Figure 3.

Evolution pattern of the type III effectors and their host receptors. (A) N-terminal region of AvrPtoB did as the initial protein to suppress FLS2-medated basal defence, and then Fen was evolved by plant to negate basal defence suppression, and activate defence signaling. To counter recognition by Fen and restore basal defence suppression activity, the N-terminal region of AvrPtoB acquired an E3 ligase domain to mediate the degradation of Fen. Finally, Pto was evolved to be invulnerable to AvrPtoB-mediated ubiquitination and subsequent degradation to restore resistance response. (B) HopAB family type III effectors in Pseudomonas syringae were evolved using the terminal re-assortment.