Mechanisms of mRNA Destabilization During the Plant Defense Response

9409089虽然直接和间接证据表明，信使核糖核酸是许多基因表达的重要决定因素，但对调节植物信使核糖核酸稳定性的分子机制知之甚少。植物防御反应的特征是编码大豆富含脯氨酸的蛋白PvPRP1、一种延伸素、β-微管蛋白以及一些未知蛋白的mRNAs的迅速丢失。在这些mRNAs中，PvPRP1mRNA下调是目前最好的机制特征。PvPRP1 mRNA在激发子处理后不稳定，并且已经确定了一种与该转录物特异结合的蛋白质(PRP-BP)。对RNA结合蛋白的纯化将是确定其生化特性的主要目标，包括激发子处理的明显翻译后激活以及与PvPRP1 mRNA的相互作用。此外，纯化蛋白的可获得性将使其编码基因的克隆和PRP-BP特异性抗体的产生用于对该蛋白进行免疫细胞化学定位。接触病原体引发的最快速的过程之一是活性氧物种(AOS)的显着释放，这被称为氧化爆发。AOS作为诱导植物保卫素生物合成的信号中间体的可能性已经引起了相当大的关注。然而，AOS调节植物防御素积累和其他细胞内防御相关变化的机制(S)尚不清楚。本研究将利用生化和分子方法阐明AOS和细胞谷胱甘肽水平的变化在激发子诱导的信号通路中的作用，从而调节PvPRP1和植物保留素途径的mRNA水平。正在研究的实验系统是真菌病原菌与寄主植物(菜豆)之间的相互作用。在更一般的水平上，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控。***

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. ***