Evidence for the Presence of the Toxin-Binding Protein on the Plasma Membrane of Sugarcane Cells

Helminthosporoside is a host-specific toxin produced by Helminthosporium sacchari, both in culture and in infected sugarcane tissue. The susceptibility of any given clone of sugarcane to disease is invariably associated with the presence of a toxin-binding protein. This report presents evidence for the presence of the toxin-binding protein on the plasma membrane of the plant cell. This evidence includes, among others: (1) The protection of susceptible plant tissues by prior treatment with antiserum to the binding protein, (2) the successful pyridoxylation and reduction of the binding protein in vivo followed by its isolation, (3) the reaction of sugarcane cells and free protoplasts with [(3)H]antiserum prepared against the binding protein, and (4) the agglutination of sugarcane protoplast preparations with antiserum to the binding protein.