Formation of stress ethylene depends both on ACC synthesis and on the activity of free radical-generating system

Leaves of soybean ( Glyxine max. L., var. Progress) were subjected to desiccation, which brought about varying degree of membrane damage as checked with the conductivity method. Progress of injury up to 30% was associated with promotion of ethylene synthesis and with accumulation of 1-aminocyclopropane-1-carboxylic acid (ACC) and 1-(malonylamino)cyclopropane-l-carboxylic acid (MACC) in the cells, as well as with activation of lipoxygenase, the enzyme which is involved in lipid peroxidation and which is capable of forming activated oxygen. The stress-induced promotion of ethylene synthesis was inhibited by the ACC synthase inhibitor aminooxyacetate (AOA). as well as by n-propyl gallate (PG), a free radical scavenger and inhibitor of lipoxygenase. Pretreatment of non-stressed soybean leaves with different concentrations of PG also resulted in the corresponding inhibition of lipoxygenase activity and ethylene formation, the former effect being less pronounced than the latter one. In the tissues pretreated with propyl gallate, the ACC level was not affected, whereas the MACC substantially increased. In leaves showing 40% membrane damage neither lipoxygenase activity nor ethylene synthesis increased any further, despite a further increase in the ACC and MACC levels. Therefore, we propose that there are two prerequisites for effective in vivo synthesis of stress ethylene: promotion of ACC synthesis and activation of a free radical-generating system, which is responsible for the non-enzymatic conversion of ACC to ethylene. The latter effect seems to be due to the activation of the membrane-associated lipoxygenase, which depends on stress-induced alterations in membrane properties.     

High fidelity to wintering,stop-over and breeding sites shown by a Long-billed Curlew Numenius americanus tracked with satellite telemetry on migratory flights across North America

Capsule We studied the migratory movements and site fidelity of a male Long-billed Curlew using satellite telemetry in North America; the bird completed three migratory cycles and showed strong fidelity to stop-over, breeding, and wintering sites, not only on a geographical scale but also on a local scale across the years.     

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Images of bacterial cells stained with KK114 dye and visualized with STED microscopy. On the monitor: large field of view of B. subtilis cells, the KK114 ball‐and‐stick model and the schematics of the STED setup. Different space‐filling representations of the FtsZ protein are also shown. Further details can be found in the article by Massimiliano Lucidi, Radu Hristu, Lorenzo Nichele, George A. Stanciu, Denis E. Tranca, Alina Maria Holban, Paolo Visca, Stefan G. Stanciu, and Gabriella Cincotti ( e202000097 ).

     

ATP involvement in plant tissue responses to low temperature

The effects of chilling and freezing temperature on membrane permeability and ATP content were studied in the leaves of cucumber ( Cucumis sativus L.) and winter rape ( Brassica napus L. var. oleifera L.) leaves, grown at different temperatures. In the winter rape leaves, the endogenous ATP content was modified by application of dinitrophenol (DNP) solutions of different concentrations. The low temperature-induced changes in membrane permeability (as monitored by the conductivity method) were found to be associated with ATP decrease, both in the chilling-sensitive and chilling-resistant (subjected to freezing) plants. In tissues showing reversible injuries, changes in ATP content preceded those in membrane permeability and the adenylate energy charge was affected slightly. In tissues showing irreversible membrane damage, the ATP content was always below 0.4 μmol (g dry weight)⁻¹ and the adenylate energy charge was near 0.5. DNP treatment increased freezing sensitivity of winter rape leaves. In the cold-hardened winter rape leaves, however, freezing and thawing did not significantly affect ATP content or the energy charge, although the specimen showed a rather large increase in membrane permeability. In these leaves ATP content recovered about 20 h after a freezing and thawing treatment. It is proposed that a decrease in ATP supply might be the primary reason for the membrane leakiness at low temperature, both in chilling-sensitive and chilling-resistant (subjected to freezing) plants. The conclusion is, however, not true for the cold-acclimated, frostadapted cells.     

Comparative analysis of uncoupling protein 4 distribution in various tissues under physiological conditions and during development

UCP4 is a member of the mitochondrial uncoupling protein subfamily and one of the three UCPs (UCP2, UCP4, UCP5), associated with the nervous system. Its putative functions include thermogenesis, attenuation of reactive oxidative species (ROS), regulation of mitochondrial calcium concentration and involvement in cell differentiation and apoptosis. Here we investigate UCP4's subcellular, cellular and tissue distribution, using an antibody designed specially for this study, and discuss the findings in terms of the protein's possible functions. Western blot and immunohistochemistry data confirmed that UCP4 is expressed predominantly in the central nervous system (CNS), as previously shown at mRNA level. No protein was found in heart, spleen, stomach, intestine, lung, thymus, muscles, adrenal gland, testis and liver. The reports revealing UCP4 mRNA in kidney and white adipose tissue were not confirmed at protein level. The amount of UCP4 varies in the mitochondria of different brain regions, with the highest protein content found in cortex. We show that UCP4 is present in fetal murine brain tissue as early as embryonic days 12-14 (E12-E14), which coincides with the beginning of neuronal differentiation. The UCP4 content in mitochondria decreases as the age of mice increases. UCP4 preferential expression in neurons and its developmental expression pattern under physiological conditions may indicate a specific protein function, e.g. in neuronal cell differentiation.     

STED nanoscopy of KK114‐stained pathogenic bacteria

Super‐resolution microscopy techniques can provide answers to still pending questions on prokaryotic organisms but are yet to be used at their full potential for this purpose. To address this, we evaluate the ability of the rhodamine‐like KK114 dye to label various types of bacteria, to enable imaging of fine structural details with stimulated emission depletion microscopy (STED). We assessed fluorescent labeling with KK114 for eleven Gram‐positive and Gram‐negative bacterial species and observed that this contrast agent binds to their cell membranes. Significant differences in the labeling outputs were noticed across the tested bacterial species, but importantly, KK114‐staining allowed the observation of subtle nanometric cell details in some cases. For example, a helix pattern resembling a cytoskeleton arrangement was detected in Bacillus subtilis. Furthermore, we found that KK114 easily penetrates the membrane of bacterial microorganism that lost their viability, which can be useful to discriminate between living and dead cells.     

Synthesis, crystal structure and magnetic properties of a 1D mixed-metal-mixed-ligand Ni(II)/Fe(II) coordination polymer built on the nitroprusside anion

A new complex [Ni(L)Fe(CN)₅NO] · 2H₂O (L = 4,6,6-trimethyl-1,9-diamino-3,7-di-aza-nona-3-ene) has been obtained and characterized by means of X-ray crystallographic analysis and magnetochemistry. The Fe(CN)₅NO²⁻ anion links to the Ni(L)²⁺ cation through two bridging cyanide groups in a bent fashion. The intrachain Ni?Ni and interchain Ni?Ni distances are equal to 9.81(8) and 7.75(1) Å, respectively. The magnetic behaviour of the complex indicates the zero field splitting parameter D higher than 3 cm⁻¹ and the average exchange parameter (intra- and interchain) corresponding to direct Ni-Ni magnetic interaction in the crystal lattice equals ∼−0.2 cm⁻¹.     

Dynamics of indirect symptoms of skeletal muscle damage after stretch-shortening exercise

Healthy untrained men (age 20.4 ± 1.7 years, n = 20) volunteered to participate in an experiment in order to establish dynamics of indirect symptoms of skeletal muscle damage (ISMD) (decrease in maximal isometric voluntary contraction torque (MVCT) and torque evoked by electrostimulation at different frequencies and at different quadriceps muscle length, height (H) of drop jump (DJ), muscle soreness and creatine kinase (CK) activity in the blood) after 100 DJs from 0.75 m height performed with maximal intensity with an interval of 20 s between the jumps (stretch-shortening exercise, SSE). All ISMDs remained even 72 h after SSE (P < 0.01–0.001). The muscle experienced greater decrease (P < 0.01) in torque evoked by electrostimulation (at low stimulation frequencies and at short muscle length in particular) after SSE than neuromuscular performance (MVCT and H of DJ) which demonstrated secondary decrease (P < 0.01) in neuromuscular performance during the first 48 h after SSE. Within 24–72 h after the SSE the subjects felt an acute muscle pain (5–7 points approximately) and the CK activity in the blood was significantly increased up to 1200 IU/L (P < 0.001). A significant correlation between decrease in MVCT and H of DJ 24–48 h after SSE on the one hand and muscle soreness registered within 24–48 h after SSE on the other was observed, whereas correlation between the other indirect symptoms of skeletal muscle damage was not significant.