Independent Mechanisms for Acquired Salt Tolerance versus Growth Resumption Induced by Mild Ethanol Pretreatment in Saccharomyces cerevisiae

Abstract

Microbes in nature frequently experience “boom or bust” cycles of environmental stress. Thus, microbes that can anticipate the onset of stress would have an advantage. One way that microbes anticipate future stress is through acquired stress resistance, where cells exposed to a mild dose of one stress gain the ability to survive an otherwise lethal dose of a subsequent stress. In the budding yeast Saccharomyces cerevisiae, certain stressors can cross protect against high salt concentrations, though the mechanisms governing this acquired stress resistance are not well understood. In this study, we took advantage of wild yeast strains to understand the mechanism underlying ethanol-induced cross protection against high salt concentrations. We found that mild ethanol stress allows cells to resume growth on high salt, which involves a novel role for a well-studied salt transporter. Overall, this discovery highlights how leveraging natural variation can provide new insights into well-studied stress defense mechanisms.

The dynamic response to hypo‐osmotic stress reveals distinct stages of freshwater acclimation by a euryhaline diatom

“…These differences in timescales have contributed to considerable debate regarding the importance of acute gene expression responses for longer term acclimation in many different experimental systems. In yeast, there is little overlap between genes differentially expressed during acute and chronic high temperatures (Shui et al, 2015), but acute expression changes are probably necessary to potentiate growth acclimation (McDaniel et al, 2018). This discrepancy is also found in plants, where in the context of the Arabidopsis thaliana cold shock, only a small fraction of genes differentially expressed during acute stress play a role in long-term acclimation (Hannah et al, 2005).…”

“…An open question in diatom stress biology is whether different species possess a common, generalized stress response, or whether individual stressors have their own unique responses. General stress responses are hypothesized to play a role in cross‐stress protection in prokaryotic and eukaryotic microbes as well as plants (Berry & Gasch, 2008; McDaniel et al, 2018; Rangel, 2011; Sabehat et al, 1998). Future studies should examine the transcriptomic response of C. cryptica under different stress conditions, and whether hypo‐osmotic stress cross protects against other stressors such as elevated temperature or light.…”

Gene-by-environment interactions influence the fitness cost of gene copy-number variation in yeast

“…ENA genes are also transcriptionally induced by NaCl ( Proft and Serrano 1999 ; Tenney and Glover 1999 ; Ruiz et al . 2003 ), and in fact several studies have observed natural variation in ENA transcriptional regulation ( McDaniel et al . 2018 ; Sirr et al .…”

Strong environmental memory revealed by experimental evolution in static and fluctuating environments

“…Of such multi-hit genes, only five experienced more than five hits ( Table 1 ). These five genes include: ENA1/ENA2/ENA5, which in tandem encode a sodium efflux pump known to be necessary for resuming growth following transfer into high salt 34 and here displayed repeated copy number amplifications during evolution in high salt (18/43 NaCl mutants, 7/27 Glu / NaCl mutants, 4/34 H 2 O 2 / NaCl mutants); additionally, the genes AFT1 and BOL2, part of an iron-sensing and uptake pathway 35,36 , had SNPs in 28/72 mutants evolved in Glu / H 2 O 2 (including heterozygous SNPs). We also assayed 359 mutants for ploidy (Methods), as the DNA barcoding process sometimes induces self-diploidization 3 , categorizing 161/359 mutants as diploid.…”