Glucose-Mediated Repression of Plant Biomass Utilization in the White-Rot Fungus Dichomitus squalens
The extent of carbon catabolite repression (CCR) at a global level is unknown in wood-rotting fungi, which are critical to the carbon cycle and are a source of biotechnological enzymes. CCR occurs in the presence of sufficient concentrations of easily metabolizable carbon sources (e.g., glucose) and involves downregulation of the expression of genes encoding enzymes involved in the breakdown of complex carbon sources. We investigated this phenomenon in the white-rot fungusDichomitus squalensusing transcriptomics and exoproteomics. InD. squalenscultures, approximately 7% of genes were repressed in the presence of glucose compared to Avicel or xylan alone. The glucose-repressed genes included the essential components for utilization of plant biomass—carbohydrate-active enzyme(CAZyme) and carbon catabolic genes. The majority of polysaccharide-degrading CAZyme genes were repressed and included activities toward all major carbohydrate polymers present in plant cell walls, while repression of ligninolytic genes also occurred. The transcriptome-level repression of the CAZyme genes observed on the Avicel cultures was strongly supported by exoproteomics. Protease-encoding genes were generally not glucose repressed, indicating their likely dominant role in scavenging for nitrogen rather than carbon. The extent of CCR is surprising, given thatD. squalensrarely experiences high free sugar concentrations in its woody environment, and it indicates that biotechnological use ofD. squalensfor modification of plant biomass would benefit from derepressed or constitutively CAZyme-expressing strains. White-rot fungi are critical to the carbon cycle because they can mineralize all wood components using enzymes that also have biotechnological potential. The occurrence of carbon catabolite repression (CCR) in white-rot fungi is poorly understood. Previously, CCR in wood-rotting fungi has only been demonstrated for a small number of genes. We demonstrated widespread glucose-mediated CCR of plant biomass utilization in the white-rot fungusDichomitus squalens. This indicates that the CCR mechanism has been largely retained even though wood-rotting fungi rarely experience commonly considered CCR conditions in their woody environment. The general lack of repression of genes encoding proteases along with the reduction in secreted CAZymes during CCR suggested that the retention of CCR may be connected with the need to conserve nitrogen use during growth on nitrogen-scarce wood. Finally the widespread repression indicates that derepressed strains could be beneficial for enzyme production.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); Netherlands Scientific Organization; Academy of Finland
- Grant/Contract Number:
- AC02-05CH11231; NWO 824.15.023; 308284
- OSTI ID:
- 1619143
- Journal Information:
- Applied and Environmental Microbiology, Vol. 85, Issue 23; ISSN 0099-2240
- Publisher:
- American Society for MicrobiologyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Evidence for ligninolytic activity of the ascomycete fungus Podospora anserina
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journal | April 2020 |
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