Behavioral genetics of the Drosophila circadian system

Animal behavior arises from complex interactions between the genetic makeup of the animal with its environment. One behavior which has proven to be particularly amenable to genetic dissection is circadian rhythms. Circadian rhythms govern the recurrence of physiological and behavioral responses in anticipation of daily environmental changes. This thesis explores aspects of normal and pdf mutant circadian genetics in the model organism Drosophila.; The first study presented characterized the extent of Drosophila genes which displayed circadian modulations in transcript levels. These experiments were designed to identify novel genes with putative function in Drosophila circadian rhythms. Microarrays were used to monitor whole-genome transcript levels across time to compare normal and period mutant flies under light entraining (LD) and constant darkness (DD) conditions. A limited set of transcripts were found to display robust circadian fluctuations in normal flies. Unexpectedly, the period gene was found to have a large influence on non-circadian gene activation.; The second study stemmed from these microarray studies. Two candidate genes, Slob and CG5798, were chosen for preliminary characterization because of their robust transcript rhythms. SLOB was previously characterized as a modulator of the slowpoke potassium channel, itself thought to participate in fly circadian behavior. CG5798 was previously uncharacterized and predicted to encode a deubiquitinating enzyme. Such an enzyme could participate in the modulation of clock components such as PERIOD and TIMLESS, given their regulated degradation by the proteosome. Genetic misexpression, neuro-anatomic characterization, and Western blot experiments were performed.; The third and fourth studies characterized the function of the PDF neuropeptide in fly rhythms. Microarray studies comparing transcript rhythms in pdf01 mutants with that of normal flies showed that most, if not all, rhythmic transcripts in normal flies continued to cycle in the absence of pdf function. Time-series PERIOD immunostaining experiments were then performed to assess the status of the fly clock at the cellular level in pdf01 mutants. pdf was found to have both an input and output function within the fly circadian system, serving to synchronize the cell-autonomous clocks within the small ventral lateral neural group, and to drive normal molecular rhythms within the dorsal lateral neurons.