The Molecular Basis of Odor Coding in the Drosophila Antenna

Abstract

We have undertaken a functional analysis of the odorant receptor repertoire in the Drosophila antenna. Each receptor was expressed in a mutant olfactory receptor neuron (ORN) used as a "decoder," and the odor response spectrum conferred by the receptor was determined in vivo by electrophysiological recordings. The spectra of these receptors were then matched to those of defined ORNs to establish a receptor-to-neuron map. In addition to the odor response spectrum, the receptors dictate the signaling mode, i.e., excitation or inhibition, and the response dynamics of the neuron. An individual receptor can mediate both excitatory and inhibitory responses to different odorants in the same cell, suggesting a model of odorant receptor transduction. Receptors vary widely in their breadth of tuning, and odorants vary widely in the number of receptors they activate. Together, these properties provide a molecular basis for odor coding by the receptor repertoire of an olfactory organ.

Taste and pheromone perception in the fruit fly Drosophila melanogaster

“…There is evidence for mammalian chemoreceptors and Drosophila olfactory receptors with high sequence similarity to recognize structurally related ligands [45][46][47][48]. Thus, GRs within a subfamily are thought to detect structurally similar taste compounds.…”

Generation and modulation of chemosensory behaviors in C. elegans

“…Only one chemical has been linked to its cognate receptor [56,131]; the ligands for other receptors are as yet unknown. Remarkable strides have been made in defining receptorligand interactions in other systems (e.g., [132][133][134][135]), so it is surprising that so little is known about this issue in the C. elegans chemosensory system. Part of this lack of knowledge may be attributed to the large size of the C. elegans CR gene family, which makes it difficult to employ the type of analysis that has been used so elegantly and effectively to "de-orphanize" Drosphila olfactory receptor genes [132,133].…”

“…It is also possible that while the core components of the signal transduction pathways are shared, additional molecules act in an odorant pathwayspecific manner [140], allowing the neuron to discriminate between multiple chemical cues. Finally, discrimination may also be effectively achieved by the activation or inhibition of different CRs expressed in a given neuron by different chemicals, or via differential temporal dynamics of CR function [132,133,152]. Identification of additional signaling molecules, and characterization of protein function, including CRs, will be necessary to fully address this issue.…”

A microfluidics-based method for measuring neuronal activity in Drosophila chemosensory neurons

“…The fruit fly Drosophila melanogaster is widely used as a genetic model organism to uncover basic mechanisms of taste coding and odor perception [1][2][3][4][5][6][7] . Recent insights into the molecular and functional mechanisms of sensory perception in Drosophila have been achieved by the use of single-sensillum recordings of adult taste or olfactory sensilla 1,4,[8][9][10][11][12][13] . This method enables sensitive measurements of action potential patterns and shows whether responses are excitatory or inhibitory, but drawing final conclusions about the individual firing neuron is difficult, as each sensillum contains two to four neurons 14 .…”