ANTIGENIC GLYCOPROTEINS IN THE TELIOSPORE WALL OF TILLETIA INDICA

We describe the partial characterization of immunoreactive glycoprotei ns in the teliospore wall of Tilletia indica, the causal agent of Karn al bunt of wheat (Triticum aestivum). Proteins from phenol-extracted a nd precipitated spore wall preparations were used as inject antigens t o immunize New Zealand rabbits. Immunoblots of crude preparations of s pore wall proteins probed with anti-T. indica spore wall IgG showed th at the antibodies recognized a 37-43 kDa band present in the spore wal l fraction of T. indica. A weakly immunoreactive band of the same mobi lity was detected in the spore wall of T. barclayana, a closely relate d fungal pathogen and causal agent of kernel smut of rice. The 37-43 k Da poly-peptide could not be detected in the teliospore walls of the r elated fungal wheat pathogens T. controversa and T. tritici. Different ial centrifugation of pulverized T. indica teliospores confirmed that the immunoreactive T. indica polypeptide was primarily localized in a 1500 g spore wall-enriched fraction and not in cytosolic or membrane f ractions of the teliospores. The lectin concanavalin A bound to a 36-4 1 kDa polypeptide of T. indica but not T. barclayana. Treatment of spo re wall proteins with glycosidase enzymes to remove oligosaccharide re sidues revealed that the 37-43 kDa polypeptide of T. indica was compos ed of two distinct immunoreactive polypeptides of lower molecular weig ht than those detected in undigested spore wall protein immunoblots. T he immunoreactivity of the 37-43 kDa T. barclayana protein was lost up on enzymatic deglycosylation. This suggests the cross reactivity betwe en the 37-43 kDa antigen of T. barclayana and T. indica is most likely due to oligosaccharide epitopes common to the glycoproteins. The diff erential reactivity of the deglycosylated proteins comprising the 37-4 3 kDa antigens provides a potential target for development of rapid im munological diagnostic assays for teliospores of different smut pathog ens.