Drosophila CRY is a deep brain circadian photoreceptor

cry (cryptochrome) is an important clock gene, and recent data indicate tha t it encodes a critical circadian photoreceptor in Drosophila. A mutant all ele, cry(b), inhibits circadian photoresponses. Restricting CRY expression to specific fly tissues shows that CRY expression is needed in a cell-auton omous fashion for oscillators present in different locations. CRY overexpre ssion in brain pacemaker cells increases behavioral photosensitivity, and t his restricted CRY expression also rescues all circadian defects of cryb be havior. As wild-type pacemaker neurons express CRY, the results indicate th at they make a striking contribution to all aspects of behavioral circadian rhythms and are directly light responsive. These brain neurons therefore c ontain an identified deep brain photoreceptor, as well as the other circadi an elements: a central pacemaker and a behavioral output system.