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Physiology and Biochemistry

Purification and Partial Characterization of a Glycoprotein Toxin Produced by Cladosporium fulvum. G. Lazarovits, Graduate student, Department of Botany, University of Toronto, Ontario, Canada, M5S 1A1, Present address of senior author: Agriculture Canada Research Institute, University Sub Post Office, London, Ontario, N6A 5B7; B. S. Bhullar(2), H. J. Sugiyama(3), and V. J. Higgins(4). (2)(3)(4)Postdoctoral assistant, technician, and associate professor, respectively, Department of Botany, University of Toronto, Ontario, Canada, M5S 1A1. Phytopathology 69:1062-1068. Accepted for publication 9 March 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-1062.

A heat-stable, high molecular weight toxin isolated from culture filtrates and cell wall preparations of Cladosporium fulvum causes callose formation, host cell necrosis, and ion leakage in tomato leaf tissue. The toxin was purified by a combination of dialysis, methanol precipitation, DEAE-cellulose chromatography, affinity chromatography on concanavalin A-Sepharose 4B, and gel chromatography on Sephadex G-100 and Sepharose 4B. The most highly purified toxin preparations contained both protein and carbohydrate, the ratio ranging from 0.09 to 0.23. Mannose, glucose, galactose, and traces of several unidentified sugars were found in hydrolysates. The importance of the glycosyl moiety to toxin activity was indicated by toxin inactivation after periodate oxidation or treatment with α-mannosidase. Incubation of toxin with proteinase K also reduced activity, but dansylation of the protein did not alter activity. The behavior of the toxin during gel chromatography and electrophoresis suggested it was a heterogenous or polydisperse glycoprotein with a molecular weight range of 3 104 to 2.5 103 daltons.

Additional keywords: tomato leaf mold.