Collaborative Research: Molecular Genetic Studies of Bdelloid Rotifers

该项目的目标是发现和描述遗传和生态因素，这些因素允许一组无脊椎动物蛭形轮虫在没有有性生殖的情况下成功进化数千万年，尽管其他停止有性生殖的后生动物物种几乎总是遭受早期灭绝。具体而言，该项目将（1）确定蛭形虫种群内转移的DNA片段的长度和年龄分布。虽然蛭形类几乎肯定不进行有性生殖，但最近在天然蛭形类种群中发现的同源DNA转移似乎代表了一种新的混合形式，其遗传和进化意义尚不清楚。(2)通过在携带选择标记的DNA存在下筛选干燥和再水化后的蛭形生物，确定蛭形生物的不寻常的干燥/再水化循环是否可以介导基因向蛭形生物基因组的水平转移。在这种条件下发生的基因整合将构成一种遗传转移的形式，以前未知的自然发生在后生动物，如果同源的，是可能占最近证明的等位基因共享蛭形虫种群和异位纳入外源基因。(3)更充分地表征大量的水平转移和异位纳入外来（包括细菌，真菌和植物）的基因发生在蛭类通过检查转录的基因的几种轮虫，以确定的性质，来源，和可能的功能基因水平转移从远亲类群。更广泛的影响：为什么有性生殖存在，为什么它应该采取两个父母，而不是一个产生后代，是基本的生物学重要性的问题，也是公众利益，并提供了一个极好的机会，在生物学的公共教育。在早期NSF支持下，该项目的结果在美国和国际媒体上得到了广泛的报道，并已被纳入大学生物学课程，生物学教科书以及生物学和进化方面的流行书籍。 该项目将培养两名博士后科学家，一名博士。学生和四个本科生。 该项目产生的超过30 Mb的蛭形蛋白cDNA序列将保存在GenBank中，并将在具有图形界面的网站上提供，用于检查读取质量、组装覆盖率、ORF鉴定和注释;用于使用BLAST或使用关键字的蛭形蛋白注释搜索蛭形蛋白序列;以及用于下载数据、BLAST搜索结果等。

The goal of this project is to discover and characterize the genetic and ecological factors that have allowed a group of invertebrate animals, bdelloid rotifers, to evolve successfully for tens of millions of years without sexual reproduction although other metazoan species that cease reproducing sexually almost invariably suffer early extinction. Specifically, the project will (1) Determine the length and age distribution of DNA segments transferred within bdelloid populations. Although bdelloids almost certainly do not engage in sexual reproduction, the recent demonstration of homologous DNA transfer in natural bdelloid populations appears to represent a novel form of mixis, the genetic and evolutionary implications of which are as yet unknown. (2) Determine whether the unusual desiccation/rehydration cycle of bdelloids can mediate horizontal transfer of genes to bdelloid genomes by screening bdelloids after desiccation and rehydration in the presence of DNA carrying a selectable marker. The occurrence of gene integration under such conditions would constitute a form of genetic transfer previously unknown to occur naturally in metazoans and, if homologous, is likely to account for both the recently demonstrated allele sharing in bdelloid populations and the ectopic incorporation of foreign genes. (3) More fully characterize the massive horizontal transfer and ectopic incorporation of foreign (including bacterial, fungal and plant) genes that has occurred in bdelloids by examining transcribed genes of several rotifer species in order to determine the nature, sources, and possible functions of genes horizontally transferred from distantly related taxa. Broader Impacts: Why sexual reproduction exists, why it should take two parents rather than one to produce offspring, are questions of fundamental biological importance that are also of general public interest and afford an excellent opportunity for public education in biology. Results from this project under earlier NSF support have received wide coverage in the US and international media, and have been incorporated into college biology curricula, biology textbooks, and popular books on biology and evolution. The project will train two postdoctoral scientists, a Ph.D. student, and four undergraduates. The more than 30 Mb of bdelloid cDNA sequence generated by the project will be deposited in GenBank and will be available on a website with a graphical interface for examining read quality, coverage of assemblies, ORF identification, and annotation; for searching bdelloid sequences using BLAST or bdelloid annotation using keywords; and for downloading data, the results of BLAST searches, etc.