Figure 7

Overview of the seven plant-associated specific proteins and its correlation with induction and evasion of the plant immune system. The arrows in black highlight possible activities of these seven enzymes putatively secreted by T2SS. The Nix nomenclature summarizes the activity of enzymes that are part of the whole nix cluster, with particular emphasis on NixE, NixF and NixL. The blue arrows highlight induction of the immune response mediated by DAMP/PTI (mediated by lipase action) and PAMP (mediated by EF-Tu and flagellin), and evasion of immune response induced by ETI (mediated by T3SS effectors). The immune system activation responses (in red) trigger the production of reactive oxygen species (ROS), induction of systemic acquired resistance (SAR) and generation of calloses, necrosis, and programmed cell death (PCD). It is possible that Nix operates in two contexts: in free N-glycans (F-NG) or in N-glycans associated with membrane receptors (EFR and FLS2). The action of Nix proteins could degrade N-glycans that should be linked to these receptors at Golgi and directly degrade N-glycans from receptors on the plant surface. Both byproducts of N-glycans or cell wall degradation may still be used as a carbon source for bacterial metabolism. DAMP: Damage-Associated Molecular Patterns. PTI: PAMP-Triggered Immunity. ETI: Effector-Triggered Immunity.