Ultradian rhythm of trehalose levels coupled to heat resistance in continuous cultures of the yeast Saccharomyces cerevisiae

Heat resistance appears to cycle in concert with energy metabolism in continuous culture of the yeast Saccharomyces cerevisiae. To study the mechanism of this oscillation, the authors first examined if heat shock proteins (Hsps) are involved. Neither the protein levels of major Hsps nor the expression of the β-galactosidase gene as a reporter under the control of the promoter carrying heat-shock element oscillated during the metabolic oscillation. The level of trehalose in yeast cycled with the same periodicity, as did energy metabolism. This oscillation was not found in a GTS1-deleted mutant that also did not show cyclic changes in heat resistance. These results suggest that heat resistance oscillation is induced by fluctuations in trehalose level and not by an oscillatory expression of Hsps. The increase in trehalose began at the start of the respiro-fermentative phase and the decrease began after the elevation of the cyclic adenosine monophosphate (cAMP) level. The authors hypothesize that the synthesis of trehalose parallels the activation of the glycolytic pathway and that trehalose is degraded by trehalase activated by cAMP coupled with the metabolic oscillation in the continuous culture of yeast.