The memory of hyperosmotic stress response in yeast is modulated by gene-positioning

Abstract

words/175) 18Cellular memory is a critical ability displayed by microorganisms in order to adapt to potentially detrimental 19 environmental fluctuations. In the unicellular eukaryote S. cerevisiae cellular memory can take the form of a 20 faster or a decreased response following repeated stresses in cell population. Using microfluidics and 21 fluorescence time-lapse microscopy, we studied how yeasts respond to short-pulsed hyperosmotic stresses at 22 the single-cell level by analyzing the dynamical behavior of the stress responsive STL1 promoter fused to a 23 fluorescent reporter. We established that pSTL1 shows variability in its successive activations following two 24 repeated short stresses. Despite this variability, most cells displayed a memory of past stresses through a 25 decreased activity of pSTL1 upon repeated stress. Notably, we showed that genomic location is important for 26 the memory effect since promoter displacement to a pericentromeric chromatin domain leads to a decreased 27 transcriptional strength of pSTL1 and to the loss of memory. This study provides a quantitative description of a 28 cellular memory that includes single-cell variability and points towards the contribution of the chromatin 29 structure in stress memory. 30 31

Learning of Signaling Networks: Molecular Mechanisms

“…The 3-dimensional chromatin structure also plays an important role in cellular learning. Sensitization to hyperosmotic stress was abrogated if the reporter gene was placed to a pericentromic chromatin domain in yeast cells [9]. Nup2-mediated association of the INO1 and GAL1 genes with the nuclear pore complex and histone modifications led to the rapid reactivation of INO1 and GAL1 genes after a repeated signal.…”

“…Importantly, cellular learning can also result in the repression of a response. In budding yeast cells, the STL1 sugar transporter gene showed a reduced expression to the second hyperosmotic stress as compared to the first [9]. In Arabidopsis, a sub-set of MYC-dependent genes related to multiple abiotic and hormone response networks did not respond to repeated dehydration stress [10].…”