Boothroyd Catharine E, Wijnen Herman, Naef Felix, Saez Lino, Young Michael W
Laboratory of Genetics, The Rockefeller University, New York, New York, United States of America.
PLoS Genet. 2007 Apr 6;3(4):e54. doi: 10.1371/journal.pgen.0030054.
Circadian clocks are aligned to the environment via synchronizing signals, or Zeitgebers, such as daily light and temperature cycles, food availability, and social behavior. In this study, we found that genome-wide expression profiles from temperature-entrained flies show a dramatic difference in the presence or absence of a thermocycle. Whereas transcript levels appear to be modified broadly by changes in temperature, there is a specific set of temperature-entrained circadian mRNA profiles that continue to oscillate in constant conditions. There are marked differences in the biological functions represented by temperature-driven or circadian regulation. The set of temperature-entrained circadian transcripts overlaps significantly with a previously defined set of transcripts oscillating in response to a photocycle. In follow-up studies, all thermocycle-entrained circadian transcript rhythms also responded to light/dark entrainment, whereas some photocycle-entrained rhythms did not respond to temperature entrainment. Transcripts encoding the clock components Period, Timeless, Clock, Vrille, PAR-domain protein 1, and Cryptochrome were all confirmed to be rhythmic after entrainment to a daily thermocycle, although the presence of a thermocycle resulted in an unexpected phase difference between period and timeless expression rhythms at the transcript but not the protein level. Generally, transcripts that exhibit circadian rhythms both in response to thermocycles and photocycles maintained the same mutual phase relationships after entrainment by temperature or light. Comparison of the collective temperature- and light-entrained circadian phases of these transcripts indicates that natural environmental light and temperature cycles cooperatively entrain the circadian clock. This interpretation is further supported by comparative analysis of the circadian phases observed for temperature-entrained and light-entrained circadian locomotor behavior. Taken together, these findings suggest that information from both light and temperature is integrated by the transcriptional clock mechanism in the adult fly head.
昼夜节律时钟通过同步信号或授时因子与环境同步，这些信号如日常的光照和温度循环、食物供应以及社会行为。在本研究中，我们发现来自温度驯化果蝇的全基因组表达谱在有无温度循环的情况下显示出巨大差异。虽然转录水平似乎会因温度变化而广泛改变，但存在一组特定的温度驯化昼夜节律mRNA谱，它们在恒定条件下仍继续振荡。温度驱动或昼夜节律调节所代表的生物学功能存在显著差异。温度驯化的昼夜节律转录本集合与先前定义的一组响应光循环而振荡的转录本有显著重叠。在后续研究中，所有温度循环驯化的昼夜节律转录本节律也对光/暗驯化有反应，而一些光循环驯化的节律对温度驯化没有反应。编码时钟组件周期蛋白（Period）、无时间蛋白（Timeless）、时钟蛋白（Clock）、Vrille、PAR结构域蛋白1和隐花色素（Cryptochrome）的转录本在被每日温度循环驯化后均被证实具有节律性，尽管温度循环的存在导致周期蛋白和无时间蛋白在转录本水平而非蛋白质水平的表达节律之间出现了意外的相位差异。一般来说，那些对温度循环和光循环都表现出昼夜节律的转录本在被温度或光驯化后保持相同的相互相位关系。对这些转录本的温度和光共同驯化的昼夜节律相位的比较表明，自然环境中的光和温度循环协同调节昼夜节律时钟。对温度驯化和光驯化的昼夜节律运动行为所观察到的昼夜节律相位的比较分析进一步支持了这一解释。综上所述，这些发现表明，来自光和温度的信息在成年果蝇头部通过转录时钟机制整合在一起。
