The transcription factor Roc1 is a regulator of cellulose degradation in the wood-decaying mushroom Schizophyllum commune

Abstract

Wood-decaying fungi of the class Agaricomycetes (phylum Basidiomycota) are saprotrophs that break down lignocellulose and play an important role in the nutrient recycling. They secrete a wide range of extracellular plant cell wall degrading enzymes that break down cellulose, hemicellulose and lignin, the main building blocks of plant biomass. Although the production of these enzymes is regulated mainly at the transcriptional level, no activating regulators have been identified in any wood-decaying fungus in the class Agaricomycetes. We studied the regulation of cellulase expression in the wood-decaying fungus Schizophyllum commune. Comparative genomics and transcriptomics on two wild isolates revealed a Zn2Cys6-type transcription factor gene (roc1) that was highly up-regulated during growth on cellulose, when compared to glucose. It is only conserved in the class Agaricomycetes. A roc1 knockout strain showed an inability to grow on medium with cellulose as sole carbon source, and growth on cellobiose and xylan (other components of wood) was inhibited. Growth on non-wood-related carbon sources was not inhibited. Cellulase activity was reduced in the growth medium of the Δroc1 strain. ChIP-Seq identified 1474 binding sites of the Roc1 transcription factor. Promoters of genes involved in lignocellulose degradation were enriched with these binding sites, especially those of LPMO (lytic polysaccharide monooxygenase) CAZymes, indicating that Roc1 directly regulates these genes. A GC-rich motif was identified as the binding site of Roc1, which was confirmed by a functional promoter analysis. Together, Roc1 is a key regulator of cellulose degradation and the first identified in wood-decaying fungi in the phylum Basidiomycota.

Pre-assembled Cas9 ribonucleoprotein-mediated gene deletion identifies the carbon catabolite repressor and its target genes in Coprinopsis cinerea

“…We also found that the C. cinerea ortholog (protein ID: 447627) of the S. commune roc1 transcription factor was significantly upregulated in both mutants. Roc1 was recently described as a regulator of cellulase genes in S. commune (Marian et al ., 2021). Similarly, a heat shock factor-type gene (protein ID: 523533) related to the S. cerevisiae skn7 transcription factor was upregulated in both mutants.…”

“…These transcription factors include ones specifically responsible for the activation of substrate-specific sets of enzyme-encoding PCWDEs, such as xylanases, cellulases, pectinases (Benocci et al ., 2017, Thieme et al ., 2017, Klaubauf et al ., 2014). While several TFs regulating specific PCWDE genes have been described in the Ascomycetes, only a single gene, Roc1 of S. commune (Marian et al ., 2021) has been associated with cellulose degradation in the Basidiomycota. Our data revealed several transcription factors that are differentially expressed in C. cinerea cre1 mutants, providing candidates for novel TFs related to plant biomass utilisation.…”

“…First, the C. cinerea ortholog of Roc1 ortholog is upregulated in both independent C. cinerea cre1 mutants. The Schizophyllum commune transcription factor gene roc1 , which is conserved among Agaricomycetes, was strongly upregulated in the cellulose containing medium and knockouts showed reduced growth on the cellulose medium, demonstrating its importance in regulating cellulose degrading genes (Marian et al ., 2021). ChIP-Seq analysis of S. commune Roc1 identified promoters of genes involved in lignocellulose degradation, particularly LPMOs (Marian et al ., 2021).…”

“…The Schizophyllum commune transcription factor gene roc1 , which is conserved among Agaricomycetes, was strongly upregulated in the cellulose containing medium and knockouts showed reduced growth on the cellulose medium, demonstrating its importance in regulating cellulose degrading genes (Marian et al ., 2021). ChIP-Seq analysis of S. commune Roc1 identified promoters of genes involved in lignocellulose degradation, particularly LPMOs (Marian et al ., 2021). The upregulation of the C. cinerea Roc1 ortholog in C. cinerea cre1 mutants may reveal a conserved link between the two transcription factors in regulating lignocellulose degradation.…”

Evolutionary genetics of nonself recognition regarding social and sexual interactions of fungi

“…Strains and culture conditions: three strains of Schizophyllum commune were used. The reference strain 4.8A, as well as LoenenD and TattoneD (Marian et al, 2021;. Strains were cultured at 25ºC on Schizophyllum Complete Media (SCM) except where noted below (Dons et al, 1979).…”