RNA-seq analysis of the Rhizobium tropici CIAT 899 transcriptome shows similarities in the activation patterns of symbiotic genes in the presence of apigenin and salt

Background Rhizobium tropici strain CIAT 899 establishes effective symbioses with several legume species, including Phaseolus vulgaris and Leucaena leucocephala. This bacterium synthesizes a large variety of nodulation factors in response to nod-gene inducing flavonoids and, surprisingly, also under salt stress conditions. The aim of this study was to identify differentially expressed genes in the presence of both inducer molecules, and analyze the promoter regions located upstream of these genes. Results Results obtained by RNA-seq analyses of CIAT 899 induced with apigenin, a nod gene-inducing flavonoid for this strain, or salt allowed the identification of 19 and 790 differentially expressed genes, respectively. Fifteen of these genes were up-regulated in both conditions and were involved in the synthesis of both Nod factors and indole-3-acetic acid. Transcription of these genes was presumably activated through binding of at least one of the five NodD proteins present in this strain to specific nod box promoter sequences when the bacterium was induced by both apigenin and salt. Finally, under saline conditions, many other transcriptional responses were detected, including an increase in the transcription of genes involved in trehalose catabolism, chemotaxis and protein secretion, as well as ribosomal genes, and a decrease in the transcription of genes involved in transmembrane transport. Conclusions To our knowledge this is the first time that a transcriptomic study shows that salt stress induces the expression of nodulation genes in the absence of flavonoids. Thus, in the presence of both nodulation inducer molecules, apigenin and salt, R. tropici CIAT 899 up-regulated the same set of symbiotic genes. It could be possible that the increases in the transcription levels of several genes related to nodulation under saline conditions could represent a strategy to establish symbiosis under abiotic stressing conditions.España, Ministerio de Economía y Competitividad AGL2012-1España, Junta de Andalucía P11-CVI-705

FIB plan view lift-out sample preparation for TEM characterization of periodic nanostructures obtained by spinodal decomposition in Co1.7Fe1.3O4 thin films

There is a miscibility gap in the CoFe2O4–Co3O4 phase diagram. In this miscibility gap, the oxides can be subjected to a spinodal transformation. It has already been observed in oxides consisting of crystals greater than or equal to 100 nm that spinodal decomposition leads to the formation of two alternating iron-rich and cobalt-rich spinel phases. The pseudo-periodic alternation occurs approximately every 5 nm. In the miscibility gap, thin films of pure iron cobaltites, consisting of crystallites of the order of 10 nm in diameter and around 300 nm in thickness, undergo transformation when they are treated at 600 °C for several hours. X-ray diffraction and Raman spectroscopy clearly reveal this transformation, which is accentuated as a function of the treatment time. An electron microscopy study of the cross-sections (view of the films along their thickness), confirms the progressive separation of the former spinel oxide in iron-rich and cobalt-rich spinel phases, without however revealing a pseudo-periodic organization of these phases, whatever the time of treatment. In an attempt to reveal this organization, a specific method of preparation has been implemented to extract the upper part of the films parallel to their basic plane and to observe the crystallites in plan view. The alternation of the iron- and cobalt-rich phases could, however, only be found in the largest crystallites. It seems that the nanometric size of the crystallites prevents the establishment of a pseudo-periodic organization of the phases during the periodic transformation. The observation of compositional anomalies in the grain boundaries seems to support the hypothesis related to a nanometric effect of the crystallization

Managing Phenol Contents in Crop Plants by Phytochemical Farming and Breeding—Visions and Constraints

Two main fields of interest form the background of actual demand for optimized levels of phenolic compounds in crop plants. These are human health and plant resistance to pathogens and to biotic and abiotic stress factors. A survey of agricultural technologies influencing the biosynthesis and accumulation of phenolic compounds in crop plants is presented, including observations on the effects of light, temperature, mineral nutrition, water management, grafting, elevated atmospheric CO2, growth and differentiation of the plant and application of elicitors, stimulating agents and plant activators. The underlying mechanisms are discussed with respect to carbohydrate availability, trade-offs to competing demands as well as to regulatory elements. Outlines are given for genetic engineering and plant breeding. Constraints and possible physiological feedbacks are considered for successful and sustainable application of agricultural techniques with respect to management of plant phenol profiles and concentrations

Multi-scale investigation of an ancient Al-Cu-Mg-Si alloy collected on a German WWII aircraft

International audienceCrashed aircraft from World War II provide large amount of ancient materials, in particular Duralumin, which has been, for more than a century the principal metallic (aluminium) constituting the frame and fuselage of aircraft. Valuable information can be retrieved by investigating these materials

Morphology and symmetry driven by lattice accommodation in polycrystalline bcc-fcc core-shell metallic nanoparticles

Bcc-fcc multi-metallic nanoparticles associating a single-crystal core (Fe, FeCo alloys…) with a polycrystalline noble metal shell (Au, AuAg alloys …) are perfectly symmetrical or more irregular, even dramatically dissymmetrical, yet presenting a good crystalline organization. Here a combination of experimental analysis and theoretical symmetry analysis is proposed, in order to provide a unified description of the observed morphologies (Fe-Au and Fe-AuAg systems), whatever their symmetry, and predict some morphology variability in a population of nanoparticles. First the central role of the crystal lattice accommodation is comprehensively analyzed from the experimental Fe-AuAg system. The two possible bcc-fcc epitaxial relationships generate a core-shell interface in the shape of a truncated rhombic dodecahedron. This results in two different types of grains in the shell which are elastically accommodated between them by an equal distribution of twins and low angle grain boundaries, however at the cost of internal stresses. At the same time, a symmetry breaking results from two possible growth variants originating from the Nishiyama-Wasserman epitaxial relationships. The shell grains fit together in a nano-puzzle-like organization, resulting in a large number of possible arrangements distributed in 13 different point groups of symmetry, all of lower order than the core symmetry (highest order of cubic symmetry). If the variants are randomly distributed, the probability for the nanoparticle to be asymmetric (group 1) is 80%. The dissymmetrical development of the nanoparticles is then discussed. Extending this approach to other core shapes succeeds in predicting dissymmetrical or dramatically off-centered morphologies experimentally observed in Fe-Au nanoparticles

Morphology and symmetry driven by lattice accommodation in polycrystalline bcc-fcc core-shell metallic nanoparticles

Bcc-fcc multi-metallic nanoparticles associating a single-crystal core (Fe, FeCo alloys…) with a polycrystalline noble metal shell (Au, AuAg alloys …) are perfectly symmetrical or more irregular, even dramatically dissymmetrical, yet presenting a good crystalline organization. Here a combination of experimental analysis and theoretical symmetry analysis is proposed, in order to provide a unified description of the observed morphologies (Fe-Au and Fe-AuAg systems), whatever their symmetry, and predict some morphology variability in a population of nanoparticles. First the central role of the crystal lattice accommodation is comprehensively analyzed from the experimental Fe-AuAg system. The two possible bcc-fcc epitaxial relationships generate a core-shell interface in the shape of a truncated rhombic dodecahedron. This results in two different types of grains in the shell which are elastically accommodated between them by an equal distribution of twins and low angle grain boundaries, however at the cost of internal stresses. At the same time, a symmetry breaking results from two possible growth variants originating from the Nishiyama-Wasserman epitaxial relationships. The shell grains fit together in a nano-puzzle-like organization, resulting in a large number of possible arrangements distributed in 13 different point groups of symmetry, all of lower order than the core symmetry (highest order of cubic symmetry). If the variants are randomly distributed, the probability for the nanoparticle to be asymmetric (group 1) is 80%. The dissymmetrical development of the nanoparticles is then discussed. Extending this approach to other core shapes succeeds in predicting dissymmetrical or dramatically off-centered morphologies experimentally observed in Fe-Au nanoparticles

Influence of process parameters on energetic properties of sputter-deposited Al/CuO reactive multilayers

International audienceIn this study we demonstrate the effect of change of the sputtering power and the deposition pressure on the ignition and the combustion properties of Al/CuO reactive thin films. A reduced sputtering power of Al along with the deposition carried out at a higher-pressure result in a high-quality thin film showing a 200% improvement in the burn rate and a 50% drop in the ignition energy. This highlights the direct implication of the change of the process parameters on the responsivity and the reactivity of the reactive film while maintaining the Al and CuO thin-film integrity both crystallographically and chemically. Atomically resolved structural and chemical analyzes enabled us to qualitatively determine how the microstructural differences at the interface (thickness, stress level, delamination at high temperatures and intermixing) facilitate the Al and O migrations and impact the overall nano-thermite reactivity. We found that the deposition of CuO under low pressure produces well-defined and similar Al-CuO and CuO-Al interfaces with the least expected intermixing. Our investigations also showed that the magnitude of residual stress induced during the deposition plays a decisive role in influencing the overall nano-thermite reactivity. Higher is the magnitude of the tensile residual stress induced, stronger is the presence of gaseous oxygen at the interface. By contrast, high compressive interfacial stress aids in preserving the Al atoms for the main reaction while not getting expended in the interface thickening. Overall, this analysis helped in understanding the effect of change of deposition conditions on the reactivity of Al/CuO nanolaminates and several handles that may be pulled to optimize the process better by means of physical engineering of the interfaces

Band structure tuning at (La,Sr)MnO3 / (Ba,Sr)TiO3 interface

International audienceBand structure engineering in silicon-based heterostructures dedicated to microelectronic and energy harvesting applications has been common material scientist playground for decades. Careful design of the energy level variation at hetero-interfaces is used e.g. to collect electron while preventing electron-hole recombination in PV heterostructures, control electron injection with Schottky barriers (SB), promote quantum well... Although band structure engineering in Si or GaAs based heterostructures is a very mature field, it is a relatively new territory for oxide electronic where emerging new device concepts based on perovskite-derived heterostructures makes it very desirable. In all perovskite-based heterostructures, the structural continuity at ABO3 hetero-interfaces gives extra degrees of freedom to tune electronic and structural properties. Rumpling, polar discontinuity, interfacial B-site cation environment asymmetry, BO6 octahedral rotations are all potential levers to alter the band structure and promote electronic properties like e.g. interface polarization [1] or enhanced SB height [2,3].One way to play with these degrees of freedom is to modulate the interface chemical composition by introducing an Interface Control Layer (ICL), as it has been proposed decades ago for Si and GaAs based heterostructures. [3] To accelerate the exploration of ICL perovskite materials, we implemented an interface combinatorial pulsed laser deposition (ICPLD) set-up. [4] We report here on epitaxial La0.7Sr0.3MnO3/ ICL (3uc) /SrTiO3 (0-9uc) junctions with ICL = La1-xSrxMnO3 and Ba1-ySryTiO3. XPS/UPS spectroscopies were used to probe core levels, work function (WF) and band bending versus ICL composition and STO thickness. Modulation of WF leading to a transition from Schottky to ohmic contact with the polar discontinuity will be discussed together with interface atomic structure characterized by HR-STEM

Band structure tuning at (La,Sr)MnO3 / (Ba,Sr)TiO3 interface

International audienceBand structure engineering in silicon-based heterostructures dedicated to microelectronic and energy harvesting applications has been common material scientist playground for decades. Careful design of the energy level variation at hetero-interfaces is used e.g. to collect electron while preventing electron-hole recombination in PV heterostructures, control electron injection with Schottky barriers (SB), promote quantum well... Although band structure engineering in Si or GaAs based heterostructures is a very mature field, it is a relatively new territory for oxide electronic where emerging new device concepts based on perovskite-derived heterostructures makes it very desirable. In all perovskite-based heterostructures, the structural continuity at ABO3 hetero-interfaces gives extra degrees of freedom to tune electronic and structural properties. Rumpling, polar discontinuity, interfacial B-site cation environment asymmetry, BO6 octahedral rotations are all potential levers to alter the band structure and promote electronic properties like e.g. interface polarization [1] or enhanced SB height [2,3].One way to play with these degrees of freedom is to modulate the interface chemical composition by introducing an Interface Control Layer (ICL), as it has been proposed decades ago for Si and GaAs based heterostructures. [3] To accelerate the exploration of ICL perovskite materials, we implemented an interface combinatorial pulsed laser deposition (ICPLD) set-up. [4] We report here on epitaxial La0.7Sr0.3MnO3/ ICL (3uc) /SrTiO3 (0-9uc) junctions with ICL = La1-xSrxMnO3 and Ba1-ySryTiO3. XPS/UPS spectroscopies were used to probe core levels, work function (WF) and band bending versus ICL composition and STO thickness. Modulation of WF leading to a transition from Schottky to ohmic contact with the polar discontinuity will be discussed together with interface atomic structure characterized by HR-STEM

Band structure tuning at (La,Sr)MnO3 / (Ba,Sr)TiO3 interface

International audienceBand structure engineering in silicon-based heterostructures dedicated to microelectronic and energy harvesting applications has been common material scientist playground for decades. Careful design of the energy level variation at hetero-interfaces is used e.g. to collect electron while preventing electron-hole recombination in PV heterostructures, control electron injection with Schottky barriers (SB), promote quantum well... Although band structure engineering in Si or GaAs based heterostructures is a very mature field, it is a relatively new territory for oxide electronic where emerging new device concepts based on perovskite-derived heterostructures makes it very desirable. In all perovskite-based heterostructures, the structural continuity at ABO3 hetero-interfaces gives extra degrees of freedom to tune electronic and structural properties. Rumpling, polar discontinuity, interfacial B-site cation environment asymmetry, BO6 octahedral rotations are all potential levers to alter the band structure and promote electronic properties like e.g. interface polarization [1] or enhanced SB height [2,3].One way to play with these degrees of freedom is to modulate the interface chemical composition by introducing an Interface Control Layer (ICL), as it has been proposed decades ago for Si and GaAs based heterostructures. [3] To accelerate the exploration of ICL perovskite materials, we implemented an interface combinatorial pulsed laser deposition (ICPLD) set-up. [4] We report here on epitaxial La0.7Sr0.3MnO3/ ICL (3uc) /SrTiO3 (0-9uc) junctions with ICL = La1-xSrxMnO3 and Ba1-ySryTiO3. XPS/UPS spectroscopies were used to probe core levels, work function (WF) and band bending versus ICL composition and STO thickness. Modulation of WF leading to a transition from Schottky to ohmic contact with the polar discontinuity will be discussed together with interface atomic structure characterized by HR-STEM