Wijnen Herman, Naef Felix, Boothroyd Catharine, Claridge-Chang Adam, Young Michael W
Laboratory of Genetics, The Rockefeller University, New York, New York, USA.
PLoS Genet. 2006 Mar;2(3):e39. doi: 10.1371/journal.pgen.0020039. Epub 2006 Mar 24.
The transcriptional circuits of circadian clocks control physiological and behavioral rhythms. Light may affect such overt rhythms in two ways: (1) by entraining the clock circuits and (2) via clock-independent molecular pathways. In this study we examine the relationship between autonomous transcript oscillations and light-driven transcript responses. Transcript profiles of wild-type and arrhythmic mutant Drosophila were recorded both in the presence of an environmental photocycle and in constant darkness. Systematic autonomous oscillations in the 12- to 48-h period range were detectable only in wild-type flies and occurred preferentially at the circadian period length. However, an extensive program of light-driven expression was confirmed in arrhythmic mutant flies. Many light-responsive transcripts are preferentially expressed in the compound eyes and the phospholipase C component of phototransduction, NORPA (no receptor potential), is required for their light-dependent regulation. Although there is evidence for the existence of multiple molecular clock circuits in cyanobacteria, protists, plants, and fungi, Drosophila appears to possess only one such system. The sustained photic expression responses identified here are partially coupled to the circadian clock and may reflect a mechanism for flies to modulate functions such as visual sensitivity and synaptic transmission in response to seasonal changes in photoperiod.
昼夜节律时钟的转录回路控制着生理和行为节律。光可能通过两种方式影响这些明显的节律：（1）通过调节时钟回路；（2）通过与时钟无关的分子途径。在本研究中，我们研究了自主转录振荡与光驱动转录反应之间的关系。在存在环境光周期和持续黑暗的条件下，记录了野生型和无节律突变型果蝇的转录谱。仅在野生型果蝇中可检测到12至48小时周期范围内的系统性自主振荡，且优先出现在昼夜节律周期长度。然而，在无节律突变型果蝇中证实了广泛的光驱动表达程序。许多光响应转录本在复眼中优先表达，光转导的磷脂酶C成分NORPA（无受体电位）是其光依赖性调节所必需的。尽管有证据表明蓝细菌、原生生物、植物和真菌中存在多个分子时钟回路，但果蝇似乎只拥有一个这样的系统。这里确定的持续光表达反应部分与昼夜节律时钟相关，可能反映了果蝇响应光周期季节性变化调节视觉敏感性和突触传递等功能的一种机制。
