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Phosphogypsum (PG) is an acidic industrial by-product, resulting from the production of phosphoric acid. In Tunisia, 10 million tons of PG are discarded yearly without any treatment. The Tunisian PG is characterized by its cadmium content of about 3.1–22.9 mg/kg. It is mainly stocked without any treatment near the production sites. Therefore, minimizing the negative impact of this waste has increasingly aroused the interest of many researchers. The use of PG as alternative phosphorous and sulfate fertilizer was envisaged. In this context, we have investigated the possibility of cultivating transgenic potato plants overexpressing the dehydration responsive element binding (StDREB1) protein on PG-supplemented substrates. Prewashed PG (WPG) was used to reduce the acidity of PG. Two WPG concentrations were used (15 and 30%) for potato culture during 60 days. The data show that WPG altered the survival rate of wild-type potato plants. Indeed, increasing the amount and treatment period of WPG led to a decrease in plant survival to 10% (after 60 days), while the survival rate of transgenic lines was about 50% with normal growth characteristics. Furthermore, an increase in proline and soluble sugar and reduced levels of H2O2 and malondialdehyde were measured in transgenic plants. An increase in antioxidant enzyme activities was observed in these transgenic lines revealing that they can cope with oxidative stress generated by phosphogypsum addition in the medium. A very low accumulation of Cd was detected in leaves of both transgenic lines. All these data suggest that overexpression of the StDREB1 transcription factor in transgenic potato plants improved their tolerance to WPG.

We report on the design of a simple yet sensitive and selective electrode for amperometric determination of dopamine at a cathodic potential as low as −0.30 V vs. Ag/AgCl. The electrode was obtained by self-assembly of ω-mercaptopropyl naphthoquinone (NQ-SAM) on the surface of a polycrystalline gold electrode. The presence of dopamine induces an increase of the reduction current peak at −0.30 V corresponding to the reduction of naphthoquinone to hydronaphthoquinone. Dopamine and dopamine-quinone accumulate on the surface to form a 3D network linked by hydrogen bonds. Raman and infrared spectroscopy as well as atomic force microscopy confirmed the multilayer formation. The method allows dopamine to be indirectly detected at a working potential that is lower by 0.50 V than the standard oxidation potential at a bare gold electrode. The sensor shows distinct oxidation potentials for dopamine (120 mV), ascorbic acid (280 mV) and uric acid (520 mV) which makes the method fairly selective. The analytical range extends from 1 to 100 μM concentrations of dopamine, and the limits of detection and quantification are 0.040 and 0.134 μM, respectively.

Electrically addressed covalent immobilization of biomolecules to the defined electrodes of an electrode array is described. It is based on Michael addition of the thiol group of biomolecules to α,β-unsaturated carbonyl groups of benzoquinone. This "click" reaction was tested by immobilization of a number of thiolated compounds on the simplest array consisting of two gold electrodes coated by a self-assembled monolayer of benzoquinone-terminated hexanethiol. Electrically controlled binding of hexanethiol, ferrocenylhexanethiol, human serum albumin and thiol-terminated single-stranded DNA (ssDNA) was investigated. The binding was studied using cyclic voltammetry, X-ray photoelectron spectroscopy and surface plasmon resonance. The reaction requires the oxidized state of the benzoquinone moiety; this can be reached by applying of a moderate anodic potential to the electrode. Surface plasmon resonance measurements demonstrated that the thiol-modified ssDNA immobilized by this technique binds complementary synthetic oligonucleotides or PCR-amplified DNA fragments. The developed technology of electrical addressing of covalent immobilization can be applied for fabrication of sensor arrays.

International audience; Metabolisms represent highly organized systems characterized by strong regulations satisfying the mass conservation principle. This makes a whole chemical resource to be competitively shared between several ways at both intra-and inter-molecular scales. Whole resource sharing can be statistically associated with a constant sum-unit constraint which represents the basis of simplex mixture rule. In this work, a new simplex-based simulation approach was developed to learn scaffold information on metabolic processes controlling molecular diversity from a wide set of observed chemical structures. Starting from a dataset of chemical structures classified into p clusters, a machine learning process was applied by linearly combining the p clusters j and randomly sampling a constant number (n) of molecules according to different clusters' weights (wj/w) given by Scheffé's mixture matrix. At the output of mixture design, molecular linear combinations lead to calculate barycentric molecules integrating the characteristics of the different weighted clusters. The N mixtures-design was iterated by bootstrap technique leading to extensive exploration of chemical variability between and within clusters. Finally, the K response matrices issued from K iterated mixture designs were averaged to calculate a smoothed matrix containing scaffold information on regulation processes responsible for molecular diversification at inter- and intra-molecular (atomic) scales. This matrix was used as a backbone for graphical analysis of positive and negative trends between atomic characteristics (chemical substitutions) at both mentioned scales. This new simplex approach was illustrated by cycloartane-based saponins of Astragalus genus by combining three desmosylation clusters characterized by relative glycosylation levels of different aglycones' carbons.

International audience; Background. Olive oils (OOs) show high chemical variability due to several factors of genetic, environmental and anthropic types. Genetic and environmental factors are responsible for natural compositions and polymorphic diversification resulting in different varietal patterns and phenotypes. Anthropic factors, however, are at the origin of different blends' preparation leading to normative, labelled or adulterated commercial products. Control of complex OO samples requires their (i) characterization by specific markers; (ii) authentication by fingerprint patterns; and (iii) monitoring by traceability analysis.Methods. These quality control and management aims require the use of several multivariate statistical tools: specificity highlighting requires ordination methods; authentication checking calls for classification and pattern recognition methods; traceability analysis implies the use of network-based approaches able to separate or extract mixed information and memorized signals from complex matrices. Results. This chapter presents a review of different chemometrics methods applied for the control of OO variability from metabolic and physical-chemical measured characteristics. The different chemometrics methods are illustrated by different study cases on monovarietal and blended OO originated from different countries.Conclusion. Chemometrics tools offer multiple ways for quantitative evaluations and qualitative control of complex chemical variability of OO in relation to several intrinsic and extrinsic factors.

We report on the design of an amperometric tyrosinase-based biosensor using a self-assembled monolayer of ω-mercaptopropyl naphthoquinone on gold electrode as an electron mediator. Under optimal conditions (i.e. pH=7.4 and E=-0.35V vs. KCl), the chronoamperometric response of the naphthoquinone-modified bioelectrode to successive additions of phenol was evaluated. The biosensor exhibits sensitive bioelectrocatalytic response at a working potential of -0.35V vs. Ag/AgCl (sat.KCl), reaching the steady-state current within 40s after each addition of phenol solution with a range of 0-135μM and a limit of detection and quantification which are 0.019μM and 0.0633μM, respectively. The bioelectrode was used to determine the content in polyphenol in a local virgin olive oil.

It has been established that drought-responsive element binding (DREB) proteins correspond to transcription factors which play important regulatory roles in plant response to abiotic and biotic stresses. In this study, a novel cDNA encoding DREB transcription factor, designated StDREB1, was isolated from potato (Solanum tuberosum L.). This protein was classified in the A-4 group of DREB subfamily based on multiple sequence alignments and phylogenetic characterization. Semi-quantitative RT-PCR showed that StDREB1 is expressed in leaves, stems, and roots under stress conditions and it is greatly induced by NaCl, drought, low temperature, and abscisic acid (ABA) treatments. Overexpression of StDREB1 cDNA in transgenic potato plants exhibited an improved salt and drought stress tolerance in comparison to the non-transformed controls. The enhanced stress tolerance may be associated with the increase in P5CS-RNA expression (δ 1-pyrroline-5-carboxylate synthetase) and the subsequent accumulation of proline osmoprotectant in addition to a better control of water loss. Overexpression of StDREB1 also activated stress-responsive genes, such as those encoding calcium-dependent protein kinases (CDPKs), in transgenic potatoes under standard and high salt conditions. These data suggest that the StDREB1 transcription factor is involved in the regulation of salt stress tolerance in potato by the activation of different downstream gene expression.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; Dehydration responsive element binding proteins (DREB) are members of a larger family of transcription factors, many of which have been reported to contribute to plant responses to abiotic stresses in several species. While, little is known about their role in potato (Solanum tuberosum). This report describes the cloning and characterization of a DREB transcription factor cDNA, StDREB2, isolated from potato(cv Nicola) plants submitted to salt treatment. Based on a multiple sequence alignment, this protein was classified into the A-5 group of DREB subfamily. Expression studies revealed that StDREB2 was induced in leaves, roots and stems upon various abiotic stresses and in response to exogenous treatment with abscisic acid (ABA). In agreement with this expression pattern, over-expression of StDREB2 in transgenic potato plants resulted in enhanced tolerance to salt stress. These data suggest that the isolated StDREB2 encodes a functional protein involved in plant response to different abiotic stresses. An electrophoretic mobility shift assay (EMSA) indicated that the StDREB2 protein bound specifically to the DRE core element (ACCGAGA) in vitro. Moreover, Semi quantitative RT-PCR analysis revealed that the transcript level of a putative target gene i.e. d1-pyrroline-5-carboxylate synthase (P5CS) was upregulated in transgenic plants submitted to salt stress conditions. A concomitant increase in proline accumulation was also observed under these conditions. Taking together, all these data suggest that StDREB2 takes part in the processes underlying plant responses to abiotic stresses probably via the regulation of ABA hormone signaling and through a mechanism allowing proline synthesis.