Editors' ChoiceSensory Perception

It Takes Two (Odorant Receptors)

Science's STKE  08 Mar 2005:
Vol. 2005, Issue 274, pp. tw87
DOI: 10.1126/stke.2742005tw87

The prevailing model for olfaction is that individual neurons express only one odorant receptor (OR). Goldman et al. challenge this view by finding that one olfactory receptor neuron (ORN) in Drosophila sensilla in the maxillary palp (a fly olfaction organ) expresses two highly divergent Or genes. Expression analysis indicated that seven Or genes were expressed in the six types of neurons found in maxillary palp sensilla. The authors constructed a receptor-to-neuron map of the ORNs in the maxillary palp and found that three Or genes were expressed in the pb2 class of sensilla (each class of sensilla consists of an A and a B type neuron). To determine whether the genes were expressed in the A or B neuron, the Or-specific promoters were used to express the proapoptotic protein Reaper, causing selective cell death in only one of the two neurons. When Or33c or Or85e promoters were used, the surviving neuron was pb2B. Thus, both Or33c and Or85e appear to be expressed in the pb2A neuron. In situ hybridization confirmed that Or85e and Or33c transcripts were present in the same ORN in three different species of fly; thus, this is an evolutionarily conserved pattern. Or85e and Or33c produced functional odorant receptors in an in vivo expression system. Coexpression of the two ORs in this system did not result in altered odorant perception compared with that of Or85e alone. However, the combined receptors may be specific for unidentified odorants. These results change the prevailing dogma and allow for a potential increase in complexity and specificity to odorant perception.

A. L. Goldman, W. Van der Goes van Naters, D. Lessing, C. G. Warr, J. R. Carlson, Coexpression of two functional odor receptors in one neuron. Neuron 45, 661-666 (2005). [PubMed]