The phosphorus status of northern hardwoods differs by species but is unaffected by nitrogen fertilization

Northern hardwood forests in the eastern US exhibit species-specific influences on nitrogen (N) cycling, suggesting that their phosphorus (P) cycling characteristics may also vary by species. These characteristics are increasingly important to understand in light of evidence suggesting that atmospheric N deposition has increased N availability in the region, potentially leading to phosphorus limitation. We examined how P characteristics differ among tree species and whether these characteristics respond to simulated N deposition (fertilization). We added NH₄NO₃ fertilizer (50 kg ha^?1 year^?1) to single-species plots of red oak (Quercus rubra L.), sugar maple (Acer saccharum Marsh.), eastern hemlock (Tsuga canadensis (L.) Carr.), American beech (Fagus grandifolia Ehrh.), and yellow birch (Betula alleghaniensis Britt.), in the Catskill Mountains, New York from 1997 to 2007. Species differences were observed in foliar, litter and root P concentrations, but all were unaffected by a cumulative N fertilization of 550 kg/ha. Similarly, measures of soil P availability and biotic P sufficiency differed by species but were unaffected by N fertilization. Results suggest species exhibit unique relationships to P as well as N cycles. We found little evidence that N fertilization leads to increased P limitation in these northern hardwood forests. However, species such as sugar maple and red oak may be sufficient in P, whereas beech and hemlock may be less sufficient and therefore potentially more sensitive to future N-stimulated P limitation.     

Biocontrol of broomrape (Orobanche crenata Forsk. and Orobanche foetida Poir. ) by Pseudomonas fluorescens isolate Bf7-9 from the faba bean rhizosphere

Bacteria of the faba bean (Vicia faba L.)/Orobanche spp. root environment were evaluated for their potential use as biocontrol agents for the parasitic weed. Bacteria were isolated mainly from the rhizosphere of faba bean as well as from diseased Orobanche underground structures and an Orobanche-suppressive soil from three districts of northern Tunisia. Out of 351 bacterial isolates, 337 were tested for pathogenicity in an inverted pyramidal-shape screening programme including a Lactuca sativa L. seedlings bioassay, root-chamber and pot experiments. In pre-selection screening on L. sativa seedlings, 37 isolates (11%) showed a strong growth inhibitory effect, of which 70 and 84% also had a significant suppressive activity on the pre-emergence structures of O. foetida and O. crenata, respectively, in root-chamber experiments. Among five bacterial isolates selected for pot trials, strain Bf7-9 of Pseudomonas fluorescens showed high biocontrol activity against both species of Orobanche and positively influenced faba bean growth. The bacterium reduced shoot emergence of O. crenata and O. foetida by 64 and 76% and their dry weight by 39 and 63%, respectively, compared with non-inoculated controls. Pseudomonas marginalis strain Nc1-2 exhibited also a tendency to reduce incidence of O. crenata and to improve faba bean performance. Results of the present study suggest that application of naturally occurring rhizosphere bacteria offers an additional approach for biocontrol of Orobanche spp. that can supplement current methods of control in an integrated weed management strategy.     

Rapid estimation of numbers of whiteflies (Hemiptera: Aleurodidae) and thrips (Thysanoptera: Thripidae) on sticky traps

The presence or absence of greenhouse whiteflies, Trialeurodes vaporariorum Westwood, and thrips, primarily western flower thrips, Frankliniella occidentalis (Pergande), in cells of a grid laid over 7.6 cm by 12.7 cm sticky traps was used to estimate the population density of these pests on the trap. The method accurately predicted trap population densities of between 15 and 192 individuals per side for thrips on blue and yellow traps and between 15 and 168 whiteflies per side on yellow traps. The distribution of both whiteflies and thrips tended to be clustered on the sides and upper edge of the traps. The method is useful in giving a far more rapid estimate than counting individuals, particularly at high population densities.     

The role of nitric oxide in the regulation of the systemic and pulmonary vasculature of the rattlesnake, <Emphasis Type="Italic">Crotalus durissus terrificus</Emphasis>

The functional role of nitric oxide (NO) was investigated in the systemic and pulmonary circulations of the South American rattlesnake, Crotalus durissus terrificus. Bolus, intra-arterial injections of the NO donor, sodium nitroprusside (SNP) caused a significant systemic vasodilatation resulting in a reduction in systemic resistance (Rsys). This response was accompanied by a significant decrease in systemic pressure and a rise in systemic blood flow. Pulmonary resistance (Rpul) remained constant while pulmonary pressure (Ppul) and pulmonary blood flow (Qpul) decreased. Injection of L-Arginine (L-Arg) produced a similar response to SNP in the systemic circulation, inducing an immediate systemic vasodilatation, while Rpul was unaffected. Blockade of NO synthesis via the nitric oxide synthase inhibitor, L-NAME, did not affect haemodynamic variables in the systemic circulation, indicating a small contribution of NO to the basal regulation of systemic vascular resistance. Similarly, Rpul and Qpul remained unchanged, although there was a significant rise in Ppul. Via injection of SNP, this study clearly demonstrates that NO causes a systemic vasodilatation in the rattlesnake, indicating that NO may contribute in the regulation of systemic vascular resistance. In contrast, the pulmonary vasculature seems far less responsive to NO.     

Delivery of antibodies to the cytosol: Debunking the myths

The use of antibodies to target their antigens in living cells is a powerful analytical tool for cell biology research. Not only can molecules be localized and visualized in living cells, but interference with cellular processes by antibodies may allow functional analysis down to the level of individual post-translational modifications and splice variants, which is not possible with genetic or RNA-based methods. To utilize the vast resource of available antibodies, an efficient system to deliver them into the cytosol from the outside is needed. Numerous strategies have been proposed, but the most robust and widely applicable procedure still remains to be identified, since a quantitative ranking of the efficiencies has not yet been done. To achieve this, we developed a novel efficiency evaluation method for antibody delivery based on a fusion protein consisting of a human IgG₁ Fc and the recombination enzyme Cre (Fc-Cre). Applied to suitable GFP reporter cells, it allows the important distinction between proteins trapped in endosomes and those delivered to the cytosol. Further, it ensures viability of positive cells and is unsusceptible to fixation artifacts and misinterpretation of cellular localization in microscopy and flow cytometry. Very low cytoplasmic delivery efficiencies were found for various profection reagents and membrane penetrating peptides, leaving electroporation as the only practically useful delivery method for antibodies. This was further verified by the successful application of this method to bind antibodies to cytosolic components in living cells.     

Formation of Cystine Slipknots in Dimeric Proteins

We consider mechanical stability of dimeric and monomeric proteins with the cystine knot motif. A structure based dynamical model is used to demonstrate that all dimeric and some monomeric proteins of this kind should have considerable resistance to stretching that is significantly larger than that of titin. The mechanisms of the large mechanostability are elucidated. In most cases, it originates from the induced formation of one or two cystine slipknots. Since there are four termini in a dimer, there are several ways of selecting two of them to pull by. We show that in the cystine knot systems, there is strong anisotropy in mechanostability and force patterns related to the selection. We show that the thermodynamic stability of the dimers is enhanced compared to the constituting monomers whereas machanostability is either lower or higher.     

Global profiling of reactive oxygen and nitrogen species in biological systems: high-throughput real-time analyses

Herein we describe a high-throughput fluorescence and HPLC-based methodology for global profiling of reactive oxygen and nitrogen species (ROS/RNS) in biological systems. The combined use of HPLC and fluorescence detection is key to successful implementation and validation of this methodology. Included here are methods to specifically detect and quantitate the products formed from interaction between the ROS/RNS species and the fluorogenic probes, as follows: superoxide using hydroethidine, peroxynitrite using boronate-based probes, nitric oxide-derived nitrosating species with 4,5-diaminofluorescein, and hydrogen peroxide and other oxidants using 10-acetyl-3,7-dihydroxyphenoxazine (Amplex® Red) with and without horseradish peroxidase, respectively. In this study, we demonstrate real-time monitoring of ROS/RNS in activated macrophages using high-throughput fluorescence and HPLC methods. This global profiling approach, simultaneous detection of multiple ROS/RNS products of fluorescent probes, developed in this study will be useful in unraveling the complex role of ROS/RNS in redox regulation, cell signaling, and cellular oxidative processes and in high-throughput screening of anti-inflammatory antioxidants.     

Three new species of picobiine mites (Acari: Syringophilidae) parasitising African flycatchers (Aves: Muscicapidae)

Three new species of quill mites of the subfamily Picobiinae Johnston & Kethley, 1973 (Acari: Syringophilidae) are described from African flycatchers (Passeriformes: Muscicapidae): Picobia cichladusa n. sp. on Cichladusa arquata Peters and P. myrmecocichla n. sp. on Myrmecocichla arnotti (Tristram), both from Tanzania, and P. echo n. sp. on Cossypha heuglini Hartlaub from the Democratic Republic of the Congo.     

Network-level and population genetics analysis of the insulin/TOR signal transduction pathway across human populations

Genes and proteins rarely act in isolation, but they rather operate as components of complex networks of interacting molecules. Therefore, for understanding their evolution, it may be helpful to take into account the interaction networks in which they participate. It has been shown that selective constraints acting on genes depend on the position that they occupy in the network. Less understood is how the impact of local adaptation at the intraspecific level is affected by the network structure. Here, we analyzed the patterns of molecular evolution of 67 genes involved in the insulin/target of rapamycin (TOR) signal transduction pathway. This well-characterized pathway plays a key role in fundamental processes such as energetic metabolism, growth, reproduction, and aging and is involved in metabolic disorders such as obesity, insulin resistance, and diabetes. For that purpose, we combined genotype data from worldwide human populations with current knowledge of the structure and function of the pathway. We identified the footprint of recent positive selection in nine of the studied genomic regions. Most of the adaptation signals were observed among Middle East and North African, European, and Central South Asian populations. We found that positive selection preferentially targets the most central elements in the pathway, in contrast to previous observations in the whole human interactome. This observation indicates that the impact of positive selection on genes involved in the insulin/TOR pathway is affected by the pathway structure.