Collaborative Research: Developmental, Molecular and Evolutionary Analysis of Chaetognaths: A Deuterostome-Like Ecdysozoan

[00:23 . 64]毛齿动物，或“箭虫”，是世界上所有海洋中数量最多的海洋无脊椎动物之一。这种无处不在的动物群的系统发育位置目前尚不清楚。直到最近，毛齿动物被认为是基础后口动物，基于它们的发育特征，如它们的径向卵裂程序、典型的肠腔、囊胚的后位和三分体的成体平面。新的分子证据，包括本文提出的Hox基因数据，表明毛齿动物不是后口动物，而是与节肢动物和线虫等外生动物密切相关的基础原口动物。事实上，毛齿动物现在被认为是最关键和研究不足的后生动物群体之一，可以深入了解原始动物身体结构的进化。然而，对毛齿发育的细胞和分子研究很少。Drs。Martindale和Halanych的提议描述了一套全面的、多学科的方法，旨在描述毛齿动物胚胎的“工作”方式。利用现代发育（细胞内细胞谱系标记和激光细胞删除实验）和分子（克隆，原位杂交）技术，Martindale和Halanych将收集这些有趣动物正常发育的重要信息，并能够和检查后生动物遗传调控机制的保护。此外，基因发现技术（EST筛选）将为体表进化的祖先机制提供有价值的新信息。这些数据不仅对确定毛囊动物的系统发育位置很重要，而且还可以为外生动物的进化提供分子和发育方面的见解，以及发育程序的“可进化性”。毛齿纲可能是现有的基础无脊椎动物系统中信息最丰富、最容易处理的，它将使我们了解线虫和节肢动物枝的进化，这两种动物是地球上基因研究最多的动物群体。

0236479HalanychThe chaetognaths, or "arrow worms", are one of the most abundant marine invertebrates found in all the world's seas. The phylogenetic position of this ubiquitous group of animals is currently unknown. Until recently, chaetognaths were considered to be basal deuterostomes based on developmental features such as their radial cleavage program, classic enterocoeley, posterior position of the blastopore, and tripartite adult body plan. New molecular evidence, including Hox gene data presented in this proposal, has suggested that chaetognaths are not deuterostomes but basal protostomes closely allied with ecdysozoans such as arthropods and nematodes. In fact, chaetognaths are now thought to be one of the most pivotal and understudied groups of metazoan animals for gaining insight into the evolution of protostome body plans. Only a handful of cellular and molecular investigations of chaetognath development have ever been made, however. Drs. Martindale and Halanych's proposal describes a comprehensive and multidisciplinary set of approaches designed to characterize how chaetognath embryos "work". Using both modern developmental (intracellular cell lineage labeling and laser cell deletion experiments) and molecular (cloning, in situ hybridization) techniques, Martindale and Halanych will collect vital information on the normal development of these interesting animals, and be able to and examine the conservation of genetic regulatory mechanisms in the Metazoa. In addition, techniques of gene discovery (EST screening) will provide valuable new information on the ancestral mechanisms of body plan evolution. These data will not only be important to determine the phylogenetic position of chaetognaths, but to also provide molecular and developmental insight in to the evolution of the ecdysozoan clade, and the "evolveability" of developmental programs. Chaetognaths could be the most informative and tractable basal invertebrate system available that will allow an understanding of the evolution of the nematode and arthropod clades, the two most genetically heavily studied group of animals on earth.