Figure 3

The effects of the regulatory parameters on the geometry of the nullclines. In (a) we show the impact of positive (grey area) or negative (white area) regulation of G _Z by Y. The geometrical effect associated to β^Yis the only independent of presence of input. In (b) we depict input-dependent effects associated to other regulatory parameters. Nullcline (5) shifts are related to the regulatory interaction of X upon G _Y . The orange line represents the qualitative location for α^X> 1, in brown the location for α^X< 1 is shown. Similarly, the crossing point of nullcline (6) with the vertical axis is shifted to higher (blue) or lower values (green) depending on the type of regulation by β^X.