Opposite Patterns of Expression of Two Aspergillus nidulans Xylanase Genes with Respect to Ambient pH

The Aspergillus nidulans xylanase genes xlnA and xlnB are subject to regulation by ambient pH via the zinc finger transcription factor PacC. In the presence of d-xylose, xlnA is expressed under conditions of alkaline ambient pH while xlnB is expressed at acidic ambient pH. These data have been confirmed for acidity- and alkalinity-mimicking A. nidulans mutants.