Schendzielorz Julia, Schendzielorz Thomas, Arendt Andreas, Stengl Monika
Department of Biology, Animal Physiology, University of Kassel, Kassel, Germany.
Department of Biology, Animal Physiology, University of Kassel, Kassel, Germany
J Biol Rhythms. 2014 Oct;29(5):318-31. doi: 10.1177/0748730414546133. Epub 2014 Sep 17.
Pigment-dispersing factor (PDF) is the most important coupling factor of the circadian system in insects, comparable to its functional ortholog vasoactive intestinal polypeptide of the mammalian circadian clock. In Drosophila melanogaster, PDF signals via activation of adenylyl cyclases, controlling circadian locomotor activity rhythms at dusk and dawn. In addition, PDF mediates circadian rhythms of the visual system and is involved in entrainment to different photoperiods. We examined whether PDF daytime-dependently elevates cAMP levels in the Madeira cockroach Rhyparobia maderae and whether cAMP mimics PDF effects on locomotor activity rhythms. To determine time windows of PDF release, we searched for circadian rhythms in concentrations of cAMP and its functional opponent cGMP in the accessory medulla (AMe), the insect circadian pacemaker controlling locomotor activity rhythms, and in the optic lobes, as the major input and output area of the circadian clock. Enzyme-linked immunosorbent assays detected PDF-dependent increases of cAMP in optic lobes and daytime-dependent oscillations of cAMP and cGMP baseline levels in the AMe, both with maxima at dusk and dawn. Although these rhythms disappeared at the first day in constant conditions (DD1), cAMP but not cGMP oscillations returned at the second day in constant conditions (DD2). Whereas in light-dark cycles the cAMP baseline level remained constant in other optic lobe neuropils, it oscillated in phase with the AMe at DD2. To determine whether cAMP and cGMP mimic PDF-dependent control of locomotor activity rhythms, both cyclic nucleotides were injected at different times of the circadian day using running-wheel assays. Whereas cAMP injections generated delays at dusk and advances at dawn, cGMP only delayed locomotor activity at dusk. For the first time we found PDF-dependent phase advances at dawn in addition to previously described phase delays at dusk. Thus, we hypothesize that PDF release at dusk and dawn controls locomotor activity rhythms and visual system processing cAMP-dependently.
色素分散因子（PDF）是昆虫昼夜节律系统中最重要的耦合因子，类似于其在哺乳动物昼夜节律时钟中的功能同源物血管活性肠肽。在黑腹果蝇中，PDF通过激活腺苷酸环化酶发出信号，控制黄昏和黎明时的昼夜运动活动节律。此外，PDF介导视觉系统的昼夜节律，并参与对不同光周期的同步化。我们研究了PDF是否在白天依赖性地提高马德拉蜚蠊（Rhyparobia maderae）中的cAMP水平，以及cAMP是否模拟PDF对运动活动节律的影响。为了确定PDF释放的时间窗口，我们在附属髓质（AMe）（控制运动活动节律的昆虫昼夜节律起搏器）和视叶（作为昼夜节律时钟的主要输入和输出区域）中寻找cAMP及其功能拮抗剂cGMP浓度的昼夜节律。酶联免疫吸附测定法检测到视叶中cAMP的PDF依赖性增加以及AMe中cAMP和cGMP基线水平的白天依赖性振荡，两者在黄昏和黎明时达到最大值。尽管这些节律在恒定条件下的第一天（DD1）消失，但cAMP而非cGMP振荡在恒定条件下的第二天（DD2）恢复。在明暗循环中，其他视叶神经纤维中的cAMP基线水平保持恒定，而在DD2时它与AMe同步振荡。为了确定cAMP和cGMP是否模拟PDF对运动活动节律的依赖性控制，使用转轮试验在昼夜节律的不同时间注射这两种环核苷酸。注射cAMP在黄昏时产生延迟，在黎明时产生提前，而cGMP仅在黄昏时延迟运动活动。我们首次发现除了先前描述的黄昏时的相位延迟外，黎明时还有PDF依赖性的相位提前。因此，我们假设黄昏和黎明时的PDF释放以cAMP依赖性方式控制运动活动节律和视觉系统处理。
