Isolation of a Receptor for a Fungal-Wall-Derived Eliitor of Phytoalexins

真菌壁源性植保素激发子受体的分离：这项研究的长期目标是从大豆组织中分离和鉴定一种七乙糖苷受体。真菌衍生的B-葡聚糖是一种从真菌中分离得到的B-葡聚糖，在植物和动物中都是各种防御机制的诱导剂或增强剂。从任何来源都没有分离到这种类型的寡糖受体(S)。唯一具有生物活性的B-葡聚糖片段已被纯化为均一组分，并对其结构进行了表征，它是一种在纳摩尔浓度下具有刺激植物抗菌蛋白(抗生素)在大豆组织中积累的活性的七-B-葡萄糖苷。资助初期的具体目标是确定最合适的大豆组织，从中分离活性七糖苷激发子的受体，制备七糖苷激发子的各种衍生物，并比较它们的生物学活性与天然激发子的生物活性。这些衍生物将被用来制备(I)用于配基结合研究的放射性标记激发子，(Ii)用于受体定位和鉴定研究的光亲和标记试剂，以及(Iii)用于受体纯化的亲和层析基质。如果时间允许，激发子衍生物将被用于启动研究，以鉴定植物提取物中可能的受体。植物抗毒素积累被认为在植物抗病中起着重要作用，也是研究植物基因表达调控的一个很好的模式系统。在研究该受体(S)在导致基因表达改变导致植物细胞中植物抗毒素积累的信号通路中所起的作用之前，有必要对该受体进行纯化。这项研究应该会增加我们对植物如何感知入侵微生物以及这种识别如何导致特定植物防御系统激活的理解。

Isolation of a Receptor for a Fungal-Wall-Derived Elicitor of Phytoalexins: The long term goal of the research described in this proposal is the isolation and characterization of a hepta-B-glucoside receptor from soybean tissue. Fungal-derived B-glucans of the type from which the hepta-B-glucoside was isolated are active as inducers or enhancers of a variety of defense mechanisms in both plants and animals. No receptor for oligosaccharide(s) of this type has been isolated from any source. The only biologically active B-glucan fragment that has been purified to homogeneity and structurally characterized is a hepta-B-glucoside that is active at nanomolar concentrations in stimulating phytoalexin (antibiotic) accumulation in soybean tissue. The specific goals for the initial period of funding are to identify the most suitable soybean tissue from which to isolate the receptor for the active hepta-B-glucoside elicitor, to prepare various derivatives of the hepta-B-glucoside elicitor and to compare their biological activity with that of the native elicitor. These derivatives will be used to prepare (i) radiolabeled elicitor for ligand-binding studies, (ii) photo-affinity labeling reagents for receptor localization and identification studies, and (iii) affinity chromatography matrices for receptor purification. Time permitting, the elicitor derivatives will be used to initiate studies to identify putative receptors in plant extracts. Phytoalexin accumulation is believed to play an important role in plant disease resistance and also is an excellent model system for studying the regulation of gene expression in plants. Purification of the hepta-B-glucoside receptor is necessary before studies can be undertaken to identify the role the receptor(s) play in the signal pathway that results in altered gene expression leading to phytoalexin accumulation in affected plant cells. The research should increase our understanding of how plants perceive invasive microorganisms and how the recognition leads to activation of specific plant defenses.