Relationships between Grain Hardness and the Contents of Prolamin and Three Anti-fungal Proteins in Sorghum

Abstract

Abstract The contents of three anti-fungal proteins of Mr 18k, 26k and 30k were determined by enzyme-linked immunosorbent assay (ELISA) for 40 cultivars of sorghum that varied in grain hardness and prolamin content. Statistically significant relationships were observed between the contents of the anti-fungal proteins and prolamin content, particularly for the Mr 18k (r=0·64) and 30k (r=0·73) proteins. Analysis of hard and soft portions of two cultivars shared that the Mr 18, 26 and 30k proteins were present at a higher level in the corneous endosperm than in the floury endosperm. Immunofluorescence microscopy, using antisera raised in rabbits against these proteins, revealed that the anti-Mr 18k antiserum reacted primarily with the protein bodies and along the cell walls, where the protein bodies are concentrated. Labelling was also more intense in the outer than in the inner endosperm. The Mr 26k protein was associated primarily with the cell walls and not with the protein bodies. The peripheral endosperm was labelled to the greatest extent as detached by immunofluorescence. No fluorescence was observed for the Mr 30k protein. The results indicate a locational and quantitative link between the sorghum prolamins and anti-fungal proteins. This may be due to common genetic modulation or linkage.