LecRK79, a putative virulence target of the RXLR effector IPI-O is involved in cell wall-plasma membrane adhesions and PAMP-triggered immunity

The potato late blight pathogen Phytophthora infestans secretes many RXLR effectors, one of which is IPI-O. In IPI-O the RXLR motif overlaps with the tripeptide RGD (RSLRGD), a typical cell adhesion motif present in extracellular metazoan proteins that play a role in cell-cell interactions. A phage display aimed at selecting proteins that potentially interact with the RGD motif in IPI-O resulted in the identification of Arabidopsis lectin receptor kinase LecRK79 (Gouget et al. 2006, Plant Physiology 140, 81-90). We postulate that LecRK79 is a virulence target of IPI-O. For functional characterization we generated Arabidopsis lines overexpressing LecRK79 (OE lines) or lacking LecRK79 (knock-out lines lecrk79). Infection assays revealed changes in phenotype upon infection with Phytophthora brassicae in both the OE and lecrk79 lines and demonstrate that LecRK79 has a role in Phytophthora disease resistance. To unravel the mechanisms underlying this resistance we analysed callose deposition upon PAMP treatment and investigated the strength of cell wall-plasma membrane adhesions by inducing plasmolysis. The results indicate that LecRK79 plays an important role in the continuum between cell wall and plasma membrane and suggest that this lectin receptor kinase is involved in PAMP-triggered immunity