Mechanisms of mRNA Destabilization During the Plant Defense Response

[409089]虽然直接和间接证据表明mRNA在许多基因的表达中是一个重要的决定因素，但对植物中mRNA稳定性的分子调控机制知之甚少。植物防御反应的特点是编码富含大豆脯氨酸的蛋白PvPRP1、延伸蛋白、β -微管蛋白以及一些未知蛋白的mrna的快速丢失。在这些mRNA中，PvPRP1 mRNA下调是目前机制表征最好的。PvPRP1 mRNA在激发子处理后不稳定，并且已经鉴定出一种特异性结合该转录物的蛋白（PRP-BP）。纯化RNA结合蛋白将是一个主要目标，以确定其生化特性，包括通过激发子处理和与PvPRP1 mRNA相互作用的翻译后激活。此外，纯化蛋白的可用性将允许克隆其编码基因和生产PRP-BP特异性抗体，用于蛋白质的免疫细胞化学定位。暴露于病原体引发的最迅速的过程之一是活性氧（AOS）的显著释放，这被称为氧化爆发。AOS作为诱导植物抗菌素生物合成的信号中间体的可能性受到了广泛的关注。然而，AOS调控植物抗毒素积累和其他细胞内防御相关变化的机制尚不清楚。本研究将利用生化和分子方法来阐明AOS的作用以及细胞谷胱甘肽水平的变化在激发剂诱导的信号通路中导致PvPRP1和植物抗毒素通路mRNA水平的调节。正在研究的实验系统是真菌病原体与寄主植物（豆类）之间的相互作用。在更普遍的水平上，这些研究的结果将有助于我们理解氧化应激对基因表达的调节。＊＊＊

9409089 Mehdy Little is known concerning the molecular mechanisms regulating mRNA stability in plants although direct and indirect evidence indicates that it is an important determinant in the expression of many genes. The plant defense response is characterized by a rapid loss of mRNAs encoding the bean proline-rich protein, PvPRP1, an extensin, Beta-tubulin as well as a number of unknown proteins. Among these mRNAs, the PvPRP1 mRNA down-regulation is currently the best characterized mechanistically. The PvPRP1 mRNA is destabilized after elicitor treatment and a protein which specifically binds this transcript has been identified (PRP-BP). Purification of the RNA binding protein will be a major goal in order to define its biochemical properties including apparent post- translational activation by elicitor treatment and interaction with the PvPRP1 mRNA. In addition, availability of the purified protein will allow cloning of its encoding gene and production of PRP-BP- specific antibodies for immunocytochemical localization of the protein. One of the most rapid processes triggered by exposure to pathogens is the striking release of active oxygen species (AOS) which is termed the oxidative burst. The possibility that AOS serve as signal intermediates which induce phytoalexin biosynthesis has received considerable attention. However, the mechanism(s) of AOS regulation of phytoalexin accumulation and other intracellular defense-related changes is unknown. This research will use biochemical and molecular approaches to clarify the roles of AOS and changes in cellular glutathione levels in elicitor-induced signalling pathways leading to regulation of PvPRP1 and phytoalexin pathway mRNA levels. The experimental system being studied is the interaction between the fungal pathogen and the host plant (bean). At a more general level, the results of these studies will contribute to our understanding of oxidative stress regulation of gene expression. ***