Browsing by Author "Amrein, Hubert O"
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Item Open Access Analysis of the Drosophila Sugar Receptor Genes(2009) Slone, Jesse DavidGustation, also known as taste perception, is critical for the survival of most animal species. The fruit fly Drosophila melanogaster employs 68 different gustatory receptors (GRs) for the detection of sugars, bitter or toxic compounds, and pheromones. However, with a few notable exceptions, the functions of most GRs involved in feeding are unknown. Our research has focused on a cluster of highly-related Drosophila Grs, known as the Gr64 family, that have been shown to be critical for the perception of multiple sugars. Furthermore, we have demonstrated that another gene related to the Gr64 genes, Gr61a, is a sugar receptor that is narrowly tuned to a subset of pyranose sugars and may (along with the Gr64 genes) be indispensable for early fly development.
As a complementary approach to our behavioral analysis, we have examined the expression pattern of the Drosophila sugar receptors using knock-in driver alleles created by homologous recombination. As expected, most of these drivers have shown strong expression in various taste tissues. Intriguingly, some of these knock-in alleles also show expression in the maxillary palp and antenna, tissues previously thought to be involved only in olfaction. These expression patterns raise interesting questions about the true range of function of these chemosensory receptors and whether or not they might be involved in olfaction as well as gustation.
Item Open Access Investigation of the roX RNAs and the RNA Helicase MLE in Dosage Compensation in Drosophila melanogaster(2009) Hendricks, Dianne GrayceIn Drosophila melanogaster, where males are XY and females are XX, dosage compensation is acheived by approximately two-fold upregulation of transcription of the single male X chromosome. This upregulation is mediated by the dosage compensation complex (DCC), which is assembled in a sequential manner on the male X chromosome and is composed of the two noncoding roX (RNA on the X) RNAs and at least five proteins, including the RNA helicase Maleless (MLE). MLE contains two highly conserved double stranded RNA binding domains (DRBDs) at the N terminus. We investigated the roles of the roX RNAs and MLE helicase through experiments using classical genetic methods to generate and analyze the effects of mutants and mutant transgenes, immunolocalization experiments to study MSL protein and roX RNA to chromosomes. For the first time in vivo, we demonstrate that MLE associates with double stranded RNA in a sequence non-specific manner that is independent of other DCC components. Importantly, we find that the DSRBDs of MLE are essential for dosage compensation but are not required for MLE localization to the male X chromosome. We propose that although the DSRBDs are not essential for ds RNA binding, they may act synergistically with other domains of MLE or other MSLs to associate with RNA in vivo. We propose that a MLE/ roX RNA association involving secondary structure formed by the roX RNAs may be involved in the assembly, stabilization, or function of the DCC.
Item Open Access The Drosophila Gustatory Receptor Genes: the Molecular Basis of Taste Perception and Coding(2007-07-26) Thorne, NatashaDiscrimination between edible and contaminated foods is crucial for the survival of animals. In Drosophila, a family of gustatory receptors (GRs) expressed in taste neurons is thought to mediate the recognition of sugars and bitter compounds, thereby controlling feeding behavior. Using the Gal4/UAS system, we have characterized the expression of Gr genes in detail, and find that gene expression falls into two distinct groups. The first group, which make up the majority of the genes analyzed, are co-expressed with Gr66a, and functional ablation of taste neurons expressing these genes demonstrates that these neurons mediate sensitivity to bitter substrates. A second, distinct group of taste neurons, express Gr5a and mediate sensitivity to trehalose. We find that these two sub-populations of taste neurons - attractive-type and avoidance-type - project afferents to discrete areas of the primary taste center in the CNS. These results demonstrate how bitter and sweet taste are coded for in the periphery and indicates that information about different taste modalities is initially segregated in the CNS. We have also used the Gal4/UAS system to thoroughly characterize the expression profile of a cluster of six Grs - Gr28a and Gr28b.a-b.e. We find that these receptors are expressed not only in taste neurons, but other sensory neurons, as well as neurons in the CNS. RNA in situ hybridization confirms this unusual expression pattern. In order to explore the function of these Grs, these genes have been deleted using ends-out homologous recombination, to produce Gr28 mutant flies. Initial behavioral experiments with Gr28 mutant flies suggest that these receptors may play a role in detecting aversive substrates and/or modulate avoidance responses to these substrates.