Investigations of the role of host controlled peptidoglycan recycling in the regulation of the pea aphid-Buchnera symbiosis

项目摘要 动物与细菌密切相关，包括有益的共生体和有害的共生体。 病原体了解使宿主对病原体和有益体做出不同反应的细微差别 相互作用可以使治疗特异性靶向病原体。一个基本的接口， 细菌和动物的细胞是细菌的细胞壁。特别地，已知细胞壁肽聚糖（PG）是一种具有生物活性的蛋白质。 感染过程中的关键分子，无论是对病原体，如百日咳杆菌和奈瑟菌 淋病菌，以及共生菌如费氏弧菌。在豌豆蚜虫的共生模式中， 豌豆蚜管蚜及其共生细菌Buchnera aphidicola是PG途径的关键酶 在宿主基因组中编码，并且已知在含有这些基因的细胞中特异性表达。 共生细菌，并且在其他真核系统中也进行了类似的观察。的重点 一项提议是检验新的假设，即宿主对PG再循环的控制是宿主调节的关键机制 共生体的数量我们将使用新的生物化学和遗传学方法来测试这一假设， 豌豆蚜虫系统。具体来说，我们假设蚜虫之间Buchnera丰度的变化可以 可以通过宿主来源的PG基因表达水平的差异来解释，宿主利用蛋白质 改变Buchnera细胞壁，以及宿主对Buchnera PG再循环的控制建立了 布赫内拉人口规模。验证这一假设将揭示动物如何驯化致病 细菌，并将它们转化为共生体，更广泛地说，将扩大我们对 微生物与动物的相互作用，包括人类。 为了确定PG循环在共生调节中的作用，我们将：1）调查PG- 相关的寄主基因在决定Buchnera种群大小中起作用，2）决定寄主PG相关的 基因在功能上与Buchnera细胞壁相互作用，和3）证明宿主PG之间的关系， 基因和Buchnera调控。为了测试这一点，我们将量化PG基因表达的差异 具有高与低Buchnera丰度的蚜虫基因型之间的水平，表征了宿主基因 产品在体外影响Buchnera PG，并在体内询问PG基因功能，实现新的遗传学 蚜虫Buchnera系统的工具。我们预测蚜虫利用PG基因破坏Buchnera PG循环 并停止细胞分裂，使宿主能够通过负调节控制共生体的丰度。我们的基因组规模 这些方法将能够发现共生体控制的其他潜在遗传基础。拟议预算的结果 这项工作将大大有助于我们了解动物如何与共生细菌相互作用， 特别是宿主如何调节共生体这些发现可能会导致新的药物靶向细菌 昆虫疾病媒介的共生体，或开发不伤害有益共生体的抗生素。

Project Summary Animals live in close association with bacteria, including both beneficial symbionts and harmful pathogens. Understanding the nuances that enable hosts to respond differently to pathogenic versus beneficial interactions could enable therapies that specifically target pathogens. A fundamental interface between bacterial and animal cells is the bacterial cell wall. In particular, cell wall peptidoglycan (PG) is known to be a key molecule in the infection process, both for pathogens such as Bordetella pertussis and Neisseria gonorrhoeae and also for symbionts such as Vibrio fischeri. In the model symbiosis of the pea aphid, Acyrthosiphon pisum, with its bacterial symbiont, Buchnera aphidicola, key enzymes in the pathway for PG recycling are encoded in the host genome and are known to be specifically expressed in the cells that harbor the symbiotic bacteria, and similar observations have been made in other eukaryotic systems. The focus of this proposal is to test the novel hypothesis that host control of PG recycling is a key mechanism for host regulation of symbiont populations. We will test this hypothesis using novel biochemical and genetic approaches within the pea aphid system. Specifically, we hypothesize that variation in Buchnera abundance between aphids can be explained by differences in the level of host-derived PG gene expression, that the host employs proteins that alter the Buchnera cell wall, and that host control over Buchnera PG recycling establishes stability of Buchnera population sizes. Testing this hypothesis will shed light on how animals domesticate pathogenic bacteria and convert them into symbionts, and, more broadly, will expand our fundamental understanding of microbial interactions with animals, including humans. To define the role of PG recycling in the regulation of symbiosis, we will: 1) investigate whether PG- related host genes play a role in determining Buchnera population size, 2) determine how host PG-related genes interact functionally with the Buchnera cell wall, and 3) demonstrate the relationship between host PG genes and Buchnera regulation in vivo. To test this, we will quantify the differences in PG gene expression levels between aphid genotypes with high versus low Buchnera abundance, characterize how host gene products affect Buchnera PG in vitro, and interrogate PG gene functions in vivo, implementing novel genetic tools for the aphid-Buchnera system. We predict that aphids use PG genes to disrupt Buchnera PG recycling and halt cell division, enabling hosts to control symbiont abundance by negative regulation. Our genome-scale approaches will enable discovery of other potential genetic bases of symbiont control. Results of the proposed work will contribute significantly to our understanding of how animals interact with symbiotic bacteria and, more specifically, how hosts regulate symbionts. These findings may lead to novel drugs targeting bacterial symbionts of insect disease vectors, or to the development of antibiotics that do not harm beneficial symbionts.