Yeast: Role of ZRT1 and ZRT2 and ZAP1 feedback.

<p>A, contributions of ZRT1 or ZRT2 to the total zinc influx for varying external zinc concentration. B, ZAP1 activity for varying values of ZRT independent influx . The stable solution is marked with a solid line, the unstable solution is dotted.</p

Yeast: parameters.

<p>Parameters values and standard deviations obtained by fitting the model to measurements published in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037193#pone.0037193-Zhao2" target="_blank">[15]</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037193#pone.0037193-Bird1" target="_blank">[21]</a>.</p

Plant roots: parameters.

*<p>Value for ZIP1, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037193#pone.0037193-Grotz1" target="_blank">[28]</a>;</p>†<p>;</p>‡<p>.</p><p>Plant roots: parameters used in the simulation of the <i>activator only</i>, <i>dimerized activator</i> and the <i>dimerized activator-inhibitor</i> models.</p

Yeast simulations.

<p>Comparison between measurements and simulated steady states of ZAP1, internal zinc, ZRT1 and ZRT2 for varying external zinc concentration. Measurements: ZRT1 and ZRT2 from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037193#pone.0037193-Bird1" target="_blank">[21]</a>, ZAP1 and zinc from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037193#pone.0037193-Zhao2" target="_blank">[15]</a>.</p

Plant roots: Robustness and stability.

<p>Robustness and stability of the activator-inhibitor model for (dash-dotted), (solid) and (dashed) and varying external zinc concentration. A, real part of largest eigenvalue. B, internal zinc concentration. Minimal and maximal values of limit cycle shown for unstable steady state ().</p

Plant roots: Steady states of the different regulation models.

<p>The model are: activator only (dash-dotted), dimerizing activator (dashed) and activator-inhibitor pair with dimerization (solid). Measurements of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037193#pone.0037193-Talke1" target="_blank">[17]</a> are also shown.</p

Plant roots: Activator-Inhibitor model with dimerization.

<p>A, steady state values of inhibitor (solid), activator (dashed) and gene activity (dash-dotted) in dependence of internal zinc concentration. B, steady state gene activity in dependence of internal zinc status for varying . Dashed curve corresponds to the nominal .</p

Plant roots: Scheme of the three models of zinc uptake regulation.

<p>A, Activator only [Eq. (9)], B, Activator with dimerization [Eq. (15)], C, Activator-Inhibitor model [Eq. (16)].</p

Yeast: scheme of zinc influx regulation model.

<p>ZAP1 is inactivated by zinc and activates transcription of the transporters ZRT1 and ZRT2.</p