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Fungal symbiont Mycena complements impaired nitrogen utilization in Gastrodia elata and supplies indole-3-acetic acid to facilitate its seed germination

Summary

A special type of orchid called Gastrodia elata cannot survive on its own because it has lost the ability to produce its own food and certain plant growth hormones. Instead, it relies completely on a fungal partner called Mycena to provide nitrogen nutrients and auxin (a growth hormone). This study reveals exactly how Mycena does this by analyzing their genes and how they communicate, showing that the fungus acts as a nutritional life-support system for the orchid seed’s germination.

Background

Gastrodia elata is a fully mycoheterotrophic orchid that depends entirely on symbiotic association with Mycena fungi for early growth and seed germination. The plant lacks essential genes for nitrogen utilization and indole-3-acetic acid (IAA) biosynthesis, making it nutritionally dependent on its fungal partner.

Objective

To elucidate how the fungal symbiont Mycena compensates for impaired nitrogen utilization and supplies auxin to facilitate seed germination in G. elata through genome-scale analysis and functional validation.

Results

G. elata lacks genes for nitrogen assimilation and IAA biosynthesis while Mycena retains a complete set. Mycena upregulates nitrogen metabolism and tryptophan-dependent IAA biosynthesis genes during symbiosis. Disruption of MyNir (nitrite reductase) and MyAmid (amidase) significantly impaired seed germination, reduced IAA production, blocked auxin signaling, and altered energy metabolism in G. elata.

Conclusion

Mycena compensates for G. elata’s incomplete nitrogen metabolism by assimilating inorganic nitrogen and producing IAA, which promotes seed germination through coordinated hormonal crosstalk, energy mobilization, and cellular restructuring. These findings provide novel insights into plant-fungal symbiotic associations from a nitrogen utilization perspective.
  • Published in:Plant Communications,
  • Study Type:Research Study,
  • Source: PMID: 40903900, DOI: 10.1016/j.xplc.2025.101500
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