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Concurrent Session

Session: Concurrent Session: Symbiosis and Mutualism (mycorrhiza and N-fixing Rhizobia)

Stimulation of arbuscular mycorrhizal symbiosis by a fungal tripeptide

Monday, July 14, 2025
11:40 - 11:50  
Location: Confex Hall 1+2

Abstract Text:

Most land plants, including crops, establish a mutualist association with arbuscular mycorrhizal (AM) fungi. During this interaction, plants acquire water and minerals from the fungus, that explores the soil far beyond the plant root system. In return, fungi are rewarded with sugars and lipids from the host plants. These exchanges occur in specialized structures, the arbuscules, that develop in plant cells through dichotomous branching of fungal hyphae. To allow fungal colonization and proper establishment of the symbiosis interface, cell-cell communication play crucial roles. Using a bioinformatics approach in the model species Rhizophagus irregularis, we identified a family of five proteins predicted to deliver multiple copies of a secreted tripeptide. Interestingly, these proteins display canonical features of Ascomycota sexual pheromone precursors, suggesting a role in cell-cell communication during fungal development and/or symbiosis. Indeed, our data collectively show that these fungal peptide genes are induced by plant exudates and are strongly expressed during symbiosis. Moreover, the predicted tripeptides can be detected using targeted mass spectrometry in germinated spores and in mycorrhized roots. Furthermore, exogenous application with the synthetic peptide increases hyphal fusions in vitro and promotes symbiotic interaction with the model plant Medicago truncatula, thus highlighting the existence of a new fungal-derived pheromone regulating AM symbiosis.