Gene Expression Profiling and Enzymatic Function of Phanerochaete Chrysosporium Cytochrome P450s Involved in the Metabolism of Benzo(a)pyrene

Abstract

The completed genome sequences and genomics databases currently available for plants, animals and fungi provide a scaffold for addressing the biological role of the impressive gene collection in these organisms. The white-rot fungus Phanerochaete chrysosporium encodes 149 cytochrome P450 (CYP) genes in its genome. The functions of many of these genes or their target substrates are still unknown. This study aimed at elucidating the functions of P. chrysosporium’s cytochrome P450 (PcCYP) gene repertoire using the polyclic aromatic hydrocarbon (PAH) benzo(a)pyrene (BaP) as a substrate. The set of complementary expression systems used in this study was pivotal in assigning function to the PcCYPs investigated. A cDNA microarray system targeting 133 P. chrysosporium P450 cDNAs as probes was used to investigate the differential expression patterns of PcCYPs gene diversity in response to this PAH. BaP was able to elicit a response of 12 cytochrome P450 genes strongly suggesting that it was a potential substrate of these PcCYPs. A functional analysis of the 12 PcCYP genes targeting the coding sequences of these P. chrysosporium P450 cDNAs as probes was conducted. These PcCYPs 1a, 5b, 24s, 30d, 59a, 59c and 66a were proved to be functional with a heterologous Saccharomyces cerevisiae expression system. These findings strongly suggest that species that gave a physiological response and metabolized the substrate are key to the metabolism of this PAH. This knowledge can be applied to make improved predictions on the cellular systems optimized for aromatic degradation by this fungus applicable in bioremediation.