Fig. 4.
Cross-input modulation within the RD29A regulatory system. (a) A cross-input modulation is defined as modulation of a signaling process by the rate pj, by the adjacent, non-cognate input (S′). Regulatory outcome of the cross-input modulation can be by either enhancement (E) or inhibition (I) of pj. We assume that cross-input modulation is delayed by τ, hence the use of dashed lines. (b) Outline of all 18 possible system structures, organized by regulatory outcome (E or I) and the non-cognate input (SNaCl or SABA). The five system structures that reproduce the observed synergistic effect are highlighted in color (red = SNaCl modulates the TF2 pathway; blue = SABA modulates the TF1 pathway).