Plett, J. M., et al. 2020. New Phytologist

Mycorrhizal effector PaMiSSP10b alters polyamine biosynthesis in Eucalyptus root cells and promotes root colonization

Jonathan M. Plett, Kirsta L. Plett, Johanna Wong-Bajracharya, Maira de Freitas-Pereira, Mauricio Dutra Costa, Annegret Kohler, Francis Martin, and Ian C. Anderson

20 June 2020, New Phytologist 228(2): 712 – 727;  https://doi.org/10.1111/nph.16759

Summary

• Pathogenic microbes are known to manipulate the defences of their hosts through the production of secreted effector proteins. More recently, mutualistic mycorrhizal fungi have also been described as using these secreted effectors to promote host colonization. Here we characterise a mycorrhiza‐induced small secreted effector protein of 10 kDa produced by the ectomycorrhizal fungus Pisolithus albus, PaMiSSP10b.
• We demonstrate that PaMiSSP10b is secreted from fungal hyphae, enters the cells of its host, Eucalyptus grandis, and interacts with an S‐adenosyl methionine decarboxylase (AdoMetDC) in the polyamine pathway. Plant polyamines are regulatory molecules integral to the plant immune system during microbial challenge.
• Using biochemical and transgenic approaches we show that expression of PaMiSSP10b influences levels of polyamines in the plant roots as it enhances the enzymatic activity of AdoMetDC and increases the biosynthesis of higher polyamines. This ultimately favours the colonization success of P. albus.
• These results identify a new mechanism by which mutualistic microbes are able to manipulate the host’s enzymatic pathways to favour colonization.

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