Involvement of a Conidial Endoglucanase and a Plasma-membrane-bound β-Glucosidase in the Induction of Endoglucanase Synthesis by Cellulose in Trichoderma reesei

Summary: The induction of endo-1,4-β-glucanase synthesis by Trichoderma reesei QM 9414 was investigated in conidia, mycelia and protoplasts. Cellulose induced endoglucanase synthesis only in conidia, but not in glucose-grown mycelia or protoplasts. Cellooligosaccharides and sophorose induced endoglucanase synthesis in mycelia, conidia and protoplasts. Only conidia exhibited detectable basal endoglucanase levels, whereas β-glucosidase activity was found in conidia, mycelia and protoplasts. The β-glucosidase was inhibited in vitro by nojirimycin and glucono-δ-lactone. Addition of either of these inhibitors to the induction medium blocked de novo synthesis of endo-1,4 β-glucanase with cellulose (conidia) or cellooligosaccharides (protoplasts and mycelia) as inducer, whereas induction by sophorose remained unaffected. The results are consistent with the assumption that basal constitutive levels of endoglucanase and β-glucosidase are involved in the induction of cellulase synthesis by cellulose in T. reesei.