The objective was to describe and model varia- tion patterns in individual fish responses to contaminants among estuaries, season and gender. Two hundred twenty- seven adult European flounders were collected in two sea- sons (winter and summer) in four estuaries along the Bay of Biscay (South West France), focusing on a pristine system (the Ster), vs. three estuaries displaying contrasted levels of contaminants (the Vilaine, Loire and Gironde). Twenty-three variables were measured by fish, considering the load of contaminants (liver metals, liver and muscle persistent organic pollutants, muscle polycyclic aromatic hydrocar- bons); the gene expression (Cyt C oxydase, ATPase, BHMT, Cyt P450 1A1, ferritin); the blood genotoxicity (Comet test); and liver histology (foci of cellular alteration–tumour, steatosis, inflammation, abnormal glycogen storage). Ca- nonical redundancy analysis (RDA) was used to model these variables using gender, season and estuary of origin as explanatory variables. The results underlined the homo- geneity of fish responses within the pristine site (Ster) and more important seasonal variability within the three contam- inated systems. The complete model RDA was significant and explained 35 % of total variance. Estuary and season respectively explained 30 and 5 % of the total independent variation components, whilst gender was not a significant factor. The first axis of the RDA explains nearly 27 % of the total variance and mostly represents a gradient of contami- nation. The links between the load of contaminants, the expression of several genes and the biomarkers were ana- lysed considering different levels of chemical stress and a possible multi-stress, particularly in the Vilaine estuary.

International audience | Pollinators have to cope with a wide range of stressful, not necessarily lethal factors limiting their performance and the ecological services they provide. Among these stressors are pesticides, chemicals that are originally designed to target crop-harming organisms but that also disrupt various functions in pollinators, including flight, communication, orientation and memory. Although all these functions are crucial for reproductive individuals when searching for mates or nesting places, it remains poorly understood how pesticides affect reproduction in pollinators. In this study, we investigated how a widely used fungicide, boscalid, affects reproduction in honey bees (Apis mellifera), an eusocial insect in which a single individual, the queen, fulfills the reproductive functions of the whole colony. Boscalid is a succinate dehydrogenase inhibitor (SDHI) fungicide mainly used on rapeseed flowers to target mitochondrial respiration in fungi but it is also suspected to disrupt foraging-linked functions in bees. We found that immature queen exposure to sublethal, field relevant doses of boscalid disrupted reproduction, as indicated by a dramatic increase in queen mortality during and shortly after the nuptial flights period and a decreased number of spermatozoa stored in the spermatheca of surviving queens. However, we did not observe a decreased paternity frequency in exposed queens that successfully established a colony. Queen exposure to boscalid had detrimental consequences on the colonies they later established regarding brood production, Varroa destructor infection and pollen storage but not nectar storage and population size. These perturbations at the colony-level correspond to nutritional stress conditions, and may have resulted from queen reduced energy provisioning to the eggs. Accordingly, we found that exposed queens had decreased gene expression levels of vitellogenin, a protein involved in egg-yolk formation. Overall, our results indicate that boscalid decreases honey bee queen reproductive quality, thus supporting the need to include reproduction in the traits measured during pesticide risk assessment procedures.

Partitioning tissue metal concentration into subcellular compartments relecting 'toxicologically available'pools may provide good descriptors of the toxicological efects of metals on organisms. Here we investigatedthe relationships between internal compartmentalization of Cd, Pb and Zn and biomarker responses in a model soil organism: the earthworm. The aim of this study was to identify metal fractions reflecting the toxic pressure in an endogeic, naturally occurring earthworm species (Aporrectodea caliginosa) exposed torealistic field-contaminated soils.After a 21 days exposure experiment to 31 field contaminated soils, Cd, Pb and Zn concentrationsin earthworms and in three subcellular fractions (cytosol, debris and granules) were quantified. Differentbiomarkers were measured: the expression of a metallothionein gene (mt), the activity of catalase (CAT) andof glutathione-s-transferase (GST), and the protein, lipid and glycogen reserves. Biomarkers were furthercombined in an integrated biomarker index (IBR).The subcellular fractionation provided better predictors of biomarkers than the total internal contentshence supporting its use when assessing toxicological bioavailability of metals to earthworms. The mostsoluble internal pools of metals were not always the best predictors of biomarker responses. metallothioneinexpression responded to increasing concentrations of Cd in the insoluble fraction (debris + granules). Proteinand glycogen contents were also mainly related to Cd and Pb in the insoluble fraction. On the other hand,GST activity was better explained by Pb in the cytosolic fraction. CAT activity and lipid contents variationswere not related to metal subcellular distribution. The IBR was best explained by both soluble and insolublefractions of Cd and Pb.This study further extends the scope of mt expression as a robust and specific biomarker in an ecologicallyrepresentative earthworm species exposed to field-contaminated soils. The genetic lineage of the individuals,assessed by DNA barcoding with cytochrome c oxidase subunit I, did not inuence mt expression.

Eisenia andrei earthworms were exposed for 7 and 14 days to six samples of soil taken from around an abandoned lead (Pb) mine and characterized by different levels of metal contamination (S6-S1, this latter being the most contaminated soil). The organisms were analyzed for metal bioaccumulation and for biological parameters as biomarkers of stress (lysosomal membrane stability; lipofuscin lysosomal content; lysosomal/cytoplasmic volume ratio) and genotoxicity (Micronucleus frequency). Chemical analysis showed the loads of Pb, Cd, Zn, and Cu in the worms following exposure. Among the stress biomarkers, lysosomal membrane stability was significantly affected in the coelomocytes of the earthworms exposed already 7 days to different contaminated soils. Organisms exposed for 14 days to S1 showed in the cells of the chloragogenous tissue, a particularly relevant increase in lipofuscin, a biomarker of oxidative stress, and an increase in the lysosome/cytoplasm volume ratio, indicating stressful condition at the tissue level. Moreover, in the same conditions, a decrease in total body weight was observed. At the longer exposure time, the coelomocytes of worms exposed to S1, S2, and S3 (soils with higher metal concentrations) showed a significant increase in micronuclei (MNi) frequency. Expressions of the P21 and topoisomerase genes, which are involved in DNA repair, showed significant up-regulation in the cells of worms exposed to S1, S2, S3, S4 and to a less extend S6. This may indicate that the worms were only able to successfully reduce the level of DNA damage in S4 and S5 if considering MN frequency data. The biomarker data was integrated by the Earthworm Expert System, allowing an objective interpretation of the complex biological data and clearly defining the areas in which the presence of chemicals is toxic for the edaphic organisms.

International audience | Because they are widely used, copper oxide nanoparticles (CuO NPs) are likely to enter the aquatic environment and then reach the sediment. We have examined the effect of CuO NPs in the freshwater endobenthic bivalve Corbicula fluminea. Some previous studies have investigated effects at biochemical and physiological levels, but molecular endpoints are still poorly studied despite they are sensitive in early detection of NPs effect. In the present study, we have investigated short-term effects (96 h) of CuO NP (12, 30 nm; 0, 20 and 100 mg/L) using molecular endpoints as well as more conventional biochemical and physiological markers. The expression of antioxidant (CuZnSOD, MnSOD, Cat, Se-GPx, Trxr) and antitoxic (GST-Pi, HSP70, MT, Pgp, MRP1) related genes was measured at the mRNA level while anti-oxidant (SOD, TAC) and antitoxic (GST, ACP) defenses, energetic reserves and metabolism (ETS, Tri, LDH), and cellular damages (LPO) were assessed using a biochemical approach. The filtration rate measured at 96 h provided information at the physiological scale. Gene expression and filtration rate were responsive to CuO NPs but the effects differed according to the NP size. The results suggest that defense mechanisms may have been set up following 30 nm-NP exposure. The response to 12 nm-NP was lower but still showed that exposure to 12 nm-NP led to activation of cellular elimination mechanisms. The lowering of the filtration rate may have protected the organisms from the contamination. However, this raised the question of further repercussions on organism biology. Together, the results (i) indicate that CuO NP may exert effects at different levels even after a short-term exposure and (ii) point out the precocity of molecular response.

Understanding of aquaporins (AQPs) facilitating the transport of water and many other small solutes including metalloids like silicon (Si) and arsenic (As) is important to develop stress tolerant cultivars. In the present study, 40 AQPs were identified in the genome of pigeonpea (Cajanus cajan), a pulse crop widely grown in semi-arid region and areas known to affected with heavy metals like As. Conserved domains, variation at NPA motifs, aromatic/arginine (ar/R) selectivity filters, and pore morphology defined here will be crucial in predicting solute specificity of pigeonpea AQPs. The study identified CcNIP2-1 as an AQP predicted to transporter Si (beneficial element) as well as As (hazardous element). Further Si quantification in different tissues showed about 1.66% Si in leaves which confirmed the predictions. Furthermore, scanning electron microscopy showed a higher level of Si accumulation in trichomes on the leaf surface. A significant alleviation in level of As, Sb and Ge stress was also observed when these heavy metals were supplemented with Si. Estimation of relative water content, H₂O₂, lipid peroxidation, proline, total chlorophyll content and other physiological parameters suggested Si derived stress tolerance. Extensive transcriptome profiling under different developmental stages from germination to senescence was performed to understand the tissue-specific regulation of different AQPs. For instance, high expression of TIP3s was observed only in reproductive tissues. Co-expression network developed using transcriptome data from 30 different conditions and tissues, showed interdependency of AQPs. Expression profiling of pigeonpea performed using real time PCR showed differential expression of AQPs after Si supplementation. The information generated about the phylogeny, distribution, molecular evolution, solute specificity, and gene expression dynamics in article will be helpful to better understand the AQP transport system in pigeonpea and other legumes.

Phenanthrene (PHE) is widely distributed, and it can cause genotoxicity in humans by interacting with enzymes in the body. A current challenge for PHE bioremediation is the inhibitory effect of biotoxic intermediates on bacterial growth. Notably, the aerobic biotransformation processes for PHE in the presence of sophorolipids have been poorly studied. Here, a PHE-degrading strain was isolated from sediments and identified as Pseudomonas stutzeri and named LSH-PAH1. It was observed that 1-naphthol (a biotoxic substance that can inhibit strain growth) was produced during the PHE metabolism process of LSH-PAH1. The biodegradation ratio increased from 21.4% to 91.7% within 48 h after the addition of sophorolipids. Unexpectedly, this addition accelerated the metabolic process for 1-naphthol rather than causing its accumulation. The cometabolism of 1-naphthol and sophorolipids alleviated the biotoxic effects for the strain, which was verified by gene expression analysis. We identified a new PHE-degrading strain and provided a mechanism for PHE biodegradation using LSH-PAH1 with the addition of sophorolipids, which provides a reference for practical applications of the bioremediation of PHE and study of the cometabolism of biotoxic intermediates.

Arsenic (As) and cadmium (Cd), two major carcinogenic heavy metals, enters into human food chain by the consumption of rice or rice-based food products. Both As and Cd disturb plant-nutrient homeostasis and hence, reduces plant growth and crop productivity. In the present study, As/Cd modulated responses were studied in non-basmati (IR-64) and basmati (PB-1) rice varieties, at physiological, biochemical and transcriptional levels. At the seedling stage, PB-1 was found more sensitive than IR-64, in terms of root biomass; however, their shoot phenotype was comparable under As and Cd stress conditions. The ionomic data revealed significant nutrient deficiencies in As/Cd treated-roots. The principal component analysis identified NH₄⁺ as As-associated key macronutrient; while, NH₄⁺/NO₃⁻ and K⁺ was majorly associated with Cd mediated response, in both IR-64 and PB-1. Using a panel of 21 transporter gene expression, the extent of nutritional deficiency was ranked in the order of PB-1(As)<IR-64(As)<PB-1(Cd)<IR-64(Cd). A feed-forward model is proposed to explain nutrient deficiency induced de-regulation of gene expression, as observed under Cd-treated IR-64 plants, which was also validated at the level of sulphur metabolism related enzymes. Using urea supplementation, as nitrogen-fertilizer, significant mitigation was observed under As stress, as indicated by 1.018- and 0.794-fold increase in shoot biomass in IR-64 and PB-1, respectively compared to that of control. However, no significant amelioration was observed in response to supplementation of urea under Cd or potassium under As/Cd stress conditions. Thus, the study pinpointed the relative significance of various macronutrients in regulating As- and Cd-tolerance and will help in designing suitable strategies for mitigating As and/or Cd stress conditions.

The intensification of anomalous events of seawater warming and the co-occurrence with local anthropogenic stressors are threatening coastal marine habitats, including seagrasses, which form extensive underwater meadows. Eutrophication highly affects coastal environments, potentially summing up to the widespread effects of global climate changes. In the present study, we investigated for the first time in seagrasses, the transcriptional response of different plant organs (i.e., leaf and shoot apical meristem, SAM) of the Mediterranean seagrass Posidonia oceanica growing in environments with a different history of nutrient enrichment. To this end, a mesocosm experiment exposing plants to single (nutrient enrichment or temperature increase) and multiple stressors (nutrient enrichment plus temperature increase), was performed. Results revealed a differential transcriptome regulation of plants under single and multiple stressors, showing an organ-specific sensitivity depending on plants' origin. While leaf tissues were more responsive to nutrient stress, SAM revealed a higher sensitivity to temperature treatments, especially in plants already impacted in their native environment. The exposure to stress conditions induced the modulation of different biological processes. Plants living in an oligotrophic environment were more responsive to nutrients compared to plants from a eutrophic environment. Evidences that epigenetic mechanisms were involved in the regulation of transcriptional reprogramming were also observed in both plants’ organs. These results represent a further step in the comprehension of seagrass response to abiotic stressors pointing out the importance of local pressures in a global warming scenario.

Volatile organic compounds (VOCs) promote cyanobacteria dominating eutrophicated waters, with aquatic plant decrease and even disappearance. To uncover the toxic mechanism of cyanobacterial VOCs on aquatic plants, we investigated the growth, photosynthetic pigment levels, photosynthetic abilities and related gene expression in duckweed treated with β-cyclocitral and β-ionone, 2 main components in the VOCs. The levels of chlorophylls and carotenoids gradually declined with raising the concentration of the 2 compounds and prolonging the treatment time. Their decline should result from the down-regulation of 8 genes associated with photosynthetic pigment biosynthesis and up-regulation of 2 genes involved in carotenoid degradation. The reduction was also found in the photosystem II (PSII) efficiency and O₂ evolution rate, which should result from the lowered photosynthetic pigment levels and down-regulation of 38 genes related with photosynthetic process. The frond numbers, total frond area and fresh weight gradually decreased with raising the 2 compound concentration, which may result from the lowered photosynthetic abilities as well as down-regulated expression of 7 genes associated with growth-promoting hormone biosynthesis and signal transduction. It can be speculated that cyanobacterial VOCs may poison aquatic plants by lowering the photosynthesis and growth through altering related gene expression.