The Formation and Evolution of the Metameric Body Plan in Basal Annelids

[00:49 . 25]关于后生动物进化中节段体平面的起源存在相当大的争论。有观点认为原口-后口动物的祖先已经有节段，而另一些人则认为节段是在节段生物的三个主要分支中独立进化的：环节动物、节肢动物和脊索动物。虽然人们对节肢动物和脊索动物的发展了解很多，但对环节动物的发展几乎一无所知。仅有的一点细胞和分子信息几乎全部来自于水蛭，这是一种高度衍生的淡水链状环节动物。海洋多毛动物是基生环节动物中种类最多、种类最多的一类动物，是研究环节动物节段发育进化的重要类群，但目前尚未有关于多毛动物胚胎的细胞内命运图谱发表。这一建议描述了一个全面的和综合的细胞和分子解剖的起源和多毛类节段体计划的发展。研究人员将研究具有不同生活史特征的三种多毛动物，而不是专注于单一的多毛动物物种，以获得对这一动物群体内机制多样性的认识。现代细胞谱系分析将与两种不同模式途径的分子研究相结合，形成一个节段体平面，并将该体平面多样化到不同的区域。特定目标#1：利用细胞谱系技术跟踪具有不同生活史的三种多毛动物的胚胎和幼虫节段组织起源。具体目标#2：研究三种多毛类胚胎和幼虫中嵌入、犰狳、甚至跳过、矮胖和毛茸茸的分割基因的时空分布。具体目标#3：完成我们之前分离的Hox基因在异交物种Chaetopterus中的表达研究，并对比Hox基因在两种同源多毛动物（Capitella和Hydroides）中的分布。提出的工作将提供关于如何在环节动物的基础群体中产生分段身体计划的关键信息。在与其他后生动物门进行任何种类的分段同源性比较之前，这个信息是至关重要的。

0094925MartindaleThere is considerable debate about the origin of segmental body plans in metazoan evolution. Arguments have been made that the protostome-deuterostome ancestor was already segmented, while others argue that segmentation evolved independantly in the three major clades of segmented organisms: the annelids, arthropods, and chordates. While there is alot known about the development of some arthropods and chordates, virtually nothing is known about the development of annelids. The little cellular and molecular information available comes almost exclusively from a few species of the highly derived group of freshwater clitellate annelids, the leeches. The marine polychaetes are the most diverse and speciose group of basal annelids and are clearly a critical group to study when considering the evolution of segmental development in the annelids, yet not a single intracellular fate map has been published on any polychaete embryo. This proposal describes a comprehensive and integrative cellular and molecular dissection of the origins and development of the segmental body plan in polychaetes. Rather than focusing on a single polychaete species, the investigators will examine three species of polychaetes with different life history characteristics to gain an appreciation for the diversity of mechanisms within this group of animals. Modern cell lineage analysis will be utilized in conjunction with molecular studies of two distinct patterning pathways, the formation of a segmental body plan, and the diversification of that body plan into distinct regions. Specific Aim #1: Utilize cell lineage techniques to follow the embryonic and larval origins of segmental tissues in three species of polychaetes with distinct life histories. Specific Aim #2: Examine the spatio-temporal deployment of the segmentation genes engrailed, armadillo, even-skipped, runt, and hairy in three species of polychaete embryos and larvae. Specific Aim #3: Complete the expression studies with our previously isolated Hox genes in the heteronomous species Chaetopterus and contrast the deployment of Hox genes with two species of homonomous polychaetes (Capitella and Hydroides). The proposed work will provide critical information about how the segmented body plan is generated in a basal group of annelids. This information is crucial before any kind of comparison about the homology of segmentation can be made with other metazoan phyla.