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Lignin-degrading Enzymes from a Pathogenic Canker-rot Fungus Inonotus obliquus Strain IO-B2

Summary

This research investigated how the medicinal mushroom Chaga breaks down wood components using special enzymes. Scientists mapped the fungus’s genetic code and studied specific enzymes that help it decompose lignin, a tough component of wood. The findings help explain how this fungus survives on trees and potentially produces beneficial compounds. Impacts on everyday life: • Better understanding of how medicinal mushrooms like Chaga produce beneficial compounds • Potential applications in developing natural treatments for cancer and inflammation • Insights for developing eco-friendly methods for breaking down wood waste • Improved knowledge for sustainable cultivation of medicinal mushrooms • Applications in biotechnology for producing useful enzymes

Background

Inonotus obliquus is a pathogenic fungus found in living trees that has been widely used as traditional medicine for cancer therapy. The fungus parasitizes living trees by forming sclerotia or canker-like bodies called ‘Chaga’. While lignocellulose-degrading enzymes are involved in early stages of host infection, the parasitic life cycle and enzymatic mechanisms of this fungus are not fully understood.

Objective

To investigate the activities of laccase (Lac), manganese peroxidase (MnP), and lignin peroxidase (LiP) from I. obliquus cultivated in Kirk’s medium. Additionally, to sequence the fungal genome and identify genes related to wood degradation, with particular focus on characterizing the molecular structure of a putative MnP enzyme.

Results

The genome sequence comprised 21,203 predicted protein-coding genes, with 134 genes related to wood degradation. Of these, 47 genes were associated with lignin degradation, with mnp genes being most numerous. The characterized IoMnP1 showed catalytic properties analogous to MnP and was phylogenetically related to MnPs from Pyrrhoderma noxium, Fomitiporia mediterranea, and Sanghuangporus baumii. Enzyme assays detected Lac and MnP activities but no LiP activity in the fungal extract.

Conclusion

IoMnP1 was confirmed to be a member of the manganese peroxidase family based on its molecular structure and phylogenetic relationships. The genome analysis revealed numerous genes involved in wood degradation, particularly those related to lignin breakdown, supporting I. obliquus’s role as a white-rot fungus. The absence of LiP genes and activity suggests the fungus relies primarily on MnP and Lac for lignin degradation.
  • Published in:AMB Express,
  • Study Type:Laboratory Research,
  • Source: 10.1186/s13568-023-01566-3
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