Functional Analyses of NPR1 in Plant Defense

描述(申请人提供)：克服感染是所有真核生物在无处不在的微生物中生存和进化所必须面对的斗争。研究宿主-微生物的相互作用对于医学、农业和许多其他人类事务的发展，包括打击生物恐怖主义的威胁，具有重要的意义。该项目的长期目标是了解植物抵御感染的分子机制。拟南芥NPR1蛋白是多种防御途径的主要调节者。它是水杨酸(SA)介导的系统获得性抗性(SAR)所必需的。NPR1的突变取消了SA诱导的基因表达和SAR。在诱导后，NPR1被定位于核以激活基因表达。然而，这一关键监管步骤的机制尚不清楚。除SAR外，NPR1还参与SA介导的对茉莉酸诱导的防御通路的串扰抑制。了解NPR1在SAR和JA信号转导中的双重作用对于理解这些信号转导途径的调控机制和相互作用至关重要。此外，识别NPR1在每个反应中的靶基因将导致对这些防御反应的分子基础的新的见解。因此，该项目的两个具体目标是：(1)确定控制NPR1活动的调控机制。通过这个特定的目标，将确定细胞SA水平的升高如何导致核转位和NPR1蛋白的激活。不同的化学修饰，如二硫键的形成和蛋白质的磷酸化对NPR1蛋白活性的影响将被检测。(2)阐明NPR1在不同防御途径中的功能。这一特定的目的将集中在了解NPR1如何响应SA，作为SAR的正调节因子和JA介导的防御途径的负调节因子的双重角色，以及NPR1在这两条防御途径中调控哪些基因。更好地理解植物免疫具有重要的理论意义和现实意义。比较植物和动物的免疫反应可能会导致发现控制宿主-微生物相互作用的共同机制。利用植物的先天免疫来控制作物病害，可能会导致农药的替代，其中许多农药会造成环境污染，对人类健康有害。

DESCRIPTION (provided by applicant): Overcoming infection is a struggle that all eukaryotic organisms have to face to survive and evolve among the ubiquitously present microorganisms. Studying host-microbe interactions is of fundamental importance to the development of medicine, agriculture and many other human affairs, including the fight against the threat of bio-terrorism. The long-term goal of this project is to understand the molecular mechanisms by which plants defend themselves against infection. The Arabidopsis NPR1 protein is a master regulator of multiple defense pathways. It is required for the salicylic acid (SA)-mediated systemic acquired resistance (SAR). Mutations in NPR1 abolish SA-induced gene expression and SAR. Upon induction, NPR1 is nuclear localized to activate gene expression. However, the mechanism of this key regulatory step is unknown. Besides SAR, NPR1 is also involved in SA-mediated cross-talk inhibition of a defense pathway induced by jasmonic acid. Understanding the dual role of NPR1 in SAR and JA-signaling will be essential for understanding the control mechanisms and interactions between these pathways. Moreover, identification of target genes of NPR1 in each response will lead to new insights into the molecular basis for these defense responses. Therefore, the two specific aims of this project are: (1) Determine the regulatory mechanisms that control NPR1 activity. Through this specific aim, it will be determined how elevation of cellular SA levels leads to nuclear translocation and activation of the NPR1 protein. The effects of different chemical modifications such as disulfide bond formation and protein phosphorylation on NPR1 protein activity will be examined. (2) Elucidate NPR1 functions in different defense pathways. This specific aim will focus on understanding how NPR1, in response to SA, plays a dual role as a positive regulator of SAR and a negative regulator of JA-mediated defense pathway and what genes NPR1 regulates in these two defense pathways. Better understanding of plant immunity will have both theoretical and practical significance. Comparing immune responses in plants and animals may lead to discovery of common mechanisms governing host-microbe interactions. Using plants' innate immunity to control crop disease may lead to replacement of pesticides, many of which cause pollution of the environment and are harmful to human health.