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Aspergillus oxylipin signaling and quorum sensing pathways depend on g protein-coupled receptors.

Affeldt KJ, Brodhagen M, Keller NP - Toxins (Basel) (2012)

Bottom Line: Here, we present evidence that oxylipins stimulate a burst in cAMP in A. nidulans, and that loss of an A. nidulans GPCR, gprD, prevents this cAMP accumulation.A. flavus undergoes an oxylipin-mediated developmental shift when grown at different densities, and this regulates spore, sclerotial and aflatoxin production.The finding of GPCRs that regulate production of survival structures (sclerotia), inoculum (spores) and aflatoxin holds promise for future development of anti-fungal therapeutics.

View Article: PubMed Central - PubMed

Affiliation: Department of Bacteriology and Department of Medical Microbiology and Immunology, 1550 Linden Drive, Madison, WI 53706, USA.

ABSTRACT
Oxylipins regulate Aspergillus development and mycotoxin production and are also involved in Aspergillus quorum sensing mechanisms. Despite extensive knowledge of how these oxylipins are synthesized and what processes they regulate, nothing is known about how these signals are detected and transmitted by the fungus. G protein-coupled receptors (GPCR) have been speculated to be involved as they are known oxylipin receptors in mammals, and many putative GPCRs have been identified in the Aspergilli. Here, we present evidence that oxylipins stimulate a burst in cAMP in A. nidulans, and that loss of an A. nidulans GPCR, gprD, prevents this cAMP accumulation. A. flavus undergoes an oxylipin-mediated developmental shift when grown at different densities, and this regulates spore, sclerotial and aflatoxin production. A. flavus encodes two putative GprD homologs, GprC and GprD, and we demonstrate here that they are required to transition to a high-density development state, as well as to respond to spent medium of a high-density culture. The finding of GPCRs that regulate production of survival structures (sclerotia), inoculum (spores) and aflatoxin holds promise for future development of anti-fungal therapeutics.

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(a) A. nidulans wild type and ∆gprA were treated with EtOH (control) or 10 μM oxylipin in EtOH, tissues were harvested, and cAMP concentrations were measured; (b) A. nidulans wild type and ∆gprD were treated with EtOH (control) or 10 μM oxylipin in EtOH, tissues were harvested, and cAMP concentrations were measured; (c) A. nidulans wild type and ∆gprG were treated with EtOH (control) or 10 μM oxylipin in EtOH, tissues were harvested, and cAMP concentrations were measured. Differences from the EtOH control in (a), (b), and (c) are denoted as follows: *p < 0.05; **p < 0.01, determined by one-tailed paired Student’s T-tests.
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toxins-04-00695-f002: (a) A. nidulans wild type and ∆gprA were treated with EtOH (control) or 10 μM oxylipin in EtOH, tissues were harvested, and cAMP concentrations were measured; (b) A. nidulans wild type and ∆gprD were treated with EtOH (control) or 10 μM oxylipin in EtOH, tissues were harvested, and cAMP concentrations were measured; (c) A. nidulans wild type and ∆gprG were treated with EtOH (control) or 10 μM oxylipin in EtOH, tissues were harvested, and cAMP concentrations were measured. Differences from the EtOH control in (a), (b), and (c) are denoted as follows: *p < 0.05; **p < 0.01, determined by one-tailed paired Student’s T-tests.

Mentions: To better assess the possibility that GprA or GprD might be involved in oxylipin perception, A. nidulans ∆gprA and ∆gprD strains, as well as ∆gprG, a randomly chosen GPCR deletion mutant exhibiting the wild type conidiation response to linoleic acid, were then assessed for their cAMP response to four pure oxylipins: 13(S)-HpODE, 9(S)-HpODE, 13(S)-HODE and 9(S)-HODE. As shown in Figure 2, both ∆gprA and ∆gprG produced significantly more cAMP when exposed to each of the four oxylipins than when treated with an equivalent volume of EtOH (all p < 0.05). In contrast, the ∆gprD mutant did not respond to any of the four oxylipins with an increase in cAMP concentrations over that of the EtOH control (all p > 0.1).


Aspergillus oxylipin signaling and quorum sensing pathways depend on g protein-coupled receptors.

Affeldt KJ, Brodhagen M, Keller NP - Toxins (Basel) (2012)

(a) A. nidulans wild type and ∆gprA were treated with EtOH (control) or 10 μM oxylipin in EtOH, tissues were harvested, and cAMP concentrations were measured; (b) A. nidulans wild type and ∆gprD were treated with EtOH (control) or 10 μM oxylipin in EtOH, tissues were harvested, and cAMP concentrations were measured; (c) A. nidulans wild type and ∆gprG were treated with EtOH (control) or 10 μM oxylipin in EtOH, tissues were harvested, and cAMP concentrations were measured. Differences from the EtOH control in (a), (b), and (c) are denoted as follows: *p < 0.05; **p < 0.01, determined by one-tailed paired Student’s T-tests.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3475224&req=5

toxins-04-00695-f002: (a) A. nidulans wild type and ∆gprA were treated with EtOH (control) or 10 μM oxylipin in EtOH, tissues were harvested, and cAMP concentrations were measured; (b) A. nidulans wild type and ∆gprD were treated with EtOH (control) or 10 μM oxylipin in EtOH, tissues were harvested, and cAMP concentrations were measured; (c) A. nidulans wild type and ∆gprG were treated with EtOH (control) or 10 μM oxylipin in EtOH, tissues were harvested, and cAMP concentrations were measured. Differences from the EtOH control in (a), (b), and (c) are denoted as follows: *p < 0.05; **p < 0.01, determined by one-tailed paired Student’s T-tests.
Mentions: To better assess the possibility that GprA or GprD might be involved in oxylipin perception, A. nidulans ∆gprA and ∆gprD strains, as well as ∆gprG, a randomly chosen GPCR deletion mutant exhibiting the wild type conidiation response to linoleic acid, were then assessed for their cAMP response to four pure oxylipins: 13(S)-HpODE, 9(S)-HpODE, 13(S)-HODE and 9(S)-HODE. As shown in Figure 2, both ∆gprA and ∆gprG produced significantly more cAMP when exposed to each of the four oxylipins than when treated with an equivalent volume of EtOH (all p < 0.05). In contrast, the ∆gprD mutant did not respond to any of the four oxylipins with an increase in cAMP concentrations over that of the EtOH control (all p > 0.1).

Bottom Line: Here, we present evidence that oxylipins stimulate a burst in cAMP in A. nidulans, and that loss of an A. nidulans GPCR, gprD, prevents this cAMP accumulation.A. flavus undergoes an oxylipin-mediated developmental shift when grown at different densities, and this regulates spore, sclerotial and aflatoxin production.The finding of GPCRs that regulate production of survival structures (sclerotia), inoculum (spores) and aflatoxin holds promise for future development of anti-fungal therapeutics.

View Article: PubMed Central - PubMed

Affiliation: Department of Bacteriology and Department of Medical Microbiology and Immunology, 1550 Linden Drive, Madison, WI 53706, USA.

ABSTRACT
Oxylipins regulate Aspergillus development and mycotoxin production and are also involved in Aspergillus quorum sensing mechanisms. Despite extensive knowledge of how these oxylipins are synthesized and what processes they regulate, nothing is known about how these signals are detected and transmitted by the fungus. G protein-coupled receptors (GPCR) have been speculated to be involved as they are known oxylipin receptors in mammals, and many putative GPCRs have been identified in the Aspergilli. Here, we present evidence that oxylipins stimulate a burst in cAMP in A. nidulans, and that loss of an A. nidulans GPCR, gprD, prevents this cAMP accumulation. A. flavus undergoes an oxylipin-mediated developmental shift when grown at different densities, and this regulates spore, sclerotial and aflatoxin production. A. flavus encodes two putative GprD homologs, GprC and GprD, and we demonstrate here that they are required to transition to a high-density development state, as well as to respond to spent medium of a high-density culture. The finding of GPCRs that regulate production of survival structures (sclerotia), inoculum (spores) and aflatoxin holds promise for future development of anti-fungal therapeutics.

Show MeSH
Related in: MedlinePlus