RUI: Specification and Evolution of Reproductive Fate in the Pea Aphid

进化允许生物体通过基因突变和自然选择在许多代中适应它们的环境。此外，一些生物可以在一代人的时间内适应环境的变化，而不会改变它们的基因。当环境影响生物体如何发育时，这种“发育可塑性”就会发生，并允许生物体比通过进化变化更快地适应环境挑战。可塑性本身是通过更长的突变和选择过程进化而来的，但人们对这种进化知之甚少。这个项目的重点是蚜虫，一种在夏季进行无性繁殖并产活的小昆虫。然而，夏季的形式无法在寒冷的冬天生存。在秋天，当蚜虫母亲感觉到白天越来越短时，它们就会用化学方法向它们的胚胎后代发出信号，让它们发育成一种能够产卵的形态，这种形态可以在冬天的寒冷中存活下来，并在春天孵化。该项目的参与者将研究蚜虫胚胎从夏季形态转变为秋季形态时发生的分子变化。参与者还将调查来自暖冬地区的蚜虫，这些地区不再产生秋季形态，也不产卵，以试图了解在最近的进化过程中，对较短的白天的反应是如何消失的。这项工作将主要在布林莫尔学院（Bryn Mawr College）进行，这是一所女子本科院校，因此也旨在让年轻女性参与到进化发育生物学学科中假设驱动实验和数据分析的设计和执行中来。蚜虫的生殖多表型是自然种群遗传调节的一个重要例子，其中关于可塑性的发育和内分泌基础已经有了很多了解。然而，要取得这样的进展，就需要对该系统的基本原理有准确的了解。虽然有几条线索的证据表明，少年激素参与了光周期反应，但这种激素在调节效果中所起的确切作用尚不清楚。结合激素操作、幼年激素滴度测量和基因表达的早期规范以及随后分化为夏季和秋季形式的方法，将区分幼年激素在这一过程中所起作用的相互竞争的假设。如果实验成功，将证明幼激素在生殖命运规范中的胚胎作用，并确定这种分化的其他早期标记，为理解这种转换及其如何进化以适应新环境提供候选对象，并打开新的大门。

Evolution allows organisms to adapt to their environments over many generations via genetic mutation and natural selection. In addition, some organisms can adapt to changes in their environments within just one generation without any change in their genes. Such "developmental plasticity" occurs when the environment influences how organisms develop, and allows organisms to adapt to environmental challenges more rapidly than is possible through evolutionary change. Plasticity itself has evolved through the longer process of mutation and selection, but little is known about this evolution. This project focuses on aphids, small insects that reproduce clonally and give live birth during the summer months. The summer form, however, cannot survive a cold winter. In the fall, when mother aphids sense that days are getting shorter, they chemically signal their embryonic offspring to develop into a form that can lay eggs that can survive the cold temperatures of winter and hatch in the spring. The participants in this project will investigate the molecular changes that occur in developing aphid embryos when they switch from the summer to the fall form. Participants will also investigate aphids from regions with mild winters that no longer produce the fall form and do not lay eggs, to try to understand how the response to shorter days has been lost over the course of recent evolution. The work will take place primarily at Bryn Mawr College, a women's undergraduate institution, and thus also aims to engage young women in the design and execution of hypothesis-driven experimentation and data analysis within the discipline of evolutionary developmental biology.The aphid reproductive polyphenism is poised to become an important example of genetic accommodation in natural populations, one for which a good deal is known about the developmental and endocrine basis of the plasticity. Such progress, however, will require an accurate understanding of the fundamentals of the system. Although several lines of evidence suggest that juvenile hormone is involved in the photoperiod response, the precise role this hormone plays in mediating the effect is not clear. A combined approach of hormone manipulation, measurements of juvenile hormone titer, and gene expression during early specification and subsequent differentiation into the summer and fall forms will discriminate among competing hypotheses for the role that juvenile hormone plays in the process. If successful, the experiments could demonstrate an embryonic role for juvenile hormone in the specification of reproductive fate and identify other early markers of this differentiation, providing candidates and opening new doors toward understanding the switch and how it evolves to accommodate novel environments.