Integrative Model of Oxidative Stress Adaptation in the Fungal Pathogen Candida albicans

Acknowledgments We are grateful to the Ian Fraser Cytometry Centre and our Mass Spetrometry and qPCR Facilities for help with the flow cytometry, glutathione and qRT-PCR assays, respectively. We also thank our many colleagues in the CRISP Consortium and in the medical mycology and systems biology communities for insightful discussions. Funding: This work was supported by the CRISP project (Combinatorial Responses In Stress Pathways), which was funded by the UK Biotechnology and Biological Research Council (www.bbsrc.ac.uk): AJPB, KH, CG, ADM, NARG, MT, MCR. (Research Grants; BB/F00513X/1, BB/F005210/1-2). AJPB and JQ received additional support from the BBSRC (Research Grants; BB/K016393/1; BB/K017365/1). NARG and AJPB were also supported by the Wellcome Trust (www.wellcome.ac.uk), (Grants: 080088; 097377). AJPB was also supported by the European Research Council (http://erc.europa.eu/), (STRIFE Advanced Grant; ERC-2009-AdG-249793). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Cellular modules/sub-modules of the comprehensive reaction network model and their components.

<p>Cellular modules/sub-modules of the comprehensive reaction network model and their components.</p

Perturbation of Redox Potential (ΔE) is a reasonable proxy for oxidative stress sensitivity.

<p><b>(a)</b> Simulated changes in ΔE in <i>C</i>. <i>albicans</i> cells following exposure to 5 mM H₂O₂: wt, wild type (CA372); <i>cap1</i> (JC842); <i>hog1</i> (JC45); <i>cat1</i> (CA1864) and <i>cap1 hog1</i> (JC118) (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0137750#pone.0137750.s010" target="_blank">S7 Table</a>). The dotted line represents -180 mV, above which cells are more likely to enter oxidant-driven cell death pathways [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0137750#pone.0137750.ref058" target="_blank">58</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0137750#pone.0137750.ref059" target="_blank">59</a>]. <b>(b)</b> Experimental determination of percentage survival following exposure of the <i>C</i>. <i>albicans</i> strains to 5 mM H₂O₂: *, P<0.05; **, P<0.01; ***, P<0.001, using an Unpaired t-test.</p

Temporal changes in the levels of (a) active Cap1 (Cap1^A) and (b) <i>TRR1</i> mRNA levels following exposure to 5 mM H₂O₂.

<p>Model simulations are represented by black solid lines (left hand Y-axes), and experimental measurements by blue boxes (three independent experiments; right hand Y-axis). Relative <i>TRR1</i> mRNA levels were measured relative to the internal <i>ACT1</i> mRNA control. Standard deviation was calculated and is shown in the figure.</p

Temporal changes in the levels of stressor, glutathione, glutathione disulphide and thioredoxin following exposure to 5 mM H₂O₂.

<p>Model simulations (black solid lines) are compared with the corresponding measurements based on three independent experiments (blue boxes). <b>(a)</b> Extracellular hydrogen peroxide (H₂O₂^Ex): left hand Y-axis, simulated levels (mM); right hand Y-axis, experimental measurements (percent of initial value). <b>(b)</b> Glutathione (GSH) left hand Y-axis, simulated levels (mM); right hand Y-axis, experimental measurements (mM). <b>(c)</b> Glutathione disulphide (GSSG) left hand Y-axis, simulated levels (mM); right hand Y-axis, experimental measurements (mM). <b>(d)</b> Simulated levels of the oxidised form of thioredoxin (Trx1^Ox). Experimental errors represent standard deviations from at least three measurements.</p

Comprehensive reaction network model of the oxidative stress response in <i>C</i>. <i>albicans</i>.

<p>A description of the modules and sub-modules and the list of components considered in this study are provided in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0137750#pone.0137750.t001" target="_blank">Table 1</a>. The biochemical reactions and system components are presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0137750#pone.0137750.s004" target="_blank">S1</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0137750#pone.0137750.s005" target="_blank">S2</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0137750#pone.0137750.s008" target="_blank">S5</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0137750#pone.0137750.s009" target="_blank">S6</a> Tables. In addition to the biochemical reactions that are marked in this figure, all components of the model are also assumed to undergo a first order decay. See <i>Model Construction</i> for further details.</p