Characterization of root-associated microbiota of non-mycorrhizal plants and its contribution to phosphorus nutrition
Résumé
Most land plants rely on the arbuscular mycorrhizal symbiosis for their phosphorus (P) uptake. However, there are non-mycorrhizal (NM) plant lineages (e.g. Brassicaceae, Cyperaceae and Caryophyllaceae families) that lost the ability to establish this symbiosis and it is still not clear how these plants acquire enough P to grow, especially in P-depleted soils. Recent studies suggest a potential role of newly-discovered fungi in the P nutrition of these NM plants. Indeed, it was shown that some fungi, phylogenetically distant from mycorrhizal lineages (e.g. Helotiales strain F229, Colletotrichum tofieldiae, Serendipita indica) have mycorrhizal-like features, including enhancing plant P acquisition by transferring P directly from the substrate to Brassicaceae NM species. However, the contribution of these “mycorrhizal-like” fungi to P nutrition of NM plants remains unexplored. We put forward the hypothesis that mycorrhizal-like fungi functionally replace arbuscular mycorrhizal fungi in NM plants, contributing significantly to the P nutrition of these plants. We conducted a large-scale analysis (using ITS2 metabarcoding) of the fungal root microbiota of 39 wild-growing NM and mycorrhizal plant species, along a gradient of soil P concentrations, to have a first characterization of the microbiota of these plants and identify their specificities. We will also present correlation data between P acquisition of NM plants and the composition of the fungal microbiota with the aim to pinpoint potential mycorrhizal-like taxa. Our final goal is to quantify the contribution of these fungi to the P nutrition of NM plants and determine if these associations could be a new adaptation balancing the loss of the mycorrhizal symbiosis in NM plants.