Genetics of Maize Mitochondria

一个长期的项目，以阐明突变是如何产生和恢复在植物线粒体和这些突变对植物表型和细胞功能的影响将继续进行。将继续研究在异质玉米植株中繁殖的一组致死性线粒体突变（非染色体条纹，NCS）对细胞功能的影响。最近发现，两种类型的细胞核编码的植物线粒体应激蛋白，交替氧化酶（AOX）和HSP 22显着增加，在所有的NCS突变体。有人建议，以确定在什么水平上发生这种诱导，并确定其他线粒体蛋白的差异调节NCS植物。第二个目标是了解植物线粒体基因组的完整性是如何保持的。基因组在体内作为亚基因组的集合存在，其由主动重组产生。尽管如此，线粒体基因型和它们的亚基因组互补物通常忠实地从母本传递给后代。在一个特殊的玉米品系P2中，已经发现线粒体基因组是惊人的可变的，并且新的、小的亚基因组被扩增到高水平。这些小的mtDNA环携带允许其扩增的复制起点的假设将被测试。两个独立扩增的小亚基因组在杂交中被发现是母系遗传的，这可能有助于确定线粒体基因组中那些对mtDNA的正确分离和有效复制至关重要的区域。由于线粒体在细胞程序性死亡、氧化应激和细胞器逆行调节等现象中的核心作用，最近对线粒体的兴趣越来越大。在逆向调节中，某些核基因的表达响应于细胞器代谢状态的变化而被转录激活。这项研究的结果将进一步深入了解线粒体功能的基因组调控。

A long-term project to elucidate how mutations are generated and recovered in plant mitochondria and what effects these mutations have on plant phenotypes and cellular function will be continued. An investigation into the effects on cellular function of a set of lethal mitochondrial mutations (nonchromosomal) stripe, NCS) that are propagated in heteroplasmic maize plants will be continued. It has been recently found that two types of nucleus-encoded plant mitochondrial stress proteins, alternative oxidase (AOX) and HSP22 are dramatically increased in all of the NCS mutants. It is proposed to determine at what level this induction occurs and to identify other mitochondrial proteins that are differentially regulated in NCS plants. A second objective is to learn how the integrity of plant mitochondrial genomes is maintained. The genomes exist in vivo as a collection of subgenomes, which result from active recombination. Nonetheless, mitochondrial genotypes and their subgenomic complements are usually faithfully transmitted from maternal parent to progeny. In an exceptional line of maize, P2, it has been found that nitochondrial genomes are surprisingly variable and that novel, small subgenomes are amplified to high levels. The hypothesis that these small mtDNA circles carry origins of replication that allow their amplification will be tested. Two of the independently amplified small subgenomes have been found to be maternally heritable in crosses, which may help to identify those regions of the mitochondrial genome that are critical for the proper segregation and efficient replication of mtDNA.Interest in mitochondria has intensified recently due to their central roles in phenomena such as programmed cell death, oxidative stress and organellar retrograde regulation. In retrograde regulation, the expression of certain nuclear genes is transcriptionally activated in response to changes in the metabolic state of organelles. The results of this investigation will give further insight into the genomic regulation of mitrochondrial function.