Long-term changes in abundance of bats as revealed by their frequency in tawny owls’ diet

Percentage of bats in tawny owls’ diet was compared in three periods: I — before 1976, II — 1976–1992, III — 1993–2009, by using the published and unpublished material from Poland (only samples over 100 vertebrate prey items). This species of owl showed an opportunistic predation on bats and took them more frequently in periods of higher abundance. Before the mass use of toxic pesticides in Poland, in the period I bats constituted more than 2% of vertebrates in four out of five diet samples (median 2.4%). The lowest bat abundance occurred in Poland in the 1980s and resulted in the lowest percentage of bats taken by owls in the period II (n = 11, median 0.2%). Due to the recovery of bat populations in the period III, the percentage of bats in tawny owls’ diet increased (n = 23, median 0.7%). In large samples (over 200 vertebrate items, n = 21) collected in central and north-eastern Poland the percentage of bats increased from 1980 to 2009 (the estimated average value at the end of that period slightly exceeded 1%). Samples collected at the same five sites in 1975–1992 and again in 2000–2009, confirmed the increasing trend in percentage of bats captured by tawny owls noted in last years.     

Knock-down of protein phosphatase 2A subunit B’γ promotes phosphorylation of CALRETICULIN 1 in Arabidopsis thaliana

Different types of plant pathogens may cause enormous losses in agriculture and also have an ecological impact in the nature. On molecular level, disease resistance is acquired through the action of tightly interconnected signaling pathways that may induce highly specific immune reactions in plant cells. Controlled protein dephosphorylation through protein phosphatase 2A activity is emerging as a crucial mechanism that regulates diverse signaling events in plants. PP2A is predominantly trimeric, and consists of a catalytic subunit, a scaffold subunit A, and a variable regulatory subunit B, which determines the target specificity of the PP2A holoenzyme.¹ Recently, we uncovered a specific role for a regulatory subunit B’γ of PP2A as a negative regulator of immune reactions in Arabidopsis thaliana (hereafter Arabidopsis).² Knock-down pp2a-b’γ mutants show constitutive activation of defense related genes, imbalanced antioxidant metabolism and premature disintegration of chloroplasts upon ageing. Proteomic analysis of soluble leaf extracts further revealed that the constitutive defense response in pp2a-b’γ leaves associates with increased levels of Cu/Zn superoxide dismutase, aconitase as well as components of the methionine-salvage pathway, suggesting PP2A-B’γ modulates methionine metabolism in leaves.     

Structure-activity relationships for the cardiotropic action of the Led-NPF-I peptide in the beetles Tenebrio molitor and Zophobas atratus.

We have examined the effects of the Led-NPF-I peptide (Ala-Arg-Gly-Pro-Gln-Leu-Arg-Leu-Arg-Phe-amide) and a series of ten analogues on the heart contractile activity of Tenebrio molitor and Zophobas atratus, and the structure-activity relationships for cardioactive action of Led-NPF-I were established. A video microscopy technique and computer-based method of data acquisition and analysis were used to study the action of the peptides on continuously perfused heart preparations. Cardiac activity was progressively inhibited by Led-NPF-I when the peptide concentrations were increased from 10(-9) to 10(-5) M. Substitution of the L-proline residue at position 4 of the native peptide with hydroxyproline, valine or D-proline caused a loss of cardioinhibitory activity. Also, replacement of arginine residues at all three positions 2, 7 and 9 with another basic amino acid histidine, reduces cardioinhibitory action of Led-NPF-I. Some modifications of the C-terminal residues, as the Phe(4-NO2)-, Phe(4-NH2)- and Phe(4-NMe2)-analogues, resulted in agonistic peptides with biological activity similar to that of the native peptide. However, three other C-terminal analogues tested [Tyr10]-, [D-Phe10]-Led-NPF-I, and Ala-Arg-Gly-Pro-Gln-Leu-Arg-Leu-Arg-Phe-OH were inactive in the heart bioassay, which suggests that this end of the amino acid chain may play an important role in bioactivity and interaction of the native peptide with its receptor on the myocardium.     

Molecular Mechanism of Heat Shock-Provoked Disassembly of the Coliphage λ Replication Complex

We have found previously that, in contrast to the free O initiator protein of λ phage or plasmid rapidly degraded by the Escherichia coli ClpP/ClpX protease, the λO present in the replication complex (RC) is protected from proteolysis. However, in cells growing in a complete medium, a temperature shift from 30 to 43°C resulted in the decay of the λO fraction, which indicated disassembly of RC. This process occurred due to heat shock induction of the groE operon, coding for molecular chaperones of the Hsp60 system. Here we demonstrate that an increase in the cellular concentration of GroEL and GroES proteins is not in itself sufficient to cause RC disassembly. Another requirement is a DNA gyrase-mediated negative resupercoiling of λ plasmid DNA, which counteracts DNA relaxation and starts to dominate 10 min after the temperature upshift. We presume that RC dissociates from λ DNA during the negative resupercoiling, becoming susceptible to the subsequent action of GroEL/S and ClpP/ClpX proteins. In contrast to λcro⁺, in λcro⁻ plasmid-harboring cells, the RC reveals heat shock resistance. After temperature upshift of the λcrots plasmid-harboring cells, a Cro repressor-independent control of λ DNA replication and heat shock resistance of RC are established before the period of DNA gyrase-mediated negative supercoiling. We suggest that the tight binding of RC to λ DNA is due to interaction of RC with other DNA-bound proteins, and is related to the molecular basis of the λcro⁻ plasmid replication control.     

DNA degradation at elevated temperatures after plasmid amplification in amino acid-starved Escherichia coli cells

Summary Amino acid starvation of Escherichia coli relA mutants may be used as a method for efficient plasmid DNA amplification. Here we demonstrate DNA degradation which occurs at elevated temperatures (42–43°C) after plasmid amplification in amino acid-starved bacteria. These results may explain the previously described low efficiency of plasmid DNA amplification at elevated temperatures.     

The acrAB locus is involved in modulating intracellular acetyl coenzyme A levels in a strain of Escherichia coli CM2555 expressing the chloramphenicol acetyltransferase (cat) gene

Recently, an Escherichia coli CM2555 strain was described as sensitive to chloramphenicol when expressing the chloramphenicol resistance gene (cat) from a multicopy plasmid. This sensitivity was linked to dysfunction of the acrA gene, which encodes a component of the AcrAB-TolC multidrug efflux pump. Preliminary data indicate that the sensitivity phenotype might be due to a decline in intracellular acetyl coenzyme A concentration accompanying the reaction catalyzed by chloramphenicol acetyltransferase, the cat-encoded resistance protein. Here, we demonstrate that the acrA dysfunction is the factor impairing the intracellular acetyl coenzyme A levels in the cat-expressing CM2555 strain. This effect might be alleviated by the interplay of proteins constituting two homologous efflux systems: AcrAB-TolC and AcrEF-TolC. However, our results show also that this is a genetic background-specific phenomenon, as the decrease in acetyl coenzyme A level is not evident in a cat-bearing acrAB derivative of the commonly used strain C600.     

The vanilloid transient receptor potential channel TRPV4: From structure to disease

The Transient Receptor Potential Vanilloid 4 channel, TRPV4, is a Ca²⁺ and Mg²⁺ permeable non-selective cation channel involved in many different cellular functions. It is activated by a variety of physical and chemical stimuli, including heat, mechano-stimuli, endogenous substances such as arachidonic acid and its cytochrome P450-derived metabolites (epoxyeicosatrienoic acids), endocannabinoids (anandamide and 2-arachidonoylglycerol), as well as synthetic α-phorbol derivatives. Recently, TRPV4 has been characterized as an important player modulating osteoclast differentiation in bone remodelling and as a urothelial mechanosensor that controls normal voiding. Several TRPV4 gain-of-function mutations are shown to cause autosomal-dominant bone dysplasias such as brachyolmia and Koszlowski disease. In this review we comprehensively describe the structural, biophysical and (patho)physiological properties of the TRPV4 channel and we summarize the current knowledge about the role of TRPV4 in the pathogenesis of several diseases.     

The Cellular and Physiological Functions of the Lowe Syndrome Protein OCRL1

Phosphoinositide lipids play a key role in cellular physiology, participating in a wide array of cellular processes. Consequently, mutation of phosphoinositide‐metabolizing enzymes is responsible for a growing number of diseases in humans. Two related disorders, oculocerebrorenal syndrome of Lowe (OCRL) and Dent‐2 disease, are caused by mutation of the inositol 5‐phosphatase OCRL1. Here, we review recent advances in our understanding of OCRL1 function. OCRL1 appears to regulate many processes within the cell, most of which depend upon coordination of membrane dynamics with remodeling of the actin cytoskeleton. Recently developed animal models have managed to recapitulate features of Lowe syndrome and Dent‐2 disease, and revealed new insights into the underlying mechanisms of these disorders. The continued use of both cell‐based approaches and animal models will be key to fully unraveling OCRL1 function, how its loss leads to disease and, importantly, the development of therapeutics to treat patients.      

DNA breakage drives nuclear search

The search for a homologous template is a fundamental, yet largely uncharacterized, reaction in DNA double-strand break repair. Two reports now demonstrate that broken chromosomes increase their movement and explore large volumes of nuclear space searching for a homologous template. Break mobility requires resection and recombination enzymes, as well as damage-checkpoint components.