The Rice Resistance Protein Pair RGA4/RGA5 Recognizes the Magnaporthe oryzae Effectors AVR-Pia and AVR1-CO39 by Direct Binding

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Cesari, S. | Thilliez, G. | Ribot, C. | Chalvon, V. | Michel, C. | Jauneau, A. | Rivas, S. | Alaux, L. | Kanzaki, H. | Okuyama, Y. | Morel, J.-B. | Fournier, E. | Tharreau, D. | Terauchi, R. | Kroj, T.

Edité par CCSD ; American Society of Plant Biologists (ASPB) -

BGPI : équipe 4/5. International audience. Resistance (R) proteins recognize pathogen avirulence (Avr) proteins by direct or indirect binding and are multidomain proteins generally carrying a nucleotide binding (NB) and a leucine-rich repeat (LRR) domain. Two NB-LRR protein-coding genes from rice (Oryza sativa), RGA4 and RGA5, were found to be required for the recognition of the Magnaporthe oryzae effector AVR1-CO39. RGA4 and RGA5 also mediate recognition of the unrelated M. oryzae effector AVR-Pia, indicating that the corresponding R proteins possess dual recognition specificity. For RGA5, two alternative transcripts, RGA5-A and RGA5-B, were identified. Genetic analysis showed that only RGA5-A confers resistance, while RGA5-B is inactive. Yeast two-hybrid, coimmunoprecipitation, and fluorescence resonance energy transfer-fluorescence lifetime imaging experiments revealed direct binding of AVR-Pia and AVR1-CO39 to RGA5-A, providing evidence for the recognition of multiple Avr proteins by direct binding to a single R protein. Direct binding seems to be required for resistance as an inactive AVR-Pia allele did not bind RGA5-A. A small Avr interaction domain with homology to the Avr recognition domain in the rice R protein Pik-1 was identified in the C terminus of RGA5-A. This reveals a mode of Avr protein recognition through direct binding to a novel, non-LRR interaction domain.

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