Unusual Transcription Regulation of the<i>niaD</i>Gene under Anaerobic Conditions Supporting Fungal Ammonia Fermentation

Abstract

The niaD gene of the fungus Aspergillus nidulans encodes an assimilatory nitrate reductase and exogenous ammonium represses its expression. Under anoxic conditions, however, A. nidulans expressed niaD even in the presence of ammonium and used the gene product for dissimilatory nitrate reduction (ammonia fermentation). This transcription regulation mechanism under anaerobiosis is critical for the fungus to ferment ammonium.