INTERACTIONS BETWEEN AGROBACTERIUM AND HOST PLANTS

我们建议研究化学信号的双向交换 病原微生物农杆菌及其植物寄主。这 一种生物通过转移一种细菌引起高等植物的冠瘤 将致癌DNA片段插入植物基因组。我们的主要关注点是 基因对化学信号的转录调控 从主人那里释放出来的。几乎所有的病原体都会导致与发病机制相关的 基因对寄主释放的信号做出反应，而根癌农杆菌是一种 为研究这一现象提供了有价值的模型。在感染之初， 伤口释放的化合物通过三种蛋白质(跨膜 感觉蛋白激酶Vira、反应调节因子Virg和 周质糖结合蛋白(ChvE)激活转录 VIR规则。后来，一种名为章鱼的化合物通过OccR起作用 蛋白质(一种LysR类型的蛋白质)诱导其他基因，包括 共轭调节器Trar.TRAR和TRAI是LUXR/Luxi的成员 群体感应蛋白家族，并仅在高供体诱导tra基因 细胞密度。至少一种其他植物病原体和一种动物病原体 (铜绿假单胞菌)使用同源蛋白调节发病- 相关基因。我们工作的第二个重点是研究T-T的转移 对宿主进行DNA检测。我们将确定之前的三个 病毒区域的未知基因是毒力所必需的，并且 他们是否受Virg的监管。我们还将研究来自 一个不同的质粒作为VIRB操纵子的11个基因的模型，如 这两个操纵子是紧密同源的。理解这些共轭关系- 类似的过程可能会导致防止抗生素转移的新方法 细菌之间的抗性基因和毒素决定因素。更一般地说 这一现象是大分子络合物从 细胞和这些复合体在细胞之间的运输。

We propose to study the two-way exchange of chemical signals between the pathogenic microbe Agrobacterium tumefaciens and its plant hosts. This organism causes crown gall tumors in higher plants by transferring a segment of oncogenic DNA into the plant genome. Our primary focus is on the transcriptional regulation of genes in response to chemical signals released from hosts. Virtually all pathogens induce pathogenesis-related genes in response to host-released signals, and A. tumefaciens is a valuable model for studying this phenomenon. At the outset of infection, wound-released compounds act through three proteins (the transmembrane sensory protein kinase VirA, the response regulator VirG, and the periplasmic sugar binding protein ChvE) to activate transcription of the vir regulon. Later, a compound called octopine acts through the OccR protein (a LysR-type protein) to induce other genes, including the conjugation regulator TraR. TraR and TraI are members of the LuxR/LuxI family of quorum-sensing proteins, and induce tra genes only at high donor cell densities. At least one other plant pathogen and one animal pathogen (Pseudomonas aeruginosa) use homologous proteins to regulate pathogenesis- related genes. A second focus of our work is to study the transfer of T- DNA to the host. We will determine whether three previously uncharacterized genes in the vir region are required for virulence, and whether they are regulated by VirG. We will also study a tra operon from a different plasmid as a model for the eleven genes of the virB operon, as the two operons are closely homologous. Understanding these conjugation- like processes may lead to new ways to prevent the transfer of antibiotic resistance genes and toxin determinants between bacteria. More generally this phenomenon is an example of export of macromolecular complexes from cells and transport of these complexes between cells.