Abstract
Drosophila cryptochrome (CRY) is a key circadian photoreceptor that interacts with the period and timeless proteins (PER and TIM) in a light-dependent manner. We show here that a heat pulse also mediates this interaction, and heat-induced phase shifts are severely reduced in the cryptochrome loss-of-function mutant cryb. The period mutant perL manifests a comparable CRY dependence and dramatically enhanced temperature sensitivity of biochemical interactions and behavioral phase shifting. Remarkably, CRY is also critical for most of the abnormal temperature compensation of perL flies, because a perL; cryb strain manifests nearly normal temperature compensation. Finally, light and temperature act together to affect rhythms in wild-type flies. The results indicate a role for CRY in circadian temperature as well as light regulation and suggest that these two features of the external 24-h cycle normally act together to dictate circadian phase.
Highlights
Most organisms have circadian rhythms of gene expression and behavior that are controlled by endogenous clocks
An interaction between the circadian photoreceptor CRYPTOCHROME (CRY) and a complex composed of the key circadian regulators PERIOD (PER) and TIMELESS (TIM) are critical for circadian temperature responses as well a circadian light responses
We found a surprising relationship between the response of the Drosophila clock to heat pulses and light pulses as well as between heat pulses and temperature compensation; the connector is the photoreceptor CRY
Summary
Most organisms have circadian rhythms of gene expression and behavior that are controlled by endogenous clocks. The central pacemaker of animals is proposed to consist of autoregulatory feedback loops that regulate the expression of key clock genes [2]. An admittedly simplified view of the Drosophila central clock posits a core system of four interacting regulatory proteins. A circadian cycle begins when a CLOCK (CLK) and CYCLE (CYC) heterodimer activates the expression of two other proteins, PERIOD (PER) and TIMELESS (TIM). PER-TIM complexes enter the nucleus and inactivate CLOCK-CYCLE activity, slowing their own production and signaling the end of a cycle. Kinases and phosphatases modify PER, TIM, and CLK and play critical roles in circadian rhythms [3,4,5,6,7]
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