C. elegans senses the environmental temperature by AFD and AWC sensory neurons. Genetic analysis suggested that signal transduction of thermosensory system in AFD and AWC is similar to that of olfactory and visual system in C. elegans and other animals (Mori et al., 2007; Kuhara et al., 2008). Based on the analogy to olfactory and visual system, it is plausible to hypothesize that G protein-coupled receptors (GPCRs) sense the environmental temperature. Previous reports showed that
srtx-1 encoding GPCR is specifically expressed in sensory ending of both AFD and AWC neurons (Colosimo et al., 2004; Biron et al., 2008). We evaluated the expression of
srtx-1 in detail by comparing fluorescence intensities of
srtx-1promoter::GFP in AFD and AWC. Our results suggest that
srtx-1 is expressed strongly in AFD, very weakly in AWC OFF neuron, and not expressed in AWC ON neuron. We generated two deletion mutants,
srtx-1(
nj62) and
srtx-1(
nj63), and found that both mutants exhibited impaired thermotaxis. Wild type animals migrated to the previous cultivation temperature after cultivation at 17, 20 or 23 degree on a temperature gradient. The
srtx-1 mutants however migrated to colder region than the cultivation temperature after cultivated at 23 degree, and slightly but significantly migrated to colder region than the cultivation temperature after cultivation at 20 degree. By contrast,
srtx-1 mutants migrated to higher region than the cultivation temperature after cultivation at 17 degree. The expression of strx-1cDNA only in AFD restored the abnormalities of thermotaxis. When strx-1cDNA was overexpressed in AFD of wild type animals, the distribution on a temperature gradient of animals cultivated at 17 and 20 degree was shifted to higher region. According to all these results, we propose that STRX-1(GPCR) is a key component for thermosensation in AFD, somewhat regulates temperature sense range.We thank D. Garbers forgcy-8p promoter, H. Oliver forceh-36 partial promoter, H. Inada for TMV-UV library, T. Kohashi for advice to assay systems.