Mobile Genetic Elements in Sexual and Ancient Asexual Taxa

有性和古代无性分类群中的移动遗传元件

• 批准号: 0821956
• 负责人: Irina Arkhipova
• 金额: $ 65.7万
• 依托单位: Marine Biological Laboratory
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-15 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0821956&HistoricalAwards=false
• 关键词: Mobile; Genetic; Elements; Sexual; Ancient

Transposable genetic elements (TEs) are of virtually universal occurrence in eukaryotes and prokaryotes, and in multicellular eukaryotes have been found to constitute a substantial portion of the genome: nearly one-half in humans, and even more in many plants. Their existence raises fundamental questions related to eukaryotic genome structure, function, and evolution. This project is based on the view that much can be learned about TEs and their effects on genome structure by comparing their characteristics and evolution in sexual taxa with those in asexual taxa. Because of the important role of sexual reproduction in both the maintenance and limitation of deleterious TEs in eukaryotic populations, the putative asexuality and other highly unusual characteristics of bdelloid rotifers, such as the repeated DNA breakage and repair thought to occur during the cycles of desiccation and rehydration characteristic of bdelloid habitats, make them a promising model system for investigating fundamental problems associated with TEs. These problems include their proliferation, compartmentalization and distribution within genomes, the mechanisms of their copy number control, the dependence of their maintenance, dynamics and evolution on biparental reproduction, their domestication and possible role in the maintenance of chromosome ends, and their participation in horizontal gene flow, whereby TEs and other DNA may enter bdelloid genomes by means other than vertical descent. Indeed, the investigators' studies of bdelloid TEs have already revealed notable differences from sexual taxa in the types and genomic distribution of TEs and foreign DNA in bdelloid genomes, and have suggested novel ideas for the operation and evolution of systems that protect chromosomes and their ends from degradation. The principal objectives of the research are (i) to investigate subtelomeric TE-rich clusters in bdelloids in order to determine whether telomeric TE copies may constitute part of a genome defense system against invading TEs, and to uncover the role of telomere-associated retroelements in formation and function of these clusters; (ii) to investigate the origin and function of novel reverse transcriptases found in bdelloids and its possible relation to genome defense mechanisms; (iii) to further examine bdelloid and monogonont genomes for the presence of diverse intact or relict retroelements and telomeric TE-rich clusters, and to identify candidate monogonont TEs for introduction into bdelloid genomes; and (iv) to continue efforts to achieve stable transformation in order to test for proliferation of TEs introduced into internal and telomeric regions. These specific objectives are aimed at characterizing fundamental mechanisms of genome defense in bdelloids and their implications for eukaryotes generally. The research will be of interest to biologists interested in problems of genome structure and evolution, as well as to the general public. The investigators will continue to discuss their research in the media, as they have done in previous years on programs such as NPR's "The Connection" and "Talk of the Nation: Science Friday." They will contribute to the activities of Mobile Genetic Element Cluster at the Marine Biological Laboratory (MBL) at Woods Hole, and will participate in convening the annual Northeast Mobile DNA meeting. The project will continue to rely on student involvement, providing undergraduates with hands-on training and with access to the unique summer environment at the MBL, which includes Friday lectures by eminent scientists and the possibility to interact with visiting scientists and summer course students from around the world.

在真核生物和原核生物中，可替代的遗传因素（TES）实际上是普遍的，并且在多细胞真核生物中被发现构成了基因组的很大一部分：在人类中近一半，在许多植物中甚至更多。它们的存在提出了与真核基因组结构，功能和进化有关的基本问题。该项目基于这样的观点，即可以通过将性分类单元的特征和进化与无性群体中的人进行比较，可以了解TES及其对基因组结构的影响。 Because of the important role of sexual reproduction in both the maintenance and limitation of deleterious TEs in eukaryotic populations, the putative asexuality and other highly unusual characteristics of bdelloid rotifers, such as the repeated DNA breakage and repair thought to occur during the cycles of desiccation and rehydration characteristic of bdelloid habitats, make them a promising model system for investigating fundamental problems associated with TEs.这些问题包括它们的增殖，基因组中的分区和分布，其拷贝数控制的机制，其维持，动态和进化对两胎再生产的依赖性，其驯化以及它们在维持染色体末端的维持以及其参与水平基因的参与方面的作用，与其他DNA相比，与其他DNA相比，与其他基因相比。的确，研究人员对细胞类动物TE的研究已经揭示了性分类单元中TES和外源DNA在Bdelloid基因组中的类型和基因组分布的显着差异，并提出了针对保护染色体及其末端的系统的运行和演变的新思想。该研究的主要目标是（i）研究bdelloid中的亚电体TE簇簇，以确定端粒TE副本是否可能构成基因组防御系统的一部分，反对侵入TES，并揭示端粒相关的返回元素在这些晶状体的形成和功能中的作用； （ii）研究在骨动物中发现的新型逆转录酶的起源和功能及其与基因组防御机制的可能关系； （iii）进一步检查了存在多种多样或遗物的恢复元素以及端粒Te富集的簇，并鉴定候选单子群TES，以引入bdelloid基因组； （iv）继续努力实现稳定的转型，以测试引入内部和端粒区域的TE的扩散。这些特定的目标旨在表征基因组防御的基本机制及其对真核生物的影响。 对基因组结构和进化问题以及公众感兴趣的生物学家将感兴趣的研究。调查人员将继续在媒体上讨论他们的研究，就像往年对NPR的“ The Connection”和“ The Nation：Science Friday”等计划所做的那样。他们将在伍兹霍尔（Woods Hole）的海洋生物实验室（MBL）上为移动遗传元素簇的活动做出贡献，并将参加年度东北移动DNA会议。该项目将继续依靠学生的参与，为大学生提供动手培训，并在MBL上获得独特的夏季环境，其中包括著名科学家的星期五讲座，以及与世界各地的访问科学家和夏季课程互动的可能性。