THE EFFECTS OF SELECTED INHIBITORS ON CELLULOSE MICROFIBRIL ASSEMBLY IN BOERGESENIA FORBESII (CHLOROPHYTA) PROTOPLASTS 1

Protoplasts of Boergesenia forbesii (Harvey) were treated with inhibitors of protein synthesis in order to investigate their effects on cellulose synthesis. Cellulose synthesis was reversibly inhibited by 10 μM cycloheximide as assayed by fluorescence microscopy of Tinopal binding to cellulose. Freeze fracture and image analysis of cycloheximide‐ treated cells indicated a reduction in the number of intramembrane particles; however, the terminal synthesizing complexes remained at all times. Treatment with 10 μM actinomycin D, when applied during the first hour of protoplast formation, irreversibly inhibits cellulose synthesis and terminal complex formation. De novo protein synthesis is required for cell wall regeneration by protoplasts. The data suggest that the structural subunits visualized in the terminal complex do not undergo significant turnover, but that there may exist an essential proteinaceous component of cellulose synthesis which must be continually renewed.