A new role for cryptochrome in a Drosophila circadian oscillator

Cryptochromes are flavin/pterin-containing proteins that are involved in ci rcadian clock function in Drosophila and mice. In mice, the cryptochromes C ry1 and Cry2 are integral components of the circadian oscillator within the brain(1-6) and contribute to circadian photoreception in the retina(7). In Drosophila, cryptochrome (CRY) acts as a photoreceptor that mediates light input to circadian oscillators in both brain and peripheral tissue(8-12). A Drosophila cry mutant, cry(b), leaves circadian oscillator function intac t in central circadian pacemaker neurons but renders peripheral circadian o scillators largely arrhythmic. Although this arrhythmicity could be caused by a loss of light entrainment, it is also consistent with a role for CRY i n the oscillator. A peripheral oscillator drives circadian olfactory respon ses in Drosophila antennae(13). Here we show that CRY contributes to oscill ator function and physiological output rhythms in the antenna during and af ter entrainment to light-dark cycles and after photic input is eliminated b y entraining flies to temperature cycles. These results demonstrate a photo receptor-independent role for CRY in the periphery and imply fundamental di fferences between central and peripheral oscillator mechanisms in Drosophil a.