Structure, Organization, and Transcriptional Regulation of a Family of Copper Radical Oxidase Genes in the Lignin-Degrading Basidiomycete Phanerochaete chrysosporium

Abstract

The white rot basidiomycete Phanerochaete chrysosporium produces an array of nonspecific extracellular enzymes thought to be involved in lignin degradation, including lignin peroxidases, manganese peroxidases, and the H 2 O 2 -generating copper radical oxidase, glyoxal oxidase (GLX). Preliminary analysis of the P. chrysosporium draft genome had identified six sequences with significant similarity to GLX and designated cro1 through cro6. The predicted mature protein sequences diverge substantially from one another, but the residues coordinating copper and constituting the radical redox site are conserved. Transcript profiles, microscopic examination, and lignin analysis of inoculated thin wood sections are consistent with differential regulation as decay advances. The cro2-encoded protein was detected by liquid chromatography-tandem mass spectrometry in defined medium. The cro2 cDNA was successfully expressed in Aspergillus nidulans under the control of the A. niger glucoamylase promoter and secretion signal. The recombinant CRO2 protein had a substantially different substrate preference than GLX. The role of structurally and functionally diverse cro genes in lignocellulose degradation remains to be established.

Transcriptome and Secretome Analyses of the Wood Decay Fungus Wolfiporia cocos Support Alternative Mechanisms of Lignocellulose Conversion

“…This suggests that oxalate decarboxylase could have a role in modulating iron redox reactions, in addition to iron homeostasis. In regard to peroxide production in W. cocos cultures, CRO5 is a likely candidate based on its homology with GLX, a phylogenetically related but distinct copper radical oxidase (2,37). However, in contrast to the case with GLX (43), nothing is known of the substrate specificity of CRO5.…”

“…Possibly utilizing methanol from lignin demethylation during incipient brown rot decay, the enzyme has been implicated in hydroxyl radical generation via H 2 O 2 production (36). In addition, four H 2 O 2 -generating copper radical oxidases (37) were also expressed. Of these, CRO5 was highly expressed and, impressively, the fourth most highly upregulated gene among 11,191 detected in Asp (Table 2; see also Data Set S1).…”

Influence of Populus Genotype on Gene Expression by the Wood Decay Fungus Phanerochaete chrysosporium

“…In fact, eight related genes were localized to a 32-kb region which contains Phach1_140680, Phach1_7965, Phach1_ 1321, and Phach1_32896. Clustering of functionally related genes in P. chrysosporium had been previously observed for LiP-and CRO-encoding genes (46,47), but regulation is not strictly coordinated among these tightly linked sequences. Thus, a putative flavin-containing monooxygenase (Phlgi_6283) is 89% identical to Phlgi_132896 and similarly expressed on line 64 (Table 2), and yet it resides on a separate scaffold.…”

Comparative Transcriptome and Secretome Analysis of Wood Decay Fungi Postia placenta and Phanerochaete chrysosporium

“…Proteins corresponding to a copper radical oxidase (Ppl56703), an FADlinked oxidoreductase (Ppl122772), and the above-mentioned GMC oxidoreductase (Ppl128830) were accompanied by relatively high transcript levels, but regulated expression levels that increased Ͼ2-fold were not observed. The Postia CRO protein is similar to three P. chrysosporium copper radical oxidases (CRO3, CRO4, and CRO5), with N-terminal repeats of a highly conserved WSC domain (55). None of the seven P. chrysosporium CRO proteins was detected by MS/MS in BMA cultures.…”