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 β-glucosidase enzymes and one intracellular β-glucosidase lacks β-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 β-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.

Two Major Facilitator Superfamily Sugar Transporters from Trichoderma reesei and Their Roles in Induction of Cellulase Biosynthesis

“…Other than direct import of the degradation products from cellulose into cytoplasm, sensing these products may also involve a specific membrane anchored receptor (6,29,30). In the present study, a putative sugar transporter Crt1 belonging to the major facilitator superfamily was also identified.…”

NMR structure of a lytic polysaccharide monooxygenase provides insight into copper binding, protein dynamics, and substrate interactions

“…Considering the dominance of LPMOs in the secretomes of biomass-degrading microorganisms (18), the abundance of LPMOencoding genes in such organisms, and the documented beneficial effects of LPMOs on biomass conversion, it seems that we have only seen the beginning of what may be a very important development in enzymatic biomass refining. Many important aspects of these recently discovered enzymes remain unresolved, including the catalytic mechanism and the structural determinants of substrate specificity.…”

Functional expression and characterization of a glucuronoyl esterase from the fungus <i>Neurospora crassa</i>: identification of novel consensus sequences containing the catalytic triad

“…and hemicellulose from the plant cell walls (Znameroski et al, 2012). In this report, we showed that the putative protein NCU09445.7 in N. crassa is actually a functional glucuronoyl esterase.…”