Ir. K. (Klaas) Bouwmeester: The interplay between a Phytophthora RXLR effector and an Arabidopsis lectin receptor kinase

Phytophthora infestans – the causal agent of potato late blight – secretes a plethora of proteins to facilitate plant infection. One of these is IPI-O, a protein that triggers a resistance response on potatoes carrying the Rpi-blb1 resistance gene. Most P. infestans isolates are unable to infect Rpi-blb1 plants due to recognition of specific IPI-O variants by Rpi-blb1. Two isolates that were found to infect Rpi-blb1-potatoes lack these variants and thus escape recognition. Profiling ipiO variation in the P. infestans population could therefore be used to predict the effectiveness of Rpi-blb1-mediated potato resistance in the field.

IPI-O contains a RGD adhesion motif that binds LecRK-I.9, an Arabidopsis lectin receptor kinase. LecRK-I.9 mediates the cell wall-plasma membrane continuum (CW-PM) of the plant cell. IPI-O can disrupt this continuum by virtue of its RGD motif. We observed that both Arabidopsis lines expressing ipiO and LecRK-I.9 knock-out lines display a destabilized CW-PM continuum, less callose deposition, and loss of Phytophthora resistance. Arabidopsis and potato plants that overexpress LecRK-I.9 were shown to gain Phytophthora resistance. These results strongly suggest that LecRK-I.9 is a novel resistance component in defense against Phytophthora.