The lignin peroxidase (LIP) production and regulation, in manganese ions (Mn 2+ ) deficient cultures of the white rot fungus Phanerochaete chrysosporium, is still not clearly understood. Mn 2+ deficiency is correlated to low levels of manganese containing superoxide dismutase (MnSOD). In this work, we show that despite the low activity level of MnSOD in Mn 2+ -deficient cultures, the presence of H 2 O 2 is essential for the expression of the lip-H2 gene, which encodes for the major LIP isoenzyme produced (LIP-H2). Thus, the H 2 O 2 present in Mn 2+ -deficient cultures is probably produced by other mechanisms rather than dismutation of superoxide ions by MnSOD. Glyoxal oxidase gene (glox) expression was significantly higher than MnSOD (MnSOD1) and cellobiose dehydrogenase (cdh1) expression in Mn 2+ -deficient cultures, indicating its clear involvement in H 2 O 2 production in those cultures. Glyoxal oxidase may compensate the absence of MnSOD activity in Mn 2+ -deficient cultures. The high levels of reactive oxygen species (ROS) needed for the enhancement of LIP expression in Mn2+ -deficient cultures were not directly correlated to the protein kinase C (PKC) activity involved in signal transduction pathway. High level of oxidative stress was observed in MnSOD silenced mutants, grown in the presence of Mn 2+ , indicating that oxidative stress in Mn 2+ -deficient cultures was caused by low levels of MnSOD rather than the deficiency in Mn 2+ . The results of this work can further contribute to the understanding of LIP regulation in Mn 2+ -deficient cultures.