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Impact of sublethal zinc exposure on ectomycorrhizal Laccaria bicolor x poplar symbiosis

Summary

This research examines how a fungus called Laccaria bicolor helps poplar trees survive in soil contaminated with excess zinc. The study found that even under zinc stress, the fungus and tree can maintain their symbiotic partnership, though both grow slower and the fungal layer around roots thins. The fungus activates special defense mechanisms and transporter proteins to manage zinc levels and protect the tree host, demonstrating remarkable resilience of this natural partnership.

Background

Zinc pollution is a widespread environmental problem affecting plant growth and production. Ectomycorrhizal fungi can help tree species mitigate toxicity effects. The resilience of plant-fungal symbiotic interactions under metal stress conditions remains poorly understood.

Objective

To investigate the impact of sublethal zinc exposure on Laccaria bicolor and its ectomycorrhizal symbiosis with Populus tremula x alba. The study examined growth, morphological parameters, symbiosis marker genes, reactive oxygen species scavenging enzymes, and zinc transporters in the presence and absence of a host plant.

Results

Ectomycorrhizal symbiosis development was maintained under excess zinc despite reduced fungal and plant growth. Symbiosis marker genes showed zinc-induced transcriptional responses even without a host plant. ROS scavenging enzyme expression and zinc transporter regulation were primarily responsive in the presence of a host, suggesting host-fungus interplay is essential for adaptation to zinc stress.

Conclusion

L. bicolor and P. tremula x alba maintain ectomycorrhizal symbiosis under zinc stress through establishment of new homeostatic equilibria. The fungal mantle structure is significantly impacted while the Hartig net remains relatively unaffected. Specific zinc transporters showing host-dependent regulation were identified as candidates for host protection functions and warrant further functional characterization.
  • Published in:Frontiers in Plant Science,
  • Study Type:Experimental study,
  • Source: PMID: 40959553, DOI: 10.3389/fpls.2025.1656580
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