Redox Imbalance at the Start of Each Morphogenetic Step of Neurospora crassa Conidiation

Toledo, Ivonne; Rangel, Pablo; Hansberg, Wilhelm

doi:10.1006/abbi.1995.1326

Cited by 49 publications

(36 citation statements)

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“…gfp or cpeA were used as probes as indicated. Another attractive possibility for a role of catalase-peroxidase during development comes from the observation that in N. crassa a hyperoxidant state was detected at the start of different morphogenic transitions (12,29). Therefore, CpeA could have an important function in coping with this dangerous state.…”

Section: Discussionmentioning

confidence: 99%

Aspergillus nidulansCatalase-Peroxidase Gene (cpeA) Is Transcriptionally Induced during Sexual Development through the Transcription Factor StuA

et al. 2002

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Catalases, peroxidases, and catalase-peroxidases are important enzymes to cope with reactive oxygen species in pro-and eukaryotic cells. In the filamentous fungus Aspergillus nidulans three monofunctional catalases have been described, and a fourth catalase activity was observed in native polyacrylamide gels. The latter activity is probably due to the bifunctional enzyme catalase-peroxidase, which we characterized here. The gene, named cpeA, encodes an 81-kDa polypeptide with a conserved motif for heme coordination. The enzyme comprises of two similar domains, suggesting gene duplication and fusion during evolution. The first 439 amino acids share 22% identical residues with the C terminus. Homologous proteins are found in several prokaryotes, such as Escherichia coli and Mycobacterium tuberculosis (both with 61% identity). In fungi the enzyme has been noted in Penicillium simplicissimum, Septoria tritici, and Neurospora crassa (69% identical amino acids) but is absent from Saccharomyces cerevisiae. Expression analysis in A. nidulans revealed that the gene is transcriptionally induced upon carbon starvation and during sexual development, but starvation is not sufficient to reach high levels of the transcript during development. Besides transcriptional activation, we present evidence for posttranscriptional regulation. A green fluorescent protein fusion protein localized to the cytoplasm of Hülle cells. The Hülle cell-specific expression was dependent on the developmental regulator StuA, suggesting an activating function of this helix-loop-helix transcription factor.

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Section: Discussionmentioning

confidence: 99%

Aspergillus nidulansCatalase-Peroxidase Gene (cpeA) Is Transcriptionally Induced during Sexual Development through the Transcription Factor StuA

et al. 2002

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“…These difficulties are multiplied when modifications within living cells are considered. Even in the most carefully studied systems [52,[174][175][176][177], one can only rigorously conclude that a wide range of oxidative modifications are concomitant with elevated proteolytic removal. Similar observations have been made with isolated mitochondria and choloroplasts, so that the idea probably has generality.…”

Section: Enzymic Removal Of Oxidized Proteinsmentioning

confidence: 99%

“…Conidiation comprises successively the germination of the conidium (an asexual spore) to generate filamentous hyphae by apical growth ; later, aerial hyphae develop, and ultimately conidia form at their tips. There are thus three transitions, and each involves a ' hyperoxidant ' state, as judged by chemiluminescence, alteration of GSH\GSSG and NAD(P)H\NAD(P) + ratios and excretion of GSSG [175,177,[204][205][206]. Protein oxidation (measured by carbonyl groups) is kinetically and spatially correlated with these events.…”

Section: Oxidized Proteins In the Control Of Cell Growth And Differenmentioning

confidence: 99%

Biochemistry and pathology of radical-mediated protein oxidation

Dean

Stocker

et al. 1997

Biochemical Journal

1,549

982

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Radical-mediated damage to proteins may be initiated by electron leakage, metal-ion-dependent reactions and autoxidation of lipids and sugars. The consequent protein oxidation is O2-dependent, and involves several propagating radicals, notably alkoxyl radicals. Its products include several categories of reactive species, and a range of stable products whose chemistry is currently being elucidated. Among the reactive products, protein hydroperoxides can generate further radical fluxes on reaction with transition-metal ions; protein-bound reductants (notably dopa) can reduce transition-metal ions and thereby facilitate their reaction with hydroperoxides; and aldehydes may participate in Schiff-base formation and other reactions. Cells can detoxify some of the reactive species, e.g. by reducing protein hydroperoxides to unreactive hydroxides. Oxidized proteins are often functionally inactive and their unfolding is associated with enhanced susceptibility to proteinases. Thus cells can generally remove oxidized proteins by proteolysis. However, certain oxidized proteins are poorly handled by cells, and together with possible alterations in the rate of production of oxidized proteins, this may contribute to the observed accumulation and damaging actions of oxidized proteins during aging and in pathologies such as diabetes, atherosclerosis and neurodegenerative diseases. Protein oxidation may also sometimes play controlling roles in cellular remodelling and cell growth. Proteins are also key targets in defensive cytolysis and in inflammatory self-damage. The possibility of selective protection against protein oxidation (antioxidation) is raised.

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“…A hyperoxidant state develops at the start of these morphogenetic transitions (14,(39)(40)(41)(42) and during germination of conidia (26). A hyperoxidant state is defined as an unstable, transient state in which reactive oxygen species surpass the antioxidant capacity of the cell (13,15).…”

mentioning

confidence: 99%

“…The occurrence of a hyperoxidant state is indicated by oxidation of total protein that occurs at the start of the aforementioned morphogenetic transitions (39,41). Glutamine synthetase and glutamate dehydrogenase oxidation occurs during adhesion of hyphae, formation of aerial hyphae, and return to the growth state (41,42). Catalase is modified during conidiation (15) and in vitro because of the reaction of singlet oxygen ( 1 O 2 ) with its heme (25).…”

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confidence: 99%

Asexual Development Is Increased in Neurospora crassa cat - 3 -Null Mutant Strains

2003

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We use asexual development of Neurospora crassa as a model system with which to determine the causes of cell differentiation. Air exposure of a mycelial mat induces hyphal adhesion, and adherent hyphae grow aerial hyphae that, in turn, form conidia. Previous work indicated the development of a hyperoxidant state at the start of these morphogenetic transitions and a large increase in catalase activity during conidiation. Catalase 3 (CAT-3) increases at the end of exponential growth and is induced by different stress conditions. Here we analyzed the effects of cat-3-null strains on growth and asexual development. The lack of CAT-3 was not compensated by other catalases, even under oxidative stress conditions, and cat-3 RIP colonies were sensitive to H 2 O 2 , indicating that wild-type (Wt) resistance to external H 2 O 2 was due to CAT-3. cat-3 RIP colonies grown in the dark produced high levels of carotenes as a consequence of oxidative stress. Light exacerbated oxidative stress and further increased carotene synthesis. In the cat-3 RIP mutant strain, increased aeration in liquid cultures led to increased hyphal adhesion and protein oxidation. Compared to the Wt, the cat-3 RIP mutant strain produced six times more aerial hyphae and conidia in air-exposed mycelial mats, as a result of longer and more densely packed aerial hyphae. Protein oxidation in colonies was threefold higher and showed more aerial hyphae and conidia in mutant strains than did the Wt. Results indicate that oxidative stress due to lack of CAT-3 induces carotene synthesis, hyphal adhesion, and more aerial hyphae and conidia.

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Redox Imbalance at the Start of Each Morphogenetic Step of Neurospora crassa Conidiation

Cited by 49 publications

References 0 publications

Aspergillus nidulansCatalase-Peroxidase Gene (cpeA) Is Transcriptionally Induced during Sexual Development through the Transcription Factor StuA

Aspergillus nidulansCatalase-Peroxidase Gene (cpeA) Is Transcriptionally Induced during Sexual Development through the Transcription Factor StuA

Biochemistry and pathology of radical-mediated protein oxidation

Asexual Development Is Increased in Neurospora crassa cat - 3 -Null Mutant Strains

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