Animals change their behavior or metabolism to respond to temperature, an important environmental stimulus. In C. elegans, a behavioral response to temperature can be observed as thermotaxis behavior, in which wild-type animals migrate to the cultivation temperature on a thermal gradient after cultivation at a certain temperature with food. Thermotaxis requires food-associated learning of cultivation temperature and proper temperature sensing (Mori et al., 2007). Although several molecules involved in this behavior have been identified, the molecular basis on thermotaxis still remains to be elucidated. For shedding light into new molecules in thermosensory signaling pathway, we tried to isolate suppressor mutants for thermophilic abnormality of
ttx-4 mutant. Previous study reported that
ttx-4 mutant animals lacking novel Protein Kinase C (nPKC) migrate to higher temperature than the cultivation temperature (Okochi et al., 2005). nPKC is thought to act as a modulator of temperature signaling in AFD thermosensory neuron, yet how nPKC regulates thermosensory signals is unknown. Through our screening, two suppressor mutants were isolated. One mutant has a mutation in M01F1.7 gene that is homologous to rdgB (retinal degeneration B) gene in D. melanogaster and human
nir1-3. RDGB is known as phosphatidylinositole transfer protein and required for phototransduction (Trivedi and Padinjat, 2007). Domain structure between M01F1.7 and rdgB is well conserved. The finding of rdgB homolog in nematode's thermosensory pathway may imply that thermosensation in nematode and phototransduction in fly share the same molecular mechanisms. Another mutant has a mutation in C31H2.1 (
tbc-7) gene that encodes Rab GAP. We are analyzing phenotypes of these suppressor mutants in detail and conducting cell specific RNAi experiment for the candidate genes that are likely required for the same or related signaling pathways where M01F1.7 and C31H2.1 function. These analyses should reveal how TTX-4 (nPKC) regulates or is regulated by these suppressor genes, thereby identifying TTX-4 (nPKC)-mediated thermosensory signaling pathway in AFD thermosensory neuron.