Causes of Extreme Mitochondrial Mutation Rate Variation

项目摘要 线粒体突变在人类中的发生率非常高，是遗传和年龄增长的主要原因。 相关疾病。尽管突变率的升高一直被认为是高强度基因突变的副产品， 线粒体内发生的代谢活动，最近的证据已经对这一观点提出了质疑， 线粒体突变的原因在该领域存在巨大的不确定性。与人类相比，有些人 真核生物在其线粒体DNA中表现出极低的突变率。如何解决这个问题 一些生物体能够保持低线粒体突变率，这有可能告诉我们， 了解是什么原因导致它们在人类中如此之高。然而，值得注意的是， 来解决真核生物遗传学的基本问题。拟议的研究将集中在开花 植物作为理解线粒体突变率变化机制的模型。 植物中线粒体（和质体）DNA替换的速率通常低于植物核中的速率。 基因组和数量级低于动物线粒体。然而，植物也表现出极端的 线粒体序列进化速率的波动，甚至在密切相关的物种之间。进展 了解大多数植物物种中极低速率的机制， 由于研究罕见突变事件的固有技术困难而受阻。出现了新 利用深度测序和定量PCR技术直接测量罕见的 突变和量化DNA损伤率提供了一个令人兴奋的机会，以克服这些历史 隔栏.拟议的研究将把这些方法应用于野生型和突变型背景， 模式被子植物拟南芥测试一套替代假设，有关的保真度 DNA聚合酶，重组修复机制的功效，偏向基因转换的影响， 和植物细胞器中对DNA损伤的暴露/易感性。将对两种植物进行分析 和分生组织，以区分那些简单地积累在植物组织中的突变， 实际上会传给后代。这项研究还将扩展到相关的开花植物物种， 最近，线粒体序列进化的速度大大加快。这些 研究将阐明线粒体突变率变化的机制， 真核生物，并告知正在进行的辩论的作用，氧化损伤作为一种诱变力在人类 线粒体

PROJECT SUMMARY Mitochondrial mutations occur at a very high rate in humans and are a major cause of inherited and age- related diseases. Although elevated mutation rates have long been considered a byproduct of the intense metabolic activity that occurs within mitochondria, recent evidence has called this view into question, creating enormous uncertainty in the field about the causes of mitochondrial mutations. In contrast to humans, some eukaryotes exhibit extremely low rates of mutation in their mitochondrial DNA. Answering the question of how some organisms are able to maintain low mitochondrial mutation rates has the potential to inform our understanding of what causes them to be so high in humans. Remarkably, however, little effort has been made to address this fundamental question of eukaryotic genetics. The proposed research will focus on flowering plants as a model for understanding the mechanisms responsible for variation in mitochondrial mutation rate. Rates of mitochondrial (and plastid) DNA substitutions in plants are generally lower than in plant nuclear genomes and orders of magnitude lower than in animal mitochondria. However, plants also exhibit extreme fluctuations in rates of mitochondrial sequence evolution even among closely related species. Progress in understanding the mechanisms responsible for the extremely low rates in most plant species has been impeded by the inherent technical difficulties in studying rare mutation events. The advent of new methodologies that leverage deep sequencing and quantitative PCR technologies to directly measure rare mutations and quantify rates of DNA damage presents an exciting opportunity to overcome these historical barriers. The proposed research will apply these methodologies to both wild-type and mutant backgrounds in the model angiosperm Arabidopsis thaliana to test a suite of alternative hypotheses, relating to the fidelity of DNA polymerases, the efficacy of recombinational repair mechanisms, the effects of biased gene conversion, and exposure/susceptibility to DNA damage in plant organelles. Analyses will be conducted on both vegetative and meristematic tissues to distinguish mutations that simply accumulate in plant tissues from those that are actually transmitted to offspring. The research will also be extended to related species of flowering plants in which there has been a recent and massive acceleration in rates of mitochondrial sequence evolution. These investigations will elucidate the mechanisms responsible for variation in mitochondrial mutation rates across eukaryotes and inform ongoing debates about the role of oxidative damage as a mutagenic force in human mitochondria.