EVIDENCE FOR A CYCLOHEXIMIDE-SENSITIVE COMPONENT IN BIOLOGICAL CLOCK OF ACETABULARIA

An 8-h exposure to cycloheximide (0.1 .mu.g/ml) delays the phase of the photosynthesis rhythm 6-14 h in individual A. [mediterranea] cells monitored at 25.degree. C, providing the drug is present during the 1st half of a cell''s circadian cycle. Puromycin pulses (50 .mu.g/ml) are like cycloheximide in their effect on phase, but chloramphenicol (100 .mu.g/ml) is ineffective. Protein synthesis on 80S ribosomes provides a necessary component for the biochemical mechanism of circadian regulation in Acetabularia.