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

本研究的目的是分离和鉴定具有生物活性的七糖苷的受体。用于配体结合研究的放射性标记的七-B-葡萄糖苷激发子，将通过将寡糖与酪胺结合，然后对该结合物进行碘化来制备。已经证实模型七糖苷麦芽七糖可以与酪胺偶联，而且碘标记所需的七-B-葡萄糖苷激发子的结构修饰不太可能影响其激发子活性。还将制备用于受体定位和鉴定研究的光亲和标记试剂。将使用标准的细胞分离技术、配体结合分析和光亲和标记来鉴定和定位七-B-葡萄糖苷激发子的受体(S)。如果确定了激发子受体，将对其进行纯化和鉴定。拟议的实验将为未来的研究奠定基础，以确定受体(S)的生理意义，并确定受体(S)在导致基因表达变化的信号通路中所起的作用，进而导致在受影响的植物细胞中积累植物保留素。真菌衍生的B-葡聚糖，从其分离出活性七-B-葡萄糖苷的类型，是植物中多种防御机制的诱导剂或增强剂。唯一具有生物活性的B-葡聚糖衍生片段已经纯化到均一状态并进行了结构鉴定，它是一个七-B-葡萄糖苷激发子。七-B-葡萄糖苷激发子诱导植物保留素的积累是研究植物寡糖受体结构和功能的一个很好的模型系统，因为寡糖配体的完整结构已经确定，并且关于植物中诱导转录的基因已经有了大量的信息。低聚糖结合后的细胞。拟议中的研究，如果成功，将在植物中特别重要，因为植物调节分子的受体还没有被提纯和表征。

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.***//