Figure 2. (A and C) Structure and regulatory output of incoherent and coherent FFL motifs. Four different types (I1-I4 and C1-C4) are depicted, where X and Y refer to transcription factors (black boxes) and small RNAs (gray boxes), respectively. Z reflects target genes of X and Y, modified from Mangan and Alon.⁹ In the case of the RNAIII FFL, Rot stands on one hand for the rot mRNA, repressed by RNAIII, on the other hand for the Rot protein, repressing hla. (B) Schematic picture of the PrrA/PcrZ, RpoE/RybB and PhoP/AmgR mixed incoherent FFLs in R. sphaeroides, E. coli and S. enterica, respectively. (D) Schematic picture of mixed coherent FFLs. The OmpR-based and RNAIII-based FFLs from E. coli and S. aureus, respectively, are depicted.