Figure 4. Intra-species robustness of gap gene patterning to perturbations in levels of maternal gradients.

(A) The position of gap gene expression features is relatively robust towards changes in maternal gradient concentrations. This sketch—modified from Figure 1 of Manu et al. (2009b)—shows concentration variation in the maternal Bcd gradient (above) and the zygotic expression domain of Kr (below). Solid line and coloured area indicate averaged expression patterns, dashed lines indicate expression variation. Red arrows show the difference between the range of positional variation in Bcd (red background) and Kr. (B) Phase diagram for AC/DC2 in response to variation in Bcd concentration. Pink dots and error bars show average Bcd concentration with standard deviation between 47 and 61% A–P position. Dashed lines show the maximum range of Bcd profiles in the data. AC/DC2 subcircuits for nuclei indicated by the X-axis, where simulated with Cad concentration fixed to its value at T1, and Bcd concentration fixed to the values given by the Y-axis. Background colour indicates the resulting dynamical regime: the multistable anterior regime is shown in black, the monostable posterior regime in grey. (C) Phase diagram for AC/DC2 in response to variation in Cad concentration. White dots indicate Cad concentrations between 47 and 61% A–P position. AC/DC2 subcircuits for nuclei indicated by the X-axis, where simulated with Bcd concentration fixed to its value at T1, and Cad concentration fixed to the values given by the Y-axis. Background indicates dynamical regime as in (B). See text for details.