2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

Kafirins are the main storage proteins of sorghum grain and are found in protein bodies in the seed endosperm; gamma-kafirin is a highly disulfide-bound structural protein at the protein body periphery and alpha-kafirin is the major storage protein (~80% of total kafirin). Protein bodies of a high protein digestibility mutant line were previously shown to have remarkably irregular shapes with alpha-kafirin exposed at the periphery. In this study, mutant protein bodies were examined to determine their structural changes during development and whether or not the proteins coalesce in the matrix in the maturing grain. Protein bodies and immunolocalization of alpha- and gamma-kafirins of developing normal and mutant lines at 20, 30 and 40 days after half bloom (DAHB) were examined by transmission electron microscopy. Mutant protein bodies at 20 DAHB already appeared lobed; gamma-kafirin at this stage was dispersed. By 40 DAHB, the matrix was filled with lobed protein body structures that were coalesced in part. At this later developmental stage, gamma-kafirin in the mutant appeared in discrete dark-staining regions. Concentric rings of gamma-kafirin were found in some mutant and normal protein bodies. Coalescing of the alpha-kafirin in maturing grain suggests that this protein could be functional in the processing of sorghum foods, while kafirins in normal lines are not available due to their encapsulation in protein bodies.