SGER: A Multi-Gene Approach to Understanding Relationships Among Ciliates in the Class Spirotrichea

DEB-0079325劳拉A. Katz Laura A.卡茨获得了一笔赠款，用于研究一种名为纤毛虫的迷人微生物的进化，纤毛虫是一种多样化的原生动物，其特征是每个细胞中存在两种类型的细胞核，以及染色体的不寻常分子加工。 与许多植物和动物不同，我们目前只有一个基本的框架来解释这些生物的进化历史。 例如，在过去的二十年里，随着物种识别技术的进步，纤毛虫的种类数量从基于显微镜分析的只有三种，增加到基于电子显微镜的八种，再增加到基于DNA序列数据的至少九种。 螺毛纲是一个特别有争议的纤毛虫组合，因为以前的分析提供了不同的图片，其中纤毛虫属于这一类，以及这些纤毛虫是如何相关的。 纤毛虫被认为属于螺毛纲，可以在淡水和海洋生态系统中找到，其特征是其纤毛的多样性，有时是戏剧性的。 我们目前的分类系统是基于有限的数据，只有少数类群。 为了准确地重建纤毛虫之间的亲缘关系，需要从纤毛虫的全面调查中分析多个基因。本研究的主要目的是：（1）鉴定螺毛纲纤毛虫的种类，（2）重建这些种类之间的亲缘关系。 为了实现这些目标，将确定三个基因的DNA序列（小亚基rRNA，α-微管蛋白和DNA聚合酶II的最大亚基）从类螺旋体的潜在成员。 此外，将从适当的外群物种（非旋毛）中表征序列。 将使用至少两种比对方法对所得DNA序列进行比对，并使用几种系统发育方法（例如最大简约法和最大似然法）对单个基因和组合数据集进行物种关系估计。 由此产生的系谱将回答有关旋毛类进化历史的问题，同时也表明了未来研究纤毛虫之间关系的领域。

DEB-0079325Laura A. Katz Dr. Laura A. Katz has been awarded a grant to study the evolution of a fascinating type of microorganisms known as ciliates, a diverse group of protozoa characterized by the presence of two types of nuclei in each cell and by unusual molecular processing of their chromosomes. Unlike many plants and animals, we currently have only a basic framework for interpreting the evolutionary history of these organisms. For example, in the past twenty years, as techniques for identifying species have improved, the number of classes of ciliates has risen from only three based on microscopic analyses, to eight based on electron microscopy, to at least nine based on DNA sequence data. The class Spirotrichea represents a particularly contentious assemblage of ciliates as previous analyses provide varying pictures of which ciliates belong within this class and how these ciliates are related. Ciliates thought to belong to the class Spirotrichea can be found in both freshwater and marine ecosystems, and are characterized by diverse, and sometimes dramatic, arrangements of their ciliature. Our current classification system is based on limited data from only a handful of taxa. Analysis of multiple genes from a comprehensive survey of ciliates is needed to accurately reconstruction relationships among these organisms. The overall goals of this study are (1) to identify species of ciliates that belong to the class Spirotrichea, and (2) to reconstruct relationships among these species. To achieve these goals, DNA sequences will be determined for three genes (small subunit rRNA, alpha-tubulin and the largest subunit of the DNA polymerase II) from potential members of the class Spirotrichea. In addition, sequences will be characterized from appropriate outgroup species (non-spirotrichs). The resulting DNA sequences will be aligned using at least two alignment methods and estimates of species relationships will be made using several phylogenetic methods (e.g. maximum parsimony and maximum likelihood) on both individual genes and a combined data set. The resulting genealogies will answer questions about the evolutionary history of spirotrichs, while also indicating areas for future research on the relationships among ciliates.