RESUMO
Drosophila circadian oscillators comprise interlocked period (per)/timeless (tim) and Clock (Clk) transcriptional/translational feedback loops. Within these feedback loops, CLOCK (CLK) and CYCLE (CYC) bind E-box elements to activate per and tim transcription, and we now show that at the same time CLK-CYC repress Clk by activating the transcriptional repressor vrille (vri), thus accounting for the opposite cycling phases of these transcripts and identifying vri as the negative component of the Clk-feedback-loop. The core oscillator mechanism is assumed to be the same for oscillators in different tissues. However, we have shown that CRYPTOCHROME (CRY) has a light-independent function in the oscillator that controls olfaction rhythms, suggesting that CRY may function within the oscillator mechanism itself as it does in mammals. These olfaction rhythms require the function of 'peripheral' oscillators which are distinct from the 'central' lateral neuron (LN) oscillators that mediate locomotor activity rhythms. Preliminary results show that antennal oscillator cells are sufficient and LNs are not necessary for olfaction rhythms, indicating that unlike the situation in mammals, the central oscillator has little impact on the olfaction rhythm oscillator under these conditions.
Assuntos
Ritmo Circadiano/fisiologia , Drosophila/fisiologia , Animais , Proteínas CLOCK , Ritmo Circadiano/genética , Criptocromos , Drosophila/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/fisiologia , Proteínas do Olho/genética , Proteínas do Olho/fisiologia , Retroalimentação , Genes de Insetos , Modelos Biológicos , Proteínas Nucleares/genética , Proteínas Nucleares/fisiologia , Proteínas Circadianas Period , Células Fotorreceptoras de Invertebrados/fisiologia , RNA/genética , RNA/metabolismo , Receptores Acoplados a Proteínas G , Fatores de Transcrição/genética , Fatores de Transcrição/fisiologiaRESUMO
In the Drosophila circadian clock, daily cycles in the RNA levels of dclock (dClk) are antiphase to those of period (per). We altered the timing/levels of dClk expression by generating transgenic flies whereby per circadian regulatory sequences were used to drive rhythmic transcription of dClk. The results indicate that posttranscriptional mechanisms make substantial contributions to the temporal changes in the abundance of the dCLK protein. Circadian regulation is largely unaffected in the transgenic per-dClk flies despite higher mean levels of dCLK. However, in per-dClk flies the duration of morning activity is lengthened in light-dark cycles and light pulses evoke longer lasting bouts of activity. Our findings suggest that, in addition to a role in generating circadian rhythms, dCLK modulates the direct effects of light on locomotion.