It Takes Two to Sense CO 2

Abstract

Many insects detect CO 2 , thereby obtaining critical information about their environment; bloodsucking insects like mosquitoes, for instance, follow CO 2 trails to locate potential hosts. Drosophila detect CO 2 through a subset of olfactory sensory neurons that do not express odorant family receptors (known to sense other volatile chemicals) but do express Gr21a , which is classified as belonging to the gustatory receptor family (see Wilson). Jones et al . showed that a second gustatory receptor gene, Gr63a , was coexpressed with Gr21a in CO 2 -sensing neurons in both adult and larval Drosophila . Moreover, the mosquito homologs of Gr21a and Gr63a were coexpressed in a subset of neurons in the mosquito organ through which CO 2 ­­ is sensed. When Gr21a and Gr63a were coexpressed in neurons that are normally unresponsive to CO 2 , these neurons became responsive, although neither receptor alone was sufficient to confer CO 2 sensitivity. Furthermore, mutant flies lacking Gr63a were insensitive to CO 2 , as determined both behaviorally and through electrophysiological recordings. Thus, the authors conclude that coexpression of Gr21a and Gr63a is required for CO 2 detection in Drosophila , a finding that may have implications for the development of repellants against blood-feeding insects. W. D. Jones, P. Cayirlioglu, I. Grunwald Kadow, L. B. Vosshall, Two chemosensory receptors together mediate carbon dioxide detection in Drosophila . Nature 445 , 86-90 (2007). [PubMed] R. I. Wilson, Scent secrets of insects. Nature 445 , 30-31 (2007). [PubMed]