Introduction of heterologous transcription factors and their target genes into Penicillium oxalicum leads to increased lignocellulolytic enzyme production.

Genetic engineering of transcription factors is an efficient strategy to improve lignocellulolytic enzyme production in fungi. In this study, the xylanase transcriptional regulators of Trichoderma reesei (Xyr1) and Neurospora crassa (XLR-1), as well as their constitutively active mutants (Xyr1 and XLR-1), were heterologously expressed in Penicillium oxalicum. The two heterologous regulators were identified to be able to activate lignocellulolytic enzyme gene expression in P. oxalicum. Particularly, expression of T. reesei Xyr1 resulted in a higher cellulase production level compared with the expression of native xylanase transcriptional regulator XlnR using the same promoter. Xyr1 and XLR-1 were found to be able to confer P. oxalicum more enhanced lignocellulolytic abilities than wild-type regulators Xyr1 and XLR-1. Furthermore, introduction of regulatory modules containing Xyr1/XLR-1 and their target cellulase genes resulted in greater increases in cellulase production than alone expression of transcriptional regulators. Through the cumulative introduction of three regulatory modules containing regulator mutants and their corresponding target cellulase genes from P. oxalicum, T. reesei, and N. crassa, a 2.8-fold increase in cellulase production was achieved in P. oxalicum.