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Plenary Session

Session: Plenary Session 6

MAX effectors in the rice-Magnaporthe oryzae interaction

Wednesday, July 16, 2025
17:55 - 18:20  
Location: Confex Hall 1+2

Phytopathogenic fungi secrete effector proteins during host colonization to facilitate infection. Our group has identified a large effector family, termed MAX (Magnaporthe AVRs and ToxB-like), characterized by a conserved 3-dimensional fold despite highly divergent amino-acid sequences and surface properties. This structural conservation coupled with sequence diversification suggests a capacity to interact with a broad spectrum of host targets. In Magnaporthe oryzae, the causal agent of rice blast disease, MAX effectors are particularly abundant. Across 120 isolates representing seven host-associated lineages, we identified ~60 MAX genes per genome. Over half of these genes are specifically expressed during the biotrophic phase of rice infection, suggesting a role in virulence. To investigate MAX effector function, we conducted large-scale protein-protein interaction screens in both heterologous and homologous systems, leading to the identification of putative targets in rice. Several MAX effectors were found to interact with heavy metal-associated (HMA) domain-containing proteins, specifically members of the HIPP (HMA isoprenylated plant protein) and HPP (HMA plant protein) subfamilies, both of which include susceptibility factors in diverse plant-pathogen systems. Other MAX effectors interacted with a wide array of unrelated rice proteins, suggesting functional diversification within the family. This presentation will provide an overview of our current progress in elucidating the function, localization, and structure of MAX effectors and their putative targets. These findings improve our understanding of the function of fungal effectors and may contribute to the development of blast-resistant plants.