Dependence of arbuscular-mycorrhizal fungi on their plant host for palmitic acid synthesis.
Lipids are the major form of carbon storage in arbuscular-mycorrhizal fungi. We studied fatty acid synthesis by Glomus intraradices and Gigaspora rosea. [(14)C]Acetate and [(14)C]sucrose were incorporated into a synthetic culture medium to test fatty acid synthetic ability in germinating spores (G. intraradices and G. rosea), mycorrhized carrot roots, and extraradical fungal mycelium (G. intraradices). Germinating spores and extraradical hyphae could not synthesize 16-carbon fatty acids but could elongate and desaturate fatty acids already present. The growth stimulation of germinating spores by root exudates did not stimulate fatty acid synthesis. 16-Carbon fatty acids (16:0 and 16:1) were synthesized only by the fungi in the mycorrhized roots. Our data strongly suggest that the fatty acid synthase activity of arbuscular-mycorrhizal fungi is expressed exclusively in the intraradical mycelium and indicate that fatty acid metabolism may play a major role in the obligate biotrophism of arbuscular-mycorrhizal fungi.
Trépanier
Martin
M
Centre de Recherche en Horticulture, Pavillon de l'Envirotron, Université Laval, Québec G1K 7P4, Canada. Martin.Trepanier@FSAA.ulaval.ca
Bécard
Guillaume
G
Moutoglis
Peter
P
Willemot
Claude
C
Gagné
Serge
S
Avis
Tyler J
TJ
Rioux
Jacques-André
JA
D000085:Acetates / Q000378:metabolism; D002250:Carbon Radioisotopes / Q000378:metabolism; D003470:Culture Media; D018552:Daucus carota / Q000382:microbiology*; D064429:Fatty Acid Synthases / Q000378:metabolism; D005227:Fatty Acids / Q000032:analysis; D005658:Fungi / Q000737:chemistry / Q000201:enzymology* / Q000254:growth & development; D015966:Gene Expression Regulation, Fungal; D025282:Mycelium / Q000201:enzymology; D038821:Mycorrhizae / Q000737:chemistry / Q000201:enzymology* / Q000254:growth & development; D019697:Onions / Q000382:microbiology*; D019308:Palmitic Acid / Q000378:metabolism*; D013172:Spores, Fungal / Q000502:physiology; D013395:Sucrose / Q000378:metabolism; D013559:Symbiosis
D000085:Acetates; D002250:Carbon Radioisotopes; D003470:Culture Media; D005227:Fatty Acids; D019308:Palmitic Acid; D013395:Sucrose; D064429:Fatty Acid Synthases