Temperature sensation is critical for all organisms to find an optimal habitat and many temperature-sensitive TRP channels appeared to participate in thermosensory/regulatory mechanisms. We recently reported that Drosophila melanogaster TRPA1 is regulated in the downstream of Rhodopsin (Rh)1/Gq/PLC cascade to avoid suboptimal temperatures in 18~24^oC (ref. 1 and 2). We further examined the property of temperature responsiveness of larvae and found that wild-type shows age-dependent shift in the temperature preference: the 2nd instar larvae do not discriminate between 18 and 23^oC, whereas the late 3rd instar larvae predominantly prefer 18^oC. Interestingly, Rh1 participation in the temperature preference was obvious in the early stage but not the late stage. We screened other Rh subtypes and identified Rh5 and Rh6 as critical components in the temperature preference throughout the larval stages: the 2nd instar larvae of rh5 and rh6 mutants strongly prefer 23^oC over 18^oC, and the late 3rd instar larvae show no preference between 18 and 23^oC.
Expression of Rh5 and Rh6 is apparent in the larval photo-sensitive organ (Bolwig organ) which is involved in light avoidance. However, acute light stimulation did not affect the cool preference at the late stage in wild-type larvae, suggesting that the function of Rh5 and Rh6 in Bolwig organ is independent from the temperature discrimination. Instead, we found that Rh5 and Rh6 in trpA1-positive neurons in brain are important for temperature preference; the knockdown of rh5 and rh6 mRNA in the trpA1-positive neurons in brain phenocopied the mutants, whereas the knockdown in the trpA1-positive peripheral neurons showed wild-type phenotype. All together, we propose the unconventional role of Rh5 and Rh6 in CNS in the thermosensory modality.

1) Control of thermotactic behavior via coupling of a TRP channel to a phospholipase C signaling cascade. Nat Neurosci. 2008, 11(8):871-3.
2) Function of rhodopsin in temperature discrimination in Drosophila. Science. 2011, 331(6022):1333-6