Huelsmann, C. | Search bioRxiv

bioRxiv2025

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

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

plant biology↗

bioRxiv2024

Barley powdery mildew invasion coincides with the dynamic accumulation of leaf apoplastic extracellular vesicles that are associated with host stress response proteins

The mutual exchange of extracellular vesicles across kingdom borders is a feature of many plant-microbe interactions. The occurrence and cargos of extracellular vesicles has been studied in several instances, but their dynamics in the course of infection have remained elusive. Here we used two different procedures, differential high-speed centrifugation and polymer-based enrichment, to collect extracellular vesicles from the apoplastic wash fluid of barley (Hordeum vulgare) leaves challenged by its fungal powdery mildew pathogen, Blumeria hordei. Both methods yielded extracellular vesicles of similar quality and morphological characteristics, though the polymer approach was associated with higher reproducibility. We noted that extracellular vesicles derived from the apoplastic wash fluid constitute polydisperse populations that are selectively responsive to leaf infection by B. hordei. Extracellular vesicles of [~]100 nm - 300 nm diameter became progressively more abundant, in particular from 72 hours post inoculation onwards, resulting in a major peak late during fungal infection. Vesicles of [~]300 nm - 500 nm showed similar accumulation dynamics but reached much lower levels, suggesting they might constitute a separate population. Proteome analysis uncovered an enrichment of biotic stress response proteins associated with the extracellular vesicles. The barley t-SNARE protein Ror2, the ortholog of the PEN1 marker protein of extracellular vesicles in Arabidopsis thaliana, accumulates in extracellular vesicles during powdery mildew infection, hence also qualifying as a potential marker protein. Our study serves as a starting point for investigating the role of extracellular vesicles at different stages of plant-microbe interactions.

plant biology↗