Evolution of a Mitochondrial Gene and its Intron in Parasitic and Nonparasitic Plants

9811362 deamphilis Support被要求研究在不同开花植物线粒体基因细胞色素氧化酶I （coxI）中相同位置发现的I族内含子的历史。内含子与真菌中一个已被充分研究的感染性内含子同源并具有关键的结构元素。内含子出现在开花植物的许多不相关的谱系中，而在绝大多数被研究的开花植物中不存在。令人惊讶的是，内含子特别集中在寄生植物中，它们与其他植物和真菌有着密切的共生关系。这种模式和寄生植物的生物学特征表明，一些寄生植物可能能够结合外源DNA序列和/或可能在遗传转移到宿主谱系中扮演内含子来源的角色。拟议的研究将测试基于生物学的假设，这些假设可能解释coxI内含子在植物谱系中的存在和运动。收集的数据将定义内含子在寄生和非寄生植物群体中的精确分布，序列的基因和细胞位置，以及coxI内含子和外显子序列的系统发育比较。第二个线粒体基因atpA也将被检测，以提高coxI外显子的系统发育分辨率和可靠性。（植物线粒体）的历史。这项研究将首次对植物线粒体基因及其内含子进行全面分析；这些结果将对我们理解细胞器遗传学、移动遗传元件以及分子进化和系统学的基本问题具有重要意义。此外，本项目对社会的广泛意义还包括：1)培养本科生、研究生和博士后科学家；2)在植物细胞器序列中识别入侵遗传元件的潜力；3)内含子研究的系统发育方法的发展，可能在理解生物学、农业和医学中的其他入侵元件方面有更广泛的应用；4)有助于对寄生植物的认识，有助于控制农业中有害的寄生杂草。

9811362 dePamphilis Support is requested to study the history of a Group I intron found at an identical location in the mitochondrial gene cytochrome oxidase I (coxI) of diverse flowering plants. The intron is homologous with and has key structural elements of a well-studied infectious intron in fungi. The intron occurs in numerous unrelated lineages of flowering plants, while being absent from the vast majority of flowering plants examined. Surprisingly, the intron is particularly concentrated in parasitic plants, which have intimate symbiotic associations with other plants and fungi. This pattern, and features of the biology of parasitic plants, suggests the possibility that some parasitic plants are capable of incorporation of foreign DNA sequences and/or may have played a role as an intron source in genetic transfers to host lineages. The proposed research will test biologically-based hypotheses that may explain the presence and movement of the coxI intron among plant lineages. The data collected will define the precise distribution of the intron across parasitic and nonparasitic plant groups, the genic and cellular location of the sequences, and phylogenetic comparisons of coxI intron and exon sequences. A second mitochondrial gene, atpA, will also be examined, to improve the phylogenetic resolution and reliability of the coxI exon (ie., plant mitochondrial) history. This research will represent the first comprehensive analysis of a plant mitochondrial gene and its intron; the results will have important implications for our understanding of organelle genetics, mobile genetic elements, and fundamental problems of molecular evolution and systematics. In addition, the broader significance of this project to society includes: 1) Training of undergraduate, graduate, and postdoctoral scientists; 2) Potential for the identification of invasive genetic elements in plant organelle sequences, 3) Development of phylogenetic approaches to the study of intr ons that may have broader application to understanding other invasive elements in biology, agriculature, and medicine; 4) Contributing to an understanding of parasitic plants, which could aid efforts to control harmful parasitic weeds in agriculture.