Molecular rhythms that regulate rhythm genes in Drosophila

Abstract

Almost all living organisms display rhythms in their activities coinciding with the day-night cycles. Our current understanding of the molecular regulation of circadian rhythmicity in Drosophila comes from studies integrating genetics and molecular biology, and Drosophila is perhaps one of the best understood models in the field of circadian rhythm research. Following the initial discovery of the per (period) gene some decades ago, several other genes, viz. timeless, dclock, cycle, and double-time, that function in the generation of circadian rhythms, have been identified during the past three years: Molecular genetic studies have provided exciting insights into the regulation of the body clocks. Heterodimeric complexes of positive elements (dCLOCK and CYCLE) and their interactions with feedback loops and negative elements of per and tim genes and their products have been identified and these are providing clues to the general layout of the molecular loops that generate circadian rhythms. The lark gene, which encodes an RNA-binding protein, might function as a regulatory element in the circadian clock output pathway controlling pupal eclosion rhythms. However, a clear picture of the output pathways or downstream processes through which the clock regulates the circadian rhythmic events is yet to be understood.