The Magnaporthe oryzae MAX effector AVR-Pia binds a novel group of rice HMA domain-containing proteins

Maidment, J. H.; Saile, S. C.; Bocquet, A.; Thivolle, C.; Bourcet, L.; Planel, L.-F.; Gelin, M.; Kroj, T.; Padilla, A.; De Guillen, K.; Cesari, S.

doi:10.1101/2025.07.11.664054

bioRxiv · 10.1101/2025.07.11.664054

The Magnaporthe oryzae MAX effector AVR-Pia binds a novel group of rice HMA domain-containing proteins

Maidment, J. H.·Saile, S. C.·Bocquet, A.·Thivolle, C.·Bourcet, L.·Planel, L.-F.·Gelin, M.·Kroj, T.·Padilla, A.·De Guillen, K.·Cesari, S.

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Abstract

Phytopathogenic fungi secrete effector proteins to promote virulence. MAX (Magnaporthe Avrs and ToxB-like) effectors form a sequence-diverse family sharing a conserved protein structure. AVR-Pia, a MAX effector from the rice blast fungus Magnaporthe oryzae, is recognised by the paired rice nucleotide-binding leucine-rich repeat immune receptors OsRGA4/OsRGA5 through direct binding to an integrated heavy metal-associated (HMA) domain in OsRGA5. Here, we identify previously unknown host targets of AVR-Pia: four HMA domain-containing rice proteins, belonging to the HMA Isoprenylated Plant Proteins (HIPPs) and HMA Plant Proteins (HPPs). AVR-Pia interacted with all four proteins, both in vitro and in planta, and bound their HMA domains with varying affinities. The crystal structure of AVR-Pia in complex with the HMA domain of OsHPP09 revealed the molecular details of the binding interface. Structure-guided mutagenesis of OsHPP09 identified a single point mutation which prevents AVR-Pia binding, providing a foundation for targeted engineering of HMA domains to evade effector binding.

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Maidment, J. H., Saile, S. C., Bocquet, A., Thivolle, C., Bourcet, L., Planel, L.-F., Gelin, M., Kroj, T., Padilla, A., De Guillen, K., Cesari, S.. 2025-07-14. The Magnaporthe oryzae MAX effector AVR-Pia binds a novel group of rice HMA domain-containing proteins. https://doi.org/10.1101/2025.07.11.664054

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