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A novel circadianly expressed Drosophila melanogaster gene dependent on the period gene for its rhythmic expression
1Department of Biochemistry, Stanford University School of Medicine, CA 94305, USA.
Abstract:
The Drosophila melanogaster period (per) gene is required for expression of endogenous circadian rhythms of locomotion and eclosion. per mRNA is expressed with a circadian rhythm that is dependent on Per protein; this feedback loop has been proposed to be essential to the central circadian pacemaker. This model would suggest the Per protein also controls the circadian expression of other genetic loci to generate circadian behavior and physiology. In this paper we describe Dreg-5, a gene whose mRNA is expressed in fly heads with a circadian rhythm nearly identical to that of the per gene. Dreg-5 mRNA continues to cycle in phase with that of per mRNA in conditions of total darkness and also when the daily feeding time is altered. Like per mRNA, Dreg-5 mRNA is not expressed rhythmically in per null mutant flies. Dreg-5 encodes a novel 298 residue protein and Dreg-5 protein isoforms also oscillate in abundance with a circadian rhythm. The phase of Dreg-5 protein oscillation, however, is different from that of Per protein expression, suggesting that Dreg-5 and per have common translational but different post-translational control mechanisms. These results demonstrate that the per gene is capable of modulating the rhythmic expression of other genes; this activity may form the basis of the output of circadian rhythmicity in Drosophila.
Insights
The period (per) gene in fruit flies regulates circadian rhythms. A newly identified gene, Dreg-5, also shows rhythmic expression dependent on per, suggesting per controls multiple genes for daily rhythms.
Area of Science:
- Chronobiology
- Molecular Genetics
- Drosophila melanogaster research
Background:
- The Drosophila melanogaster period (per) gene is crucial for circadian rhythms.
- A feedback loop involving Per protein and per mRNA is thought to be essential for the central circadian pacemaker.
- The Per protein may regulate other genes to generate complex circadian behaviors.
Purpose of the Study:
- To identify and characterize novel genes regulated by the per gene.
- To investigate the role of Dreg-5 in the Drosophila circadian system.
- To understand the regulatory mechanisms controlling rhythmic gene expression in flies.
Main Methods:
- Northern blot analysis to detect Dreg-5 mRNA expression.
- Assessment of Dreg-5 mRNA cycling in constant darkness and altered feeding schedules.
- Analysis of Dreg-5 mRNA and protein expression in per null mutant flies.
- Protein isoform analysis to determine oscillation patterns.
Main Results:
- Dreg-5 mRNA exhibits a circadian rhythm in fly heads, closely mirroring per mRNA cycling.
- Dreg-5 mRNA rhythmicity persists under constant darkness and altered feeding times.
- Dreg-5 mRNA expression is abolished in per null mutant flies.
- Dreg-5 protein isoforms also oscillate with a circadian rhythm, but out of phase with Per protein.
Conclusions:
- The per gene modulates the rhythmic expression of other genes, such as Dreg-5.
- Dreg-5 and per share common translational but distinct post-translational control mechanisms.
- The per gene's ability to regulate downstream genes is fundamental to generating circadian output in Drosophila.