cryptochrome mediates light-dependent magnetosensitivity of drosophilas circadian clock隐花色素调节依赖光magnetosensitivity果蝇的生物钟.pdfVIP

PLoS BIOLOGY Cryptochrome Mediates Light-Dependent Magnetosensitivity of Drosophila’s Circadian Clock 1 2 ¨ 1* Taishi Yoshii , Margaret Ahmad , Charlotte Helfrich-Forster ´ 1 University of Regensburg, Institute of Zoology, Regensburg, Germany, 2 Universite Paris VI, PCMP, Paris, France Since 1960, magnetic fields have been discussed as Zeitgebers for circadian clocks, but the mechanism by which clocks perceive and process magnetic information has remained unknown. Recently, the radical-pair model involving light- activated photoreceptors as magnetic field sensors has gained considerable support, and the blue-light photoreceptor cryptochrome (CRY) has been proposed as a suitable molecule to mediate such magnetosensitivity. Since CRY is expressed in the circadian clock neurons and acts as a critical photoreceptor of Drosophila’s clock, we aimed to test the role of CRY in magnetosensitivity of the circadian clock. In response to light, CRY causes slowing of the clock, ultimately leading to arrhythmic behavior. We expected that in the presence of applied magnetic fields, the impact of CRY on clock rhythmicity should be altered. Furthermore, according to the radical-pair hypothesis this response should be dependent on wavelength and on the field strength applied. We tested the effect of applied static magnetic fields on the circadian clock and found that flies exposed to these fields indeed showed enhanced slowing of clock rhythms. This effect was maximal at 300 lT, and reduced at both higher and lower field strengths. Clock response to magnetic fields was present in blue light, but absent under red-light illumin