Abstract
Pathogens deliver a number of effector proteins into plant cells to suppress PAMP (pathogen-associated molecular pattern)-triggered immunity (PTI). Resistant plants are able to recognize the effectors by the resistance (R) proteins and induce strong immune responses. AVR3a, an effector protein secreted from potato blight pathogen Phytophthora infestans, is translocated into plant cells and suppresses PTI induced by the recognition of INF1. However, its underlying mechanism is still unclear. Because the molecular function of AVR3a is not predictable from the amino acid sequences, we performed protein structural analysis. The NMR analysis revealed that AVR3a protein has a positively charged surface area, which is important for binding a phosphatidylinositol phosphate. AVR3a with a point mutation in the area was not able to suppress INF1-induced PTI, although it was still recognized by R3a, a potato R protein. These data suggest that the binding of a phosphatidylinositol phosphate plays an important role for the virulence functions of AVR3a. We will discuss the molecular relationship between the lipid-binding area and the virulence function.
