Figure 12.

Schematic overview on the interactions of X. campestris pv. campestris and C. annuum analyzed in this work. A major plant cell wall component is pectate, a polygalacturonide (PGA). Pectate is perceived by X. campestris pv. campestris by means of the TonB system. ExbD2, which is not required for ferric iron uptake, is essential for this process. This induces extracellular pectate lyase activity, resulting in the generation of OGAs. Extracellular OGAs consisting of at least 8 galacturonate residues are recognized by C. annuum as a DAMP, resulting in the initiation of defensive measures like an oxidative burst reaction. The presence of a PRR similar to WAK1 is supposed for C. annuum. WAK1 has been identified recently in A. thaliana as a receptor that specifically perceives OGAs [23].