Fig. 7
Hypothesis about the role of CRT1 in cellulase induction. a Scouting activity of cellulases results in the formation of small amount of inducing sugar (cellobiose or sophorose). The sugar is imported by CRT1 and sensed by some unknown component of the induction system with high affinity for the inducer. Binding of the inducer to this component causes the cellulase induction. b Among cellulases, lower affinity cellobiose transporters and other transporters (arabinose, xylose, etc.) get induced, resulting in the transport of bulk of the sugars released from the lignocellulose feedstock. c Accumulation of glucose inside the cells by \(\upbeta\)-glucosidase activity and by the scouting high-affinity hexose transporters causes the carbon catabolite repression to limit cellulase production