16 research outputs found
Behavior of Silene vulgaris (Moench.) Garcke against exposure to chromium. Evaluation of potential use in soil remediation
Tesis Doctoral inĂ©dita leĂda en la Universidad AutĂłnoma de Madrid, Facultad de Ciencias, Departamento de QuĂmica AgrĂcola. Fecha de lectura: 17-07-201
Fungal-associated NO is involved in the regulation of oxidative stress during rehydration in lichen symbiosis
[EN] Background
Reactive oxygen species (ROS) are normally produced in respiratory and photosynthetic electron chains and their production is enhanced during desiccation/rehydration. Nitric oxide (NO) is a ubiquitous and multifaceted molecule involved in cell signaling and abiotic stress. Lichens are poikilohydrous organisms that can survive continuous cycles of desiccation and rehydration. Although the production of ROS and NO was recently demonstrated during lichen rehydration, the functions of these compounds are unknown. The aim of this study was to analyze the role of NO during rehydration of the lichen Ramalina farinacea (L.) Ach., its isolated photobiont partner Trebouxia sp. and Asterochloris erici (Ahmadjian) Skaloud et Peksa (SAG 32.85 = UTEX 911).
Results
Rehydration of R. farinacea caused the release of ROS and NO evidenced by the fluorescent probes DCFH2-DA and DAN respectively. However, a minimum in lipid peroxidation (MDA) was observed 2 h post-rehydration. The inhibition of NO in lichen thalli with c-PTIO resulted in increases in both ROS production and lipid peroxidation, which now peaked at 3 h, together with decreases in chlorophyll autofluorescence and algal photobleaching upon confocal laser incidence. Trebouxia sp. photobionts generate peaks of NO-endproducts in suspension and show high rates of photobleaching and ROS production under NO inhibition which also caused a significant decrease in photosynthetic activity of A. erici axenic cultures, probably due to the higher levels of photo-oxidative stress.
Conclusions
Mycobiont derived NO has an important role in the regulation of oxidative stress and in the photo-oxidative protection of photobionts in lichen thalli. The results point to the importance of NO in the early stages of lichen rehydration.This project was funded by the Spanish Ministry of Education and Science [project numbers CGL2006 12917 C02 0 and CGL2009 13429 C02 01], project Prometeo 2008/1/4 of the Generalitat Valenciana and the project AECID PCI/A/024755/09 of the Spanish Ministry of Foreign Affaires. We are grateful to F. Gasulla, J. Gimeno-Romeu, E. Barreno, (ICBIBE, University of Valencia) and A. Guera (Plant Biology, University of Alcala) for communicating unpublished data, to Dr. R. Catala (CIB, Madrid), Dr. P. D'Ocon (UVEG, Valencia) and Dr. J. Medina (INIA, Madrid) for critical revision of the manuscript, and J. L. Rodriguez Gil for MDA protocol optimization. English revision was done by Wendy Ran.CatalĂĄ, M.; Gasulla Vidal, F.; Pradas Del Real, AE.; GarcĂa-Breijo, F.; Reig Armiñana, J.; Barreno Rodriguez, E. (2010). Fungal-associated NO is involved in the regulation of oxidative stress during rehydration in lichen symbiosis. BMC Microbiology. 10. https://doi.org/10.1186/1471-2180-10-297S1
Apports des techniques spectroscopiques en biologie végétale
International audienceAlthough spectroscopic techniques based on very large research infrastructures are commonly used in disciplines such as physics or material sciences, they are less common among plant biologists. However, they give access to information that can greatly advance our understanding of biological mechanisms. Micro X-ray fluorescence micro-spectroscopy (ΌXRF) based on synchrotron radiation makes it possible to obtain elemental distribution maps with a lateral resolution down to submicrometer scale and high sensitivity. In compliment to ΌXRF, some synchrotron beamlines have the capability to perform micro-X-ray absorption spectroscopy (”XAS) analysis. This technique allows to probe the local structure of the element of interest and to determine its oxidation state and its ligands. This is for example very useful in ecotoxicology to understand the behavior and fate of a contaminant to better evaluate its bioavailability and possible impacts on the environment. Alternatively, in agronomy this information can be used to improve plant nutrition. These techniques are, however, extremely dependent on a proper sample preparation. For about ten years, much progress has been made both on the equipment of synchrotron beamlines and on the sample preparation techniques to take into account the particular nature of biological samples (highly hydrated, fragile and sensitive to radiation). These different points will be developed through the example of plants (Lactuca sativa, lettuce) exposed to a foliar iron salt supply and addition of silver nanoparticles
Distinguishing Engineered TiO2 Nanomaterials from Natural Ti Nanomaterials in Soil Using spICP-TOFMS and Machine Learning
International audienceABSTRACT: Identifying engineered nanomaterials (ENMs) made from earth-abundant elements in soils is difficult because soil also contains natural nanomaterials (NNMs) containing similar elements. Here, machine learning models using elemental fingerprints and mass distributions of three TiO2 ENMs and Ti-based NNMs recovered from three natural soils measured by single-particle inductively coupled plasma time-of-flight mass spectrometry (spICP-TOFMS) was used to identify TiO2 ENMs in soil. Synthesized TiO2 ENMs were unassociated with other elements (>98%), while 40% of Ti-based ENM particles recovered from wastewater sludge had distinguishable elemental associations. All Ti-based NNMs extracted from soil had a similar chemical fingerprint despite the soils being from different regions, and >60% of Ti-containing NNMs had no measurable associated elements. A machine learning model best distinguished NNMs and ENMs when differences in Ti-mass distribution existed between them. A trained LR model could classify 100 nm TiO2 ENMs at concentrations of 150 mg kgâ1 or greater. The presence of TiO2 ENMs in soil could be confirmed using this approach for most ENM-soil combinations, but the absence of a unique chemical fingerprint in a large fraction of both TiO2 ENMs and Ti-NNMs increases model uncertainty and hinders accurate quantification
Apports des techniques spectroscopiques en biologie végétale
International audienceAlthough spectroscopic techniques based on very large research infrastructures are commonly used in disciplines such as physics or material sciences, they are less common among plant biologists. However, they give access to information that can greatly advance our understanding of biological mechanisms. Micro X-ray fluorescence micro-spectroscopy (ÎŒXRF) based on synchrotron radiation makes it possible to obtain elemental distribution maps with a lateral resolution down to submicrometer scale and high sensitivity. In compliment to ÎŒXRF, some synchrotron beamlines have the capability to perform micro-X-ray absorption spectroscopy (”XAS) analysis. This technique allows to probe the local structure of the element of interest and to determine its oxidation state and its ligands. This is for example very useful in ecotoxicology to understand the behavior and fate of a contaminant to better evaluate its bioavailability and possible impacts on the environment. Alternatively, in agronomy this information can be used to improve plant nutrition. These techniques are, however, extremely dependent on a proper sample preparation. For about ten years, much progress has been made both on the equipment of synchrotron beamlines and on the sample preparation techniques to take into account the particular nature of biological samples (highly hydrated, fragile and sensitive to radiation). These different points will be developed through the example of plants (Lactuca sativa, lettuce) exposed to a foliar iron salt supply and addition of silver nanoparticles.Si les techniques spectroscopiques basĂ©es sur les trĂšs grandes infrastructures de recherche (TGIR) sont couramment utilisĂ©es dans des disciplines telles que la physique ou encore les sciences des matĂ©riaux, elles sont moins rĂ©pandues chez les biologistes. Elles permettent pourtant dâaccĂ©der Ă des informations qui peuvent faire grandement avancer notre comprĂ©hension des mĂ©canismes biologiques. La micro-spectroscopie par fluorescence X (”XRF) basĂ©e sur le rayonnement synchrotron permet de rĂ©aliser des cartographies Ă©lĂ©mentaires avec une rĂ©solution latĂ©rale pouvant descendre Ă quelques centaines de nanomĂštres et une grande sensibilitĂ©. En parallĂšle Ă la ”XRF, certaines lignes de lumiĂšre au synchrotron permettent de coupler la micro-spectroscopie dâabsorption des rayons X (”XAS). GrĂące Ă cette technique, on peut sonder la structure de lâĂ©lĂ©ment dâintĂ©rĂȘt et dĂ©terminer en particulier son Ă©tat dâoxydation et ses ligands. Câest par exemple trĂšs utile en Ă©cotoxicologie pour comprendre le comportement et le devenir dâun contaminant pour mieux Ă©valuer son impact sur lâenvironnement ou en agronomie pour enrichir des cultures en Ă©lĂ©ments minĂ©raux. Ces techniques sont cependant extrĂȘmement tributaires dâune bonne prĂ©paration dâĂ©chantillons. Depuis une dizaine dâannĂ©es environ, de nombreux progrĂšs ont Ă©tĂ© fait tant sur lâĂ©quipement des lignes de lumiĂšre que sur les techniques de prĂ©paration dâĂ©chantillons pour prendre en compte la nature particuliĂšre des Ă©chantillons biologiques (hautement hydratĂ©s, fragiles et sensibles aux rayonnements). Ces diffĂ©rents points seront dĂ©veloppĂ©s au travers de lâexemple de plantes (Lactuca sativa, salade) exposĂ©es Ă un apport foliaire en fer avec ajout de nanoparticules dâargent
The Chromium Detoxification Pathway in the Multimetal Accumulator <i>Silene vulgaris</i>
Phytomanagement could be a viable alternative
in areas polluted
with wastes from chromium-using industries. This study investigated
the ability of <i>Silene vulgaris</i> to take up CrÂ(III)
and CrÂ(VI) with special attention on the mechanism used by this species
to tolerate high doses of CrÂ(VI). Plants were grown semihydroponically
with different concentrations of either CrÂ(III) or CrÂ(VI). A combination
of synchrotron X-ray spectroscopic techniques, scanning electron and
light microscopy and infrared spectroscopy were used to determine
the distribution and speciation of Cr. <i>S. vulgaris</i> accumulated more Cr when grown with CrÂ(VI) resulting in an overall
reduction in biomass. Starch accumulation in leaves may be attributed
to an impartment between carbon utilization and assimilation resulted
from stunted plant growth but not the complete inhibition of photosynthesis
indicating that <i>S. vulgaris</i> possess tolerance mechanisms
that allows it to survive in CrÂ(VI) rich environments. These primary
tolerance mechanisms are (a) the total reduction of CrÂ(VI) to CrÂ(III)
in the rhizosphere or just after uptake in the fine lateral root tips
and (b) chelation of CrÂ(III) to the cell wall both of which reduce
metal interference with critical cell functions. These mechanisms
make <i>S. vulgaris</i> suitable for in situ remediation
of Cr polluted soils
Silver nanoparticles and wheat roots: a complex interplay
International audienceAgricultural soils are major sinks of silver nanoparticles in the environment, and crops are directly exposed to these emerging contaminants. A clear picture of their chemical transformations, uptake and transport mechanisms, and phytotoxic impacts is still lacking. In this work, wheat plants were exposed to pristine metallic (Ag-NPs) and sulfidized (AgS-NPs) silver nanoparticles and ionic Ag. Data on Ag distribution and speciation, phytotoxicity markers and gene expression were studied. A multi-technique and multi-scale approach was applied combining innovating tools at both laboratory and synchrotron. Various chemical transformations were observed on the epidermis and inside roots, even for AgS-NPs, leading to an exposure to multiple Ag forms, which likely evolve over time. Genes involved in various functions including oxidative stress, defense against pathogens and metal homeostasis were impacted in different ways depending on the Ag source. This study illustrates the complexity of the toxicity pattern for plants exposed to Ag-NPs, the necessity of monitoring several markers to accurately evaluate the toxicity, and the interest of interpreting the toxicity pattern in light of the distribution and speciation of Ag
Assessing implications of nanoplastics exposure to plants with advanced nanometrology techniques
International audienceDespite the increasing attention given to the impacts of nanoplastics in terrestrial environments, there is limited data about the effects on plants, and the quantitative information on uptake. In the present study, wheat plants grown in hydroponics were exposed to Pd-doped nanoplastics. This allowed us to quantify nanoplastics uptake and translocation to the shoots. Visualization of nanoplastics in roots was performed with synchrotron micro X-ray fluorescence (”XRF). Nanoplastics accumulated on the root epidermis, especially at the root tip and in root maturation zones. A close relationship between plant roots, rhizodeposits and nanoplastics behaviour was shown. Reinforcement of the cell wall in roots was evidenced using Fourier transform infrared spectroscopy (FTIR) and synchrotron-computed microtomography (”CT). Synchrotron-computed nanotomography (nanoCT) evidenced the presence of globular structures but they could not be identified as nanoplastics since they were observed both in the control and treated roots. By utilizing the inorganic tracer in the doped-nanoplastics, this study paves the road for elucidating interactions in more complex systems by using an integrative approach combining classical phytotoxicity markers with advanced nanometrology techniques
Impact of a Model Soil Microorganism and of Its Secretome on the Fate of Silver Nanoparticles
International audienceSulfidation is a key process for silver nano-particles released from consumer products in the environment. This study focuses on the impact of a model soil microorganism , Bacillus subtilis, on the fate of pristine and already sulfidized Ag-NPs. The nanoparticles were incubated with the initial growth medium, isolated secretome, and living bacteria, and characterized for their size and morphology, agglomeration state, structure, and Ag speciation. No Ag internalization or sorption on the cell wall was detected. A partial sulfidation, leading to an AgâAg 2 S coreâshell structure, was observed in the presence of the secretome, and the rate limiting step of the reaction was the oxidation of Ag 0 , and it was favored near the crystal dislocations. The sulfidation was complete in the presence of the living bacteria and followed an indirect pathway. Both crystalline Ag 2 S and amorphous Ag 2 S and/or Ag-thiol were identified. At the opposite, the bacteria had no impact on Ag 2 S. These results suggest that microorganisms participate in the sulfidation of Ag-NPs in aerobic systems such as unsaturated soils, and thus affect the bioavailability of Ag. It is important to take these transformations into account during exposure experiments, since they drastically change the exposure conditions. Finally, the secretome of B. subtilis might be used for the green synthesis of AgâAg 2 S coreâshell nanoparticles
Searching for relevant criteria to distinguish natural vs. anthropogenic TiO 2 nanoparticles in soils
International audienceis one of the most produced nanomaterials. Agricultural soils are a major compartment of accumulation of TiO 2-NPs after release from consumer products into the sewer system, due to the use of sewage sludge as a soil amendment. TiO 2 is naturally present in soils, and distinguishing between anthropo-genic and natural TiO 2 in soils is thus important to assess the risks associated with the increased use of nano-TiO 2. Methods to distinguish these materials in complex matrices such as soils are currently lacking. The purpose of this study was, therefore, to search for characteristic physical and chemical properties of natural and engineered nano-TiO 2 , based on a combination of bulk, micro and nanofocused X-ray fluorescence and X-ray absorption spectroscopy, transmission electron microscopy, X-ray diffraction and chemical analyses. Digested sewage sludge, agricultural soil and sludge-amended soil were studied by these techniques. The particle size distribution was not a relevant criterion since the sludge and the sludge-amended soil contained a variety of nanometer-and micrometer sized Ti-containing particles. Both the sludge and the soil contained a mixture of rutile and anatase, with a minor proportion of amorphous TiO 2. In the sludge, there was no trend relating particle size and Ti mineralogy. The morphology of the TiO 2 particles proved to be different in the two matrices, with smooth faceted particles in the sludge and rough irregular ones in the soil. In addition, natural TiO 2 particles were included in micro and macroaggregates of the soil and formed intricate assemblages with minerals and organic compounds. In the sludge, TiO 2 formed homo and heteroaggregates of simpler structure, richer in organic matter. Thus, the study of the morphology of TiO 2 particles and their status in unperturbed mineral-organic assemblages may provide some insights into their origin. The observed differences may attenuate over time, due to the incorporation of the sludge material within the soil structure