Dynamic Transcriptional and Metabolic Responses in Yeast Adapting to Temperature Stress

Understanding the response processes in cellular systems to external perturbations is a central goal of large-scale molecular profiling experiments. We investigated the molecular response of yeast to increased and lowered temperatures relative to optimal reference conditions across two levels of molecular organization: the transcriptome using a whole yeast genome microarray and the metabolome applying the gas chromatography/mass spectrometry (GC/MS) technology with in vivo stable-isotope labeling for accurate relative quantification of a total of 50 different metabolites. The molecular adaptation of yeast to increased or lowered temperatures relative control conditions at both the metabolic and transcriptional level is dominated by temperature-inverted differential regulation patterns of transcriptional and metabolite responses and the temporal response observed to be biphasic. The set of previously described general environmental stress response (ESR) genes showed particularly strong temperature-inverted response patterns. Among the metabolites measured, trehalose was detected to respond strongest to the temperature stress and with temperature-inverted up-and downregulation relative to control, midtemperature conditions. Although associated with the same principal environmental parameter, the two different temperature regimes caused very distinct molecular response patterns at both the metabolite and the transcript level. While pairwise correlations between different transcripts and between different metabolites were found generally preserved under the various conditions, substantial differences were also observed indicative of changed underlying network architectures or modified regulatory relationships. Gene and associated gene functions were identified that are differentially regulated specifically under the gradual stress induction applied here compared to abrupt stress exposure investigated in previous studies, including genes of as of yet unidentified function and genes involved in protein synthesis and energy metabolism.