Identification and functional analysis of a novel receptor for an odorant, benzaldehyde, in Caenorhabditis elegans.

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The nematode Caenorhabditis elegans.detects many chemicals, wchich can be attractants or repellents. Although divergent seven transmembrane receptors have been reported candidates chemosensory receptors in C. elegans, only Odr-10 was identified as the receptor for an attractant, diacetyl. C06H5.7 encodes a seven transmembrane domain receptor as well as odr-10. However, it has not yet been predicted to be a candidate chemosensory receptor.In the present study, we show that C06H5.7 is likely to encode a receptor for the odorant benzaldehyde. Benzaldehyde exhibits attractive effects at low concentrations and repulsive effects at high concentrations. A null mutation in C06H5.7 caused a benzaldehyde-specific aversion defect, but not an attraction defect. C06H5.7 was expressed in the ASH chemosensory neurons, which senses many aversive stimuli. On the other hand, C06H5.7 was detected in neither AWA nor AWC neurons, which are required for chemotaxis to specific subsets of volatile attractants. The C06H5.7 cDNA rescued the benzaldehyde defect of C06H5.7 null mutant. Interestingly, C06H5.7 responded to analogues of bezaldehyde such as 3, 4-dihydroxybenzaldehyde, 3, 4-dihydroxybenzoic acid and 4-hydroxyphenyl lactic acid, but not bezaldehyde itself in electrophysiological analysis. In conclusion, C. elegans responded to benzaldehyde repulsion via C06H5.7 in ASH. Furthermore, C. elegans might detect the volatile odorant as their water-soluble analogs derived in mucosa membrane.