Figure 6.

(A) Interactions of 2 Gierer–Meinhardt systems. In addition to the basic antagonism of the activator and inhibitor morphogens (as used in the single-patch system scenario), the activator substances of different Gierer–Meinhardt systems inhibit each other. Sufficiently strong inhibition between different activator morphogens ensures that patches belonging to distinct systems do not overlap. (B) Simulation of 4 interacting patch systems from a Cx3D simulation. Each system is based on 2 morphogens interacting according to the Gierer–Meinhardt model. Red, green, blue, and purple indicate the concentrations of distinct activator substances. Repulsion constants between activators were chosen to be identical for all of the activator pairs. (C) Multiple patch systems defined by inhibitory substances (same simulation as in Fig. 6B). Red, green, blue, and purple indicate the concentrations of distinct inhibitor types. In contrast to the scenario where patches are defined by the activator substance concentration, here, there is a smooth overlap between patches because there is no mutual inhibition between inhibitory substances. Patch systems are still guaranteed to develop at distinct locations, because the different activator substances compete with each other, such that also the patches of the inhibitor concentrations are at different locations.