From START to FINISH : the influence of osmotic stress on the cell cycle

Peer reviewedPublisher PD

Time course activity of cell cycle components upon application of 1 M NaCl at early S phase.

<p>The left vertical axis refers to the concentrations of total Sic1, SBF/MBF, Swe1, Cdc28-Clb2, Cdc28-Clb5, and Hog1PP and the right vertical axis refers to the concentration of the Hsl1-Hsl7 complex. (A) A wild type untreated cell, (B) 1 M NaCl applied during early S phase (at t = 45 min) to a wild type cell causes the cell cycle to last about 76 minutes longer compared to the wild type untreated cell. (C) 1 M NaCl applied to a Δ<i>swe1</i> cell; in this case the cell cycle duration is 62 minutes longer than in an untreated Δ<i>swe1</i> cell. (D) The deletion of Sic1 does not cancel the delay caused by Hog1PP activity. 1 M NaCl applied to a Δ<i>sic1</i> cell prolongs the cell cycle around 52 minutes compared to a Δ<i>sic1</i> untreated cell.</p

The HOG MAPK network rescues the mitotic exit defect of MEN mutants.

<p>(A) A <i>cdc15</i> cell is arrested in M phase and cannot divide. (B) Application of 0.4 M NaCl stimulates the <i>cdc15</i> cell to go through cell division. (C) The <i>cdc14</i> cell can go through the cell division in the presence of 0.4 M NaCl. (D) Removing the interaction of Hog1PP with <i>CLB2</i> does not cancel the cell division of the <i>cdc15</i> cell in the presence of osmotic stress. Note that the <i>cdc15</i> cell upon osmotic stress is able to finish its current cell cycle but gets arrested in the next G2/M phase. (E) The <i>cdc15</i> cell, in which the interaction of Sic1 with Hog1PP is blocked, cannot finish its cell cycle and is arrested in M phase.</p

Differential sensitivities of <i>C</i>. <i>albicans fdh3</i>Δ and <i>glr1</i>Δ cells to hydrogen peroxide, nitric oxide and formaldehyde.

<p><b>(A)</b> Sensitivity to hydrogen peroxide (7.5 mM H₂O₂) and formaldehyde (5 mM CH₂O): wild type (CPK05); <i>glr1</i>Δ (CKS10), <i>glr1</i>Δ+<i>GLR1</i> (CKS31), <i>fdh3</i>Δ (ATT1); <i>fdh3</i>Δ+<i>FDH3</i> (ATT4) (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0126940#pone.0126940.t001" target="_blank">Table 1</a>). <b>(B)</b> Dose-dependent sensitivity to formaldehyde: wild type (CPK05); <i>fdh3</i>Δ (ATT1); <i>fdh3</i>Δ+<i>FDH3</i> (ATT4). <b>(C)</b> Differences in adaptation (inflection) time after nitrosative stress (2.5 mM DPTA NONOate): wild type (CPK05); <i>glr1</i>Δ (CKS10); <i>glr1</i>Δ+<i>GLR1</i> (CKS31); <i>fdh3</i>Δ (ATT1); <i>fdh3</i>Δ+<i>FDH3</i> (ATT4).</p

The metabolic background is a global player in Saccharomyces gene expression epistasis

The regulation of gene expression in response to nutrient availability is fundamental to the genotype–phenotype relationship. The metabolic–genetic make-up of the cell, as reflected in auxotrophy, is hence likely to be a determinant of gene expression. Here, we address the importance of the metabolic–genetic background by monitoring transcriptome, proteome and metabolome in a repertoire of 16 Saccharomyces cerevisiae laboratory backgrounds, combinatorially perturbed in histidine, leucine, methionine and uracil biosynthesis. The metabolic background affected up to 85% of the coding genome. Suggesting widespread confounding, these transcriptional changes show, on average, 83% overlap between unrelated auxotrophs and 35% with previously published transcriptomes generated for non-metabolic gene knockouts. Background-dependent gene expression correlated with metabolic flux and acted, predominantly through masking or suppression, on 88% of transcriptional interactions epistatically. As a consequence, the deletion of the same metabolic gene in a different background could provoke an entirely different transcriptional response. Propagating to the proteome and scaling up at the metabolome, metabolic background dependencies reveal the prevalence of metabolism-dependent epistasis at all regulatory levels. Urging a fundamental change of the prevailing laboratory practice of using auxotrophs and nutrient supplemented media, these results reveal epistatic intertwining of metabolism with gene expression on the genomic scale

Impact of <i>FDH3</i> and <i>GLR1</i> deletion on transcript levels in respose to formaldehyde, oxidative or nitrosative stress.

<p>Transcript levels were quantified by qRT-PCR, relative to the internal <i>ACT1</i> mRNA control after 10 min of stress treatment and normalised to untreated wild type cells: wild type (CPK05); <i>fdh3</i>Δ (ATT1); <i>glr1</i>Δ (CKS10). Stresses were 2.5 mM CySNO (NS), 5 mM CH₂O or 5 mM H₂O₂ (XS). Gene expression was assayed for the following genes: (A) <i>GLR1</i>, (B) <i>FDH3</i>, (C) <i>TRX1</i>, (D) <i>PDI1</i>.</p

Predicted roles for Fdh3 and Glr1 in <i>C. albicans</i>.

<p><b>(A)</b> Predicted roles for Fdh3 and Glr1 in GSNO and GSSG detoxification. <b>A</b> shows the working hypothesis of the major enzymes involved in the detoxification of GSSG (glutathione disulphide) and GSNO (S-nitrosoglutathione). When glutathione (GSH) is oxidised via H₂O₂ to GSSG, GSSG can be reduced with the help of the NADPH-dependent glutathione reductase (GR). We predict that the glutathione reductase of <i>Candida albicans</i> is <i>GLR1</i>. When GSH is exposed to NO, GSH is S-nitrosylated to GSNO. We predict that the S-nitrosoglutathione reductase (GSNOR) of <i>Candida albicans</i> is <i>FDH3</i>. <b>(B)</b> Predicted role for Fdh3 in formaldehyde detoxification. <b>B</b> shows the second enzymatic function of GSNOR the detoxification of formaldehyde. Formaldehyde reacts with glutathione (GSH) to form S-(hydroxmethyl)glutathione which then gets converted by Fdh3 and NAD+ to S-(formyl)glutathione.</p