The evolutionary mechanisms optimizing neural circuit structure and function for skylight navigation across insect species

昆虫是动物王国中最多样化的群体，并提供重要的生态和经济效益。为了成功地狩猎、觅食或散布，大多数自由生活的昆虫依赖于相当大的导航技能，为此它们使用不同的视觉刺激，如天体和天窗偏振。尽管昆虫眼睛的形态多样性很大，但最近的数据显示，它们的视网膜嵌合体在物种之间表现出惊人的相似性。虽然系统的形态学特征已经在几乎所有被分析的昆虫中发现了极化天窗的视网膜探测器，但这些结构的规范及其潜在的神经回路是否实际上是进化保守的，这仍然是未知的。此外，它们的结构（连通性）和功能（计算）如何适应不同昆虫物种的不同生态位是未知的。在本提案中，我们计划测试三个假设：(1)指定极化天窗探测器的分子机制在昆虫中是保守的；(2)转录因子网络的变化使该探测器系统适应物种特异性需求；(3)下游电路元件中特异性表达的基因产物形成进化保守的神经网络。我们将利用现有的果蝇分子遗传学工具，结合不同的生物信息学方法，比较昆虫间的调控序列、转录因子结合位点、转录因子网络和基因表达谱。这些实验将揭示昆虫天窗导航神经回路形成背后的进化保守机制以及物种特异性适应。

Insects are the most diverse group within the animal kingdom and provide both important ecological and economic benefit. For successful hunting, foraging, or dispersal, most free-living insects rely on considerable navigation skills, for which they use different visual stimuli, like celestial bodies and skylight polarization. Despite great morphological diversity of insect eyes, recent data revealed that their retinal mosaics show remarkable similarities across species. While systematic morphological characterization has identified retinal detectors for polarized skylight in virtually all insects analyzed, it remains unknown whether specification of these structures and their underlying neural circuitry are in fact evolutionarily conserved. Moreover, it is unknown how their structure (connectivity) and function (computation) are adapted to the diverse ecological niches of different insect species.In this proposal, we are planning to test three hypotheses:(1) The molecular mechanism for specifying polarized skylight detectors is conserved across insects(2) Variations in the transcription factor network adapt this detector system to species-specific demands(3) Gene products expressed specifically in downstream circuit elements shape evolutionarily conserved neural networks. We will use the molecular genetic tools available in Drosophila in combination with different bioinformatics methods, to compare regulatory sequences, transcription factor binding sites, transcription factor networks, and gene expression profiles across insects. These experiments will reveal evolutionarily conserved mechanisms as well as species-specific adaptations behind the formation of neural circuits for insect skylight navigation.