Limits...
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.

Show MeSH

Related in: MedlinePlus

Spores were counted from the area of a plate surrounding a disk soaked with ethanol or linoleic acid in ethanol. The counts from the ethanol control disks were set to one, and the spore totals from the same strain exposed to linoleic acid (dark gray bars) were expressed relative to the ethanol control spore counts (light gray bars). Differences between the two treatments for each strain are denoted as follows: *p < 0.05; **p < 0.01; ***p < 0.001, determined by two-tailed unpaired Student’s T-tests.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3475224&req=5

toxins-04-00695-f005: Spores were counted from the area of a plate surrounding a disk soaked with ethanol or linoleic acid in ethanol. The counts from the ethanol control disks were set to one, and the spore totals from the same strain exposed to linoleic acid (dark gray bars) were expressed relative to the ethanol control spore counts (light gray bars). Differences between the two treatments for each strain are denoted as follows: *p < 0.05; **p < 0.01; ***p < 0.001, determined by two-tailed unpaired Student’s T-tests.

Mentions: Next the three mutants were assessed for their ability to respond to linoleic acid (LA), a known inducer of conidiation in A. flavus [29]. Conidiation was measured in response to disks containing 1 mg LA or an ethanol control (Figure 5). As previously reported, the wild type exhibited a significant increase in conidiation in response to LA (p = 0.003). In a similar fashion, all three mutants also produced significantly more conidia when exposed to LA (p = 0.002 for ∆gprC, p = 0.001 for ∆gprD, and p = 0.0008 for KD::gprCD). Although the relative increase in conidiation for the KD::gprCD strain from the ethanol control, 5.5-fold, was greater than that of any other strain tested, it still produced fewer conidia than any of the other strains (data not shown), as seen in the previous experiments.


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

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

Spores were counted from the area of a plate surrounding a disk soaked with ethanol or linoleic acid in ethanol. The counts from the ethanol control disks were set to one, and the spore totals from the same strain exposed to linoleic acid (dark gray bars) were expressed relative to the ethanol control spore counts (light gray bars). Differences between the two treatments for each strain are denoted as follows: *p < 0.05; **p < 0.01; ***p < 0.001, determined by two-tailed unpaired 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-f005: Spores were counted from the area of a plate surrounding a disk soaked with ethanol or linoleic acid in ethanol. The counts from the ethanol control disks were set to one, and the spore totals from the same strain exposed to linoleic acid (dark gray bars) were expressed relative to the ethanol control spore counts (light gray bars). Differences between the two treatments for each strain are denoted as follows: *p < 0.05; **p < 0.01; ***p < 0.001, determined by two-tailed unpaired Student’s T-tests.
Mentions: Next the three mutants were assessed for their ability to respond to linoleic acid (LA), a known inducer of conidiation in A. flavus [29]. Conidiation was measured in response to disks containing 1 mg LA or an ethanol control (Figure 5). As previously reported, the wild type exhibited a significant increase in conidiation in response to LA (p = 0.003). In a similar fashion, all three mutants also produced significantly more conidia when exposed to LA (p = 0.002 for ∆gprC, p = 0.001 for ∆gprD, and p = 0.0008 for KD::gprCD). Although the relative increase in conidiation for the KD::gprCD strain from the ethanol control, 5.5-fold, was greater than that of any other strain tested, it still produced fewer conidia than any of the other strains (data not shown), as seen in the previous experiments.

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