Seasonal physiological responses of Argania spinosa tree from Mediterranean to semi-arid climate

Argania spinosa (the argan tree) is a slow-growing tree endemic of Morocco, growing on semi-arid areas where no other tree species can live. With the aim of predicting temporal changes in A. spinosa woodlands under a probable increase in aridity, we set off to investigate these questions: how do A. spinosa physiological attributes respond to variations in climatic conditions and seasonality, and which is the set of attributes that most affects tree response to environmental conditions? In three study sites, Beni Snassen (North), High-Atlas (Mountain) and Admine Forest in Agadir (Coastal), gas exchange measurements, photochemical efficiency, leaf water potential and different leaf attributes were monitored in February, July and November of 2006. The Mountain site presents the most continental climate. Trees in this site were the most stressed in summer, having the lowest midday leaf water potential values, photochemical efficiency and assimilation rates. We found a Ψ_md threshold around -4 MPa, below which stomatal conductance responds linearly to Ψ_md. Plants from the North area never reached this threshold during the study period. Although leaf pigments presented a clear seasonal pattern, leaves from Coastal trees exhibit the highest content for each season. The three study sites were separated by two discriminate functions obtained by canonical discriminant analysis. In summer, the Mountain population is separated from the other sites mainly by assimilation rate and F_v/F_m, while in winter transpiration rates and chlorophyll content are the main discriminant variables. Our study shows that A. spinosa trees adjust their physiological status and leaf attributes to environmental conditions allowing plants to thrive under a dry climate. Under a scenario of global change, the distribution of the argan tree likely shifts to milder areas.     

Zero‐modified Poisson model: Bayesian approach,influence diagnostics,and an application to a Brazilian leptospirosis notification data

In this paper, a Bayesian method for inference is developed for the zero‐modified Poisson (ZMP) regression model. This model is very flexible for analyzing count data without requiring any information about inflation or deflation of zeros in the sample. A general class of prior densities based on an information matrix is considered for the model parameters. A sensitivity study to detect influential cases that can change the results is performed based on the Kullback–Leibler divergence. Simulation studies are presented in order to illustrate the performance of the developed methodology. Two real datasets on leptospirosis notification in Bahia State (Brazil) are analyzed using the proposed methodology for the ZMP model.     

An Improved Synthesis of 1-β-D-Arabinofuranosylcytosine 5′-Phosphate-L-1,2-diacylglycerols

Abstract

5′-O-MMTr-cytosine arabinoside was prepared on a large scale from 5′-O-MMTr-cytidine with diphenyl carbonate via 5′-protected cytidine-2′,3′-carbonate-aracytidine-2′,2-anhydro derivative at a 67 % yield. The synthesis of 1,2-L-dipalmitoyl-snglycerol, 1,2-L-distearoyl-sn-glycerol and 1,2-L-dioleoyl-sn-glycerol described here using 9-fluorenylmethoxycarbonyl (FMOC) group for protection of 3-position of glycerol which can be selectively removed by Et₃N treatment on the overall 60–70 % yield based on 1.2,-isopropilidene-sn-glycerol. These glycerols were phosphorylated first with 2-chlorophenyl-phosphoro-bis-triazolide quantitatively¹ in order to avoid acyl migration, then the glycerophosphate intermediates were condensed with 2′,3′,N⁴-trileulinyl-l-β-D-arabinofuranosylcytosine in the presence of 2-mesytilenesulphonyl chloride (MsCl) and 1 -methylimidazole (Melm)-which was used in the coupling of nucleotides²-^? in an 85–95 % yield compared with the low yielding diester method of Ryu³. Deblocking was carried out in two steps with tetrabutylammonium fluoride (TBAF) and hydrazine hydrate, producing target compouns (14a, 14b, 14c) at a 50 % yield.     

A spin label study of erythrocyte membranes during simulation of freezing

Summary Human erythrocytes were labeled with stearic acid spin labels, and no change was detected in membrane fluidity under hyperosmotic stress, going from isotonicity to about 3000 mOsm. Intact erythrocytes labeled with an androstane spin label and submitted to simulation of freezing show the onset of irreversible structural breakdown occurring in a saline solution at 2,000 mOsm. Ghosts labeled with maleimide spin label (4-maleimide-2,2,6,6-tetramethylpiperidinooxyl) when submitted to solutions of increasing osmolalities (pH 7.4), exhibit protein conformational changes that are irreversible after a simulated freeze-thaw cycle. After sonication of maleimide spin-labeled ghosts, membrane buried sulfhydryl groups become exposed. Such preparations showed behavior similar to the unsonicated when in saline hyperosmolal medium (pH 7.4). Such results suggest the ionic strength of the medium as the determining factor of the detected conformational changes. Maleimide spin-labeled ghosts in 300 mOsm saline solution (pH 7.4) were treated with ascorbic acid (spin destruction of nitroxides), and the kinetic analysis indicates that 65% of the labeled sites are located at the external interface of the membrane or in hydrophilic channels. Deformation and rearrangements of membrane components in solutions of increasing osmolalities apparently are related to protein conformational changes, on the outside surface of erythrocyte membranes, with a significant amount being structurally dissociated of lipids.     

Detection of hydrogen peroxide by lactoperoxidase-mediated dityrosine formation

The aim of this work was to study the dityrosine-forming activity of lactoperoxidase (LPO) and its potential application for measuring hydrogen peroxide (H₂O₂). It was observed that LPO was able to form dityrosine at low H₂O₂ concentrations. Since dityrosine concentration could be measured in a simple fluorimetric reaction, this activity of the enzyme was utilized for the measurement of H₂O₂ production in different systems. These experiments successfully measured the activity of NADPH oxidase 4 (Nox4) by this method. It was concluded that LPO-mediated dityrosine formation offers a simple way for H₂O₂ measurement.     

Territorial damselflies do not show immunological priming in the wild

Adaptive immunity allows vertebrates to gain protection against repeated pathogenic infections. Analogous responses (priming) have been recently uncovered in invertebrates. However, whether such responses are widespread is not known. The present study investigated the presence of immunological priming in males of a species whose phylogenetic position places it in one of the less derived insect orders. It is hypothesized that the efficiency of such a response could be related to animal condition, as assessed by the expression of a sexually selected ornament. Hetaerina americana Fabricius (Odonata: Calopterygidae) males bear a conspicuous ornament (a red wing spot), which is evolutionarily maintained via male territorial competition. Using field‐collected animals, a group of males is challenged with bacteria before exposure to a higher dose of the same or a different bacteria, and survival is compared with that of infected males not previously challenged, as well as control groups. Gram‐positive and Gram‐negative bacteria are used. To explore how long priming may take to work, the second exposure is carried out either after 1 or 5 days. Red spot and body size are entered in the analysis as predictors of survival within and between groups. There is no difference in survival among groups, which suggests no priming effect. Overall, red spot and body size are not consistent in explaining survival.     

A fungal scent from the cheese

Assembly of microbial communities is shaped by various physical and chemical factors deriving from their environment, including other microbes inhabiting the certain niche. In addition to direct cell–cell contacts, primary and secondary metabolites impact the growth of microbial community members. Metabolites might act as growth-promoting (e.g., cross-feeding), growth-inhibiting (e.g., antimicrobials) or signalling molecules. In multi-species microbial assemblies, secreted metabolites might influence specific members of the community, altering species abundances and therefore the functioning of these microcosms. In the current issue, Cosetta and colleagues describe a unique volatile metabolite-mediated cross-kingdom interaction that shapes the cheese rind community assembly. The study paves the way of our understanding how fungus-produced volatile compounds promote the growth of a certain bacterial genus, a principal connection between community members of the cheese rind.