Lipid metabolism of the endomycorrhizal fungus: Glomus intraradices.

Lipid metabolism of the endomycorrhizal fungus: Glomus intraradices. The us e of monoxenic cultures of the obligately biotrophic vesicular arbuscular f ungus Glomus intraradices now permits investigation of the lipid metabolism of this organism. In bicompartmental culture plates, sporulating extraradi cal hyphae can be obtained, totally free of roots, and then provided with C -14-acetate as lipid precursor. Three experimental stages were studied: i) stage A, symbiotic stage corresponding to the fungus still attached to the host plant roots, ii) stage B, consisting of the fungus detached from the h ost roots, iii) stage C, germinating spores. In each case, the fungus prove d to be able to synthesise its own lipids: 1,2- and 1,3-diacylglycerols, tr iacylglycerols, phospholipids, sterols and free fatty acids, de novo. Lipid metabolism varied with the experimental conditions. Phospholipid synthesis was intensive in germinating spores. Thus the obligately biotrophic status of this fungus cannot be explained by a deficiency in synthesis of these v arious lipid classes. (C) 2001 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.