Molecular Genetic Analysis of the Xanthomonas oryzae pv. oryzae Avirulence Determinants

米黄单胞菌 pv. 的分子遗传学分析。

• 批准号: 0110483
• 负责人: Pamela Ronald
• 金额: $ 36万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-07-15 至 2004-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0110483&HistoricalAwards=false
• 关键词: Molecular; Genetic; Analysis; Xanthomonas; oryzae

In the establishment of infection, many mammalian and plant bacterial pathogens produce effector molecules that are delivered to host cells. Transport of these effectors is accomplished through several different mechanisms. For example, bacterial Type III secretion systems channel effectors directly into the host cell whereas bacterial Type I systems secrete effectors into the extracellular environment. In many plant/pathogen interactions, host resistance responses are initiated via intracellular receptors encoded by plant disease resistance genes that recognize Type III secreted effector molecules encoded by bacterial avirulence (avr) genes. In contrast, the mechanisms by which plant cell surface receptors respond to extracellular effectors are unknown. Xa21 is a rice resistance gene encoding a presumed receptor kinase that confers resistance to Xanthomonas oryzae pv. oryzae (Xoo) Philippine race 6, the causal agent of bacterial leaf blight, the most destructive bacterial disease of rice in Asia and Africa. Dr. Ronald has shown that the presumed extracellular leucine rich repeat domain of XA21 is responsible for specific recognition of the avirulent strain Xoo Philippine race 6. Dr. Ronald has identified 6 Xoo genes from this strain that are required for the avirulence function. Three of these genes (xooA, xooB, xooC) encode proteins that share similarity with components of Type I secretion systems of gram negative bacteria. The long-term goal of this proposal is to elucidate the relationship and function of these six Xoo avirulence determinants, identify and characterize the effector molecule and analyze the interaction between the effector and rice receptor kinase XA21. The Xa21/Xoo interaction is particularly advantageous for these studies for several reasons. Xa21 is the only disease resistance gene encoding a receptor kinase so far identified and likely recognizes an extracellular effector. Xoo is genetically tractable and the genes encoding Type I secretion systems are characterized. Finally, rice is a model for studies of all cereals and therefore the expected results will have a broad impact on understanding and controlling bacterial diseases of cereals. Accomplishment of the proposed objectives is expected to lead to the first detailed understanding of the roles of Type 1 secretion systems and sulfation in determining host specificity of phytopathogenic bacteria.

在感染建立过程中，许多哺乳动物和植物细菌病原体产生递送至宿主细胞的效应分子。 这些效应物的运输是通过几种不同的机制完成的。 例如，细菌III型分泌系统将效应子直接导入宿主细胞，而细菌I型系统将效应子分泌到细胞外环境中。在许多植物/病原体相互作用中，宿主抗性反应通过由植物抗病基因编码的细胞内受体启动，所述细胞内受体识别由细菌无毒（avr）基因编码的III型分泌的效应分子。 相反，植物细胞表面受体对细胞外效应物的反应机制尚不清楚。Xa 21是一个水稻抗病基因，编码一个假定的受体激酶，赋予对黄单胞菌的抗性。白叶枯病是亚洲和非洲水稻上最具破坏性的细菌性病害。罗纳德博士已经表明，XA 21的假定的细胞外富含亮氨酸的重复结构域负责特异性识别无毒菌株Xoo菲律宾小种6。罗纳德博士已从该菌株中鉴定出无毒功能所需的6个Xoo基因。这些基因中的三个（xooA、xooB、xooC）编码与革兰氏阴性菌的I型分泌系统的组分具有相似性的蛋白质。本研究的长期目标是阐明这6个Xoo无毒决定因子的相互关系和功能，鉴定和表征效应分子，并分析效应分子与水稻受体激酶XA 21之间的相互作用。Xa 21/Xoo相互作用对于这些研究特别有利，原因有几个。Xa 21是迄今为止鉴定的唯一编码受体激酶的抗病基因，并且可能识别细胞外效应物。Xoo在遗传上是易处理的，并且编码I型分泌系统的基因被表征。最后，水稻是所有谷物研究的模型，因此预期结果将对理解和控制谷物细菌性疾病产生广泛影响。实现所提出的目标，预计将导致第一次详细了解的作用，1型分泌系统和硫酸化在确定植物病原细菌的宿主特异性。