Cotyledonary Storage Proteins in Pisum sativum. III. Patterns of Accumulation During Development

Abstract

An antiserum raised against proteins from isolated protein bodies of mature pea seeds recognized seven antigenically distinct protein families in cotyledon extracts analysed by crossed immunoelectrophoresis. This antiserum has been used to follow the sequence of appearance and pattern of accumulation of these proteins in peas grown under controlled environmental conditions. One antigen present in mature cotyledons was shown to be a haemagglutinin, one corresponded to legumin, and four distinct, non-crossreacting antigenic species were related to the vicilin series of proteins. Both the number of components detected and the order of their appearance during development were similar in three genotypes examined, but the quantitative representation of legumin relative to other components was genotype-specific. Quantitative differences were observed in the polypeptide composition of the vicilin components responsible for separate antigenic specificities, but qualitative differences were not excluded. During development, similar conspicuous quantitative changes in polypeptide composition, accompanied by a change in mean electrophoretic mobility, occurred amongst the molecules carrying the predominant antigenic determinant related to vicilin (peak 4); again, qualitative differences might also distinguish these components. The antigen responsible for peak 6 contained two major polypeptides distinct from the components of the legumin and vicilin fractions. Peak 6 represented the first fully immunocompetent species to appear during development, but later became quantitatively less significant as the other antigenic species accumuIated. Legumin and the antigen forming peak 6 were first detected immunologically in an apparently incomplete form. These putative precursors disappeared during subsequent development, so that only the corresponding stable precipitin peaks were seen in the immunoelectrophoretic profiles of extracts from mature cotyledons.