Construction of BAC Libraries of Metazoans Occupying Key Phylogenetic Positions

基因组DNA的大插入文库是发育进化和遗传学比较研究的宝贵资源，可以解决生物学中基因组如何进化以及基因组进化如何导致身体结构进化的基本问题。本研究的目标是建立代表后生动物宽度的11个BAC库。重点是那些占据系统发育位置的动物，这对理解动物进化至关重要。优先考虑具有证明潜力的生物作为发育模式生物。因此，我们选择了2种后口动物：七鳃鳗和头脊索文文鱼。七鳃鳗是颅类的基础动物，是理解脊椎动物进化过程中基因和染色体复制模式的关键；在分子系统发育的基础上，原造口动物最近被分为两类：外生动物和光生动物。然而，在这些群体中，门的分支模式都没有得到很好的解决。因为有代表性的蜕皮动物、果蝇和隐杆线虫已经被很好地研究过，所以我们没有选择任何蜕皮动物。一般来说，在基因、发育和进化方面很少受到关注的光藻目，已经选择了7种生物。其中包括2种环节动物，其中一种是多毛纲的Platynereis dumerilii，在环节动物中相对较基础，另一种是水蛭Helobdella robusta，衍生程度较高。水蛭正迅速成为一种光栖动物模式发育生物，虽然水蛭是相当衍生的，但它多年来一直是发育遗传学研究的对象。包括两种软体动物——一种双壳动物（Spisula solidissima）和一种腹足动物（ilyanassobsoleta）。其他光板虫包括1只nemertean (Cerebratulus lacteus)， 1只sipunculid（Temiste langiformis）和1只acel flatworm （Neochildea fusca）。在系统发育的位置是有争议的。在形态学的基础上，它们被认为是基侧动物。然而，大多数（但不是全部）分子系统发育分析将孔洞置于原口动物中。为了解决双边起源问题，我们选择了一种栉水母（栉水母）。最后，为了说明后生动物的起源，选择了最具基部后生动物代表的海绵——白垩粘海绵（Callyspongia diffusa）。BAC文库将由P. de Jong（奥克兰儿童医院研究所）建设和分发，他在BAC文库建设方面有着长期的记录，包括为人类基因组计划制作BAC文库。对于对整个基因组测序感兴趣的生物体，建议15X的覆盖范围。对于其他人，建议10倍的覆盖率。

Large-insert libraries of genomic DNA are a valuable resource for comparative studies indevelopment evolution and genetics for addressing such fundamental questions in biology ashow genomes have evolved and how evolution of genomes has resulted in evolution of bodyplans. The goal of the proposed research is to construct 11 BAC libraries representative of thebreadth of the Metazoa. The focus is on animals that occupy phylogenetic positions key to anunderstanding of animal evolution. Preference is given to organisms with demonstrated potentialas developmental model organisms. Therefore, 2 deuterostomes have been chosen: lamprey,basal in the craniates and pivotal for understanding the pattern of gene and chromosomalduplications during vertebrate evolution, and the cephalochordate amphioxus, the closest livinginvertebrate relative of the vertebrates. On the basis of molecular phylogenetics, the protostomeshave recently been divided into two groups, the Ecdysozoa and the Lophotrochozoa. However,branching patterns of the phyla within each of these groups are poorly resolved. Becauserepresentatives of the Ecdysozoa, Drosophila and Caenorhabditis have been well-studied, wehave not chosen any Ecdysozoan. For the Lophotrochozoa, which have, in general, received littleattention in regard to genes, development and evolution, seven organisms have been chosen.These include 2 annelids, one of which, the polychaete Platynereis dumerilii, is relatively basalwithin the annelids and the other of which, the leech Helobdella robusta, is more highly derived.Platynereis is rapidly becoming a lophotrochozoan model developmental organism, and whilethe leech is quite derived, it has been the object of developmental genetic studies for some years.Two molluscs are included-- one bivalve, (Spisula solidissima) and one gastropod (Ilyanassaobsoleta). The other Lophotrochozoans include 1 nemertean (Cerebratulus lacteus), 1 sipunculid(Temiste langiformis), and 1 acoel flatworm (Neochildea fusca). The phylogenetic position ofthe acoels is controversial. On the basis of morphology, they were considered basal Bilateria.However, most, but not all, molecular phylogenetic analyses place acoels within the protostomes.To address bilaterian origins, we have chosen a ctenophore (Mnemiopsis leidyi). Finally, toaddress the origin of the metazoa, a sponge, Callyspongia diffusa, a representative of the mostbasal Metazoa, was selected. BAC libraries will be constructed and distributed by P. de Jong(Children's Hospital Research Institute, Oakland), who has a long track-record in construction ofBAC libraries, including making the BAC library for the human genome project. For organismsfor which interest is high to sequence the entire genome, 15X coverage is proposed. For others,10X coverage is proposed.