Arms race coevolution in rice blast disease: the link between an effector host target and plant immunity through an integrated NLR domain
R. TERAUCHI (1), H. Kanzaki (2), H. Saitoh (2), A. Maqbool (3), K. Yoshida (4), S. Cesari (5), T. Kroj (6), M. Banfield (3), S. Kamoun (7) (1) Iwate Biotechnology Research Center, Japan; (2) Iwate Biotechnology Research Center, Japan; (3) John Innes Centre, United Kingdom; (4) Kobe University, Japan; (5) CSIRO, Australia; (6) INRA, France; (7) The Sainsbury Laboratory, United Kingdom

The Magnaporthe oryzae AVR-Pik effector gene has five alleles that are differentially recognized by alleles of the rice Pik locus carrying the paired NLR genes, Pik-1 and Pik-2 that are both required for resistance (Yoshida et al. Plant Cell 2009, Kanzaki et al. Plant J. 2012). AVR-Pik recognition is mediated by direct binding of the effector to the heavy metal associated (HMA) domain of Pik-1. The crystal structure of the AVR-PikD/Pikp-1-HMA complex has recently been solved (Maqbool et al. eLife 2015), revealing that variable amino acids of AVR-Pik are located at the binding interface. We hypothesize that evolution of the AVR-Pik allelic series was driven by strong selection by Pik-1, and that deletion of AVR-Pik may cause a fitness cost to M. oryzae in rice without cognate Pik. To understand the virulence contribution of AVR-Pik, we carried out a Y2H screen of rice proteins, and identified small proteins containing the HMA domain (sHMAs). Knockdown of sHMA genes in rice reduced susceptibility against compatible isolates of M. oryzae, suggesting that sHMAs are susceptibility (S-) genes required for successful pathogen invasion. sHMAs interact with other rice proteins and contribute to reduction of ROS, and are stabilized by AVR-Pik. We hypothesize that the M. oryzae AVR-Pik effector targets rice sHMAs and co-opts host ROS reduction for its own benefit. This virulence effect was large enough to select a rice lineage having Pik-1 NLR with an integrated HMA domain to trigger resistance.

Abstract Number: P17-626
Session Type: Poster