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High-throughput sequencing has become a prominent tool to assess plant-associated microbial diversity. Still, some technical challenges remain in characterising these communities, notably due to plant and fungal DNA co-amplification. Fungal-specific primers, Peptide Nucleic Acid (PNA) clamps, or adjusting PCR conditions are approaches to limit plant DNA contamination. However, a systematic comparison of these factors and their interactions, which could limit plant DNA contamination in the study of plant mycobiota, is still lacking. Here, three primers targeting the ITS2 region were evaluated alone or in combination with PNA clamps both on nettle (Urtica dioica) root DNA and a mock community. PNA clamps did not improve the richness or diversity of the fungal communities but increased the number of fungal reads. Among the tested factors, the most significant was the primer pair. Specifically, the 5.8S-Fun/ITS4-Fun pair exhibited a higher OTU richness but fewer fungal reads. Our study demonstrates that the choice of primers is critical for limiting plant and fungal DNA co-amplification. PNA clamps increase the number of fungal reads when ITS2 is targeted but do not result in higher fungal diversity recovery at high sequencing depth. At lower read depths, PNA clamps might enhance microbial diversity quantification for primer pairs lacking fungal specificity. [ABSTRACT FROM AUTHOR]

On a global scale, the effects of human activities, in particular changes in the way land is used and exploited and the resulting contamination, have had profound negative effects on biodiversity and ecosystem functioning. Consequently, restoring the marginal lands through the use of solutions inspired and supported by nature appears to be one of the European Union's main objectives. In this respect, eco-innovative phytotechnologies, such as phytoremediation, have become an important ecological engineering approach for the recovery of contaminated land. A relatively new area of phytoremediation is phytomanagement in which non-food crops with high biomass yields are used to reduce and control the risks associated with soil pollution, while enabling profitable and sustainable use of resources by extracting contaminants and recovering marketable biomass. Consequently, the best choice of plant species is crucial to the successful phytomanagement of contaminated sites. This meta-analysis highlights the importance of using fast-growing plants for phytomanagement purposes, focusing on woody species. Those from the Salicaceae family, which includes poplars (Populus), have attracted the most attention in recent decades. On the basis of this meta-analysis, poplars appear to be the best candidates for the remediation of metal-contaminated soils, particularly when combined with the most appropriate microbial consortia. Finally, we describe the molecular determinants of poplar involved in the management of trace elements (TE), as well as the valorization processes that have been applied to poplar biomass from phytoremediation trials. [ABSTRACT FROM AUTHOR]

Phytotechnologies for the management of lands contaminated with potentially toxic elements (PTEs) are considered as gentle alternatives to conventional remediation techniques. During the last few years, phytotechnologies have progressively shifted to phytomanagement, a concept that includes the valorization of the plant biomass produced on the contaminated site. This study aimed at evaluating the mid-term effect of ecto- and endomycorrhizal inoculation on the reduction of PTE mobility in soils and foliar accumulation by two poplar clones, Skado ( Populus trichocarpa x P. maximowiczii ) and I-214 ( P. deltoides x P. nigra ), dedicated to bioenergy purposes. The effects of inoculation were investigated in two large scale trials of 1 ha each. Poplars grown on highly contaminated soils accumulated excessive Cd and Zn in leaves compared with those planted on less contaminated soils, and the I-214 clone generally accumulated less PTEs than the Skado clone. Interestingly, the filtering capacity of mycorrhizal fungi was significant for Zn, Cu, Pb and Cr in Skado leaves only at the most contaminated areas after two growing seasons. These foliar concentrations were not correlated with Ca(NO 3 ) 2 -extractable concentrations in soils, suggesting that mycorrhizal fungi limited PTE translocation from roots to leaves without impacting PTE mobility in soils. Therefore, the reduction of PTE accumulation in poplar leaves may be optimized by selecting appropriate combinations of cultivars and inocula at specific PTE levels and soil conditions. Because Cd and Zn may pose a risk after leaf abscission and wood harvest, further research is needed to efficiently reduce Cd and Zn concentrations in poplar tissues. Otherwise, the phytomanagement of metal contaminated sites with poplars should include options to safely manage both leaves and wood. [ABSTRACT FROM AUTHOR]

Characterization of microbial communities in stressful conditions at a field level is rather scarce, especially when considering fungal communities from aboveground habitats. We aimed at characterizing fungal communities from different poplar habitats at a Hg-contaminated phytomanagement site by using Illumina-based sequencing, network analysis approach, and direct isolation of Hg-resistant fungal strains. The highest diversity estimated by the Shannon index was found for soil communities, which was negatively affected by soil Hg concentration. Among the significant correlations between soil operational taxonomic units (OTUs) in the co-occurrence network, 80% were negatively correlated revealing dominance of a pattern of mutual exclusion. The fungal communities associated with Populus roots mostly consisted of OTUs from the symbiotic guild, such as members of the Thelephoraceae, thus explaining the lowest diversity found for root communities. Additionally, root communities showed the highest network connectivity index, while rarely detected OTUs from the Glomeromycetes may have a central role in the root network. Unexpectedly high richness and diversity were found for aboveground habitats, compared to the root habitat. The aboveground habitats were dominated by yeasts from the Lalaria, Davidiella, and Bensingtonia genera, not detected in belowground habitats. Leaf and stem habitats were characterized by few dominant OTUs such as those from the Dothideomycete class producing mutual exclusion with other OTUs. Aureobasidium pullulans, one of the dominating OTUs, was further isolated from the leaf habitat, in addition to Nakazawaea populi species, which were found to be Hg resistant. Altogether, these findings will provide an improved point of reference for microbial research on inoculation-based programs of tailings dumps. [ABSTRACT FROM AUTHOR]

We investigated the fate of trace elements (TE) in poplar wood on the conversion of biomass to heat in a 0.2 MW combustion unit equipped with a fabric filter. The phytoremediation wood was harvested from a TE-contaminated agricultural site planted with a high-density poplar stand. The combustion technology used in the present experiment allows for an efficient separation of the various ash fractions. The combustion process concentrates Cu, Cr, and Ni in the bottom ash, heat exchanger ash, and cyclone ash fractions. Therefore, the impact of the fabric filter is negligible for these elements. Conversely, Cd, Pb, and Zn are significantly recovered in the emission fraction in the absence of the fabric filter above the emission limits. The use of a fabric filter will allow the concentration of these three TEs in the ashes collected below the filter, thus complying with all regulatory thresholds, i.e., those from the large combustion plant EU directive. Because the TE concentrations in the different fractions differed significantly, it is recommended that these fractions be treated separately, especially when recycling of ashes from phytoremediation wood through application in agriculture is envisaged. [ABSTRACT FROM AUTHOR]

Abstract: Metal tolerance of filamentous fungi is a poorly understood mechanism. In order to unravel the molecular basis of zinc (Zn) tolerance in the ectomycorrhizal fungal model Hebeloma cylindrosporum, we carried out a functional screening of an H. cylindrosporum cDNA library in the zrc1Δ mutant strain of Saccharomyces cerevisiae to search for genes conferring Zn tolerance to yeast cells. This strategy allowed the isolation of HcZnT1, a gene belonging to the cation diffusion facilitator family, which induced tolerance to Zn, but not to other metals. HcZnT1 was constitutively expressed in Hebeloma cells, whatever the Zn status of the medium and the fungal cell type (mycelia, sporocarps, mycorrhizas). A HcZnT1:GFP fusion protein was expressed in yeast and the corresponding fluorescence was recorded on endoplasmic reticulum membranes. Taken together, these different findings suggest a dual role of HcZnT1 in Zn homeostasis of fungal cells, by supplying requested Zn ions for the functioning of the endoplasmic reticulum as well as by detoxifying the cytosol under Zn stress. Zn pools were also investigated by using the Zn-specific fluorophore zinquin in H. cylindrosporum cells. Zinquin labeling revealed compartmentalization in intracellular vesicles interspersed throughout the cytoplasm that do not correspond to vacuolar compartments. Altogether the present data represent the first steps into the understanding of Zn homeostasis and tolerance in Hebeloma. [Copyright &y& Elsevier]

In mycorrhizal associations, the fungal partner assists its plant host with nitrogen and phosphorus uptake while obtaining photosynthetically fixed carbon. Recent studies in mycorrhiza have highlighted the potential for direct transfer of ammonia from fungal to plant cells. This presents a new perspective on nitrogen transfer at the mycorrhizal interface, which is discussed here in light of recent progress made in characterizing a large array of membrane proteins that could fulfil the function of transporting ammonia. [Copyright &y& Elsevier]

Glutamine synthetase (GS, EC 6.3.1.2) was purified to apparent electrophoretic homogeneity from roots of Pseudotsuga menziesii (Mirb) Franco by a three-step procedure involving diethylaminoethyl (DEAE)-Trisacryl chromatography, affinity chromatography on Matrex Gel Red A, and preparative polyacrylamide gel electrophoresis. The enzyme was purified 40-fold with a 16% recovery. The native enzyme had a molecular mass of 460±5 kDa as estimated by gel filtration, interpolation of the Ferguson plots and non-denaturing gradient-PAGE. It was composed of two different subunits of 54 and 64 kDa. Affinity constants for glutamate (Glu), glutamine (Gln), ATP and ADP were 2.6, 10.5, 0.5 and 0.083 mM, respectively. The enzyme exhibited a negative cooperativity for ammonium (Hill number of 0.7) with two Km values which were 11 and 75µM in the presence of ammonium concentrations lower and higher than 1.3 mM, respectively. Glycine and ADP appeared as potential inhibitors of the GS activity. The optimum pH values were 7.2 and 7.6 for the transferase and the biosynthetic assays, respectively. The enzyme lost 30% of its activity within 25 days of storage at 4°C. The optimum temperatures of activity were 40°C and 45°C for the transferase and biosynthetic activities, respectively. [ABSTRACT FROM AUTHOR]

Studies the kinetics, energetics and specificity of a general amino acid transporter in the ectomycorrhizal fungus Paxillus involutus. Active transport characteristics of amino acid uptake; Inhibitors of amino acid uptake; Consistency of dependence on acidity and inhibition by protonophores.

Examines the pathways of glutamate and glutamine metabolism in the ectomycorrhizal fungus Paxillus involutus. Effects of azaserine, aminooxyacetate and methionine sulfoximine on glutamate and glutamine metabolism.

Growing lignocellulosic crops on marginal lands could compose a substantial proportion of future energy resources. The potential of poplar was explored, by devising a field trial of two hectares in 2007 in a metal-contaminated site to quantify the genotypic variation in the growth traits of 14 poplar genotypes grown in short-rotation coppice and to assess element transfer and export by individual genotypes. Our data led us to conclusions about the genotypic variations in poplar growth on a moderately contaminated site, with the Vesten genotype being the most productive. This genotype also accumulated the least amounts of trace elements, whereas the Trichobel genotype accumulated up to 170 mg Zn kg−1 DW in the branches, with large variation being exhibited among the genotypes for trace element (TE) accumulation. Soil element depletion occurred for a range of TEs, whereas the soil content of major nutrients and the pH remained unchanged or slightly increased after 10 years of poplar growth. The higher TE content of bark tissues compared with the wood and the higher proportion of bark in branches compared with the wood led us to recommend that only stem wood be harvested, instead of the whole tree, which will enable a reduction in the risks encountered with TE-enriched biomass in the valorization process. Unlabelled Image • We observed genotypic variations in growth of poplar at a moderately contaminated site. • There were large variations between genotypes for trace element accumulation. • Soil depletion occurred for a range of trace element after 10 years of growth. • Branches had accumulated a lot more elements than wood. • We recommend choosing stemwood-only harvesting instead of whole-tree harvesting. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) are crucial elements for current high-technology and renewable energy advances. In addition to their increasing usage and their low recyclability leading to their release into the environment, REEs are also used as crop fertilizers. However, little is known regarding the cellular and molecular effects of REEs in plants, which is crucial for better risk assessment, crop safety and phytoremediation. Here, we analysed the ionome and transcriptomic response of Arabidopsis thaliana exposed to a light (lanthanum, La) and a heavy (ytterbium, Yb) REE. At the transcriptome level, we observed the contribution of ROS and auxin redistribution to the modified root architecture following REE exposure. We found indications for the perturbation of Fe homeostasis by REEs in both roots and leaves of Arabidopsis suggesting competition between REEs and Fe. Furthermore, we propose putative ways of entry of REEs inside cells through transporters of microelements. Finally, similar to REE accumulating species, organic acid homeostasis (e.g. malate and citrate) appears critical as a tolerance mechanism in response to REEs. By combining ionomics and transcriptomics, we elucidated essential patterns of REE uptake and toxicity response of Arabidopsis and provide new hypotheses for a better evaluation of the impact of REEs on plant homeostasis. [Display omitted] • Combined transcriptomics and ionomics reveal Arabidopsis thaliana response to REEs. • REEs likely induce ROS and auxin-mediated root architecture modifications. • REE perturbs nutrient homeostasis by competing for cellular transport pathways. • Organic acids could be of importance for REE tolerance. [ABSTRACT FROM AUTHOR]

Rare Earth Elements (REEs) are essential components of modern technology and industry, leading to their increased release into the environment. This review synthesizes current knowledge on the transfer, accumulation, and fractionation of REEs in plants, with a focus on the impacts of REE-triggered stress at different organization levels, and the underlying tolerance mechanisms. We explore the mechanisms governing REE uptake, transport, fractionation and distribution within plants and their potential hormetic and toxic effects under normal and stress conditions. This comprehensive review provides valuable insights into the complex interplay between REE accumulation, stress response, and tolerance mechanisms in plants, fostering a deeper understanding of REE phytotoxicity and the development of sustainable solutions for REE-contaminated ecosystems. [ABSTRACT FROM AUTHOR]

The stinging nettle Urticadioica L. is a perennial crop with low fertilizer and pesticide requirements, well adapted to a wide range of environmental conditions. It has been successfully grown in most European climatic zones while also promoting local flora and fauna diversity. The cultivation of nettle could help meet the strong increase in demand for raw materials based on plant fibers as a substitute for artificial fibers in sectors as diverse as the textile and automotive industries. In the present review, we present a historical perspective of selection, harvest, and fiber processing features where the state of the art of nettle varietal selection is detailed. A synthesis of the general knowledge about its biology, adaptability, and genetics constituents, highlighting gaps in our current knowledge on interactions with other organisms, is provided. We further addressed cultivation and processing features, putting a special emphasis on harvesting systems and fiber extraction processes to improve fiber yield and quality. Various uses in industrial processes and notably for the restoration of marginal lands and avenues of future research on this high-value multi-use plant for the global fiber market are described. [ABSTRACT FROM AUTHOR]

• There is much controversy on the contribution of NADP-dependent glutamate dehydrogenase (NADP-GDH) in NH4+ assimilation in ectomycorrhizal (ECM) fungi and ectomycorrhizas. Experiments reported here provide information on the dispensability of NADP-GDH in various ectomycorrhizal isolates. • Glutamate dehydrogenase and glutamine synthetase (GS) enzyme activities were measured on mycelia grown under various nitrogen (N) conditions. The contribution of GDH in ammonium assimilation was further estimated by following 15N incorporation from (15NH4)2SO4 into glutamate, when GS was inhibited by phosphinothricin. Finally, gene amplification on cDNA and genomic DNA was performed using degenerated primers. • Two groups of fungi could be distinguished. The GDH+ fungi include Hebeloma cylindrosporum-like fungi, which possess a functional NADP-GDH. The GDH− fungi include Paxillus involutus-like fungi for which the NADP-GDH activity, as well as the GDHA transcripts, were not detected, whatever the growth condition. • All the results are consistent with the dispensability of the NADP-GDH function in ECM fungi, suggesting a minor role in ammonium assimilation in ectomycorrhizal fungi. We hypothesize that the lack of a functional NADP-GDH could be an evolutive adaptation in relation to the ecological niche of ECM fungi, rather than a transitional regulation in response to changes in N contents of the extracellular medium. [ABSTRACT FROM AUTHOR]

• In an effort to understand processes that are related to heavy metal sequestration, we characterized six metallothionein genes ( PtdMTs) in the hybrid cottonwood, Populus trichocarpa ×  deltoides. • cDNA microarrays and reverse transcriptase-polymerase chain reaction were used to examine PtdMT expression in poplar tissues. They displayed differential gene expression patterns, which may be associated with the diverse roles and functions PtdMTs have in coping with particular developmental (e.g. root development and leaf senescence) and environmental cues. • The heterologous expression in a cadmium (Cd)-hypersensitive yeast mutant showed the ability of PtdMT cDNAs to confer Cd tolerance. The concentration of PtdMT mRNAs were increased by zinc, but not by copper and Cd. • Further studies will help to clarify the role of metallothionein genes in metal homeostasis and poplar development, and help to isolate poplar genotypes particularly tolerant to stress for use in experiments of phytoremediation. New Phytologist (2004) doi: 10.1111/j.1469-8137.2004.01168.x © New Phytologist (2004) [ABSTRACT FROM AUTHOR]

Investigates cadmium uptake and subcellular compartmentation in the ectomycorrhizal fungus Paxillus involutus. Characterization of the concentration-dependent cadmium-uptake kinetics; Effect of metabolic inhibitors and low temperature on cadmium accumulation; Metal-tolerance mechanisms in mycorrhizal fungi.

Mercury (Hg) is a highly toxic metal with no known biological function, and it can be highly bioavailable in terrestrial ecosystems. Although fungi are important contributors to a number of soil processes including plant nutrient uptake and decomposition, little is known about the effect of Hg on fungi. Fungi accumulate the largest amount of Hg and are the organisms capable of the highest bioaccumulation of Hg. While referring to detailed mechanisms in bacteria, this mini-review emphasizes the progress made recently on this topic and represents the first step towards a better understanding of the mechanisms underlying Hg tolerance and accumulation in fungal species and hence on the role of fungi within the Hg cycle at Hg-contaminated sites. Key points: • The fungal communities are more resilient than bacterial communities to Hg exposure. • The exposure to Hg is a threat to microbial soil functions involved in both C and nutrient cycles. • Fungal (hyper)accumulation of Hg may be important for the Hg cycle in terrestrial environments. • Understanding Hg tolerance and accumulation by fungi may lead to new remediation biotechnologies. [ABSTRACT FROM AUTHOR]

This study aimed to determine the trace element accumulation in the soil and plants in an industrial wasteland and to estimate the extent of transfer to humans to measure the effects on and risks to vegetation and human health and find bioindicator plants representative of the levels of the main contaminants. In areas with the highest extractable trace element levels, we observed decreases in plant biodiversity explained by the disappearance of several families, favouring the coverage of tolerant species, such as Urtica dioica and Hedera helix. Trace elements were also found in the leaves of several plants, especially in a dominant species that is poorly studied, Alliaria petiolata. Indeed, this species had the highest contents of Zn (1750 mg.kg-1 DW), Ni (13.1 mg.kg-1 DW), and Cd (18 mg.kg-1 DW) found at the site and is a potential Zn bioindicator since its leaf contents were also representative of the Zn extractable contents in soil (R² = 0.94). The hazard quotient and carcinogen risk revealed that most of the site had an identified or possible risk, mainly due to Pb and As. Native species, especially A. petiolata , could be used in phytoextraction to manage and limit these human and environmental risks. [Display omitted] • The floristic composition of a wasteland was determined under heterogeneous levels of trace element contamination. • Trace element contamination reduced biodiversity by selecting tolerant species. • The dominant species, Alliaria petiolata , is a potential Zn bioindicator with the highest leaf Zn, Ni and Cd uptake. • Pb and As are the elements that presented the greatest risk to human health in the case of accidental soil ingestion. [ABSTRACT FROM AUTHOR]

Dark septate endophytes (DSEs) are widely distributed worldwide and can promote plant growth. Therefore, they are considered potentially important plant allies, especially in stressful environments. Previous studies have reported that DSEs cohabit roots with other microorganisms such as ectomycorrhizal (ECM), endophytic and pathogenic fungi/oomycetes. However, interactions between different DSE species have not yet been reported, and studies on the interactions between DSEs and other fungi are scarce. Using a simple and reproducible pairwise growth assay in vitro , we studied the synergistic/antagonistic interactions between eight DSEs, two ECM fungi and three root pathogens. Most of the DSE/DSE outcomes were neutral. Interestingly, we identified several DSE strains acting in synergy with other strains, as well as strains that could potentially act as biocontrol agents. Notably, three metal-tolerant DSE strains, namely, Cadophora sp. Leptodontidium sp. and Phialophora mustea , could decrease the growth of the root phytopathogens Pythium intermedium , Phytophthora citricola and Heterobasidion annosum. The present data are discussed in the general context of the use of fungal consortia as inocula in the tree-based phytomanagement of marginal lands. [ABSTRACT FROM AUTHOR]

• The present study aims to establish a flora inventory of a red gypsum technosol. • The site was characterized by a remarkably low availability of some nutrients. • A spontaneous tree succession has been established, dominated by Betula pendula. • This study aided the implementation of a revegetation strategy at the landfill. Red gypsum is the product of the neutralization of titanium dioxide (TiO 2) extraction residue from ilmenite and anatase. The disposal of red gypsum creates heterogeneous plots with layers that may include Fe, Ca, Al, Mg, Mn, S, and other elements and an alkaline pH that makes revegetation complicated and slow. The vertical and horizontal dispersion of the sediment particles are the main concern. Therefore, the establishment of precise vegetation cover is needed to address this issue. One of the aims of this study was (1) to explore the distribution of the spontaneous vegetation found along a red gypsum-formed landfill located at the Ochsenfeld site in eastern France. Additionally, (2) some pedological parameters were also studied to determine the most significant red gypsum chemical drivers influencing the occurrence and abundance of the vegetation within the site. The Braun-Blanquet scale was used to rate the species presence in the field contained in the spontaneous vegetation dataset. The vegetation survey revealed the presence of 59 species from 23 families. The most abundant species was Betula pendula, and a further cluster analysis enabled the differentiation of areas with this species. The CaCl 2 extractable concentrations of the nutrients and trace elements, as well as the pH and the organic matter (OM) present in the sampled substrate, were used to form the pedological parameters dataset. A multiple factor analysis (MFA) was performed to link the large datasets together and revealed 3 groups of plants. Group 1 was composed of pH-tolerant species such as B. pendula and S. caprea. Group 2 was formed by Cr-Zn-tolerant species, including Echium vulgare and R. pseudoacacia. Finally, group 3 was characterized by species such as Clematis vitalba and Artemisia vulgaris that tolerate the presence of Na. The MFA revealed a correlation between the Betula pendula distribution and the pH, CaCl 2 extractable P concentration and organic matter. On the other hand, A lack of relation of the CaCl 2 extractable concentrations of Fe, Mn, Na, Si and K were also found. This study aided in the selection of an adapted candidate for the implementation of the revegetation strategy of a red gypsum landfill in eastern France. Further tests were performed at the site using white birch for Mn accumulation and topsoil stabilization in situ. [ABSTRACT FROM AUTHOR]

Industrial waste dumps are rarely colonized by vegetation after they have been abandoned, indicating biological infertility. Revegetation of industrial tailings dumps is thus necessary to prevent wind erosion, metal leaching and has been shown to restore soil functions and ecosystem services. However, little is known about the microbial colonization and community structure of vegetated tailings following the application of restoration technologies. In this study, we investigated the rhizosphere and phyllosphere bacterial communities of a poplar tree plantation within a phytomanagement-based restoration program of a Hg-contaminated site. We used Illumina-based sequencing combined with culture-dependent approaches to describe plant-associated bacterial communities and to isolate growth-promoting bacteria (PGPB) and Hg-resistant bacteria. The genus Streptomyces was highly specific to the root community, accounting for 24.4% of the relative abundance but only representing 0.8% of the soil community, whereas OTUs from the Chloroflexi phylum were essentially detected in the soil community. Aboveground habitats were dominated by bacteria from the Deinococcus-Thermus phylum, which were not detected in belowground habitats. Leaf and stem habitats were characterized by several dominant OTUs, such as those from the phylum Firmicutes in the stems or from the genera Methylobacterium , Kineococcus , Sphingomonas and Hymenobacter in the leaves. Belowground habitats hosted more cultivable Hg-resistant bacteria than aboveground habitats and more Hg-resistant bacteria were found on the episphere than in endospheric habitats. Hg-resistant isolates exhibiting plant growth-promoting (PGP) traits, when used as inoculants of Capsicum annuum , were shown to increase its root dry biomass but not Hg concentration. The N 2 -fixing and Hg-resistant species Pseudomonas graminis , observed in the poplar phyllosphere, may be a key microorganism for the restoration of industrial tailings dumps. [ABSTRACT FROM AUTHOR]

Fungal root endophytes, including the common group of dark septate endophytes (DSEs), represent different taxonomic groups and potentially diverse life strategies. In this study, we investigated two unidentified helotialean lineages found previously in a study of DSE fungi of semiarid grasslands, from several other sites, and collected recently from a pezizalean truffle ascoma and eggs of the cereal cyst nematode Heterodera filipjevi. The taxonomic positions and phylogenetic relationships of 21 isolates with different hosts and geographic origins were studied in detail. Four loci, namely, nuc rDNA ITS1-5.8S-ITS2 (internal transcribed spacer [ITS]), partial 28S nuc rDNA (28S), partial 18S nuc rDNA (18S), and partial RNA polymerase II second-largest subunit (RPB2), were amplified and sequenced for molecular phylogenetic analyses. Analyses of similar ITS sequences from public databases revealed two globally distributed lineages detected in several biomes from different geographic regions. The host interaction of isolates from nematodes was examined using in vitro bioassays, which revealed that the fungi could penetrate nematode cysts and colonize eggs of H. filipjevi, confirming observations from field-collected samples. This is the first report of a DSE, and we are not aware of other helotialean fungal species colonizing the eggs of a plant-parasitic nematode. Neither conidiomata and conidia nor ascomata formation was detected in any of the isolates. Based on molecular phylogenetic analyses, these isolates represent a distinct lineage within the Helotiales in the Hyaloscyphaceae. For this lineage, we propose here the new genus Polyphilus represented by two new species, P. sieberi and P. frankenii. [ABSTRACT FROM AUTHOR]

Phytotechnologies are a set of sustainable, ecological options notably for alleviating pollutant linkages induced by contaminated soils. However, concerns exist regarding the processing of trace elements (TE)-enriched biomass and the fate of TEs in the end-products. The fractionation of phytoremediation TE-enriched non-woody lignocellulosic (tobacco) and woody (birch, willow) phytoremediation-borne biomasses was studied using ethanol organosolv, soda and dilute acid pretreatments. TE distribution in the process fractions (pulp, liquid effluents and lignin) was further examined. In dilute acid conditions, a wood pretreatment performed at 170 °C in the presence of 2% w/w of sulfuric acid allowed an efficient extraction of the metals in the water effluent (≈90% for Mn and Zn) producing a clean pulp. A soda pretreatment resulted in a low metal extractability, especially at high temperature. At 170 °C or above with 15% w/w of NaOH, metals were mostly recovered in the cellulosic pulp (70%- 98%). Using organosolv pulping, the TE contents were in the decreasing order: pulp ≫ water stream > lignin. The TE organosolv extraction in the liquid phase varied depending on the TE metal and on the species but was generally low. Metal extractability increased with the water content in the solvent of the organosolv pulping but decreased with temperature. Enzymatic hydrolyses of TE-enriched and metal-free pulps were investigated and it was concluded that the TE concentrations had little or no effect on polysaccharide enzymatic hydrolysability by cellulases. The final destination of the various fractions for valorization in a biorefinery setting is discussed, regarding their TE content. [ABSTRACT FROM AUTHOR]

Afforestation of trace element (TE)-contaminated soil, notably with fast growing trees producing large biomass has been demonstrated to be an attractive option for their bioremediation. Mycorrhizal fungi can form symbiotic associations with plants, contributing to TE tolerance and participating actively in bioremediation processes. We studied the effects of mycorrhizal inoculation on the growth of two poplar clones (Skado and I214), to large-scale. Two TE-contaminated sites of ca . 1 ha (Pierrelaye and Fresnes-sur-Escaut, France) were planted with 2200 trees, and were either inoculated with a mixed commercial inoculum or not-inoculated and allometric parameters were determined after 2 and 4 years of growth. The height diameter relationships remained linear overtime, although the second period of the experiment has been more favorable to growth of the Skado clone and its survival rates were higher compared than those of the I214 clone, at both sites. The inoculation with mycorrhizal significantly impacted the biomass production of the Skado clone at both sites, despite striking differences in soil structure and contamination. In overall, this bioaugmentation option with mycorrhizal fungi influenced more poplar growth than soil contamination and highly improved its biomass production. [ABSTRACT FROM AUTHOR]

Chlorinated ethenes (CE) are among the most common volatile organic compounds (VOC) that contaminate groundwater, currently representing a major source of pollution worldwide. Phytoscreening has been developed and employed through different applications at numerous sites, where it was generally useful for detection of subsurface chlorinated solvents. We aimed at delineating subsurface CE contamination at a chlor-alkali facility using tree core data that we compared with soil data. For this investigation a total of 170 trees from experimental zones was sampled and analyzed for perchloroethene (PCE) and trichloroethene (TCE) concentrations, measured by solid phase microextraction gas chromatography coupled to mass spectrometry. Within the panel of tree genera sampled, Quercus and Ulmus appeared to be efficient biomonitors of subjacent TCE and PCE contamination, in addition to the well known and widely used Populus and Salix genera. Among the 28 trees located above the dense non-aqueous phase liquid (DNAPL) phase zone, 19 tree cores contained detectable amounts of CE, with concentrations ranging from 3 to 3000 μg L −1 . Our tree core dataset was found to be well related to soil gas sampling results, although the tree coring data were more informative. Our data further emphasized the need for choosing the relevant tree species and sampling periods, as well as taking into consideration the nature of the soil and its heterogeneity. Overall, this low-invasive screening method appeared useful to delineate contaminants at a small-scale site impacted by multiple sources of chlorinated solvents. [ABSTRACT FROM AUTHOR]

Torrefaction (290 °C) and pyrolysis (450 and 800 °C) trials were performed at pilot scale with a patented reactor on metal-enriched poplars from a contaminated soil managed by phytotechnologies and poplars cultivated on uncontaminated soil, for comparison. This study emphasized the influence of temperature on end-product yield, metal distribution in end-products and metal behavior. Results showed that the evolution of the end-product yield, i.e. biochar, bio-oil and gas fractions, was depending on temperature rather than other parameters such as the origin or metal content of the tested poplars. Torrefaction decreased the processed poplars weight, leading to metal-enriched torrefied biomass as a major end-product. At 450 and 800 °C, metal behavior was governed by temperature. Nevertheless, the different chlorine content of initial biomass was hypothesized to be an important factor that could modify the metal behavior by increasing metal volatilization at process temperatures. Amongst the studied metals, Zn and Pb were hypothesized to form volatile metal chlorides, therefore increased metal volatilization from Control poplar biomass could be explained by increased chlorine content of such biomass. At 450 °C, metals were recovered in biochar, then in bio-oil and finally in gases. At 800 °C, similar results were obtained for Cu, confirming that Cu was not easily volatilized. On the contrary, Zn, Pb and Cd were mostly recovered in gases, which became the second metal recovery compartment. According to metal concentrations, valorization options were discussed for end-products. [ABSTRACT FROM AUTHOR]

Past industrial activities have generated many contaminated lands from which Mercury (Hg) escapes, primarily by volatilization. Current phytomanagement techniques aim to limit Hg dispersion by increasing its stabilization in soil. Although soil fungi represent a source of Hg emission associated with biovolatilization mechanisms, there is limited knowledge about how dead fungal residues (i.e., fungal necromass) interact with soil Hg. This study determined the Hg biosorption potential of fungal necromass and the chemical drivers of passive Hg binding with dead mycelia. Fungal necromass was incubated under field conditions with contrasting chemical properties at a well-characterized Hg phytomanagement experimental site in France. After four months of incubation in soil, fungal residues passively accumulated substantial quantities of Hg in their recalcitrant fractions ranging from 400 to 4500 μg Hg/kg. In addition, infrared spectroscopy revealed that lipid compounds explained the amount of Hg biosorption to fungal necromass. Based on these findings, we propose that fungal necromass is likely an important factor in Hg immobilization in soil. [Display omitted] • Fungal necromass accumulates large quantities of Mercury (Hg) in soil. • Hg biosorption depends on the chemical properties of fungal residues. • Lipid acyl chains are positively related to Hg adsorption on fungal necromass. [ABSTRACT FROM AUTHOR]

The aim of the present study is to deepen the current understanding of the microbial communities at two poplar phytomanagement sites to reveal the environmental factors that drive the abundance, diversity and composition of microbial communities. A soil analysis revealed that the two soils displayed contrasting physico-chemical characteristics, with significant lower pH and higher Cd, Zn and Mn CaCl 2 -extractable fractions at Leforest site, compared with Pierrelaye site. The fungal and bacterial community profiles in the poplar roots and soils were assessed through Illumina MiSeq sequencing. Diversity indices and β-diversity measures illustrated that the root microbial communities were well separated from the soil microbial communities at both sites. A detailed study of the fungal composition showed that Ascomycota dominated the overall fungal communities on poplar soil, the root samples at Pierrelaye, and the unplanted soil at the experimental sites. Conversely, Basidiomycota accounted for a much higher percentage of the fungal community in poplar root samples from the Leforest site. The root bacterial communities were dominated by Alphaproteobacteria and Actinobacteria , and the soil samples were dominated by Alphaproteobacteria and Acidobacteria. The occurrence and dominance of the ectomycorrhizal community at Leforest but not at Pierrelaye is the major feature of our data set. Overall, ectomycorrhizal root symbionts appeared to be highly constrained by soil characteristics at the phytomanagement sites. Our data support the view that mycorrhizal inoculation is needed in highly stressed and nutrient-poor environments. [ABSTRACT FROM AUTHOR]

Despite a long history of use in phytomanagement strategies, the impacts of poplar trees on the structure and function of microbial communities that live in the soil remain largely unknown. The current study combined fungal and bacterial community analyses from different management regimes using Illumina-based sequencing with soil analysis. The poplar phytomanagement regimes led to a significant increase in soil fertility and a decreased bioavailability of Zn and Cd, in concert with changes in the microbial communities. The most notable changes in the relative abundance of taxa and operational taxonomic units unsurprisingly indicated that root and soil constitute distinct ecological microbial habitats, as exemplified by the dominance of Laccaria in root samples. The poplar cultivar was also an important driver, explaining 12% and 6% of the variance in the fungal and bacterial data sets, respectively. The overall dominance of saprophytic fungi, e.g. Penicillium canescens, might be related to the decomposition activities needed at the experimental site. Our data further highlighted that the mycorrhizal colonization of poplar cultivars varies greatly between the species and genotypes, which is exemplified by the dominance of Scleroderma under Vesten samples. Further interactions between fungal and bacterial functional groups stressed the potential of high-throughput sequencing technologies in uncovering the microbial ecology of disturbed environments. [ABSTRACT FROM AUTHOR]

Numerous studies address the distribution and the diversity of dark septate endophytes (DSEs) in the literature, but little is known about their ecological role and their effect on host plants, especially in metal-polluted soils. Seven DSE strains belonging to Cadophora, Leptodontidium, Phialophora and Phialocephala were isolated from roots of poplar trees from metal-polluted sites. All strains developed on a wide range of carbohydrates, including cell-wall-related compounds. The strains evenly colonized birch, eucalyptus and ryegrass roots in re-synthesis experiments. Root and shoot growth promotion was observed and was both plant and strain dependent. Two Phialophora and Leptodontidium strains particularly improved plant growth. However, there was no correlation between the level of root colonization by DSEs and the intensity of growth promotion. All strains produced auxin and six also stimulated plant growth through the release of volatile organic compounds (VOCs). SPME-GC/MS analyses revealed four major VOCs emitted by Cadophora and Leptodontidium. The strains exhibited growth at high concentrations of several metals. The ability of metal-resistant DSE strains to produce both soluble and volatile compounds for plant growth promotion indicates interesting microbial resources with high potential to support sustainable production of bioenergy crops within the context of the phytomanagement of metal-contaminated sites. [ABSTRACT FROM AUTHOR]

Revegetation of industrial landfills and mine tailing may restore key soil functions and reduce the environmental impacts of contaminants. These marginal sites are often characterized by phytotoxic levels of trace elements (TE) (Cu, Fe, Mn, and Zn) and low nutrient status (N, P, and K). The aim of this study was to test the effect of digestate and bacterial inoculation on soil physicochemical properties (pH, CaCl 2 extractable Mn, and microbial enzyme activities) and birch (Betula pendula) growth and physiology on a red gypsum substrate in a lab-to-field experimental approach. The biomass of birches amended with digestate (D0.05% N) was on average 2- and 6-fold greater than that of control birch in the laboratory and field experiments, respectively. A higher concentration of digestate (0.1% N) had an inhibitory effect on plant growth, and reduced the survival rates of amended plants by 40% as compared with controls. The digestate (D0.05% N) treatment significantly increased leaf P and K contents while decreasing leaf Ca, Fe and Mn contents. Digestate also increased some key soil enzyme activities of C, N, P and S metabolism by >10-fold compared with the control soil. In a phytomanagement scenario, digestate would be a preferred amendment resource for the production of clean birch leaf biomass on contaminated red gypsum landfill, as birch trees amended with digestate had lower leaf TE and higher leaf nutrient contents than control birches. [Display omitted] • Digestate and bacterial inoculum were used to improve birch growth on red gypsum. • The digestate significantly increased birch biomass as well as leaf P and K content. • The two amendments decreased the leaf Fe, Mn and Zn contents. • Soil functionalities were enhanced upon digestate amendments. [ABSTRACT FROM AUTHOR]

Although current Hg emissions from industrial activities may be accurately monitored, evidence of past releases to the atmosphere must rely on one or more environmental proxies. We used Hg concentrations in tree cores collected from poplars and willows to investigate the historical changes of Hg emissions from a dredged sediment landfill and compared them to a nearby control location. Our results demonstrated the potential value of using dendrochemistry to record historical Hg emissions from past industrial activities. [ABSTRACT FROM AUTHOR]

Tailings dumps require mercury stabilization to prevent air pollution by evaporated mercury, which can be achieved through plant covers. Plants are considered a net sink for atmospheric Hg via incorporation into leaf tissues. However, most studies related to Hg uptake by plants have considered plants exposed to only atmospheric Hg, whereas in the case of tailings dumps, plants are potentially exposed to both soil and atmospheric Hg. The goal of this work is to evaluate the relative contributions of root and atmospheric pathways by growing poplar (Populus trichocarpa X Populus maximowiczii/var Skado) cuttings on either control or polluted substrates and under either natural or controlled exposure conditions. We showed that foliar Hg concentrations significantly increased with age, reaching 120 ng g −1 dry mass when poplars were exposed to Hg-contaminated substrate under natural exposure. Remarkably, we did not observe significantly different Hg concentrations in poplar leaves grown on either the control or polluted substrates when cultivated together in growth chambers. Our set of data prompted us to conclude that Hg entry into poplar leaves is exclusively through an atmospheric pathway. Our results are discussed in line with existing literature. [ABSTRACT FROM AUTHOR]

Revegetation of the tailings dumps produced by various industrial activities is necessary to prevent dust storms and erosion and represents a great challenge for ecological restoration. Little is known about the microbial colonisation and community structure of revegetated tailings following site exploitation. Here, we report the sequencing of 16S rRNA and internal transcribed spacer (ITS) fungal RNA gene amplicons from chlor-alkali residue and from an adjacent undisturbed soil to define the composition and assembly of the rhizosphere microbial communities. After quality filtering, a total of 72,373 and 89,929 bacterial sequences and 122,618 and 111,209 fungal sequences remained for community analysis from undisturbed soil and tailings dump samples, respectively. These reads were affiliated with 45 bacterial and 9 fungal phyla and 113 bacterial and 35 fungal classes. We observed a clear dominance of Gammaproteobacteria at our study site (24% of total sequences), especially of the Pseudomonas genera (72% of Gammaproteobacteria sequences), together with the dominance of a few fungal taxa, such as Hebeloma and Geopora. However, we also noticed that the core microbiome comprised 64.4% and 62.4% of the bacterial and fungal genera, respectively, despite marked differences in soil physico-chemical properties. A heatmap of correlations between soil parameters and taxa confirmed that approximately 50% of the 33 dominant taxa colonised both types of soil. We further demonstrated that the global bacterial-fungal network topology of the dump approximated that of the undisturbed soil. Our approach illuminates the importance of studying more than just a single component of the microbial community and represents a step forward in uncovering the microbial ecology of disturbed environments beyond what is generally found in conventional studies. Our study also provides novel global community proxies that have led us to conclude that environmental filtering is more likely to occur through the activity of tree roots rather than as a result of specific soil characteristics and could be an important force in the assembly of at least some microbial communities. [ABSTRACT FROM AUTHOR]

The extractive industry is increasingly faced with problems of managing contaminated sites. The red gypsum landfill at the Ochsenfeld site is representative of the typology byproduct storage of the Ti-extraction activity. The management of the elemental content and the water body are the issues at this site. The aim of this study was to evaluate the canopy conductance (g cmax) of various tree species and the content of elements in the leaves, utilizing the opportunity of a demonstration plantation setup in 2014 with sixteen tree species, combined with a growth chamber experiment. We combined the gas exchange measurements with the data from two multispectral cameras with RGB and NIR bands embarked on an unmanned aerial vehicle (UAV). In the field, Ostrya carpinifolia, Maclura pomifera, and Rhus copallina had the highest g cmax of all planted tree species, and the high transpiration rate in O. carpinifolia was confirmed in a pot-based controlled experiment. Except R. copallina , the species with a high Mn content (O. carpinifolia , Betula pendula , and Salix aquatica grandis) had high stomatal conductance. O. carpinifolia could therefore be a species to exploit in the management of landfill leachates, especially in the context of climate change since this species is well adapted to dry environments. [Display omitted] • Management of landfills utilizing trees for water evaporation and element uptake was tested. • A method to calculate LAI in landfills by UAV 3D imaging was proposed. • The maximal canopy conductance of 16 tree species was derived from g smax and LAI. • Ostrya carpinifolia combined the highest growth, canopy conductance, and Mn uptake. [ABSTRACT FROM AUTHOR]

The rapid development of green energy sources and new medical technologies contributes to the increased exploitation of rare earth elements (REEs). They can be subdivided into light (LREEs) and heavy (HREEs) REEs. Mining, industrial processing, and end-use practices of REEs has led to elevated environmental concentrations and raises concerns about their toxicity to organisms and their impact on ecosystems. REE toxicity has been reported, but its precise underlying molecular effects have not been well described. Here, transcriptomic and proteomic approaches were combined to decipher the molecular responses of the model organism Saccharomyces cerevisiae to La (LREE) and Yb (HREE). Differences were observed between the early and late responses to La and Yb. Several crucial pathways were modulated in response to both REEs, such as oxidative-reduction processes, DNA replication, and carbohydrate metabolism. REE-specific responses involving the cell wall and pheromone signalling pathways were identified, and these responses have not been reported for other metals. REE exposure also modified the expression and abundance of several ion transport systems, with strong discrepancies between La and Yb. These findings are valuable for prioritizing key genes and proteins involved in La and Yb detoxification mechanisms that deserve further characterization to better understand REE environmental and human health toxicity. [Display omitted] • First proteo-transcriptomics analysis revealing yeast molecular response to REEs. • Rare earth elements trigger specific responses. • Yeast cells react differentially to light vs heavy REEs. • Cell wall organization and pheromone signalling pathways are key yeast responses. [ABSTRACT FROM AUTHOR]

Highlights: [•] We use EDXRF to identify trends in high-resolution cation distribution in tree rings. [•] Potassium counts are elevated in sapwood and infected wood. [•] Localized peaks in calcium counts can be associated with crystals in wood. [•] Intra-annual variation in peak counts appears associated with ring boundaries. [ABSTRACT FROM AUTHOR]

Heavy metals are pollutants which affect all organisms. Since a small number of eukaryotes have been investigated with respect to metal resistance, we hypothesize that many genes that control this phenomenon remain to be identified. This was tested by screening soil eukaryotic metatranscriptomes which encompass RNA from organisms belonging to the main eukaryotic phyla. Soil-extracted polyadenylated mRNAs were converted into cDNAs and 35 of them were selected for their ability to rescue the metal ( Cd or Zn) sensitive phenotype of yeast mutants. Few of the genes belonged to families known to confer metal resistance when overexpressed in yeast. Several of them were homologous to genes that had not been studied in the context of metal resistance. For instance, the BOLA ones, which conferred cross metal ( Zn, Co, Cd, Mn) resistance may act by interfering with Fe homeostasis. Other genes, such as those encoding 110- to 130-amino-acid-long, cysteine-rich polypeptides, had no homologues in databases. This study confirms that functional metatranscriptomics represents a powerful approach to address basic biological processes in eukaryotes. The selected genes can be used to probe new pathways involved in metal homeostasis and to manipulate the resistance level of selected organisms. [ABSTRACT FROM AUTHOR]

Tree nutrient research concentrated on endogenous C and N remobilisation in spring has neglected to acknowledge the possibilities of significant effects of N uptake before bud break, especially on the quality of regrowth and N reserve remobilisation. To investigate this subject, experimental studies were performed on young poplars (Populus tremula x Populus alba, clone INRA 717-1B4) grown with a controlled nutrient supply: (i) without N, 'control'; (ii) N supplied throughout the course of the experiment, 'N-supply'; and (iii) N supplied only before bud break, 'N-pulse'. Results confirm the hypothesis that poplar scions can significantly take up nitrate before bud break, amounting to ~34% of the total N stored the previous year. After bud break, emerging leaves restart the sap flow, which increased nitrate uptake to support the regrowth. N-pulse and N-supply treatments were found to have significant effects shortly after a growth period, i.e. by increasing N content of all tissues (e.g. 37 and 81% in new shoots respectively), leaf area (18 and 29%) and specific leaf area (20 and 35%). Therefore, results confirm the hypothesis that early N supply plays a significant role in the N status and N remobilisation involved in the spring regrowth of young trees. Young poplars (Populus tremula L. x Populus alba L.) were found to take up nitrate before bud break, which lead quickly to significant changes on regrowth and N partitioning of sinks just after bud break. The N uptake increased the quality of new shoots. The uptake of N by the poplar scions before bud break amounted to approximately a third of the N storage of the previous year. After bud break, emerging leaves restarted the sap flow, which increased nitrate uptake to support the regrowth. These results show that early N supply plays a significant role in the N status and N remobilisation involved in the spring re-growth of young trees. Our study applies to tree nurseries where growth of young trees may be stimulated by the addition of fertilizers just before bud break and during spring regrowth, rather than applying fertilizers in autumn. [ABSTRACT FROM AUTHOR]

Abstract: Two full-length cDNAs (OmZnT1 and OmFET) encoding membrane transporters were identified by yeast functional screening in the heavy metal tolerant ericoid mycorrhizal isolate Oidiodendron maius Zn. OmZnT1 belongs to the Zn-Type subfamily of the cation diffusion facilitators, whereas OmFET belongs to the family of iron permeases. Their properties were investigated in yeast by functional complementation of mutants affected in metal uptake and metal tolerance. Heterologous expression of OmZnT1 and OmFET in a Zn-sensitive yeast mutant restored the wild-type phenotype. Additionally, OmZnT1 expression also restored cobalt tolerance in a Co-sensitive mutant. A GFP fusion protein revealed that OmZnT1 was targeted to the endoplasmic reticulum membrane, a result consistent with a function for OmZnT1 in metal sequestration. Similarly to other iron permeases, OmFET-GFP was localized on the plasma membrane. OmFET restored the growth of uptake-defective strains for iron and zinc. Zinc-sensitive yeast mutants expressing OmFET specifically accumulated magnesium, as compared to cells transformed with the empty vector. We suggest that OmFET may counteract zinc toxicity by increasing entry of magnesium into the cell. [Copyright &y& Elsevier]

Trees can take up and assimilate contaminants from the soil, subsurface, and groundwater. Contaminants in the transpiration stream can become bound or incorporated into the annual rings formed in trees of the temperate zones. The chemical analysis of precisely dated tree rings, called dendrochemistry, can be used to interpret past plant interactions with contaminants. This investigation demonstrates that dendrochemistry can be used to generate historical scenarios of past contamination of groundwater by chlorinated solvents at a site in Verl, Germany. Increment cores from trees at the Verl site were collected and analyzed by energy-dispersive X-ray fluorescence (EDXRF) line scanning. The EDXRF profiles showed four to six time periods where tree rings had anomalously high concentrations of chlorine (Cl) as an indicator of potential contamination by chlorinated solvents. [ABSTRACT FROM AUTHOR]

Using the nutrient film technique, we screened 21 clones of poplar for growth in the presence of a mix of trace elements (TE) and for TE accumulation capacities. Poplar cuttings were exposed for four weeks to a multipollution solution consisting in 10 μM Cd, Cu, Ni, and Pb, and 200 μM Zn. Plant biomass and TE accumulation patterns in leaves varied greatly between clones. The highest Cd and Zn concentrations in leaves were detected in P. trichocarpa and P. trichocarpa hybrids, with the clone Skado (P. trichocarpa x P. maximowiczii) accumulating up to 108 mg Cd kg−1 DW and 1510 mg Zn kg−1 DW when exposed to a multipollution context. Our data also confirm the importance of pH and multipollution, as these factors greatly affect TE accumulation in above ground biomass. The NFT technique applied here to a large range of poplar clones also revealed the potential of the Rochester, AFO662 and AFO678 poplar clones for use in phytostabilization programs and bioenergy production, where production of less contaminated above ground biomass is suitable. [ABSTRACT FROM PUBLISHER]

Gene networks involved in inorganic phosphate (Pi) acquisition and homeostasis in woody perennial species able to form mycorrhizal symbioses are poorly known. Here, we describe the features of the 12 genes coding for Pi transporters of the Pht1 family in poplar (Populus trichocarpa). Individual Pht1 transporters play distinct roles in acquiring and translocating Pi in different tissues of mycorrhizal and nonmycorrhizal poplar during different growth conditions and developmental stages. Pi starvation triggered the up-regulation of most members of the Pht1 family, especially PtPT9 and PtPT11. PtPT9 and PtPT12 showed a striking up-regulation in ectomycorrhizas and endomycorrhizas, whereas PtPT1 and PtPT11 were strongly down-regulated. PtPT10 transcripts were highly abundant in arbuscular mycorrhiza (AM) roots only. PtPT8 and PtPT10 are phylogenetically associated to the AM-inducible Pht1 subfamily I. The analysis of promoter sequences revealed conserved motifs similar to other AM-inducible orthologs in PtPT10 only. To gain more insight into gene regulatory mechanisms governing the AM symbiosis in woody plant species, the activation of the poplar PtPT10 promoter was investigated and detected in AM of potato (Sohmum tuberosum) roots. These results indicated that the regulation of AM-inducible Pi transporter genes is conserved between perennial woody and herbaceous plant species. Moreover, poplar has developed an alternative Pi uptake pathway distinct from AM plants, allowing ectomycorrhizal poplar to recruit PtPT9 and PtPT12 to cope with limiting Pi concentrations in forest soils. [ABSTRACT FROM AUTHOR]

Summary Genome-wide analysis of fungal manganese transporters was undertaken, making use of whole genome sequences available in fungal databases. A repertoire of 281 putative manganese transporters was found in total across 26 fungal species representing 20 fungal orders. The process of gene duplication was apparently accompanied by gene loss events, and this resulted in a great variety of manganese transporters that can be observed in the genome of modern fungi. Eleven transporters belonging to gene families in which manganese transporters have been found were identified in the Phanerochaete chrysosporium genome. This whole set of transporters may cover the need of P. chrysosporium cells for manganese loading in and unloading out of the cytosol, thereby insuring manganese homeostasis. The tight control of intracellular Mn2+ ion concentration is for instance of crucial importance for the control of lignin-degradative systems by saprotrophic fungi, and thereof the carbon cycle in forest ecosystems. [ABSTRACT FROM AUTHOR]

Background and Aims: Nitrogen (N) availability in the forest soil is extremely low and N economy has a special importance in woody plants that are able to cope with seasonal periods of growth and development over many years. Here we report on the analysis of amino acid pools and expression of key genes in the perennial species Populus trichocarpa during autumn senescence. [ABSTRACT FROM PUBLISHER]

Amino acids are the currency of nitrogen exchange between source and sink tissues in plants and constitute a major source of the components used for cellular growth and differentiation. The characterization of a new amino acid transporter belonging to the amino acid permease (AAP) family, AAP11, expressed in the perennial species Populus trichocarpa is reported here. PtAAP11 expression analysis was performed by semi-quantitative RT-PCR and GUS activity after poplar transformation. PtAAP11 function was studied in detail by heterologous expression in yeast. The poplar genome contains 14 putative AAPs which is quite similar to other species analysed except Arabidopsis. PtAAP11 was mostly expressed in differentiating xylem cells in different organs. Functional characterization demonstrated that PtAAP11 was a high affinity amino acid transporter, more particularly for proline. Compared with other plant amino acid transporters, PtAAP11 represents a novel high-affinity system for proline. Thus, the functional characterization and expression studies suggest that PtAAP11 may play a major role in xylogenesis by providing proline required for xylem cell wall proteins. The present study provides important information highlighting the role of a specific amino acid transporter in xylogenesis in poplar. [ABSTRACT FROM PUBLISHER]