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Reactive oxygen species generated by microbial NADPH oxidase NoxA regulate sexual development in Aspergillus nidulans
Author(s) -
LaraOrtíz Teresa,
RiverosRosas Héctor,
Aguirre Jesús
Publication year - 2003
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2003.03800.x
Subject(s) - biology , nadph oxidase , aspergillus nidulans , reactive oxygen species , mutant , microbiology and biotechnology , oxidase test , peroxidase , gene , biochemistry , genetics , enzyme
Summary NADPH oxidases (Nox) have been characterized as higher eukaryotic enzymes used deliberately to produce reactive oxygen species (ROS). The recent discovery of new functional members of the Nox family in plants and animals has led to the recognition of the increasing importance of ROS as signals involved in regulation of diverse cellular processes such as defence, growth and signalling. Here, we address the role of NADPH oxidase‐generated ROS in the biology of the filamentous fungus Aspergillus nidulans . We characterize the noxA gene and show that it encodes a member of a novel NADPH oxidase subfamily ubiquitous in lower eukaryotes. Deletion of noxA specifically blocks differentiation of sexual fruit bodies (cleistothecia), without affecting hyphal growth or asexual development. Accordingly, the noxA gene is induced during sexual development, peaking at the time of cleistothecia differentiation and in parallel with the hülle cell‐associated catalase peroxidase gene cpeA . This expression pattern is not dependent on transcription factors SteA and StuA, which are essential for cleistothecia formation. In contrast, noxA ‐dependent premature sexual development correlates with noxA derepression in ΔsakA null mutants, connecting stress MAPK signalling to the regulated production of ROS. Using a nitroblue tetrazolium (NBT) assay to detect superoxide, we found that hülle cells and cleistothecia initials produce superoxide in a process inhibited by NADPH oxidase inhibitor DPI and markedly reduced in ΔnoxA mutants. Furthermore, using H 2 DCFDA, we detected that H 2 O 2 and possibly other ROS are generated in a NoxA‐dependent fashion, mainly in the external walls from cleistothecia initials. The essential role of NoxA‐generated ROS in A. nidulans sexual differentiation and the presence of one or two noxA homologues in all analysed filamentous fungi suggest that NADPH oxidase‐generated ROS play important roles in fungal physiology and differentiation.