| A huge amount of carbon is sequestered in woody substrates and terrestrial ecosystems depend largely on the degradation capacities of fungi with their unique ability to recycle lignocellulose efficiently. The major modes of lignocellulose degradation by fungi are termed white rot and brown rot. A comparative phylogenetic analysis of enzymes belonging to 14 gene families putatively involved in lignocellulose degradation from the brown rotter Postia placenta and the white rotter Phanerochaete chrysosporium reveals striking differences in the genomes of the two species representing white rot and brown rot chemistries. The genome of the brown rotter Postia is characterized by repeated gene copy losses and a reduced rate of gene duplications throughout most of the 14 gene families as compared to Phanerochaete. In contrast to brown rot fungi, white rot fungi have the ability to degrade lignin, which confers a high degree of recalcitrance to cell walls. White rot fungi achieve this unique capability by secreting extracellular enzymes, of which class II heme peroxidases belonging to the superfamily of plant peroxidases are presumed to play a major role. A detailed phylogenetic analysis of the fungal class II peroxidases supports the monophyly of class II sequences within the plant peroxidase superfamily and demonstrates a trend towards diversification and expansion of the ligninolytic enzymes manganese peroxidases (MnP), lignin peroxidases (LiP), and versatile peroxidases (VP) in wood degrading basidiomycetes. The analyses support independent origins of MnPs and VPs, whereas LiPs arose only once in the basidiomycete class of the Polyporales. The first described MnP-like partial sequences are reported for members of the basidiomycete classes Corticiales (Cytidia salicina) and Hymenochaetales ( Fomitiporia mediterranea). A further investigation of the occurrence of MnP sequences in the grape vine pathogen F. mediterranea enabled the characterization of three full-length mnp gene sequences and the deduced amino to the Hymenochaetales. In addition, phylogenetic analyses including partial class II sequences from other hymenochaetalean taxa support the observation that MnPs of the Hymenochaetales constitute a distinct group within the class II gene family. The three Fomitiporia mnp genes seem to be differentially expressed according to results from real-time PCR experiments. As expected for manganese-dependent peroxidases, the abundancies of the mRNA transcripts increased with increasing manganese concentrations, whereas the third copy exhibited a manganese independent pattern. |
