Multiphasic adaptation of the transcriptome of Saccharomyces cerevisiae to heat stress

Abstract The genome-wide transcriptional response of Saccharomyces cerevisiae to a temperature shift from 28 °C to 41 °C – a temperature at which cell viability was not impaired, but growth rate was – was determined over a period of 6 h under well-controlled conditions. Care was taken not to introduce other perturbations. The data shows that the cells respond by rapidly changing their gene expression. Two phases were observed in this response: A short term transitional response during the first hour in which cell growth ceased, followed by a transcriptionally stable phase that was growth permissive. The initial response was broadest, involving almost half of all the ORFs being induced or repressed to a statistically significant level (here 1.5 fold). Functional analysis showed that genes involved in energy transduction, including trehalose metabolism, and molecular-chaperone encoding genes were induced most prominently. The latter set of genes presumably functions to counteract the effect of the temperature increase on protein denaturation. Furthermore, genes encoding parts of the translation- and transcription systems were repressed temporarily, in line with the observed lag phase in growth. After the initial adaptation phase a new stable state of gene expression was attained, compatible with cell growth. This new transcriptome was characterised by a continued induction of stress response genes, except for those involved in trehalose biosynthesis and a normalisation of the expression of genes coding for the transcription and translation machinery. Finally, our data, together with information available from the literature, show that the adaptation of specific cellular processes to severe temperature stress can occur at different hierarchical control levels. While trehalose metabolism seems to be adjusted mainly at the transcriptional level, the metabolic or post-transcriptional level seems to be more significant for the adaptation of parts of glycolysis and respiration.