Yeast adapt to near-freezing temperatures by STRE/Msn2,4-dependent induction of trehalose synthesis and certain molecular chaperones

Virtually nothing is known about the biochemical adaptations in eukaryotic cells that may enhance survival at low temperatures or upon freezing. Here we demonstrate an adaptive response in yeast that is activated below 10degreesC and increases tolerance to low temperatures and freezing. This response involves a dramatic accumulation of the chemical chaperone trehalose and induction of trehalose-synthesizing enzymes (Tps1, Tps2) and certain heat shock proteins (Hsp104, Hsp42, Hsp12, Ssa4). mRNAs for these proteins increase dramatically below 10degreesC and even at 0degreesC. Their expression requires Msn2,4 transcription factors but also involves marked mRNA stabilization. Upon return to 30degreesC, TPS1, TPS2, and HSP104 mRNAs, trehalose levels and tolerance to freezing fall dramatically within minutes. Mutants lacking trehalose or Msn2,4 die more rapidly at 0degreesC and upon freezing. Thus, below WC, yeastshow an adaptive response that sustains viability at low or freezing temperatures, which are commonly encountered in natural environments and laboratory refrigerators.