The effects of ClrB internal mutant overexpression and creA deletion on the transcriptome of Penicillium oxalicum

The synthesis of cellulolytic enzymes by filamentous fungi are mainly regulated at the transcriptional level. The essential role of transcriptional activator ClrB/CLR-2 in the induction of cellulase genes has been reported in several fungal species. In this study, we identified the C-terminal region of ClrB in Penicillium oxalicum as a transcriptional activation domain using a yeast reporter gene system. Overexpression of a mutant ClrBID fusing the DNA-binding and transcriptional activation domains of ClrB together enabled cellulase production under cellulase non-inducing conditions. Strikingly, the ClrBID-overexpression strain produced cellulase in the presence of glucose at a level similar to that of reference strain on cellulose. Combination of ClrBID overexpression and deletion of carbon catabolite-repressor gene creA suggested an additive effect of the two manipulations on carbon catabolite de-repression. A similar modification of ClrB in Aspergillus niger also resulted in cellulase production on glucose. The results indicated that the post-transcriptional control of ClrB activity involves its central region, and provided a potential strategy for engineering Penicillium and Aspergillus strains for cellulase production on easy-to-use carbon sources. A total of 15 samples were analzyed, which include biological triplicates. The reference strain M12 was considered as a control.