Phytoalexins from glycoproteins

Cline and Albershelm (35) suggested that the primary event in activating the biochemical processes leading to increased concentrations of phytoalexins in plants is the binding of ellcltors to receptors in the plasma membrane. Initial evidence for this was reported by Yoshlkawa et al. 36) when they found that soybean membrane preparations bound HC-laminaran (a 8-1,3-glucan elicitor from Phytophthora spp.). The receptor, while not yet characterized, appears to be a protein or glycoprotein. 

The production of phytoalexins in response to microbes requires a mechanism which enables the plant to recognize the invading organism and subsequently leads to the stimulation of phytoalexin synthesis at the site of microbial penetration. Substances of microbial origin which mediate phytoalexin accumulation in plants have been called elicitors(Ref. 2) and it has been shown in several cases that the culture medium of pathogens contained components which elicited phytoalexin accumulation in the pathogen s host (Ref. 3). Studies on the nature of elicitors have resulted in the partial purification and characterization of a number of molecules from different microbial sources. Elicitors have been reported to have a dependence for activity on a polypeptide or protein (Ref. 4), a glycoprotein (Ref. 5), or polysaccharide (Ref. 6) component. 

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