Cold response in<i>Saccharomyces cerevisiae</i>: new functions for old mechanisms

The response of yeast cells to sudden temperature downshifts has received little attention compared with other stress conditions. Like other organisms, both prokaryotes and eukaryotes, in Saccharomyces cerevisiae a decrease in temperature induces the expression of many genes involved in transcription and translation, some of which display a cold-sensitivity phenotype. However, little is known about the role played by many cold-responsive genes, the sensing and regulatory mechanisms that control this response or the biochemical adaptations at or near 0 degrees C. This review focuses on the physiological significance of cold-shock responses, emphasizing the molecular mechanisms that generate and transmit cold signals. There is now enough experimental evidence to conclude that exposure to low temperature protects yeast cells against freeze injury through the cold-induced accumulation of trehalose, glycerol and heat-shock proteins. Recent results also show that changes in membrane fluidity are the primary signal triggering the cold-shock response. Notably, this signal is transduced and regulated through classical stress pathways and transcriptional factors, the high-osmolarity glycerol mitogen-activated protein kinase pathway and Msn2/4p. Alternative cold-stress generators and transducers will also be presented and discussed.