Factors Affecting the Induction of Lignin Peroxidase in Manganese-Deficient Cultures of the White Rot Fungus <i>Phanerochaete chrysosporium</i>

Abstract

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 Mn 2 + -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.