FIGURE 1 

Mathematical modelling. (A) Activation part of the trichome patterning model. Solid lines indicate processes that are contained in the final model, whereas dashed lines indicate hypotheses that are rejected during the analysis. Greek letters denote the corresponding rate constants. The active complex (AC) induces the expression of the patterning genes GLABRA1 (GL1), GLABRA2 (GL2), GLABRA3 (GL3) and TRIPTYCHON (TRY). GL1 and GL3 form the active complex by dimerization. GL1, GL3 and TRY are basally expressed, and GL3 and TRY are non-cell autonomous. Basal and AC-regulated expression (green and blue arrows) denote processes that are manipulated in the simulations and experiments. (B) Inhibition part of the trichome patterning model. The three inhibition scenarios characterize how TRY may inhibit the positive feedback described in (A). In the cases of single competitive inhibition, TRY prevents the formation of the active complex by binding to free GL3, whereas in the double competitive inhibition TRY binds additionally to free GL1. In case of uncompetitive inhibition, TRY directly binds to the existing active complex. In all scenarios, the resulting inactive complex is denoted by IC. The full model comprises the interactions shown in (A) and one of the inhibitions given in (B).