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Figure 3 | BMC Developmental Biology

Figure 3

From: A mechanism for the sharp transition of morphogen gradient interpretation in Xenopus

Figure 3

Relationship between parameters and threshold values of M. Threshold values are calculated and plotted and colour-coded as indicated. White areas indicate either that a threshold does not exist or that its value is above 5. (A) Threshold values are plotted in parameter plane (ka, kb). α = 6, β = 3, kda = kdb = 1. (B) Setting different values for the decay constants kda and kdb significantly broadens the range of possible parameter values of ka and kb that allows a threshold generation. Degradation constants are set to kda = 1 and kdb = 5. Note that the area in the parameter plane (ka, kb) that allows threshold (coloured area) is shifted and becomes much broader compared to (A). α = 6, β = 3. (C) Threshold values are plotted in parameter plane (α, β). ka = 5.5, kb = 5.4. (D) Steady state values of A and B plotted against M at the black dots in (C). Left panel, (α, β) = (2, 4). Right panel, (α, β) = (5, 2). ka = 5.5, kb = 5.4, kda = kdb = 1. Note that the two areas in (C) where the system is bistable with a threshold shows opposite steady state profiles. When α < β (area 1 in the middle panel in C), A is on and B is off with low M, and vice versa with high M at steady state. When α > β (area 2 in the middle panel in C), B is on and A is off with low M, and vice versa with high M at steady state.

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