Characterization of SAR-Independent Pathogen Induced Defense in Arabidopsis

植物利用一系列不同的可诱导的防御反应来预防感染和从疾病中恢复。虽然调节这些防御的一些途径是已知的，如系统获得性抵抗(SAR)，但其他关键的系统一直没有被发现。本研究旨在阐明在拟南芥son1(nim1-1的抑制子)突变体中表达的一种新形式的SAR非依赖抗性(SIR)，并定义和测试其表达与SIR相关的基因。三个目标中的两个集中在研究son1突变表型和最近描述的SON1基因产物(Kim和Delaney，2002a)。因为son1植物表现出一种新的抗性形式，所以全面描述抗性表型是至关重要的。因此，将通过双突变分析来确定Son1介导的抗性所需的防御信号转导途径，评估对这种抗性敏感的病原菌类型的范围，并评估SAR和Son1介导的抗性之间的相互作用(目标1)。目标2下的研究将检查SON1蛋白本身，其结构表明它可能是泛素连接酶复合体的一个组成部分，该复合体针对蛋白质进行破坏。为了评估SON1是否发挥这一作用，将进行测试，以确定SON1是否与泛素连接酶复合体的核心成分相互作用。其他工作将寻求识别SON1靶向的蛋白质，这些蛋白质被假设为SIR的积极调节因子。该项目的第三个目标是确定在两种表达SIR的植物基因类型中表达发生变化的基因；-son1突变体和转基因植物，它们被开发来过表达与SAR调节因子NIM1相互作用的TGA5转录因子(Kim和Delaney，2002b)。积累Son1和TGA5的植物的转录图谱将使用基于寡核苷酸的微阵列进行分析，该微阵列几乎包括所有的拟南芥基因。通过比较两种独立衍生的SIR激活植物的基因表达，可以明显看出每种植物的共同基因。一些与SIR相关的基因将接受功能分析，以确定它们在SIR中的作用。所描述的研究将产生关于在SON1植物中表达的SIR的重要信息，为深入了解SON1对SIR的调控提供洞察力，提供与SAR非依赖性抗性相关的分子标记，并为开发新的作物病害控制形式提供信息。所描述的研究在生物学方面之外还有许多更广泛的影响。这些措施包括：对本科生和研究生以及博士后进行彻底培训，扩大对代表性不足群体的研究参与，通过共享该项目产生的转录档案数据，加强研究基础设施；通过本科生、研究生和博士后人员在会议上的发言，广泛传播知识。这项研究还可以为社会提供对新途径的理解，这些新途径将能够创造出高度抗病的作物，从而改善粮食生产的经济性，并减少目前使用的化学疾病控制剂对环境的影响和对健康的影响。

Plants employ an array of distinct inducible defense responses to prevent infection and to recover from disease. While a few of the pathways that regulate these defenses are known, such as systemic acquired resistance (SAR), other critically important systems have eluded discovery. The proposed research is aimed at elucidating a novel form of SAR-independent resistance (SIR) expressed in Arabidopsis son1 (suppressor of nim1-1) mutants, and at defining and testing genes whose expression is associated with SIR. Two of the three objectives are focused on study of the son1 mutant phenotype and on the SON1 gene product, which was recently described (Kim and Delaney, 2002a). Because son1 plants express a novel form of resistance, it is essential that the resistance phenotype be fully described. Therefore, the defense signal transduction pathway requirements for son1-mediated resistance will be determined using double mutant analysis, the range of pathogen types susceptible to this resistance assessed, and the interactions between SAR and son1-mediated resistance evaluated (Objective 1). Investigations under Objective 2 will examine the SON1 protein itself, whose structure suggests it may be a component of an ubiquitin ligase complex that targets proteins for destruction. To assess whether SON1 plays this role, tests will be performed to determine whether SON1 interacts with core components of the ubiquitin ligase complex. Other work will seek to identify proteins targeted by SON1 that are hypothesized to act as positive regulators of SIR. The third objective of the project is to identify genes whose expression is altered in two genotypes of plants that express SIR; -son1 mutants and transgenic plants that were developed to overexpress the TGA5 transcription factor that interacts with the SAR-regulator NIM1 (Kim and Delaney, 2002b). The transcriptional profiles of son1 and TGA5-accumulating plants will be analyzed using oligonucleotide-based microarrays that include nearly all the Arabidopsis genes. By comparing gene expression in the two independently derived SIR-activated plants, the genes common to each will be evident. Some SIR-associated genes will be subjected to functional analysis to determine their role in SIR. The research described will yield important information on SIR expressed in son1 plants, provide insight into the regulation of SIR by SON1, provide molecular markers associated with SAR-independent resistance, and provide information that may lead to development of novel forms of disease control in crop plants. The research described has a number of broader impacts outside of its biological aspects. These include: thorough training of undergraduate and graduate students and a postdoctoral fellow, broadening participation in research of underrepresented groups, enhancing the infrastructure for research through the sharing of transcriptional profile data generated by this project; and the broad dissemination of knowledge through presentations at conferences by undergraduate, graduate and postdoctoral personnel. The research can also be of general benefit to society by providing understanding of novel pathways that will enable creation of highly disease resistant crops, thus improving the economics of food production, and reducing the environmental impact and health consequences of currently used chemical disease control agents.