Dr. Ana Maria Velez Arango
Dr. Joe Louis
Date of this Version
Sanchez, M. (2019). Identification and Evaluation of Chemoreceptor Genes in Western Corn Rootworm, Diabrotica Virgifera Virgifera Leconte, as Potential Targets for Pest Management (Master Thesis). University of Nebraska-Lincoln, Lincoln, Nebraska. United States of America.
The western corn rootworm (WCR), Diabrotica virgifera virgifera Le Conte, is the most significant pest of maize in the United States Corn Belt, where yield reduction and management cost exceed more than 1 billion dollars every year. Multiple pest management strategies have been developed for WCR, including use of synthetic insecticides, corn expressing proteins from the bacteria Bacillus thuringiensis (Bt), and cultural practices. However, the management of WCR is challenging for farmers due to the remarkable ability of this insect to evolve resistance to all of the mentioned pest management strategies. RNA interference (RNAi) is one of the newest molecular tools in the toolbox for managing this pest, but current RNAi-target genes are highly conserved housekeeping genes essential for insect survival, generating concerns about effects on non-target organisms. Chemoperception mechanisms have been demonstrated to be often species-specific among animals, which represents a potential field for target searching. Several studies have described the attraction effect of different exudates and volatiles from corn roots in WCR, including CO2 as the primary attractant, ethylene, β-caryophyllene, and benzoxazinoid complexes. Although the genetic mechanism of host finding is still understudied in this insect. Thus far, three chemoreceptor genes in the gustatory receptor (gr) family (gr1, gr2, and gr3) have been identified in WCR. Their function seems to be related to CO2 perception as described in other insect models.
The goal of this research was to evaluate the role of the reported Grs in WCR using a parental RNAi strategy in which adults received the double-stranded RNA (dsRNA) treatment, and the phenotype is assessed in the offspring. The results demonstrated the ability to knockdown of Grs through parental RNAi, and also the disruption in the CO2 finding behavior of larvae from the Gr2-dsRNA treatment. Additionally, novel chemosensory genes were identified and characterized as part of the repertory of genes that potentially participate in WCR host finding. These genes included ionotropic receptors (Irs), ionotropic glutamate receptors (iGluRs), transient receptor potential channel receptors (trps), and odorant-binding proteins (Obps). Results from this research provide foundational knowledge to species-specific chemoreceptor genes involved in WCR attraction to corn roots.
Advisors: Ana M. Vélez Arango and Joe Louis