The Machinery of Mitochondrial Recombination in Higher Plants

摘要植物线粒体作为参与能量代谢的亚细胞区室，含有自身的遗传信息。 植物线粒体基因组的动态性质代表了区分植物和动物的重要特征。 了解这种性状的潜在遗传基础对于发展其进化价值及其对操纵的顺从性的认识是重要的。 两种类型的遗传交换是植物线粒体的特征：高频率的DNA交换发生在“相似”序列上，发现为大的，散布的重复序列，以及不频繁的DNA交换在“不相似”位点上，包含少至六个或七个共享核苷酸。 两者似乎都代表了植物遗传变异的重要来源。 PI实验室在模式植物拟南芥中克隆了一个基因，命名为MSH 1，该基因与线粒体DNA维持和可能与DNA交换活性有关。 本文将对MSH 1的功能进行分析。 作为这些研究的必然结果，将研究依赖于RecA基因的线粒体DNA交换活性。 该研究的中心假设是RecA与相互作用的蛋白质组分一起，通过与MSH 1活性不同的机制控制高等植物线粒体中的重组活性。 作为这一假设的检验，将分离证明与RecA相互作用的蛋白质，以及与该推定的蛋白质复合物结合的线粒体DNA序列。 RecA的功能分析将涉及突变研究和植物转化。 RecA和MSH 1功能和物理相互作用的证据也将被寻找。 拟议的研究的重要性将是识别和表征似乎是唯一适应植物的遗传网络的组成部分，并了解重组过程在植物线粒体基因组维护和传输中的作用。从实践的角度来看，线粒体重组活性的理解是导致雄性不育的突变的发展的关键，因此，拟议的研究应该是有用的农业种子工业的杂交种子。 该项目还将为本科生、研究生和博士后研究员提供培训机会;征聘代表性不足的少数群体将是一个优先事项。

Abstract Plant mitochondria, as subcellular compartments involved in energy metabolism, contain their own genetic information. The dynamic nature of the plant mitochondrial genome represents an important feature that distinguishes plants and animals. An understanding of the underlying genetic basis of this trait is important to developing an appreciation of its value to evolution and its amenability to manipulation. Two types of genetic exchange are characteristic of plant mitochondria: high frequency DNA exchange that occurs at "like" sequences found as large, interspersed repeats, and infrequent DNA exchange at "unlike" sites containing as little as six or seven shared nucleotides. Both appear to represent important sources of genetic variation in plants. The laboratory of the PI has cloned a gene in the model plant species Arabidopsis thaliana, designated MSH1, that is associated with mitochondrial DNA maintenance and possibly with DNA exchange activity. In this proposal, the function of MSH1 will be analyzed. As a corollary to these studies, mitochondrial DNA exchange activity dependent on the gene RecA will be investigated. The central hypothesis of the research is that RecA, together with interacting protein components, control recombination activity in higher plant mitochondria by mechanisms that are distinct from MSH1 activity. As tests of this hypothesis, proteins that demonstrate interaction with RecA will be isolated, as well as mitochondrial DNA sequences to which this putative protein complex binds. Functional analysis of RecA will involve mutation studies and plant transformations. Evidence for RecA and MSH1 functional and physical interaction will also be sought. The importance of the proposed study will be to identify and characterize components of a genetic network that appears to be uniquely adapted to plants, and to understand the role of recombination processes in plant mitochondrial genome maintenance and transmission. From a practical standpoint, an understanding of mitochondrial recombination activity is key to the development of mutations that cause male sterility, and hence the proposed research should be useful to the agricultural seed industry for hybrid seed. The project will also involve training opportunities for undergraduates, graduate students and postdoctoral fellows; recruitment of under-represented minorities will be a priority.