Genetics of Maize Mitochondria

对线粒体突变的分析在包括酵母、真菌和人类在内的几种生物中都提供了信息。植物线粒体基因组的遗传分析一直是有限的，因为只有少数已知祖先的突变已被描述。我们重点研究了一组在异质植物中存活的致命玉米突变(非染色体条纹；NCS)。不同的NCS突变体与不同的表型相关，这些突变被证明是影响至少三个不同线粒体基因(COX2、NAD4以及共转录的S3和L16核糖体蛋白基因)的缺失。这项建议的主要目的是阐明NCS损伤导致基因表达改变的机制。我们将分析NCS2和NCS3植物中的突变和正常转录本，并产生抗体来确定受NCS突变影响的转录本是否在非突变植物线粒体内翻译。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。拟议的研究应该澄清植物线粒体转录和转录后调控的各个方面。这项建议的第二个目标是试图开发一种利用NCS6突变体来演示玉米线粒体转化的系统，该突变体携带有良好特征的COX2基因的部分缺失。转化系统的可获得性应该有助于研究植物线粒体中可能的调控序列。

The analysis of mitochondrial mutations has been informative in several organisms, including yeast, fungi and humans. 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 a least three different mitochondrial genes (cox2, nad4 and the co-transcribed S3 and L16 ribosomal protein genes.) The major goal of this proposal is to elucidate the mechanisms by which the NCS lesions cause altered gene expression. We will analyze the mutant and normal transcripts in NCS2 and NCS3 plants and generate antibodies to determine whether the transcripts affected by NCS mutations are translated within nonmutant plant mitochondria. The long-term objective of this project is to understand the effects of individual plant mitochondrial genes on organelle biogenesis and overall cellular function. The proposed studies should clarify aspects of transcriptional and post-transcriptional regulation in plant mitochondria. A second goal of this proposal is to attempt to develop a system for demonstrating maize mitochondrial transformation using the NCS6 mutant, which carries a partial deletion of the well-characterized cox2 gene. The availability of a transformation system should facilitate studies of putative regulatory sequences in plant mitochondria.*** //