Identification and interest of molecular markers to monitor plant Pi status.

Background: Inorganic phosphate (Pi) is the sole source of phosphorus for plants. It is a limiting factor for plant yield in most soils worldwide. Due to economic and environmental constraints, the use of Pi fertilizer is and will be more and more limited.

Overexpression of the transporter in alters the phosphorus accumulation of and the distribution of HcPT2 in ectomycorrhizae.

Ectomycorrhizal (ECM) fungi are associated with the roots of woody plants in temperate and boreal forests and help them to acquire water and nutrients, particularly phosphorus (P). However, the molecular mechanisms responsible for the transfer of P from the fungus to the plant in ectomycorrhizae are still poorly understood. In the model association between the ECM fungus and its host plant , we have shown that the fungus, which possesses three H+:Pi symporters (HcPT1.

Improved rock phosphate dissolution from organic acids is driven by nitrate assimilation of bacteria isolated from nitrate and CaCO3-rich soil.

Until now, the solubilization capacities of insoluble mineral P by soil microorganisms have been screened in vitro with media containing NH4+ as a nitrogen source. This presence of NH4+ will lead to an acidification of the medium responsible for the solubilization of the insoluble P. However, besides proton release, the production of organic acids can play a very important role in the release of free P.

Agroecosystem diversification with legumes or non-legumes improves differently soil fertility according to soil type.

Plant diversification through crop rotation or agroforestry is a promising way to improve sustainability of agroecosystems. Nonetheless, criteria to select the most suitable plant communities for agroecosystems diversification facing contrasting environmental constraints need to be refined. Here, we compared the impacts of 24 different plant communities on soil fertility across six tropical agroecosystems: either on highly weathered Ferralsols, with strong P limitation, or on partially weathered soils derived from volcanic material, with major N limitation.

The grazing activity of sp. drives phytate mineralisation within its trophic relationship with bacteria.

The microbial loop has been suggested as an alternative route for better utilization of phytate, a poorly available P source to plants. We hypothesized that bacterial grazer activity might dramatically enhance bacterial migration and proliferation, increasing the probability of phytate hydrolysis by bacterial phytases and, thus, phytate mineralization and release of free phosphate. We tested this hypothesis in a two-compartment system with a solid medium containing phytate or free phosphate as the source of P.

A dansyl-derivatized phytic acid analogue as a fluorescent substrate for phytases: experimental and computational approach.

A new myo-inositol pentakisphosphate was synthesized, which featured a dansyl group at position C-5. The fluorescent tag was removed from the inositol by a 6-atom spacer to prevent detrimental steric interactions in the catalytic site of phytases. The PEG linker was used in order to enhance hydrophilicity and biocompatibility of the new artificial substrate.

How deep can ectomycorrhizas go? A case study on Pisolithus down to 4 meters in a Brazilian eucalypt plantation.

Despite the strong ecological importance of ectomycorrhizal (ECM) fungi, their vertical distribution remains poorly understood. To our knowledge, ECM structures associated with trees have never been reported in depths below 2 meters. In this study, fine roots and ECM root tips were sampled down to 4-m depth during the digging of two independent pits differing by their water availability.

Phosphorus Transport in Mycorrhiza: How Far Are We?

Mycorrhizal fungi considerably improve plant nutrition and help them to cope with changing environments. Particularly, these fungi express proteins to transfer inorganic phosphate (P) from the soil to colonized roots through symbiotic interfaces. The mechanisms involved in P transfer from fungal to plant cells are still largely unknown.

HcPT1.2 participates in Pi acquisition in Hebeloma cylindrosporum external hyphae of ectomycorrhizas under high and low phosphate conditions.

Ectomycorrhizal fungi improve tree phosphorus nutrition through transporters specifically localized at soil-hyphae and symbiotic interfaces. In the model symbiosis between the fungus Hebeloma cylindrosporum and the maritime pine (Pinus pinaster), several transporters possibly involved in phosphate fluxes were identified, including three H:Pi transporters. Among these three, we recently unraveled the function of one of them, named HcPT2, in both pure culture and symbiotic interaction with P.

and P-NMR Study of the Phosphate Transport and Polyphosphate Metabolism in in Response to Plant Roots Signals.

We used and phosphorus-31 nuclear magnetic resonance (P-NMR) spectroscopy to follow the change in transport, compartmentation and metabolism of phosphate in the ectomycorrhizal fungus in response to root signals originating from host () or non-host () plants. A device was developed for the studies allowing the circulation of a continuously oxygenated mineral solution in an NMR tube containing the mycelia. The studies were performed on fungal material after several consecutive treatment steps (freezing in liquid nitrogen; crushing with perchloric acid; elimination of perchloric acid; freeze-drying; dissolution in an appropriate liquid medium).

The Hebeloma cylindrosporum HcPT2 Pi transporter plays a key role in ectomycorrhizal symbiosis.

Through a mutualistic relationship with woody plant roots, ectomycorrhizal fungi provide growth-limiting nutrients, including inorganic phosphate (Pi), to their host. Reciprocal trades occur at the Hartig net, which is the symbiotic interface of ectomycorrhizas where the two partners are symplasmically isolated. Fungal Pi must be exported to the symbiotic interface, but the proteins facilitating this transfer are unknown.

Nitrogen and phosphate metabolism in ectomycorrhizas.

1047 I. Introduction 1047 II. Mobilization of soil N/P by ECM fungi 1048 III.

Establishing a Symbiotic Interface between Cultured Ectomycorrhizal Fungi and Plants to Follow Fungal Phosphate Metabolism.

In ectomycorrhizal plants, the fungal cells colonize the roots of their host plant to create new organs called ectomycorrhizae. In these new organs, the fungal cells colonize the walls of the cortical cells, bathing in the same apoplasm as the plant cells in a space named the 'Hartig net', where exchanges between the two partners take place. Finally, the efficiency of ectomycorrhizal fungi to improve the phosphorus nutrition of their host plants will depend on the regulation of phosphate transfer from the fungal cells to plant cells in the Hartig net through as yet unknown mechanisms.

A Method for Radioactive Labelling of to Study Plant-fungus Interactions.

In order to quantify P accumulation and P efflux in the ectomycorrhizal basidiomycete fungus , we supplied P to mycelia previously grown in liquid medium. The culture had four main steps that are 1) growing the mycelium on complete medium with P, 2) transfer the mycelia into new culture solution with or without P, 3) adding a solution containing P and 4) rinsing the mycelia before incubation with or without plant. The main point is to rinse very carefully the mycelia after P supply in order to avoid overestimation of P efflux into the medium.

The host plant Pinus pinaster exerts specific effects on phosphate efflux and polyphosphate metabolism of the ectomycorrhizal fungus Hebeloma cylindrosporum: a radiotracer, cytological staining and P NMR spectroscopy study.

Ectomycorrhizal (ECM) association can improve plant phosphorus (P) nutrition. Polyphosphates (polyP) synthesized in distant fungal cells after P uptake may contribute to P supply from the fungus to the host plant if they are hydrolyzed to phosphate in ECM roots then transferred to the host plant when required. In this study, we addressed this hypothesis for the ECM fungus Hebeloma cylindrosporum grown in vitro and incubated without plant or with host (Pinus pinaster) and non-host (Zea mays) plants, using an experimental system simulating the symbiotic interface.

From soil to plant, the journey of P through trophic relationships and ectomycorrhizal association.

Phosphorus (P) is essential for plant growth and productivity. It is one of the most limiting macronutrients in soil because it is mainly present as unavailable, bound P whereas plants can only use unbound, inorganic phosphate (Pi), which is found in very low concentrations in soil solution. Some ectomycorrhizal fungi are able to release organic compounds (organic anions or phosphatases) to mobilize unavailable P.

Localization of the Bacillus subtilis beta-propeller phytase transcripts in nodulated roots of Phaseolus vulgaris supplied with phytate.

Soil organic phosphorus (Po) such as phytate, which comprises up to 80 % of total Po, must be hydrolyzed by specific enzymes called phytases to be used by plants. In contrast to plants, bacteria, such as Bacillus subtilis, have the ability to use phytate as the sole source of P due to the excretion of a beta-propeller phytase (BPP). In order to assess whether the B.

Potassium nutrition of ectomycorrhizal Pinus pinaster: overexpression of the Hebeloma cylindrosporum HcTrk1 transporter affects the translocation of both K(+) and phosphorus in the host plant.

Mycorrhizal associations are known to improve the hydro-mineral nutrition of their host plants. However, the importance of mycorrhizal symbiosis for plant potassium nutrition has so far been poorly studied. We therefore investigated the impact of the ectomycorrhizal fungus Hebeloma cylindrosporum on the potassium nutrition of Pinus pinaster and examined the involvement of the fungal potassium transporter HcTrk1.

Promoter-dependent expression of the fungal transporter HcPT1.1 under Pi shortage and its spatial localization in ectomycorrhiza.

Mycorrhizal exchange of nutrients between fungi and host plants involves a specialization and polarization of the fungal plasma membrane adapted for the uptake from the soil and for secretion of nutrient ions towards root cells. In addition to the current progress in identification of membrane transport systems of both symbiotic partners, data concerning the transcriptional and translational regulation of these proteins are needed to elucidate their role for symbiotic functions. To answer whether the formerly described Pi-dependent expression of the phosphate transporter HcPT1.

Biotrophic transportome in mutualistic plant-fungal interactions.

Understanding the mechanisms that underlie nutrient use efficiency and carbon allocation along with mycorrhizal interactions is critical for managing croplands and forests soundly. Indeed, nutrient availability, uptake and exchange in biotrophic interactions drive plant growth and modulate biomass allocation. These parameters are crucial for plant yield, a major issue in the context of high biomass production.