The filamentous fungi Aspergillus nidulans is an obligate aerobe, and therefore generates its main energy requirements by means of oxidative respiration, using the cytochrome c respiratory pathway. This is in contrast to the yeast Saccharyomyces cerevisiae, which can grow without oxygen. S. cerevisiae switches off the production of many oxidative respiratory components (such as cytochrome c) when energy can be produced by alternative means (fermentation) which do not require oxygen. Surprisingly, A. nidulans appears to regulate the production of cytochrome c in a similar manner, even though it appears to have an absolute requirement for oxygen. A functional analysis of the A. nidulans cytochrome c gene (cycA) promoter is currently being carried out to determine the molecular basis of regulation of the gene. In particular, the focus will be on the HAP I and HAP2 regulatory proteins, which are known to affect cytochrome c expression in yeast, since consensus sequences for the binding sites of these proteins have been found in the cycA promoter, and the gene is known to be transcriptionally induced by oxygen. Another intriguing observation is that cytochrome c deficient mutants of A. nidulans which were created at Massey University by targeted gene disruption (Bird, 1996) are viable upon fermentable carbon sources. These results suggest the mutant strains must be using alternative means of energy production which do not require cytochrome c. The extent to which these mutant strains (as well as wildtype strains) are utilising an alternative respiratory pathway and fermentation has been investigated using respiratory measurements and ethanol assays, respectively.
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)