AN ANALYSIS OF VACUOLE DEVELOPMENT IN OAT ALEURONE PROTOPLASTS

Cultured oat (Avena sativa L. - naked form) aleurone protoplasts were employed as a model system for following changes which accompany the d evelopment of vacuoles during in-vitro incubation. Over a 5-d period, the aleurone grains progressively grew and fused to form a large centr al vacuole and the volume of the protoplasts increased sevenfold. The growth of the vacuole was accompanied by a progressive acidification o f the vacuolar sap. Vacuolation was inhibited by high concentrations o f mannitol and by cycloheximide and cordycepin applied at various time s during the incubation period. Neither cycloheximide nor cordycepin a ffected the initial phases of vacuolation but cycloheximide retarded s ubsequent stages, particularly if added early in the incubation. Cordy cepin inhibited only the later stages of vacuolation. Radiolabelling s tudies identified at least three novel microsomal proteins, with relat ive molecular masses of approximately 34, 47 and 48 kDa, which appeare d during vacuolation and whose synthesis was markedly affected by thes e inhibitors.