REGULATION OF MANGANESE PEROXIDASE GENE-TRANSCRIPTION BY HYDROGEN-PEROXIDE, CHEMICAL STRESS, AND MOLECULAR-OXYGEN

The expression of manganese peroxidase (MnP) in nitrogen-limited cultu res of the lignin-degrading fungus Phanerochaete chrysosporium is regu lated at the level of gene transcription by H2O2 and various chemicals , including ethanol, sodium arsenite, and 2,4-dichlorophenol, as well as by Mn(II) and heat shock Northern (RNA) blot analysis demonstrates that the addition of 1.0 mM H2O2 to 5-day old cultures grown in the ab sence of Mn results in the appearance of mnp mRNA within 15 min. Highe r levels of mnp mRNA are obtained with simultaneous induction by Mn an d H2O2 than with H2O2 alone. Although neither MnP activity nor associa ted protein is detectable in H2O2-induced cultures groan in the absenc e of Mn, simultaneous induction with Mn and H2O2 results in a 1.6-fold increase in MnP activity compared with the MnP activity resulting fro m Mn induction alone. In the presence of Mn, purging of low-nitrogen c ultures with 100% O-2, in contrast to incubation under air, results in an increase in the accumulation of mnp mRNA and a 13-fold increase in MnP activity on day 5. However, in contrast to the effects of H2O2 an d heat shock, O-2 purging of Mn-deficient cultures results in negligib le accumulation of mnp mRNA.