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Hallmarks of Basidiomycete Soft- and White-Rot in Wood-Decay -Omics Data of Two Armillaria Species

Summary

This research investigated how two species of fungi break down wood in forest ecosystems. The study revealed that these fungi use an unusual strategy to decay wood that differs from what scientists previously thought. Instead of breaking down all components of wood equally, they focus on degrading specific parts while leaving others largely untouched. This has important implications for understanding forest health and carbon cycling. Impacts on everyday life: • Helps explain how forests naturally recycle dead wood and return nutrients to soil • Provides insights for developing more efficient wood-degrading processes for biofuel production • Improves understanding of forest diseases and their management • Contributes to knowledge about natural carbon cycling in forests • Could lead to new applications in sustainable waste management

Background

Wood-decaying Basidiomycetes are key players in forest ecosystems and global carbon cycling due to their ability to efficiently degrade plant cell walls. Recent studies have revealed high functional diversity in wood-decay strategies, particularly within the traditional white-rot and brown-rot classifications. Armillaria species include both devastating forest pathogens and saprotrophs that decay wood, but their wood-decay mechanisms deviate from typical white-rotters.

Objective

To examine the mechanistic bases of wood-decay in the conifer-specialists Armillaria ostoyae (pathogenic) and Armillaria cepistipes (saprotrophic) using transcriptomic and proteomic approaches, and to better understand their wood-decay strategies compared to typical white-rot fungi.

Results

The saprotrophic A. cepistipes showed a stronger transcriptional and protein-level response to wood than the pathogenic A. ostoyae. Both species showed upregulation of diverse plant cell wall degrading enzymes, particularly pectinases and expansins, while lignin-degrading enzymes were generally downregulated. The study found enrichment of pectinolytic genes, iron acquisition systems, and CBM67 proteins, with limited expression of lignin-degrading enzymes.

Conclusion

Armillaria species display an atypical wood-decay strategy that resembles soft-rot decay rather than typical white-rot, characterized by preferential degradation of cellulose and pectin while largely bypassing lignin degradation. This suggests the existence of an ancestral soft-rot decay machinery conserved across Ascomycota and Basidiomycota, with subsequent evolution of efficient lignin-degrading abilities in white-rot fungi.
  • Published in:Microorganisms,
  • Study Type:Comparative Transcriptomic and Proteomic Analysis,
  • Source: 10.3390/microorganisms9010149
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