Protein body formation in the developing barley endosperm

Abstract

The ultrastructure of the pericarp, testa, aleurone and endosperm in a developing barley grain is presented in the form of a reconstructed section cut tangential to the dorsal surface of the grain and extending half way to the center of the endosperm.Protein body formation in the endosperm is examined in Carlsberg II and Bomi barley and two mutants defective in hordein synthesis. Protein bodies of complex morphology are deposited in large as well as small vacuoles. They comprise clusters of homogeneous components, embedded in a fibrillar matrix, associated with electron-dense spheres and numerous vesicles. The fibrillar matrix is interpreted to be a transient stage in the condensation of storage proteins into a homogeneous structure. The polypeptide composition of protein bodies determines their ultrastructure. The reduction in the synthesis of ‘B’ type hordein in mutant Risø 56 increases the proportion of the fibrillar matrix, while a more drastic alteration in storage protein condensation is observed in mutant Risø 1508, which is highly deficient in both ‘B’ and ‘C’ type hordein polypeptides.