotica Virgifera Virgifera (Coleoptera: Chrysomelidae)
Author(s)
Knolhoff, Lisa Marie
Issue Date
2008
Doctoral Committee Chair(s)
Robertson, Hugh M.
Department of Study
Entomology
Discipline
Entomology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Entomology
Language
eng
Abstract
Yearly rotation of corn with another crop interrupts the life cycle of the western corn rootworm beetle (Diabrotica virgifera virgifera, Coleoptera: Chrysomelidae), but behavioral resistance to crop rotation is a major problem. Resistant adult females exhibit reduced fidelity to corn due to increased locomotor activity and lay their eggs in the soil of both in corn and soybean fields. This work is an examination of the rotation resistance trait at both the molecular and behavioral levels, which integrates gene expression, soybean herbivory, and behaviors relating to locomotor activity and oviposition. A key purpose of this study was to investigate a possible molecular mechanism or marker by utilizing microarray analysis to find gene expression differences relating to the rotation resistance trait. Expression of candidate genes was measured with real-time PCR, and they exhibit the predicted patterns from the microarray in independent samples across time and space. Rotation-resistant females have lower constitutive expression of genes involved in antibacterial defense, but many genes with higher expression have no matches to known proteins. In another set of experiments, gene expression was used to study how soybean herbivory relates to the rotation resistance phenotype; resistant females often feed on soybean foliage, even though the nutritional benefit is negligible. Ability to compensate for proteinase inhibition due to soybean herbivory by increasing expression of digestive proteinases is not a trait shared exclusively by rotation-resistant western corn rootworm beetles. Two proteinases, which were cathepsin B-like enzymes, exhibited consistent patterns of expression in response to inhibition of proteinase activity resulting from soybean herbivory. The relationship of soybean herbivory to oviposition and locomotor behaviors was examined in another set of experiments in a longitudinal study on individual females in the laboratory. The arena was designed to elicit differences in dispersal similar to those observed in the field. Oviposition in rotation-resistant females was influenced by soybean roots, and oviposition in wild-type females was influenced by whether they had fed on soybean. This work contributes to the broader understanding of the rotation resistance phenotype and provides a framework for further studies on the integration of behavior and associated molecular traits.
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