Pleurotus ostreatus manganese-dependent peroxidase silencing impairs decolourization of Orange II.
Bottom Line: Relative real-time PCR quantification analysis confirmed that all the nine genes are transcribed, and that Mn(2+) amendment results in a drastic increase in the transcript levels of the predominantly expressed MnP genes (mnp 3 and mnp 9), while decreasing versatile peroxidase gene transcription (mnp 4).Knock-down of mnp 3 resulted in the reduction of fungal OII decolourization capacity, which was co-linear with marked silencing of the Mn(2+)-dependent peroxidase genes mnp 3 and mnp 9.This is the first direct genetic proof of an association between MnP gene expression levels and azo dye decolourization capacity in P. ostreatus, which may have significant implication on understanding the mechanisms governing lignin biodegradation.
Affiliation: Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.Show MeSH
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Mentions: The capacity of the white‐rot fungus P. ostreatus strain PC9 to decolourize OII was evaluated both on solid media and in liquid culture, in the presence of Mn2+ at several concentrations ranging 0–270 µM. Mn2+ concentration in the non‐amended medium was determined by atomic absorption spectroscopy and was found to be less than 0.1 µM. On solid medium, linear growth rate was not affected by the Mn2+ amendments, yet decolourization was apparent only at concentrations above 8.1 µM, and its intensity was increased with elevation of Mn2+ concentration in the medium (Fig. 1A). In the absence of Mn2+ no visible changes in OII colour intensity were observed even after 30 days of incubation. Media containing Mn2+ concentrations higher than 54 µM showed formation of dark precipitation foci of MnO2 (López et al., 2007). Consequently, for further analysis on solid media we used Mn2+ at a concentration of 27 µM. Decolourization was also monitored in liquid culture for 10 days (Fig. 1B), showing a similar dependency on Mn2+ concentration. The fungal dry weight in liquid culture was similar in all treatments (average of 256 mg/flask after 10 days of incubation, with a ±4% deviation). OII decolourization did not occur in non‐inoculated media, at any of the examined Mn2+ concentrations, even after 30 days of incubation. Since this reaction depends on the presence of Mn2+ and there was no decolourization in the absence of Mn2+, it was attributed to Mn2+‐dependent peroxidase activity. Accordingly, OII decolourization can serve as a differential phenotypic assay for the expression level of these enzymes and was used here to assess mnp3 silenced strains.
Affiliation: Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.