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.
Ozturk, M. p53 mutation in hepatocellular carcinoma after aflatoxin exposure. Lancet 1991, 338, 1356–1359, doi:10.1016/0140-6736(91)92236-U.
[3]
Gouas, D.; Shi, H.; Hainaut, P. The aflatoxin-induced TP53 mutation at codon 249 (R249S): Biomarker of exposure, early detection and target for therapy. Cancer Lett. 2009, 286, 29–37, doi:10.1016/j.canlet.2009.02.057.
[4]
Yu, J.; Cleveland, T.E.; Nierman, W.C.; Bennett, J.W. Aspergillus flavus genomics: Gateway to human and animal health, food safety, and crop resistance to disease. Rev. Iberoam. Micol. 2005, 22, 194–202, doi:10.1016/S1130-1406(05)70043-7.
[5]
Lewis, L.; Onsongo, M.; Njapau, H.; Schurz-Rogers, H.; Luber, G.; Kieszak, S.; Nyamongo, J.; Backer, L.; Dahiye, A.M.; Misore, A.; et al. Aflatoxin contamination of commercial maize products during an outbreak of acute aflatoxicosis in eastern and central Kenya. Environ. Health Perspect. 2005, 113, 1763–1767.
[6]
Boyce, J.A. Mast cells and eicosanoid mediators: A system of reciprocal paracrine and autocrine regulation. Immunol. Rev. 2007, 217, 168–185, doi:10.1111/j.1600-065X.2007.00512.x.
[7]
Affeldt, K.J.; Keller, N.P. Oxylipins in Fungal-Mammalian. Interactions. In Biocommunications of Fungi; Witzany, G., Ed.; Springer: Houten, The Netherlands, 2012; pp. 291–303.
[8]
Christensen, S.A.; Kolomiets, M.V. The lipid language of plant-fungal interactions. Fungal Genet. Biol. 2011, 48, 4–14, doi:10.1016/j.fgb.2010.05.005.
[9]
León-Morcillo, R.J.; Angel, J.; Martín-Rodríguez; Vierheilig, H.; Ocampo, J.A.; García-Garrido, J.M. Late activation of the 9-oxylipin pathway during arbuscular mycorrhiza formation in tomato and its regulation by jasmonate signalling. J. Exp. Bot. 2012, 63, 3545–3558, doi:10.1093/jxb/ers010.
Tsitsigiannis, D.I.; Keller, N.P. Oxylipins as developmental and host-fungal communication signals. Trends Microbiol. 2007, 15, 109–118, doi:10.1016/j.tim.2007.01.005.
[16]
Horowitz Brown, S.; Zarnowski, R.; Sharpee, W.C.; Keller, N.P. Morphological transitions governed by density dependence and lipoxygenase activity in Aspergillus flavus. Appl. Environ. Microbiol. 2008, 74, 5674–5685, doi:10.1128/AEM.00565-08.
[17]
Brown, S.H.; Scott, J.B.; Bhaheetharan, J.; Sharpee, W.C.; Milde, L.; Wilson, R.A.; Keller, N.P. Oxygenase coordination is required for morphological transition and the host-fungus interaction of Aspergillus flavus. Mol. Plant-Microbe Interact 2009, 22, 882–894, doi:10.1094/MPMI-22-7-0882.
[18]
Brodhun, F.; Feussner, I. Oxylipins in fungi. FEBS J. 2011, 278, 1047–1063, doi:10.1111/j.1742-4658.2011.08027.x.
[19]
Tsitsigiannis, D.I.; Zarnowski, R.; Keller, N.P. The lipid body protein, PpoA, coordinates sexual and asexual sporulation in Aspergillus nidulan. J. Biol. Chem. 2004, 279, 11344–11353.
Tsitsigiannis, D.I.; Kowieski, T.M.; Zarnowski, R.; Keller, N.P. Three putative oxylipin biosynthetic genes integrate sexual and asexual development in Aspergillus nidulans. Microbiology 2005, 151, 1809–1821, doi:10.1099/mic.0.27880-0.
[22]
Tsitsigiannis, D.I.; Bok, J.-W.; Andes, D.; Nielsen, K.F.; Frisvad, J.C.; Keller, N.P. Aspergillus cyclooxygenase-like enzymes are associated with prostaglandin production and virulence. Infect. Immun. 2005, 73, 4548–4559, doi:10.1128/IAI.73.8.4548-4559.2005.
[23]
Dagenais, T.R.T.; Chung, D.; Giles, S.S.; Hull, C.M.; Andes, D.; Keller, N.P. Defects in conidiophore development and conidium-macrophage interactions in a dioxygenase mutant of Aspergillus fumigatus. Infect. Immun. 2008, 76, 3214–3220, doi:10.1128/IAI.00009-08.
[24]
Jarosz, L.M.; Ovchinnikova, E.S.; Meijler, M.M.; Krom, B.P. Microbial spy games and host response: Roles of a Pseudomonas aeruginosa small molecule in communication with other species. PLoS Pathog. 2011, 7, e1002312, doi:10.1371/journal.ppat.1002312.
[25]
Albuquerque, P.; Casadevall, A. Quorum sensing in fungi—A review. Med. Mycol. 2012, 50, 337–345.
[26]
Singh, A.; del Poeta, M. Lipid signalling in pathogenic fungi. Cell. Microbiol. 2011, 13, 177–185, doi:10.1111/j.1462-5822.2010.01550.x.
[27]
Herrero-Garcia, E.; Garzia, A.; Cordobés, S.; Espeso, E.A.; Ugalde, U. 8-Carbon oxylipins inhibit germination and growth, and stimulate aerial conidiation in Aspergillus nidulans. Fungal Biol. 2011, 115, 393–400, doi:10.1016/j.funbio.2011.02.005.
Calvo, A.M.; Hinze, L.L.; Gardner, H.W.; Keller, N.P. Sporogenic effect of polyunsaturated fatty acids on development of Aspergillus spp. Appl. Environ. Microbiol. 1999, 65, 3668–3673.
[30]
Ricciotti, E.; Fitzgerald, G.A. Prostaglandins and inflammation. Arterioscler. Thromb. Vasc. Biol. 2011, 31, 986–1000, doi:10.1161/ATVBAHA.110.207449.
[31]
Singh, R.K.; Gupta, S.; Dastidar, S.; Ray, A. Cysteinyl leukotrienes and their receptors: Molecular and functional characteristics. Pharmacology 2010, 85, 336–349, doi:10.1159/000312669.
[32]
Folcik, V.A.; Cathcart, M.K. Predominance of esterified hydroperoxy-linoleic acid in human monocyte-oxidized LDL. J. Lipid Res. 1994, 35, 1570–1582.
[33]
Kühn, H. Biosynthesis, metabolization and biological importance of the primary 15-lipoxygenase metabolites 15-hydro(pero)xy-5Z,8Z,11Z,13E-eicosatetraenoic acid and 13-hydro(pero)xy-9Z,11E-octadecadienoic acid. Prog. Lipid Res. 1996, 35, 203–226, doi:10.1016/S0163-7827(96)00008-2.
[34]
Hattori, T.; Obinata, H.; Ogawa, A.; Kishi, M.; Tatei, K.; Ishikawa, O.; Izumi, T. G2A plays proinflammatory roles in human keratinocytes under oxidative stress as a receptor for 9-hydroxyoctadecadienoic acid. J. Invest. Dermatol. 2007, 128, 1123–1133.
[35]
Obinata, H.; Hattori, T.; Nakane, S.; Tatei, K.; Izumi, T. Identification of 9-hydroxyoctadecadienoic acid and other oxidized free fatty acids as ligands of the G protein-coupled receptor G2A. J. Biol. Chem. 2005, 280, 40676–40683.
[36]
Obinata, H.; Izumi, T. G2A as a receptor for oxidized free fatty acids. Prostaglandins Other Lipid Mediat. 2009, 89, 66–72, doi:10.1016/j.prostaglandins.2008.11.002.
Li, L.; Wright, S.J.; Krystofova, S.; Park, G.; Borkovich, K.A. Heterotrimeric G protein signaling in filamentous fungi. Annu. Rev. Microbiol. 2007, 61, 423–452, doi:10.1146/annurev.micro.61.080706.093432.
[41]
Xue, C.; Hsueh, Y.; Heitman, J. Magnificent seven: Roles of G protein-coupled receptors in extracellular sensing in fungi. FEMS Microbiol. Rev. 2008, 32, 1010–1032, doi:10.1111/j.1574-6976.2008.00131.x.
[42]
Shimizu, K.; Keller, N.P. Genetic involvement of a cAMP-dependent protein kinase in a G protein signaling pathway regulating morphological and chemical transitions in Aspergillus nidulans. Genetics 2001, 157, 591–600.
[43]
Shimizu, K.; Hicks, J.K.; Huang, T.-P.; Keller, N.P. Pka, Ras and RGS protein interactions regulate activity of AflR, a Zn(II)2Cys6 transcription factor in Aspergillus nidulan. Genetics 2003, 165, 1095–1104.
[44]
Fillinger, S.; Chaveroche, M.-K.; Shimizu, K.; Keller, N.; d’Enfert, C. cAMP and ras signalling independently control spore germination in the filamentous fungus Aspergillus nidulans. Mol. Microbiol. 2002, 44, 1001–1016, doi:10.1046/j.1365-2958.2002.02933.x.
[45]
Roze, L.V.; Beaudry, R.M.; Keller, N.P.; Linz, J.E. Regulation of aflatoxin synthesis by FadA/cAMP/protein kinase A signaling in Aspergillus parasiticus. Mycopathologia 2004, 158, 219–232, doi:10.1023/B:MYCO.0000041841.71648.6e.
[46]
Lafon, A.; Seo, J.-A.; Han, K.-H.; Yu, J.-H.; d’Enfert, C. The heterotrimeric G-protein GanB(α)-SfaD(β)-GpgA(γ) is a carbon source sensor involved in early cAMP-dependent germination in Aspergillus nidulans. Genetics 2005, 171, 71–80, doi:10.1534/genetics.105.040584.
[47]
Liavonchanka, A.; Feussner, I. Lipoxygenases: Occurrence, functions and catalysis. J. Plant Physiol. 2006, 163, 348–357, doi:10.1016/j.jplph.2005.11.006.
Seo, J.-A.; Han, K.-H.; Yu, J.-H. The gprA and gprB genes encode putative G protein-coupled receptors required for self-fertilization in Aspergillus nidulans. Mol. Microbiol. 2004, 53, 1611–1623, doi:10.1111/j.1365-2958.2004.04232.x.
[50]
Han, K.; Seo, J.; Yu, J. A putative G protein-coupled receptor negatively controls sexual development in Aspergillus nidulans. Mol. Microbiol. 2004, 51, 1333–1345, doi:10.1111/j.1365-2958.2003.03940.x.
[51]
He, Z.-M.; Price, M.S.; Obrian, G.R.; Georgianna, D.R.; Payne, G.A. Improved protocols for functional analysis in the pathogenic fungus Aspergillus flavus. BMC Microbiol 2007, 7.
[52]
McDonald, T.; Brown, D.; Keller, N.P.; Hammond, T.M. RNA silencing of mycotoxin production in Aspergillus and Fusarium species. Mol. Plant Microbe Interact 2005, 18, 539–545, doi:10.1094/MPMI-18-0539.
