Genomic and functional studies reveal important roles of integrated domains in NLR-immune receptors
T. KROJ (1), D. Ortiz (2), S. Cesari (3) (1) INRA, France; (2) INRA, France; (3) CSIRO, Australia

Recently, we established that in a broad range of plant lineages structurally and functionally diverse protein domains are integrated into nucleotide-binding and leucine-rich repeat domain immune receptors (NLRs) (Kroj et al., New Phytol. 2016). Functional studies suggest that many of these integrated domains (IDs) serve as decoys that mimic true effector targets and sense pathogens by interacting directly with effectors to trigger immunity (Césari et al., Frontiers in Plant Science 2014). To decipher the mode of action of NLRs carrying IDs, we investigate the recognition of the structurally related effectors AVR-Pia and AVR1-CO39 from the blast fungus Magnaphorte oryzae (de Guillen et al., PLoS Pathogens 2015) by the rice NLR pair RGA4/RGA5. We reported previously that AVR-Pia and AVR1-CO39 bind to the RATX1 (related to ATX1 ) ID of RGA5 (Césari et al., Plant Cell 2013; Césari et al., EMBO J. 2014). Using recombinant proteins, we determined the binding affinity and delimited in NMR titration experiments the binding surface in AVR-Pia. AVR-Pia mutants confirmed this interaction surface and pin-pointed amino acids crucial for RATX1-binding and in planta recognition. Additional interactions of AVR-Pia with other parts of RGA5 were identified and further characterized by mutant analysis. The emerging model is that IDs are crucial for effector recognition but that additional interactions outside the ID are also required for the detection of effectors and activation of resistance.

Abstract Number: P17-549
Session Type: Poster