Kandror et al. investigated the response of yeast to low temperatures and discovered a key role for the disaccharide trehalose (which can act as a chaperone) in tolerance to near-freezing temperatures and freezing. Anyone who has forgotten a perishable item in the back of a refrigerator recognizes that some microorganisms survive (and thrive) at near-freezing temperatures. Although the heat shock response to increased temperatures has been extensively investigated--and "cold shock responses" to temperatures between 10oC and 18oC have been described--little is known about adaptations that allow microorganisms to survive freezing or near-freezing temperatures. Kandror et al. (who previously implicated trehalose in cold adaptation of bacteria) used Northern and Western analysis and [35S]methionine incorporation to demonstrate increases in mRNA and protein for trehalose-6-phosphate synthase and trehalose-6-phosphate phosphatase in cells incubated for many hours at 0oC, despite an overall decrease in protein synthesis. Microarray analysis indicated that amounts of mRNAs of other genes involved in trehalose synthesis, and of several heat shock genes that are not induced at 18oC or 10oC, were also increased. Mutational analysis indicated that the stress-activated Msn2,4 transcriptional activators were required for increased production of the "near-freezing" mRNAs (and were important for survival of freezing and near-freezing temperatures), although temperature shift experiments indicated a role for mRNA stabilization as well. Cell trehalose content increased 25- to 50-fold during sustained exposure to 0oC or 4oC, and mutational analysis indicated that trehalose accumulation at near-freezing temperatures enhanced survival of freezing and that trehalose content was closely correlated with freezing tolerance.
O. Kandror, N. Bretschneider, E. Kreydin, D. Cavalieri, A. L. Goldberg, Yeast adapt to near-freezing temperatures by STRE/Msn2,4-dependent induction of trehalose synthesis and certain molecular chaperones. Mol. Cell 13, 771-781 (2004). [Online Journal]