Oomycetes Seek Help from the Plant: Phytophthora infestans Effectors Target Host Susceptibility Factors

Plants have a sophisticated immune system to defend against a wide range of invaders, including insects, nematodes, bacteria, oomycetes, fungi, and viruses. Microbes may manipulate or suppress immunity by delivering effector proteins, either to the inside or outside of plant cells. Much attention has been focused on identifying the targets of effector proteins in the host and on characterizing how effector activities suppress immunity. The best studied effector proteins are bacterial type III effectors (T3Es), many of which target positive regulators of immunity in order to inhibit their activity (Deslandes and Rivas, 2012).