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
cry
b
. The
period
mutant
per
L
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
per
L
flies, because a
per
L
;
cry
b
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.
Temperature-dependent changes in circadian rhythms are mediated by interactions between the photoreceptor cryptochrome (CRY) and the proteins period (PER) and timeless (TIM).