Synchronous growth and synthesis of macromolecules in a naturally wall-less volvocale,Dunaliella bioculata

Summary Dunaliella bioculata, a naturally wall-less unicellular green alga, can be induced to divide synchronously when subjected to a 12 hours light-12 hours dark cycle. This rhythmic cell division will last for at least 15 days under a subsequent constant illumination. Synchronization can be improved when cells are submitted to 8 hours light-16 hours dark cycles under bright white light (10,000 lux). In these conditions the cell division gives rise to two daughter cells: The chronology of DNA, RNA and proteins synthesis has been studied during such a synchronized cell cycle. DNA synthesis begins 4 hours before the outset of cell division and is completed after two hours in the dark; in difference, illumination seems necessary to the synthesis of RNA and proteins.