Contact chemosensation in Drosophila: Genetics and anatomy

We have characterized the gustatory system of Drosophila with regard to the identification of gustatory receptor genes and the neuroanatomy of gustatory information processing in the Drosophila brain. These studies have also examined the role of these genes in other chemical senses.; Using computational biological techniques we were able to expand and characterize a previously identified gene family that appears to encode G-Protein coupled receptors. Using in situ hybridization, we were able to localize expression of members of this gene family to the chemosensory tissues of the gustatory and olfactory organs. We created transgenes using the putative promoter regions of these genes in combination with the bipartite GAL4-UAS expression system to allow expression of easily visualized marker proteins. Analysis of these transgenic flies demonstrated that individual members of this gene family are expressed in subsets of neurons of either the olfactory system or the gustatory system. Furthermore, genes expressed in the gustatory tissues are expressed in multiple gustatory organs distributed over the Drosophila body surface. We are able to begin making inferences about the discriminatory power of the Drosophila gustatory sense based on these expression patterns. Finally, we see that the larval Drosophila utilizes the same gene family for gustatory sensation albeit in a more limited manner.; We then used the aforementioned transgenes to begin tracing the neural circuitry of gustation in Drosophila. These experiments demonstrate that the distributed nature of the gustatory organs in the somatic body is reflected in an organotopic map within the CNS. This spatial segregation of gustatory neuron projections immediately suggests a mechanism by which the activation of a single species of receptor in different organs can give rise to different behavioral responses. This strategy is conserved between different developmental stages of Drosophila.