Genetic Dissection of Systemic Acquired Resistance in Arabidopsis

被非病原体或无毒病原体感染不仅会导致局部的超敏性抗性，还会导致全身性获得性抗性（SAR）的发展，即对通常有毒病原体的抗性在整个植物中发展。SAR的建立与细胞壁羟脯氨酸水平和过氧化物酶活性的增加以及一组防御基因的系统表达有关，但这些防御在SAR中的功能意义尚未确定。系统性信号的诱导与局部过敏性坏死有关，水杨酸是SAR机制的一个组成部分，尽管它似乎不是系统性信号。已经建立了一个系统，以生物诱导SAR在拟南芥（A. thaliana）通过攻毒前接种遗传定义明确的细菌病原体。该系统显示了烟草和黄瓜中SAR的许多特征，并且已经开发出一种易于处理的突变体筛选，在初步研究中，从11,000个诱变植株群体中分离出10个证实的突变体，这些突变体表现出局部超敏抗性，但不能产生SAR。现在建议利用拟南芥中可用的工具进行SAR的遗传解剖，具体目的如下：拟南芥生物诱导SAR的进一步生理特性研究。分析过敏抗性缺陷突变体以确定局部过敏坏死在SAR生物诱导中的作用。进一步从拟南芥生态型colo和Wassilewskija生态型T- DNA标记系诱变种子中收集SAR突变体。这一发育中的突变体在优势、互补和图谱位置方面的特征。5. 利用这些突变体，通过对基因作用序列的遗传和生理分析，描绘出SAR生物诱导的信号通路。6. SAR基因的分子克隆，首先着重于已鉴定出T-DNA标记等位基因的关键基因。

9419301 Lamb Attempted infection by a non-pathogen or an avirulent form of a pathogen can result not only in localized hypersensitive resistance, but also in the development of systemic acquired resistance (SAR) in which resistance to normally virulent pathogens develops throughout the plant. Establishment of SAR is associated with increases in cell wall hydroxyproline levels and peroxidase activity, together with the system expression of a subset of defense genes, but the functional significance of these defenses in SAR has not been established. Induction of the systemic signals is correlated with localized hypersensitive necrosis, and salicylic acid is a component of the SAR mechanism although it does not appear to be the systemic signal. A system has been extablished for biological induction of SAR in Arabidopsis (A. thaliana) by pre-challenge inoculation with genetically well-defined bacterial pathogens. This system exhibits many of the features of well-characterized SAR in tobacco and cucumber, and a tractable mutant screen has been developed that in preliminary studies resulted in the isolation, from a population of 11,000 mutagenized plants, of 10 confirmed mutants that exhibit local hypersensitive resistance but fail to develop SAR. It is now proposed to exploit the tools available with Arabidopsis for genetic dissection of SAR with the following specific objectives: 1. Further physiological characterization of biologically induced SAR in Arabidopsis. 2. Analysis of hypersensitive resistance-defective mutants to define the role of localized hypersensitive necrosis in the biological induction of SAR. 3. Further develop the collection of SAR mutants from mutagenized seeds of Arabidospsis ecotype Col-O and T- DNA taggd lines of ecotype Wassilewskija. 4. Characterization of this developing collection of mutants with respect to dominance, complementation, and map position. 5. Use these mutants to delineate the signal pathway for biological induction of SAR by genetic and physiological analysis of the sequence of gene action. 6. Molecular cloning of SAR genes with an initial emphasis on key genes for which T-DNA tagged alleles have been identified.