Genetics of Maize Mitochondria

该项目的长期目标是了解单个植物线粒体基因对细胞器生物发生和整体细胞功能的影响。植物线粒体基因组的遗传分析一直受到限制，因为只有少数具有已知祖先的突变被描述。我们集中研究了一组在异质植物中存活的致死性玉米突变（非染色体条纹；NCS）。不同的NCS突变体与不同的表型相关，并且突变已被证明是影响至少三种不同线粒体基因（cox2， nad4和共转录的S3和L16核糖体蛋白基因）表达的缺失。目前研究的主要目标是将细胞色素氧化酶亚基2的5'端和启动子序列缺失的同质线粒体转化为可区分的、功能性的cox2拷贝。这将使高等植物线粒体可以进行基因操作，否则就无法进行。正常启动子和突变启动子将在体内进行测试。我们建议继续分析新的线粒体突变，特别是部分表征的NCS4突变。NCS4突变体重排涉及整合到线粒体基因组中的s2质粒序列。最后，我们建议继续我们的遗传学方法来分析线粒体在植物发育中的作用。处于不同氧化磷酸化阶段的突变体对叶绿素水平和叶绿体功能核编码产物的产生有不同的影响。我们还将利用这些突变体来确定线粒体功能何时对细胞、组织和器官的存活至关重要。该项目的长期目标是了解单个植物线粒体基因对细胞器生物发生和整体细胞功能的影响。在该奖项的任期内，重点将放在：(1)开发转化高等植物线粒体的程序；(2)继续分析现有的线粒体突变；(3)继续分析线粒体在植物发育过程中的作用。＊＊＊

Abstract 9406055 A long-term objective of this project is to understand the effects of individual plant mitochondrial genes on organelle biogenesis and overall cellular function. The genetic analysis of plant mitochondrial genomes has been limited due to the fact that only a few mutations with known progenitors have been described. We have focused on a set of lethal maize mutations (Nonchromosomal stripe; NCS) that survive in heteroplasmic plants. Different NCS mutants are associated with distinct phenotypes and the mutations have been shown to be deletions affecting the expression of at least three different mitochondrial genes (cox2, nad4 and the co-transcribed S3 an L16 ribosomal protein genes. The major goal of the current proposal is to transform mitochondria that are homoplasmic for a deletion of the 5' end and promoter sequences of cytochrome oxidase subunit 2 with a distinguishable, functional copy of cox2. This would open up higher plant mitochondria to genetic manipulations that cannot otherwise be performed. Normal and mutant promoter constructs will be tested in vivo. We propose to continue our analyses of new mitochondrial mutations, particularly the partially characterized NCS4 mutation. The NCS4 mutant rearrangement involves S2-plasmid sequences that have incorporated into the mitochondrial genome. Finally, we propose to continue our genetic approach to analyzing the roles of mitochondria during plant development. The mutants in different steps of oxidative phosphorylation have distinguishable effects on chlorophyll levels and the production of nuclear-coded products for chloroplast function. We will also use the mutants to determine when mitochondrial function is essential for the survival of cells, tissues and organs. %%% The long-term objective of this project is to understand the effects of individual plant mitochondrial genes on organelle biogenesis and overall cellular function. During the tenure of this award, the focus will be on: (1) devel oping procedures for transforming higher plant mitochondria (2) continuing the analysis of existing mitochondrial mutations and (3) continuing to genetically analyze the role(s) of mitochondria during plant development. ***