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Omics approaches to investigate pre-symbiotic responses of the mycorrhizal fungus Tulasnella sp. SV6 to the orchid host Serapias vomeracea

Summary

This study examines how a fungus called Tulasnella responds to orchids before they physically touch each other. Researchers grew the fungus near young orchid plants separated by a thin membrane and found that the fungus changed its genes and chemistry significantly, suggesting it somehow detected the orchid’s presence. The fungus increased production of proteins and fats, as if preparing for a partnership with the plant. These findings help us understand how plants and fungi communicate and begin their beneficial relationships.

Background

Orchid mycorrhiza (ORM) is a complex symbiosis between orchids and fungi, but the molecular changes during pre-symbiotic stages remain largely unexplored. While arbuscular mycorrhiza has been well-studied regarding pre-symbiotic communication, similar investigations in ORM are limited. Understanding these early interactions could reveal how fungal partners recognize and respond to orchid hosts.

Objective

To investigate the pre-symbiotic responses of the ORM fungus Tulasnella sp. SV6 to the orchid host Serapias vomeracea using transcriptomic and metabolomic approaches. The study focused on fungal gene expression and metabolite changes occurring before physical contact between the fungal mycelium and orchid roots.

Results

Transcriptomic analysis revealed 1,669 differentially expressed genes, with 1,002 up-regulated and 667 down-regulated in the pre-symbiotic stage. Up-regulated genes were associated with protein synthesis, amino acid biosynthesis, and lipid metabolism. Metabolomic analysis showed increased levels of amino acids, phospholipids, and a small secreted protein, suggesting significant metabolic remodeling in response to the host plant presence.

Conclusion

Tulasnella sp. SV6 exhibits distinct transcriptomic and metabolomic remodeling in the pre-symbiotic stage, indicating it perceives information from orchid roots and adjusts its metabolism accordingly. The increased biosynthetic activity and upregulation of a small secreted protein suggest the fungus is preparing for symbiotic interaction, though whether this response is triggered by specific plant signals or other factors requires further investigation.
  • Published in:Mycorrhiza,
  • Study Type:Experimental Research,
  • Source: PMID: 40172721, DOI: 10.1007/s00572-025-01188-6
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