Overexpression of GaaR, a D-galacturonic acid responsive transcription factor, enables inducer-independent production of pectinases in Aspergillus niger

The transcription factor GaaR is needed for the expression of genes required for pectin degradation, and transport and catabolism of the main degradation product, D-galacturonic acid (GA) in Aspergillus niger. In this study, we overexpressed GaaR in A. niger from the strong constitutive A. nidulans gpdA promoter. Overexpression of GaaR resulted in an increased transcription of the genes encoding pectinases, GA transporters and catabolic pathway enzymes even under non-inducing conditions, i.e. in the absence of GA.