Two NADPH oxidase isoforms are required for sexual reproduction and ascospore germination in the filamentous fungus Podospora anserina.
NADPH oxidases are enzymes that produce reactive oxygen species (ROS) using electrons derived from intracellular NADPH. In plants and mammals, ROS have been proposed to be second messengers that signal defence responses or cell proliferation. By inactivating PaNox1 and PaNox2, two genes encoding NADPH oxidases, we demonstrate the crucial role of these enzymes in the control of two key steps of the filamentous fungus Podospora anserina life cycle. PaNox1 mutants are impaired in the differentiation of fruiting bodies from their progenitor cells, and the deletion of the PaNox2 gene specifically blocks ascospore germination. Furthermore, we show that PaNox1 likely acts upstream of PaASK1, a MAPKKK previously implicated in stationary phase differentiation and cell degeneration. Using nitro blue tetrazolium (NBT) and diaminobenzidine (DAB) assays, we detect a regulated secretion of both superoxide and peroxide during P. anserina vegetative growth. In addition, two oxidative bursts are shown to occur during fruiting body development and ascospore germination. Analysis of mutants establishes that PaNox1, PaNox2, and PaASK1, as well as a still unknown additional source of ROS, modulate these secretions. Altogether, our data point toward a role for NADPH oxidases in signalling fungal developmental transitions with respect to nutrient availability. These enzymes are conserved in other multicellular eukaryotes, suggesting that early eukaryotes were endowed with a redox network used for signalling purposes.
Institut de Génétique et Microbiologie, UMR 8621, Bât. 400, Université de Paris XI, 91405 Orsay cedex, France.
Fabienne
F
Malagnac
Hervé
H
Lalucque
Gersende
G
Lepère
Philippe
P
Silar
D000595:Amino Acid Sequence; D001483:Base Sequence; D016384:Consensus Sequence; D017931:DNA Primers; D008969:Molecular Sequence Data; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D048468:Podospora / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D016133:Polymerase Chain Reaction; D012098:Reproduction / Q000502:physiology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D019255:NADPH Oxidases