Incomplete processing of peroxidase transcripts in the lignin degrading fungus Phanerochaete chrysosporium

Abstract

Phanerochaete chrysosporium has been thoroughly studied as a microbial model for lignin degradation. The enzymes lignin peroxidase (LiP) and manganese peroxidase (MnP), both encoded by several genes, play the main role in the cleavage of different lignin substructures. In this work, the expression of specific LiP and MnP transcripts in liquid medium and in a wood-containing soil system was studied by reverse transcription-PCR and subsequent cloning and sequencing of the products obtained. Splice variants of different LiP and MnP transcripts were observed in wood-containing soil incubations and in liquid cultures. The processed transcripts contained different numbers of complete introns. Since the presence of stop codons in several of these introns would prevent the synthesis of active enzyme, we propose that these transcripts arise as a result of incomplete processing rather than alternative splicing. Interestingly, analysis of splice variants from mnp genes led to the identification of a fourth actively transcribed gene coding for MnP in P. chrysosporium.