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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 research explores how orchid-associated fungi sense and respond to their host plants before they even make physical contact. Scientists used advanced molecular techniques to track changes in gene expression and chemical composition in Tulasnella fungal cells when exposed to orchid plants. The fungi showed significant metabolic preparation, increasing production of proteins and cellular membrane components, suggesting they are actively preparing for symbiosis. This study reveals that plant-fungus interactions begin through long-distance chemical communication before the organisms ever physically meet.

Background

Orchid mycorrhiza (ORM) is a complex plant-fungal symbiosis where orchid seeds require fungal colonization for germination and early development. While metabolism has been studied in established mycorrhizal tissues, molecular changes during pre-symbiotic stages in ORM remain largely unexplored. This study investigates how the ORM fungus Tulasnella sp. SV6 responds to the presence of its host plant before physical contact occurs.

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 fungal mycelium was harvested before physical contact with orchid roots to identify molecular changes occurring during early interaction stages.

Results

The ORM fungus showed significant transcriptomic remodeling with 1,002 up-regulated and 667 down-regulated genes in the PRESYMB condition. Up-regulated genes were associated with protein synthesis, amino acid biosynthesis, and lipid metabolism. Metabolomic analysis revealed increased levels of amino acids (proline, phenylalanine) and phospholipids (phosphatidylcholines, lysophosphatidylcholines), supporting the transcriptomic data. A small secreted protein was strongly up-regulated, potentially involved in early symbiotic signaling.

Conclusion

Tulasnella sp. SV6 perceives information from orchid roots and undergoes significant transcriptomic and metabolomic remodeling before physical contact, suggesting active pre-symbiotic communication. The fungus activates biosynthetic pathways for protein and lipid synthesis, indicating metabolic preparation for symbiotic interaction. These results provide insight into the early molecular events in orchid mycorrhiza establishment.
  • Published in:Mycorrhiza,
  • Study Type:Experimental Research,
  • Source: PMID: 40172721, DOI: 10.1007/s00572-025-01188-6
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