Chemical Composition Variability of Essential Oils of Daucus gracilis Steinh. from Algeria

The chemical compositions of 20 Algerian Daucus gracilis essential oils were investigated using GC‐FID, GC/MS, and NMR analyses. Altogether, 47 compounds were identified, accounting for 90 – 99% of the total oil compositions. The main components were linalool ( 18 ; 12.5 – 22.6%), 2‐methylbutyl 2‐methylbutyrate ( 20 ; 9.2 – 20.2%), 2‐methylbutyl isobutyrate ( 10 ; 4.2 – 12.2%), ammimajane ( 47 ; 2.6 – 37.1%), (E)‐β‐ocimene ( 15 ; 0.2 – 12.8%) and 3‐methylbutyl isovalerate ( 19 ; 3.3 – 9.6%). The chemical composition of the essential oils obtained from separate organs was also studied. GC and GC/MS analysis of D. gracilis leaves and flowers allowed identifying 47 compounds, amounting to 92.3% and 94.1% of total oil composition, respectively. GC and GC/MS analysis of D. gracilis leaf and flower oils allowed identifying linalool (22.7%), 2‐methylbutyl 2‐methylbutyrate (18.9%), 2‐methylbutyl isovalerate (13.6%), ammimajane (10.4%), 3‐methylbutyl isovalerate (10.3%), (E)‐β‐ocimene (8.4%) and isopentyl 2‐methylbutyrate (8.1%) as main components. The chemical variability of the Algerian oil samples was studied using statistical analysis, which allowed the discrimination of three main Groups. A direct correlation between the altitudes, nature of soils and the chemical compositions of the D. gracilis essential oils was evidenced.     

Degradation pathway and generation of monohydroxamic acids from the trihydroxamate siderophore deferrioxamine B

Siderophores are avid ferric ion-chelating molecules that sequester the metal for microbes. Microbes elicit siderophores in numerous and different environments, but the means by which these molecules reenter the carbon and nitrogen cycles is poorly understood. The metabolism of the trihydroxamic acid siderophore deferrioxamine B by a Mesorhizobium loti isolated from soil was investigated. Specifically, the pathway by which the compound is cleaved into its constituent monohydroxamates was examined. High-performance liquid chromatography and mass-spectroscopy analyses demonstrated that M. loti enzyme preparations degraded deferrioxamine B, yielding a mass-to-charge (m/z) 361 dihydroxamic acid intermediate and an m/z 219 monohydroxamate. The dihydroxamic acid was further degraded to yield a second molecule of the m/z 219 monohydroxamate as well as an m/z 161 monohydroxamate. These studies indicate that the dissimilation of deferrioxamine B by M. loti proceeds by a specific, achiral degradation and likely represents the reversal by which hydroxamate siderophores are thought to be synthesized.     

Cell surface control of the multiubiquitination and deubiquitination of high-affinity immunoglobulin E receptors.

Multiubiquitination of proteins is a critical step leading to selective degradation for many polypeptides. Therefore, activation-induced multiubiquitination of cell surface receptors, such as the platelet-derived growth factor (PDGF) receptor and the T cell antigen (TCR) receptor, may correspond to a degradation pathway for ligand-receptor complexes. Here we show that the antigen-induced engagement of high-affinity immunoglobulin E receptors (Fc epsilon RI) results in the immediate multiubiquitination of Fc epsilon RI beta and gamma chains. This ubiquitination is independent of receptor phosphorylation and is restricted to activated receptors. Surprisingly, receptor multiubiquitination is immediately reversible when receptors are disengaged. Therefore, multiubiquitination and deubiquitination of Fc epsilon RI receptors is controlled at the cell surface by receptor engagement and disengagement. The rapidity, specificity and, most importantly, the reversibility of the activation-induced receptor multiubiquitination suggest that this process may turn on/off a cell surface receptor signaling function thus far unsuspected.     

Tree-growth responses across environmental gradients in subtropical Argentinean forests

Subtropical forests in montane ecosystems grow under a wide range of environmental conditions. However, little is known about the growth responses of subtropical trees to climate along ecological gradients. To assess how, and to what extent climate controls tree growth, we analyzed tree responses to climate for 15 chronologies from 4 different species (Schinopsis lorentzii, Juglans australis, Cedrela lilloi, Alnus acuminata) across a variety of environments in subtropical forests from northwestern Argentina (22–28°S, 64–66°W). Using correlation and principal component analysis, site and species differences in tree-growth responses to precipitation and temperature were determined along the elevation gradient from the dry-warm Chaco lowlands to the wet-cool montane Yungas. Our results show that species responses differ according to the severity in climate conditions along the elevation gradient. At sites with unfavorable conditions, mainly located at the extremes of the environmental gradient, responses of different species to climate variations are similar; in contrast, at sites with relatively mild conditions, tree growth displays a large variety of responses reflecting differences in both local environmental conditions and species physiology. Our research suggests that individualistic responses to environmental variability would determine differences in the type and timing of the responses of dominant trees to climate, which ultimately may shift species’ assemblages in montane subtropical regions of South America under future climate changes.     

Smurf2 regulates stability and the autophagic–lysosomal turnover of lamin A and its disease‐associated form progerin

A‐lamins, encoded by the LMNA gene, are major structural components of the nuclear lamina coordinating essential cellular processes. Mutations in the LMNA gene and/or alterations in its expression levels have been linked to a distinct subset of human disorders, collectively known as laminopathies, and to cancer. Mechanisms regulating A‐lamins are mostly obscure. Here, we identified E3 ubiquitin ligase Smurf2 as a physiological regulator of lamin A and its disease‐associated mutant form progerin (LAΔ50), whose expression underlies the development of Hutchinson‐Gilford progeria syndrome (HGPS), a devastating premature aging syndrome. We show that Smurf2 directly binds, ubiquitinates, and negatively regulates the expression of lamin A and progerin in Smurf2 dose‐ and E3 ligase‐dependent manners. Overexpression of catalytically active Smurf2 promotes the autophagic–lysosomal breakdown of lamin A and progerin, whereas Smurf2 depletion increases lamin A levels. Remarkably, acute overexpression of Smurf2 in progeria fibroblasts was able to significantly reduce the nuclear deformability. Furthermore, we demonstrate that the reciprocal relationship between Smurf2 and A‐lamins is preserved in different types of mouse and human normal and cancer tissues. These findings establish Smurf2 as an essential regulator of lamin A and progerin and lay a foundation for evaluating the efficiency of progerin clearance by Smurf2 in HGPS, and targeting of the Smurf2–lamin A axis in age‐related diseases such as cancer.     

Impacts of the invasive cane toad on aquatic reptiles in a highly modified ecosystem: the importance of replicating impact studies

Invasive species can have dramatic and detrimental effects on native species, and the magnitude of these effects can be mediated by a plethora of factors. One way to identify mediating factors is by comparing attributes of natural systems in species with heterogeneity of responses to the invasive species. This method first requires quantifying impacts in different habitats, ecosystems or geographic locations. We used a long-term, before-and-after study to quantify the impacts of the invasive and toxic cane toad (Rhinella marina) on two predators in a highly modified ecosystem: an irrigation channel in an agricultural landscape. Survey counts spanning 8 years indicated a severe population-level decline of 84 % in Merten’s Water Monitor (Varanus mertensi) that was coincident with the arrival of cane toads. The impact of cane toads on V. mertensi was similar to that found in other studies in other habitats, suggesting that cane toads severely impact V. mertensi populations, regardless of habitat type or geographic location. In contrast, a decline was not detected in the Freshwater Crocodile (Crocodylus johnstoni). There is now clear evidence that some C. johnstoni populations are vulnerable to cane toads, while others are not. Our results reinforce the need for the replication of impact studies within and among species; predicting impacts based on single studies could lead to overgeneralizations and potential mismanagement.     

Porcine odorant-binding protein: structural stability and ligand affinities measured by fourier-transform infrared spectroscopy and fluorescence spectroscopy

Infrared spectra show that the binding of the odorants 2-isobuthyl-3-methoxypyrazine (PYR) and 3,7-dimethyl-1-octanol (DMO) stabilises the tertiary structure of porcine OBP-I against thermal denaturation. The fluorescence emission spectrum of the single tryptophan shows a lambdamax at 337 nm, indicating that the residue is not directly exposed to the solvent. Tryptophan does not appear to be involved in the odorant binding process and it is not accessible to the fluorescence quenchers NaI, CsCl and acrylamide. The binding of the fluorescent dye 1-aminoanthracene (1-AMA), a strong ligand, does not modify the tryptophan fluorescence spectrum. In contrast, the lambdamax of 1-AMA bound to OBP-I is shifted from 537 to 481 nm, with a lambdamax intensity increase by a factor of 80. Bound 1-AMA is displaced by odorant molecules in competitive binding assays and can be employed in simple and rapid binding assay, avoiding the use of radioactive ligands. The Scatchard plot shows that 1-AMA binds to OBP-I with a dissociation constant of 1.3 microM and an equimolar stoichiometry.     

Analysis of the essential oil from the roots of Eupatorium cannabinum subsp. corsicum (L.) by GC, GC-MS and 13C-NMR

Eupatorium cannabinum subsp. corsicum (L.) is an endemic subspecies from the island of Corsica. The essential oil from the roots of this aromatic plant has been studied by GC, GC-MS and by 13C-NMR. In contrast to the essential oil from the aerial parts, which is dominated by hydrocarbon compounds (76.9%) and particularly by sesquiterpene components (43.3%), the essential oil from the roots was characterized by a high content of oxygenated compounds (61.0%), particularly oxygenated monoterpenes (54.0%). In the root oil, 106 components were identified representing 96.1% of the total amount. This oil was dominated by the monoterpenes esters (33%), the major components of which were neryl isobutyrate (17.6%), thymyl methyl oxide (15.1%), delta-2-carene (14.5%) and beta-pinene (5.7%). Aromatic esters, nerol derivatives (esters and diesters) and a benzofuran were investigated by GC-MS using different ionization modes including electron impact ionization, and positive- and negative-chemical ionization. These components have not previously been reported in the essential oil of aerial parts of E. cannabinum from Corsica island.     

The epsilon hinge-ear region regulates membrane localization of the AP-4 complex

Adaptor protein (AP) complexes are key factors for the spatial and temporal regulation of intracellular trafficking events. Four complexes (AP-1, -2, -3, -4) are known, among which AP-4 is only poorly characterized. Recent work suggests a role for AP-4 in the intracellular trafficking of the β-amyloid precursor protein and molecular genetics showed that the loss of functional AP-4 is associated with congenital neuronal disorders of severe cognitive dysfunction. To unravel the molecular mechanisms controlling AP-4 functions, we established the intracellular expression of recombinant AP-4 complex. This approach combined with the analysis of mutant complexes allowed us to discover that the epsilon adaptin hinge-ear region has a function in membrane recruitment of AP-4. We further show that this process is phosphorylation dependent and involves PP2A-like protein phosphatases and a staurosporine-sensitive kinase. Deletion of the residues 839-871 in the carboxy-terminal region of the hinge of epsilon adaptin abrogated the membrane/cytosol recycling of AP-4. As targets of phosphorylation, we identified three serine residues: S847, S868 and S871. We conclude that the terminal hinge region and the appendage of the AP-4 epsilon subunit are involved in membrane association in a process that is controlled by phosphorylation and dephosphorylation events.     

Microbial activity in Eastern Venezuelan savannas turned into grasslands

We studied the effects of season and management practices on chemical properties and biochemical parameters in a typical Ultisol soil of native and introduced pastures of the Eastern savannas of Venezuela. Sseason, soil management, and their interaction, significantly affected chemical properties and biochemical parameters. The total carbon and the water soluble carbon experienced a significant decrease during the wet period. The basal respiration, the arginine ammonification (AA) and the fluoriscein diacetate hydrolysis showed a relatively low microbial activity. The transformation of native savannas to pastures systems of B. brizantha and S. capitata increased the organic matter content in soil. The AA and the basal respiration were sensible indicators to estimate changes in soil quality and also reflected the interaction of temporal changes and management practices.