Structural and Immunochemical Studies on the Phytotoxic Peptidorhamnomannan of Ceratocystis ulmi

A wilt-inducing peptidorhamnomannan produced by Ceratocystis ulmi, the causative agent in Dutch Elm disease, has been subjected to additional chemical and physical characterization. Gel filtration, reductive beta elimination, hydrofluoric acid deglycosylation, and ultracentrifugation experiments provide evidence that the wilt-inducing polymer is polydisperse with a molecular weight range of approximately 105,000 to 120,000. The carbohydrate portion of each molecule is composed of small percentages of mannose, mannobiose, mannotriose, and a tetra- or pentasaccharide composed of mannose and rhamnose plus a major component consisting of two or three long rhamnomannan chains each with a molecular weight range of 32,000 to 34,000. All saccharide units are attached via O-glycosidic linkages to a protein with a molecular weight of approximately 35,000.Rabbit antibodies directed against both C. ulmi and the purified peptidorhamnomannan have been prepared. Their possible use in evaluating the role of the polymer in the disease is discussed.