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The Arabidopsis gibberellin methyl transferase 1 suppresses gibberellin activity, reduces whole-plant transpiration and promotes drought tolerance in transgenic tomato.

Previous studies have shown that reduced gibberellin (GA) level or signal promotes plant tolerance to environmental stresses, including drought, but the underlying mechanism is not yet clear. Here we studied the effects of reduced levels of active GAs on tomato (Solanum lycopersicum) plant tolerance to drought as well as the mechanism responsible for these effects. To reduce the levels of active GAs, we generated transgenic tomato overexpressing the Arabidopsis thaliana GA METHYL TRANSFERASE 1 (AtGAMT1) gene. AtGAMT1 encodes an enzyme that catalyses the methylation of active GAs to generate inactive GA methyl esters. Tomato plants overexpressing AtGAMT1 exhibited typical GA-deficiency phenotypes and increased tolerance to drought stress. GA application to the transgenic plants restored normal growth and sensitivity to drought. The transgenic plants maintained high leaf water status under drought conditions, because of reduced whole-plant transpiration. The reduced transpiration can be attributed to reduced stomatal conductance. GAMT1 overexpression inhibited the expansion of leaf-epidermal cells, leading to the formation of smaller stomata with reduced stomatal pores. It is possible that under drought conditions, plants with reduced GA activity and therefore, reduced transpiration, will suffer less from leaf desiccation, thereby maintaining higher capabilities and recovery rates.

Uncovering DELLA-Independent Gibberellin Responses by Characterizing New Tomato procera Mutants

A loss-of-function mutation in the single tomato DELLA gene PROCERA revealed DELLA-related phenotypes and facilitated the identification of DELLA-independent gibberellin responses. Gibberellin (GA) regulates plant development primarily by triggering the degradation/deactivation of the DELLA proteins. However, it remains unclear whether all GA responses are regulated by DELLAs. Tomato (Solanum lycopersicum) has a single DELLA gene named PROCERA (PRO), and its recessive pro allele exhibits constitutive GA activity but retains responsiveness to external GA. In the loss-of-function mutant proΔGRAS, all examined GA developmental responses were considerably enhanced relative to pro and a defect in seed desiccation tolerance was uncovered. As pro, but not proΔGRAS, elongation was promoted by GA treatment, pro may retain residual DELLA activity. In agreement with homeostatic feedback regulation of the GA biosynthetic pathway, we found that GA20oxidase1 expression was suppressed in proΔGRAS and was not affected by exogenous GA3. In contrast, expression of GA2oxidase4 was not affected by the elevated GA signaling in proΔGRAS but was strongly induced by exogenous GA3. Since a similar response was found in Arabidopsis thaliana plants with impaired activity of all five DELLA genes, we suggest that homeostatic GA responses are regulated by both DELLA-dependent and -independent pathways. Transcriptome analysis of GA-treated proΔGRAS leaves suggests that 5% of all GA-regulated genes in tomato are DELLA independent.

Dielectric spectroscopy of microemulsions

The dielectric spectroscopy method (DS) has become a useful technique for the investigation of the structural and dynamic features of the components of both microemulsions and microdroplets over a wide temperature and frequency range. The dielectric parameters obtained by DS determine the geometry of the association structures as well as the overall picture of the dynamics of the different polar groups, aggregates, and association structures representing dipole modes. In this paper the results of a comprehensive study of the different types of microemulsions (ionic and nonionic) by DS are presented. The static and dynamic dielectric properties of microemulsions as a function of temperature, frequency and concentration of water, oil, surfactant and consurfactant are considered. The dielectric properties have been investigated in the frequency range 105–1010 Hz using time domain dielectric spectroscopy (TDDS) and over a broad temperature interval enabling us to cover all the main dynamic processes occurring in such systems. The data treatment for the dynamic behavior of the microemulsions was carried out in the time domain in terms of dipole correlation functions and in the frequency domain in terms of complex dielectric permittivity. The correlation functions of the investigated systems exhibit complex nonexponential relaxation behavior, which must be deconvoluted into normal modes and represented as a sum of the simple exponential, exp (−tτ), and nonexponential terms, exp [−(tτ)]. The parameter ν characterizes the shape of the relaxation function and the cross-corrrelation efects, and describes the morphology of the system. The molecular mechanisms responsible for dielectric polarization in microemulsions of different nature are discussed. Knowledge of the amount of hydrate water and co-surfactant in the interface can be obtained for nonionic microemulsions. In the case of ionic microemulsions. TDDS is a powerful technique for monitoring the organization of clusters and for investigation of relaxation processes involving rearrangement and movement of the droplets forming the clusters.

Solubilization of a dendrimer into a microemulsion.

The present work investigates, for the first time, a system comprising a dendrimer incorporated into the water core of water-in-oil (W/O) microemulsion (ME). A second generation (G-2) poly(propyleneimine) dendrimer (PPI) was solubilized into W/O ME composed of AOT (sodium bis(2-ethylhexyl)sulfosuccinate), heptane, and water. Such a model system possessing the benefits of both dendrimers and ME, can potentially offer superior control of drug administration. The localization of PPI within the system, its specific interactions with the components of the carrier, and its effect on the ME structure was explored by SAXS, DSC, ATR-FTIR, and electrical conductivity measurements. Considerable water binding by PPI, accompanied by partial dehydration of AOT polar heads, was detected by ATR-FTIR and DSC analysis, suggesting that PPI acted as a water pump. In addition, SAXS measurements showed periodicity increase and disordering of the droplets. Hence, localization of PPI within the core and interfacial regions of the droplets was assumed. Direct electrostatic interactions between PPI and the sulfonate group were not noticed, since the dendrimer molecules were mostly not protonated in the current basic environment at pH 12. However, slight hydrogen bonding between PPI and the S=O groups allowed the dendrimer to behave as a spacer between sodium and sulfonate ions. This affected the electrical conductivity behavior of the system, revealing that PPI favored the percolation process. Most likely, PPI decreased the rigidity of the interfacial layer, facilitating the diffusion of sodium ions through the channels. The characterized model system can be advantageously utilized to design specific delivery vehicles, allowing administration of dendrimers as a therapeutic agent from host MEs.

The effect of airflow pattern on filter breakthrough in physical adsorption

Abstract The Wheeler–Jonas (WJ) model for prediction of the protection capacity of organic vapor filters under a fixed airflow was extended to breathing-simulation, pulsating flow. Breakthrough curves of dimethyl-methyl phosphonate (DMMP) and decane were measured under fixed flow and sinusoidal flow. A linear dependence of ln( C X / C 0 ) on the breakthrough time ( t B ) was observed in all the experiments, indicating that the concepts of critical bed weight ( W C ) and dynamic adsorption capacity ( W E ) as defined by the WJ model are applicable to pulsating flow as well. W E was found to be almost unchanged by the flow pattern, whereas W C was considerably larger (by 7–44%) at pulsating flow compared to fixed flow with the same average rate. Thus, shifting from fixed flow to pulsating flow may shorten t B significantly. The effect of the flow type on t B increases with the ratio of the critical weight to the total bed weight. For a high protection level ( C 0 / C X =60u2008000), the protection capacity of personal NBC canisters was reduced by up to 15% upon shifting from fixed to pulsating flow.

The effect of flow pattern on adsorption of dimethyl methyl phosphonate in activated carbon beds and canisters

Abstract Breakthrough times ( t B ) of activated carbon, at constant rate and pulsating (breathing-simulation) flow challenge of dimethyl methyl phosphonate (DMMP), an accepted simulant for organophosphorus warfare agents, were obtained. For personal filter canisters, t B at pulsating flow rates of 30 or 45 lxa0min −1 on the average were found to be shorter than t B obtained at fixed flow rates by 4 and 6%, respectively. The shortening of t B by pulsating flow patterns relative to fixed flow is explained in terms of the critical bed weight as used in the Wheeler-Jonas model. The difference in t B between pulsating and fixed flow rate is expected to increase with decreasing bed depths that approach the critical bed depth.

Dielectric and Calorimetric Characteristics of Bound and Free Water in Surfactant-Based Systems

ABSTRACT The hydration behavior of the system polyoxyethylene (10) oleylalcohol [C18:1 (EO)10 or Brij 97]/water/dodecane/butanol (model system B) was investigated along a dilution line for which the respective weight ratio of dodecane:butanol:Brij 97 is 3:3:4. Two experimental methods were applied: time domain dielectric spectroscopy (TDDS) and sub-zero temperature differential scanning calorimetry (SZT-DSC). Two types of bound water (with melting peaks at -25 and -11°C) were detected by SZT-DSC (using the endothermic mode), whereas TDDS revealed only one such type. Nevertheless, roughly the same total amount of bound water was estimated from these two techniques. The average number of bound water molecules per ethylene oxide (EO) group, NW/EO is 2.3 (TDDS data) or 2.5 (SZT-DSC data) in good agreement with the observation that 1–2 water layers are formed in the hydration of ethoxylated surfactants. We have also shown that butanol is involved in the formation of the bound water that melts at -25°C. We suggest that butanol molecules occupy binding sites within the second hydration shell, thereby reducing the expected total bound water content.

W/O microemulsions as dendrimer nanocarriers: an EPR study.

A complex system, based on a dendrimer solubilized in the aqueous core of water-in-oil microemulsion, may combine the advantages of both dendrimers and microemulsions to provide better control of drug release. We report for the first time the use of EPR technique to determine the effect of solubilized dendrimer on the structure of the microemulsion. The solubilized poly(propyleneimine) (PPI-G2) interacts with sodium bis(2-ethylhexyl) sulfosuccinate (AOT). EPR analysis provided information on polarity, microviscosity, and molecular order of the systems. Polarity and microviscosity increased from unloaded water-in-oil microemulsion to the system loaded with 0.2 wt % PPI-G2, but remained unchanged with higher PPI-G2 loads. The degree of order also increased with 0.2 wt % PPI-G2 with only minor additional increase with larger quantities (25 wt %) of PPI-G2. Variations in pH only slightly affected the structure of microemulsion in the absence and presence of the loaded dendrimers. Aliphatic oils with longer lipophilic chains enhanced the structural order of the microemulsion. On increasing water content, polarity and degree of order increased. PPI-G2 dendrimer in small loads is attracted by the negatively charged AOT and thus intercalates in the interface of the droplets. Yet, at higher PPI-G2 loads, the excess molecules are solubilized in the water core.

Type and Location of Interaction between Hyperbranched Polymers and Liposomes. Relevance to Design of a Potentially Advanced Drug Delivery Nanosystem (aDDnS)

Advanced drug delivery nanosystems (aDDnSs) combining liposomal and dendritic materials have only recently appeared in the research field of drug delivery. The nature and localization of the interactions between the components of such systems are not yet fully described. In this study, liposomes are combined with hyperbranched polyesters for the development of new aDDnSs. The polymer-lipid interactions along with their dependence on the polyesters pseudogeneration number and the liposomal lipid composition have been examined. The results indicate that the interaction between the materials takes place in the headgroup region, where H-bonds between the polymers terminal hydroxyls and the phospholipids phosphate moiety are formed. Due to the polymers compact imperfect structure, which varies with pseudogeneration number, no linear trends are observed with increasing pseudogeneration number. Moreover, it is shown that high percentages of cholesterol in the lipid bilayer affect the penetration of the polymers in the headgroup region.

Decontamination of adsorbed chemical warfare agents on activated carbon using hydrogen peroxide solutions.

Mild treatment with hydrogen peroxide solutions (3-30%) efficiently decomposes adsorbed chemical warfare agents (CWAs) on microporous activated carbons used in protective garments and air filters. Better than 95% decomposition of adsorbed sulfur mustard (HD), sarin, and VX was achieved at ambient temperatures within 1-24 h, depending on the H2O2 concentration. HD was oxidized to the nontoxic HD-sulfoxide. The nerve agents were perhydrolyzed to the respective nontoxic methylphosphonic acids. The relative rapidity of the oxidation and perhydrolysis under these conditions is attributed to the microenvironment of the micropores. Apparently, the reactions are favored due to basic sites on the carbon surface. Our findings suggest a potential environmentally friendly route for decontamination of adsorbed CWAs, using H2O2 without the need of cosolvents or activators.