Origins and evolutionary consequences of a genetic mechanism for developmental plasticity

环境诱导的变异，或“发育可塑性”，为动物和植物提供了一种至少在某种程度上与环境“匹配”它们的特征的方法。在极端情况下，这种可变性会导致完全不同的替代形式。尽管可塑性在动物和植物中普遍存在，但在基因水平上理解环境如何导致不同性状结果之间的“切换”的例子很少。至于开关的内部遗传机制是如何在进化中产生的，就更不清楚了。此外，由于我们对这些开关所涉及的基因以及这些开关所起的作用的了解有限，这种灵活性对性状的自然选择（在不同条件下采取不同形式）有什么影响还不是很清楚。在这项研究中，太平洋Pristionchus和几个相关的物种——它们对饥饿和本地食物竞争采取不同的喂养形式——将被用来确定基因是如何在进化史上聚集在一起形成一个调节发育可塑性的开关的。一种比较的方法将被用来推断这种开关对基因的影响，以及它最终影响的特征。此外，研究人员还将对本科生、研究生和博士后进行综合遗传学、发育生物学和进化研究方面的培训，并将支持印第安纳大学的两个科学推广项目：(i) PI将在年度暑期项目中主持和指导代表性不足的少数族裔高中生进行自己的研究项目；（ii） PI将帮助印第安纳州高中教师开发和实施项目、实验和活动，作为课堂资源，以提高州生命科学的教学标准。本研究将促进对发育可塑性的功能遗传学理解，特别是对其调控基因和靶基因的理解，并将为理解多表型（即离散发育可塑性）的机制进化和进化意义提供必要的框架。首先，它将描述营养传感如何与多表型开关在线虫模型太平洋Pristionchus。这一目标将通过开关组件的功能测试来实现，特别是从多表型突变体的正向筛选中分离的基因。其次，重建太平洋p.p pacificus及其科（Diplogastridae）其他物种口多表型的综合开关机制的进化史。这一目标将通过比较反向遗传学和转基因实验来实现。第三，它将确定多表型的分子后果及其在双腹线虫中的损失。这一目标将通过对多表型靶基因的分子进化分析来实现。总之，该研究将把多表型遗传学模型整合到以可塑性和次生同化形态为特征的几个谱系的系统发育框架中。具体而言，该研究将建立一个多表型模型，其中包括：(i)其起源的机制要求；（ii）其调控变化的分子能力；（三）其近因（遗传）和最终（进化）结果。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Environmentally induced variability, or 'developmental plasticity', offers a way for animals and plants to "match" their traits, at least to some degree, to their surroundings. In extreme cases, this variability results in disparate, alternative forms. Although plasticity in general is common in animals and plants, very few examples of how environments cause "switches" between alternative trait outcomes are understood at the level of genes. It is even more obscure how the internal genetic machinery for a switch arises in evolution. Furthermore, what consequences this flexibility has for the natural selection of traits, which take different forms under different conditions, are not well understood, due to our limited understanding of the genes involved in the switches and what these switches act on. In this research, the nematode Pristionchus pacificus and several related species - which assume different feeding-forms in response to starvation and local competition for food - will be used to determine how genes have come together in evolutionary history to form a switch that mediates developmental plasticity. A comparative approach will be used infer what effects this switch has had on the genes, and ultimately the traits, it influences. In addition, the investigators will train undergraduate, graduate, and postdoctoral students in research integrating genetics, developmental biology, and evolution, and it will support two science-outreach programs at Indiana University: (i) the PI will host and mentor underrepresented minority high-school students in their own research projects in an annual summer program; (ii) the PI will help Indiana high-school teachers to develop and implement projects, experiments, and activities as classroom resources to improve the teaching and learning of state life science standards.This research will advance a functional genetic understanding of developmental plasticity, specifically of its regulatory and target genes, and it will provide the necessary framework for understanding both the mechanistic evolution and the evolutionary significance of polyphenism, i.e., discrete developmental plasticity. First, it will describe how nutritional sensing interfaces with the polyphenism switch in the nematode model Pristionchus pacificus. This aim will be met by functional tests of switch components, particularly genes isolated from a forward screen for polyphenism mutants. Second, the research will reconstruct the evolutionary history of an integrated switch mechanism for the mouth polyphenism in P. pacificus and other species in its family (Diplogastridae). This aim will be met by comparative reverse genetics and transgenic experiments. Third, it will determine the molecular consequences of polyphenism and its loss across diplogastrid nematodes. This aim will be met by molecular evolutionary analyses of polyphenism target genes. In summary, the research will integrate a model for polyphenism genetics into a phylogenetic framework of several lineages characterized by plastic - and secondarily assimilated morphologies. Specifically, the research will establish a model for polyphenism that encompasses: (i) the mechanistic requirements for its origin; (ii) the molecular capacities for its regulation to change; and (iii) its proximate (genetic) and ultimate (evolutionary) consequences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.