Analysis of period mRNA cycling in Drosophila head and body tissues indicates that body oscillators behave differently from head oscillators.

The period (per) gene is thought to be part of the Drosophila circadian pacemaker. The circadian fluctuations in per RNA and protein that constitute the per feedback loop appear to be required for pacemaker function, and have been measured in head neuronal tissues that are necessary for locomotor activity and eclosion rhythms. The per gene is also expressed in a number of neuronal and nonneuronal body tissues for which no known circadian phenomena have been described. To determine whether per might affect some circadian function in these body tissues, per RNA cycling was examined. These studies show that per RNA cycles in the same phase and amplitude in head and body tissues during light-dark cycles. One exception to this is the lack of per RNA cycling in the ovary, which also appears to be the only tissue in which PER protein is primarily cytoplasmic. In constant darkness, however, the amplitude of per RNA cycling dampens much more quickly in bodies than in heads. Taken together, these results indicate that circadian oscillators are present in head and body tissues in which PER protein is nuclear and that these oscillators behave differently.