Figure 4.

Boolean representation of signaling network The binary switches used to represent allele status at the NPR1 and NDR1 loci were rendered according to standard depictions in engineering texts. All other symbols are according to Genoud, Trevino Santa Cruz and Métraux [24]. Signal generators were rendered as rectangles with black boxes inside them set at one or zero. "Or" gates, indicating that either input is sufficient to give the specified output, were rendered as bullet shapes with concave left sides. "And" gates, indicating that both inputs are required to give the specified output, were rendered as bullet shapes with flat left sides. Signaling outputs that also serve as inputs to downstream events were rendered as open triangles. Branches in the pathway were indicated with filled circles to suggest the resemblance to contact points in electrical circuit diagrams.