The Non-vertebrate Chordate Oikopleura and Evolution of Vertebrate Developmental Innovations

非脊椎动物脊索动物 Oikopleura 和脊椎动物发育创新的进化

• 批准号: 0345203
• 负责人: John Postlethwait
• 金额: $ 42万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0345203&HistoricalAwards=false
• 关键词: Non; vertebrate; Chordate; Oikopleura; Evolution

NSF0345203 The Non-vertebrate Chordate Oikopleura and Evolution of Vertebrate Developmental InnovationsDevelopmental innovations transformed ancient filter-feeding chordates into voracious predators, the ancestors of the vertebrates. These innovations are proposed to include a three-part brain, neural crest, and epidermal placodes, and to be associated with extensive genome amplification. A central problem is an understanding of the molecular genetic changes that permitted the evolution of new developmental mechanisms responsible for the vertebrate bauplan. In addition to the Vertebrata (or Craniata), the phylum Chordata contains two other sub-phyla, Cephalochordata (the sister group to the Vertebrata), and the basally diverging Urochordata. Urochordate larvae have a typical chordate morphology including notochord, dorsal nerve cord, pharyngeal slit primordia, and a muscular post-anal tail. Urochordates of the class Ascidiacea are well studied classically, molecularly, and genomically, but their larvae usually lack a complete one-way digestive system, and metamorphosis destroys much of the central nervous system as the body plan reorganizes into a sessile, filter-feeding adult. In contrast, urochordates of the class Larvacea (or Appendicularia), including Oikopleura dioica, maintain a complete chordate body plan as free-living adults, which may be an advantage for the investigation of the chordate bauplan. Furthermore, in contrast to cephalochordates, Oikopleura embryos are available year round and can be maintained many generations in the lab. The overall objective of this proposal is to help understand the evolutionary origin of vertebrate developmental innovations utilizing Oikopleura dioica to complement investigations on ascidians and cephalochordates. Intellectual Merit Objectives: Aim 1. To determine the fate map of Oikopleura embryos. Understanding the fate map is essential for investigations of cell fate determination. Methods include injection of fluorescent dyes into blastomeres at various ages, and four-dimensional reconstructions in multi-photon confocal microscopy. Aim 2. To test in Oikopleura the developmental role of orthologs of genes shown to be required for the development of vertebrate neural crest and placodes. Methods for Aim 2 include down-regulating gene function with morpholino antisense oligonucleotides, and testing gene function by transient transgenesis. Broader Impact Objectives: Aim 3. To train two minority undergraduates studying Oikopleura molecular developmental genetics in a ten-week summer research program, and one minority undergraduate for academic year research. Aim 4. To increase knowledge of the basic biology of a major player in global carbon sequestration. Larvaceans bypass most of the microbial food web by converting picophytoplankton into biomass directly available to predatory fish and into fast-sinking carbon trapped in their discarded houses that are transported to ocean depths. In the face of global warming, likely due at least in part to rising atmospheric carbon dioxide, it is crucial to understand better the biology of this key global link in the carbon cycle.

NSF0345203非脊椎动物脊索动物与脊椎动物的进化发展创新将古老的滤食性脊索动物转变为贪婪的捕食者，脊椎动物的祖先。这些创新被提议包括一个由三部分组成的脑、神经脊和表皮安慰剂，并与广泛的基因组扩增有关。一个中心问题是对分子遗传变化的理解，这些变化允许进化出导致脊椎动物鲍普兰的新的发育机制。除了脊椎动物(或称头盖动物)外，脊索动物门还包括另外两个亚门，Cephalchordata(脊椎动物的姐妹群)和基本发散的尾索动物。尾索幼虫具有典型的脊索形态，包括脊索、背侧神经索、咽裂原基和一条肌肉发达的肛后尾巴。海鞘纲的尾索动物在经典、分子和基因组学上都得到了很好的研究，但它们的幼虫通常缺乏完整的单向消化系统，随着身体计划重组为无柄、滤食性成虫，变态破坏了中枢神经系统的大部分。相比之下，幼虫纲(或附肢纲)的尾索动物，包括Oikopleura dioica，作为自由生活的成年动物，保持着完整的脊索体计划，这可能是研究脊索动物的一个优势。此外，与头壳动物不同的是，Oikopleura的胚胎全年可用，并可以在实验室中保持许多世代。这项建议的总体目标是帮助理解脊椎动物发展创新的进化起源，利用Oikopleura dioica补充对海鞘和头颈类动物的研究。智力价值目标：目的1.确定Oikopleura胚胎的命运图谱。了解细胞命运图是研究细胞命运决定的基础。方法包括在不同年龄的卵裂球内注射荧光染料，以及在多光子共聚焦显微镜下进行四维重建。目的2.在Oikopleura中测试脊椎动物神经脊和安慰剂发育所需基因的同源基因的发育作用。目的2的方法包括用吗啡反义寡核苷酸下调基因功能，并通过瞬时转基因检测基因功能。更广泛的影响目标：目标3。在为期十周的暑期研究计划中，培养两名学习Oikopleura分子发育遗传学的少数民族本科生，以及一名少数民族本科生进行学年研究。目标4.增加对全球碳固存主要参与者的基础生物学知识。幼虫通过将浮游微藻转化为直接供捕食性鱼类使用的生物量，以及转化为困在被运送到海洋深处的废弃房屋中的快速下沉的碳，绕过了大多数微生物食物链。面对全球变暖，至少部分原因可能是大气中二氧化碳的增加，更好地理解碳循环中这一关键全球环节的生物学意义至关重要。