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Institut national de la recherche agronomique (INRA), Unit Mixte de Recherche 1136 Interactions Arbres/Microorganismes, Laboratoire dexcellence Recherches Avancs sur la Biologie de lArbre et les Ecosystmes Forestiers (ARBRE), Centre INRA-Lorraine, 54280 Champenoux, France.
Universit de Lorraine,
Unit Mixte de Recherche 1136 Interactions Arbres/ Microorganismes, Laboratoire dexcellence Recherches Avances sur la Biologie de lArbre et les Ecosystmes Forestiers (ARBRE), 54500 Vandoeuvre-ls-Nancy, France.
Biology Department, Clark University, Lasry Center for Bioscience, 950 Main Street, Worcester, Massachusetts 01610, USA.
Correspondence to F.M. mailto:[email protected]
Web End [email protected]
doi:http://dx.doi.org/10.1038/nrmicro.2016.149
Web End =10.1038/nrmicro.2016.149 Published online 31 Oct 2016
One of the most fundamental requirements for forest trees to flourish is the ability to acquire limited nutrients, such as nitrogen and phosphorus, and water from soil. As the levels of bioavailable inorganic nutrients in forest soils are often too low to sustain plant growth, most trees rely on mycorrhizal fungal symbioses for their nutrition1,2. As such, the establishment of the mycorrhizal lifestyle was a pivotal event in the evolutionary history of land plants3,4. Subsequently, soilborne mycorrhizal fungi, such as arbuscular mycorrhizal fungi and ecto mycorrhizal fungi(BOX1), helped to shape plant communities through mutualistic relationships with
rhizoid-based rooting systems and roots58 (BOX2).
A remarkable number of ectomycorrhizal basidiomycetes and ascomycetes (more than 20,000 species) have established symbioses with ~6,000 tree species, including pines, beeches, oaks, eucalypts, dipterocarps and poplars, whereas arbuscular mycorrhizal glomeromycetes have established symbioses with ~200,000 plant species, including poplars, eucalypts and some gymnosperms2,6,9.
Thus, these symbioses have a broad influence on forest ecosystems. For example, extensive forests across the temperate, boreal, subtropical and mountainous ecoregions of the Northern Hemisphere and Southern Hemisphere are composed of tree species that have been colonized by ectomycorrhizal fungi1,2,10. In each of these forests, trillions of plant rootlets are colonized and interconnected by the mycelium of hundreds of different species of ectomycorrhizal fungi, forming extraradicular mycorrhizal networks that have been informally termed the woodwide web (REFS1113).
It is important to note that ectomycorrhizal fungi occupy a dual niche; that is, the soil and the host root. Similarly to their saprotrophic ancestors, ectomy corrhizal fungi have access to mineral nutrients in the soil that are efficiently absorbed by the perennial absorbing mycelial network and partly translocated to the host root1,9,14. However, ectomycorrhizal fungi have lost much...