Host-Pathogen Interactions

The invertase present in the culture fluid of races 1, 2, and 3 of Phytophthora megasperma Drechs. var. sojae A. A. Hildebrand (Pms) were purified until they gave but a single band, whether stained for protein or carbohydrate, after isoelectric focusing in flat bed gels. The sugar compositions of multiple preparations of the purified invertases from each race of this fungal pathogen were determined by quantitative gas chromatography of their alditol acetates. The invertases are composed of about 25% carbohydrate. Mannose and glucosamine make up more than 97% of the carbohydrate portions of the invertases of all three Pms races analyzed, but the ratio of mannose to glucosamine is clearly not the same in each race. The glycosyl linkage compositions of the glucosamine-containing mannans of multiple preparations of the Pms invertases were determined by GC-MS analysis of the partially methylated alditol acetate derivatives. The results of these analyses demonstrate clear quantitative differences between the glycosyl components of the different Pms races. The existence of race-specific carbohydrate structures in the differentially virulent Pms races suggests that these carbohydrates may be involved in determining the specificity of hostpathogen interactions.