Physiology and molecular biology of extracellular peroxidases, H2O2-generating system and deregulated mutants of Phanerochaete chrysosporium. Progress report

摘要

We have expanded the work on the LIP genes to Trametes versicolor, the second most studied white-rot fungus after P. chrysosporium. Six LIP genes have been cloned from this organism and one of these has been completely sequenced and compared to the known LIP genes that have been described to date. Our studies gave us further insights into the novel non-integrative transformation system of P. chrysosporium. Our recombinant plasmid pUGLGl-kan, which contains a LIP gene disrupted by the insertion of kan(sup r) determinant, also failed to integrate into the chromosome. Instead, it was maintained as a circular extrachromosomal element and was recoverable as a plasmid both from the meiotic and mitotic progeny. Basic characterization of the lignin peroxidase-negative mutant (lip mutant) and nitrogen-deregulated mutant has been completed. We also investigated the question whether carbon, nitrogen, and Mn(II) regulate LIP expression coordinately or independently. Results indicate that these three environmental controls independently regulate LIP and MNP gene expression. Furthermore, an idiophasic protease has been shown to be responsible for the sharp decline in LIP activity after day 6 of incubation in low nitrogen cultures and addition of glucose to these day 6 cultures has been shown to suppress the protease levels and maintain high levels of LIP. The results further indicated that this protease is synthesized de novo during the idiophase. Additional studies showed that MNPs play a dominant role in the decolorization of chlorolignols in bleached kraft pulp effluents and that LIPs play a relatively minor role in this process. These studies have since been confirmed independently by an Austrian group.