Genetic organization and transcriptional regulation in the qa gene cluster of Neurospora crassa.

A transcription map of the qa gene cluster of Neurospora crassa has been constructed by using cloned DNA fragments as hybridization probes. The mRNAs encoded in the previously identified qa-2 (3-dehydroquinate hydro-lyase, EC 4.2.1.10), qa-4 (dehydroshikimate dehydratase), qa-3 (quinate:NAD+ 3-oxidoreductase, EC 1.1.1.24), and qa-1 (regulatory protein) genes have been characterized. In addition, mRNAs encoded in two new genes in this cluster (qa-x, qa-y) have been identified. Regulation of this system occurs at the level of transcription and is under the combined control of quinic acid and the qa-1 protein. The qa cluster represents a group of adjacent coding sequences which occupy approximately 18 kilobases in linkage group VII. The expression of the qa-1 gene appears to be constitutive but also autoregulated. mRNAs encoded in genes flanking the qa gene cluster have also been identified.