Understanding character polarity in Deep Metazoan phylogeny - Phylogenomics of Myzostomids

了解深部后生动物系统发育中的特征极性 - Myzostomids 的系统发育组学

• 批准号: 5453021
• 负责人: Professor Dr. Ralph Tiedemann, Ph.D.
• 金额: --
• 依托单位: Arbeitsgruppe Evolutionsbiologie / Spezielle Zoologie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2005
• 资助国家: 德国
• 起止时间: 2004-12-31 至 2009-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5453021?language=en
• 关键词: Understanding; character; polarity; Deep; Metazoan

Mainly due to molecular phylogenetic studies, a new view on Deep Metazoan Phylogeny has recently emerged for the protostomia, dividing them into the molting (Ecdysozoa) and the nonmolting protostomes (most often called the Lophotrochozoa). The myzostomids comprise a small group of symbiotic protostomes on echinoderms, which exhibit a body plan with a mosaic of characters typical of annelides and platyzoans. They are parenchymous organisms with parapodia, chaetae, cirri, and an incomplete segmentation. It is therefore not surprising that the taxonomic position of myzostomids has been a matter of controversy since their discovery. Recent molecular analyses based on a few genes have rather complicated than resolved the picture, suggesting close affinities of myzostomids to platyhelminths. In the project proposed here, we aim at clarifying the taxonomic position of myzostomids by a phylogenomic approach: for two model myzostomids (Myzostoma cirriferum, Pulvinomyzostomum pulvinar) libraries of Expressed Sequence Tags (ESTs) will be generated and compared by state-of-the-art bioinformatic tools to potential sister taxa. As the two focus species derive from the two most distantly related phylogenetic lineages within myzostomids, comparison on them will allow relating intra-taxon (within myzostomids) to inter-taxon (among myzostomids and potential sister taxa) gene divergence. For a series of important genes, an in-depth analysis will be performed on a larger series of myzostomid species. These genes have been agreed on among applicants in the SPP Deep Metazoan Phylogeny , such that comparable genomic datasets will be generated for surrogate analysis. Our phylogenomic analysis will be complemented by a comprehensive ultrastructural analysis of myzostomid body plans. While our proximate goal is to resolve the taxonomic position of myzostomids, we ultimately aim at providing evidence for character polarity (plesiomorphic, apomorphic, or convergent) of some of the basic features of protostome body plans, such as parapodia, chaetae, cirri, and segmentation.

由于分子系统发育的研究，最近出现了一种新的关于原口动物深层后生动物系统发育的观点，将它们分为蜕皮（蜕皮动物）和不蜕皮的原口动物（通常称为Lophotrochozoa）。粘口动物是棘皮动物中一小群共生的原口动物，它们的身体结构具有典型的环节动物和平台动物的马赛克特征。它们是具有副足、毛纲、卷毛和不完全分节的实质生物。因此，自myzostomids被发现以来，其分类位置一直存在争议，这并不奇怪。最近基于几个基因的分子分析使问题变得更加复杂，而不是解决问题，这表明myzostomids与platyhelminths有着密切的亲缘关系。在本文提出的项目中，我们的目的是通过系统基因组学方法阐明myzostomids的分类地位：对两种模型myzostomids (Myzostoma cirriferum, Pulvinomyzostomum pulvinar)，将生成表达序列标签（est）文库，并通过最先进的生物信息学工具与潜在的姐妹类群进行比较。由于这两个焦点物种来自于myzostomids中两个最遥远的系统发育谱系，因此对它们进行比较可以将分类群内（myzostomids内部）和分类群间（myzostomids和潜在的姐妹分类群之间）的基因差异联系起来。对于一系列重要的基因，将在更大的myzostomid物种系列上进行深入的分析。这些基因已经在SPP深层后生动物系统发育的申请者中达成一致，这样就可以生成可比较的基因组数据集来进行替代分析。我们的系统基因组分析将由myzostomid body plans的全面超微结构分析来补充。虽然我们的近期目标是解决myzostomids的分类位置，但我们的最终目标是为原石体平面的一些基本特征（如旁足、毛纲、卷状和分节）的特征极性（多形、无形或收敛）提供证据。