20/9: M. Cosme - Interactions between arbuscular mycorrhizal fungi and Arabidopsis

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20/9: M. Cosme - Interactions between arbuscular mycorrhizal fungi and Arabidopsis

20/9: M. Cosme - Interactions between arbuscular mycorrhizal fungi and the non-host plant Arabidopsis

20 septembre 2019

Salle de séminaire FRAIB

Marco Cosme (Université Catholique de Louvain), lauréat du programme Marie Curie, présentera ses travaux sur l’étude de l'incompatibilité non-hôte dans la symbiose mycorhizienne à arbuscule à l'occasion de ce séminaire intitulé "Interactions between arbuscular mycorrhizal fungi and the non-host plant <i>Arabidopsis</i>".

Arbuscular mycorrhizal (AM) fungi are unable to form symbiotic associations with approximately 29% of all vascular plants, including important crops and model organisms, and often antagonize their growth. The underlying mechanism of this antagonism is poorly understood.

We deployed the AM fungus Rhizophagus irregularis against the non-host plant Arabidopsis to analyze transcriptional changes and monitor fungal colonization and plant growth depression in Arabidopsis lines altered in phytohormone or microbe-associated molecular pathways. We analyzed also de novo hyphal germination and fungal metabolism under the influence of roots or exudates.

mcosmemontage

Colonized Arabidopsis root

R. irregularis activated Arabidopsis strigolactone biosynthesis genes, suggesting that early non-host detection of AM fungi is not completely impaired. However, in colonized Arabidopsis roots, fungal nutrient transporters were inactive. Although we observed defense-related GO term enrichment in Arabidopsis, associated with mycorrhizal-induced resistance (MIR), neither the compromised defense nor growth phytohormone pathways affected the AM fungal antagonism against Arabidopsis. Moreover, plant mutants susceptible to various pathogens were not susceptible to R. irregularis. Conversely, a coumarin exudation pathway stimulated colonization in Arabidopsis when R. irregularis was nursed by neighboring host roots. This was associated with activation of fungal metabolism and de novo hyphal germination.

Altogether, R. irregularis did not act like a typical pathogen nor Arabidopsis autoregulated growth-defense tradeoffs. This suggests that, although non-hosts still hold functional conservation of MIR, AM fungal antagonism against non-hosts may entangle a more specialized mechanism yet uncharted. Furthermore, we uncover that coumarin exudation involved with plant responses to nutrient depletion can excite AM fungi during the prepenetration dialogue.

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Mcosme

Marco Cosme est chercheur en post-doctorat au sein de l'Université Catholique de Louvain.

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Date de création : 06 juin 2023