Polypeptide Signaling in Plants: Structure, Function, Evolution and Mechanism of Action of Systemin and Its Precursor, Prosystemin

本研究的目的是了解200个氨基酸的激素原蛋白（prosystemin）的合成和储存的基本过程，以及18个氨基酸的多肽激素（systemin）的加工、释放和接受机制，该激素是由原系统蛋白衍生的，以应对食草动物的攻击。将鉴定合成原系统素的特定细胞类型，并确定其细胞间或细胞内储存的位置。研究损伤引起原系统素加工和释放系统素的机制，并开展特异性新型加工酶的研究。将对加工酶进行纯化和表征。系统素在番茄植株中的运输方式将被研究，其在靶细胞中的接受机制将在生化和亚细胞水平上进行研究。系统蛋白激活的全谱蛋白将被鉴定、纯化和克隆。在大肠杆菌表达系统中产生的原系统蛋白将以毫克为单位产生，以确定其三维结构，并将结构特征与其储存和加工联系起来。利用原系统蛋白抗体、cDNA杂交分析和PCR分析，系统地寻找整个植物界中原系统蛋白同源物的发生。原系统素和系统素在系统激活除番茄外的其他植物防御基因中的作用将被进一步研究。将研究从原系统蛋白中衍生出系统素以外的多肽激素的可能性。系统素是迄今为止唯一在植物中发现的肽激素。它在植物防御昆虫和其他侵害方面起作用。这项研究将有助于我们对植物在其生命周期中如何应对压力的基本理解。

9601099 Ryan The objective of this research is to understand the fundamental processes involved in the synthesis and storage of the 200 amino acid prohormone protein, prosystemin, and the mechanisms of processing, release and mode of reception of the 18 amino acid polypeptide hormone, systemin, that is derived from prosystemin in response to wounding by herbivore attacks. The specific cell types in which prosystemin is synthesized will be identified and the sites of its inter- or intracellular storage will be established. The mechanism by which wounding causes processing and release of systemin from prosystemin will be studied, and research to identify the specific novel processing enzymes will be carried out. The processing enzymes will be purified and characterized. The mode of transport of systemin in tomato plants will be investigated and the mechanism(s) of its reception in target cells will be studied at the biochemical and subcellular levels. The full spectrum of proteins that are activated by systemin will be identified, purified and cloned. Prosystemin protein, produced in an E. coli expression system, will be produced in mg quantities to determine its three dimensional structure, and to relate the stuctural features to its storage and processing. The occurrence of prosystemin homologs throughout the plant kingdom will be systematically sought using prosystemin antibodies, cDNA hybridization analyses, and PCR analyses. The role of prosystemin and systemin in systemically activating defense genes in plant species other than tomato will be studied. The possiblity that polypeptide hormones other than systemin may be derived from the prosystemin protein will be examined. Systemin is the only peptide hormone identified in plants to date. It has a role in plant defense against insects and other insults. This research will contribute to our fundamental understanding of how plants cope with stresses that they encounter during their life cycle.