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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) Spores were counted from strains grown on plates containing extracts from uninoculated media (light gray bars) or spent medium of high-density wild type cultures (dark gray bars). The spore counts from plates with the media control extract were set to one, and the spore counts from the same strain exposed to the high-density extract were expressed in relation to the media control counts. Differences between the two treatments for each strain are denoted as follows: *p < 0.05; **p < 0.01, determined by two-tailed unpaired Student’s T-tests; (b) A sample of the plates is shown, containing a set of cultures exposed to the media control extract (light gray bar) and a set exposed to the high-density wild type extract (dark gray bar).
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toxins-04-00695-f004: (a) Spores were counted from strains grown on plates containing extracts from uninoculated media (light gray bars) or spent medium of high-density wild type cultures (dark gray bars). The spore counts from plates with the media control extract were set to one, and the spore counts from the same strain exposed to the high-density extract were expressed in relation to the media control counts. Differences between the two treatments for each strain are denoted as follows: *p < 0.05; **p < 0.01, determined by two-tailed unpaired Student’s T-tests; (b) A sample of the plates is shown, containing a set of cultures exposed to the media control extract (light gray bar) and a set exposed to the high-density wild type extract (dark gray bar).

Mentions: Because it appeared that depletion of both gprC and gprD caused the fungus to stay locked in a low-density development pattern, we hypothesized that these receptors may be required for transmitting a signal produced at high density. The extract from the spent medium of a high density culture induced a significant increase in conidiation in the wild type [16], so this extract and an extract from un-inoculated plates (media control) were applied to cultures of the gprC and gprD mutants (Figure 4). As previously reported, the high-density extract stimulated a significant increase in conidiation when applied to the wild type (p = 0.002). In contrast to wild type, conidiation for all three mutants appeared to be slightly decreased in response to the high-density extract, though this was only minimally significant for the ∆gprC strain (p = 0.049).


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

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

(a) Spores were counted from strains grown on plates containing extracts from uninoculated media (light gray bars) or spent medium of high-density wild type cultures (dark gray bars). The spore counts from plates with the media control extract were set to one, and the spore counts from the same strain exposed to the high-density extract were expressed in relation to the media control counts. Differences between the two treatments for each strain are denoted as follows: *p < 0.05; **p < 0.01, determined by two-tailed unpaired Student’s T-tests; (b) A sample of the plates is shown, containing a set of cultures exposed to the media control extract (light gray bar) and a set exposed to the high-density wild type extract (dark gray bar).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

toxins-04-00695-f004: (a) Spores were counted from strains grown on plates containing extracts from uninoculated media (light gray bars) or spent medium of high-density wild type cultures (dark gray bars). The spore counts from plates with the media control extract were set to one, and the spore counts from the same strain exposed to the high-density extract were expressed in relation to the media control counts. Differences between the two treatments for each strain are denoted as follows: *p < 0.05; **p < 0.01, determined by two-tailed unpaired Student’s T-tests; (b) A sample of the plates is shown, containing a set of cultures exposed to the media control extract (light gray bar) and a set exposed to the high-density wild type extract (dark gray bar).
Mentions: Because it appeared that depletion of both gprC and gprD caused the fungus to stay locked in a low-density development pattern, we hypothesized that these receptors may be required for transmitting a signal produced at high density. The extract from the spent medium of a high density culture induced a significant increase in conidiation in the wild type [16], so this extract and an extract from un-inoculated plates (media control) were applied to cultures of the gprC and gprD mutants (Figure 4). As previously reported, the high-density extract stimulated a significant increase in conidiation when applied to the wild type (p = 0.002). In contrast to wild type, conidiation for all three mutants appeared to be slightly decreased in response to the high-density extract, though this was only minimally significant for the ∆gprC strain (p = 0.049).

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