1. Department of Biology and Biochemistry and Biological Clocks Program, University of Houston, Houston, Texas 77204, USA
2. Department of Biology and NSF Center for Biological Timing, Brandeis University, Waltham, Massachusetts 02454, USA
3. Department of Biological Sciences, University of Maine, Orono, Maine 04469, USA
4. These authors contributed equally to this work

Correspondence to: Paul E. Hardin² Correspondence and requests for materials should be addressed to P.E.H. (e-mail: Email: phardin@uh.edu).

Abstract

Cryptochromes are flavin/pterin-containing proteins that are involved in circadian clock function in Drosophila and mice. In mice, the cryptochromes Cry1 and Cry2 are integral components of the circadian oscillator within the brain^{1, 2, 3, 4, 5, 6} and contribute to circadian photoreception in the retina⁷. In Drosophila, cryptochrome (CRY) acts as a photoreceptor that mediates light input to circadian oscillators in both brain and peripheral tissue^{8, 9, 10, 11, 12}. A Drosophila cry mutant, cry^b, leaves circadian oscillator function intact in central circadian pacemaker neurons but renders peripheral circadian oscillators largely arrhythmic. Although this arrhythmicity could be caused by a loss of light entrainment, it is also consistent with a role for CRY in the oscillator. A peripheral oscillator drives circadian olfactory responses in Drosophila antennae¹³. Here we show that CRY contributes to oscillator function and physiological output rhythms in the antenna during and after entrainment to light–dark cycles and after photic input is eliminated by entraining flies to temperature cycles. These results demonstrate a photoreceptor-independent role for CRY in the periphery and imply fundamental differences between central and peripheral oscillator mechanisms in Drosophila.