Reverse transcription-PCR analysis of the regulation of the manganese peroxidase gene family.

Manganese peroxidase (MnP) gene expression in the lignin-degrading fungus Phanerochaete chrysosporium is regulated by nutrient nitrogen levels and by Mn(II), the substrate for the enzyme, as well as by heat shock and other factors. Reverse transcription-PCR (RT-PCR) of total RNA can distinguish the mRNAs of each of the three sequenced P. chrysosporium mnp genes, i.e., mnp1, mnp2, and mnp3. Quantitative RT-PCR demonstrates that each of the three transcripts is present at a similar low basal level in nitrogen-sufficient cultures, with or without Mn, and in nitrogen-limited cultures lacking Mn. However, in 5-day-old, nitrogen-limited, stationary cultures supplemented with 180 microM Mn, the levels of the mnp1 and mnp2 transcripts increased approximately 100- and 1,700-fold, respectively, over basal levels. In contrast, under these conditions, the level of the mnp3 transcript did not increase significantly over the basal level. Quantitative RT-PCR of total RNA extracted from nitrogen-deficient, Mn-supplemented cultures on days 2 through 7 demonstrates that whereas the mnp1 transcript was present at relatively low levels on days 3 through 7, the mnp2 transcript level peaked on day 5 and the mnp3 transcript level peaked on day 3. Comparison of total RNA extracted on day 5 from nitrogen-deficient, Mn-supplemented stationary and agitated cultures indicates that in stationary cultures, mnp2 was the major expressed mnp gene, whereas in large agitated cultures, mnp1 was the major expressed mnp gene.