Project description:Lignin is a biopolymer found in plant cell walls that accounts for 30% of the organic carbon in the biosphere. White-rot fungi (WRF) are considered the most efficient organisms at degrading lignin in Nature. While lignin depolymerization by WRF has been exhaustively studied, the possibility that WRF are able to utilize lignin as a carbon source is still a matter of controversy. Here we employ 13C-labeling and systems biology approaches to demonstrate that two WRF, Trametes versicolor and Gelatoporia subvermispora, funnel lignin-derived aromatic compounds into central carbon metabolism via intracellular catabolic pathways. These results provide insights into global carbon cycling in soil ecosystems, and furthermore establishes a foundation for employing WRF in simultaneous lignin depolymerization and bioconversion to bioproducts – a key step towards enabling a sustainable bioeconomy.
Project description:White-rot fungi (WRF), considered the most efficient organisms at degrading organic carbon in the biosphere, are found in plant cell wall lignin biopolymer. We employ multi-omics to demonstrate that Trametes versicolor and Gelatoporia subvermispora funnel lignin-derived aromatic compounds into central carbon metabolism via intracellular catabolic pathways. These results provide insights into global carbon cycling in soil ecosystems.
Project description:We propose to elucidate new metabolic pathways in fungi - with a special focus on white rot fungi (WRF)- involved in the catabolism of lignin-derived aromatic compounds. Basidiomycete fungi, in particular WRF, are the most efficient organisms for the depolymerization and mineralization of lignin to CO2 and H2O in Nature and thus, WRF play a pivotal role in carbon cycling. Lignin depolymerization by WRF is mediated by the action of extracellular oxidative ligninolytic enzymes, such as laccases and peroxidases, alongside other secreted metabolites. This extracellular process has been studied for decades via analysis of lignin modifications, ligninolytic enzyme activity in fungal broths, enzyme isolation and characterization, and more recently through multi-omics analyses. Despite the massive research effort directed toward understanding how WRF depolymerize lignin, almost no attention has been dedicated to the elucidation of the intracellular metabolism of WRF in catabolizing lignin. In fact, whether or not WRF are able to catabolize lignin remains a matter of discussion and debate.
The work (proposal:https://doi.org/10.46936/10.25585/60001176) conducted by the U.S. Department of Energy Joint Genome Institute (https://ror.org/04xm1d337), a DOE Office of Science User Facility, is supported by the Office of Science of the U.S. Department of Energy operated under Contract No. DE-AC02-05CH11231.
Project description:Wood-degrading fungi play a critical role in global carbon cycling, and their varied mechanisms for deconstruction offer pathways for industrial bioconversion. In this study, we used comparative genomics to isolate upregulation patterns among fungi with brown rot (carbohydrate-selective) or white rot (lignin-degrading) nutritional modes. Specifically, we used whole-transcriptome profiling to compare early, middle, and late decay stages on wood wafers, matching differentially-expressed gene (DEG) patterns with fungal growth and enzyme activities. This approach highlighted 34 genes uniquely upregulated in early brown rot stages, with notable candidates involved in generating reactive oxygen species (ROS) as a pretreatment mechanism during brown rot. This approach further isolated 18 genes in late brown rot stages that may be adapted to handle oxidatively-reacted lignocellulose components. By summing gene expression levels in functional classes, we also identified a broad and reliable distinction in glycoside hydrolase (GH) versus lignocellulose oxidative (LOX) transcript counts that may reflect the energy investment burden of lignin-degrading machinery among white rot fungi.
Project description:To determine the wood degradation mechanism and its key genes of Lenzites gibbosa, we sequenced 15 transcriptomes of mycelial samples under woody environments at 3, 5, 7, and 11 d (D3, D5, D7, and D11) and non-woody environments (CK). All the transcripts were annotated as much as possible in eight databases to determine their function. The key genes and biological processes, relating to wood degradation, were predicted and screened. A total of 2069 differentially expressed genes (DEGs) were obtained in ten differential groups. Comparing wood with non-wood treatment conditions, the key genes were those participating in oxidation-reduction process, they were oxidoreductases and peroxidases genes, and their regulators genes; these genes mainly focused on the three biological processes of carbohydrate metabolism, lignin catabolism, and secondary metabolites biosynthesis, transport and catabolism. The mostly enriched subcategories in molecular function were oxidoreductase activity, peroxidase activity, and heme binding in GO annotation. One cellulose and hemicellulose degradation pathway and seven pathways related to lignin-derived aromatic compounds degradation or late lignin degradation were found. In conclusion, during the process of L. gibbosa growing on wood, gene expression at the transcriptional level indicated that lignin catabolism and hyphal growth were promoted, but the metabolism of carbon and carbohydrates including cellulose in lignocellulose in overall trend was inhibited to some extent. The results have important reference value for the study of degradation mechanism of wood white rot.
Project description:The basidiomycete white-rot fungus Obba rivulosa, a close relative of Gelatoporia (Ceriporiopsis) subvermispora, is an efficient degrader of softwood. The dikaryotic O. rivulosa strain T241i (FBCC949) has been shown to selectively remove lignin from spruce wood prior to depolymerization of plant cell wall polysaccharides, thus possessing potential in biotechnological applications such as pretreatment of wood in pulp and paper industry. In this work, we studied the time-course of the conversion of spruce by the genome-sequenced monokaryotic O. rivulosa strain 3A-2, which is derived from the dikaryon T241i, to get insights to transcriptome level changes during prolonged solid state cultivation. During 8-week cultivation, O. rivulosa expressed a constitutive set of genes encoding putative plant cell wall degrading enzymes. High level of expression of the genes targeted towards all plant cell wall polymers was detected at 2-week time point, after which majority of the genes showed reduced expression. This implicated non-selective degradation of lignin by the O. rivulosa monokaryon. These results suggest high variation between mono- and dikaryotic strains of the white-rot fungi with respect to their abilities to convert plant cell wall polymers.
Project description:Unique ability of basidiomycete white rot fungi to degrade all components of plant cell walls makes them indispensable organisms in global carbon cycle. In this study, we analyzed proteomes of two closely related white rot fungi, Obba rivulosa and Gelatoporia subvermispora, while growing on solid spruce wood, and defined a core set of CAZymes that was shared between these species including the orthologous enzymes. Similar production pattern of these CAZymes indicate their key role in plant biomass degradation and need for their further biochemical characterization. The obtained results give an insight into specific enzymes and enzyme sets that are produced during the degradation of solid spruce wood. These findings expand the knowledge on enzyme production in nature-mimicking conditions and may contribute to exploitation of white rot fungi and their enzymes in biotechnological applications.