Iron starvation leads to increased expression of Cu/Zn-superoxide dismutase in Aspergillus

In a search for iron-regulated proteins of Aspergillus nidulans and Aspergi llus fumigatus a 16-kDa protein was identified which is about 5-fold upregu lated during iron starvation in both species and which can be approximately 500-fold enriched by simple one-step chromatography on Amberlite XAD-16 re sin, N-terminal protein sequence analysis and cloning of the respective A. nidulans cDNA identified this protein as a Cu/Zn-superoxide dismutase (SODA ), Northern analysis revealed that upregulation of sodA expression occurs a t the level of transcript accumulation. This seems to be a specific low iro n response and not a general starvation answer since sodA transcript levels do not respond to carbon or nitrogen starvation, In contrast, copper deple tion leads to transcriptional downregulation of sodA. Furthermore, sodA exp ression was found still to be subject to iron regulation in an A. nidulans mutant lacking SREA, a regulator of iron homeostasis, indicating that sodA expression is regulated by an SREA-independent mechanism, The data presente d suggest that SODA plays a protective role under iron deplete conditions. (C) 2000 Federation of European Biochemical Societies. Published by Elsevie r Science B.V. All rights reserved.