Fig. 4

Construction of the peroxidase-FopAC expressing strains of A. niger. A Schematic diagram of the pod-fopAC expression cassette containing the promoter of the fopA gene (PfopA), the horseradish roots pod gene, the encoding sequence of the C-terminal domain of the fopA (fopAC), the trpC terminator (TtrpC), and the selection marker ptrA. The expression cassette was constructed as described in “Materials and methods” section. B Assay of peroxidase on the GOD-POD bienzymatic detection plate. The same concentrations of spores of the peroxidase-expressing transformants DPOC-1, DPOC-8, DPOC-9 and DPOC-11 were spotted on the CD plate. Then the amount of glucose released was detected by the GOD-POD bienzymatic system. Peroxidase activity was tested by a dark brown halo surrounding the colonies. A. niger ATCC 20611 was used as the control. C Relative expression of pod in the peroxidase-FopAC expressing transformants. Actin was used as a reference gene and the 2-^ΔΔCt method was used for calculating relative expression levels. D The peroxidase activities in the transformants. Error bars represent the standard deviation of three independent experiments. “a/b/c” above the bars indicate significant differences at P < 0.01. n.d., not detected