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- Title
Characterization of binding proteins that recognize oligoglucoside elicitors of phytoalexin synthesis in soybean.
- Authors
Côté, François; Jong-Joo Cheong; Alba, Rob; Hahn, Michael G.
- Abstract
We are studying the cellular signaling pathway leading to pterocarpan phytoalexin biosynthesis in soybean that is induced by a branched hepta-β-glucoside originally isolated from the mycelial walls of the phytopathogenic oomycete Phytophthora sojae. Our research has focused on the specific recognition of the hepta-β-glucoside elicitor by binding proteins in soybean cells. Elicitor-binding proteins with properties expected of physiological receptors for the hepta-β-glucoside elicitor have been identified in soybean root membranes. These elicitor-binding proteins co-migrate with a plasma membrane marker (vanadate-sensitive H+-ATPase) on linear sucrose density gradients. Binding of a radio-iodinated derivative of the hepta-β-glucoside elicitor by membrane-localized elicitor-binding proteins is specific, reversible, saturable, and of high affinity (Kd ≈ 1 nM). After solubilization with the nonionic detergent, n-dodecylsucrose, the elicitor-binding proteins retain their high affinity (Kd =1.8 nM) for the radiolabeled elicitor and their binding specificity for elicitor-active oligoglucosides. A direct correlation is observed between the ability of oligoglucosides to displace labeled elicitor from the elicitor-binding proteins and the elicitor activity of the oligosaccharides. Thus, the elicitor-binding proteins recognize the same structural elements of the hepta-β-glucoside elicitor that are essential for its phytoalexin-inducing activity, suggesting that the binding proteins are physiological receptors for the elicitor. Current research is directed toward the purification of the hepta-β-glucoside elicitor-binding proteins by using ligand affinity chromatography. Purification and characterization of the hepta-β-glucoside binding proteins are among the first steps toward elucidating how the hepta-β-glucoside elicitor triggers the signal transduction pathway that ultimately leads to the synthesis of phytoalexins in soybean.
- Subjects
BIOSYNTHESIS; PHYTOALEXINS; PHYTOPATHOGENIC microorganisms; CELL membranes; CHROMATOGRAPHIC analysis; PROTEIN binding; PLANT physiology
- Publication
Physiologia Plantarum, 1995, Vol 93, Issue 2, p401
- ISSN
0031-9317
- Publication type
Article
- DOI
10.1111/j.1399-3054.1995.tb02245.x