The evolution of a co-opted gene-regulatory network underlying a rapidly evolving morphological trait

 描述（由申请人提供） 本研究的目的是剖析快速进化的复杂性状背后的致病基因和突变，并了解这种性状进化的约束性质。这样的奋进需要一个实验系统，在这个系统中，物种在很短的进化时间内发生剧烈的变化，这些变化可以很容易地被遗传操纵。黑腹果蝇（Drosophilamelanogaster）种群的后叶是最近发现的雄性生殖器的重要结构特征。在过去的200万年里，这一组的四个物种中的每一个的结构都进化出了惊人的不同形态。我们的初步工作已经记录了一个高度保守的基因调控网络（GRN）编码的幼虫后气门在成人后叶创造新的表型变异的明显的共同选择和重新部署。这一发现刺激我们假设机制，将允许快速进化的叶改变，而留下的气孔结构不变。在这个GRN的成员中有一个基因pox neuro（poxn），我们已经证明它在D. simulans相对于D. melanogaster和D. melanogaster导致叶增大，如在D. simulans。此外，我们已经证明，在D. simulans是由基因内所含的后叶特异性增强子的序列分歧引起的。使用群体遗传学方法来检测自然选择，我们已经确定了一个选择的签名，与后叶增强子的poxn。在这里，我们建议采用基因组学（即RNA-seq，群体基因组学）和分子遗传学技术（即转基因表达和互补测定），以确定其他致病基因和突变，负责不同物种之间的后叶大小和形状的差异。黑腹物种组（目的1和2）。有了大量这样的分子变化，我们将研究后叶的增选节点是如何在不改变气门结构的情况下在其叶功能中分化的（目的3）。

 DESCRIPTION (provided by applicant) The goal of this research is to dissect the causative genes and mutations underlying a rapidly evolving complex trait and to understand the nature of constraints on the evolution of this trait. Such an endeavor requires an experimental system in which drastic changes occur over short evolutionary timeframes in species that can be easily manipulated genetically. The posterior lobe in the Drosophila melanogaster species group is a recently-derived structural feature of male genitalia important in mating. The structure has evolved strikingly different morphology in each of the four species of this group over the past two million years. Our preliminary work has documented the apparent co-option and re-deployment of a highly conserved gene regulatory network (GRN) encoding the larval posterior spiracle in creating novel phenotypic variation in the adult posterior lobe. This finding stimulates us to hypothesize mechanisms that would allow the rapidly evolving lobe to change while leaving the spiracle structure unaltered. Among the members of this GRN is the gene pox neuro (poxn) which we have shown is divergently upregulated in D. simulans relative to D. melanogaster and that over-expression in D. melanogaster leads to enlargement of the lobe as observed in D. simulans. Additionally, we have shown that the upregulation of poxn in D. simulans is caused by sequence divergence in a posterior lobe-specific enhancer contained within the gene. Using a population genetic method to detect natural selection, we have identified a signature of selection that coincides with the posterior lobe enhancer of poxn. Here, we propose to employ genomic (i.e. RNA-seq, population genomics) and molecular genetic techniques (i.e. transgenic expression and complementation assays) to identify other causative genes and mutations responsible for differences in posterior lobe size and shape among species of the D. melanogaster species group (Aims 1 and 2). With a large collection of such molecular changes in hand, we will examine how co-opted nodes of the posterior lobe have diverged in their lobe functions without altering the spiracle structure (Aim 3).