AreB, the nitrogen and carbon regulator in Aspergillus nidulans
Nitrogen and carbon repression general regulatory systems modulate the expression of target genes participating in utilization of alternative nitrogen/carbon sources, resulting in transcription only when preferred sources are limiting. In Aspergillus nidulans, the GATA transcription factor AreB was identified as nitrogen regulator (Conlon et al., 2001) but its activity depends on both nitrogen and carbon source (Dzikowska et al., 2012).
Transcriptomic analysis of areB deletion strain grown under different carbon/nitrogen conditions has shown that areB participates both in nitrogen and carbon regulation. Observed effects are, at least partially, indirect as the expression of several transcription factor coding genes is changed in areB deletion strain.
areB gene encodes three different proteins which differ at their N-terminal part. This results from a differential splicing and selection of two different promoter regions and start codons. To explore the mechanism of transcription regulation by areB we analyzed the changes in expression levels of three areB transcripts (areBα, areBβ, areBγ) grown under carbon/nitrogen repressing/de-repressing conditions. The qPCR analysis shows that the three areB transcripst are expressed in different proportions and this depends on carbon/nitrogen conditions.