Heavy metal-associated domain (HMA) proteins of rice confer susceptibility to Magnaporthe oryzae and are targeted by M. oryzae effector AVR-Pik
H. KANZAKI (1), H. Saitoh (1), S. Cesari (2), K. Fujisaki (1), E. Kanzaki (1), K. Yoshida (3), T. Takeda (1), K. Ito (1), C. Mitsuoka (1), A. Hirabuchi (1), M. Banfield (4), T. Kroj (5), S. Kamoun (6), R. Terauchi (1) (1) Iwate Biotechnology Research Center, Japan; (2) CSIRO Plant Industry, Australia; (3) Kobe Univ. Laboratory of plant Genetics, Japan; (4) John Innes Centre, Japan; (5) INRA, UMR BGPI, France; (6) The Sainsbury Laboratory, United Kingdom

Heavy metalassociated (HMA) domains can be identified in a family of small proteins of rice. Interestingly, HMA domains also occur as integrated domains in two rice NLR proteins, RGA5 and Pik-1, that recognize sequence-divergent but structurally conserved effectors from the rice blast pathogen Magnaporthe oryzae. Here we examined the role of small HMA-containing proteins (sHMAs) in rice. Using a Y2H approach, we show that the M. oryzae cytoplasmic effector AVR-Pik interacts with sHMAs. Knockdown of sHMA genes in rice reduced the susceptibility to compatible isolates of M. oryzae, indicating that sHMAs are required for efficient infection and act as susceptibility (S-) genes. sHMAs negatively regulate the accumulation of reactive oxygen species (ROS) and we find that AVR-Pik stabilizes sHMAs. These results suggest that M. oryzae evolved AVR-Pik to target rice sHMAs to enhance host susceptibility. This was followed by independent recombination of HMAs into NLR proteins Pik-1 and RGA5 to function as integrated domains to trap effectors and initiate immune signaling.

Abstract Number: P17-543
Session Type: Poster