Dissertation Research: Circadian-Clock Genes and Variation in Photoperiodic Time Measurement: a Role for Timeless?

陆地环境中的两个主要循环是每日和季节。 植物和动物使用内部的生物钟来计时它们的日常活动。 许多植物、脊椎动物和昆虫利用一天的长度（光周期）来预测季节的变化，并相应地安排它们的生长、发育、繁殖、开花、冬眠或迁徙的季节性活动。 这项研究关注的是日常活动（昼夜节律）和季节性活动（光周期）之间的分子联系。 影响每日和季节性事件发生时间的最强环境线索是光照。 虽然光输入途径和昼夜节律的分子基础已经很好地理解，但对季节周期调节的分子基础知之甚少。 这项研究使用捕蚊植物，Wyeomyia smithii，通过检查无时间基因的表达和作用，专注于调节日常和季节周期的机制之间的联系，该基因已知对于光线的输入和昆虫和脊椎动物生物钟的中枢功能至关重要。 斯氏怀蝇生活在一个广泛的纬度范围内，随着生长季节的长度在这个范围内变化，用于在活跃的夏季发育和冬季休眠之间转换的白天长度也在变化。 这种对日长反应的差异将用于确定（1）无时间的表达模式如何随起源纬度和日长而变化，以及（2）DNA水平上的多态性如何随起源纬度和日长而变化。 这项研究的独特之处在于，它不仅将评估日常和季节性时间过程之间的联系，而且还将展示在分子水平上，这种联系如何在进化时间内随气候梯度而变化。

The two major cycles in terrestrial environments are daily and seasonal. Plants and animals use an internal circadian clock to time their daily activities. Many plants, vertebrates, and insects use the length of day (photoperiod) to anticipate the changing seasons and to time their seasonal activities of growth, development, reproduction, flowering, hibernation, or migration accordingly. This research is concerned with the molecular connection between the timing of daily activities (circadian rhythmicity) and seasonal activities (photoperiodism). The strongest environmental cue affecting the timing of both daily and seasonal events is light. Whereas the light-input pathway and molecular basis of circadian rhythmicity are well understood, little is known about the molecular basis of the regulation of seasonal cycles. This research uses the pitcher-plant mosquito, Wyeomyia smithii, to focus on the connection between the mechanisms regulating daily and seasonal cycles by examining the expression and role of the timeless gene, a gene known to be essential for the input of light and the central functioning of the circadian clock in insects and vertebrates. Wyeomyia smithii lives over a broad latitudinal range and, as the length of the growing season changes over this range, so also does the day length used to switch between active summer development and winter dormancy. This divergence of response to day length will be used to determine (1) how the expression patterns of timeless vary with latitude of origin and day length and (2) how polymorphism at the level of DNA varies with latitude of origin and day length. This research is unique in that it will be evaluating not only the connection between the daily and seasonal timing processes, but also show how at the molecular level that connection varies over a gradient of climate through evolutionary time.