Mitochondrial/Nuclear Regulation of Respiration in Arabidopsis

线粒体有它们自己的基因组，然而，它们的大多数蛋白质是核编码的，这些蛋白质的表达和输入需要细胞器和细胞核之间高度调控的双向通讯。到目前为止，分离植物线粒体-核通讯的元件是不可行的。缺失的成分一直是线粒体功能的一个很容易得分的特征，对环境信号做出反应。植物线粒体具有与质子转运和ATP合成无关的交替氧化酶(AOX)的分支呼吸途径。寒冷、伤害、活性氧(ROS)和病原体攻击等增加了交替氧化酶的活性和AOX基因的表达。在实验室中，AOX在植物中也是一种可有可无的活性，因此它的水平可能是转基因的，缺乏AOX活性的潜在突变体可能会被恢复。我们的研究集中在分离线粒体-核信号转导中的突变体，使用AOX表达来对线粒体功能进行评分。我们已经设计了一种视觉屏幕，用于氧化应激攻击后受损的AOX诱导。为了补充这一筛选，我们使用微阵列分析来进一步表征突变体，并识别与应激诱导的AOX表达有关的基因和基因簇。对拟南芥叶片线粒体基因表达的初步微阵列实验表明，该方法是成功的。[初始数据可在网上获得：http://genome WWw4.stanford.edu/微阵列/smd由实验者麦金托什提供]为了确保基因组的完全覆盖，我们将使用寡核苷酸阵列、cDNA微阵列和定向“线粒体”阵列。突变体和转基因植物将被用于破译线粒体参与氧化应激信号和细胞死亡，以及AOX在超强毒力反应中的作用。AOX和ROS参与细胞死亡的研究将通过细胞色素c基因家族(at-CC)的表达、线粒体和胞浆中的细胞色素c水平以及细胞色素途径的活性来研究。

Mitochondria have their own genomes, however, the majority of their proteins are nuclear-encoded and the expression and import of these proteins requires a highly regulated, two-way communication between organelles and the nucleus. To date, it has not been feasible to isolate the elements of mitochondrion-nucleus communication in plants. The missing component has been an easily scorable trait for mitochondrial function, one responsive to environmental signals. Plant mitochondria have a branched respiratory pathway with an alternative oxidase (AOX) not coupled to proton translocation and ATP synthesis. Cold, wounding, Reactive Oxygen Species (ROS), and pathogen attack, among others, increase alternative oxidase activity and Aox gene expression. AOX, in the laboratory, is also a dispensable activity in plants, thus its levels may be genetically modified and potential mutants lacking AOX activity recovered. Our research is centered around the isolation of mutants in mitochondrion-nucleus signaling using AOX expression to score for mitochondrial function. We have devised a visual screen for impaired AOX induction after challenge by oxidative stress. To complement this screen, we use microarray analysis to further characterize the mutants, and to identify genes and gene clusters involved in stress-induced AOX expression. Preliminary microarray experiments on mitochondrial gene expression in Arabidopsis leaves establish that this approach can be successful. [Initial data are available online: http://genome www4.stanford.edu/MicroArray/SMD under experimenter "McIntosh"] To ensure complete coverage of the genome we will use oligoarrays, cDNA arrays and directed "mitochondrial" arrays. Mutants in conjunction with transgenic plants will be used to decipher mitochondrial involvement in oxidative stress signaling and cell death, and the role of AOX in the hypevirulence response. AOX and ROS involvement in cell death will be studied through cytochrome c gene family (At-Cc) expression, cytochrome c levels in the mitochondrion and cytosol, and cytochrome pathway activity.