Symbiotic Association of Aphids: Biochemical Role of the Prokaryotic Endosymbiont

蚜虫的共生关联：原核内共生体的生化作用

• 批准号: 9402813
• 负责人: Paul Baumann
• 金额: $ 31万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-09-01 至 1998-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9402813&HistoricalAwards=false
• 关键词: Symbiotic; Association; Aphids; Biochemical; Role

9402813 Baumann Aphids are dependent for survival on an association with a prokaryotic endosymbiont housed within specialized cells in the aphid body cavity. Using the aphid Schizaphis graminum ( greenbud) we have found that its endosymbiont (Buchnera aphidicola) has all of the genes of the tryptophan biosynthetic pathway and the trpEG (genes for anthranilate synthase, the first enzyme of the pathway) is amplified on a plasmid. These results are consistent with past observations indicating that the endosymbiont synthesizes tryptophan which is utilized by the aphid host. Preliminary results have indicated that, in the distantly related endosymbiont of the aphid Schlectendalia chinensis, tryEG has a chromosomal location. We intend to continue this research by examining the gene organization of the tryptophan biosynthetic pathway in the endosymbiont of this aphid species and making a survey to determine the distribution of gene amplification of chromosomal location of trpEG in the endosymbionts of other aphid species. The first reaction which initiates the biosynthesis of aromatic amino acids (tryptophan, phenylalanine, tyrosine) as well as folic acid is catalyzed by 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) synthase. We intend to determine if this gene is located on a plasmid, on the chromosome or if there are isofunctional DAHP synthases. This will be accomplished by restriction enzyme and Southern blot analysis as well as the cloning and sequencing of the gene(s) for the enzyme(s). Comparisons will be made with the gene organization in E. coli and other organisms. In most prokaryotes the genes for ribosomal RNA are arranged as a single transcription unit in the order 16S, and 5S rRNAs. We have shown that B. aphidicola has only one copy of the 16S 23s rRNA gene and is unusual in that it is unlinked to the other rRNA genes. We will continue this study by examining the organization of the 23S and 5S rRNA genes in B. aphidicola. The genes will be cloned, sequenced, and the up stream and downstream regions compared to the putative promoter and terminator of the B.aphidicola 16S rRNA transcription unit. In their most active stage of growth aphids reproduce by parthenogenesis giving birth to live yound. Nothing is known concerning the number of endosymbionts during the growth cycle of the aphid. Using the quantitative polymerase chain reaction we will determine the number of copies of 16S and 23S rRNA genes in the B. aphidicola-aphid DNA preparations during the aphid growth cycle. The results will be an indication of the number of endosymbionts. Using immunological methods we will determine the amount of several essential endosymbiont consitutents. This includes ribosomes (ribosomal protein S1), RNA polymerase (beta-subunit), sigma factor and GroEL. %%% The results obtained from these studies may be of use for the eventual control of aphid populations by manipulation of the endosymbionts which are essential for their survival. ***

9402813鲍曼蚜虫取决于与蚜虫体腔中专用细胞内的原核生物内共生体的关联。 使用蚜虫schizaphis graminum（Greenbud），我们发现其内共生菌（Buchnera athidicola）具有色氨酸生物合成途径的所有基因，而TRPEG（源自雌激酶的基因，该途径的第一个酶）是plplififififif的。这些结果与过去的观察结果一致，表明内共生体合成了蚜虫宿主利用的色氨酸。 初步结果表明，在蚜虫schlectendalia chinensis的遥远相关的内共生体中，Tryeg具有染色体位置。 我们打算通过检查该蚜虫物种的内共生体中色氨酸生物合成途径的基因组织，并进行调查，以确定TRPEG在其他蚜虫物种内共生体中TRPEG染色体位置的基因扩增的分布。 引发芳香族氨基酸（色氨酸，苯丙氨酸，酪氨酸）的生物合成的第一反应以及叶酸由3-脱氧-D-阿拉宾素甲酸7-磷酸盐（DAHP）合成酶催化。 我们打算确定该基因是否位于质粒，染色体上或是否存在功能功能的DAHP合酶。 这将通过限制酶和Southern印迹分析以及酶（S）基因的克隆和测序来实现。 比较将与大肠杆菌和其他生物的基因组织进行。 在大多数原核生物中，核糖体RNA的基因在16S和5S rRNA中排列为单个转录单元。 我们已经表明，B。蚜虫只有16S 23S rRNA基因的一个副本，并且不寻常，因为它与其他rRNA基因无关。 我们将通过研究B. adphidicola中的23S和5S rRNA基因的组织来继续这项研究。 将基因克隆，测序以及向上流和下游区域与假定的启动子和B.Aphidicola 16S rRNA转录单元相比。在最活跃的生长阶段，蚜虫通过孤phenenogeneseres繁殖了活着的Yound。 关于蚜虫生长周期中内共生体的数量，尚无任何了解。 使用定量聚合酶链反应，我们将在蚜虫生长周期中确定B. adphidicola-Apphid DNA制剂中16S和23S rRNA基因的拷贝数。 结果将表明内共生体的数量。 使用免疫学方法，我们将确定几个基本内共生助理合并的数量。 这包括核糖体（核糖体蛋白S1），RNA聚合酶（β-亚基），Sigma因子和凹槽。 %%％从这些研究中获得的结果可能是通过操纵内共生体的最终控制蚜虫种群的，这对于它们的生存至关重要。 ***