Bertossa Rinaldo C, van de Zande Louis, Beukeboom Leo W, Beersma Domien G M
Department of Molecular Neurobiology, Centre for Behaviour and Neurosciences, University of Groningen , Groningen , The Netherlands .
Chronobiol Int. 2014 Jul;31(6):749-60. doi: 10.3109/07420528.2014.880451. Epub 2014 Apr 23.
Photoperiodism, the ability to respond to seasonal varying day length with suitable life history changes, is a common trait in organisms that live in temperate regions. In most studied organisms, the circadian system appears to be the basis for photoperiodic time measurement. In insects this is still controversial: while some data indicate that the circadian system is causally involved in photoperiodism, others suggest that it may have a marginal or indirect role. Resonance experiments in the parasitic wasp Nasonia vitripennis have revealed a circadian component in photoperiodic time measurement compatible with a mechanism of internal coincidence where a two components oscillator system obtains information from dawn and dusk, respectively. The identity of this oscillator (or oscillators) is still unclear but possible candidates are the oscillating molecules of the auto-regulatory feedback loops in the heart of the circadian system. Here, we show for the first time the circadian oscillation of period and cryptochrome mRNAs in the heads of Nasonia females kept under short and long photoperiods. Period and cryptochrome mRNA levels display a synchronous oscillation in all conditions tested and persist, albeit with reduced amplitude, during the first day in constant light as well as constant darkness. More importantly, the signal for the period and cryptochrome oscillations is set by the light-on signal. These results, together with phylogenetic analyses, indicate that Nasonia's period and cryptochrome display characteristics of homologous genes in other hymenopteran species.
光周期现象是指生物体能够通过适当的生活史变化来响应季节性变化的日照长度，这是生活在温带地区的生物的一个共同特征。在大多数已研究的生物体中，昼夜节律系统似乎是光周期时间测量的基础。在昆虫中，这一点仍存在争议：虽然一些数据表明昼夜节律系统与光周期现象存在因果关系，但另一些数据则表明它可能只起边缘或间接作用。对寄生黄蜂丽蝇蛹集金小蜂的共振实验揭示了光周期时间测量中的一个昼夜节律成分，这与一种内源性巧合机制相符，即一个由两个成分组成的振荡器系统分别从黎明和黄昏获取信息。这个振荡器（或这些振荡器）的身份仍不清楚，但可能的候选者是昼夜节律系统核心的自调节反馈回路中的振荡分子。在这里，我们首次展示了在短日照和长日照条件下饲养的丽蝇蛹集金小蜂雌虫头部中周期基因（period）和隐花色素基因（cryptochrome）mRNA的昼夜振荡。在所有测试条件下，周期基因和隐花色素基因的mRNA水平都呈现同步振荡，并且在持续光照和持续黑暗的第一天中，尽管振幅减小，但这种振荡仍然持续。更重要的是，周期基因和隐花色素基因振荡的信号是由光照信号设定的。这些结果，连同系统发育分析，表明丽蝇蛹集金小蜂的周期基因和隐花色素基因表现出其他膜翅目物种中同源基因的特征。
