MOLECULAR-CLONING AND TRANSCRIPTIONAL REGULATION OF THE ASPERGILLUS-NIDULANS XLND GENE ENCODING A BETA-XYLOSIDASE

The xlnD gene encoding the 85-kDa beta-xylosidase was cloned from Aspe rgillus nidulans. The deduced primary structure of the protein exhibit s considerable similarity to the primary structures of the Aspergillus niger and Trichoderma reesei beta-xylosidases and same similarity to the primary structures of the class 3 beta-glucosidases. xlnD is regul ated at the transcriptional level; it is induced by xylan and D-xylose and is repressed by D-glucose. Glucose repression is mediated by the product of the creA gene, Although several binding sites for the pH[ r egulatory protein PacC were found in the upstream regulatory region, i t was not clear from a Northern analysis whether PacC is involved in t ranscriptional regulation of xlnD.