Studies on the quinic acid (qa) gene cluster of Neurospora Africana by Kimberly Anne Rutledge.

Abstract

The qa-IS-qa-IF intergenic sequence of N. afrieana was chosen for study because this region may playa role in the carbon catabolite repression of the genes within the quinic acid (qa) gene cluster. Evidence has indicated that expression of the GAL genes, within the galactose pathway of S. eerevisiae , is reduced in the presence of a preferred carbon source such as glucose. This process results from the inability of the GAL4 activator protein to bind to its GAL4 binding sites within the GAL promoters. However, the exact mechanism of GAL4 inhibition is unknown. A similar mechanism may occur within the qa gene cluster of N. erassa. In the presence of a preferred carbon source, qa gene expression is repressed. Asch and Case (1992) provided evidence that some qa genes were slightly repressed in the presence of glucose, while other qa genes were higWy repressed. The qaIF activator gene was amongst the highly repressed genes. The exact mechanism of catabolite repression is unclear. We attempted to study the qa-IS-qa-IF intergenic sequence of N. afrieana because this region may influence the qa gene repression in the presence of glucose. Two plasmid clones, pR1 and pRX2, were established. Plasmid pR1 contains a 3.8-kb insert spanning the entire qa-IS-qa-IF region of N. afrieana. Whereas, plasmid pRX2 contains a 2.7-kb fragment spanning a portion of the qa-IS-qa-IF intergenic region. Southern blot analysis of both plasmids pR1 and pRX2 confirmed that these clones contain the qa-IS-qa-IF intergenic sequence. Sequence analysis of the plasmid pR1, using the M13/pUC reverse primer, determined the qa-IF end of the 3.8-kb insert. Although sequencing of both plasmids was limited, the established clones were characterized and can be used in future experiments.