Molecular Characterization of Mutants of the Acetate Regulatory GenefacBofAspergillus nidulans

Todd, Richard B.; Kelly, Joseph F.; Davis, Meryl A.; Hynes, Michael J.

doi:10.1006/fgbi.1997.1007

Cited by 29 publications

(24 citation statements)

References 66 publications

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“…Later screens conducted by Armitt et al (1976) and Owen et al (1992) increased this total to 14 complementation groups plus single mutants. The identification of the facB gene as an acetate-responsive transcription factor demonstrated that acetate is actively sensed in some types of eukaryotic organisms (Katz and Hynes 1989;Todd et al 1997b). Although a number of Arabidopsis proteins show moderate sequence similarity ($ 25% identity) to the C-terminal transcriptional activation domain of FacB, there is no significant similarity over the entire primary sequence that would indicate the presence of a FacB homologue in Arabidopsis.…”

Section: Discussionmentioning

confidence: 97%

Acetate non-utilizing mutants of Arabidopsis: evidence that organic acids influence carbohydrate perception in germinating seedlings

et al. 2004

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A phenotypic screen was employed to isolate Arabidopsis plants that are deficient in their ability to utilize or sense acetate. The screening strategy, based on resistance to the toxic acetate analogue monofluoroacetic acid, was adapted from one that has been used successfully to identify important metabolic and regulatory genes involved in acetate metabolism in fungi. Following conventions established from the fungal work, the mutants were called acn mutants for acetate non-utilization. Three highly resistant plant lines were the focus of genetic and physiological studies. Mutant acn1 appears to be a true acetate non-utilizing mutant, as it displays increased sensitivity to exogenous acetate. The progeny of the original acn2 mutant did not germinate, even in the presence of sucrose as an exogenous carbon source. The germination of seeds from the F3 generation depended on the sucrose concentration in the medium. Only a small proportion of seeds germinated in the absence of exogenous sucrose and in the presence of 100 mM sucrose, but up to 70% of seeds germinated on 20 mM sucrose. Mutant acn3 exhibited sensitivity to exogenous sucrose, showing significant chlorosis on medium containing 20 mM sucrose, but no chlorosis when grown in the absence of exogenous sucrose. This phenotype was alleviated if acetate was provided. The acn mutants demonstrate that disrupting organic acid utilization can have profound affects on carbohydrate metabolism.

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Section: Discussionmentioning

confidence: 97%

Acetate non-utilizing mutants of Arabidopsis: evidence that organic acids influence carbohydrate perception in germinating seedlings

et al. 2004

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“…No afp::uidA expression was observed during cultivation on acetate and acetamide, although A. giganteus is able to utilize both nutrients for growth at rates comparable to that on glucose. Many fungi can metabolize acetate and acetamide as sole carbon sources via the glyoxylate bypass of the tricarboxylic acid cycle (Todd et al 1997). …”

Section: Discussionmentioning

confidence: 99%

Transcriptional regulation of the Antifungal Protein in Aspergillus giganteus

2002

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Regulation of the expression of the afp gene that codes for the Antifungal Protein of Aspergillus giganteus was investigated using a reporter system. For this purpose, the E. coli reporter gene uidA encoding beta-glucuronidase (GUS) was placed under the control of the afp promoter. No homologous integration of the reporter construct into the afp site was observed among 156 transformants tested. In one of the transformants carrying a single, ectopically integrated, copy of the construct, GUS and AFP both displayed exactly the same temporal expression patterns under various cultivation conditions, as assayed by Northern and protein analyses. Thus, this transformant was used to identify factors that are involved in the transcriptional regulation of afp expression. Expression is only detectable in the vegetative mycelium, whereas no expression occurs in aerial hyphae or conidia, indicating that afp expression is developmentally regulated. Transcription of afp is regulated by ambient pH, being suppressed under acidic conditions and strongly induced under alkaline conditions. This observation suggests that PacC regulates the afp gene, which is consistent with the presence of two putative PacC binding sites within the 5' upstream region. Transcription is not subject to carbon catabolite repression or nitrogen metabolite repression. The expression of afp is up-regulated by heat shock, upon growth in the presence of excess NaCl and ethanol, and under conditions of carbon starvation. In contrast, expression decreases slightly in the presence of hydrogen peroxide and under nitrogen starvation. These data are compatible with the presence of a putative heat shock element (NTTCNNGANTTCN) and five putative C(4)T stress-responsive elements within the afp promoter.

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“…These genes are induced by acetate via the FacB activator, which is related to the Cat8 and Sip4 proteins of S. cerevisiae (10,31,61,67,74,76,77). Mutations in acuD and acuE, which encode the glyoxalate bypass enzymes isocitrate lyase and malate synthase, respectively, are also unable to use acetate, but in addition are unable to use fatty acids as sole carbon sources (2,3,21,36,61).…”

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confidence: 99%

Regulatory Genes Controlling Fatty Acid Catabolism and Peroxisomal Functions in the Filamentous Fungus Aspergillus nidulans

et al. 2006

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The catabolism of fatty acids is important in the lifestyle of many fungi, including plant and animal pathogens. This has been investigated in Aspergillus nidulans, which can grow on acetate and fatty acids as sources of carbon, resulting in the production of acetyl coenzyme A (CoA). Acetyl-CoA is metabolized via the glyoxalate bypass, located in peroxisomes, enabling gluconeogenesis. Acetate induction of enzymes specific for acetate utilization as well as glyoxalate bypass enzymes is via the Zn 2 -Cys 6 binuclear cluster activator FacB. However, enzymes of the glyoxalate bypass as well as fatty acid beta-oxidation and peroxisomal proteins are also inducible by fatty acids. We have isolated mutants that cannot grow on fatty acids. Two of the corresponding genes, farA and farB, encode two highly conserved families of related Zn 2 -Cys 6 binuclear proteins present in filamentous ascomycetes, including plant pathogens. A single ortholog is found in the yeasts Candida albicans, Debaryomyces hansenii, and Yarrowia lipolytica, but not in the Ashbya, Kluyveromyces, Saccharomyces lineage. Northern blot analysis has shown that deletion of the farA gene eliminates induction of a number of genes by both short-and long-chain fatty acids, while deletion of the farB gene eliminates short-chain induction. An identical core 6-bp in vitro binding site for each protein has been identified in genes encoding glyoxalate bypass, beta-oxidation, and peroxisomal functions. This sequence is overrepresented in the 5 region of genes predicted to be fatty acid induced in other filamentous ascomycetes, C. albicans, D. hansenii, and Y. lipolytica, but not in the corresponding genes in Saccharomyces cerevisiae.It has become increasingly clear that the breakdown of fatty acids is important in the metabolism, development, and pathogenicity of many fungi. Catabolism occurs via the beta-oxidation pathway, in which fatty acids are activated to the corresponding acyl coenzyme A (CoA) and then oxidation by a series of enzyme steps releases acetyl-CoA and an acyl-CoA shortened by two carbons, which can undergo additional cycles of beta-oxidation. In mammals, beta-oxidation of long-chain fatty acids occurs in peroxisomes, while medium-and shortchain fatty acids undergo beta-oxidation in the mitochondria (reviewed in references 16 and 84). In contrast, in Saccharomyces cerevisiae fatty acids are metabolized entirely in peroxisomes (reviewed in reference 29). In fungi, where fatty acids can serve as sole sources of carbon and energy, the acetyl-CoA must be converted to C 4 compounds via the glyoxalate bypass, comprising the enzymes isocitrate lyase and malate synthase, allowing gluconeogenesis (40, 64). Isocitrate lyase and malate synthase are usually, but not always, located in peroxisomes. It has been found that mutations affecting isocitrate lyase, malate synthase, and peroxisomal functions can affect the pathogenicity of both plant and animal pathogens (33,37,45,46,66). Furthermore it has been found that genes encoding enzymes for fatty acid catabol...

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Molecular Characterization of Mutants of the Acetate Regulatory GenefacBofAspergillus nidulans

Cited by 29 publications

References 66 publications

Acetate non-utilizing mutants of Arabidopsis: evidence that organic acids influence carbohydrate perception in germinating seedlings

Acetate non-utilizing mutants of Arabidopsis: evidence that organic acids influence carbohydrate perception in germinating seedlings

Transcriptional regulation of the Antifungal Protein in Aspergillus giganteus

Regulatory Genes Controlling Fatty Acid Catabolism and Peroxisomal Functions in the Filamentous Fungus Aspergillus nidulans

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