Fig. 8.

Hypothetical model of Tr69957-mediated cellulase induction in T. reesei. The figure shows the potential mechanism of signaling mediated by the sugar transporter Tr69957 under the control of cellulase expression. This scheme also shows the processes involved in regulating lignocellulosic enzymes in T. reesei. The major enzymes involved in mobilization of lignocellulosic material are endoglucanases (EGs), cellobiohydrolases (CBHs), and β-glucosidases. These enzymes act synergistically to break down biomass. Accessory enzymes such as swollenins and Lytic Polysaccharide Monooxygenases (LPMOs) are also important in this process. Due to its complexity, the degradation of lignocellulosic material involves other enzymes such as xylanases and mannanases that are able to break down the polysaccharides present in the plant biomass. The expression of all the degrading enzymes is controlled by the major transcription factors (TFs): XYR1, ACE1, ACE2, ACE3, BGL1, CRE1, and the HAP2/3/5 complex. These transcription factors can also regulate the expression of sugar transporters that are responsible for sugar uptake in response to different carbon sources. Early and late signaling involving the sugar transporter Tr69957 are indicated by black and red arrows, respectively