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Poster

Session: Session 1 Presenting Authors at Posters (Odds)

P-411 - Extracellular Vesicles: Mediators of Cross-Kingdom Communication in Arbuscular Mycorrhizal Symbiosis

Monday, July 14, 2025
13:30 - 15:15  
Location: Confex Hall 3
Symbiosis and Mutualism (mycorrhiza and N-fixing Rhizobia)

Arbuscular mycorrhizas are among the most important fungi in terrestrial ecosystems. Plants benefit nutritionally from AM fungi by obtaining phosphate in exchange for carbon. As fatty acid auxotrophs AM fungi rely entirely on the plant for lipids. This mutualistic exchange occurs in highly branched, intracellular fungal arbuscules in root cortical cells. However, arbuscules have a short life span of only 2-3 days which suggests an intimately regulated molecular dialogue is needed to maintain the symbiosis. Recently, it was proposed that molecular signals such as small RNAs (sRNAs) function in cross-kingdom RNA interference (ckRNAi) to modulate plant-fungal interactions, however, their role in AM symbiosis remains largely unknown.

Here we present evidence for a highly regulated plant-to-fungal small RNA (sRNA) exchange mediated by extracellular vesicles (EVs) in Medicago truncatula. We have isolated EVs from Rhizophagus irregularis colonised Medicago roots and identified both protein and sRNA cargo. Interestingly, host sRNAs are upregulated during the symbiosis at a time that coincide with EV production to modulate target genes linked to symbiotic function. Expression analysis of sRNAs and fungal target genes revealed downregulation of target genes in the presence of the corresponding sRNAs. Our results provide a first evidence for plant-to-fungal ckRNAi and show a highly regulated role for EV-associated sRNAs in modulating the AM symbiosis.