Isolation of a Receptor for a Fungal Wall Derived Elicitor of Phytoalexins

本研究的目的是分离和表征具有生物活性的庚- b -葡萄糖苷的受体。一种用于配体结合研究的放射性标记的庚- b -葡萄糖苷激发子，将通过将寡糖与酪胺偶联，然后对偶联物进行碘化制备。已经确定了一种模型七葡糖苷，麦芽糖七葡糖苷，可以与酪胺结合，而且，用碘进行放射性标记所需的七葡糖苷激发子的结构修饰不太可能影响其激发子的活性。还将准备用于受体定位和鉴定研究的光亲和标记试剂。hepta- b -葡萄糖苷激发子的受体将通过标准细胞分离技术、配体结合测定和光亲和标记进行鉴定和定位。如果确定了激发子受体，将对其进行纯化和表征。提出的实验将为未来的研究奠定基础，以确定受体的生理意义，并确定受体在导致基因表达改变的信号通路中所起的作用，进而导致受影响的植物细胞中植物抗毒素的积累。真菌衍生的b -葡聚糖是植物多种防御机制的诱导剂或增强剂，其中活性庚- b -葡糖苷是从真菌中分离出来的。唯一具有生物活性的b -葡聚糖衍生片段已被纯化到均匀性和结构特征是一个七- b -葡聚糖激发子。hepta-B-glucoside激发子诱导植物抗毒素积累是研究植物低聚糖受体结构和功能的一个很好的模型系统，因为我们已经确定了低聚糖配体的完整结构，并且对植物细胞中诱导转录的基因也有了相当多的了解结合低聚糖。这些研究如果成功，将在植物中具有特别重要的意义，因为调控分子的植物受体尚未被纯化和表征

The objective of this research is to isolate and characterize the receptor for a biologically active hepta-B-glucoside. A radiolabeled hepta-B-glucoside elicitor, for use in ligand- binding studies, will be prepared by conjugation of the oligosaccharide to tyramine, followed by iodination of the conjugate. It has been established that a model heptaglucoside, maltoheptaose, can be conjugated to tyramine and furthermore, that the structural modifications of the hepta-B-glucoside elicitor required for radiolabeling with iodine are unlikely to affect its elicitor activity. A photoaffinity labeling reagent for receptor localization and identification studies will also be prepared. The receptor(s) for the hepta-B-glucoside elicitor will be identified and localized using standard cell fractionation techniques, ligand-binding assays, and photo-affinity labeling. If an elicitor receptor is identified, it will be purified and characterized. The proposed experiments will lay the groundwork for future studies to determine the physiological significance of the receptor(s) and to identify the role the receptor(s) play in the signal pathway that results in altered gene expression leading, in turn, to phytoalexin accumulation in affected plant cells.%%% Fungal-derived B-glucans, of the type from which the active hepta-B-glucoside was isolated, are active as inducers or enhancers of a variety of defense mechanisms in plants. The only biologically active B-glucan-derived fragment that has been purified to homogeneity and structurally characterized is a hepta-B-glucoside elicitor. Induction of phytoalexin accumulation by the hepta-B-glucoside elicitor is an excellent model system for the study of the structure and function of oligosaccharide receptors in plants because the complete structure of the oligosaccharide ligand has been determined and considerable information is known about the genes whose transcription is induced in plant cells upon binding of the oligosaccharide. The proposed studies, if successful, will be particularly important in plants, since plant receptors for regulatory molecules have not yet been purified and characterized.***//