Achieving efficient protein expression in Trichoderma reesei by using strong constitutive promoters

The transcriptional profiles of 13 key genes that participate in glucose metabolism in T. reesei were analyzed by quantitative real-time reverse-transcription polymerase chain reaction (RT-qPCR). The results indicated that the mRNA levels of pdc (encoding pyruvate decarboxylase) and eno (encoding enolase) genes were much higher than other genes under high glucose conditions. Recombinant T. reesei strains that homologously expressed xylanase II were constructed by using the promoters of the pdc and eno genes, and they respectively produced 9266？IU/ml and 8866？IU/ml of xylanase activities in the cultivation supernatant in a medium with high glucose concentration. The productivities of xylanase II were 1.61？g/L (with the pdc promoter) and 1.52？g/L (with the eno promoter), approximately accounted for 83% and 82% of the total protein secreted by T. reesei, respectively.This work demonstrates the screening of constitutive promoters by using RT-qPCR in T. reesei, and has obtained the highest expression of recombinant xylanase II to date by using these promoters.