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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

Gastrodia elata is a special orchid that cannot make its own food and must rely entirely on a fungal partner called Mycena. Scientists discovered that the orchid has lost genes needed to use nitrogen and make growth hormones, while the fungus Mycena has kept these genes. By providing nitrogen and a hormone called auxin, the fungus helps the orchid seeds germinate and grow.

Background

Gastrodia elata is a fully mycoheterotrophic orchid that depends entirely on its fungal symbiont Mycena for early growth and seed germination. The plant lacks essential genes for nitrogen utilization and auxin biosynthesis, making it nutritionally dependent on fungal partners.

Objective

To elucidate the genetic and physiological mechanisms by which the fungal symbiont Mycena supplies nitrogen nutrients and indole-3-acetic acid (IAA) to facilitate seed germination in G. elata through genome-scale analysis and transcriptomic profiling.

Results

G. elata lacks genes for nitrogen assimilation and IAA biosynthesis while Mycena retains a complete set. MyNir and MyAmid knockout mutants showed significantly impaired nitrogen utilization, reduced IAA production (61-69% reduction in ΔMyAmid), and blocked seed germination. Disruption altered hormone crosstalk, energy metabolism, and cellular restructuring in G. elata seeds.

Conclusion

Mycena compensates for the incomplete nitrogen metabolism of G. elata by assimilating nitrate via MyNir and producing IAA via MyAmid, thereby promoting seed germination through coordinated hormonal signaling, energy mobilization, and cellular restructuring. These findings provide novel insights into plant-fungal symbiotic associations from the nitrogen utilization perspective.
  • Published in:Plant Communications,
  • Study Type:Experimental Research Study,
  • Source: PMID: 40903900
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