Effects of gap size and associated changes in light and soil moisture on the understorey vegetation of a Hungarian beech forest

In European beech forests windstorms often create canopy gaps and change the level of incident light, soil moisture and nutrient availability on the forest floor. Understanding the interrelations between gap size and environmental change, and the effects these have on regeneration processes is a prerequisite for developing techniques of nature-based forestry. The aims of this study were to investigate the effects of gap size on the resulting spatial distributions of key abiotic environmental variables (light and soil moisture) in gaps, and to study how light and soil moisture affect the abundance and distribution of herb layer species. To do this we used eight artificially created gaps – three large (diameter: 35–40 m) and five small (diameter: 10–15 m) – in a mesotrophic submontane beech forest. Data on species’ importance and substrate types were collected in systematically distributed 1 m×1 m quadrats before gap creation and on four occasions during the next two growing seasons. Hemispherical photographs were taken and analysed to estimate relative light intensity. Soil moisture was measured by frequency domain and capacitance probes. It was found that gap size had a profound effect on the environmental variables measured. While relative light intensity values in small gaps did not reach those in large gaps, soil moisture levels did reach similar maximum values in gap centres regardless of gap size. Richness, composition and total cover of herbaceous vegetation were different in small versus large gaps. Much of this difference was attributed to the presence of specific relative light intensities and also to the increased amount of available soil moisture in gaps. Species were differently affected by the combined effects of light and soil moisture, as well as by differences in available substrates. All this resulted in species-specific distribution patterns within gaps.     

Oxidative DNA cleavage induced by an iron(III) flavonoid complex: synthesis, crystal structure and characterization of chlorobis(flavonolato)(methanol) iron(III) complex

A flavonol iron(III) complex, [Fe(flavonolato)(2)Cl(MeOH)], has been prepared. The compound has been characterized by X-ray crystallography, spectroscopy, magnetism and electronic paramagnetic resonance (EPR) at X- and Q-band. The geometrical environment around the metal is best described as rhombic distorted octahedral. This distortion has also been inferred from the magnetic measurements and from the EPR spectra at different temperatures, E/D(rhombicity parameter) approximately 0.06. The DNA cleavage activity of the iron(III) complex with and without ascorbate/hydrogen peroxide is reported. Mechanisms of the oxidative cleavage have been proposed when DNA strand scission is performed both with and without ascorbate/hydrogen peroxide activation.     

EBP1 regulates organ size through cell growth and proliferation in plants

Plant organ size shows remarkable uniformity within species indicating strong endogenous control. We have identified a plant growth regulatory gene, functionally and structurally homologous to human EBP1. Plant EBP1 levels are tightly regulated; gene expression is highest in developing organs and correlates with genes involved in ribosome biogenesis and function. EBP1 protein is stabilised by auxin. Elevating or decreasing EBP1 levels in transgenic plants results in a dose-dependent increase or reduction in organ growth, respectively. During early stages of organ development, EBP1 promotes cell proliferation, influences cell-size threshold for division and shortens the period of meristematic activity. In postmitotic cells, it enhances cell expansion. EBP1 is required for expression of cell cycle genes; CyclinD3;1, ribonucleotide reductase 2 and the cyclin-dependent kinase B1;1. The regulation of these genes by EBP1 is dose and auxin dependent and might rely on the effect of EBP1 to reduce RBR1 protein level. We argue that EBP1 is a conserved, dose-dependent regulator of cell growth that is connected to meristematic competence and cell proliferation via regulation of RBR1 level.     

Pharmacological profile of the "triple" monoamine neurotransmitter uptake inhibitor, DOV 102,677

1. The molecular and behavioral pharmacology of DOV 102,677 is characterized. 2. This characterization was performed using radioligand binding and neurotransmitter uptake assays targeting the monoamine neurotransmitter receptors. In addition, the effects of DOV 102,677 on extracellular neurotransmitter levels were investigated using in vivo microdialysis. Finally, the effects of DOV 102,677 in the forced swim test, locomotor function, and response to prepulse inhibition was investigated.3. DOV 102,677 is a novel, "triple" uptake inhibitor that suppresses [(3)H]dopamine (DA), [(3)H]norepinephrine (NE) and [(3)H]serotonin (5-HT) uptake by recombinant human transporters with IC(50) values of 129, 103 and 133 nM, respectively. Radioligand binding to the dopamine (DAT), norepinephrine (NET), and serotonin (SERT) transporters is inhibited with k (i) values of 222, 1030, and 740 nM, respectively. DOV 102,677 (20 mg/kg IP) increased extracellular levels of DA and 5-HT in the prefrontal cortex to 320 and 280% above baseline 100 min after administration. DA levels were stably increased for the duration (240 min) of the study, but serotonin levels declined to baseline by 200 min after administration. NE levels increased linearly to a maximum of 348% at 240 min post-dosing. Consistent with these increases in NE levels, the density of beta-adrenoceptors was selectively decreased in the cortex of rats treated with DOV 102,677 (20 mg/kg per day, PO, 35 days). 4. DOV 102,677 dose-dependently reduced the amount of time spent immobile by rats in the forced swim test, a model predictive of antidepressant activity, with a minimum effective dose (MED) of 20 mg/kg and a maximal efficacy comparable to imipramine. This decrease in immobility time did not appear to result from increased motor activity. Further, DOV 102,677 was as effective as methylphenidate in reducing the amplitude of the startle response in juvenile mice, without notably altering motor activity. 5. In summary, DOV 102,677 is an orally active, "balanced" inhibitor of DAT, NET and SERT with therapeutic versatility in treating neuropsychiatric disorders beyond depression.     

Characterization of three Rop GTPase genes of alfalfa (Medicago sativa L.)

Three cDNA clones coding for Medicago sativa Rop GTPases have been isolated. The represented genes could be assigned to various linkage groups by genetic mapping. They were expressed in all investigated plant organs, although at different level. Relative gene expression patterns in response to Sinorhizobium infection of roots as well as during somatic embryogenesis indicated their differential participation in these processes. DNA sequences coding for altogether six different Medicago sp. Rop GTPases could be identified in sequence databases. Based on their homology to each other and to their Arabidopsis counterparts, a unified nomenclature is suggested for Medicago Rop GTPases.     

A yeast-based model of alpha-synucleinopathy identifies compounds with therapeutic potential

We have developed a yeast-based model recapitulating neurotoxicity of alpha-synuclein fibrilization. This model recognized metal ions, known risk factors of alpha-synucleinopathy, as stimulators of alpha-synuclein aggregation and cytotoxicity. Elimination of Yca1 caspase activity augmented both cytotoxicity and inclusion body formation, suggesting the involvement of apoptotic pathway components in toxic alpha-synuclein amyloidogenesis. Deletion of hydrophobic amino acids at positions 66-74 in alpha-synuclein reduced its cytotoxicity but, remarkably, did not lower the levels of insoluble alpha-synuclein, indicating that noxious alpha-synuclein species are different from insoluble aggregates. A compound screen aimed at finding molecules with therapeutic potential identified flavonoids with strong activity to restrain alpha-synuclein toxicity. Subsequent structure-activity analysis elucidated that these acted by virtue of anti-oxidant and metal-chelating activities. In conclusion, this yeast-cell model as presented allows not only fundamental studies related to mechanisms of alpha-synuclein-instigated cellular degeneration, but is also a valid high-throughput identification tool for novel neuroprotective agents.     

Habitat-specific sensory-exploitative signals in birds: propensity of dipteran prey to cause evolution of plumage variation in flush-pursuit insectivores

Sensory exploitation occurs when signals trigger behavioral reactions that diminish the receiver's fitness. Research in this area focuses on the match between the signal's form and the receiver's sensitivity, but the effect of habitat on interspecific sensory exploitation is rarely addressed. Myioborus redstarts use conspicuous wing and tail displays of contrasting black-and-white plumage patches to flush dipteran insects, which are then pursued and captured in flight. Previous studies have shown that by increasing the distance at which insects perform an escape response, conspicuous visual displays improve the birds' foraging performance. We tested the hypothesis that selection for a visual signal that maximizes prey escape distance under local habitat conditions can lead to the evolution of geographic variation in plumage pattern among Myioborus redstarts. Using models of foraging birds, we recorded the escape responses of Dipterous insects to a range of plumage patterns and background tones (from light to dark) to determine whether the plumage pattern that maximizes prey flushing is dependent upon that habitat (background) against which birds are viewed by their prey. Our results indicate that the effectiveness of a particular plumage pattern in flushing dipteran prey depends strongly on the background against which that plumage pattern is displayed, and darker habitat (background) conditions generally favor plumages with more extensive patches of white in the tail. However, the addition of white wing patches that imitate the plumage of the painted redstart (Myioborus pictus) generally increases insect escape responses but reduces the effect that tail pattern variation and background tone have on escape behavior. These experiments support the hypothesis that habitat-specific natural selection to enhance sensory exploitation of prey escape responses could produce geographic variation in plumage patterns of flush-pursuers.     

Characterization of the last step of lignin biosynthesis in Zinnia elegans suspension cell cultures

The last step of lignin biosynthesis in Zinnia elegans suspension cell cultures (SCCs) catalyzed by peroxidase (ZePrx) has been characterized. The k(3) values shown by ZePrx for the three monolignols revealed that sinapyl alcohol was the best substrate, and were proportional to their oxido/reduction potentials, signifying that these reactions are driven exclusively by redox thermodynamic forces. Feeding experiments demonstrate that cell wall lignification in SCCs is controlled by the rate of supply of H(2)O(2). The results also showed that sites for monolignol beta-O-4 cross-coupling in cell walls may be saturated, suggesting that the growth of the lineal lignin macromolecule is not infinite.