106. Abstract
Protoplasts of Boergesenia forbesii
(Hanvey) were treated with inhibitors of protein synthesis in
order to investigate their effects on cellulose synthesis. Cellulose
synthesis was reversibly inhibited by 10 M 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 M 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 signifi-cant turnover, but that there may
exist an essential proteinaceous component of cellulose synthesis
which must be continually renewed.