Sakai Atsushi, Takano Hiroyoshi, Kuroiwa Tsuneyoshi
Department of Biological Sciences, Faculty of Science, Nara Women's University, Nara 630-8506, Japan.
Int Rev Cytol. 2004;238:59-118. doi: 10.1016/S0074-7696(04)38002-2.
Plant cells have two distinct types of energy-converting organelles: plastids and mitochondria. These organelles have their own DNAs and are regarded as descendants of endosymbiotic prokaryotes. The organelle DNAs associate with various proteins to form compact DNA-protein complexes, which are referred to as organelle nuclei or nucleoids. Various functions of organelle genomes, such as DNA replication and transcription, are performed within these compact structures. Fluorescence microscopy using the DNA-specific fluorochrome 4',6-diamidino-2-phenylindole has played a pivotal role in establishing the concept of "organelle nuclei." This fluorochrome has also facilitated the isolation of morphologically intact organelle nuclei, which is indispensable for understanding their structure and composition. Moreover, development of an in vitro transcription?DNA synthesis system using isolated organelle nuclei has provided us with a means of measuring and analyzing the function of organelle nuclei. In addition to these morphological and biochemical approaches, genomics has also had a great impact on our ability to investigate the components of organelle nuclei. These analyses have revealed that organelle nuclei are not a vestige of the bacterial counterpart, but rather are a complex system established through extensive interaction between organelle and cell nuclear genomes during evolution. Extensive diversion or exchange during evolution is predicted to have occurred for several important structural proteins, such as major DNA-compacting proteins, and functional proteins, such as RNA and DNA polymerases, resulting in complex mechanisms to control the function of organelle genomes. Thus, organelle nuclei represent the most dynamic front of interaction between the three genomes (cell nuclear, plastid, and mitochondrial) constituting eukaryotic plant cells.
质体和线粒体。这些细胞器有自己的DNA，被认为是内共生原核生物的后代。细胞器DNA与各种蛋白质结合形成紧密的DNA - 蛋白质复合物，这些复合物被称为细胞器核或类核体。细胞器基因组的各种功能，如DNA复制和转录，都在这些紧密结构中进行。使用DNA特异性荧光染料4',6 - 二脒基 - 2 - 苯基吲哚的荧光显微镜在确立“细胞器核”的概念方面发挥了关键作用。这种荧光染料还促进了形态完整的细胞器核的分离，这对于理解它们的结构和组成是必不可少的。此外，利用分离的细胞器核开发体外转录 - DNA合成系统为我们提供了一种测量和分析细胞器核功能的方法。除了这些形态学和生物化学方法外，基因组学也对我们研究细胞器核的组成成分的能力产生了重大影响。这些分析表明，细胞器核并非细菌对应物的遗迹，而是在进化过程中通过细胞器和细胞核基因组之间广泛相互作用建立的复杂系统。预计在进化过程中，几种重要的结构蛋白，如主要的DNA压缩蛋白，以及功能蛋白，如RNA和DNA聚合酶，发生了广泛的分化或交换，从而产生了控制细胞器基因组功能的复杂机制。因此，细胞器核代表了构成真核植物细胞的三个基因组（细胞核、质体和线粒体）之间相互作用最活跃的前沿。
