Mechanisms of mRNA Destabilization During the Plant Defense Response

9409089 Mehdy尽管直接和间接的证据表明它是许多基因表达的重要决定因素，但对调节植物mRNA稳定性的分子机制知之甚少。 植物防御反应的特征在于编码富含脯氨酸的蛋白质PvPRP 1、延伸蛋白、β-微管蛋白以及许多未知蛋白质的mRNA的快速丢失。 在这些mRNA中，PvPRP 1 mRNA的下调是目前最好的表征机制。 PvPRP 1 mRNA在激发子处理后不稳定，并且已经鉴定了特异性结合该转录物的蛋白质（PRP-BP）。 RNA结合蛋白的纯化将是一个主要目标，以确定其生物化学性质，包括通过激发子处理的表观翻译后活化和与PvPRP 1 mRNA的相互作用。 此外，纯化的蛋白质的可用性将允许克隆其编码基因和PRP-BP特异性抗体的产生，用于蛋白质的免疫细胞化学定位。 由暴露于病原体引发的最快速的过程之一是活性氧物质（AOS）的显著释放，其被称为氧化爆发。 AOS作为信号中间体诱导植物抗毒素生物合成的可能性受到了广泛的关注。 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尚不清楚。 本研究将使用生物化学和分子生物学方法来阐明AOS的作用和细胞谷胱甘肽水平的变化在诱导剂诱导的信号通路，导致PvPRP 1和植物抗毒素途径mRNA水平的调节。 所研究的实验系统是病原真菌与寄主植物（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. ***