The bgl1 gene of Trichoderma reesei QM 9414 encodes an extracellular, cellulose-inducible beta-glucosidase involved in cellulase induction by sophorose.
We have investigated the effect of disruption of the bgl1-(beta-glucosidase l-encoding) gene of Trichoderma reesei on the formation of other beta-glucosidase activities and on the induction of cellulases. To this end the bgl1 locus was disrupted by insertion of the Aspergillus nidulans amdS (acetamidase-encoding) gene. The bgl1-disrupted strain did not produce the 75 kDa extracellular beta-glucosidase on cellulose or lactose, but still formed beta-glucosidase activity on glucose, cellobiose, xylan or beta-1,3-glucan, suggesting that the enzyme(s) exhibiting this beta-glucosidase activity is (are) not encoded by bgl1. The cellulase-inducer sophorose induced the bgl1-encoded beta-glucosidase, whereas the remaining beta-glucosidase activity was induced by methyl-beta-D-glucoside. The bgl1-gene product was mainly secreted into the medium, whereas the other beta-glucosidase activity was mainly associated with the cells. A bgl1-multicopy strain formed higher amounts of cellulases than the parent strain. Nonsaturating concentrations of sophorose efficiently induced cellobiohydrolase l formation in the bgl1-multicopy strain, but less efficiently in the bgl1-disrupted strain. The multicopy strain and the parent strain were comparably efficient at saturating sophorose concentrations. The beta-glucosidase inhibitor nojirimycin strongly inhibited induction in all strains. These data suggest that the bgl1-encoded beta-glucosidase is not identical to the plasma-membrane-bound, constitutive, methyl-beta-glucoside inducible beta-glucosidase, but represents an extracellular cellulose-induced enzyme. Both enzymes contribute to rapid induction of cellulases by modifying the inducer sophorose.
D001483:Base Sequence; D002480:Cellulase / Q000096:biosynthesis*; D002482:Cellulose / Q000494:pharmacology; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D004790:Enzyme Induction / Q000187:drug effects; D005784:Gene Amplification; D015870:Gene Expression / Q000187:drug effects; D005800:Genes, Fungal; D005936:Glucans / Q000494:pharmacology; D008757:Methylglucosides / Q000494:pharmacology; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D014242:Trichoderma / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D001617:beta-Glucosidase / Q000096:biosynthesis / Q000235:genetics*
D017931:DNA Primers; D004271:DNA, Fungal; D005936:Glucans; D008757:Methylglucosides; C027020:methylglucoside; D002482:Cellulose; D001617:beta-Glucosidase; D002480:Cellulase; C003328:sophorose