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¹³C Incorporation into Signature Fatty Acids as an Assay for Carbon Allocation in Arbuscular Mycorrhiza
- Olsson, Pål Axel, van Aarle, Ingrid M., Gavito, Mayra E., Bengtson, Per, Bengtsson, Göran
- Applied and environmental microbiology 2005 v.71 no.5 pp. 2592-2599
- Glomus intraradices, vesicular arbuscular mycorrhizae, lipogenesis, long chain fatty acids, lipids, carbon, stable isotopes, isotope labeling, Gigaspora margarita, mycelium, roots, nutrient transport, symbiosis, Allium porrum, leeks, Plantago lanceolata, Trifolium subterraneum
- The ubiquitous arbuscular mycorrhizal fungi consume significant amounts of plant assimilated C, but this C flow has been difficult to quantify. The neutral lipid fatty acid 16:1[omega]5 is a quantitative signature for most arbuscular mycorrhizal fungi in roots and soil. We measured carbon transfer from four plant species to the arbuscular mycorrhizal fungus Glomus intraradices by estimating ¹³C enrichment of 16:1[omega]5 and compared it with ¹³C enrichment of total root and mycelial C. Carbon allocation to mycelia was detected within 1 day in monoxenic arbuscular mycorrhizal root cultures labeled with [¹³C]glucose. The ¹³C enrichment of neutral lipid fatty acid 16:1[omega]5 extracted from roots increased from 0.14% 1 day after labeling to 2.2% 7 days after labeling. The colonized roots usually were more enriched for ¹³C in the arbuscular mycorrhizal fungal neutral lipid fatty acid 16:1[omega]5 than for the root specific neutral lipid fatty acid 18:2[omega]6,9. We labeled plant assimilates by using ¹³CO₂ in whole-plant experiments. The extraradical mycelium often was more enriched for ¹³C than was the intraradical mycelium, suggesting rapid translocation of carbon to and more active growth by the extraradical mycelium. Since there was a good correlation between ¹³C enrichment in neutral lipid fatty acid 16:1[omega]5 and total ¹³C in extraradical mycelia in different systems (r² = 0.94), we propose that the total amount of labeled C in intraradical and extraradical mycelium can be calculated from the ¹³C enrichment of 16:1[omega]5. The method described enables evaluation of C flow from plants to arbuscular mycorrhizal fungi to be made without extraction, purification and identification of fungal mycelia.