Dataset Information

Induction of lignocellulose-degrading enzymes in Neurospora crassa by cellodextrins.

ABSTRACT: Neurospora crassa colonizes burnt grasslands in the wild and metabolizes both cellulose and hemicellulose from plant cell walls. When switched from a favored carbon source such as sucrose to cellulose, N. crassa dramatically upregulates expression and secretion of a wide variety of genes encoding lignocellulolytic enzymes. However, the means by which N. crassa and other filamentous fungi sense the presence of cellulose in the environment remains unclear. Here, we show that an N. crassa mutant carrying deletions of two genes encoding extracellular ?-glucosidase enzymes and one intracellular ?-glucosidase lacks ?-glucosidase activity, but efficiently induces cellulase gene expression in the presence of cellobiose, cellotriose, or cellotetraose as a sole carbon source. These data indicate that cellobiose, or a modified version of cellobiose, functions as an inducer of lignocellulolytic gene expression in N. crassa. Furthermore, the inclusion of a deletion of the catabolite repressor gene, cre-1, in the triple ?-glucosidase mutant resulted in a strain that produces higher concentrations of secreted active cellulases on cellobiose. Thus, the ability to induce cellulase gene expression using a common and soluble carbon source simplifies enzyme production and characterization, which could be applied to other cellulolytic filamentous fungi.

SUBMITTER: Znameroski EA

PROVIDER: S-EPMC3341005 | biostudies-literature | 2012 Apr

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Induction of lignocellulose-degrading enzymes in Neurospora crassa by cellodextrins.

Znameroski Elizabeth A EA Coradetti Samuel T ST Roche Christine M CM Tsai Jordan C JC Iavarone Anthony T AT Cate Jamie H D JH Glass N Louise NL

Proceedings of the National Academy of Sciences of the United States of America 20120402 16

Neurospora crassa colonizes burnt grasslands in the wild and metabolizes both cellulose and hemicellulose from plant cell walls. When switched from a favored carbon source such as sucrose to cellulose, N. crassa dramatically upregulates expression and secretion of a wide variety of genes encoding lignocellulolytic enzymes. However, the means by which N. crassa and other filamentous fungi sense the presence of cellulose in the environment remains unclear. Here, we show that an N. crassa mutant ca ...[more]

PMID: 22474347

Similar Datasets

Project description:Plant cell walls are composed of cellulose, hemicellulose, and lignin, collectively known as lignocellulose. Microorganisms degrade lignocellulose to liberate sugars to meet metabolic demands. Using a metagenomic sequencing approach, we previously demonstrated that the microbiome of the North American porcupine (Erethizon dorsatum) is replete with genes that could encode lignocellulose-degrading enzymes. Here, we report the identification, synthesis and partial characterization of four novel genes from the porcupine microbiome encoding putative lignocellulose-degrading enzymes: ?-glucosidase, ?-L-arabinofuranosidase, ?-xylosidase, and endo-1,4-?-xylanase. These genes were identified via conserved catalytic domains associated with cellulose- and hemicellulose-degradation. Phylogenetic trees were created for each of these putative enzymes to depict genetic relatedness to known enzymes. Candidate genes were synthesized and cloned into plasmid expression vectors for inducible protein expression and secretion. The putative ?-glucosidase fusion protein was efficiently secreted but did not permit Escherichia coli (E. coli) to use cellobiose as a sole carbon source, nor did the affinity purified enzyme cleave p-Nitrophenyl ?-D-glucopyranoside (p-NPG) substrate in vitro over a range of physiological pH levels (pH 5-7). The putative hemicellulose-degrading ?-xylosidase and ?-L-arabinofuranosidase enzymes also lacked in vitro enzyme activity, but the affinity purified endo-1,4-?-xylanase protein cleaved a 6-chloro-4-methylumbelliferyl xylobioside substrate in acidic and neutral conditions, with maximal activity at pH 7. At this optimal pH, KM, Vmax, and kcat were determined to be 32.005 ± 4.72 ?M, 1.16x10-5 ± 3.55x10-7 M/s, and 94.72 s-1, respectively. Thus, our pipeline enabled successful identification and characterization of a novel hemicellulose-degrading enzyme from the porcupine microbiome. Progress towards the goal of introducing a complete lignocellulose-degradation pathway into E. coli will be accelerated by combining synthetic metagenomic approaches with functional metagenomic library screening, which can identify novel enzymes unrelated to those found in available databases.

Dataset Information

Induction of lignocellulose-degrading enzymes in Neurospora crassa by cellodextrins.

Publications

Induction of lignocellulose-degrading enzymes in Neurospora crassa by cellodextrins.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets