Seasonal Adaptation of a Circadian Clock

描述（由申请人提供）：本提案的总体目标是了解昼夜节律起搏器如何适应环境温度和白天长度（光周期）的季节性变化而适应新的相位排列。提出具体目标的主要基础是基于我们之前的工作，表明D. melanogaster周期（每）RNA（称为dmpi8； D. melanogaster每内含子8）的3'端内含子的热敏和光敏剪接作为传递日历信息的多模态“季节传感器”。dmpi8在季节性寒冷天气（即低温和短光周期）的高剪接效率提前了“夜间”活动的时间，使果蝇能够在黄昏早来的情况下表现出白天活动的能力。相反，在温暖的日子里，dmpi8的低剪接效率确保了苍蝇在炎热的正午太阳下尽量减少活动，主要是夜间活动，降低了与干燥相关的风险。我们还发现编码磷脂酶C （PLCbeta）的norpA（无受体电位A）基因调节dmpi8剪接效率的温度和时钟控制。这些发现确定了norpA的一种新的非光作用。在这项应用中，我们拟确定温度、光照、时钟因素和NORPA如何共同调节dmpi8的剪接效率，以及这一分子事件对节律性行为的季节适应的贡献。主要目的是鉴定介导dmpi8剪接的热敏性的顺式作用元件，并研究PLC/磷脂酰肌醇信号级联的作用。此外，我们将分析从广泛纬度分离的几种不同果蝇物种的自然种群的生物钟和行为节律。初步研究结果表明，在生物钟适应季节气候的地理变化过程中，每3'端内含子是自然选择的目标。为了实现这一目标，我们提出了包括生化、组织培养和全动物方法在内的多因素实验策略。我们的研究将进一步深入了解时钟功能的季节适应性，并揭示norpA如何参与校准黑腹龙的分子和行为热反应。

DESCRIPTION (provided by applicant): The overall goal of this proposal is to understand how a circadian pacemaker accommodates new phase alignments in response to seasonal changes in ambient temperature and day length (photoperiod). A major foundation for the proposed specific aims is based on our prior work showing that the thermosensitive and photosensitive splicing of the 3'-terminal intron from the D. melanogaster period (per) RNA (termed dmpi8; D. melanogaster dper intron 8) acts as a multi-modal "seasonal sensor" conveying calendar information. High splicing efficiency of dmpi8 on seasonally cold days (i.e., low temperatures and short photoperiods) advances the timing of 'evening' activity, endowing flies with the ability to manifest daytime activity despite the early onset of dusk. Conversely, low splicing efficiency of dmpi8 on warm days ensures that flies minimize activity during the hot midday sun and are mainly nocturnal, lowering the risks associated with desiccation. We also showed that the norpA (no receptor potential A) gene encoding phospholipase C (PLCbeta), modulates the temperature and clock control of dmpi8 splicing efficiency. These findings identified a novel non-photic role for norpA. In this application we propose to determine how temperature, light, clock factors and NORPA co-regulate the splicing efficiency of dmpi8, and the contribution of this molecular event to seasonal adaptation in rhythmic behavior. Major objectives are to identify cis-acting elements that mediate thermosensitivity of dmpi8 splicing and investigate the role of the PLC/phosphatidylinositol signaling cascade. Moreover, we will analyze the clockworks and behavioral rhythms in natural populations of several different Drosophila species isolated from a wide range of latitudes. Preliminary findings suggest that per 3'-terminal introns are targets for natural selection in the adaptation of circadian clocks to geographical variations in seasonal climates. To accomplish these goals we propose to take multifacted experimental strategies including biochemical, tissue culture and whole animal approaches. Our studies will add insights into seasonal adaptation of clock function and reveal how norpA participates in calibrating molecular and behavioral thermoresponses in D. melanogaster.