The Role of Developmental Genes in Controlling Butterfly Eyespot Patterns

Evo-DEVO的新兴领域试图通过研究基因的可变性及其控制的发育路径，部分地了解塑造了基因如何转化为表型的进化过程。蝴蝶翅膀上丰富多彩的功能图案为Evo-DEVO研究提供了理想的材料，因为1)它们在所描述的12,000个物种内和之间都是可变的，2)它们代表着视觉上引人注目的选择产品，通常具有已知的适应价值，3)因为发生图案形成的二维表皮翅膀表面非常容易受到发育、分子和表型特征的影响。若虫体内最常见的图案元素是眼点：不同颜色鳞片的明显同心环。眼点被认为是模仿脊椎动物眼睛的外观，可以惊吓攻击的捕食者，或者将攻击转向翅膀的边缘。最近的研究表明，三种转录因子Spalt，Sal，Engrailed，En和Distal-less，Dll，在羽化过程中的视斑区表达。SAL和DLL在眼点中央盘中表达，黑色鳞片在那里分化，而EN在中央盘周围的环状细胞中表达，与成虫翅膀上金色鳞片的图案相关。此外，在B.anynana的一个突变体“金眼”中，SAL不存在于细胞的中央圆盘中，而EN在整个眼斑中表达，成虫的图案由一个完全金色的眼斑组成。这项提案中概述的实验将测试SAL和DLL以及EN是否分别在区分眼点的黑色和金色鳞片时存在因果关系。将开发B.anynana的种系转化技术，以测试这些基因是否在功能上被增选，以指定进化中的新模式。还将尝试开发一种热休克促进系统，可以在发育过程中的特定时间激活这些转基因。候选基因的功能将通过在眼斑区异地表达它们，并测试它们在指定有色鳞片命运方面的功能和充分性来确定。如果如预期的那样，在转录因子和有色鳞片的分化之间建立了因果关系，那么最终的目标将是剖析这些基因的调节区的进化，跨越B.anynana内选定的品系，跨越具有不同眼斑形态的密切相关物种，并最终跨有和没有眼斑的物种，以了解DNA序列变异和形态进化之间的关系。优点标准一：EVO-DEVO的许多工作主要是对不同物种发育所涉及的遗传途径的描述，有时来自不同的门。尽管比较研究能够而且已经产生了丰硕的成果，但不应忽视种内和密切相关物种之间的变异研究。事实上，适应性进化主要涉及通过自然选择对存在于同一种群的个体中的表型变异进行分类，而不是存在于不同物种的个体中。重要的是要了解这种种内变异的产生，以及通过比较鳞翅目一组发育基因的进化来理解基因共同选择的可能更“救赎”的机制。这些目标可以通过解剖调控基因的进化来实现，这些基因在区分适应性特征方面发挥着关键作用。这个项目的目的是测试几个候选基因是否显示出这种关键作用。优点标准II：蒙泰罗博士是一名新教师，目前培养两名本科生和两名女性研究生，其中一人是俄克拉何马州乔克托部落的美国原住民。这位优秀且非常有前途的研究生已经开始了这里描述的项目。蒙泰罗博士将继续对研究生和本科生进行人口遗传学、系统遗传学和发育生物学方面的培训，不分性别和种族，以便为他们提供广泛的、多方面的进化和发展方法。此外，这个项目有一个跨学科的部分，研究生将与物理系的成员一起工作，并在该系参加适当的研究生课程。

0316283MonteiroThe emerging field of evo-devo seeks to understand the evolutionary processes that have shaped how genotype translates into phenotype, in part by studying variability in genes and the developmental pathways that they control. The colorful and functional patterns on the wings of butterflies provide ideal material for evo-devo research because 1) they are variable both within and across the 12,000 described species, 2) because they represent visually compelling products of selection, often with a known adaptive value, and 3) because the two-dimensional epidermal wing surfaces, where pattern formation takes place, are very amenable to developmental, molecular, and phenotypic characterization. Among the most common pattern elements within the nymphalids are the eyespots: distinct concentric rings of differently colored scales. Eyespots are thought to mimic the appearance of vertebrate eyes, and can either startle an attacking predator or deflect the attack towards the margin of the wing. Recently it was shown that three transcription factors, Spalt, Sal;, Engrailed, En; and Distal-less, Dll, are expressed in the eyespot field of Bicyclus anynana during the pupal wing stage. Sal and Dll are expressed in a central disc of the eyespot, where black scales differentiate, while En is present in a ring of cells around the central disc, correlating to the pattern of gold scales in the adult wing. Additionally, in a mutant line of B. anynana, "Goldeneye," Sal is absent from the central disc of cells, while En is expressed in the whole eyespot field, and the adult pattern consists of an entirely gold eyespot. The experiments outlined in this proposal will test whether there is a causal involvement of Sal and Dll, on the one hand, and En, on the other hand, in differentiating the black and gold colored scales of an eyespot, respectively. The technique of germ line transformation in B. anynana will be developed in order to test whether these genes have been functionally co-opted to specify novel patterns in evolution. Development of a heat-shock promoter system that can activate these transgenes at specific times during development will also be attempted. The function of the candidate genes will be determined by ectopically expressing them in the eyespot field and testing their function and sufficiency in specifying the fate of the colored scales. If, as expected, a causal relationship is established between the transcription factors and differentiation of the colored scales, the ultimate goal will be to dissect the evolution of the regulatory regions of these genes across selected lines within B. anynana, across closely related species with divergent eyespot morphologies, and ultimately across species with and without eyespots in order to understand the relationship between DNA sequence variation and morphological evolution. Merit Criteria I: Much work in evo-devo has been dominated by the characterization of the genetic pathways involved in the development of different species, often times from different phyla. Although comparative studies can, and have, generated fruitful results, studies of variation at the intra-specific level and among closely related species should not be neglected. Indeed, adaptive evolution primarily involves the sorting by natural selection of phenotypic variants present in individuals of the same population, not in individuals of different species. It is important to understand the generation of such intra-specific variation, as well as the possibly more "saltational" mechanisms of gene co-option by comparing the evolution of a set of developmental genes across the Lepidoptera. These aims can be achieved by dissecting the evolution of regulatory genes with a demonstrated key role in differentiating adaptive traits. This project aims to test whether a few candidate genes display that key role. Merit Criteria II: Dr. Monteiro is a new faculty member currently training 2 undergraduate students and two female graduate students, one of which a member of the Native American tribe Choctaw Nation of Oklahoma. This excellent and very promising graduate student has already begun working on the project described here. Dr. Monteiro will continue to train graduate and undergraduates students alike in Population Genetics, Phylogenetics, and Developmental Biology, irrespective of gender and ethnicity, in order to provide them with a broad multifaceted approach to Evolution and Development. In addition, this project has a cross-disciplinary component where graduate students will be working with members of the Physics department and taking appropriate graduate courses in that Department as well.