Regulation of Temperature Recognition by Circadian Clock Neurons and Thermosensing Mechanism in Drosophila

Abstract

Temperature affects almost all aspects of living and survival in any organism. However, regarding the center of temperature recognition and mechanisms of thermosensation is little known. Using Drosophila which has central nerve system as a model system, total 27,000 independent lines of P-element inserted mutant flies were tested by temperature preference behavior in genome-scale. Among 27,000 fly lines, 13,700 lines were tested as the second part of screening and then 954 lines were selected as final thermomutant candidates. The one mutant that was isolated the first part of screening, han, preferred different temperature during the day and night. han null flies showed arrhythmic circadian behavior and HAN expressed specifically in 13 pairs of circadian clock neurons in adult brain. Recently HAN found out a receptor for the circadian clock neuropeptide PDF. And circadian mutant norpA, which has mutation in phosphoinositide (PI)-dependent phospholipase C (PLC) involved in phototransduction pathway by activation of TRPL channel are also isolated the second part of thermomutant screening. Together with these data, most animal display circadian rhythms and it is already known that these rhythms can be entrained by environmental stimuli not only daily light-dark but also temperature cycles. To examine whether circadian clock neurons are related thermosensation, flies whose neurons were inhibited by different circadian clock drivers were tested thermosensing behavior. When flies which were used tim-Gal4 driver show an abnormal temperature preference but the flies whose neurons are inhibited by per-Gal4 are normal temperature preference. Each fly line having different clock driver show different expression patterns at s-LNv, LNd and DN2 of circadian clock neurons. When s-LNv, DN1 neurons were inhibited, flies showed cryophilic temperature preference and flies which were inhibited in part of LNd neurons showed thermophilic distribution. As a result, s-LNv neurons ar...