Bacterial elicitors and plant signaling in induced systemic resistance.

Plant root colonizing, fluorescent Pseudomonas spp. have been studied for decades for their plant growth promoting properties and their effective suppression of soil borne plant diseases. The modes of action that play a role in disease suppression by these bacteria include siderophore-mediated competition for iron, antibiosis, and induced systemic resistance (ISR). The involvement of ISR is typically studied in systems in which the Pseudomonas bacteria and the pathogen are inoculated and remain spatially separated on the plant, e.g. the bacteria on the root and the pathogen on the leaf, or the use of split root systems. Since no direct interactions are possible between the two populations, suppression of disease development has to be plant mediated. We discuss bacterial traits and the plant signal transduction pathways involved in Pseudomonas mediated ISR, in particular in the model plant Arabidopsis thaliana