Characterizing the molecular and developmental basis of environmental versus genetic trait variation in aphids

 描述（由申请人提供） 表型可塑性影响一系列人类特征，从身高和体重到疾病易感性。然而，环境输入被检测到，然后改变发育程序的机制还没有得到很好的理解，研究这种联系的实验模型是有限的。该项目解决了一个迷人的问题，即环境和遗传变异如何影响替代表型的发展，使用一个创新的模型系统，豌豆蚜虫。这一物种提供了一个无与伦比的机会来研究自然和养育在表型决定中的作用：它表现出显着不同的有翼和无翼的变体，这些变体是由无性繁殖的雌性动物的环境条件和雄性动物中一个单一的未识别的遗传位点引起的。因此，引人注目的是，两个二态性，每一个在不同的控制机制下，存在于这个单一的物种。在这里，我们提出了一个全面的调查的发展和遗传基础的二型，第一次研究的同类，研究计划，建立在广泛的初步数据。在目标1中，我们将确定和表征翅膀多态性位点，以阐明这个单一的基因座如何导致雄性形态的巨大差异。我们的方法包括使用基因组测序进行关联作图，使用qRT-PCR进行跨发育的基因表达水平分析，使用原位杂交在靶向发育阶段进行基因表达空间分析，以及使用CRISPR/Cas9系统进行突变分析。在目标2中，我们将研究翅膀决定的激素基础，以确定环境线索是如何转化为女性的表型差异。我们将测试类固醇激素，蜕皮激素，在这个过程中的作用。我们将测量蜕皮激素滴度水平诱导的母亲（有翼的后代生产者）与未诱导的母亲（无翼的后代生产者），并通过注射蜕皮激素实验操纵其后代表型。此外，我们将通过qRT-PCR在接受或不接受翅膀诱导信号的母亲的胚胎中测量蜕皮激素应答基因的表达水平。在目标3中，我们将研究环境诱导和遗传控制的二态性背后的共享机制的程度，以确定这两种二态性如何在机制层面上相关。我们将通过寻找突变雄性多态性基因对雌性替代变体的影响，并通过qRT-PCR测量有翅和无翅雄性蚜虫中蜕皮激素响应基因的基因表达来解决这个问题。总的来说，这项研究将导致一个模型，环境和遗传因素如何影响相似的替代表型。我们预计，这项工作的一个主要发现将是照明环境信号是如何绕过时，有一个进化过渡到遗传控制的表型变异。

 DESCRIPTION (provided by applicant) Phenotypic plasticity affects an array of human characteristics, from height and weight to disease susceptibility. Yet the mechanisms by which environmental inputs are detected and then alter developmental programs are not well understood, and experimental models for studying this link are limited. This project addresses the fascinating problem of how both the environment and genetic variation influence the development of alternative phenotypes using an innovative model system, the pea aphid. This species offers an unparalleled opportunity to examine the role of nature and nurture in phenotype determination: it exhibits dramatically different winged and wingless morphs that are induced by environmental conditions in asexual females and by a single unidentified genetic locus in males. Thus, strikingly, two dimorphisms, each under different control mechanisms, exist within this single species. Here we propose a comprehensive investigation of the developmental and genetic basis of both dimorphisms, the first study of its kind, with a research plan that builds upon extensive preliminary data. In Aim 1 we will identify and characterize the wing polymorphism locus to illuminate how this single locus can cause dramatic differences in morphology in males. Our methods include association mapping using genome sequencing, gene expression level profiling across development using qRT-PCR, gene expression spatial profiling using in situ hybridization at targeted developmental stages, and mutant analysis using the CRISPR/Cas9 system. In Aim 2, we will study the hormonal basis of wing determination to ascertain how environmental cues are translated into phenotypic differences in females. We will test the role of a steroid hormone, ecdysone, in this process. We will measure ecdysone titer levels in induced mothers (winged offspring producers) versus uninduced mothers (wingless offspring producers), and experimentally manipulate their offspring phenotypes via injection of ecdysone. Further, we will measure expression levels of ecdysone-responsive genes via qRT-PCR in the embryos of mothers receiving or not receiving wing-inducing signals. In Aim 3, we will examine the extent to which there are shared mechanisms underlying the environmentally induced and genetically controlled dimorphisms, to establish how the two dimorphisms are related at the mechanistic level. We will approach this problem by looking for an effect of mutating the male polymorphism gene on the female alternative morphs and by measuring gene expression of ecdysone-responsive genes in winged and wingless male aphids via qRT-PCR. Overall, this research will result in a model of how both environmental and genetic factors influence similar alternative phenotypes. We anticipate that a major finding of this work will be the illumination of how environmental signals are bypassed when there is an evolutionary transition to genetic control of phenotypic variation.