Catalases are H2O2-detoxifying enzymes present in most living organisms that use H202, as a unique substrate. We study catalase gene expression as part of a general project aimed at demonstrating a causal relationship between oxidative stress and development (Hansberg and Aguirre, 1990). Two catalase genes, designated catA (Navarro et al., 1996) and catB (Kawasaki et al.,1997) have been characterized in A. nidulans. More recently, a third catalase (CatC) has been detected using catA/catB double mutants. Why are different enzymes required to carry out the same reaction?. Part of the answer is related to the fact that these catalases are differentially expressed both, in time and space, throughout the life cycle. The catA gene encodes catalase A, which is specifically localized to asexual and sexual spores, whereas catalase B is induced during stationary phase of growth, conidiation and oxidative stress. Part of catalases A and B have been',. immunolocalized to the cell wall of conidia and hyphae, respectively. Mutants affected in catA or catB are sensitive to H2O2 at different stages of A. nidulans life cycle. How is this differential regulation accomplished?. We have found that the catA mRNA accumulates in response to different types of stress. However, translation of the.mRNA is coupled to the spore formation, in a process mediated by the catA mRNA 5' UTR region. On the other hand, the catB gene is regulated at the transcriptional level. A 580-by region of the catB promoter necessary for regulation during stationary phase and oxidative stress has been defined. The study of catA, catB and eventually catC, will allow us to understand an important part of the antioxidant response and the mechanisms of gene regulation that operate during development. Partially supported by grant No. IN206097 from PAPIIT-UNAM, Mexico.
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)