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https://hdl.handle.net/2142/86456
Description
Title
Chemoreceptors From the Hawk Moth Manduca Sexta L
Author(s)
Patch, Harland M.
Issue Date
2005
Doctoral Committee Chair(s)
Hugh Robertson
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
In this study I cloned and characterized four M. sexta chemoreceptors. Differential screening of a male antennal cDNA library before the publication of the Drosophila melanogaster genome yielded one G coupled-protein receptor that had no matches in Genbank databases and the results of RT-PCR and quantitative real-time PCR experiments show MsOr1 is expressed only in male antennae suggesting a male-specific function for this receptor. In situ hybridization revealed MsOr1 was expressed exclusively in a single cell associated with male-specific type-I trichoid sensilla further suggesting this receptor is involved in pheromone detection. The second receptor, MsOr2, was discovered using fully degenerate inosine primers designed to conserved motifs of a unique group of highly conserved odorant receptors. Comparison of RT-PCR, quantitative real-time PCR and in situ hybridization results with those of previously described odorant receptors in the DmOr83b subfamily show a strong sequence and expression pattern similarity. The third receptor described in this paper, MsOr3, was found by 5'-end sequencing of a normalized and subtracted cDNA library from male M. sexta antennae. RT-PCR and quantitative real-time PCR show that this receptor is expressed only in male and female antennae. Moreover, it is expressed at much higher levels in females, suggesting it functions as a general Or, perhaps tuned to plant volatiles. A gustatory receptor was sequenced from the labial palp mRNA of M. sexta using degenerate inosine primers designed to the conserved motifs of two gustatory receptors found in the Anopheles gambiae and Drosophila melanogaster genomes. This gene fragment codes for the C-terminal region of a gustatory protein with 73% identity to DmGr21a. In D. melanogaster DmGr21a has been show to detect CO2; I propose a similar function for MsGr1 based on sequence similarity and the exclusive expression of this gustatory receptor in the labial palps of M. sexta as revealed by RT-PCR and quantitative real-time PCR. Higher expression levels of this gene in female labial palps suggest an enhanced sensitivity to the odorant that binds MsGr1, perhaps indicating a role for CO2 in oviposition.
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