Abstract
To promote infection, the rice phytopathogen fungus Magnaporthe oryzae secretes proteins, called effectors, which will interfere with cellular process in the host. The recognition of some of them (avirulence effector, or Avr) by the plant immune receptors, named resistance proteins (R), induces the resistance.This thesis has allowed the structural characterisation, by Nuclear Magnetic Resonance, of two Avr-effectors proteins of Magnaporthe oryzae, AVR1-CO39 and AVR-Pia. Although very different in term of their primary sequences, the unexpected discovery that they share a similar fold with AVRPizt, another M.oryzae effector, and ToxB, a toxin of the wheat pathogen Pyrenophora tritici-repentis, allow us to highlight an effector family named MAX-effector (M. oryzae Avrs and ToxB) mostly found inM.oryzae et M.Grisea.At the same time, we investigated the interaction between AVR-Pia and the « integrated decoy » domain RATX1 from RGA5. The structure of AVR-Pia-H3, an inactive allele of AVR-Pia which has lost binding to RATX1, was determined by NMR. These interactions were characterized by calorimetry and the binding surface of RATX1 on AVR-Pia was determined by NMR. In planta studies of AVR-Piamutants and various RGA5 domains in rice show that even if the RATX1 domain is necessary, it is not the only RGA5 domain involved in the effector recognition