Chronobiology Laboratory, Evolutionary and Organismal Biology Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, PO Box 6436, Jakkur, Bangalore, Karnataka 560064, India.
J Exp Biol. 2012 Sep 1;215(Pt 17):2960-8. doi: 10.1242/jeb.071290.
Adult emergence (eclosion) of fruit flies Drosophila melanogaster under constant laboratory conditions follows a circadian pattern with bouts of eclosion recurring at approximately 24 h intervals. Under periodic light:dark (LD) cycles, adults emerge only during a specific time of the day followed by little or no emergence for the rest of the day. This phenomenon is therefore equated to a gate of emergence that, when open, allows adults to emerge and when closed, no emergence takes place. In this study, we attempt to understand the mechanism underlying adult emergence rhythm in D. melanogaster using a model based on interplay between developmental and circadian clock systems. The model is composed of an oscillatory threshold of a substance that builds up during pre-adult development. Computer simulations based on this model enabled us to make specific predictions about the 'gate width' of the adult emergence rhythm under conditions of fast/slow pre-adult development and short/long circadian periods, which we subsequently tested empirically. The main predictions from the simulations are: (1) flies with faster development have greater gate width and vice versa, and (2) flies with faster circadian clocks have shorter gate width and vice versa. To empirically validate these predictions, we carried out experiments on D. melanogaster populations known to have fast/slow pre-adult development, short/long circadian periods and narrow/wide gate width. Additionally, we manipulated the rate of pre-adult development of the above flies by increasing/decreasing ambient temperature to further examine the influence of developmental rates on gate width of adult emergence rhythm by a complementary approach. The results show that gate width is greatly influenced by the duration of pre-adult development and the length of circadian cycles. This suggests that the adult emergence rhythm of D. melanogaster may be based on mechanisms involving oscillatory threshold and build-up of a developmental substance.
在恒定的实验室条件下，成年果蝇的成虫出现（羽化）遵循昼夜节律模式，每隔大约 24 小时出现一次羽化高峰期。在周期性的光照：黑暗（LD）循环下，成虫仅在一天中的特定时间出现，其余时间几乎没有成虫出现。因此，这种现象被等同于成虫出现的门控，当门打开时，允许成虫出现，当门关闭时，成虫不会出现。在这项研究中，我们试图使用基于发育和昼夜节律系统相互作用的模型来理解 D. melanogaster 中成年出现节律的机制。该模型由在成虫前发育过程中积累的物质的振荡阈值组成。基于该模型的计算机模拟使我们能够对快速/慢速成虫前发育和短/长昼夜周期条件下的成虫出现节律的“门宽”做出具体预测，随后我们通过实验进行了验证。模拟的主要预测结果是：（1）发育较快的果蝇具有更大的门宽，反之亦然，（2）昼夜节律较快的果蝇具有较短的门宽，反之亦然。为了验证这些预测，我们对具有快速/慢速成虫前发育、短/长昼夜周期和窄/宽门宽的已知 D. melanogaster 种群进行了实验。此外，我们通过增加/减少环境温度来操纵上述果蝇的成虫前发育速度，以通过互补方法进一步研究发育速度对成虫出现节律门宽的影响。结果表明，门宽受成虫前发育持续时间和昼夜周期长度的影响很大。这表明 D. melanogaster 的成虫出现节律可能基于涉及振荡阈值和发育物质积累的机制。
