Cloning, characterisation and comparative analysis of a starch synthase IV gene in wheat: functional and evolutionary implications

<p>Abstract</p> <p>Background</p> <p>Starch is of great importance to humans as a food and biomaterial, and the amount and structure of starch made in plants is determined in part by starch synthase (SS) activity. Five SS isoforms, SSI, II, III, IV and Granule Bound SSI, have been identified, each with a unique catalytic role in starch synthesis. The basic mode of action of SSs is known; however our knowledge of several aspects of SS enzymology at the structural and mechanistic level is incomplete. To gain a better understanding of the differences in SS sequences that underscore their specificity, the previously uncharacterised <it>SSIVb </it>from wheat was cloned and extensive bioinformatics analyses of this and other SSs sequences were done.</p> <p>Results</p> <p>The wheat SSIV cDNA is most similar to rice <it>SSIVb </it>with which it shows synteny and shares a similar exon-intron arrangement. The wheat <it>SSIVb </it>gene was preferentially expressed in leaf and was not regulated by a circadian clock. Phylogenetic analysis showed that in plants, SSIV is closely related to SSIII, while SSI, SSII and Granule Bound SSI clustered together and distinctions between the two groups can be made at the genetic level and included chromosomal location and intron conservation. Further, identified differences at the amino acid level in their glycosyltransferase domains, predicted secondary structures, global conformations and conserved residues might be indicative of intragroup functional associations.</p> <p>Conclusion</p> <p>Based on bioinformatics analysis of the catalytic region of 36 SSs and 3 glycogen synthases (GSs), it is suggested that the valine residue in the highly conserved K-X-G-G-L motif in SSIII and SSIV may be a determining feature of primer specificity of these SSs as compared to GBSSI, SSI and SSII. In GBSSI, the Ile485 residue may partially explain that enzyme's unique catalytic features. The flexible 380s Loop in the starch catalytic domain may be important in defining the specificity of action for each different SS and the G-X-G in motif VI could define SSIV and SSIII action particularly.</p

NADP-Dependent Isocitrate Dehydrogenase from Arabidopsis Roots Contributes in the Mechanism of Defence against the Nitro-Oxidative Stress Induced by Salinity

NADPH regeneration appears to be essential in the mechanism of plant defence against oxidative stress. Plants contain several NADPH-generating dehydrogenases including isocitrate dehydrogenase (NADP-ICDH), glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), and malic enzyme (ME). In Arabidopsis seedlings grown under salinity conditions (100 mM NaCl) the analysis of physiological parameters, antioxidant enzymes (catalase and superoxide dismutase) and content of superoxide radical (O2  ∙−), nitric oxide (NO), and peroxynitrite (ONOO−) indicates a process of nitro-oxidative stress induced by NaCl. Among the analysed NADPH-generating dehydrogenases under salinity conditions, the NADP-ICDH showed the maximum activity mainly attributable to the root NADP-ICDH. Thus, these data provide new insights on the relevance of the NADP-ICDH which could be considered as a second barrier in the mechanism of response against the nitro-oxidative stress generated by salinity

Superhard transparent hybrid nanocomposites for high fidelity UV-nanoimprint lithography

Transparent hyperbranched acrylate nanocomposites were produced using different combinations of silica nanoparticles and silicon-based sol-gel precursors. The nanocomposites were processed using a dual-cure UV polymerization and condensation scheme. The viscosity of hybrid suspensions was found to be one to two orders of magnitude lower than that of particulate composites with the same equivalent silica fraction. The Vickers microhardness of the polymer was 112 MPa. It was equal to 190 MPa and 148 MPa for the hybrid composites and particulate composites with 20 vol% SiO2, respectively, and it was equal to 287 MPa for the hybrid material with 30 vol% SiO2. Light-trapping textures in the form of random sub-micron pyramidal features were replicated in the hybrid composites from a nickel template using UV-nanoimprint lithography. After optimization of the dual-cure process sequence, a very high replication fidelity was obtained for all investigated compositions, leading to a haze above 99% over the visible light spectrum and a very effective light scattering performance in a broad angular exposure. (C) 2013 Elsevier Ltd. All rights reserved

Análisis de la nitración fisiológica de proteínas en órganos de plantas de guisante (Pisum sativum L) durante su desarrollo y senescencia

Comunicaciones a congreso

A Facile in Situ and UV Printing Process for Bioinspired Self-Cleaning Surfaces

A facile in situ and UV printing process was demonstrated to create self-cleaning synthetic replica of natural petals and leaves. The process relied on the spontaneous migration of a fluorinated acrylate surfactant (PFUA) within a low-shrinkage acrylated hyperbranched polymer (HBP) and its chemical immobilization at the polymer-air interface. Dilute concentrations of 1 wt. % PFUA saturated the polymer-air interface within 30 min, leading to a ten-fold increase of fluorine concentration at the surface compared with the initial bulk concentration and a water contact angle (WCA) of 108◦. A 200 ms flash of UV light was used to chemically crosslink the PFUA at the HBP surface prior to UV printing with a polydimethylsiloxane (PDMS) negative template of red and yellow rose petals and lotus leaves. This flash immobilization hindered the reverse migration of PFUA within the bulk HBP upon contacting the PDMS template, and enabled to produce texturized surfaces with WCA well above 108◦. The synthetic red rose petal was hydrophobic (WCA of 125◦) and exhibited the adhesive petal effect. It was not superhydrophobic due to insufficient concentration of fluorine at its surface, a result of the very large increase of the surface of the printed texture. The synthetic yellow rose petal was quasi-superhydrophobic (WCA of 143◦, roll-off angle of 10◦) and its self-cleaning ability was not good also due to lack of fluorine. The synthetic lotus leaf did not accurately replicate the intricate nanotubular crystal structures of the plant. In spite of this, the fluorine concentration at the surface was high enough and the leaf was superhydrophobic (WCA of 151◦, roll-off angle below 5◦) and also featured self-cleaning properties

UV-nanoimprint lithography and large area roll-to-roll texturization with hyperbranched polymer nanocomposites for light-trapping applications

Light-trapping textures were produced in hyperbranched polymer (HBP) silica nanocomposites using a UV-nanoimprint lithography (UVNIL) replication method, either in batch or roll-to-roll processes. The hardness of the HBP was found to increase by a factor of 2.5 with the addition of 50 vol% of nanoparticles. A nickel master with random sub-micron pyramidal structures was used to imprint nanocomposites containing up to 20 vol% of silica on a polyethylene naphthalate (PEN) substrate. The influence of nanoparticle fraction and pressure on the texture morphology and light scattering properties of the replicas was studied using scanning electron microscopy and optical analysis. The roughness and coherence length of the textures were similar to those of the master for all investigated compositions and process pressures. Likewise, the light scattering performance of aluminum-coated texturized nanocomposites was identical to that of the metal template, with a haze of 90% over the 400–800 nm spectral range. Thin film amorphous silicon solar cells were deposited on the texturized substrates using a large-area roll-to-roll process. The photocurrent of these devices was found to be 23% higher than the reference value of a flat cell

Identification and Characterization of Vnx1p, a Novel Type of Vacuolar Monovalent Cation/H+ Antiporter of Saccharomyces cerevisiae

We identified and characterized Vnx1p, a novel vacuolar monovalent cation/H+ antiporter encoded by the open reading frame YNL321w from Saccharomyces cerevisiae. Despite the homology of Vnx1p with other members of the CAX (calcium exchanger) family of transporters, Vnx1p is unable to mediate Ca2+ transport but is a low affinity Na+/H+ and K+/H+ anti-porter with a Km of 22.4 and 82.2 mm for Na+ and K+, respectively. Sequence analyses of Vnx1p revealed the absence of key amino acids shown to be essential for Ca2+/H+ exchange. vnx1Δ cells displayed growth inhibition when grown in the presence of hygromycin B or NaCl. Vnx1p activity was found in the vacuoles and shown to be dependent on the electrochemical potential gradient of H+ generated by the action of the V-type H+-ATPase. The presence of Vnx1p at the vacuolar membrane was further confirmed with cells expressing a VNX1::GFP chimeric gene. Similar to Nhx1p, the prevacuolar compartment-bound Na+/H+ antiporter, the vacuole-bound Vnx1p appears to play roles in the regulation of ion homeostasis and cellular pH

Régulation et rôle physiologique du gène VvHT1 (Vitis vinifera hexose transporter 1) exprimé durant la maturation de la baie de raisin

La qualité des vins dépend du rapport acides/glucides des baies de raisin à la vendange. Les glucides s'accumulent fortement dans la baie sous forme d'hexoses à partir du stade de la maturation appelé véraison. Un clone codant un transporteur potentiel d'hexoses (VvHT1: Vitis vinifera Hexose Transporter 1) a été obtenu au laboratoire. Son expression augmente à la véraison. Le travail présent concerne la régulation de l'expression de VvHT1, (en utilisant le géne rapporteur GUS) et son rôle physiologique dans la plante. Ces résultats donnent le premier exemple d'un transporteur d'hexose induit par des glucides non transports, ce qui implique une signalisation glucidique extracellulaire. Le rôle physiologique de VvHT1 a été étudié par la stratégie "sens/anti-sens" grâce à des plants de Tabac transformés. Certaines des plantes transformées présentent un phénotype particulier et sont affectées au niveau du rapport source/puits, de l'absorption des glucides et du métabolisme glucidique.Wine quality strongly depends on the ratio acid/sugar of the grape berries at harvest. Grapevine berries (Vitis vinifera) mainly store hexoses. This accumulation which starts suddenly at the ripening stage named vraison, involves hexoses transporters. A complete clone (VvHT1: Vitis vinifera hexose transporter 1) was previously isolated in the laboratory. Its expression increases around vraison, suggesting that VvHT1 could be involved in hexose accumulation during berry ripening. The work presented here deals with the regulation of VvHT1promoter, using the GUS reporter gene, and with its physiological role, using a sense/antisense strategy in tobacco plants. The data provide the first example of a putative hexose transporter induced by sugars in higher plants and demonstrate an original sugar sensing phenomenon. Some of the plants transformed with VvHT1 cDNA show a marked phenotype and are clearly affected in source/sink partitioning, glucose uptake and sugar metabolism in leaves.POITIERS-BU Sciences (861942102) / SudocSudocFranceF