Post-genome project of the endocellular symbiotic bacterium, Buchnera.

在细胞内共生中，两个或两个以上的基因组及其基因表达机制不仅和谐共存，而且相互作用。在我们研究的主要材料蚜虫细菌细胞的共生系统中，有几十个巨大的、被称为细菌细胞的蚜虫特化细胞，在细胞质中含有许多原核共生体。该共生微生物被命名为Buchnera，与大肠杆菌系统发育关系密切，基于16S rDNA结构的分子系统发育分析表明，Buchnera与蚜虫的共生关系可追溯到2亿年前。这些年来，这两个伴侣已经变得如此相互依赖，他们再也不能独立生活了。我们对这一共生系统进行了近25年的广泛研究，包括Buchnera的进化、基因和基因组的结构、基因表达以及该系统对宿主代谢的意义。这些研究可细分为4项。在第三学期，我们分析了Buchnera的基因组，并在世界上首次成功地揭开了一个专一共生细菌的全貌，这表明Buchnera虽然与大肠杆菌关系密切，但却失去了大肠杆菌中发现的七分之六的基因。Buchnera基因组分析还揭示了许多对理解细胞进化具有重要意义的宝贵事实。本报告总结了第四学期蚜虫-布氏虫共生系列研究的结果。本术语中最重要的结果是在细菌细胞的转录组分析中获得的。许多基因在细菌细胞中特异性高表达，其中包括：(1)氨基酸代谢基因，包括生物合成Buchnera不能产生的氨基酸的基因，以及利用Buchnera可以合成的氨基酸的基因；(2)与运输相关的基因，包括线粒体转运体基因和编码Rab（一种调节囊泡运输的G蛋白）的基因；(3)降解细菌细胞壁的推定溶菌酶基因。少

In intracellular symbiosis, two or more genomes and their gene expression machinery coexist in a single cell not only harmoniously but mutualistically. In the symbiosis system of the aphid bacteriocyte that has been our main research materials, several tens of huge, specialized cells of aphids, called bacteriocytes, contain many prokaryotic symbionts in the cytoplasm. The symbiotic microorganism, designated Buchnera, is shown to be closely related to E. coli phylogenetically, and molecular phylogenetic analysis based on the structure of 16S rDNA suggests that the symbiosis of Buchnera with the aphid dates back to 200 million years ago. For these years the two partners have become so dependent mutualistically, they can no longer live independently from each other.We have studied on this symbiosis system extensively for about 25 years with respect to evolution of Buchnera, structure of genes and genomes, gene expression, and the system's significance in terms of the host's metabolism. Th … More ese studies may be subdivided into 4 terms. In the third term, we analyzed the Buchnera genome and successfully unveiled its whole picture for the first time in the world for an obligately symbiotic bacterium, which indicated that Buchnera, in spite of its close relationship to E. coli, has lost six sevenths genes that are found in the latter. The Buchnera genome analysis revealed also many invaluable facts significant in understanding cellular evolution.This report is to summarize the results obtained in the fourth term that concludes the series of studies on the aphid-Buchnera symbiosis. The most significant result in this term was obtained in transcriptome analysis of the bacteriocyte. A number of genes were highly expressed specifically in the bacteriocyte, which include (1)genes for amino acid metabolism, including those for biosynthesis of amino acids that Buchnera cannot produce, and those for utilization of amino acids that Buchnera can synthesize ; (2)genes related to transport, including genes for mitochondrial transporters and a gene encoding Rab, a G protein that regulates vesicular transport ; and (3)genes for putative lysozymes that degrade bacterial cell walls. Less