The Dynamical Systems Properties of the HOG Signaling Cascade
Figure 5
Schematic representation of the Hog pathway models of Mettetal et al. [10] and Zi et al. [15]. Pictures are redrawn from original figures of these papers. Top: (a) Diagrammatic representation of Mettetal’s model. Au(t) represents the osmolarity applied at time and the variables and can be identified with the intracellular glycerol concentration and the enrichment of Hog1 in the nucleus. The model contains a feedback depending on Hog1p (with strength β) and one, which is independent of Hog1p (strength α). The equations for this model read and . (b) The same model, interpreted in biological terms. The export of osmolytes is regulated by a mechanism, which does not depend on the MAPK pathway (e.g., closure of Fps1p) and by a mechanism depending on Hog1p activation. (c) Diagram of the model structure proposed by Zi et al. The model includes a simplified version of the MAPK pathway as well as two different feedbacks induced by activated Hog1p (a slow transcriptional and a fast nontranscriptional). Both of these feedbacks act by increasing the production of glycerol.
