Light-dependent oxidative stress determines physiological leaf spot formation in barley

ABSTRACT We reported previously that physiological leaf spot (PLS) formation in winter and spring barley is dependent on genotype-related oxidative stress under field conditions. In the present study, we searched for factors inducing PLS symptoms in the greenhouse similar to those observed in the field and investigated its relationship to reactive oxygen species (ROS) metabolism. We found that in the greenhouse, oxidative stress induced spring barley cv. Extract, which is sensitive to PLS, to express symptoms similar to those observed in the field. Leaves severely affected by PLS showed significantly lower activities of key enzymes in the Halliwell-Asada cycle such as ascorbate peroxidase, glutathione reductase, dehy-droascorbate reductase, and monodehydroascorbate reductase. The sensitive cultivar also showed lower levels of total superoxide dismutase (SOD) and Cu/Zn-SOD activity but a higher level of chloroplast-specific Fe-SOD activity than that of the insensitive cultivar. Thus, an unbalanced ROS metabolism in chloroplasts may trigger PLS incidence in sensitive cultivars, which is in agreement with the fact that light is essential for the induction of PLS expression under both field and greenhouse conditions. Accordingly, under greenhouse conditions, continuous light stress (7 days), but not light shock treatments, induced PLS similar to that of field conditions in sensitive cv. Extract, but not in resistant cv. Scarlett. Light with a high proportion of energy in the blue wavelength spectrum (350 to 560 nm) was significantly more PLS inductive than light with a pronounced red (photosynthetically active radiation) spectrum (580 to 650 nm). Exposure to ozone did not produce PLS-like symptoms. Furthermore, similar to earlier observations in the field, PLS symptom expression was closely correlated with the accumulation of superoxide (O(2) (-)) detected by both biochemical and histochemical assays. Taken together, these data suggest that PLS in barley is genotype-dependent but its expression appears to be induced by certain environmental stress factors, among which photosyn-thetically active radiation plays a major role.     

Bruchpilot promotes active zone assembly, Ca2+ channel clustering, and vesicle release

The molecular organization of presynaptic active zones during calcium influx-triggered neurotransmitter release is the focus of intense investigation. The Drosophila coiled-coil domain protein Bruchpilot (BRP) was observed in donut-shaped structures centered at active zones of neuromuscular synapses by using subdiffraction resolution STED (stimulated emission depletion) fluorescence microscopy. At brp mutant active zones, electron-dense projections (T-bars) were entirely lost, Ca2+ channels were reduced in density, evoked vesicle release was depressed, and short-term plasticity was altered. BRP-like proteins seem to establish proximity between Ca2+ channels and vesicles to allow efficient transmitter release and patterned synaptic plasticity.     

Spin coupling in engineered atomic structures

We used a scanning tunneling microscope to probe the interactions between spins in individual atomic-scale magnetic structures. Linear chains of 1 to 10 manganese atoms were assembled one atom at a time on a thin insulating layer, and the spin excitation spectra of these structures were measured with inelastic electron tunneling spectroscopy. We observed excitations of the coupled atomic spins that can change both the total spin and its orientation. Comparison with a model spin-interaction Hamiltonian yielded the collective spin configuration and the strength of the coupling between the atomic spins.     

The preparation and structures of hydrogen ordered phases of ice

Two hydrogen ordered phases of ice were prepared by cooling the hydrogen disordered ices V and XII under pressure. Previous attempts to unlock the geometrical frustration in hydrogen-bonded structures have focused on doping with potassium hydroxide and have had success in partially increasing the hydrogen ordering in hexagonal ice I (ice Ih). By doping ices V and XII with hydrochloric acid, we have prepared ice XIII and ice XIV, and we analyzed their structures by powder neutron diffraction. The use of hydrogen chloride to release geometrical frustration opens up the possibility of completing the phase diagram of ice.     

Toll-like receptor triggering of a vitamin D-mediated human antimicrobial response

In innate immune responses, activation of Toll-like receptors (TLRs) triggers direct antimicrobial activity against intracellular bacteria, which in murine, but not human, monocytes and macrophages is mediated principally by nitric oxide. We report here that TLR activation of human macrophages up-regulated expression of the vitamin D receptor and the vitamin D-1-hydroxylase genes, leading to induction of the antimicrobial peptide cathelicidin and killing of intracellular Mycobacterium tuberculosis. We also observed that sera from African-American individuals, known to have increased susceptibility to tuberculosis, had low 25-hydroxyvitamin D and were inefficient in supporting cathelicidin messenger RNA induction. These data support a link between TLRs and vitamin D-mediated innate immunity and suggest that differences in ability of human populations to produce vitamin D may contribute to susceptibility to microbial infection.     

Plasma haptoglobin concentration in cattle with surgically corrected torsio uteri intrapartum

In 26 cows with surgically corrected torsio uteri intra partum, severity of disease, wound healing and secondary diseases were correlated with plasma haptoglobin concentration. The objective of the investigation was to determine, if an increased plasma haptoglobin concentration indicates the severity of disease respectively expected wound healing disorders or secondary diseases. The degree of severity of disease was determined by rectally diagnosed elasticity of the uterus before the surgery. In the present investigation, the severity of a uterine torsion intra partum could not be evaluated by determining the plasma haptoglobin concentration. In 9 of 11 days of investigation there was no significant difference in the plasma haptoglobin concentration of animals with an elastic uterus (animals with good prognosis) in contrast to cows with tight uterus (patients with poor prognosis) found. The significant differences on the 6th and 7th day post surgery are related to secondary diseases in patients with poor prognosis, which develop evidently earlier and form stronger. The correlation of all cows with--to those without secondary illnesses shows, that 10 days post surgery patients with secondary diseases have a significant higher plasma haptoglobin concentration (p < 0.05) compared to animals without secondary illnesses. No correlations existed between plasma haptoglobin concentration and wound healing in the examined cattle. A postoperatively increase of haptoglobin indicates a higher risk of secondary illnesses and complications.     

Mechanism of wine lactone formation: demonstration of stereoselective cyclization and 1,3-hydride shift

The cyclization mechanism of (E)-2,6-dimethyl-6-hydroxyocta-2,7-dienoic acid to wine lactone under acidic aqueous conditions was investigated using the two stereoselectively deuterium-labeled precursors (2E,6R,7Z)-[8-2H]-2,6-dimethyl-6-hydroxyocta-2,7-dienoic acid and (2E,7E)-(+/-)-[8-2H]-2,6-dimethyl-6-hydroxyocta-2,7-dienoic acid. A detailed analysis of the generated wine lactone isomers by enantioselective multidimensional gas chromatography (MDGC)/ion trap tandem mass spectrometry demonstrates that the formation of wine lactone proceeds via a nonenzymatic stereoselective cationic cyclization cascade that includes a 1,3-hydride shift. Usually, such mechanisms are features of cyclization reactions that are catalyzed by terpene cyclases. This nonenzymatic conversion of an acyclic precursor to a bicyclic monoterpene under relevant cationic cyclization conditions has rarely been observed and confirms recent suggestions that the precursor itself can provide the chemical functionality required for specific steps in the cyclization cascade.     

Simple prediction of the survival of follicles in cryopreserved human ovarian tissue

This study examines the possible predictive value of the LIVE/DEAD fluorescence viability assay for evaluation of survival of cryopreserved human ovarian tissue. Ovarian tissue from ten patients was examined by LIVE/DEAD viability staining before and after cryopreservation and after freezing in a -20 C freezer (negative control). After cryopreservation with a slow freezing protocol and cryoprotectant the LIVE/DEAD assay showed 86% viable follicles (an intact oocyte and at least more than 50% of the granulosa cells alive), whereas after freezing at -20 C the survival rate was 67%. The healthy follicular loss after cryopreservation was 4%, whereas with freezing at -20 C, it was 25%. Although this assay overestimates the survival rate of cryopreserved primordial follicles, if the LIVE/DEAD assay yields greater than approximately 85% viable follicles, it can be assumed that the follicles in the cryopreserved tissue have maintained their developmental potential and that the tissue is suitable for retransplantation.     

Modeling single-neuron dynamics and computations: a balance of detail and abstraction

The fundamental building block of every nervous system is the single neuron. Understanding how these exquisitely structured elements operate is an integral part of the quest to solve the mysteries of the brain. Quantitative mathematical models have proved to be an indispensable tool in pursuing this goal. We review recent advances and examine how single-cell models on five levels of complexity, from black-box approaches to detailed compartmental simulations, address key questions about neural dynamics and signal processing.     

Crystal structure of a divalent metal ion transporter CorA at 2.9 angstrom resolution

CorA family members are ubiquitously distributed transporters of divalent metal cations and are considered to be the primary Mg2+ transporter of Bacteria and Archaea. We have determined a 2.9 angstrom resolution structure of CorA from Thermotoga maritima that reveals a pentameric cone-shaped protein. Two potential regulatory metal binding sites are found in the N-terminal domain that bind both Mg2+ and Co2+. The structure of CorA supports an efflux system involving dehydration and rehydration of divalent metal ions potentially mediated by a ring of conserved aspartate residues at the cytoplasmic entrance and a carbonyl funnel at the periplasmic side of the pore.