The localization of the qa-lS-qa-IF Intergenic Region of Neurospora africana, /

Abstract

Many microrganisms, III the presence of a preferred carbon source, repress genes which are used to metabolize other carbon sources, a process call carbon catabolite repression. Carbon catabolite repreSSIOn has been shown to operate within the quinic acid utilization pathway (qa) of Neurospora crassa. The mechanisms acting to cause this repression remain unknown. However, a strain of N. crassa containing a deletion of the qa -1 S repressor gene showed that some q a genes remained slightly repressed while others remained highly repressed, in the presence of a preferred carbon source. One of these directly repressed genes is the gene coding for the qa-1 F activator protein. To investigate this phenomenon the qa-1 S-qa-1 F intergenic regIOn of Neurospora africana was chosen for study. N. africana was chosen because the entire qa gene sequence of N. crassa is known and provided a comparison between the two species. First, subclones of plasmid pRl, which contained a 3.8 kb insert known to contain the qa-1S-qa-1F intergenic region of N. africana, were constructed. Southern blot analysis of the subclones plasmid pRXl and pRX2 revealed that the entire qa-1 S-qa-1 F intergenic region was contained within plasmid pRX2. Further sequence analysis revealed the existence of portions of the qa-1 F and qa-1 S genes and the location the intergenic region within the original 3.8 kb insert.