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、体重到疾病易感性。然而，环境输入被检测到并随后改变发育计划的机制还没有被很好地理解，研究这种联系的实验模型也是有限的。这个项目利用一种创新的模式系统--豌豆蚜虫，解决了环境和遗传变异如何影响另类表型的发展这一有趣的问题。这个物种提供了一个无与伦比的机会来研究先天和后天在表型决定中的作用：它表现出截然不同的有翼和无翼的形态，这些形态是由无性雌性的环境条件和雄性的单一未知遗传位点诱导的。因此，引人注目的是，在这个单一物种中存在两种二形性，每一种都在不同的控制机制下。在这里，我们建议对这两种二形性的发育和遗传基础进行全面的调查，这是此类研究的第一次，并提出了一项建立在大量初步数据基础上的研究计划。在目标1中，我们将识别和表征翅膀多态基因座，以阐明该单一基因座如何导致雄性动物形态上的显着差异。我们的方法包括使用基因组测序的关联图谱，使用qRT-PCR的发育过程中的基因表达水平图谱，使用目标发育阶段的原位杂交的基因表达空间图谱，以及使用CRISPR/Cas9系统的突变分析。在目标2中，我们将研究翅膀决定的荷尔蒙基础，以确定环境线索如何转化为雌性个体的表型差异。我们将测试一种类固醇激素--蜕皮激素在这一过程中的作用。我们将测量诱导母亲(有翼后代生产者)和未诱导母亲(无翅后代生产者)的蜕皮激素滴度水平，并通过注射蜕皮激素来实验性地操纵它们的后代表型。此外，我们将通过qRT-PCR检测接受或不接受翅膀诱导信号的母亲胚胎中蜕皮激素反应基因的表达水平。在目标3中，我们将研究环境诱导和基因控制的二态现象背后的共同机制的程度，以确定这两种二态现象在机制水平上是如何联系的。我们将通过寻找雄性多态基因突变对雌性变种的影响，以及通过qRT-PCR检测有翼和无翅雄蚜中蜕皮激素反应基因的基因表达来解决这个问题。总体而言，这项研究将产生一个模型，说明环境和遗传因素如何影响相似的可选表型。我们预计，这项工作的一个主要发现将是阐明当存在向表型变异的遗传控制的进化过渡时环境信号是如何被绕过的。

 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.