https://phys.org/news/2018-05-insights-clock-fruit.html

While the light-dependent mechanisms of synchronisation are well understood, very little is known about how temperature influences the circadian clock, and how light and temperature stimuli are mutually processed in the brain. To this end, Ralf Stanewsky and his team investigated the role a specific gene called nocte plays in this process.

Fruit flies with a non-functioning nocte gene are no longer able to synchronise their sleep rhythm based on the temperature of their environment. The abbreviation "nocte" stands for "no circadian temperature entrainment." The nocte mutants were, however, still able to use light input to synchronise their circadian clocks as long as the temperature around them remained constant. As soon as the light and temperature began to fluctuate simultaneously (which would normally occur at night when the temperature decreases), the circadian clock fell out of sync, which in turn disrupted the flies' sleeping rhythm. "We show that the nocte gene normally regulates the transmission of information on the environmental temperature to special 'clock neurons' in the brain. When this gene is missing, false temperature signals are sent to the clock neurons which then disrupts the fly's sleep pattern," says Ralf Stanewsky.