MECHANISM OF TEMPERATURE-INDUCED SYNCHRONY IN TETRAHYMENA PYRIFORMIS. ANALYSIS OF THE LEADING CAUSE OF SYNCHRONIZATION

Abstract

In Tetrahymena pyriformis, the so-called “synchronous rounding” is shown when amino acids-starved cells are exposed to the cyclic temperature-treatment for synchronization. Although no division is seen in this system, the degree of synchrony, time sequence of the underlying change in “synchronous rounding” correspond exactly to those in synchronous division. In addition, the characteristic SH-changes preceding “synchronous rounding” are quite similar to those of synchronous division. Furthermore, the fact that only the supply of amino acids deflects “synchronous rounding” to synchronous division suggests a vital connection of the two systems. It can be concluded, therefore, that both systems have a common mechanism of phasing induced by the heat-treatment.
By scrutinizing “synchronous rounding” in reference to the prerequisites for synchronous division, the following are concluded. (1) The response of the oxidative phosphorylation system to the heat-treatment may be a leading cause of inducing synchrony, and the presumptive regulator enzyme (particularly thermo-labile) must be involved in this metabolic system. (2) Characteristic changes in SH amounts would also have a close connection with the mechanism of phasing. They, however, may depend on the action of the oxidative phosphorylation system. (3) Synthesis of the specific protein after the heat-treatment may not account for phasing itself, but it is sine qua non for synchronous division. (4) Synchronous division may occur only when protein synthesis is superimposed upon the active rhythm of the oxidative phosphorylation system and characteristic SH-changes which are phased by the heat-treatment.