SDS-PAGE analysis of starch granule and soluble extracts from the endosperm of the wheat cv Wyuna. Each lane was loaded with the protein extracted from 5 mg of starch (starch granule extracts) or 20 μg of protein from soluble extracts. A, Lane 1, molecular mass markers; lane 2, silver-stained wheat SGPs; lane 3, activity stain of wheat SGPs. B, Lane 1, silver-stained protein standard ladder; lane 2, silver-stained wheat endosperm SGPs; lanes 3 to 14, immunoblots of SDS-PAGE gels loaded with either soluble extracts (lanes 3–8) or protease-treated starch granules (lanes 9–14). Samples were collected at different stages of endosperm development: 5 DPA (lanes 3 and 9), 7 DPA (lanes 4 and 10), 9 DPA (lanes 5 and 11), 13 DPA (lanes 6 and 12), 16 DPA (lanes 7 and 13), and 24 DPA (lanes 8 and 14). Occasional cross-reactivities of the monoclonal antibody with proteins of molecular mass lower than 100 kD were observed; however, these cross reactivities were not reproducible (unlike the consistent immunoreactivity of the 100-kD proteins) and are therefore considered to be nonspecific interactions.