Tandem Cytochrome P450 Monooxygenase Genes and Splice Variants in the White Rot Fungus Phanerochaete Chrysosporium: Cloning, Sequence Analysis, and Regulation of Differential Expression

Phanerochaete chrysosporium, the model white rot fungus, uses P450 monooxygenation for oxidation of xenobiotic chemicals. To characterize its P450 systems, we have isolated two tandemly linked full-length P450 monooxygenase genes, pc-1 (2510bp) and pc-2 (2503bp). cDNA sequence and splice site analysis showed multiple small putative introns (35-82bp), 17 in pc-1 and 16 in pc-2. The deduced P450 proteins PC-1 (531 aa, MW 60,070) and PC-2 (538 aa, MW 61,765) showed 55% aa identity with each other and low relatedness (25-36%) with P450 gene families CYP52, CYP86, CYP4, and CYP3 decreasing in that order. Alternate splicing was identified for pc-1 transcription. Real-time quantitative RT-PCR analysis on 4-day cultures showed an elevated level of expression ( approximately 8-fold) of pc-1 in nutrient-limited (ligninolytic) as compared to nutrient-rich (non-ligninolytic) conditions. Interestingly, the pc-1 gene is expressible in both primary and secondary phases of growth with peak expression occurring with secondary metabolism.