Riboflavin, overproduced during sporulation of <i>Ashbya gossypii</i>, protects its hyaline spores against ultraviolet light

Stahmann, K.‐Peter; Arst, Herbert N.; Althöfer, Henning; Revuelta, José Luis; Monschau, Nicole; Schlüpen, Christina; Gätgens, Cornelia; Wiesenburg, Andreas; Schlösser, Thomas

doi:10.1046/j.1462-2920.2001.00225.x

Cited by 54 publications

(44 citation statements)

References 26 publications

(39 reference statements)

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“…RF oversynthesis by both of the above-mentioned fungi occurs after vegetative growth has ceased, during mycelium lysis and spore formation (209,463). As a rule, similar kinetics of production have been seen during microbial synthesis of secondary metabolites, e.g., antibiotics, but not primary metabolites.…”

Section: Transcriptional Regulation In Mycelial Fungimentioning

confidence: 86%

“…Therefore, RF overproduction by the mycelial fungi E. ashbyii and A. gossypii has been called "pseudosecondary biosynthesis" (66). The physiological reasons for RF overproduc- (463). That fungi can produce pigments to attract insects for spore spreading is well known (3), but one cannot exclude the possibility that RF overproduced during sporulation by E. ashbyii and A. gossypii attracts insects spreading their spores to new plants (438).…”

Section: Transcriptional Regulation In Mycelial Fungimentioning

confidence: 99%

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Genetic Control of Biosynthesis and Transport of Riboflavin and Flavin Nucleotides and Construction of Robust Biotechnological Producers

Abbas

Sibirny

2011

Microbiol Mol Biol Rev

316

272

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SUMMARY Riboflavin [7,8-dimethyl-10-(1′- d -ribityl)isoalloxazine, vitamin B 2 ] is an obligatory component of human and animal diets, as it serves as the precursor of flavin coenzymes, flavin mononucleotide, and flavin adenine dinucleotide, which are involved in oxidative metabolism and other processes. Commercially produced riboflavin is used in agriculture, medicine, and the food industry. Riboflavin synthesis starts from GTP and ribulose-5-phosphate and proceeds through pyrimidine and pteridine intermediates. Flavin nucleotides are synthesized in two consecutive reactions from riboflavin. Some microorganisms and all animal cells are capable of riboflavin uptake, whereas many microorganisms have distinct systems for riboflavin excretion to the medium. Regulation of riboflavin synthesis in bacteria occurs by repression at the transcriptional level by flavin mononucleotide, which binds to nascent noncoding mRNA and blocks further transcription (named the riboswitch). In flavinogenic molds, riboflavin overproduction starts at the stationary phase and is accompanied by derepression of enzymes involved in riboflavin synthesis, sporulation, and mycelial lysis. In flavinogenic yeasts, transcriptional repression of riboflavin synthesis is exerted by iron ions and not by flavins. The putative transcription factor encoded by SEF1 is somehow involved in this regulation. Most commercial riboflavin is currently produced or was produced earlier by microbial synthesis using special selected strains of Bacillus subtilis , Ashbya gossypii , and Candida famata . Whereas earlier RF overproducers were isolated by classical selection, current producers of riboflavin and flavin nucleotides have been developed using modern approaches of metabolic engineering that involve overexpression of structural and regulatory genes of the RF biosynthetic pathway as well as genes involved in the overproduction of the purine precursor of riboflavin, GTP.

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Section: Transcriptional Regulation In Mycelial Fungimentioning

confidence: 86%

Section: Transcriptional Regulation In Mycelial Fungimentioning

confidence: 99%

Genetic Control of Biosynthesis and Transport of Riboflavin and Flavin Nucleotides and Construction of Robust Biotechnological Producers

Abbas

Sibirny

2011

Microbiol Mol Biol Rev

316

272

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“…A. gossypii naturally overproduces riboflavin as a detoxifying and protective mechanism (31) and is currently in use for industrial vitamin B 2 production (32). In this work we used A. gossypii to manipulate the purine pathway and eliminate the mechanism of regulation affecting the committed step of the pathway, the synthesis of PRA, which is catalyzed by the enzyme PRPP amidotransferase (10,15,16).…”

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confidence: 99%

Metabolic Engineering of the Purine Pathway for Riboflavin Production in Ashbya gossypii

Jiménez

Santos

Pompejus³

et al. 2005

Appl Environ Microbiol

107

115

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Purine nucleotides are essential precursors for living organisms because they are involved in many important processes, such as nucleic acid synthesis, energy supply, and the biosynthesis of several amino acids and vitamins such as riboflavin. GTP is the immediate precursor for riboflavin biosynthesis, and its formation through the purine pathway is subject to several regulatory mechanisms in different steps. Extracellular purines repress the transcription of most genes required for de novo ATP and GTP synthesis. Additionally, three enzymes of the pathway, phosphoribosyl pyrophosphate (PRPP) amidotransferase, adenylosuccinate synthetase, and IMP dehydrogenase, are subject to feedback inhibition by their end products. Here we report the characterization and manipulation of the committed step in the purine pathway of the riboflavin overproducer Ashbya gossypii. We report that phosphoribosylamine biosynthesis in A. gossypii is negatively regulated at the transcriptional level by extracellular adenine. Furthermore, we show that ATP and GTP exert a strong inhibitory effect on the PRPP amidotransferase from A. gossypii. We constitutively overexpressed the AgADE4 gene encoding PRPP amidotransferase in A. gossypii, thereby abolishing the adenine-mediated transcriptional repression. In addition, we replaced the corresponding residues (aspartic acid 310 , lysine 333 , and alanine 417 ) that have been described to be important for PRPP amidotransferase feedback inhibition in other organisms by site-directed mutagenesis. With these manipulations, we managed to enhance metabolic flow through the purine pathway and to increase the production of riboflavin in the triple mutant strain 10-fold (228 mg/liter).

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“…In A. gossypii, the exogenous addition of cAMP blocks sporulation and riboflavin overproduction (25). We thus added cAMP to a nutrient-limited culture to identify the cAMP-repressed gene set (Fig.…”

Section: Fig 4 Sporulation Ability Of the Tpk1 Tpk2 And Msn2/4 Mutamentioning

confidence: 99%

“…Previously, conserved roles of key S. cerevisiae genes regulating meiosis, e.g., IME1, IME2, IME4, and NDT80, for the sporulation in A. gossypii were identified (24). Similar to bcy1 mutants in yeast, exogenous addition of cAMP to the growth medium promoting constitutive activation of PKA blocks sporulation in A. gossypii (25).…”

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confidence: 98%

Developmental Growth Control Exerted via the Protein A Kinase Tpk2 in Ashbya gossypii

et al. 2015

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Sporulation in Ashbya gossypii is induced by nutrient-limited conditions and leads to the formation of haploid spores. Using RNA-seq, we have determined a gene set induced upon sporulation, which bears considerable overlap with that of Saccharomyces cerevisiae but also contains A. gossypii-specific genes. Addition of cyclic AMP (cAMP) to nutrient-limited media blocks sporulation and represses the induction of sporulation specific genes. Deletion of the protein kinase A (PKA) catalytic subunits encoded by TPK1 and TPK2 showed reduced growth in tpk1 but enhanced growth in the tpk2 strain; however, both mutants sporulated well. Sporulation can be blocked by cAMP in tpk1 but not in tpk2 strains. Similarly, TPK2 acts at a second developmental switch promoting the break in spore dormancy. In S. cerevisiae, PKA phosphorylates and inhibits Msn2/4. The transcript profiles of the tpk1 and msn2/4 mutants were very similar to that of the wild type under sporulation conditions. However, deletion of the single A. gossypii MSN2/4 homolog generated a specific sporulation defect. We identified a set of genes involved in spore wall assembly that was downregulated in the msn2/4 mutant, particularly DIT2, suggesting that poor spore viability may be due to lysis of spores. Our results reveal specific functional differences between the two catalytic PKA subunits in A. gossypii and identified Tpk2 as the key A kinase that transduces developmental decisions of growth. Our data also suggest that Msn2/4 is involved only at a late step of sporulation in A. gossypii and is not a major regulator of IME1.

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Riboflavin, overproduced during sporulation of Ashbya gossypii, protects its hyaline spores against ultraviolet light

Cited by 54 publications

References 26 publications

Genetic Control of Biosynthesis and Transport of Riboflavin and Flavin Nucleotides and Construction of Robust Biotechnological Producers

Genetic Control of Biosynthesis and Transport of Riboflavin and Flavin Nucleotides and Construction of Robust Biotechnological Producers

Metabolic Engineering of the Purine Pathway for Riboflavin Production in Ashbya gossypii

Developmental Growth Control Exerted via the Protein A Kinase Tpk2 in Ashbya gossypii

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