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: 0544199
• 负责人: David Mark Welch
• 金额: $ 59.71万
• 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: 2006
• 资助国家: 美国
• 起止时间: 2006-05-01 至 2010-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0544199&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，但关于是什么维持有性繁殖并导致放弃有性繁殖的血统早期灭绝，并没有普遍的共识。解决这一根本问题的一个有希望的方法是研究瓢虫总纲的轮虫，这是一类非常不寻常的无脊椎动物，由大约370个所描述的物种组成，其中雄性、两性、残留的男性结构和减数分裂是未知的，尽管如此，它们仍然存在并成功地进化了数千万年。该项目将研究蜈蚣无性与基因组结构之间的关系，以及它可能与蜈蚣抵抗干燥的能力(其自然栖息地的特点)以及它们最近发现的从极高水平的电离辐射中恢复的能力的可能联系。这方面的研究将包括：(1)种内和种间蜈蚣基因组选定区域的测序和细胞遗传学研究，以全面描述蜈蚣基因组的结构；(2)蜈蚣暴露于干燥和电离辐射后DNA损伤修复的基因组后果的表征；以及(3)开发RNA干扰以确定DNA修复和重组基因在蜈蚣抗干燥和抗电离辐射中的功能作用。这些实验旨在测试这样一种可能性，即为了从与短期水生栖息地经常脱水有关的高水平DNA损伤中恢复而进行的选择，是否解释了它们基因组结构的基本特征，包括明显存在共线染色体对，在其他典型的组蛋白基因簇中缺乏组蛋白H2A基因，以及缺乏寄生反转录转座子，也可能解释了它们在没有有性繁殖的情况下进化成功的原因。此外，考虑到蜈蚣类基因组已知的几个不同寻常的特征，继续对这些生物进行分子遗传学和比较研究可能会揭示更多的新特征，对这些新特征的了解可能对理解动植物中有性生殖的优势、无性血统的早期灭绝以及长期无性繁殖的基因组后果具有重要意义。尽管有性繁殖是动物和植物的主要繁殖形式，但为什么有性存在，以及是什么导致放弃有性的世系灭绝，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血统是进化死胡同这一规则的一个很大的例外：蜈蚣总科的轮虫，这是一组水生无脊椎动物，雄性、两性和性别未知，但在数千万年的时间里，这种动物仍然存在并成功地进化和多样化，形成了370多个物种。研究将探索蜈蚣无性与基因组结构之间的关系，以及它可能与蜈蚣承受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。来自哈佛大学和小型文科学校的本科生将参与该项目，并将有机会在哈佛大学和伍兹霍尔的海洋生物实验室进行研究。