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bioRxiv · 10.1101/2025.06.04.657782

Cooperation between a root fungal endophyte and host-derived coumarin scopoletin mediates Arabidopsis iron nutrition

Van Dijck, L.·Esposto, D.·Huelsmann, C.·Malisic, M.·Piro, A.·Giehl, R. F. H.·Balcke, G. U.·Tissier, A.·Parker, J. E.
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Abstract

O_LIIron acquisition is a critical challenge for plants, especially in iron-deficient soils. Recent research underscores the importance of root-exuded coumarins in modulating the root microbiome community structure and facilitating iron uptake. However, interactions between root-associated fungi and coumarins in plant iron nutrition remain unknown. We investigated the mechanism by which a fungal endophyte, Macrophomina phaseolina (F80), enhances Arabidopsis iron nutrition. C_LIO_LIFungal-coumarin interactions were assessed by profiling metabolites and measuring iron mobilisation in F80 cultures supplemented with specific coumarins, alongside quantifying growth performance and iron content in Arabidopsis coumarin-biosynthesis mutants inoculated with F80. C_LIO_LIOur findings reveal that an interaction between the coumarin scopoletin and F80 in the rhizosphere rescues plant growth under iron-limiting conditions by resolving the iron mobility bottleneck. F80 exhibits a capacity to modify scopoletin into iron-chelating catechol coumarin esculetin, thereby releasing available iron. C_LIO_LIWe conclude that Arabidopsis-produced scopoletin functions as a precursor for fungal conversion into iron-chelating coumarins. By extending the role of coumarins from bacterial to fungal members of the root microbiota, this study places coumarins at the centre of commensal-mediated enhancement of plant iron nutrition across microbial kingdoms. C_LI

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Van Dijck, L., Esposto, D., Huelsmann, C., Malisic, M., Piro, A., Giehl, R. F. H., Balcke, G. U., Tissier, A., Parker, J. E.. 2025-06-06. Cooperation between a root fungal endophyte and host-derived coumarin scopoletin mediates Arabidopsis iron nutrition. https://doi.org/10.1101/2025.06.04.657782

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