Gene Organization and Regulation in Neurospora Crassa. Evidence from the Cloning and Transformation of the qa Gene Cluster

Abstract

An analysis of the qa. gene cluster in Neurospora offers an excellent opportunity for understanding the organization and regulation of a eukaryotic gene cluster. This cluster is involved in the catabolism of quinic acid and encodes three closely linked structural genes, qa-2, qa-3, and qa-4, and a positively acting regulatory gene, qa-1, Fig. 1 (Giles et al., 1978). The (qa gene cluster is very tightly linked to me-7 on the right arm of LG VII and so far has proved to be inseparable from the centromere. The qa-2 gene encodes catabolic dehydroquinase; the qa-3 gene, quinate dehydrogenase; and the qa-4 gene, 5-dehydroshikimate dehydratase, Fig. 1. The qa-2 gene was cloned by complementation of an aroD - strain of E. coli which lacks activity for the biosynthetic dehydroquinase (Vapnek et al., 1977). The entire qa gene cluster has been cloned on a 19 kb fragment utilizing the cosmid technique (Collins and Hohn, 1980) and selecting for qa-2 + complementation in E. coli (Schweizer et al., 1981). In E. coli, only the qa-2 + gene is expressed. The qa-3 + , qa-4 + and qa-1 + genes were detected on the basis of transformation back into Neurospora with these cosmid clones.