A. nidulans contains at least three catalases. Thus far, two genes have been cloned and characterized: catA and catB (Navarro et al., 1996; Kawasaki et al., 1997). Besides being developmentally regulated, CatB activity was induced by HO,, paraquat or uric acid catabolism but not by osmotic stress, whereas the third catalase activity has been detected only during late stationary phase. catB transcriptional regulation was studied by using a catB:: IacZ fusion containing 3.5 kb of catB 5'upstream regulatory sequences. The reporter gene activity was induced during the stationary phase of growth. Starting with the activity detected by 10h of growth, the beta-galactosidase activity was induced 4, 14 and 22 fold at 18h, 28h and 48h, respectively. Under oxidative stress conditions produced by a 2h paraquat treatment, the activity was induced 17 fold. A second lacZ fusion containing only 993 by of catB 5' upstream regulatory sequences behaved similarly within previous one. After we sequenced this region, a comparison analysis revealed several putative regulatory elements similar to consensus sequences shown to bind transcription factors involved in responses to different types of stress. These sequences are contained within a 580 by region, whose deletion clearly reduced catB::lacZ induction during stationary phase and oxidative stress. A more detailed analysis of this region is underway. We are also trying to isolate catB-deregulated mutants using a strain with two copies of the catB: : lacZ fusion. We expect this approach will allow us to define important regulators of the oxidative stress response in A. nidulans. Supported by grant 1N-206097 from PAPIT-UNAM, Mexico.
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)