Collaborative Research: Molecular Genetic Studies of Bdelloid Rotifers

合作研究：蛭形轮虫的分子遗传学研究

• 批准号: 0544305
• 负责人: Matthew Meselson
• 金额: $ 78.25万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-05-01 至 2009-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0544305&HistoricalAwards=false
• 关键词: Collaborative; Research; Molecular; Genetic; Studies

Although there are many hypotheses, there is no general agreement regarding what maintains sexual reproduction and causes the early extinction of lineages that abandon it. A promising approach to the resolution of this fundamental problem is the study of rotifers of Class Bdelloidea, a highly unusual group of invertebrate animals comprising some 370 described species in which males, hermaphrodites, vestigial male structures, and meiosis are unknown and which has nevertheless persisted and successfully evolved and diversified for tens of millions of years. This project will investigate the relationship between bdelloid asexuality and genome structure, and its possible connection with the ability of bdelloids to withstand desiccation characteristic of their natural habitats and their recently discovered ability to recover from extremely high levels of ionizing radiation. Research will include: (1) Sequencing and cytogenetic studies of selected regions of bdelloid genomes within and between species in order to obtain an overall description of bdelloid genome structure; (2) Characterization of the genomic consequences of DNA damage repair following the exposure of bdelloids to desiccation and to ionizing radiation; and (3) Development of RNA interference to determine the functional role of DNA repair and recombination genes in bdelloid resistance to desiccation and to ionizing radiation. The experiments are designed to test the possibility that selection for recovery from high levels of DNA damage associated with the frequent desiccation of bdelloid rotifers in their ephemerally aquatic habitats accounts for basic features of their genome structure, including the apparent presence of syntenic chromosome pairs, the absence of genes for histone H2A in otherwise canonical histone gene clusters, and the lack of parasitic retrotransposons, and may also account for their evolutionary success in the absence of sexual reproduction. In addition, considering the several unusual features of bdelloid genomes already known, continued molecular genetic and comparative studies of these organisms may well reveal further novel features, knowledge of which may have important implications for understanding the predominance of sexual reproduction among animals and plants, the early extinction of asexual lineages, and the genomic consequences of prolonged asexuality.Although sex is the dominant form of reproduction among animals and plants, why sex persists, and what causes the extinction of lineages that abandon it, remains one of the most perplexing questions in biology. This project will investigate one of the great exceptions to the rule that asexual lineages are an evolutionary dead end: the rotifers of the Class Bdelloidea, a group of aquatic invertebrate animals in which males, hermaphrodites, and sex are unknown and which has nevertheless persisted and successfully evolved and diversified into more than 370 species over tens of millions of years. Research will explore the relationship between bdelloid asexuality and genome structure, and its possible connection with the ability of bdelloids to withstand the extreme dehydration they encounter in their natural habitat and their recently discovered ability to recover from extremely high levels of radiation. Undergraduate students from Harvard and small, liberal arts schools will participate in the project and will have the opportunity to carry out research at both Harvard and the Marine Biological Laboratory at Woods Hole.

尽管有许多假说，但关于是什么维持了有性生殖，并导致放弃有性生殖的谱系的早期灭绝，还没有达成普遍的共识。解决这个基本问题的一个有希望的方法是对蛭形目轮虫的研究，蛭形目轮虫是一个非常不寻常的无脊椎动物类群，包括约370种已描述的物种，其中雄性，雌雄同体，退化的雄性结构，和减数分裂是未知的，但它仍然持续存在，并成功地进化和多样化了数千万年。 该项目将调查蛭形动物无性繁殖与基因组结构之间的关系，以及其与蛭形动物自然栖息地特有的耐干燥能力和最近发现的从极高水平的电离辐射中恢复的能力之间的可能联系。 研究将包括：（1）对物种内和物种间蛭形生物基因组的选定区域进行测序和细胞遗传学研究，以获得蛭形生物基因组结构的总体描述;（2）表征蛭形生物暴露于干燥和电离辐射后DNA损伤修复的基因组后果;（3）RNA干扰技术在蛭形虫抗干燥和电离辐射中的应用。 这些实验旨在测试从与蛭形轮虫在其短暂的水生栖息地中频繁脱水相关的高水平DNA损伤中恢复的选择解释其基因组结构的基本特征的可能性，包括明显存在同线染色体对，在其他典型的组蛋白基因簇中缺乏组蛋白H2 A基因，以及缺乏寄生性反转录转座子，也可能是它们在没有有性生殖的情况下进化成功的原因。 此外，考虑到已知蛭形虫基因组的几个不寻常的特征，对这些生物的持续分子遗传学和比较研究可能会揭示更多的新特征，这些特征的知识可能对理解动植物中有性生殖的优势，无性谱系的早期灭绝，以及长期无性恋的基因组后果。尽管性是动植物繁殖的主要形式，但为什么性会持续存在，是什么原因导致放弃性的谱系灭绝，仍然是生物学中最令人困惑的问题之一。 这个项目将调查无性系是进化死胡同的规则的一个伟大的例外：蛭形纲的轮虫，一组水生无脊椎动物，其中雄性，雌雄同体和性别是未知的，但仍然坚持和成功地进化和多样化超过370个物种超过数千万年。 研究将探索蛭形虫无性与基因组结构之间的关系，以及它与蛭形虫在自然栖息地遇到的极端脱水的能力以及最近发现的从极高水平的辐射中恢复的能力之间的可能联系。 来自哈佛和小型文科学校的本科生将参与该项目，并将有机会在哈佛和伍兹霍尔的海洋生物实验室开展研究。