Sabre and Environmentally Responsive Cell Expansion

埃蒙斯这个项目的目的是阐明一种形态新颖性进化的分子遗传学基础。待研究的生物是与模式遗传生物秀丽隐杆线虫有关的自由生活土壤线虫。在以前的工作中，已经表明了一种新的形态特征的雄性交配结构已经出现在进化的属Caenorhabditis。对秀丽隐杆线虫的遗传研究表明，这一特征的形成涉及几个在形态发生途径中起作用的基因。该途径的一个基因是转录因子Pax-6的线虫同源基因。Pax-6存在于许多多细胞生物中，从昆虫到脊椎动物，它被认为在中枢神经系统的形成以及眼睛的发育中起着至关重要的作用。Pax-6位点的进化变化在线虫新形态特征出现中的作用将被研究。将确定几个物种的细胞系，并与秀丽隐杆线虫的细胞系进行比较，以确定细胞系的变化在形态进化中所起的作用。一个非隐杆线虫物种的Pax-6同源基因将被分离、测序，并与秀丽隐杆线虫的基因进行比较。目的是确定影响形态的遗传变化是否发生在Pax-6的上游，Pax-6的启动子，Pax-6的蛋白质编码区，或Pax-6的下游。如果秀丽隐杆线虫和第二个物种的基因在氨基酸序列上是相同的，并且在相同的细胞中表达，那么进化变化一定影响了下游功能。如果这两个基因不相同，那么由两个物种的基因构建的一系列杂交基因将在秀丽隐杆线虫和第二个物种中进行测试。埃蒙斯博士希望通过详细识别导致形态变化的发育基因的遗传变化，帮助阐明形态发生的遗传决定因素，以及导致形态进化的遗传变化的本质。这项研究的结果应该有助于回答关于进化机制的几个悬而未决的问题。＊＊＊

9506308 Emmons The aim of this project is to elucidate the molecular genetic basis for the evolution of a morphological novelty. The organisms to be studied are free living soil nematodes related to the model genetic organism Caenorhabditis elegans. In previous work it has been shown that a novel morphological feature of the male copulatory structure has appeared during evolution of the genus Caenorhabditis. Genetic studies in C. elegans have revealed that development of this feature involves several genes acting in a morphogenetic pathway. One gene of this pathway is the nematode homolog of the transcription factor Pax-6. Pax-6 is found in many multicellular organisms, from insects to vertebrates, and is thought to play an essential role in patterning the central nervous system, as well as in the development of the eye. The role of evolutionary change at the Pax-6 locus in the appearance of the novel morphological feature of nematodes will be investigated. Cell lineages will be determined for several species and compared to those of C. elegans to determine what role change in cell lineage has played in evolution of morphology. The Pax-6 homolog of one non- Caenorhabditis species will be isolated, sequenced, and compared to the gene of C. elegans. The aim is to determine whether genetic changes affecting morphology have occurred upstream of Pax-6, in the promoter of Pax-6, in the protein coding region of Pax-6, or downstream of Pax-6. If the genes of C. elegans and the second species are identical in amino acid sequence and are expressed in the same cells, then evolutionary change must have affected downstream functions. If the two genes are not identical, then a series of hybrid genes constructed from the genes of the two species will be tested in C. elegans and in the second species. By identifying in detail the genetic changes in a developmental gene that have given rise to changes in morphology, Dr. Emmons hopes to help elucidate both the genetic determi nants of morphogenesis, and the nature of the genetic changes that result in evolution of morphology. The results of this study should contribute towards answering several outstanding questions concerning the mechanism of evolution. ***