Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 109, Issue 7, Pages 2666-2671Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1118650109
Keywords
arbuscular mycorrhiza; arginine catabolism; carbon transport; Glomus intraradices; urea cycle
Categories
Funding
- National Science Foundation [0943338, 1051397]
- Netherlands Organization for Scientific Research
- Direct For Biological Sciences
- Division Of Integrative Organismal Systems [0943338, 1051397] Funding Source: National Science Foundation
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The arbuscular mycorrhizal (AM) symbiosis, formed between the majority of land plants and ubiquitous soil fungi of the phylum Glomeromycota, is responsible for massive nutrient transfer and global carbon sequestration. AM fungi take up nutrients from the soil and exchange them against photosynthetically fixed carbon (C) from the host. Recent studies have demonstrated that reciprocal reward strategies by plant and fungal partners guarantee a fair trade of phosphorus against C between partners [Kiers ET, et al. (2011) Science 333: 880-882], but whether a similar reward mechanism also controls nitrogen (N) flux in the AM symbiosis is not known. Using mycorrhizal root organ cultures, we manipulated the C supply to the host and fungus and followed the uptake and transport of N sources in the AM symbiosis, the enzymatic activities of arginase and urease, and fungal gene expression in the extraradical and intraradical mycelium. We found that the C supply of the host plant triggers the uptake and transport of N in the symbiosis, and that the increase in N transport is orchestrated by changes in fungal gene expression. N transport in the symbiosis is stimulated only when the C is delivered by the host across the mycorrhizal interface, not when C is supplied directly to the fungal extraradical mycelium in the form of acetate. These findings support the importance of C flux from the root to the fungus as a key trigger for N uptake and transport and provide insight into the N transport regulation in the AM symbiosis.
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