A concise overview of circadian timing in Drosophila

The molecular aspects of circadian rhythmicity in Drosophila melanogaster are reviewed, with particular regard to the core of the master oscillator and the light signalling input pathway. The core is schematically represented as consisting of two interlocking transcriptional feedback loops based principally on the clock genes period, timeless, clock and cycle and their products which, through the interaction with other partners, give rise to a stable 24h endogenous oscillator. Light signalling to the clock is multifaceted and is still the subject of much speculation and research. Here we review data essentially regarding the role of the clock protein Timeless and its interaction with the photopigment Cryptochrome.