Insufficient intake of zinc and iron from a cereal-based diet is one of the causes of 'hidden hunger' (micronutrient deficiency), which affects some two billion people(1,2). Identifying a limiting factor in the molecular mechanism of zinc loading into seeds is an important step towards determining the genetic basis for variation of grain micronutrient content and developing breeding strategies to improve this trait(3). Nutrients are translocated to developing seeds at a rate that is regulated by transport processes in source leaves, in the phloem vascular pathway, and at seed sinks. Nutrients are released from a symplasmic maternal seed domain into the seed apoplasm surrounding the endosperm and embryo by poorly understood membrane transport processes(4-6). Plants are unique among eukaryotes in having specific P1B-ATPase pumps for the cellular export of zinc(7). In Arabidopsis, we show that two zinc transporting P1B-ATPases actively export zinc from the mother plant to the filial tissues. Mutant plants that lack both zinc pumps accumulate zinc in the seed coat and consequently have vastly reduced amounts of zinc inside the seed. Blockage of zinc transport was observed at both high and low external zinc supplies. The phenotype was determined by the mother plant and is thus due to a lack of zinc pump activity in the seed coat and not in the filial tissues. The finding that P1B-ATPases are one of the limiting factors controlling the amount of zinc inside a seed is an important step towards combating nutritional zinc deficiency worldwide.

Engineered nanoparticles such as graphenes, nanodiamonds, and carbon nanotubes correspond to different allotropes of carbon and are among the best candidates for applications in fast-growing nanotechnology. It is thus likely that they may get into the environment at each step of their life cycle: production, use, and disposal. The aquatic compartment concentrates pollutants and is expected to be especially impacted. The toxicity of a compound is conventionally evaluated using mass concentration as a quantitative measure of exposure. However, several studies have highlighted that such a metric is not the best descriptor at the nanoscale. Here we compare the inhibition of Xenopus laevis larvae growth after in vivo exposure to different carbon nanoparticles for 12 days using different dose metrics and clearly show that surface area is the most relevant descriptor of toxicity for different types of carbon allotropes.

The toxicity of CeO2 NPs on an experimental freshwater ecosystem was studied in mesocosm, with a focus being placed on the higher trophic level, i.e. the carnivorous amphibian species Pleurodeles waltl. The system comprised species at three trophic levels: (i) bacteria, fungi and diatoms, (ii) Chironomus riparius larvae as primary consumers and (iii) Pleurodeles larvae as secondary consumers. NP contamination consisted of repeated additions of CeO2 NPs over 4 weeks, to obtain a final concentration of 1 mg/L. NPs were found to settle and accumulate in the sediment. No effects were observed on litter decomposition or associated fungal biomass. Changes in bacterial communities were observed from the third week of NP contamination. Morphological changes in CeO2 NPs were observed at the end of the experiment. No toxicity was recorded in chironomids, despite substantial NP accumulation (265.8 ± 14.1 mg Ce/kg). Mortality (35.3 ± 6.8%) and a mean Ce concentration of 13.5 ± 3.9 mg/kg were reported for Pleurodeles. Parallel experiments were performed on Pleurodeles to determine toxicity pathways: no toxicity was observed by direct or dietary exposures, although Ce concentrations almost reached 100 mg/kg. In view of these results, various toxicity mechanisms are proposed and discussed. The toxicity observed on Pleurodeles in mesocosm may be indirect, due to microorganism's interaction with CeO2 NPs, or NP dissolution could have occurred in mesocosm due to the structural complexity of the biological environment, resulting in toxicity to Pleurodeles. This study strongly supports the importance of ecotoxicological assessment of NPs under environmentally relevant conditions, using complex biological systems.

The worldwide increase of graphene family materials raises the question of the potential consequences resulting from their release in the environment and future consequences on ecosystem health, especially in the aquatic environment in which they are likely to accumulate. Thus, there is a need to evaluate the biological and ecological risk but also to find innovative solutions leading to the production of safer materials. This work focuses on the evaluation of functional group-safety relationships regarding to graphene oxide (GO) in vivo genotoxic potential toward X. laevis tadpoles. For this purpose, thermal treatments in H2 atmosphere were applied to produce reduced graphene oxide (rGOs) with different surface group compositions. Analysis performed indicated that GO induced disturbances in erythrocyte cell cycle leading to accumulation of cells in G0/G1 phase. Significant genotoxicity due to oxidative stress was observed in larvae exposed to low GO concentration (0.1 mg.L−1). Reduction of GO at 200 °C and 1000 °C produced a material that was no longer genotoxic at low concentrations. X-ray photoelectron spectroscopy (XPS) analysis indicated that epoxide groups may constitute a good candidate to explain the genotoxic potential of the most oxidized form of the material. Thermal reduction of GO may constitute an appropriate “safer-by-design” strategy for the development of a safer material for environment.

Extensive development of new applications using graphene based materials such as graphene oxide (GO) increases its potential release and occurrence into aquatic environments, raising the question of its biological and ecological risks. As standardized single species based assays fail to highlight t(l)(icological pathways implying interactions between organisms, the use of micro/mesocosms appears as a good solution to fill the lack of environmental realism inherent to these tests. In this work, experiments were achieved using microcosm systems to expose a reconstituted food chain to GO at environmentally relevant concentrations (0.05 and 0.1 mgL 1 ). The trophic chain was composed of a consortium of algae and bacteria as primary producers, chironomid larvae as primary consumers and decomposers while larvae of the amphibian Pleurode/es wa/tii constituted the secondary consumers. Monitoring of multiple ecotoxicological and ecological endpoints allowed to observe changes in bacterial communities while no toxic effects were noticed in chironomids. However, chironomids feeding behaviour changed as a consequence of GO contamination, leading to an increase in leaf litter consumption. Genotoxic effects were noticed in Pleurode/es larvae. This study highlights the importance of using such experimental systems to better encompass the ecotoxic potential of GO through the determination of t(l)(icological routes and consequences on ecosystem's functioning.

Ecotoxicity studies conducted under environmentally relevant conditions are crucial to understanding the long-term fate of nanoparticles and their impact on ecosystems. In this study, the impacts of CeO 2 NPs on an experimental aquatic ecosystem are assessed in microcosm. The results provide evidence that CeO 2 NPs lead to teratogenicity in chironomid larvae and to a significant decrease in leaf litter decomposition. These effects might result in important impacts on aquatic ecosystems by decreasing the available organic matter used by numerous primary consumers that are the basis of many food webs. The results also show that effect endpoints, such as litter decomposition and teratogenicity in invertebrates, can be used as relevant and powerful markers of the long-term impact of NPs. Abstract 1We investigated the impact of CeO 2 nanoparticles (NPs) with different sizes, shapes and 2 coatings on the function of a freshwater experimental ecosystem. We hypothesized that the 3 different types of NPs would have different effects on the organisms involved in leaf litter 4 decomposition and could differentially affect this process. Experiments were conducted in 5 microcosm under environmentally relevant conditions with low CeO 2 NP concentrations (1 6 mg/L). Leaf litter decomposition, leaf-associated fungal biomass, bacterial community 7 diversity and toxicity on Chironomus riparius larvae were studied. A decrease in 8 teratogenicity (mouthpart deformities) in chironomid larvae was observed with citrate-coated 9 spherical NPs, suggesting a hormesis effect. In contrast, exposure to non-coated, spherical 10 NPs led to increased teratogenicity in chironomids, changes in bacterial community diversity 11 and decreased leaf litter decomposition. Large, non-coated plates induced changes in bacterial 12 assemblages, whereas no effect on fungal biomass was observed. These results are discussed 13 and several hypotheses are presented to explain the results. Leaf litter decomposition is a 14 marker that is frequently used to assess freshwater ecosystems' health. Extending its use to 15 nano-ecotoxicology enables the study of the NP impact on the function of ecosystems. This 16 study shows that leaf litter decomposition and mouthpart deformities in chironomid larvae are 17 sensitive, congruent markers of the environmental impact of CeO 2 NPs under these 18 experimental conditions. 65 homogenized in an ultrasonic bath (Bioblock, type 570 HF, Freq 35 KHz) for 10 minutes and 66 sampled to prepare fresh suspensions (93.4 mg/L) in ultrapure water. 67 Stock suspensions were characterized by Transmission Electron Microscopy (TEM, Jeol 68 Jem 2100, 200Kv, HR; see Supplementary Information, figure S1) to determine the primary 69 size and shape of the NPs. The NPs were also characterized in microcosms throughout the 70 2.7 Data analysis 173Differences in the AFDM contents and fungal biomass between groups were tested for 174 significance using a one-way analysis of variance (ANOVA) test, followed by Tukey's test. 175The differences in the bo...

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 16789To link to this article : AbstractIn the last few years, graphene has been defined as the revolutionary material showing an incredible expansion in industrial applications. Different graphene forms have been applied in several contexts, spreading from energy technologies and electronics to food and agriculture technologies. Graphene showed promises also in the biomedical field. Hopeful results have been already obtained in diagnostic, drug delivery, tissue regeneration and photothermal cancer ablation. In view of the enormous development of graphene-based technologies, a careful assessment of its impact on health and environment is demanded. It is evident how investigating the graphene toxicity is of fundamental importance in the context of medical purposes. On the other hand, the nanomaterial present in the environment, likely to be generated all along the industrial life-cycle, may have harmful effects on living organisms. In the present work, an important contribution on the impact of multi-layer graphene (MLG) on health and environment is given by using a multifaceted approach. For the first purpose, the effect of the material on two mammalian cell models was assessed. Key cytotoxicity parameters were considered such as cell viability and inflammatory response induction. This was combined with an evaluation of MLG toxicity towards Xenopus laevis, used as both in vivo and environmental model organism.

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible.