Circadian clocks: A receptor for subtle temperature changes.

Abstract

The protein IR25a is best known for its role as an odour receptor in flies, but an analysis reveals that it also acts to synchronize the circadian clock by sensing small temperature fluctuations. See Letter p.516 The roughly 24-hour period of circadian clocks is largely independent of ambient temperature but the phase can be synchronized, in the absence of light variations, to the cycle of warmer (day) and colder (night) temperatures, with a sensitivity as fine as ±2° C. Now Ralf Stanewsky and colleagues identify the chemosensory receptor IR25a, expressed in internal stretch (chordotonal) sensory neurons in the leg of Drosophila, as necessary for both behavioural and molecular synchronization of the animal's circadian clock to low-amplitude temperature cycles. They further show that this new temperature-sensing pathway functions independently from the known temperature sensors of the fly's antennas.