Figure 4.

Some effectors suppress plant immunity. The figure describes the RXLR effector AVR3a of Phytophthora infestans as an example of an effector with dual activities: activation of R gene‐specific hypersensitive cell death and suppression of plant immunity (Armstrong et al., 2005, 2006, 2009). Allelic variants of AVR3a, AVR3a^KI (containing amino acids K⁸⁰ and I¹⁰³) and AVR3a^EM (E⁸⁰ and M¹⁰³) are shown in (a). The experiments involve the expression of FLAG epitope‐tagged versions of both variants (a) in leaves of Nicotiana benthamiana. The two variants have distinct activities in plants. AVR3a^KI but not AVR3a^EM triggers hypersensitive cell death in the presence of the resistance gene R3a (b), and suppresses the hypersensitive cell death induced by another P. infestans protein, INF1 elicitin, a secreted P. infestans protein with features of pathogen‐associated molecular patterns (c). (d) FLAG antisera Western blot of leaf extracts, showing that the two variants are equally stable in planta.