Tomioka K, Miyasako Y, Umezaki Y
Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima Naka, Okayama 700-8530, Japan.
Acta Biol Hung. 2008;59 Suppl:149-55. doi: 10.1556/ABiol.59.2008.Suppl.23.
Drosophila shows bimodal circadian locomotor rhythms with peaks around light-on (morning peak) and before light-off (evening peak). The rhythm synchronizes to light and temperature cycles and the synchronization is achieved by two sets of clocks: one entrains to light cycles and the other to temperature cycles. The light-entrainable clock consists of the clock neurons located in the lateral protocerebrum (LNs) and the temperature-entrainable clock involves those located in the dorsal protocerebrum (DNs) and the cells located in the posterior lateral protocerebrum (LPNs). To understand the interaction between the light-entrainable and the temperature-entrainable clock neurons, locomotor rhythms of the mutant flies lacking PDF or PDF-positive clock neurons were examined. Under the light cycles, they showed altered phase of the evening peak. When exposed to temperature cycles of lower temperature levels, the onset of evening peak showed larger advance in contrast to those of wild-type flies. The termination of the peak also advanced while that of wild-type flies remained almost at the same phase as in the constant temperature. These results support our hypothesis that the PDF-positive light entrainable cells regulate the phase of the temperature entrainable cells to be synchronized to their own phase using PDF as a coupling mediator.
果蝇表现出双峰昼夜运动节律，峰值出现在光照开启前后（早晨峰值）和光照关闭前（傍晚峰值）。这种节律与光照和温度周期同步，且同步是通过两组时钟实现的：一组与光照周期同步，另一组与温度周期同步。可被光照同步的时钟由位于侧前脑（LNs）的时钟神经元组成，而可被温度同步的时钟涉及位于背前脑（DNs）的神经元以及位于后侧前脑（LPNs）的细胞。为了解可被光照同步和可被温度同步的时钟神经元之间的相互作用，研究了缺乏PDF或PDF阳性时钟神经元的突变果蝇的运动节律。在光照周期下，它们的傍晚峰值相位发生了改变。当暴露于较低温度水平的温度周期时，与野生型果蝇相比，傍晚峰值的起始提前幅度更大。峰值的终止也提前了，而野生型果蝇的峰值终止几乎与恒温时处于同一相位。这些结果支持了我们的假设，即PDF阳性的可被光照同步的细胞利用PDF作为耦合介质来调节可被温度同步的细胞的相位，使其与自身相位同步。
