Figure 8.

Diagram showing the responses of Arabidopsis to microbial siderophores. Leaf infiltration of iron-free siderophores (CB or DFO) activates the SA-mediated signaling pathway leading to PR1 up-regulation, the basal defense marker PAD4, ferritin accumulation via AtFER1, and root iron uptake via IRT1 and FRO2. Up-regulation of IRT1 and FRO2 appeared to be partially repressed by SA. Activation of the SA pathway and AtFER1 up-regulation depends on iron availability to the plant (indicated with dashed arrows). Further details are discussed in the text.