Synthesis of salt-soluble proteins in barley. Pulse-labeling study of grain filling in liquid-cultured detached spikes.

The accumulation of salt-soluble proteins in the endosperm of developing barley (Hordeum vulgare L.) grains was examined. Detached spikes of barley were cultured at different levels of nitrogen nutrition and pulse-labeled with [(14)C] sucrose at specific times after anthesis. Proteins were extracted from isolated endosperms and separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and crossed immunoelectrophoresis. Fluorography revealed an early, middle and late synthesis of specific proteins during grain filling. Synthesis of proteins appearing at the later stages responded to increased nitrogen nutrition. Two major components, β-amylase and protein Z in particular, had a synthesis profile almost identical to that of the endosperm storage protein, hordein.