Pourquoi inciter les agriculteurs à innover dans les techniques de désherbage ? Etat de la pratique et propositions de la recherche

International audienceL'abondance et la diversité des adventices constituent des contraintes majeures de la production des systèmes de culture des savanes d'Afrique Centrale. Dans les systèmes traditionnels, le sarclage manuel sélectif, apparaît comme une technique à fonctions multiples. Dans les systèmes plus "modernes", les techniques de désherbage chimique et mécanique sont de plus en plus souvent associées. On constate des décalages importants entre les prescriptions techniques et les pratiques. Des sarclages tardifs combinés à une maîtrise approximative des herbicides contraignent souvent l'agriculteur à l'abandon d'une partie des parcelles et engendrent des pertes de production significatives (20% pour le cotonnier). Depuis une dizaine d'années, on constate une poussée de l'innovation dans la lutte contre les adventices. Au Nord-Cameroun, le désherbage chimique réalise une percée vigoureuse sur coton et maïs avec des herbicides totaux et de pré-levée, et plus récemment sur le muskuwaari. Aussi depuis 4 ans, les ventes de sarcleurs et de butteurs prennent le pas sur les ventes de charrues témoignant de l'intérêt croissant des agriculteurs pour les techniques de désherbage. Ces constats ont conduit diverses équipes de recherche à analyser les changements et à proposer des nouveaux concepts de désherbage. Pour la mécanisation, la recherche propose des attelages plus maniables (monobovin), des bâtis monovalents économiques et préconise une intervention précoce. Concernant le désherbage chimique plusieurs pistes sont explorées soit en complément de la mécanisation dans un esprit de lutte intégrée, soit en substitution tout en évitant la sélection d'espèces envahissantes. (Résumé d'auteur

Solving Crew Scheduling Problems with Metaheuristics : A Comparative Study

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N-glycosidase treatment with 18O labeling and de novo sequencing argues for flagellin FliC glycopolymorphism in Pseudomonas aeruginosa.

International audienceIn prokaryote organisms, N-glycosylation of proteins is often correlated to cell-cell recognition and extracellular events. Those glycoproteins are potential targets for infection control. To date, many surface-glycosylated proteins from bacterial pathogens have been described. However, N-linked Pseudomonas surface-associated glycoproteins remain underexplored. We report a combined enrichment and labeling strategy to identify major glycoproteins on the outside of microorganisms. More precisely, bacteria were exposed to a mix of biotinylated lectins able to bind with glycoproteins. The latter were then recovered by avidin beads, digested with trypsin, and submitted to mass spectrometry. The targeted mixture of glycoproteins was additionally deglycosylated in the presence of H2(18)O to incorporate (18)O during PNGase F treatment and were also analyzed using mass spectrometry. This approach allowed us to identify a few tens of potential N-glycoproteins, among which flagellin FliC was the most abundant. To detect the possible sites of FliC modifications, a de novo sequencing step was also performed to discriminate between spontaneous deamidation and N-glycan loss. This approach led to the proposal of three potential N-glycosylated sites on the primary sequence of FliC: N26, N69, and N439, with two of these three asparagines belonging to an N-X-(S/T) consensus sequence. These observations suggest that flagellin FliC is a heterogeneous protein mixture containing both O- and N-glycoforms

Étude différentielle des protéomes de branchies de dreissènes (moules d’eau douce) récoltées sur des sites pollués ou non

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Design and Synthesis of Epicocconone Analogues with Improved Fluorescence Properties

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Behavioral effects of urotensin-II centrally administered in mice

International audienceUrotensin-II (U-II) receptors are widely distributed in the central nervous system. Intracerebroventricular (i.c.v.) injection of U-II causes hypertension and bradycardia and stimulates prolactin and thyrotropin secretion. However, the behavioral effects of centrally administered U-II have received little attention. In the present study, we tested the effects of i.c.v. injections of U-II on behavioral, metabolic, and endocrine responses in mice. Administration of graded doses of U-II (1-10,000 ng/mouse) provoked: (1) a dose-dependent reduction in the number of head dips in the hole-board test; (2) a dose-dependent reduction in the number of entries in the white chamber in the black-and-white compartment test, and in the number of entries in the central platform and open arms in the plus-maze test; and (3) a dose-dependent increase in the duration of immobility in the forced-swimming test and tail suspension test. Intracerebroventricular injection of U-II also caused an increase in: food intake at doses of 100 and 1,000 ng/mouse, water intake at doses of 100-10,000 ng/mouse, and horizontal locomotion activity at a dose of 10,000 ng/mouse. Whatever was the dose, the central administration of U-II had no effect on body temperature, nociception, apomorphine-induced penile erection and climbing behavior, and stress-induced plasma corticosterone level. Taken together, the present study demonstrates that the central injection of U-II at doses of 1-10,000 ng/mouse induces anxiogenic- and depressant-like effects in mouse. These data suggest that U-II may be involved in some aspects of psychiatric disorders

Design and Synthesis of Epicocconone Analogues with Improved Fluorescence Properties

Epicocconone is a natural latent fluorophore that is widely used in biotechnology because of its large Stokes shift and lack of fluorescence in its unconjugated state. However, the low photostability and quantum yields of epicocconone have limited its wider use, and in the absence of a total synthesis, this limitation has been a long-standing problem. Here we report a general strategy for the synthesis of epicocconone analogues that relies on a 2-iodoxybenzoic acid-mediated dearomatization and on the replacement of the triene tail of the natural product by an aromatic ring. This design element is general and the synthesis is straightforward, providing ready access to libraries of polyfunctional fluorophores with long Stokes shifts based on the epicocconone core. Our structural modifications resulted in analogues with increased photostability and quantum yields compared with the natural product. Staining proteomic gels with these new analogues showed significant lowering of the detection limit and a 30% increase in the number of low-abundance proteins detected. These epiccoconone analogues will substantially improve the discovery rate of biomarker needles in the proteomic haystack