Subcellular localization of the Phytophthora infestans RXLR effector AVR1 and its corresponding resistance protein R1

Phytophthora infestans causes late blight disease on potato and tomato. It secretes hundreds of effectors that modulate host cellular processes to promote colonization. Well known are the RXLR effectors that are translocated into host cells and often play dual roles. On the one hand they manipulate the host cell machinery to facilitate pathogen colonization; on the other hand, when recognized by a corresponding host resistant protein, they trigger effector-triggered immunity (ETI). The mechanisms underlying ETI are poorly understood. This study focused on the RXLR effector AVR1 and its corresponding resistance protein R1, and addressed the question in which subcellular compartment effector perception and plant defence activation takes place. We investigated the subcellular localization of both R1 and AVR1. Fusing nuclear localization/export signals and mutated versions of these signals to R1 and AVR1 allowed us to target R1 and AVR1 to different subcellular compartments. In this way we determined the subcellular localizations that are required to elicit R1-mediated immunity and AVR1-suppressed host defence responses.