MOLECULAR CELL BIOLOGICAL STUDIES ON INTRACELLULAR SYMBIOSIS

我们对蚜虫胞内共生菌Buchnera和褐飞虱胞内酵母菌样共生体进行了研究，结果总结如下：1。通过对幼龄和老年蚜虫细菌细胞共生系统基因表达模式的比较，发现寄主细胞和布氏线虫中有10多个基因只有在共生系统保持功能时才特异性表达。这些基因包括参与氨基酸代谢的酶的基因，证实了我们之前的结果。我们获得了令人信服的证据，证明布氏菌产生核黄素，并为宿主提供维生素。我们利用富含G/C的限制性内切酶对其基因组DNA进行酶切，然后进行脉冲场凝胶电泳，估计了Buchnera的基因组大小。结果表明，该基因的大小为657kbp，仅为大肠杆菌基因组的七分之一。对两种不同基因的点印迹分析和细胞DNA含量的直接荧光法显示，布氏菌是一种非常特殊的细菌，在一个细胞中有100多个基因组拷贝。此外，布氏蝽的基因组拷贝数在很大程度上受寄主昆虫形态和发育阶段的影响。5 .布氏菌是一种特殊的细菌，因为它们含有一种组蛋白Hi样蛋白，这种蛋白很可能与基因组dna相互作用。我们成功克隆了一种类似酵母的共生体的尿酸酶基因，这种酶对飞虱动员组织中储存的尿酸至关重要。同时，我们将连接该基因的E.coil转化为表达载体，构建了尿酸酶基因的大规模表达体系。

We studied on Buchnera, intracellular symbiotic bacteria of aphids and intracellular yeast-like symbionts of brown planthoppers, the results of which are summarized as follows :1. Comparison of gene expression patterns of the bacteriocyte symbiotic systems from young and old aphids revealed that there are more than ten genes, of both host cell and Buchnera, that are specifically expressed only when the symbiotic system is kept functional. These genes include those for enzymes involved in the amino acid metabolism, confirming our previous results.2. We attained convincing evidence that Buchnera produce riboflavin and provision the vitamin to hosts.3. We estimated the genome size of Buchnera by digesting the genomic DNA with restriction enzymes whose restriction sites are rich in G/C, followed by pulse-field gel electrophoresis. It turned out that the genome size, 657kbp, is only one seventh of that of the genome of E.coli.4. Dot-blot analyses of two different genes and direct fluorimetry of the cellular DNA content revealed that Buchnera are very extraordinary bacteria with more than 100 genomic copies in a single cell. In addition, the genomic copy number of Buchnera is variable to a great extent due to morph and developmental stage of the host insect.5. Buchnera are exceptional as bacteria in that they contain a histone Hi -like protein, which is likely in interaction with the genomic DNA.6. We successfully cloned the gene for uricase of the yeast-like symbiont that is essential for planthoppers to mobilize the uric acid stored in their tissue. Also, we constructed a large scale expression system of the uricase gene by transforming E.coil with the gene ligated into an expression vector.