C. elegans senses the environmental temperature by AFD and AWC sensory neurons. Genetic analysis suggested that signal transduction of temperature in AFD and AWC is similar to that of olfactory and visual system in C. elegans and other animals (Mori et al., 2007). Although thermoreceptor itself is not identified, it is plausible that GPCRs sense the environmental temperature based on analogy to olfactory and visual system. It has been reported that
srtx-1 encodes GPCR and expressed in sensory ending of both AFD and AWC (Colosimo et al., 2004, Biron et al., 2008). To examine the more detail of
srtx-1 gene expression, we analyzed the promoter::GFP fusion gene. We newly found that
srtx-1p::GFP was expressed strongly expressed in AFD and very weakly only in AWC OFF neuron. To examine
srtx-1 gene function, we isolated two deletion mutants,
nj62 and
nj63. From deletion sites, both alleles are likely to be null. When they are cultivated in 20 or 23 degree, they migrated to the lower temperature than wild type. On the other hand, when they are cultivated at 17 degree, they migrated to the higher temperature than wild type. These results suggest that
srtx-1 mutants can not response to the wide range of temperature from 17 to 23 degree, but only sense the smaller range of temperature.Next, we asked the cellular site of action. We expressed strx-1cDNA under the AFD or AWC specific promoter in
nj62 mutants and examined the thermotaxis after the cultivation at 23 degree. The expression in AFD almost completely restored cryophilic phenotype of
nj62 mutants, however the expression in AWC did not. These results suggest that STRX-1/GPCR function in AFD, not in AWC OFF is sufficient to thermotaxis at 23 degree, consistent with the expression pattern that the strong expression in AFD and the faint in AWC OFF. We are now undergoing the ectopic and overexpression experiments to further know the function of STRX-1/GPCR. The starvation is known to affect the thermotaxis (Hedgecook and Russell, 1975; Mori and Ohshima, 1995). When animals are cultivated at 23 degree with no food, wild type cancel the migration to 23 degree and instead migrate to both higher and lower temperature region than 23 degree. We found that
nj62 mutants always migrate only to lower temperature region after starvation at 23 degree. These results suggest that thermal preference to low temperature in
nj62 is crucial for thermotaxis after starvation. In sum, STRX-1/GPCR is key player for proper migration to cultivation temperature both fed and starved conditions. We thank T. Ishihara for
nhr-38:(H13)promoter, H. Oliver for
ceh-36 partial promoter, H. Inada for TMV-UV library.