Student Theses and Dissertations

Date of Award

2006

Document Type

Thesis

RU Laboratory

Vosshall Laboratory

Keywords

olfaction, drosophila, olfactory sensory neurons, odarant receptors, chemotaxis behavior, olfaction in flies

Abstract

Drosophila melanogaster is a powerful genetic model organism, and a promising model system in olfaction. At the onset of my thesis research, the expression patterns of fly’s 62 odorant receptors (ORs) were largely unknown. I set out to understand the rules of connectivity of olfactory sensory neurons and the resulting properties of olfactory circuit. Consequently, we assembled maps of the olfactory neuron projections in the fly brain and characterized the contribution of several ORs to olfactory-guided behavior. We compiled near-complete maps of OR-specific neuronal projections to the antennal lobe glomeruli of adult and larval fly brains. We analyzed expression profiles of 42 ORs, 31 of which are expressed in the adult and 21 in the larva, with an overlap of 10 ORs between the two developmental stages. Our results show surprising complexity in organization of the fly’s olfactory circuit. Four adult olfactory neuron populations co-express two ORs each and another olfactory neuron population expresses one odorant and one gustatory receptor. One glomerulus receives co-convergent input from two separate populations of olfactory neurons. Three ORs label sexually dimorphic glomeruli implicated in sexual courtship, and are thus candidate Drosophila pheromone receptors. The organization of larval antennal lobe is remarkably similar to that of adult flies and mammals; each glomerulus occupies a unique stereotyped position in the antennal lobe. Unlike in adults, each OR is expressed in only one neuron, forming glomeruli with single afferents. The olfactory sensory maps provide experimental framework for relating ORs to olfactory neuroanatomy, and ultimately, to output of the olfactory system. The Drosophila larval olfactory system shows great promise as a behavioral model. Larvae exhibit robust chemotaxis to odors and have a simple olfactory system. We utilized larvae to study response properties of three olfactory neurons to a large panel of odors. Behavioral assays of larvae with single olfactory neurons ablated, showed minimal effects on chemotaxis response, and thus great redundancy in function of olfactory neuron populations. Larvae with only Or42a olfactory neurons functional are able to chemotax robustly, demonstrating that chemotaxis is possible in the absence of the remaining elements of the olfactory circuit.

Comments

A thesis presented to the faculty of The Rockefeller University in partial fulfillment of the requirements for the degree of Doctor of Philosophy.

Permanent URL

http://hdl.handle.net/10209/120

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