Carlos Alberto Perez

Rice (Oryza sativa L.) is a staple food for half of the world’s population but lacks essential nutrients such as iron (Fe), contributing to widespread human Fe deficiency. The vacuolar Fe transporters OsVIT1 and OsVIT2 limit Fe translocation to grains by sequestering Fe in vacuoles of vegetative tissues, and single mutants of either gene show elevated grain Fe levels. Rice is cultivated in flooded soils, where soluble Fe²+ accumulates to toxic levels, raising the question of whether OsVIT1 and OsVIT2 also contribute to Fe detoxification. To investigate this, we generated osvit1osvit2 double mutants and assessed their impact on grain Fe accumulation and Fe excess tolerance. The double mutants had increased Fe concentrations in brown rice, particularly in the scutellum and plumule, indicating a role for OsVITs in determining spatial Fe distribution within the embryo. Root uptake contributed to higher Fe concentrations in grains, whereas Fe translocation from flag leaves was less important. Notably, osvit1osvit2 plants were hypersensitive to excess Fe, revealing a trade-off between Fe biofortification and tolerance to Fe excess. These findings highlight the need to consider Fe excess tolerance in biofortification strategies using VIT genes, and establish OsVIT1 and OsVIT2 as key components for Fe detoxification.

The efficiency of using chelating agents in combination with hyperaccumulator species for nickel phytoextraction has yielded mixed results thus far. This study evaluated the effects of citric acid application on metal solubility in ultramafic soils and the feasibility of its use for nickel agromining by Berkheya coddii and Bornmuellera emarginata. Four citric acid application doses (0, 20, 40, and 60 mmol kg^–1) were used in a tropical and in a temperate ultramafic soil for 90 days for B. coddii and 45 days for B. emarginata, and pH and metal solubility assessments were conducted after application. Citric acid application increased the solubility of nickel, cobalt, and manganese in the soil by up to 20-fold but negatively impacted the biomass. Berkheya coddii accumulated up to dozens of times more Ni, Co, Cr, Cu, Mn, and Zn in its leaves than did B. emarginata. However, the citric acid did not enhance nickel accumulation in either of the two species. Additionally, citric acid application increased the level of impurities in the bio-ores from the plants. Synchrotron X-ray fluorescence analysis revealed that the tissue-level distribution of metals within the plants, with or without citric acid treatment, highlights manganese toxicity as the most significant limitation for Ni phytoextraction. The results of this study show that the use of citric acid is not an effective strategy for nickel agromining; however, its capacity to mobilize multiple metals suggests potential applicability in phytoremediation of multicontaminated soils.

This study presents the structure of a-SiC thin films on top of chromium microlamps, deposited to be a protection layer against oxidation, as well as their chemical and structural modifications induced by heating during operation. They were formed with materials deposited by plasma-enhanced chemical vapor deposition (PECVD) and sputtering, on silicon substrates. The SOLEIL synchrotron beamline, used in this work, has a microfocus beam, allowing the evaluation of the micro region thermally affected using XANES. The results showed structural changes in the a-SiC protective layer. To improve the studies additional a-SiC thin films, deposited on ordinary large flat substrates, were produced and analyzed by XANES, EXAFS, GIXRF, and RBS. The results revealed the diffusion of Cr and O into the a-SiC. In addition, from a-SiC atomic geometries obtained by ab initio molecular dynamics, it was also simulated the XANES spectra with the finite difference method near ndge structure (FDMNES) code. The conclusion was that the microlamp design induced the growth of a PECVD a-SiC layer far from the best conditions, probably due to the presence of a cavity under the filament, that reduced the substrate temperature during the deposition, enhancing the Cr and O diffusion into the silicon carbide.

Enhancing the initial stages of plant growth by using polymeric gels for seed priming presents a significant challenge. This study aimed to investigate a microgel derived from polyetheramine-poly(propylene oxide) (PPO) and a bisepoxide (referred to as micro-PPO) as a promising alternative to optimize the seed germination process. The micro-PPO integrated with an iron micronutrient showed a positive impact on seed germination compared with control (Fe solutions) in which the root length yield improved up to 39%. Therefore, the element map by synchrotron-based X-ray fluorescence shows that the Fe intensities in the seed primers with the micro-PPO-Fe gel are about 3-fold higher than those in the control group, leading to a gradual distribution of Fe species through most internal embryo tissues. The use of micro-PPO for seed priming underscores their potential for industrial applications due to the nontoxicity results in zebrafish assays and environmentally friendly synthesis of the water-dispersible monomers employed.

Synchrotron X-ray computed tomography (XCT) has been increasingly applied to study the in vivo dynamics of root growth and rhizosphere processes. However, minimizing radiation-induced damage to root growth warrants further investigation. Our objective was to develop a robust approach for modeling and evaluating ways to reduce synchrotron X-ray dose effects on root growth during in vivo imaging. Wheat roots growing in soil were exposed to X-rays during XCT experiments resolved in space (3D) plus time (4D). The dose rate and cumulative absorbed dose in roots were modelled using the Monte Carlo code FLUKA for different experimental conditions of polychromatic and quasi-monochromatic X-ray beam configurations. The most impactful factors affecting damage to roots were incident X-ray energy spectrum, stored current in the accelerator machine, position of the root in the soil, and possibly the number of exposures during the 4D XCT experiments. Our results imply that radiation dose during in vivo imaging of plant roots can be diminished by using monochromatic radiation at the highest energy suitable for a given sample thickness and field of view, and by controlling the rotation axis of off-centered roots to increase attenuation of radiation by the soil matrix.

This study describes the composition and provenance of dense bodies or structures present in uncharred plant vestiges recovered at Monte Castelo (6000–700 cal. AP-SW Amazonia). It aimed to disclose some aspects of this plant remains’ interactions with the sedimentary matrix of the site over the 200 years (at least) since its initial deposit, from the point of view of the soft tissue mineralization processes. Two specimens were examined using XFCT, X-ray MicroCT, and SEM-EDS techniques to reveal the presence and distribution of Ca, K, Mn, Fe, Ti, Si, S, Cu, Br, Rb, Sr, Zn, and Zr. These attributes were integrated with compositional ED-XRF and XRD measured data from the sedimentary substrate. Results show that some of the chemical elements present in solid bodies and anatomical structures of the plant remains refer to the sedimentary environment, while others have an endogenous origin. These include mainly Rb and Br, which were interpreted as the result of degradation processes of the internal tissues, where they are mainly present. Except Sr and Zr, a portion of all the other elements entered and disperse into the sample structures from the sedimentary substrate. Its presence is attributable to mechanisms such as attachment, diffusion and impregnation through the outermost tissues, where they are mostly concentrated. The composition of most of the dense bodies consists of both endogenous and exogenous elements.

Synchrotron scanning X-ray microscopy has been established as a mature technique, bridging the gap between conventional optical microscopy and high-resolution electron microscopy and, notably, adding advantages like large penetration in bulky samples, dose reduction and spectroscopy. The CARNAÚBA beamline at the 4th generation synchrotron source Sirius-LNLS provides an X-ray nanoprobe for simultaneous multi-analytical and coherent X-ray imaging techniques, with spectroscopic capabilities in the 2.05 to 15 keV energy range. The sample is raster-scanned through the nanoprobe to provide two-dimensional maps, which can then be combined with a rotation for computed tomography. In this contribution, some relevant scientific cases for the Day-1 experiments will be presented, along with original instrument solutions for in situ, in operando, cryogenic and in vivo sample environments.

Metastatic disease remains the leading cause of death in cancer and understanding the mechanisms involved in tumor progression continues to be challenging. This work investigates the role of manganese in tumor progression in an in vivo model of tumor growth. Our data revealed that manganese accumulates within primary tumors and secondary organs as manganese-rich niches. Consequences of such phenomenon were investigated, and we verified that short-term changes in manganese alter cell surface molecules syndecan-1 and β1-integrin, enhance collective cell migration and invasive behavior. Long-term increased levels of manganese do not affect cell growth and viability but enhance cell migration. We also observed that manganese is secreted from tumor cells in extracellular vesicles, rather than in soluble form. Finally, we describe exogenous glycosaminoglycans that counteract manganese effects on tumor cell behavior. In conclusion, our analyses describe manganese as a central element in tumor progression by accumulating in Mn-rich niches in vivo, as well as in vitro, affecting migration and extracellular vesicle secretion in vitro. Manganese accumulation in specific regions of the organism may not be a common ground for all cancers, nevertheless, it represents a new aspect of tumor progression that deserves special attention.