Redundancy among manganese peroxidases in Pleurotus ostreatus

Area of Science:

• Mycology and biochemistry
• Enzymology and fungal metabolism

Background:

• Manganese peroxidases (MnPs) are crucial enzymes in lignin degradation by white rot fungi.
• Pleurotus ostreatus possesses a family of nine MnP genes (mnp1-9).
• Mn(2+) supplementation enhances the degradation of recalcitrant compounds like azo dye orange II by P. ostreatus.

Purpose of the Study:

• To investigate the role of specific MnP genes, particularly mnp3, in the ligninolytic capabilities of P. ostreatus.
• To understand the functional significance of MnP3 in Mn(2+)-sufficient conditions.
• To explore potential functional redundancy within the MnP gene family.

Main Methods:

• Gene targeting was used to inactivate the mnp3 gene in P. ostreatus using a Δku80 strain.
• Expression levels of mnp genes were monitored.
• Total MnP activity and orange II decolorization capacity were measured in wild-type and gene-inactivated strains.
• Inactivation of mnp4 and mnp9 was also performed to assess their roles.

Main Results:

• mnp3, mnp4, and mnp9 were highly expressed in Mn(2+)-amended medium, with mnp3 predominant at peak orange II decolorization.
• Inactivation of mnp3 did not significantly impair Mn(2+)-mediated orange II decolorization, despite reduced total MnP activity.
• Inactivation of mnp4 or mnp9 also did not affect orange II decolorization.
• Expression of other mnp genes remained largely unaffected by mnp3 inactivation.

Conclusions:

• The Pleurotus ostreatus MnP gene family exhibits functional redundancy.
• Deficiency in one MnP gene, such as mnp3, can be compensated by other members of the family.
• This redundancy ensures the maintenance of ligninolytic and dye decolorization functions even when specific MnPs are absent or reduced.