Zymoseptoria tritici proteins structurally related to UmV-KP4 and UmV-KP6 are toxic to fungi, and define novel structural families of fungal effectors

de Guillen, K.; Mammri, L.; Gracy, J.; Padilla, A.; BARTHE, P.; Hoh, F.; Lahfa, M.; Rouffet, J.; Petit-Houdenot, Y.; Kroj, T.; Lebrun, M.-H.

doi:10.1101/2024.10.14.618152

bioRxiv · 10.1101/2024.10.14.618152

Zymoseptoria tritici proteins structurally related to UmV-KP4 and UmV-KP6 are toxic to fungi, and define novel structural families of fungal effectors

de Guillen, K.·Mammri, L.·Gracy, J.·Padilla, A.·BARTHE, P.·Hoh, F.·Lahfa, M.·Rouffet, J.·Petit-Houdenot, Y.·Kroj, T.·Lebrun, M.-H.

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Abstract

Fungal effectors play crucial roles in plant infection. Despite low sequence identity, effectors were recently classified into structural families. In this study, we have elucidated the structures of Zt-NIP1 and Mycgr3-91409 effectors of the wheat fungal pathogen Zymoseptoria tritici, using X-ray crystallography and NMR. These effectors displayed a structural homology with, respectively, KP4 and KP6 killer toxins, from UmV dsRNA viruses infecting the corn fungal pathogen Ustilago maydis. Consequently, Zt-NIP1 and Mycgr3-91409 were renamed Zt-KP4-1 and Zt-KP6-1. Orthologs and paralogs of Zt-KP4-1 and Zt-KP6-1 were identified in Zymoseptoria, but not in other fungi, except Ecp2 effectors related to Zt-KP4-1. Assessment of the biological activities of Zt-KP6-1 and Zt-KP4-1 revealed their toxicity to fungi such as Botrytis cinerea and Z. tritici, but not to wheat. A novel pipeline relying on Foldseek and cysteine-pattern constrained HMM searches of AlphaFold2 predicted structures from Uniprot generated a comprehensive inventory of KP4 and KP6 proteins in fungi and plants. A structure-based classification of these proteins revealed four KP4 and three KP6 structural super families. This classification provided far-reaching hypotheses on their biological function and evolution. This unifying structural framework highlights the power of structure determination for the classification of effectors, and their functional investigation.

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de Guillen, K., Mammri, L., Gracy, J., Padilla, A., BARTHE, P., Hoh, F., Lahfa, M., Rouffet, J., Petit-Houdenot, Y., Kroj, T., Lebrun, M.-H.. 2024-10-16. Zymoseptoria tritici proteins structurally related to UmV-KP4 and UmV-KP6 are toxic to fungi, and define novel structural families of fungal effectors. https://doi.org/10.1101/2024.10.14.618152

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