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A pre-diabetes syndrome induced by endocrine disruptors (ED) was recently demonstrated in the model amphibian Silurana (Xenopus) tropicalis and was suggested to be a potential cause of amphibian population decline. However, such effects have not been found in wild type frogs exposed to ED and the capacity of amphibians to physiologically develop diabetes under natural conditions has not been confirmed. This study showed that a high fat diet (HFD) model displaying the important characteristics of mammal HFD models including glucose intolerance, insulin resistance and nonalcoholic fatty liver disease (NAFLD) can be developed with green frogs (Pelophylax spp.). Wild green frogs exposed to 10 μg L

Animals must partition limited resources between their own growth and subsequent reproduction. Endocrine disruptors (ED) may cause maternal metabolic disorders that decrease successful reproduction and might be responsible for multi- and transgenerational effects in amphibians. We found that the frog Silurana (Xenopus) tropicalis, exposed to environmentally relevant concentrations of benzo[a]pyrene and triclosan throughout its life cycle, produced F1 females with delayed sexual maturity and decreased size and weight. These F1 females displayed a marked metabolic syndrome associated with decreased fasting plasma cholesterol and triglyceride concentrations and decreased gonadal development. F1 females from F0 exposed animals also had decreased reproductive investment highlighted by a decrease of oocyte lipid reserves associated with significant F2-tadpole mortality. F2 females from F0 exposed animals also displayed a marked metabolic syndrome but were able to correctly direct liver lipid metabolism to the constitution of fat bodies and oocyte yolk stores. In addition, the F2 females produced progeny that had normal mortality levels at 5 days post hatching compared to the controls suggesting a good reproductive investment. Our data confirmed that these ED, at concentrations often found in natural ponds, can induce multi- and transgenerational metabolic disorders in the progeny of amphibians that are not directly exposed. We present a hypothesis to explain the transmission of the metabolic syndrome across generations through modification of egg reserves. However, when high mortality occurred at the tadpole stage, surviving females were able to cope with metabolic costs and produce viable progeny through sufficient investment in the contents of oocyte reserves.

Polychlorinated biphenyls (PCBs) are organic pollutants that are harmful to environment and toxic to humans. Numerous studies, based on basidiomycete strains, have reported unsatisfactory results in the mycoremediation of PCB-contaminated soils mainly due to the non-telluric origin of these strains. The abilities of a five-Ascomycete-strain consortium in the mycoremediation of PCB-polluted soils and its performance to restore their sound functioning were investigated using mesocosm experiments associated with chromatography gas analysis and enzymatic activity assays. With the soil H containing 850 ppm PCB from which the strains had been isolated, a significant PCB depletion of 29% after three months of treatment was obtained. This led to an important decrease of PCBs from 850 to 604 ppm. With the soil L containing 36 ppm PCB, biodegradation did not occur. In both soils, the fungal biomass quantified by the ergosterol assay, did not increase at the end of the treatment. Biodegradation evidenced in the soil H resulted in a significantly improved stoichiometry of N and P acquiring enzymatic activities. This unprecedented study demonstrates that the native Ascomycetes display remarkable properties for remediation and restoration of functioning of the soil they originated from paving the way for greater consideration of these strains in mycoremediation.

Polychlorinated biphenyls (PCBs) are widespread persistent pollutants deleterious for environment and very dangerous for human kind. As the bioremediation of PCB polluted sites by model white-rot fungi is still unsatisfactory, the use of efficient native strains which have the natural capacity to develop on polluted sites may constitute a relevant alternative strategy. In this study, we isolated 12 fungal strains from PCB contaminated soil and sediment, improved the screening method to obtain the most efficient ones in biodegradation and detoxification of PCBs and characterized potential underlying enzymatic activities. Four strains Penicillium chrysogenum, P. citreosulfuratum, P. canescens and Aspergillus jensenii, showed remarkable biodegradation capacities, greater than 70%. The remaining PCB-toxicity of their culture, including that of Trametes versicolor and Acremonium sclerotigenum, which present interesting ecological and metabolic properties, was studied. Only P. canescens was able to significantly reduce the toxicity related to PCBs and their metabolites. The enzymatic activities induced by PCBs were different according to the strains, namely laccases in T. versicolor and peroxidases in Ac. sclerotigenum. Our promising results show that the use of native fungal strains can constitute an effective strategy in the depollution of PCB polluted sites.

International audience; Metabolic disorders induced by endocrine disruptors (ED) may contribute to amphibian population declines but no transgenerational studies have evaluated this hypothesis. Here we show that Xenopus tropicalis, exposed from the tadpole stage, to the ED benzo[a]pyrene (BaP, 50 ng.L−1) produced F2 progeny with delayed metamorphosis and sexual maturity. At the adult stage, F2–BaP females displayed fatty liver with inflammation, tissue disorganization and metabolomic and transcriptomic signatures typical of nonalcoholic steato-hepatitis (NASH). This phenotype, similar to that observed in F0 and F1 females, was accompanied by a pancreatic insulin secretory defect. Metabolic disrupted F2–BaP females laid eggs with metabolite contents significantly different from the control and these eggs did not produce viable progeny. This study demonstrated that an ED can induce transgenerational disruption of metabolism and population collapse in amphibians under laboratory conditions. These results show that ED benzo[a]pyrene can impact metabolism over multiple generations and support epidemiological studies implicating environmental EDs in metabolic diseases in humans.

Polychlorinated biphenyls (PCBs) belong to the organic pollutants that are toxic to humans and harmful to environments. Numerous studies dealing with the impact of PCBs on soil microorganisms have focused on bacterial communities. The effects of PCBs on fungal communities in three different PCB-polluted soils from former industrial sites were investigated using high-throughput sequencing of the internal transcribed spacer 1 region. Significant differences in fungal alpha diversity were observed mainly due to soil physico-chemical properties. PCBs only influenced the richness of the fungal communities by increasing it. Fungal composition was rather strongly influenced by both PCBs and soil properties, resulting in different communities associated with each soil. Sixteen Ascomycota species were present in all three soils, including Stachybotrys chartarum, Fusarium oxysporum, Penicillium canescens, Penicillium chrysogenum,Penicillium citrosulfuratum and Penicillium brevicompactum, which are usually found in PCB-polluted soils, and Fusarium solani, Penicillium canescens, Penicillium citrosulfuratum and Penicillium chrysogenum, which are known PCB degraders. This study demonstrated that PCBs influence the richness and the composition of fungal communities. Their influence, associated with that of soil physico-chemical properties, led to distinct fungal communities, but with sixteen species common to the three soils which could be considered as ubiquitous species in PCB-polluted soils.

International audience; The persistent organochlorine pesticides (OCPs) in soils are suspected to disturb soil biogeochemical cycles. This study addressed the dynamic changes in soil functionality under lindane and chlordecone exposures with or without maize plant. Decreases in soil ammonium concentration, potential nitrogen mineralization and microbial biomass were only OCP-influenced in bulk soils. OCPs appeared to inhibit the ammonification step. With plants, soil functionality under OCP stress was similar to controls demonstrating the plant influence to ensure the efficiency of C- and N-turnover in soils. Moreover, OCPs did not impact the microbial community physiological profile in all tested conditions. However, microbial community structure was OCP-modified only in the presence of plants. Abundances of gram-negative and saprophytic fungi increased (up to +93% and +55%, respectively) suggesting a plant stimulation of nutrient turnover and rhizodegradation processes. Nevertheless, intimate microbial/plant interactions appeared to be OCP-impacted with depletions in mycorrhizae and micro/meso-fauna abundances (up to −53% and −56%, respectively) which might have adverse effects on more long-term plant growth (3–4 months). In short-term experiment (28 days), maize growth was similar to the control ones, indicating an enhanced plasticity of the soil functioning in the presence of plants, which could efficiently participate to the remediation of OCP-contaminated soils.

By performing a controlled exposure of an amphibian model to endocrine disruptors (EDs) at concentrations within the range of safe drinking water, we provide evidence of the role played by these widespread contaminants in amphibian population decline through metabolic disruption. In frogs exposed throughout their life cycle, this disruption induces a metabolic syndrome characteristic of a prediabetes state. Exposed animals produce progeny that metamorphose later, are smaller and lighter at the adult stage, and have reduced reproductive success. These transgenerational effects of EDs may impact overwintering survival, recruitment for reproduction, and fitness, each representing possible triggers of population decline.

International audience; Despite numerous studies suggesting that amphibians are highly sensitive to endocrine disruptors (EDs), both their role in the decline of populations and the underlying mechanisms remain unclear. This study showed that frogs exposed throughout their life cycle to ED concentrations low enough to be considered safe for drinking water, developed a prediabetes phenotype and, more commonly, a metabolic syndrome. Female Xenopus tropicalis exposed from tadpole stage to benzo(a)pyrene or triclosan at concentrations of 50 ng⋅L-1 displayed glucose intolerance syndrome, liver steatosis, liver mitochondrial dysfunction, liver transcriptomic signature, and pancreatic insulin hypersecretion, all typical of a prediabetes state. This metabolic syndrome led to progeny whose metamorphosis was delayed and occurred while the individuals were both smaller and lighter, all factors that have been linked to reduced adult recruitment and likelihood of reproduction. We found that F1 animals did indeed have reduced reproductive success, demonstrating a lower fitness in ED-exposed Xenopus Moreover, after 1 year of depuration, Xenopus that had been exposed to benzo(a)pyrene still displayed hepatic disorders and a marked insulin secretory defect resulting in glucose intolerance. Our results demonstrate that amphibians are highly sensitive to EDs at concentrations well below the thresholds reported to induce stress in other vertebrates. This study introduces EDs as a possible key contributing factor to amphibian population decline through metabolism disruption. Overall, our results show that EDs cause metabolic disorders, which is in agreement with epidemiological studies suggesting that environmental EDs might be one of the principal causes of metabolic disease in humans.

Organochlorines (OCs) are persistent chemicals found in various environmental compartments. The differences in the uptake of 14C-labeled 1,4-dichlorobenzene (DCB), 1,2,4-trichlorobenzene (TCB) and γ-hexachlorocyclohexane (γHCH) by Phragmites australis were investigated under hydroponic conditions. The first step in sorption appears to be correlated with the hydrophobic nature of the compounds, since log-linear correlations were obtained between root concentration factor and partition coefficient (LogKow). After 7 days of exposure, plant uptake of DCB, TCB, γHCH was significant with bioconcentration factors reaching 14, 19 and 15, respectively. Afterwards, uptake and translocation were seen to be more complex, with a loss of the simple relationship between uptake and LogKow. Linear correlations between the bioconcentration/translocation factors and the physico-chemical properties of OCs were shown, demonstrating that translocation from roots to shoots increases with solubility and volatility of the OCs. This suggests that OC-translocation inside plants might result from the combination of two processes, xylem sap flow and vapor fluxes. 14C-phytovolatilization was measured and was correlated with the volatility of the compounds; the more volatile OCs being most the likely to be phytovolatilized from foliar surfaces (p = 0.0008). Thus, OC-uptake/translocation appears to proceed at a rate that depends mostly on the OCs hydrophobicity, solubility and volatility.

International audience; Despite numerous studies suggesting that amphibians are highly sensitive to cumulative anthropogenic stresses, the role played by endocrine disruptors (EDs) in the decline of amphibian populations remains unclear. EDs have been extensively studied in adult amphibians for their capacity to disturb reproduction by interfering with the sexual hormone axis. Here, we studied the in vivo responses of Xenopus tropicalis males exposed to environmentally relevant concentrations of each ED, benzo[a]pyrene (BaP) and triclosan (TCS) alone (10 μg L(-1)) or a mixture of the two (10 μg L(-1) each) over a 24 h exposure period by following the modulation of the transcription of key genes involved in metabolic, sexual and immunity processes and the cellular changes in liver, spleen and testis. BaP, TCS and the mixture of the two all induced a marked metabolic disorder in the liver highlighted by insulin resistance-like and non-alcoholic fatty liver disease (NAFLD)-like phenotypes together with hepatotoxicity due to the impairment of lipid metabolism. For TCS and the mixture, these metabolic disorders were concomitant with modulation of innate immunity. These results confirmed that in addition to the reproductive effects induced by EDs in amphibians, metabolic disorders and immune system disruption should also be considered.

(1)H-HRMAS NMR-based metabolomics was used to better understand the toxic effects on maize root tips of organochlorine pesticides (OCPs), namely lindane (γHCH) and chlordecone (CLD). Maize seedlings were exposed to 2.5 μM γHCH (mimicking basic environmental contaminations) for 7 days and compared to 2.5 μM CLD and 25 μM γHCH for 7 days (mimicking hot spot contaminations). The (1)H-HRMAS NMR-based metabolomic profiles provided details of the changes in carbohydrates, amino acids, tricarboxylic acid (TCA) cycle intermediates and fatty acids with a significant separation between the control and OCP-exposed root tips. First of all, alterations in the balance between glycolysis/gluconeogenesis were observed with sucrose depletion and with dose-dependent fluctuations in glucose content. Secondly, observations indicated that OCPs might inactivate the TCA cycle, with sizeable succinate and fumarate depletion. Thirdly, disturbances in the amino acid composition (GABA, glutamine/glutamate, asparagine, isoleucine) reflected a new distribution of internal nitrogen compounds under OCP stress. Finally, OCP exposure caused an increase in fatty acid content, concomitant with a marked rise in oxidized fatty acids which could indicate failures in cell integrity and vitality. Moreover, the accumulation of asparagine and oxidized fatty acids with the induction of LOX3 transcription levels under OCP exposure highlighted an induction of protein and lipid catabolism. The overall data indicated that the effect of OCPs on primary metabolism could have broader physiological consequences on root development. Therefore, (1)H-HRMAS NMR metabolomics is a sensitive tool for understanding molecular disturbances under OCP exposure and can be used to perform a rapid assessment of phytotoxicity.

Coquillettidia mosquitoes are not efficiently controlled by the conventional chemical practices which are known to be satisfactory against the larvae of other mosquito species. A research project was undertaken to conceive a new management strategy using plants as pesticide vectors to reach the Coquillettidia aquatic larvae. Therefore, larval mortality was measured in the presence of plants treated with phloem-translocated pesticides. The herbicide glyphosate at sub-lethal concentrations induced root epidermal cell lyses in maize plantlets cultivated in aqueous media, which clearly decreased larval fixation. Therefore, such herbicide strategy might operate through disturbing the larval physiological activities depending on fixation. The dimethoate insecticide did not affect root viability but at low concentrations seemed to disturb the plant–insect interactions. Larvae showed a lower attraction for roots and a considerable decrease in the root fixation rate. These larval behavior modifications were sufficient to induce mortality, probably due to a lack of fixation on plant roots. The effectiveness of plant foliar treatment with glyphosate or dimethoate under laboratory conditions suggested that it might be the basis for an efficient control strategy for Coquillettidia larvae and mosquitoes having the same living conditions in ponds and for which fixation on macrophyte roots is an absolute requirement ( e.g. Mansonia , Mimomyia ).

Background Despite numerous studies suggesting that amphibians are highly sensitive to cumulative anthropogenic stresses, the role pollutants play in the decline of amphibian populations remains unclear. Amongst the most common aquatic contaminants, polycyclic aromatic hydrocarbons (PAHs) have been shown to induce several adverse effects on amphibian species in the larval stages. Conversely, adults exposed to high concentrations of the ubiquitous PAH, benzo[a]pyrene (BaP), tolerate the compound thanks to their highly efficient hepatic detoxification mechanisms. Due to this apparent lack of toxic effect on adults, no studies have examined in depth the potential toxicological impact of PAH on the physiology of adult amphibian livers. This study sheds light on the hepatic responses of Xenopus tropicalis when exposed to high environmentally relevant concentrations of BaP, by combining a high throughput transcriptomic approach (mRNA deep sequencing) and a characterization of cellular and physiological modifications to the amphibian liver. Results Transcriptomic changes observed in BaP-exposed Xenopus were further characterized using a time-dependent enrichment analysis, which revealed the pollutant-dependent gene regulation of important biochemical pathways, such as cholesterol biosynthesis, insulin signaling, adipocytokines signaling, glycolysis/gluconeogenesis and MAPK signaling. These results were substantiated at the physiological level with the detection of a pronounced metabolic disorder resulting in a possible insulin resistance-like syndrome phenotype. Hepatotoxicity induced by lipid and cholesterol metabolism impairments was clearly identified in BaP-exposed individuals. Conclusions Our data suggested that BaP may disrupt overall liver physiology, and carbohydrate and cholesterol metabolism in particular, even after short-term exposure. These results are further discussed in terms of how this deregulation of liver physiology can lead to general metabolic impairment in amphibians chronically exposed to contaminants, thereby illustrating the role xenobiotics might play in the global decline in amphibian populations. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-666) contains supplementary material, which is available to authorized users.

Organochlorine pesticides (OCPs) are widespread environmental pollutants; two of them are highly persistent: lindane (γHCH) and chlordecone (CLD). Maize plants cope with high levels of OCP-environmental pollution, however little is known about cellular mechanisms involved in plant response to such OCP-exposures. This research was aimed at understanding the physiological pathways involved in the plant response to OCPs in function of a gradient of exposure. Here we provide the evidences that OCPs might disrupt root cell cycle leading to a rise in the level of polyploidy possibly through mechanisms of endoreduplication. In addition, low-to-high doses of γHCH were able to induce an accumulation of H2O2 without modifying NO contents, while CLD modulated neither H2O2 nor NO production. [Ca2+]cytosolic, the caspase-3-like activity as well as TUNEL-positive nuclei and IP-positive cells increased after exposure to low-to-high doses of OCPs. These data strongly suggest a cascade mechanism of the OCP-induced toxic effect, notably with an increase in [Ca2+]cytosolic and caspase-3-like activity, suggesting the activation of programmed cell death pathway.

Mosquito breeding sites consist of water pools, which can either be large open areas or highly covered ponds with vegetation, thus with different light exposures combined with the presence in water of xenobiotics including polycyclic aromatic hydrocarbons (PAHs) generated by urban pollution. UV light and PAHs are abiotic factors known to both affect the mosquito insecticide resistance status. Nonetheless, their potential combined effects on the mosquito physiology have never been investigated. The present article aims at describing the effects of UV exposure alongside water contamination with two major PAH pollutants (fluoranthene and benzo[a]pyrene) on a laboratory population of the yellow fever mosquito Aedes aegypti. To evaluate the effects of PAH exposure and low energetic UV (UV-A) irradiation on mosquitoes, different parameters were measured including: (1) The PAH localization and its impact on cell mortality by fluorescent microscopy; (2) The detoxification capacities (cytochrome P450, glutathione-S-transferase, esterase); (3) The responses to oxidative stress (Reactive Oxygen Species-ROS) and (4) The tolerance of mosquito larvae to a bioinsecticide (Bacillus thuringiensis subsp. israelensis-Bti) and to five chemical insecticides (DDT, imidacloprid, permethrin, propoxur and temephos). Contrasting effects regarding mosquito cell mortality, detoxification and oxidative stress were observed as being dependent on the pollutant considered, despite the fact that the two PAHs belong to the same family. Moreover, UV is able to modify pollutant effects on mosquitoes, including tolerance to three insecticides (imidacloprid, propoxur and temephos), cell damage and response to oxidative stress. Taken together, our results suggest that UV and pollution, individually or in combination, are abiotic parameters that can affect the physiology and insecticide tolerance of mosquitoes; but the complexity of their direct effect and of their interaction will require further investigation to know in which condition they can affect the efficacy of insecticide-based vector control strategies in the field.

Formulated herbicides are frequently applied as carboxylesters. The first step in the metabolism of these compounds in plants is enzymatic deesterification, which generally leads to their bioactivation and increases their mobility within the plant. In apoplastic extracts from wheat devoid of cytoplasmic contamination, we have identified a pool of nitrophenyl acetate and naphthyl acetate esterases. These esterases were resolved by isoelectric focusing and activity staining into at least 11 proteins. Furthermore, the apoplastic pool of esterases could be distinguished from soluble esterases in whole-leaf extracts by two-dimensional electrophoresis and their affinity for concanavalin A. The apoplastic fraction deesterified some but not all members of the arylphenoxypropionate family of herbicides tested. Deesterification was inhibited by phenylmethylsulfonyl fluoride. We conclude that there is a pool of soluble carboxylesterases in the leaf apoplast of wheat seedlings that are largely both glycoproteins and serine hydrolases. These apoplastic esterases catalyze the hydrolysis of herbicide esters and are substrate specific. We speculate that the apoplastic esterases contribute to the bioavailability of herbicides in planta.

Atrazine is a herbicide widely used in corn culture. Corn seedlings metabolize this active ingredient readily in three ways. Two of them are catalysed by enzymes and another is purely chemical. In seedlings, the precise role played by each of these was still not clearly understood. Our work demonstrates that the chemical pathway leading to the formation of the inactive OH-2 atrazine is the pre-eminent form of metabolization inside the roots and, during the first week, inside the leaves. As shown by the kinetics of accumulation of the benzoxazinones responsible for this metabolization, a high potential of atrazine hydroxylation remains effective inside the leaves for at least 1 month. The OH-2 atrazine, which seems to accumulate inside the cell vacuoles, cannot move freely inside the plant and therefore cannot be abundantly transported from roots to leaves. The formation of a glutathione-atrazine conjugate, due to the activity of a glutathione-S-transferase (GST) isoenzyme, represents only a very small part of the total GST in corn. It is mostly present in the aerial parts and is highly effective only after a 1-week culture. When analysing the mixture of the metabolites formed in isolated corn leaves, which is very complex (nine products, among which six were major products), it seems that the metabolization pattern of corn leaves is the combined result of the three pathways and of the transformation of the conjugate into more simple derivatives.

Several different matrices (water, n -butanol, n -octanol, lecithin, waxes, and suber) were chosen to measure [ 14 C]atrazine diffusion rate and evaluate the specific diffusion parameter of this molecule. A simple experimen tal device was conceived for this purpose and two methods of calculation, deduced from Fick's law, were established and compared. The same device was used for diffusion measurements inside corn seedling fragments, either dead or alive. In inert matrices, the highest diffusion parameter found for atrazine was obtained for water (2.6 ± 0.9) 10 −10 m 2 s −1 . For more lipophilic matrices, the value of the specific parameter decreased markedly, reaching only (1.2 ± 1) 10 −12 m 2 s −1 for glycerides and (2.5 ± 2.4) 10 −13 m 2 s −1 for paraffin. For dead corn roots or coleoptile, the diffusion parameter was close to that in water: (3.7 ± 2.1) 10 −10 m 2 s −1 and (9.6 ± 4) 10 −10 m 2 s −1 . In living material, the movement of 14 C-labeled compounds was much lower: (7.4 ± 4.6) 10 −11 m 2 s −1 and (1.6 ± 1.5) 10 −11 m 2 s −1 . This was explained by atrazine hydroxylation in the presence of benzoxazinones, leading to a derivative which was accumulated inside the vacuole.

One of the possible detoxication pathways for atrazine in corn corresponds to a chemical hydroxylation process. The aim of this work was to describe the mechanism of this reaction. Underin vitroexperimental conditions, a benzoxazinones mixture (10 mM) extracted from corn plantlets was able to transform 91% of atrazine (6 μM) into 2-hydroxyatrazine during a 24-h period of incubation at 25°C. This reaction was shown to be temperature-dependent; the half-life of atrazine was 67 h at 4°C, 90 min at 25°C, and only 30 min at 50°C. However, at this temperature a rapid degradation of the active benzoxazinones occurred. The pH value of the incubation medium was shown to influence greatly the hydroxylation rate of atrazine (no hydroxylation process at pH 9, a relatively low rate at pH 7, and a maximum one at pH 5.5). The presence of an organic solvent (ethanol or acetone) in the reaction medium was responsible for a large decrease in hydroxylation activity. In a water medium, an optimal rate was obtained when the benzoxazinones concentration was close to 10 mM (average rate of hydroxylation: 2 to 3.10−4nmol h−1nmol−1benzoxazinones). For concentration values lower than 1 mM, the rates remained very low. In the presence of 10 mM benzoxazinones, the hydroxylation rate appeared not to be saturable for concentrations in atrazine varying between 6 and 100 μM. The comparison of the hydroxylation rates obtained with purified benzoxazinones (DIMBOA, DIBOA, 2-monoglucosyl DIMBOA + 2-monoglucosyl DIBOA) suggested that the chemical reactivity of benzoxazinones toward atrazine involved the 4-N-OH of the heterocycle and not the 2-C-OH. This hypothesis was reinforced by the fact that the atrazine hydroxylating activity of DIMBOA or DIBOA remained unchanged even in the presence of AlCl3, (a chelator of the 2-OH group). The natural concentration of benzoxazinones in the vacuolar sap of corn seedlings (≥10 mM) and the pH of this solution (close to 5.5) contribute to explain the high rate of atrazine chemical hydroxylationin vivo.

The present work concerns atrazine absorption and metabolism by corn (Zea mays.) seedlings immersed in an aqueous medium in comparison with Acer pseudoplatanus cell cultures. At the point of equilibrium, the apparent concentration inside the A. pseudoplatanus cells (with a moderate lipid content: 0.17% of dry weight) was about twice that of the medium. This equilibrium was probably due to a simple partition process; part of the atrazine was dissolved in the cell water and reached the same concentration as in the external medium while the rest was concentrated inside the cellular lipids. The theoretical calculation of the lipid/water partition, taking into account the value of log P measured not with the lipids but with octanol (log P = 2.5), gave a value of 1.5 for concentration inside the plant material. Such an equilibrium, resulting from a partition process between water and lipids, was also obtained in non-living corn seedlings. In living seedlings, an over-concentration of radioactivity due to [ 14 C]atrazine derivatives was rapidly obtained inside roots and shoots giving concentrations respectively 7- and 12-fold higher than that of atrazine in the external medium. This was due to very rapid chemical transformation of atrazine into its hydroxy derivatives, especially hydroxyatrazine. This hydrolysis of atrazine in corn was due to the presence of high levels of benzoxazinone derivatives in corn seedling cells. The hydroxylated metabolites were able to concentrate in the cells very rapidly and were unable to diffuse freely into the external medium. As a consequence, this process facilitated the penetration of large quantities of atrazine which became rapidly hydroxylated, allowing therefore the passive penetration of atrazine to be further improved, since the concentration C 1 in the receiver compartment was always close to zero. The passive transfer of atrazine, following Fick's law: dq/dt = - Pa (C 0 -C 1 ), was therefore optimized.

This study investigated the impacts of an organochlorine (OC, γ-hexachlorocyclohexane and chlorobenzenes) mixture on microbial communities associated to Phragmites australis rhizosphere. Seventy-eight distinct colony morphotypes were isolated, cultivated and analysed by 16S rDNA sequence analysis. Toxicity tests confirmed sensitivity (e.g. Hevizibacter, Acidovorax) or tolerance (e.g. Bacillus, Aeromonas, Pseudomonas, Sphingomonas) of isolates. Rhizosphere analysis by pyrosequencing showed the microbial adaptation induced by OC exposure. Among the most abundant molecular operational taxonomic units, 80 % appeared to be tolerant (55 % opportunist, 25 % unaffected) and 20 % sensitive. P. australis rhizosphere exposed to OCs was dominated by phylotypes related to α-, β- and γ-Proteobacteria. Specific genera were identified which were previously described as chlorinated organic pollutant degraders: Sphingomonas sp., Pseudomonas sp., Devosia sp. and Sphingobium sp. P. australis could be suitable plants to maintain their rhizosphere active microbial population which can tolerate OCs and potentially improve the OC remediation process in part by biodegradation.

Mosquitoes are vectors of major human diseases, such as malaria, dengue or yellow fever. Because no efficient treatments or vaccines are available for most of these diseases, control measures rely mainly on reducing mosquito populations by the use of insecticides. Numerous biotic and abiotic factors are known to modulate the efficacy of insecticides used in mosquito control. Mosquito breeding sites vary from opened to high vegetation covered areas leading to a large ultraviolet gradient exposure. This ecological feature may affect the general physiology of the insect, including the resistance status against insecticides. In the context of their contrasted breeding sites, we assessed the impact of low-energetic ultraviolet exposure on mosquito sensitivity to biological and chemical insecticides. We show that several mosquito detoxification enzyme activities (cytochrome P450, glutathione S-transferases, esterases) were increased upon low-energy UV-A exposure. Additionally, five specific genes encoding detoxification enzymes (CYP6BB2, CYP6Z7, CYP6Z8, GSTD4, and GSTE2) previously shown to be involved in resistance to chemical insecticides were found over-transcribed in UV-A exposed mosquitoes, revealed by RT-qPCR experiments. More importantly, toxicological bioassays revealed that UV-exposed mosquitoes were more tolerant to four main chemical insecticide classes (DDT, imidacloprid, permethrin, temephos), whereas the bioinsecticide Bacillus thuringiensis subsp. israelensis (Bti) appeared more toxic. The present article provides the first experimental evidence of the capacity of low-energy UV-A to increase mosquito tolerance to major chemical insecticides. This is also the first time that a metabolic resistance to chemical insecticides is linked to a higher susceptibility to a bioinsecticide. These results support the use of Bti as an efficient alternative to chemical insecticides when a metabolic resistance to chemicals has been developed by mosquitoes.

Mixed pollution is a characteristic of many industrial sites and constructed wetlands. Plants possessing an enzymatic detoxifying system that is able to handle xenobiotics seems to be a viable option for the removal of mixed persistent contaminants such organochlorines (OCs: monochlorobenzene (MCB), 1,4-dichlorobenzene (DCB), 1,2,4-trichlorobenzene (TCB), γ-hexachlorocyclohexane (HCH)). In this study, Phragmites australis plants were exposed to sub-lethal concentrations of OCs (7 days), in single-exposure (0.8 to 10 mg l(-1)) and in mixture of OCs (0.2 mg l(-1) MCB + 0.2 mg l(-1) DCB + 2.5 mg l(-1) TCB + 0.175 mg l(-1) HCH). Studies were conducted on the detoxification phase II enzymes; glutathione S-transferases (GST), and glucosyltransferases (UGT). Measurements of GST and UGT activities revealed that OCs may be buffered by glutathione and glucose conjugation. There appeared to be a correlation between the effects on phase II enzymes and the degree of chlorination of the benzene ring with, for example, the greatest effects being obtained for HCH exposure. In the case of mixed pollution, the induction of some GST isoenzymes (CDNB, 35 % non-significant) and UGT (118 %) in leaves and the inhibition of phase II enzymes in the other organs were measured. UGTs appear to be key enzymes in the detoxification of OCs.

A general consensus that an increased logK(ow) led to an increase in xenobiotic uptake and bioaccumulation is accepted. In this study we compared the toxicokinetics of two chemically different xenobiotics, i.e. benzo[a]pyrene and fipronil in female green frogs. Surprisingly, the uptake rates and the bioconcentration factors (BCF) of the two contaminants were not predicted by their logK(ow). The uptake rates obtained were of the same order of magnitude for the two contaminants and the BCFs measured for fipronil were about 3-fold higher than those obtained for benzo[a]pyrene. Fipronil appeared to be more recalcitrant than benzo[a]pyrene to detoxification processes leading to the accumulation of sulfone-fipronil especially in the ovaries. This phenomenon may explain reproductive influence of this contaminant described in other studies. Detoxification processes, including metabolism and the excretion of pollutants, are of importance when considering their persistence in aquatic organisms and trying to quantify their risks.

Phragmites australis shows potential for the phytoremediation of chlorinated chemicals. Also there has been some attempt to determine the phytotoxic effects of organochlorines (OC). This study reports for lindane (HCH), monochlorobenzene (MCB), 1,4-dichlorobenzene (DCB) and 1,2,4-trichlorobenzene (TCB), a no-observed-effect-concentration (NOEC 7d ) that was 1000–300,000 times higher than environmental concentrations. Nevertheless, the combined OC mixture (NOEC 7d level of each congener) induced a synergistic toxic effect, causing a severe drop (70%) in chlorophyll concentration. The mixture 0.2 mg L −1 MCB + 0.2 mg L −1 DCB + 2.5 mg L −1 TCB + 0.175 mg L −1 HCH, that was 15 times more concentrated than environmental OC mixture, did not cause phytotoxicity during 21 days. Antioxidant enzymes were affected immediately after the start of exposure (3 days), but the plants showed no signs of stress thereafter. These data suggest that environmental OC mixtures do not pose a significant risk to P. australis .

A 7-day-exposure time experiment was designed to investigate the phytotoxicity of chlorobenzenes (CBs) on Zea mays seedlings, focusing on the growth and generation of oxidative stress. Significant growth inhibition (based on biomass gain) was observed for exposure to monochlorobenzene (MCB), dichlorobenzene (DCB) and trichlorobenzene (TCB) concentrations higher than 10 mg l(-1). It would seem that CBs inhibit cell division, since the mitotic index decreased for roots exposed to DCB at 80 mg l(-1) dose (8%) and to all the TCB concentrations tested (20% inhibition). CBs exposure resulting in an increase in the oxidative stress response in maize seedlings [reactive oxygen species like H(2)O(2), antioxidant enzymes (POD, GR), lipid peroxidation] correlated to the compound's degree of chlorination, where damage increasing with the number of chlorine atoms (MCBDCBTCB). This biological response was also dependent on the dose-exposure. Z. mays exposed to CBs at concentrations10 mg l(-1) did not induce sufficient oxidative damage to cause root cell death. Therefore, CBs at current environmental concentrations are unlikely to produce evident phytotoxic effects on Z. mays seedlings.

A crucial component for developing insect management strategies is the understanding of the ecological parameters involved in habitat selection by proliferating species. The key ecological drivers underlying habitat selection in the mosquito Coquillettidia sp. have been investigated in natura. Vegetation analysis suggested that the most suitable habitats were ponds with a high vegetation cover maintaining a high degree of humidity in the air. The optimal biotope for Coquillettidia was associated with the presence of larval host plants such as Typha sp., Phragmites sp., and Juncus sp. Water quality was also found to be a key factor in larval habitat distribution. The presence of larvae was significantly correlated with physico-chemical factors and the optimal water characteristics were neutral pH, low salt concentration, and a relatively low level of suspended particulate matter. A significant correlation was observed between chemical cues and the Coquillettidia distribution pattern. For instance, 2,6-di-tert-butyl-p-cresol was positively correlated to larval habitat, whereas high lauric acid and heptadecanoic acid concentrations may be limiting factors. This study underlines the fact that mosquito habitat selection is driven by a complex process based on discriminating levels of several ecological factors. Multivariate analysis helps understand such processes, which is this case will assist in managing expanding populations of a species that threatens human health.

Plants produce semio-chemicals that directly influence insect attraction and/or repulsion. Generally, this attraction is closely associated with herbivory and has been studied mainly under atmospheric conditions. On the other hand, the relationship between aquatic plants and insects has been little studied. To determine whether the roots of aquatic macrophytes release attractive chemical mixtures into the water, we studied the behaviour of mosquito larvae using olfactory experiments with root exudates. After testing the attraction on Culex and Aedes mosquito larvae, we chose to work with Coquillettidia species, which have a complex behaviour in nature and need to be attached to plant roots in order to obtain oxygen. This relationship is non-destructive and can be described as commensal behaviour. Commonly found compounds seemed to be involved in insect attraction since root exudates from different plants were all attractive. Moreover, chemical analysis allowed us to identify a certain number of commonly found, highly water-soluble, low-molecular-weight compounds, several of which (glycerol, uracil, thymine, uridine, thymidine) were able to induce attraction when tested individually but at concentrations substantially higher than those found in nature. However, our principal findings demonstrated that these compounds appeared to act synergistically, since a mixture of these five compounds attracted larvae at natural concentrations (0.7 nM glycerol

International audience; Seeds of sunflower plants coated with the fipronil C-14-insecticide were allowed to grow in the greenhouse. The distribution of the C-14-COM pounds was studied in each part of the plant after three months. After 83 days of culture small amounts of C-14-compounds were found in the inflorescence (0.6 parts per thousand of the seed deposit) which Were fipronil itself or its lipophilic or hydrophilic metabolites. The C-14-compounds were found in each part of the inflorescence (bracts, ray and disk florets containing pollen, akenes). The C-14-concentration in the xylem sap evaluated at this stage was much too low to explain the accumulated amount in the inflorescence. Under controlled conditions in a culture chamber, it was then demonstrated that a net phloem transfer of C-14-fipronil occurred from developed leaves to growing organs. This allowed us to suppose that a similar C-14-fipronil phloem transfer could occur toward the inflorescence during its formation. A quantitative evaluation suggests that most of the labeled. compounds at this stage were not coming from the leaves but from the roots and stem where storage compounds were hydrolyzed for sustaining inflorescence development.

International audience; In animals biotransformation and immune system are not totally independents, there are numerous functional interrelationships between these two systems. They are both implicated in the capacity of organisms to resist to a wide variety of environmental components such as viruses, bacteria and xenobiotics. It is known for a long time that the immune system functions as a physiologic system and interacts with all the other components of the organism including nervous or endocrine ones. In the same manner, the biotransformation system (especially the cytochrome P450 monooxygenases) is involved in the regulation of numerous hormone productions. In this way, many studies in mammals have revealed the possible interaction between immune and biotransformation systems. Among these interactions, the capacity of the activation of host defense mechanisms to down-regulate microsomal cytochrome P450 and the role of biotransformation system in the xenobiotic-mediated immunotoxicity have been underlined. Advances in the basic knowledge of fish immune and biotransformation systems should lead to a better understanding of the possible interactions between both systems and should improve fish health monitoring which is a crucial ecotoxicological goal. (C) 2008 Elsevier B.V. All rights reserved.

Effects of the broad-spectrum insecticide fipronil were investigated on a non-target insect living in the soil, the springtail Folsomia candida Willem. Fipronil induced a significant reduction in juvenile production (PNEC = 250 μg kg −1 dry soil), which seemed to be linked with an impact on the first stages of springtail development: juveniles and 7-day-old adults. These young organisms have a thinner integument, a smaller mass body and a weaker detoxification efficiency and were more sensitive than adults (14 days old) to fipronil and phenylpyrazole derivatives. Contact toxicity for juveniles was measured (LC 50 (96 h)) giving the following values: fipronil, 450 μg l −1 ; sulfone-fipronil, 430 μg l −1 ; sulfide-fipronil, 160 μg l −1 . F. candida organisms were able to avoid contaminated food because phenylpyrazoles decreased food appetency. However, F. candida could bioaccumulate fipronil through trans-tegumental penetration (BAF 96 h = 160) and its high biotransformation rate inside springtail bodies (1 ng fipronil metabolized day −1 individual −1 ) was suspected to increase this process. Under natural conditions, phenylpyrazoles risk assessment on springtails seems to be weak due to their capacity of avoiding high contaminated zones and their biochemical tolerance to this class of insecticides.

International audience; Seed-coating with the insecticide fipronil has been intensively used in sunflower cultivation to control soil pests such as wireworms. A research project was undertaken to determine the soil distribution of fipronil and of its main phenylpyrazole metabolites. Under agronomic conditions, the quantity of fipronil in the seed-coat (437 mu g/seed) decreased continuously during the cultivation period (3.9 mu g day(-1) during the first two months; 0.3 mu g day(-1) during the next four months). At the end of the cultivation period, 42% of all phenylpyrazole compounds remained in the seed-coat. Fipronil was poorly mobile in soil, and at the end of the cultivation period it was mostly concentrated in the soil layer close to the seed (3240 mu g k(-1) soil). Starting from the seed-coating, a fipronil concentration gradient was measured in the soil, up to a distance of I I cm from the seed. Degradation in the soil occurred at a moderate rate, probably due to the fact that water solubilization of the solid active ingredient present in the seed coating was rate limiting. Indeed, after 6 months of cultivation, only 51% of the fipronil seed-coating was found in the soil. about 7% having been absorbed by the sunflower plant. and 42% remaining in the seed coat. The predominant metabolites produced in the soil were sulfone-fipronil, sulfide-fipronil and amide-fipronil, which were produced at average rates of 5 mu g kg(-1) soil day(-1) 3 mu g ka(-1) soil day(-1) and 0.4 mu g kg(-1) soil day(-1), respectively. In contrast, the photoproduct, desulfinyl-fipronil, was barely detected. All phenylpyrazole compounds were poorly mobile, except for the amide derivative, which is devoid of insecticidal activity in marked contrast to the other metabolites. Furthermore, detectable soil contamination was limited to a zone of about 11 cm around the seed. (C) 2007 Elsevier Ltd. All rights reserved.

International audience; The resistance mechanism of vetiver (Chrysopogon zizanioides Nash) to atrazine was investigated to evaluate its potential for phytoremediation of environment contaminated with the herbicide. Plants known to metabolise atrazine rely on hydroxylation mediated by benzoxazinones, conjugation catalyzed by glutathione-S-transferases (GST) and dealkylation probably mediated by cytochromes P450. All three possibilities were explored in mature vetiver grown in hydroponics during this research project. Here we report on the role of glutathione-S-transferase in the detoxification of atrazine, as determined in vetiver leaf and root of 5-week- and 8-month-old plants grown in hydroponics. Fresh vetiver roots and leaves were cut to extract and study their GST activities toward 1-chloro-2,4-dinitrobenzene (CDNB) and atrazine, using HPLC to quantify the biosynthesis of atrazine conjugates. The global GST activity was three orders of magnitude higher than that of GST isoform able to conjugate atrazine. In vitro activities of conjugation of CDNB were similar in all root and leaf vetiver extracts, whereas activities on atrazine were only detected in leaf extracts. Entire vetiver plants exposed to C-14-atrazine were found to accumulate radioactivity at the tip of leaves under moderate transpiring conditions (75% humidity). Vetiver transformed atrazine mainly into polar compounds, identified as conjugates by TLC analyses. After 20 days of exposure, the proportion of atrazine and metabolites compared to the total penetrated radioactivity into plants was: 50% of conjugates, 28% of atrazine plus possible dealkylates and 22% of unidentified products. The maximum conjugates production was observed at the tip of leaves (29 nmol g(-1) fresh biomass), as compared to roots (6 nmol g(-1) fresh biomass). Altogether, these metabolic features indicate that conjugation to glutathione was a major metabolic pathway to detoxify atrazine in vetiver. (c) 2005 Elsevier B.V. All rights reserved.

International audience; Densely overgrown pre-alpine permanent aquatic habitats are overrun by the mosquito Coquillettidia (Coquillettidia) richiardii (Ficalbi) (Diptera: Culicidae). The invasive potential of this insect depends on the ability of its larvae to survive on the roots of emergent aquatic macrophytes. In order to characterize this particular ecological niche, which is out of reach for a direct investigation, environmental factors likely to influence the interaction between larvae and host plant roots were investigated using a simplified laboratory microcosm. Environmental light and oxygen concentrations appeared to be the main factors influencing larval attachment, a dark anoxic environment being significantly more favourable. Carbon dioxide produced by the root system of the host plant appeared to be an attractive cue for larval attachment. Knowledge of the hierarchy of these environmental factors may enable us to better understand the ecological traits of larval C. richiardii in deep water. With regard to their management, new ecological data are required to develop a long-term control strategy against Coquillettidia mosquitoes.

International audience; The phenylpyrazole insecticide, fipronil, is used in seed coating against Agriotes larvae, which infest mainly corn and sunflower. Coating the seeds of the cultivated plants with fipronil has proven its effectiveness against Agriotes populations. In the case of sunflower or even corn, the possible root uptake of this insecticide may lead to a toxic effect against pollinators such as honeybees. In the present report, the uptake and transport of fipronil inside the sunflower seedling was studied in the laboratory. In a first study, sunflower was cultivated on an aqueous medium containing fipronil. An intense root uptake of fipronil occurred, leading to a transport into leaves depending upon transpiration. In a second study, plants were cultivated on a soil in which fipronil was uniformly distributed. Under our soil conditions (20% organic carbon), the partition coefficient between soil and water (K-d) was found to be equal to 386 +/- 30. The average rate of fipronil transfer from soil water to seedlings was from 2 to 2.6 times lower than water transfer. During the 3 week experiment, 55% of recovered labeled compounds was in the parent form and 35% had been converted to lipophilic metabolites, with either a 4-CF3-SO2 or 4-CF3-S substituant, which are also very potent lipophilic insecticides. This paper suggests that the possible uptake of fipronil by sunflower seedlings under agronomic conditions is mainly controlled by the physicochemical characteristics of the seed-coating mixture.

International audience; Invasive mosquitoes are economic and sanitary concerns especially in Europe and America. Most work has emphasized the role of resistance [Berrada, S., Fournier, D., Cuany, A., Nguyen, TX, 1994. Identification of resistance mechanisms in a selected laboratory strain of Cacopsylla pyri (Homoptera: Psyllidae): altered acetylcholinesterases and detoxifying oxidases. Pesticide Biochemistry and Physiology 48, 41-47; Hemingway, J., Hawkes, N.J., McCarroll, L., Ranson, H., 2004. The molecular basis of insecticide resistance in mosquitoes. Insect Biochemistry and Molecular Biology 34, 653-665] to insecticides. Compounds acting on larval sensitivity to insecticides are not well studied and their action remains poorly understood. Among several residual chemicals in ecosystems, particularly in wetlands, we identified a possible interaction of an herbicide on larval resistance to an insecticide. Our work contributes to the global control of mosquito populations by identifying possible pathways of resistance to insecticides of these vectors. Resistance or tolerance to insecticide treatments might contribute to successful invasion by mosquitoes. Here we report an ecotoxicological approach to test the hypothesis of an indirect effect of atrazine on mortality of an invasive vector. A brief contact (48 h) between Aedes aegypti mosquito larvae and atrazine led to a modification of larval sensitivity to an insecticide: using atrazine as an inducer led to a decrease in the mortality of larvae treated with Bacillus thuringiensis var. israelensis (Bti). (c) 2006 Elsevier Ltd. All rights reserved.

International audience; Fipronil is a recently discovered insecticide of the phenylpyrazole series. It has a highly selective biochemical mode of action, which has led to its use in a large number of important agronomical, household, and veterinary applications. Previous studies have shown that, during exposure to light, fipronil is converted into a desulfurated derivative (desulfinyl-fipronil), which has slightly reduced insecticidal activity. In this study, the photodegradation of fipronil was studied in solution at low light intensities (sunlight or UV lamp). In addition to desulfinyl-fipronil, a large number of minor photoproducts were observed, including diversely substituted phenylpyrazole derivatives and aniline derivatives that had lost the pyrazole ring. Desulfinyl-fipronil itself was shown to be relatively stable under both UV light and sunlight, with only limited changes occurring in the substitution of the aromatic ring. Since this compound accumulated to levels corresponding to only 30-55% of the amount of fipronil degraded, it was concluded that one or more alternative pathways of photodegradation must be operating. On the basis of the structurally identified photoproducts, it is proposed that fipronil photodegradation occurs via at least two distinct pathways, one of which involves desulfuration at the 4-position of the pyrazole ring giving the desulfinyl derivative and the other of which involves a different modification of the 4-substituent, leading to cleavage of the pyrazole ring and the formation of aniline derivatives. The latter compounds do not accumulate to high levels and may, therefore, be degraded further. The ecological significance of these results is discussed, particularly with regard to the insecticidal activity of the photoproducts.

The resistance mechanism of vetiver (Chrysopogon zizanioides) to atrazine was investigated to evaluate its potential for phytoremediation of environment contaminated with the herbicide. Plants known to metabolise atrazine rely on hydroxylation mediated by benzoxazinones, conjugation catalyzed by glutathione-S-transferases and dealkylation probably mediated by cytochromes P450. All three possibilities were explored in mature vetiver grown in hydroponics during this research project. Here we report on the chemical role of benzoxazinones in the transformation of atrazine. Fresh vetiver roots and leaves were cut to extract and study their content in benzoxazinones known to hydroxylate atrazine, such as 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)- one (DIBOA), 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA) and their mono- and di-glucosylated forms. Identification of benzoxazinones was performed by thin layer chromatography (TLC) and comparison of retention factors (Rf) and UV spectra with standards: although some products exhibited the same Rf as standards, UV spectra were different. Furthermore, in vitro hydroxylation of atrazine could not be detected in the presence of vetiver extracts. Finally, vetiver organs exposed to [14C]-atrazine did not produce any significant amount of hydroxylated products, such as hydroxyatrazine (HATR), hydroxydeethylatrazine (HDEA), and hydroxy-deisopropylatrazine (HDIA). Altogether, these metabolic features suggest that hydroxylation was not a major metabolic pathway of atrazine in vetiver.

A corn seed dressing with the fungicide triticonazole at 760 nmol/seed prevents head smut disease. In resting seeds, the dressing treatment was followed by the penetration of 19% of the product, 9% inside the tegument and 7% inside the pedicel. In growing seedlings, the inner content increased in the storage organs (endosperm + scutellum) as well as in the growing organs. The partition lipophilic phase/water certainly explains the high apparent fungicide concentration progressively reached inside endosperm and scutellum. However, no important transfer of fungicide from these organs to the growing parts seems to occur. It appears therefore that the fungicide transfer from the coating to the roots mostly occurs through dissolution of the product in the surrounding soil water and through root absorption. The efficient fungicide concentration inside the meristem is likely to be obtained during the early stages of development.

BackgroundMalaria was endemic in the Rhône-Alpes area of eastern France in the 19thcentury and life expectancy was particularly shortened in Alpine valleys. This study was designed to determine how the disease affected people in the area and to identify the factors influencing malaria transmission.MethodsDemographic data of the 19thcentury were collected from death registers of eight villages of the flood-plain of the river Isère. Correlations were performed between these demographic data and reconstructed meteorological data. Archive documents from medical practitioners gave information on symptoms of ill people. Engineer reports provided information on the hydraulic project developments in the Isère valley.ResultsDescription of fevers was highly suggestive of endemic malaria transmission in the parishes neighbouring the river Isère. The current status of anopheline mosquitoes in the area supports this hypothesis. Mean temperature and precipitation were poorly correlated with demographic data, whereas the chronology of hydrological events correlated with fluctuations in death rates in the parishes.ConclusionNowadays, most of the river development projects involve the creation of wet areas, enabling controlled flooding events. Flood-flow risk and the re-emergence of vector-borne diseases would probably be influenced by the climate change. The message is not to forget that human disturbance of any functioning hydrosystem has often been linked to malaria transmission in the past.

In plant tissues the extracellular environment or apoplast, incorporating the cell wall, is a highly dynamic compartment with a role in many important plant processes including defence, development, signalling and assimilate partitioning. Soluble apoplast proteins from Arabidopsis thaliana, Triticum aestivum and Oryza sativa were separated by two-dimensional electrophoresis. The molecular weights and isoelectric points for the dominant proteins were established prior to excision, sequencing and identification by matrix-assisted laser-desorption ionisation time of flight mass spectrometry (MALDI - TOF MS). From the selected spots, 23 proteins from O. sativa and 25 proteins from A. thaliana were sequenced, of which nine identifications were made in O. sativa (39%) and 14 in A. thaliana (56%). This analysis revealed that: (i) patterns of proteins revealed by two-dimensional electrophoresis were different for each species indicating that speciation could occur at the level of the apoplast, (ii) of the proteins characterised many belonged to diverse families reflecting the multiple functions of the apoplast and (iii), a large number of the apoplast proteins could not be identified indicating that the majority of extracellular proteins are yet to be assigned. The principal proteins identified in the aqueous matrix of the apoplast were involved in defence, i.e. germin-like proteins or glucanases, and cell expansion, i.e. β-D-glucan glucohydrolases. This study has demonstrated that proteomic analysis can be used to resolve the apoplastic protein complement and to identify adaptive changes induced by environmental effectors.

In wetlands, dramatic decline in amphibian populations have been described worldwide since the 80s. Despite numerous studies suggesting that amphibians are highly sensitive to cumulative anthropogenic stresses, the role played by endocrine disruptors in the decline of amphibian populations remains unclear. Among the endocrine disruptors contaminating wetlands, benzo[a]pyrene (BaP) and triclosan (TCS) are recurrently found. In this work, we studied the physiological response of Xenopus tropicalis exposed to environmentally realistic concentrations of BaP and TCS during a short-term (24 hours) and long-term (from tadpole to mature adult) period. By combining a high throughput transcriptomic approach and a characterization of cellular and physiological modifications, we showed that BaP, TCS and their mixture disrupt overall liver physiology highlighted by insulin resistance-like and non-alcoholic fatty liver disease (NAFLD)-like phenotypes together with hepatotoxicity due to the impairment of lipid metabolism. Additionally to direct metabolic impact observed on exposed individuals, the studied endocrine disruptors affected their fitness and their progeny development. Altogether, our observations bring new insights into the role plays by chronic contamination of wetlands on amphibian population decline., Dans les zones humides, un déclin dramatique des populations d’amphibiens a été observé au niveau mondial depuis les années 80. Malgré de nombreuses études suggérant que les amphibiens sont très sensibles aux pressions anthropiques cumulées, le rôle joué par les perturbateurs endocriniens dans le déclin de leurs populations reste incertain. Parmi les perturbateurs endocriniens contaminants les zones humides, le benzo[a]pyrène (BaP) et le triclosan (TCS) sont couramment retrouvés. Au cours de ce travail, nous avons étudié la réponse physiologique de xénopes (Xenopus tropicalis) exposés à court terme (24 heures) et à long terme (du têtard à l’adulte mature) au BaP et au TCS à des concentrations réalistes d’un point de vue environnemental. En combinant une approche transcriptomique à haut débit et une caractérisation des modifications cellulaires et physiologiques, nous avons mis en évidence que le BaP, le TCS et leur mélange perturbent la physiologie globale du foie. Ce trouble est caractérisé par un phénotype semblable à de l’insulino-résistance et à une stéatopathie non alcoolique (NAFLD) associé à une hépatotoxicité médiée par une altération du métabolisme lipidique. Outre les effets directs sur le métabolisme des individus exposés, il apparaît que les perturbateurs endocriniens étudiés affectent également le succès reproducteur de ces individus et le développement de leur descendance. Prises dans leur ensemble, nos observations apportent ainsi des débuts de réponse quant aux rôles de la contamination chronique des milieux sur le déclin des populations d’amphibiens.

Human activities lead to diffuse pollution causing damages to the ecosystem. To avoid major disturbances such as biodiversity loss or contamination of trophic chains by pollutants it is necessary to restore these ecosystems. The classical techniques used in depollution are expensive, reduce soil fertility and have a negative effect on ecosystem functionality. In contrast, the use of plants to clean up soils called phytoremediation seems to be a more effective solution. However, it needs to be improved because many biological mechanisms remain unexplained. The originality of our work is to study the functionality of the rhizosphere of maize (Zea mays) exposed to organochlorine pesticides (OCPs), lindane and chlordecone, banned in 1998 and 1993 respectively and persistent in the environment. This study will be conducted in the presence or absence of microorganisms to clarify the relationships between microorganisms and plant matrices. In this study, the mechanisms involved in the phytotoxicity of OCPs in root cells were analyzed. The cytotoxicity was dose-dependent and showed effects on the cell cycle (induction of endoreduplication and level of ploidy) and on cell death (induction of ROS, cytosolic Ca2+, caspase-3-like, apoptosis) under higher doses of exposure (particular case of former industrial sites). Lower exposures usually detected in the environment showed great disturbances in the root metabolome. These changes in sugars, organic acids, amino acids and lipids syntheses could be induced by oxidative stress provided by OCPs. Moreover, metabolome changes might cause modifications in root exudate composition which is involved in plant-microbe relationships. Ours results demonstrate that the overall rhizosphere functionality (resource allocation, carbon and nitrogen contents and microorganism's catabolism) was not disturbed by OCPs long-term exposure. Finally, we demonstrated rhizosphere positive impact on uptake of OCPs by Zea mays. Lindane seems to be partially mineralized by rhizospheric microorganisms. Then, these produced metabolites were uptaken by roots where they were bioconcentrated. These findings highlighted the rhizosphere adaptation to chemical pressure by OCPs and showed the good rhizosphere functionality despite of the OCPs contamination.; L'activité humaine est responsable de pollutions diffuses des sols entrainant des dommages sur l'écosystème. Afin d'éviter des déséquilibres importants comme la diminution de la biodiversité ou bien la contamination des chaînes trophiques par des polluants, il est nécessaire de restaurer les écosystèmes. Les différentes techniques utilisées à l'heure actuelle sont couteuses, diminuent la fertilité du sol et ont un effet négatif sur la fonctionnalité des écosystèmes. A contrario, la phytoremédiation ou dépollution grâce aux plantes, apparaît comme une solution digne d'intérêt. Néanmoins, elle nécessite d'être améliorée puisque de nombreux mécanismes restent inexpliqués. L'originalité de notre travail est d'étudier la fonctionnalité de la rhizosphère du maïs (Zea mays) exposée à des pesticides organochlorés (OCPs), le lindane et la chlordécone, interdits respectivement en 1998 et 1993 et persistants dans l'environnement. Cette étude a été réalisée en présence ou absence de microorganismes afin de préciser les mécanismes mis en jeux par les microorganismes et les matrices végétales. Ce travail a mis en évidence les mécanismes impliqués dans la phytotoxicité des deux organochlorés sur les cellules racinaires. Les réponses cellulaires sont dose-dépendantes et montrent un effet des OCPs sur le cycle cellulaire (induction de l'endoréplication et de la ploïdie) et la mort cellulaire (induction de ROS, du calcium cytosolique, des caspase-3-like, de l'apoptose) lors d'expositions extrêmes (correspondant à des cas particuliers comme les friches industrielles). A de plus faibles expositions ayant une réalité environnementale, les racines exposées montrent une perturbation importante de leur métabolome primaire. Ces modifications mesurées sur la production des sucres, des acides organiques, des acides aminées et des lipides peuvent être induites par le stress oxydant produit par les OCPs. Par ailleurs, de tels changements dans le métabolome peuvent provoquer une modification de la composition des exsudats racinaires, jouant sur la relation plante/microorganismes de la rhizosphère. Nos résultats montrent que la fonctionnalité globale de la rhizosphère (allocation des ressources en carbone et azote, catabolisme des microorganismes) n'est pas modifiée sur le long terme en présence des OCPs. Enfin, nous avons démontré l'implication de la rhizosphère (rétention/métabolisation des OCPs) sur l'absorption des OCPs par Zea mays. Le lindane semble être en partie minéralisé par la microflore rhizosphèrique puis les métabolites libérés sont absorbés par les racines, où ils sont majoritairement bioconcentrés. Ces connaissances fondamentales mettent en évidence l'adaptation de la rhizosphère à la pression chimique des OCPs et montrent que la rhizosphère reste fonctionnelle en présence de matrices contaminées par les OCPs.

Human activities lead to diffuse pollution causing damages to the ecosystem. To avoid major disturbances such as biodiversity loss or contamination of trophic chains by pollutants it is necessary to restore these ecosystems. The classical techniques used in depollution are expensive, reduce soil fertility and have a negative effect on ecosystem functionality. In contrast, the use of plants to clean up soils called phytoremediation seems to be a more effective solution. However, it needs to be improved because many biological mechanisms remain unexplained. The originality of our work is to study the functionality of the rhizosphere of maize (Zea mays) exposed to organochlorine pesticides (OCPs), lindane and chlordecone, banned in 1998 and 1993 respectively and persistent in the environment. This study will be conducted in the presence or absence of microorganisms to clarify the relationships between microorganisms and plant matrices. In this study, the mechanisms involved in the phytotoxicity of OCPs in root cells were analyzed. The cytotoxicity was dose-dependent and showed effects on the cell cycle (induction of endoreduplication and level of ploidy) and on cell death (induction of ROS, cytosolic Ca2+, caspase-3-like, apoptosis) under higher doses of exposure (particular case of former industrial sites). Lower exposures usually detected in the environment showed great disturbances in the root metabolome. These changes in sugars, organic acids, amino acids and lipids syntheses could be induced by oxidative stress provided by OCPs. Moreover, metabolome changes might cause modifications in root exudate composition which is involved in plant-microbe relationships. Ours results demonstrate that the overall rhizosphere functionality (resource allocation, carbon and nitrogen contents and microorganism's catabolism) was not disturbed by OCPs long-term exposure. Finally, we demonstrated rhizosphere positive impact on uptake of OCPs by Zea mays. Lindane seems to be partially mineralized by rhizospheric microorganisms. Then, these produced metabolites were uptaken by roots where they were bioconcentrated. These findings highlighted the rhizosphere adaptation to chemical pressure by OCPs and showed the good rhizosphere functionality despite of the OCPs contamination., L'activité humaine est responsable de pollutions diffuses des sols entrainant des dommages sur l'écosystème. Afin d'éviter des déséquilibres importants comme la diminution de la biodiversité ou bien la contamination des chaînes trophiques par des polluants, il est nécessaire de restaurer les écosystèmes. Les différentes techniques utilisées à l'heure actuelle sont couteuses, diminuent la fertilité du sol et ont un effet négatif sur la fonctionnalité des écosystèmes. A contrario, la phytoremédiation ou dépollution grâce aux plantes, apparaît comme une solution digne d'intérêt. Néanmoins, elle nécessite d'être améliorée puisque de nombreux mécanismes restent inexpliqués. L'originalité de notre travail est d'étudier la fonctionnalité de la rhizosphère du maïs (Zea mays) exposée à des pesticides organochlorés (OCPs), le lindane et la chlordécone, interdits respectivement en 1998 et 1993 et persistants dans l'environnement. Cette étude a été réalisée en présence ou absence de microorganismes afin de préciser les mécanismes mis en jeux par les microorganismes et les matrices végétales. Ce travail a mis en évidence les mécanismes impliqués dans la phytotoxicité des deux organochlorés sur les cellules racinaires. Les réponses cellulaires sont dose-dépendantes et montrent un effet des OCPs sur le cycle cellulaire (induction de l'endoréplication et de la ploïdie) et la mort cellulaire (induction de ROS, du calcium cytosolique, des caspase-3-like, de l'apoptose) lors d'expositions extrêmes (correspondant à des cas particuliers comme les friches industrielles). A de plus faibles expositions ayant une réalité environnementale, les racines exposées montrent une perturbation importante de leur métabolome primaire. Ces modifications mesurées sur la production des sucres, des acides organiques, des acides aminées et des lipides peuvent être induites par le stress oxydant produit par les OCPs. Par ailleurs, de tels changements dans le métabolome peuvent provoquer une modification de la composition des exsudats racinaires, jouant sur la relation plante/microorganismes de la rhizosphère. Nos résultats montrent que la fonctionnalité globale de la rhizosphère (allocation des ressources en carbone et azote, catabolisme des microorganismes) n'est pas modifiée sur le long terme en présence des OCPs. Enfin, nous avons démontré l'implication de la rhizosphère (rétention/métabolisation des OCPs) sur l'absorption des OCPs par Zea mays. Le lindane semble être en partie minéralisé par la microflore rhizosphèrique puis les métabolites libérés sont absorbés par les racines, où ils sont majoritairement bioconcentrés. Ces connaissances fondamentales mettent en évidence l'adaptation de la rhizosphère à la pression chimique des OCPs et montrent que la rhizosphère reste fonctionnelle en présence de matrices contaminées par les OCPs.