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

在细胞内共生中，两个或多个基因组及其基因表达机制不仅和谐地共存于单个细胞中，而且相互作用。在我们主要研究的蚜虫细菌细胞共生系统中，几十个巨大的、特化的蚜虫细胞，称为细菌细胞，在细胞质中含有许多原核共生体。这种共生微生物命名为Buchnera，与大肠杆菌在系统发育上有密切的亲缘关系，基于16S rDNA结构的分子系统发育分析表明，Buchnera与蚜虫的共生可以追溯到2亿年前。这些年来，这两个伙伴变得如此相互依赖，他们不能再独立生活。我们从Buchnera的进化、基因和基因组的结构、基因表达以及该系统在寄主代谢方面的意义等方面对这种共生系统进行了大约25年的广泛研究。TH…更多的ESE研究可以细分为4个学期。在第三个学期中，我们分析了Buchnera基因组，并在世界上首次成功地揭示了它的全貌，这表明尽管Buchnera与大肠杆菌关系密切，但它已经丢失了在后者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取得的结果，总结了关于蚜虫-Buchnera共生的一系列研究。这一时期最显著的结果是细菌细胞的转录组分析。许多基因在细菌细胞中高度特异表达，其中包括(1)氨基酸代谢基因，包括Buchnera不能产生的氨基酸生物合成基因，以及Buchnera可以合成的氨基酸利用基因；(2)与运输相关的基因，包括线粒体转运蛋白基因和编码Rab的基因，Rab是一种调节囊泡运输的G蛋白；以及(3)可能的溶菌酶基因，可降解细菌细胞壁。较少

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