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Signaling governed by G proteins and cAMP is crucial for growth, secondary metabolism and sexual development in Fusarium fujikuroi.

Studt L, Humpf HU, Tudzynski B - PLoS ONE (2013)

Bottom Line: Here we studied the impact of the heterotrimeric G protein and the cAMP-mediated signaling network, including the regulatory subunits of the cAMP-dependent protein kinase (PKA), to study their effect on colony morphology, sexual development and regulation of bikaverins, fusarubins and GAs.In contrast, bikaverin biosynthesis is significantly reduced in ffg1 and ffg3 deletion mutants and positively regulated by FfAC and FfPKA1, while GA biosynthesis depends on the active FfAC and FfPKA2 in an FfG1- and FfG3-independent manner.In addition, we provide evidence that G Protein-mediated/cAMP signaling is important for growth in F. fujikuroi because deletion of ffg3, ffac and ffpka1 resulted in impaired growth on minimal and rich media.

View Article: PubMed Central - PubMed

Affiliation: Institut für Lebensmittelchemie, Westfälische Wilhelms-Universität, Münster, Germany.

ABSTRACT
The plant-pathogenic fungus Fusarium fujikuroi is a notorious rice pathogen causing hyper-elongation of infected plants due to the production of gibberellic acids (GAs). In addition to GAs, F. fujikuroi produces a wide range of other secondary metabolites, such as fusarins, fusaric acid or the red polyketides bikaverins and fusarubins. The recent availability of the fungal genome sequence for this species has revealed the potential of many more putative secondary metabolite gene clusters whose products remain to be identified. However, the complex regulation of secondary metabolism is far from being understood. Here we studied the impact of the heterotrimeric G protein and the cAMP-mediated signaling network, including the regulatory subunits of the cAMP-dependent protein kinase (PKA), to study their effect on colony morphology, sexual development and regulation of bikaverins, fusarubins and GAs. We demonstrated that fusarubin biosynthesis is negatively regulated by at least two Gα subunits, FfG1 and FfG3, which both function as stimulators of the adenylyl cyclase FfAC. Surprisingly, the primary downstream target of the adenylyl cyclase, the PKA, is not involved in the regulation of fusarubins, suggesting that additional, yet unidentified, cAMP-binding protein(s) exist. In contrast, bikaverin biosynthesis is significantly reduced in ffg1 and ffg3 deletion mutants and positively regulated by FfAC and FfPKA1, while GA biosynthesis depends on the active FfAC and FfPKA2 in an FfG1- and FfG3-independent manner. In addition, we provide evidence that G Protein-mediated/cAMP signaling is important for growth in F. fujikuroi because deletion of ffg3, ffac and ffpka1 resulted in impaired growth on minimal and rich media. Finally, sexual crosses of ffg1 mutants showed the importance of a functional FfG1 protein for development of perithecia in the mating strain that carries the MAT1-1 idiomorph.

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Involvement of G protein-mediated/cAMP signaling in the regulation of secondary metabolism in F. fujikuroi.Involvement of G protein-mediated/cAMP signaling in the regulation of secondary metabolism in F. fujikuroi. In the inactive state one GDP-bound Gα subunit (either one of FfG1, FfG2 and FfG3) is tightly associated with the Gβγ subunit forming a heterotrimeric G protein that is associated with a seven transmembrane helices-containing GPCR. In addition the Gα and Gγ subunits further anchor the heterotrimeric G protein to the plasma membrane through a N-terminal and a C-terminal acyl group, respectively. Ligand-binding to the GPCR leads to the exchange of GDP for GTP, resulting in a conformational change of the Gβγ-binding site and the dissociation of the Gα subunit from the Gβγ dimer. Each component (FfG1, FfG2, FfG3 or Gβγ) may now stimulate the downstream target, FfAC. FfAC in turn produces cAMP from ATP and activates the PKA. FfPKA1 then activates bikaverin biosynthesis, while FfPKA2 activates GA biosynthesis. Neither FfG1 nor FfG3 are involved in the regulation of GA biosynthesis. Whether FfG2, the monomeric G protein FfRAS or the CO2 level regulates GA biosynthesis via stimulation of cAMP accumulation awaits proof. Besides the PKA another cAMP-binding protein is most likely involved in the repression of fusarubin biosynthesis.
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pone-0058185-g008: Involvement of G protein-mediated/cAMP signaling in the regulation of secondary metabolism in F. fujikuroi.Involvement of G protein-mediated/cAMP signaling in the regulation of secondary metabolism in F. fujikuroi. In the inactive state one GDP-bound Gα subunit (either one of FfG1, FfG2 and FfG3) is tightly associated with the Gβγ subunit forming a heterotrimeric G protein that is associated with a seven transmembrane helices-containing GPCR. In addition the Gα and Gγ subunits further anchor the heterotrimeric G protein to the plasma membrane through a N-terminal and a C-terminal acyl group, respectively. Ligand-binding to the GPCR leads to the exchange of GDP for GTP, resulting in a conformational change of the Gβγ-binding site and the dissociation of the Gα subunit from the Gβγ dimer. Each component (FfG1, FfG2, FfG3 or Gβγ) may now stimulate the downstream target, FfAC. FfAC in turn produces cAMP from ATP and activates the PKA. FfPKA1 then activates bikaverin biosynthesis, while FfPKA2 activates GA biosynthesis. Neither FfG1 nor FfG3 are involved in the regulation of GA biosynthesis. Whether FfG2, the monomeric G protein FfRAS or the CO2 level regulates GA biosynthesis via stimulation of cAMP accumulation awaits proof. Besides the PKA another cAMP-binding protein is most likely involved in the repression of fusarubin biosynthesis.

Mentions: In conclusion, our studies describe the complex and diverse involvement of G protein/cAMP-mediated signaling in the regulation of fungal growth, secondary metabolism and sexual development in F. fujikuroi. We demonstrate that FfG1 (class I), FfG3 (class III) and FfAC negatively regulate the biosynthesis of fusarubin, probably by additive stimulating effects of FfAC by both Gα subunits. Surprisingly, neither FfPKA1 nor FfPKA2 have any impact on fusarubin production, indicating that another yet unidentified cAMP-binding protein exists that is involved in the regulation of the perithecial pigment. On the other hand, bikaverin production is regulated in an opposite way: its production is inhibited in the ffg1, ffg3 and ffac deletion mutants. The opposite regulation of the two red pigments is also underlined by the contrasting effect of the global regulator Velvet: deletion of ffvel1 resulted not only in increased bikaverin biosynthesis under both inducing and repressing conditions, but also in complete inhibition of fusarubin formation (fig. 8).


Signaling governed by G proteins and cAMP is crucial for growth, secondary metabolism and sexual development in Fusarium fujikuroi.

Studt L, Humpf HU, Tudzynski B - PLoS ONE (2013)

Involvement of G protein-mediated/cAMP signaling in the regulation of secondary metabolism in F. fujikuroi.Involvement of G protein-mediated/cAMP signaling in the regulation of secondary metabolism in F. fujikuroi. In the inactive state one GDP-bound Gα subunit (either one of FfG1, FfG2 and FfG3) is tightly associated with the Gβγ subunit forming a heterotrimeric G protein that is associated with a seven transmembrane helices-containing GPCR. In addition the Gα and Gγ subunits further anchor the heterotrimeric G protein to the plasma membrane through a N-terminal and a C-terminal acyl group, respectively. Ligand-binding to the GPCR leads to the exchange of GDP for GTP, resulting in a conformational change of the Gβγ-binding site and the dissociation of the Gα subunit from the Gβγ dimer. Each component (FfG1, FfG2, FfG3 or Gβγ) may now stimulate the downstream target, FfAC. FfAC in turn produces cAMP from ATP and activates the PKA. FfPKA1 then activates bikaverin biosynthesis, while FfPKA2 activates GA biosynthesis. Neither FfG1 nor FfG3 are involved in the regulation of GA biosynthesis. Whether FfG2, the monomeric G protein FfRAS or the CO2 level regulates GA biosynthesis via stimulation of cAMP accumulation awaits proof. Besides the PKA another cAMP-binding protein is most likely involved in the repression of fusarubin biosynthesis.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585259&req=5

pone-0058185-g008: Involvement of G protein-mediated/cAMP signaling in the regulation of secondary metabolism in F. fujikuroi.Involvement of G protein-mediated/cAMP signaling in the regulation of secondary metabolism in F. fujikuroi. In the inactive state one GDP-bound Gα subunit (either one of FfG1, FfG2 and FfG3) is tightly associated with the Gβγ subunit forming a heterotrimeric G protein that is associated with a seven transmembrane helices-containing GPCR. In addition the Gα and Gγ subunits further anchor the heterotrimeric G protein to the plasma membrane through a N-terminal and a C-terminal acyl group, respectively. Ligand-binding to the GPCR leads to the exchange of GDP for GTP, resulting in a conformational change of the Gβγ-binding site and the dissociation of the Gα subunit from the Gβγ dimer. Each component (FfG1, FfG2, FfG3 or Gβγ) may now stimulate the downstream target, FfAC. FfAC in turn produces cAMP from ATP and activates the PKA. FfPKA1 then activates bikaverin biosynthesis, while FfPKA2 activates GA biosynthesis. Neither FfG1 nor FfG3 are involved in the regulation of GA biosynthesis. Whether FfG2, the monomeric G protein FfRAS or the CO2 level regulates GA biosynthesis via stimulation of cAMP accumulation awaits proof. Besides the PKA another cAMP-binding protein is most likely involved in the repression of fusarubin biosynthesis.
Mentions: In conclusion, our studies describe the complex and diverse involvement of G protein/cAMP-mediated signaling in the regulation of fungal growth, secondary metabolism and sexual development in F. fujikuroi. We demonstrate that FfG1 (class I), FfG3 (class III) and FfAC negatively regulate the biosynthesis of fusarubin, probably by additive stimulating effects of FfAC by both Gα subunits. Surprisingly, neither FfPKA1 nor FfPKA2 have any impact on fusarubin production, indicating that another yet unidentified cAMP-binding protein exists that is involved in the regulation of the perithecial pigment. On the other hand, bikaverin production is regulated in an opposite way: its production is inhibited in the ffg1, ffg3 and ffac deletion mutants. The opposite regulation of the two red pigments is also underlined by the contrasting effect of the global regulator Velvet: deletion of ffvel1 resulted not only in increased bikaverin biosynthesis under both inducing and repressing conditions, but also in complete inhibition of fusarubin formation (fig. 8).

Bottom Line: Here we studied the impact of the heterotrimeric G protein and the cAMP-mediated signaling network, including the regulatory subunits of the cAMP-dependent protein kinase (PKA), to study their effect on colony morphology, sexual development and regulation of bikaverins, fusarubins and GAs.In contrast, bikaverin biosynthesis is significantly reduced in ffg1 and ffg3 deletion mutants and positively regulated by FfAC and FfPKA1, while GA biosynthesis depends on the active FfAC and FfPKA2 in an FfG1- and FfG3-independent manner.In addition, we provide evidence that G Protein-mediated/cAMP signaling is important for growth in F. fujikuroi because deletion of ffg3, ffac and ffpka1 resulted in impaired growth on minimal and rich media.

View Article: PubMed Central - PubMed

Affiliation: Institut für Lebensmittelchemie, Westfälische Wilhelms-Universität, Münster, Germany.

ABSTRACT
The plant-pathogenic fungus Fusarium fujikuroi is a notorious rice pathogen causing hyper-elongation of infected plants due to the production of gibberellic acids (GAs). In addition to GAs, F. fujikuroi produces a wide range of other secondary metabolites, such as fusarins, fusaric acid or the red polyketides bikaverins and fusarubins. The recent availability of the fungal genome sequence for this species has revealed the potential of many more putative secondary metabolite gene clusters whose products remain to be identified. However, the complex regulation of secondary metabolism is far from being understood. Here we studied the impact of the heterotrimeric G protein and the cAMP-mediated signaling network, including the regulatory subunits of the cAMP-dependent protein kinase (PKA), to study their effect on colony morphology, sexual development and regulation of bikaverins, fusarubins and GAs. We demonstrated that fusarubin biosynthesis is negatively regulated by at least two Gα subunits, FfG1 and FfG3, which both function as stimulators of the adenylyl cyclase FfAC. Surprisingly, the primary downstream target of the adenylyl cyclase, the PKA, is not involved in the regulation of fusarubins, suggesting that additional, yet unidentified, cAMP-binding protein(s) exist. In contrast, bikaverin biosynthesis is significantly reduced in ffg1 and ffg3 deletion mutants and positively regulated by FfAC and FfPKA1, while GA biosynthesis depends on the active FfAC and FfPKA2 in an FfG1- and FfG3-independent manner. In addition, we provide evidence that G Protein-mediated/cAMP signaling is important for growth in F. fujikuroi because deletion of ffg3, ffac and ffpka1 resulted in impaired growth on minimal and rich media. Finally, sexual crosses of ffg1 mutants showed the importance of a functional FfG1 protein for development of perithecia in the mating strain that carries the MAT1-1 idiomorph.

Show MeSH
Related in: MedlinePlus