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. In the present study, we combined transcriptomic, microscopy, whole plant physiology, X-ray fluorescence mapping, 32 P labeling and fungal genetic approaches to unravel the role of HcPT2, a fungal Pi transporter, during the Hebeloma cylindrosporum-Pinus pinaster ectomycorrhizal association. We localized HcPT2 in the extra-radical hyphae and the Hartig net and demonstrated its determinant role for both the establishment of ectomycorrhizas and Pi allocation towards P. pinaster. We showed that the host plant induces HcPT2 expression and that the artificial overexpression of HcPT2 is sufficient to significantly enhance Pi export towards the central cylinder. Together, our results reveal that HcPT2 plays an important role in ectomycorrhizal symbiosis, affecting both Pi influx in the mycelium and efflux towards roots under the control of P. pinaster.

Spectroscopic characterization of the complexes between Fe/Mn and natural organic matters by electron paramagnetic resonance and synchrotron-based techniques.

The surface interaction between heavy metals and natural organic matters (NOM) substantially affects their migration and conversion in natural environments. In this study, the chemical speciation and element mapping of Fe and Mn in reduced NOM were investigated. The results show that quinone and semiquinone moieties dominated the redox properties in NOM, and the EPR signal intensity exhibited pH dependence with an increase of EPR signal intensity at a higher pH value. The EPR results indicate that the complexes displayed the characteristics of superparamagnetic oxides/oxyhydroxides after Fe/Mn complexed with NOM. µ-XRF results suggest that the scatterplots of Fe and Mn distributions at pH 11 had the most positive linearly-related plot points, indicating strong correlations for Mn-Fe binary metallic ions. µ-XANES results further interpret the presence of higher Mn oxidation state at pH 11, while Fe kept trivalent in all samples. These results reveal that the surface interactions are closely related to the redox state of NOM and are beneficial for better understanding the speciation, immobilization, transport, and toxicity of metal ions in natural waters.

Do selenium hyperaccumulators affect selenium speciation in neighboring plants and soil? An X-Ray Microprobe Analysis.

Neighbors of Se hyperaccumulators Stanleya pinnata and Astragalus bisulcatus were found earlier to have elevated Se levels. Here we investigate whether Se hyperaccumulators affect Se localization and speciation in surrounding soil and neighboring plants. X-ray fluorescence mapping and X-ray absorption near-edge structure spectroscopy were used to analyze Se localization and speciation in leaves of Artemisia ludoviciana, Symphyotrichum ericoides and Chenopodium album growing next to Se hyperaccumulators or non-accumulators at a seleniferous site. Regardless of neighbors, A. ludoviciana, S. ericoides and C. album accumulated predominantly (73-92%) reduced selenocompounds with XANES spectra similar to the C-Se-C compounds selenomethionine and methyl-selenocysteine. Preliminary data indicate that the largest Se fraction (65-75%), both in soil next to hyperaccumulator S. pinnata and next to nonaccumulator species was reduced Se with spectra similar to C-Se-C standards. These same C-Se-C forms are found in hyperaccumulators. Thus, hyperaccumulator litter may be a source of organic soil Se, but soil microorganisms may also contribute. These findings are relevant for phytoremediation and biofortification since organic Se is more readily accumulated by plants, and more effective for dietary Se supplementation.

Detection of posteriorly located breast tumors using gold nanoparticles: a breast-mimicking phantom study.

BACKGROUND: Accurately depicting breast tumors located posteriorly, close to the chest wall musculature, with conventional mammography is a technical challenge. OBJECTIVE: This study demonstrates the proof of concept of an x-ray fluorescence mapping (XFM) technique to address this issue. METHODS: A tissue-equivalent gel phantom is designed to mimic structures in the central part of a compressed breast. The posterior aspect of the breast and adjacent pectoralis major muscle are represented by another 10-mm-thickness breast tissue simulation phantom (BR12) that is attached to the back of the gel phantom as a region of interest (ROI). Two gold nanoparticle (GNP) solutions are embedded into the ROI to simulate varying GNP uptake within breast lesions. The ROI is imaged through performing the XFM technique with an x-ray pencil-beam and a single spectrometer. RESULTS: A 2D mapping of the middle plane in the ROI demonstrates feasibility and matches well the known spatial distribution and different GNP concentrations. 3D reconstruction of the ROI is easily rendered by repeating the 2D mapping process. CONCLUSION: XFM system geometry and its insensitivity to attenuation coefficients of breast tissue components are unique characteristics that may complement conventional mammography and improve the detection of breast cancers located posteriorly, adjacent to or overlying the chest wall musculature.

Synergistic effects of zinc and cadmium on phytoremediation potential of Christmas moss (Vesicularia montagnei).

The hyperaccumulation potential of zinc (Zn) and cadmium (Cd) and their synergistic effects were examined in relation to Christmas moss (Vesicularia montagnei (Bél) Broth., Hypnaceae), an aquatic and terrestrial moss, dosed with Cd (Cd1 and Cd2), Zn (Zn1 and Zn2) and combined Zn and Cd (Cd1Zn1 and Cd2Zn2). Zinc promoted plant growth and development, particularly in the highest Zn and combined Zn/Cd treatments (Zn2 and Cd2Zn2). The Zn treatment resulted in substantial moss chlorophyll content and highest percentage relative growth rate in biomass value (0.23 mg L-1 and 106.8%, respectively); however, the Cd2Zn2 treatment achieved maximal production of chlorophyll a and total chlorophyll (0.29 and 0.51 mg L-1, respectively) due to synergistic effects. These findings suggest that Christmas moss is a highly metal-tolerant and adaptable bryophyte species. Zinc was essential for reducing the detrimental effects of Cd while simultaneously promoting moss growth and biomass development. Furthermore, Christmas moss exhibited hyperaccumulation potential for Cd and Zn in the Cd2Zn2 and Zn alone treatments, as evidenced by highest Cd and Zn values in gametophores (1002 and 18,596 mg per colony volume, respectively). Using energy dispersive X-ray fluorescence (EDXRF) spectrometry, atomic percentages of element concentrations in moss gametophores in the Zn2, Cd2 and combined Zn/Cd treatments were generally in the order: K > Ca > P > Zn > Cd. When comparing the atomic percentages of Zn and Cd in gametophores, it is likely that the higher atomic percentage of Zn was because this element is essential for plant growth and development.

Characterization of Materials Used as Face Coverings for Respiratory Protection.

Use of masks is a primary tool to prevent the spread of the novel COVID-19 virus resulting from unintentional close contact with infected individuals. However, detailed characterization of the chemical properties and physical structure of common mask materials is lacking in the current literature. In this study, a series of commercial masks and potential mask materials, including 3M Particulate Respirator 8210 N95, a material provided by Oak Ridge National Laboratory Carbon Fiber Technology Facility (ORNL/CFTF), and a Filti Face Mask Material, were characterized by a suite of techniques, including scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Wetting properties of the mask materials were quantified by measurements of contact angle with a saliva substitute. Mask pass-through experiments were performed using a dispersed metal oxide nanoparticle suspension to model the SARS-CoV-2 virus, with quantification via spatially resolved X-ray fluorescence mapping. Notably, all mask materials tested provided a strong barrier against respiratory droplet breakthrough. The comparisons and characterizations provided in this study provide useful information when evaluating mask materials for respiratory protection.

Developing a system for in vivo imaging of maize roots containing iodinated contrast media in soil using synchrotron XCT and XRF.

AIMS: We sought to develop a novel experimental system which enabled application of iodinated contrast media to in vivo plant roots intact in soil and was compatible with time-resolved synchrotron X-ray computed tomography imaging. The system was developed to overcome issues of low contrast to noise within X-ray computed tomography images of plant roots and soil environments, the latter of which can complicate image processing and result in the loss of anatomical information. METHODS: To demonstrate the efficacy of the system we employ the novel use of both synchrotron X-ray computed tomography and synchrotron X-ray fluorescence mapping to capture the translocation of the contrast media through root vasculature into the leaves. RESULTS: With the application of contrast media we identify fluid flow in root vasculature and visualise anatomical features, which are otherwise often only observable in ex vivo microscopy, including: the xylem, metaxylem, pith, fibres in aerenchyma and leaf venation. We are also able to observe interactions between aerenchyma cross sectional area and solute transport in the root vasculature with depth. CONCLUSIONS: Our novel system was capable of successfully delivering sufficient contrast media into root and leaf tissues such that anatomical features could be visualised and internal fluid transport observed. We propose that our system could be used in future to study internal plant transport mechanisms and parameterise models for fluid flow in plants. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11104-020-04784-x.

Nanoparticle Size and Coating Chemistry Control Foliar Uptake Pathways, Translocation, and Leaf-to-Rhizosphere Transport in Wheat.

Nanoenabled foliar-applied agrochemicals can potentially be safer and more efficient than conventional products. However, limited understanding about how nanoparticle properties influence their interactions with plant leaves, uptake, translocation through the mesophyll to the vasculature, and transport to the rest of the plant prevents rational design. This study used a combination of Au quantification and spatial analysis to investigate how size (3, 10, or 50 nm) and coating chemistry (PVP versus citrate) of gold nanoparticles (AuNPs) influence these processes. Following wheat foliar exposure to AuNPs suspensions (∼280 ng per plant), adhesion on the leaf surface was increased for smaller sizes, and PVP-AuNPs compared to citrate-AuNPs. After 2 weeks, there was incomplete uptake of citrate-AuNPs with some AuNPs remaining on the outside of the cuticle layer. However, the fraction of citrate-AuNPs that had entered the leaf was translocated efficiently to the plant vasculature. In contrast, for similar sizes, virtually all of the PVP-AuNPs crossed the cuticle layer after 2 weeks, but its transport through the mesophyll cells was lower. As a consequence of PVP-AuNP accumulation in the leaf mesophyll, wheat photosynthesis was impaired. Regardless of their coating and sizes, the majority of the transported AuNPs accumulated in younger shoots (10-30%) and in roots (10-25%), and 5-15% of the NPs <50 nm were exuded into the rhizosphere soil. A greater fraction of larger sizes AuNPs (presenting lower ζ potentials) was transported to the roots. The key hypotheses about the NPs physical-chemical and plant physiology parameters that may matter to predict leaf-to-rhizosphere transport are also discussed.

Multi-analytical methodology to diagnose the environmental impact suffered by building materials in coastal areas.

This work is focused on the development of an innovative multi-analytical methodology to estimate the impact suffered by building materials in coastal environments. With the aim of improving the in situ spectroscopic assessment, which is often based on XRF and Raman spectrometers, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was implemented in the diagnosis study. In this way, the additional benefits from DRIFT were compared to the usual in situ analyses of building materials, which often have interferences from fluorescence and reststrahlen effects. The studies were extended to the laboratory scale by µ-X-ray fluorescence (µ-XRF) cross-section mapping and ion chromatography (IC), and the IC quantitative data were employed to develop thermodynamic models using the ECOS-RUNSALT program, with the aim of rationalizing the behavior of soluble salts with variations in the temperature and the relative humidity (RH). The multi-analytical methodology allowed identification of the most significant weathering agents and classification of the severity of degradation according to the salt content. The suitability of a DRIFT portable device to analyze these types of matrices was verified. Although the Kramers-Kronig algorithm correction proved to be inadequate to decrease the expected spectral distortions, the assignment was successfully performed based on the secondary bands and intensification of the overtones and decreased the time needed for in situ data collection. In addition, the pollutants' distribution in the samples and the possible presence of dangerous compounds, which were not detected during the in situ analysis campaigns, provided valuable information to clarify weathering phenomena.

Laminar gypsum crust on lede stone: Microspatial characterization and laboratory acid weathering.

Gypsum crusts are typical decay forms on limestone in polluted urban environments. Their origin and relation to the stone facies have been thoroughly investigated in the past three decades. Here, we present the combined use of novel techniques for a microspatial structural, chemical and mechanical characterization of a laminar black gypsum crust on a sandy limestone. These techniques include i.a. X-ray computed microtomography, X-ray Fluorescence micromapping, permeability mapping and the scratch test. They reveal the typical architecture of a laminar gypsum crust, with an outer opaque layer, a subsurface gypsum crystallization layer and a deeper cracked zone passing irregularly into the sound stone. Gypsum crystallization is mostly restricted to an irregular outer zone with an average thickness of 500µm, while cracks are found deeper within the rock. These cracks decrease the rock strength to more than 27.5mm below the surface. Because of their surface parallel orientation and thickness of >10-100µm, they create the potential for surface scaling. This is shown by a laboratory acid test where the crack network extensively developed due to further exposure to an SO2 environment. The use of novel techniques opens potential for the study of different decay forms and can be used for stone diagnosis with regards to conservation studies.

Bovine and equine peritubular and intertubular dentin.

Dentin contains 1-2µm diameter tubules extending from the pulp cavity to near the junction with enamel. Peritubular dentin (PTD) borders the tubule lumens and is surrounded by intertubular dentin (ITD). Differences in PTD and ITD composition and microstructure remain poorly understood. Here, a (∼200nm)(2), 10.1keV synchrotron X-ray beam maps X-ray fluorescence and X-ray diffraction simultaneously around tubules in 15-30µm thick bovine and equine specimens. Increased Ca fluorescence surrounding tubule lumens confirms that PTD is present, and the relative intensities in PTD and ITD correspond to carbonated apatite (cAp) volume fraction of ∼0.8 in PTD vs. 0.65 assumed for ITD. In the PTD near the lumen edges, Zn intensity is strongly peaked, corresponding to a Zn content of ∼0.9mgg(-1) for an assumed concentration of ∼0.4mgg(-1) for ITD. In the equine specimen, the Zn K-edge position indicates that Zn(2+) is present, similar to bovine dentin (Deymier-Black et al., 2013), and the above edge structure is consistent with spectra from macromolecules related to biomineralization. Transmission X-ray diffraction shows only cAp, and the 00.2 diffraction peak (Miller-Bravais indices) width is constant from ITD to the lumen edge. The cAp 00.2 average preferred orientation is axisymmetric (about the tubule axis) in both bovine and equine dentin, and the axisymmetric preferred orientation continues from ITD through the PTD to the tubule lumen. These data indicate that cAp structure does not vary from PTD to ITD.

Crystallographic texture and elemental composition mapped in bovine root dentin at the 200 nm level.

The relationship between the mineralization of peritubular dentin (PTD) and intertubular dentin (ITD) is not well understood. Tubules are quite small, diameter ∼2 µm, and this makes the near-tubule region of dentin difficult to study. Here, advanced characterization techniques are applied in a novel way to examine what organic or nanostructural signatures may indicate the end of ITD or the beginning of PTD mineralization. X-ray fluorescence intensity (Ca, P, and Zn) and X-ray diffraction patterns from carbonated apatite (cAp) were mapped around dentintubules at resolutions ten times smaller than the feature size (200 nm pixels), representing a 36% increase in resolution over earlier work. In the near tubule volumes of near-pulp, root dentin, Zn intensity was higher than in ITD remote from the tubules. This increase in Zn(2+), as determined by X-ray absorption near edge structure analysis, may indicate the presence of metalloenzymes or transcription factors important to ITD or PTD mineralization. The profiles of the cAp 00.2 X-ray diffraction rings were fitted with a pseudo-Voigt function, and the spatial and azimuthal distribution of these rings' integrated intensities indicated that the cAp platelets were arranged with their c-axes aligned tangential to the edge of the tubule lumen. This texture was continuous throughout the dentin indicating a lack of structural difference between in the Zn rich near-tubular region and the remote ITD.