An endogenous promoter for conditional gene expression in Acremonium chrysogenum: The xylan and xylose inducible promoter xyl1P

• Identification and characterization of the Acremonium chrysogenum xylanase-encoding xyl1 gene and its mode of expression.
• Employment of the xyl1 promoter for the conditional expression of heterologous genes.
• First description of selection marker reuse in A. chrysogenum.

Acremonium chrysogenum is the natural producer of the beta-lactam antibiotic cephalosporin C and therefore of significant biotechnological importance. Here we identified and characterized the xylanase-encoding xyl1 gene and demonstrate that its promoter, xyl1P, is suitable for conditional expression of heterologous genes in A. chrysogenum. This was shown by xylose and xylan-inducible xyl1P-driven expression of genes encoding green fluorescence protein and phleomycin resistance. Moreover, we demonstrate the potential of the xyl1P promoter for selection marker recycling. Taken together, these finding will help to overcome the limitation in genetic tools in this important filamentous fungus.