Zinc Affects Differently Growth, Photosynthesis, Antioxidant Enzyme Activities and Phytochelatin Synthase Expression of Four Marine Diatoms

Zinc-supplementation (20 μM) effects on growth, photosynthesis, antioxidant enzyme activities (superoxide dismutase, ascorbate peroxidase, catalase), and the expression of phytochelatin synthase gene were investigated in four marine diatoms (Amphora acutiuscula, Nitzschia palea, Amphora coffeaeformis and Entomoneis paludosa). Zn-supplementation reduced the maximum cell density. A linear relationship was found between the evolution of gross photosynthesis and total chlorophyll content. The Zn treatment decreased the electron transport rate except in A. coffeaeformis and in E. paludosa at high irradiance. A linear relationship was found between the efficiency of light to evolve oxygen and the size of the light-harvesting antenna. The external carbonic anhydrase activity was stimulated in Zn-supplemented E. paludosa but was not correlated with an increase of photosynthesis. The total activity of the antioxidant enzymes did not display any clear increase except in ascorbate peroxidase activity in N. palea. The phytochelatin synthase gene was identified in the four diatoms, but its expression was only revealed in N. palea, without a clear difference between control and Zn-supplemented cells. Among the four species, A. paludosa was the most sensitive and A. coffeaeformis, the most tolerant. A. acutiuscula seemed to be under metal starvation, whereas, to survive, only N. palea developed several stress responses

Réponse du peuplier au déficit hydrique

ORLEANS-BU Sciences (452342104) / SudocSudocFranceF

The impact of transposable elements on eukaryotic genomes: From genome size increase to genetic adaptation to stressful environments

International audienceTransposable elements (TEs) are present in roughly all genomes. These mobile DNA sequences are able to invade genomes and their impact on genome evolution is substantial. The mobility of TEs can induce the appearance of deleterious mutations, gene disruption and chromosome rearrangements, but transposition activity also has positive aspects and the mutational activities of TEs contribute to the genetic diversity of organisms. This short review aims to give a brief overview of the impact TEs may have on animal and plant genome structure and expression, and the relationship between TEs and the stress response of organisms , including insecticide resistance

Interactions between polystyrene nanoparticles and Chlamydomonas reinhardtii monitored by infrared spectroscopy combined with molecular biology

International audienceFor several decades, use of nanoparticles (NP) on a global scale has been generating new potential sources of organism disruption. Recent studies have shown that NP can cause modifications on the biochemical macromolecular composition of microalgae and raised questions on the toxicity of plastic particles, which are widespread in the aquatic environment. Polystyrene (PS) particles are among the most widely used plastics in the world. In our experimentation, a combined approach of infrared spectroscopy and molecular biology (real-time PCR) has been applied in order to better apprehend the consequences of interactions between Chlamydomonas reinhardtii, freshwater microalgae and PS NP. Two references have been used, nitrogen deprivation -a well-documented stressor-, and gold nanoparticles (Au-NP). As regards biochemical composition, our experiments show a differing microalga response, according to the NP to which they have been exposed. Results with infrared spectroscopy and gene expression methods are consistent and illustrate variation among several carbohydrates (galactose…). Furthermore, PS-NP seem to react in the same direction as nitrogen limitation, thereby supporting the hypothesis that PS-NP can induce response mechanisms to environmental changes in microalgae. This study highlighted the interest of combining infrared spectroscopy and gene expression as means of monitoring microalgae response to nanoplastics

Current methods to monitor microalgae-nanoparticle interaction and associated effects

International audienceWidespread use of nanoparticles for different applications has diffused their presence in the environment, particularly in water. Many studies have been conducted to evaluate their effects on aquatic organisms. Microalgae are at the base of aquatic trophic chains. These organisms which can be benthic or pelagic, meaning that they can enter into interaction with all kinds of particulate materials whatever their density, and constitute an interesting model study. The purpose of this review was to gather more than sixty studies on microalgae exposure to the different nanoparticles that may be present in the aquatic environment. After a brief description of each type of nanoparticle (metals, silica and plastic) commonly used in ecotoxicological studies, techniques to monitor their properties are presented. Then, different effects on microalgae resulting from interaction with nanoparticles are described as well as the parameters and techniques for monitoring them. The impacts described in the literature are primarily shading, ions release, oxidative stress, adsorption, absorption and disruption of microalgae barriers. Several parameters are proposed to monitor effects such as growth, photosynthesis, membrane integrity, biochemical composition variations and gene expression changes. Finally, in the literature, while different impacts of nanoparticles on microalgae have been described, there is no consensus on evidence of nanomaterial toxicity with regard to microalgae. A parallel comparison of different nanoparticle types appears essential in order to prioritize which factors exert the most influence on toxicity in microalgae cultures: size, nature, surface chemistry, concentration or interaction time

Thermoresponsive block copolymers containing reactive azlactone groups and their bioconjugation with lysozyme

International audienceThermoresponsive block copolymers based on poly(ethylene oxide) (PEO) and poly(N-isopropyl acrylamide) (PNIPAM) containing azlactone groups along the backbone and at the chain-end of the macromolecular chain were synthesized by statistically reversible addition–fragmentation chain transfer (RAFT) copolymerization and by using a combination of RAFT polymerization and thiol–ene Michael addition. Well-defined poly(ethylene oxide)-b-poly(2-vinyl-4,4-dimethylazlactone-co-N-isopropyl acrylamide) (PEO-b-P(VDM-co-NIPAM)) block copolymers and azlactone-terminated poly(ethylene oxide)-b-poly(N-isopropyl acrylamide) (PEO-b-PNIPAM-VDM) diblock copolymers with low polydispersity indices (PDIs ≤ 1.10) were prepared and fully characterized by 1H NMR spectroscopy, FT-IR spectroscopy, and SEC. Such PEO-b-P(VDM-co-NIPAM) block copolymers and azlactone-terminated PEO-b-PNIPAM block copolymers present tunable lower critical solution temperature (LCST) depending on PEO, PNIPAM, and PVDM molar ratios. The reactivity of the PEO44-b-P(VDM20-co-NIPAM80) copolymer (Mn,NMR = 14 200 g mol−1, PDI = 1.08) and of the PEO44-b-PNIPAM101-VDM copolymer (Mn,NMR = 13 700 g mol−1, PDI = 1.08) was studied with lysozyme as a model protein. A bioconjugate with a higher apparent molecular weight was obtained with the PEO44-b-P(VDM20-co-NIPAM80) copolymer in comparison with the one obtained using the PEO44-b-PNIPAM101-VDM copolymer as shown by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The results suggest promising applications of azlactone-functionalized polymers within the field of bioconjugation

Miniature Inverted-Repeat Transposable Elements (MITEs) in the Two Lepidopteran Genomes of Helicoverpa armigera and Helicoverpa zea

Miniature inverted-repeat transposable elements MITEs are ubiquitous, non-autonomous class II transposable elements. The moths, Helicoverpa armigera and Helicoverpa zea, are recognized as the two most serious pest species within the genus. Moreover, these pests have the ability to develop insecticide resistance. In the present study, we conducted a genome-wide analysis of MITEs present in H. armigera and H. zea genomes using the bioinformatics tool, MITE tracker. Overall, 3570 and 7405 MITE sequences were identified in H. armigera and H. zea genomes, respectively. Comparative analysis of identified MITE sequences in the two genomes led to the identification of 18 families, comprising 140 MITE members in H. armigera and 161 MITE members in H. zea. Based on target site duplication (TSD) sequences, the identified families were classified into three superfamilies (PIF/harbinger, Tc1/mariner and CACTA). Copy numbers varied from 6 to 469 for each MITE family. Finally, the analysis of MITE insertion sites in defensome genes showed intronic insertions of 11 MITEs in the cytochrome P450, ATP-binding cassette transporter (ABC) and esterase genes in H. armigera whereas for H. zea, only one MITE was retrieved in the ABC-C2 gene. These insertions could thus be involved in the insecticide resistance observed in these pests

Genome-wide characterization of Mariner Like transposons and their derived MITEs in the Whitefly Bemisia tabaci (Hemiptera: Aleyrodidae)

International audienceThe whitefly, Bemisia tabaci is a hemipteran pest of vegetable crops vectoring a broad category of viruses. Currently, this insect pest showed a high adaptability and resistance to almost all the chemical compounds commonly used for its control. In many cases, Transposable Elements (TEs) contributed to the evolution of host genomic plasticity. This study focuses on the annotation of Mariner Like Elements (MLEs) and their derived Miniature Inverted repeat Transposable Elements (MITEs) in the genome of B. tabaci. Two full-length MLEs belonging to mauritiana and irritans subfamilies were detected and named Btmar1.1 and Btmar2.1, respectively. Additionally, 548 defective MLE sequences clustering mainly into 19 different Mariner lineages of mauritiana and irritans subfamilies were identified. Each subfamily showed a significant variation in MLE copy number and size. Furthermore, 71 MITEs were identified as MLEs derivatives that could be mobilized via the potentially active transposases encoded by Btmar 1.1 and Btmar2.1. The vast majority of sequences detected in the whitefly genome present unusual Terminal Inverted Repeats (TIRs) of up to 400 bp in length. However, some exceptions are sequences without TIRs. This feature of the MLEs and their derived MITEs in B. tabaci genome that distinguishes them from all the other MLEs so far described in insects, which have TIRs size ranging from 20 to 40 bp. Overall, our study provides an overview of MLEs, especially those with large TIRs, and their related MITEs, as well as diversity of their families, which will provide a better understanding of the evolution and adaptation of the whitefly genome

Health and Environmental Risk Assessment at Gold Panning Sites in the Northern Region (Burkina Faso)

Gold panning has an important contribution in the economic development of Burkina Faso. However, the mining activities expose people and the environment to severe risks. The present study was initiated to estimate the impact of gold panning on health and environmental resources. Samples of sweet pepper, water and soils were taken for mercury and cyanide content analysis. Mercury was extracted from the matrices by aqua regia and analysed by atomic absorption spectrophotometry. The cyanides were extracted from the matrices by centrifugation and analysed by colorimetry. Analyses showed the presence of mercury in soil samples but with contents lower than the standard of culture setting soils (5 mg/kg) except one, which displayed a mercury content of 13.45 mg/kg. In the same way, sweet pepper sample contained 3.17 mg/kg of mercury. Soils samples taken in the agricultural field were strongly contaminated by mercury and presented a very high potential ecological risk. In surface water and groundwater, the results of mercury analysis were all lower than the detection limit of the method used (0.02 µg/L). With regard to cyanides, all the analysed fresh mud samples had contents higher than the standard of culture setting in force in Burkina Faso (0.5 mg/kg). Water taken from Sissamba school « A » water pump, contained 0.12 mg/L of cyanide. This study highlighted many health and environmental problems on the gold panning sites in Burkina Faso. Keywords : gold panning, risk, health, environmen