Involvement of protein kinase C in lignin peroxidase expression in oxygenated cultures of the white rot fungus Phanerochaete chrysosporium

Hydroxyl radicals (OH) were previously hypothesized as the principal ROS triggering lip-H2 expression in liquid cultures of Phanerochaete chrysosporium, through signal transduction. We therefore focused on determining the relationship between protein kinase C (PKC), ROS and LIP-H2. Significantly lower PKC activity was measured in high-LIP-producing (oxygenated) vs. low-LIP-producing (aerated-grown with free exchange of atmospheric air) cultures. In oxygenated cultures, inactivation of PKC activity by calphostin C, staurosporin or H7 caused significant elevation in lip-H2 and also in MnSOD1 expression. Stimulation of PKC by phorbol 12-myristate 13-acetate (PMA) caused the reverse effect. Significantly low levels of lip-H2 expression were detected when O₂^-, H₂O₂ or OH were scavenged by 4,5-dihydroxy-1,3-benzene disulfonic acid (Tiron), pyruvate or dimethylsulfoxide (DMSO), whether the level of PKC was normal, stimulated or inactivated. In situ generation of OH, via addition of Fenton reagents to aerated cultures, reduced pkc expression. In contrast, OH scavenging stimulated pkc expression. This work suggests that due to high OH levels, fungal cells activate a complex defensive system which regulates the levels of Fenton components by repressing PKC and stimulating LIP, MnSOD1 and catalase.