Catabolite repression directly affects transcription of the qa-y gene of Neurospora crassa.

The quinic acid (qa) gene cluster of Neurospora crassa is subject to two levels of gene control: a primary system which responds to the presence of quinic acid via the qa-1S repressor protein, and a secondary system which represses transcription of qa genes in the presence of a preferred carbon source, e.g. glucose. RNA blot analysis revealed that transcription of the qa-y gene, which encodes a quinic acid permease, was strongly repressed in the presence of glucose even in the absence of the qa-1S repressor protein, while transcription of the remaining qa cluster genes is repressed to a much lesser degree. DNA sequencing of the region upstream of the qa-y gene revealed a high degree of sequence conservation between N. crassa and the homothallic species Neurospora africana and Neurospora terricola. This may suggest the presence of conserved sequences that mediate catabolite repression in all three species.