Decline of <Emphasis Type="Italic">Cornus florida</Emphasis> and forest succession in a <Emphasis Type="Italic">Quercus–Carya</Emphasis> forest

Cornus florida is a common understory species in many hardwood forests in eastern North America. It plays an important role in nutrient cycling and is an important food resource for many vertebrate species, especially migratory birds. We used data collected over a 16-year period to examine population dynamics of a tagged population of C. florida in a 6.4 ha area in the context of change in the protected Quercus–Carya forest of the Ross Biological Reserve, Indiana. We examined the hypothesis that forest dynamics result from interactions between long-term ecological succession and pathogens. The C. florida population at the Ross Reserve declined by 50% between 1983 and 2000, with a survivorship of 24%. Analysis of 40 years of forest survey data showed that Quercus and Carya populations declined in importance, while Acer saccharum increased dramatically. This change in forest structure is consistent with successional changes occurring throughout the Midwest and can be attributed to suppression of disturbance. Cornus florida declined more sharply where A. saccharum increased. From 1983 to 1999, C. florida were less likely to survive if they were within 5 m of a A. saccharum. Light measurements showed that A. saccharum abundance correlated negatively with light available to C. florida, suggesting that increased shading by A. saccharum contributed to C. florida decline. The fungus, Discula destructiva causes the disease dogwood anthracnose that is associated with widespread decline of C. florida in the eastern United States. Tests for this pathogen in our study area were mostly negative. Other tests revealed that Armillaria root rot infected most C. florida, but this disease seemed to be a secondary effect of shading by A. saccharum. These results suggest that the lack of fire and other anthropogenic disturbances has resulted in an accelerated shift in dominance from Quercus and Carya to A. saccharum in the main canopy, and this shift, in turn, has resulted in increased shading of C. florida and its decline in previously more open Midwestern forests.     

<Emphasis Type="Italic">Carex</Emphasis> × <Emphasis Type="Italic">involuta</Emphasis> and <Emphasis Type="Italic">Carex juncella</Emphasis> in the flora of Slovakia

The paper brings information on an isolated occurrence and morphological characters of Carex × involuta and C. juncella populations in the Vel’ká Fatra Mts. Their presence has been known neither from the territory of Slovakia nor from the whole Western Carpathians till now.     

Hybridization increases canopy arthropod diversity in the <Emphasis Type="Italic">Quercus affinis</Emphasis> × <Emphasis Type="Italic">Quercus laurina</Emphasis> complex

Understanding the factors that influence the diversity and composition of arthropod communities is a major topic in ecology. Canopy arthropod communities are a major constituent of biodiversity and show great variation in time and space according to different factors. Recently, genetic variation within tree species has attracted attention as a significant factor determining the diversity and composition of canopy arthropod communities. A major source of genetic and phenotypic novelty in plant species is interspecific hybridization, and therefore it is of interest to evaluate how this process affects the communities of associated organisms. In this study, we used microsatellite markers and geometric morphometry of leaf shape to analyze genetic and morphological variation in 45 individuals in a local hybrid zone between the oaks Quercus affinis and Q. laurina in Mexico. Individual trees were assigned to one of the parental species or to the hybrid category. The percentage of leaf area removed by herbivores was quantified in each individual and the canopies of five individuals of each categeory (two parental species and hybrids) was fogged with insecticide to assess the diversity and composition of arthropod communities. Results indicated that hybrid trees experience higher levels of herbivory than parental species and also sustain a higher abundance and richness of canopy arthropods. In general, our study supports the “hybrid susceptibility hypothesis” that predicts a higher incidence of associated arthropods on hybrid plants than in their parental species as result of the disruption of co-adapted gene complexes associated to resistance traits.     

Reactive oxygen and nitrogen species’ effect on <Emphasis Type="Italic">lux</Emphasis>-biosensors based on <Emphasis Type="Italic">Escherichia coli</Emphasis> and <Emphasis Type="Italic">Salmonella typhimurium</Emphasis>

The effect of reactive oxygen and nitrogen species on lux-biosensors based on the Escherichia coli K12 MG1655 and Salmonella typhimurium LT2 host strains was investigated. The bioactivity of exogenous free radicals to the constitutively luminescent E. coli strain with plasmid pXen7 decreased in the order H₂O₂ > OCl^– > NO^? > RОO^? > ONOO^–> O₂^?- while the bioluminescence of S. typhimurium strain transformed with this plasmid decreased in the order NO^? > H₂O₂ > ONOO^– > RОO^? > OCl^– > O₂^?- The cross-reactivity of induced lux-biosensors to reactive oxygen and nitrogen species, the threshold sensitivity and the luminescence amplitude dependences from the plasmid specificity and the host strain were indicated. The biosensors with plasmid pSoxS′::lux possessed a wider range of sensitivity, including H₂O₂ and OCl^–, along with O₂^?- and NO^?. Among the used reactive oxygen and nitrogen species, H₂O₂ showed the highest induction activity concerning to the plasmids pKatG′::lux, pSoxS′::lux and pRecA′::lux. The inducible lux-biosensors based on S. typhimurium host strain possessed a higher sensitivity to the reactive oxygen and nitrogen species in comparison with the E. coli lux-biosensors.     

Stereoselective Inhibition of Cholesterol Esterase by Enantiomers of <Emphasis Type="Italic">exo</Emphasis>- and <Emphasis Type="Italic">endo</Emphasis>-2-Norbornyl-<Emphasis Type="Italic">N</Emphasis>–<Emphasis Type="Italic">n</Emphasis>-butylcarbamates

Four stereoisomers of 2-norbornyl-N–n-butylcarbamates are characterized as the pseudo substrate inhibitors of cholesterol esterase. Cholesterol esterase shows enantioselective inhibition for enantiomers of exo- and endo-2-norbornyl-N–n-butylcarbamates. For the inhibitions by (R)-(+)- and (S)-(−)-exo-2-norbornyl-N–n-butylcarbamates, the R-enantiomer is 6.8 times more potent than the S-enantiomer. For the inhibitions by (R)-(+)- and (S)-(−)-endo-2-norbornyl-N–n-butyl-carbamates, the S-enantiomer is 4.6 times more potent than the R-enantiomer. The enzyme-inhibitor complex models have been proposed to explain these different enantioselectivities.     

Brood cell size of <Emphasis Type="Italic">Apis</Emphasis> <Emphasis Type="Italic">mellifera</Emphasis> modifies the reproductive behavior of <Emphasis Type="Italic">Varroa</Emphasis> <Emphasis Type="Italic">destructor</Emphasis>

We undertook a field study to determine whether comb cell size affects the reproductive behavior of Varroa destructor under natural conditions. We examined the effect of brood cell width on the reproductive behavior of V. destructor in honey bee colonies, under natural conditions. Drone and worker brood combs were sampled from 11 colonies of Apis mellifera. A Pearson correlation test and a Tukey test were used to determine whether mite reproduction rate varied with brood cell width. Generalized additive model analysis showed that infestation rate increased positively and linearly with the width of worker and drone cells. The reproduction rate for viable mother mites was 0.96 viable female descendants per original invading female. No significant correlation was observed between brood cell width and number of offspring of V. destructor. Infertile mother mites were more frequent in narrower brood cells.     

Functional expression of the lipase gene Lip2 of <Emphasis Type="Italic">Pleurotus</Emphasis> <Emphasis Type="Italic">sapidus</Emphasis> in <Emphasis Type="Italic">Escherichia</Emphasis> <Emphasis Type="Italic">coli</Emphasis>

The lipase Lip2 of the edible basidiomycete, Pleurotus sapidus, is an extracellular enzyme capable of hydrolysing xanthophyll esters with high efficiency. The gene encoding Lip2 was expressed in Escherichia coli TOP10 using the gene III signal sequence to accumulate proteins in the periplasmatic space. The heterologous expression under control of the araBAD promoter led to the high level production of recombinant protein, mainly as inclusion bodies, but partially in a soluble and active form. A fusion with a C-terminal His tag was used for purification and immunochemical detection of the target protein. This is the first example of a heterologous expression and periplasmatic accumulation of a catalytically active lipase from a basidiomycete fungus.     

Sequence Analysis of the <Emphasis Type="Italic">Lactoferrin</Emphasis> Gene and Variation of <Emphasis Type="Italic">g</Emphasis>.<Emphasis Type="Italic">7605C</Emphasis>→<Emphasis Type="Italic">T</Emphasis> in 10 Chinese Indigenous Goat Breeds

Much attention has been focused on the study of lactoferrin at the protein or nucleotide level in mice, humans, and cattle, but little is known about it in goats. The goat LF gene from 5' UTR to exon 17 was amplified, and the variation of g.7605C→T in 10 Chinese indigenous goat breeds was analyzed. Among the three ruminant species (cattle, sheep, and goats), the intron-exon distribution pattern was similar, and all the exons had the same length, but the length of introns varied greatly due to insertions or deletions. The frequency of allele T at g.7605C→T (50.12%) was a little higher than that of allele C (49.88%), and the genotype distribution differed greatly between goat populations. The g.7605C→T site showed higher genetic diversity in goat populations. The genetic differentiation was 0.0783, and gene flow was 2.9433 among the 10 Chinese indigenous goat populations.     

Effects of different amino acids on somatic embryogenesis of strawberry (<Emphasis Type="Italic">Fragaria</Emphasis> × <Emphasis Type="Italic">ananassa</Emphasis> Duch.)

This study was conducted to optimize different types and concentrations of amino acids on somatic embryogenesis induction, development and maturation of leaf explants in strawberry cultivars (‘Camarosa’, ‘Paros’ and ‘Kurdistan’). Calli derived from leaf sections were transferred onto MS medium with 1.0 mg/l 2,4-d + 0.5 mg/l BAP supplemented with 0.0, 50, 100, 150 or 200 mg/l concentrations of proline, alanine and glutamine. Stimulation of embryogenesis and embryo development was strictly dependent on the type and concentration of amino acid in the medium. Proline (100 mg/l) was much more effective than glutamine and alanine, on induction and development of somatic embryogenesis in all cultivars. Cultures grown on amino acid-free medium attained lower somatic embryos than cultures grown on amino acid treated medium. Low concentrations (50 mg/l) and high concentrations (200 mg/l) of amino acids tested were inefficient for embryogenesis induction as well as for somatic embryos development.     

Synthesis and Protective Activity of β-Glycosides of <Emphasis Type="Italic">N</Emphasis>-Acetylmuramyl-<Emphasis Type="Italic">L</Emphasis>-Alanyl-<Emphasis Type="Italic">D</Emphasis>-Isoglutamine with Alkylalicyclic and Arylaliphatic Aglycons

The following glycosides of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) were synthesized: β-4-tert-butylcyclohexyl MDP, β-2-(adamant-1-yl)ethyl MDP, β-2,2-diphenylethyl MDP, and β-2-(p-biphenyl) ethyl MDP. The starting peracetylated β-N-acetylglucosaminides were prepared by the oxazoline method. They were converted into 4,6-O-isopropylidene-N-acetyl-D-muramic acids, which were coupled with L-Ala-D-Glu(NH₂)OBn. The target glycopeptides were obtained after their deprotection. The stimulation of the anti-infection resistance of mice against Staphylococcus aureus by the MDP glycosides was studied.     

<Emphasis Type="Italic">In vitro</Emphasis> and <Emphasis Type="Italic">in vivo</Emphasis> inhibition of α-amylases of stored-product mite <Emphasis Type="Italic">Acarus siro</Emphasis>

The stored-product mites are the most abundant and frequent group of pests living on the stored food products in Europe. They endanger public health since they produce allergens and transmit mycotoxin-producing fungi. Novel acaricidal compounds with inhibitory effects on the digestive enzymes of arthropods are a safe alternative to the traditional neurotoxic pesticides used for control of the stored-product pests. In this work, we explored the properties of acarbose, the low molecular weight inhibitor of -amylases (AI), as a novel acaricide candidate for protection of the stored products from infestation by Acarus siro (Acari: Acaridae). In vitro analysis revealed that AI blocked efficiently the enzymatic activity of digestive amylases of A. siro, and decreased the physiological capacity of mites gut in utilizing a starch component of grain flour. In vivo experiments showed that AI suppressed the population growth of A. siro. The mites were kept for three weeks on experimental diet enriched by AI in concentration range of 0.005 to 0.25%. Population growth of A. siro was negatively correlated with the content of AI in the treated diet with a half-population dose of 0.125%. The suppressive effect of AIs on stored-product mites is discussed in the context of their potential application in GMO crops     

A Synthesis of Heteroaromatic <Emphasis Type="Italic">S</Emphasis>- and <Emphasis Type="Italic">N</Emphasis>-β-Glycosides of <Emphasis Type="Italic">N</Emphasis>-Acetylglucosamine under Phase-Transfer Conditions

The use of crown ethers for a phase transfer-catalyzed synthesis of heteroaromatic glycosides of N-acetylglucosamine was studied. The solid-liquid system and catalysis by 15-crown-5 were found to provide for both the 100% conversion of α-D-glucosaminyl chloride peracetate and a high reaction rate. The interaction of α-D-glucosaminyl chloride peracetate and oxadiazole and triazole mercapto derivatives capable of thiol-thione tautomerism carried out at room temperature in acetonitrile in the presence of anhydrous potassium carbonate and crown ethers was shown to lead to both S- and N-glucosides. The structures of the compounds synthesized were confirmed by X-ray analysis and ¹³C and ¹H NMR spectroscopy.     

In vitro growth response of <Emphasis Type="Italic">Phytophthora cactorum</Emphasis>, <Emphasis Type="Italic">P. nicotianae</Emphasis> and <Emphasis Type="Italic">P.</Emphasis> × <Emphasis Type="Italic">pelgrandis</Emphasis> to antibiotics and fungicides

The reactions of isolates of Phytophthora cactorum, P. nicotianae and P. × pelgrandis to metalaxyl, mancozeb, dimethomorph, streptomycin and chloramphenicol were tested to obtain information about the variability of resistance in these pathogens. Distinct genetic groups showed significant differences in resistance to all tested substances except streptomycin. In response to streptomycin, the growth inhibition rates of distinct groups did not differ significantly. The most remarkable differences were detected in the reactions to chloramphenicol and metalaxyl. Discriminant analysis evaluating the effect of all substances confirmed the differences among the groups, which are in agreement with the differences revealed by earlier DNA analyses.     

Conjugal transfer using the bacteriophage ϕC31 <Emphasis Type="Italic">att</Emphasis>/<Emphasis Type="Italic">int</Emphasis> system and properties of the <Emphasis Type="Italic">attB</Emphasis> site in <Emphasis Type="Italic">Streptomyces ambofaciens</Emphasis>

To facilitate molecular genetic studies of Streptomyces ambofaciens that produces spiramycin, a commercially important macrolide antibiotic used in human medicine against Gram-positive pathogenic bacteria, the conditions for the conjugal transfer of DNA from E. coli to S. ambofaciens were established using a bacteriophage ϕC31 att/int system. The transconjugation efficiency of S. ambofaciens varied with the medium used; the highest frequency was obtained on AS-1 medium containing 10 mM MgCl₂ without heat treatment of the spores. In addition, by cloning and sequencing the attB site, we identified that S. ambofaciens contains a single attB site within an ORF coding for a pirin homolog, and its attB site sequence shows 100% nt identity to the sequence of S. coelicolor and S. lividans, which have the highest efficiency in transconjugation using the ϕC31 att/int system.     

A Single and Robust Critical Nitrogen Dilution Curve for <Emphasis Type="Italic">Miscanthus</Emphasis> × <Emphasis Type="Italic">giganteus</Emphasis> and <Emphasis Type="Italic">Miscanthus sinensis</Emphasis>

The sustainable development of miscanthus as a bioenergy feedstock requires optimizing its fertilizer inputs and, therefore, determining its nitrogen (N) requirements. The ‘critical nitrogen dilution curve’ is a powerful tool to characterize such N requirements; it relates the N concentration ([N]) in aboveground organs to their biomass, defining two domains depending on whether the N factor limits biomass growth or not. We aimed to develop such a tool in miscanthus. Using a rhizome N depletion strategy with green cutting pre-treatment over several years before the start of the experiment, we grew, in 2014, two cultivated species, Miscanthus × giganteus (M×g) and Miscanthus sinensis (Msin), at four fertilizer levels (0, 80, 160 and 240 kg N ha^?1). We found a strong nitrogen fertilization effect. The shoot [N] decreased as the aboveground biomass increased in both species and in all of the treatments. [N] was strongly correlated with leaf/stem biomass ratio. The N treatments enabled the identification of the observed critical points, i.e. points with the maximum biomass (W) and the lowest [N], on each measurement date. These points could be fitted to the following critical dilution curve that was common between M×g and Msin: N concentration (Nc) (critical [N], g N kg^?1) = 27.0 W ^?0.48 when W > 1 t ha^?1 and Nc = 27.0 when W ≤ 1. This curve was validated by literature data, separated into N-limited or not-limited conditions. The similarity of the curves between the two species was due to compensation between leaf/stem biomass ratio and [N] in the stems. This curve is helpful to diagnose the crop N status and define the optimal fertilizer requirements of miscanthus crops.     

Carbohydrate and Ethane Release with <Emphasis Type="Italic">Erwinia carotovora</Emphasis> Subspecies <Emphasis Type="Italic">betavasculorum</Emphasis><Emphasis Type="Italic">–</Emphasis>Induced Necrosis

Erwinia carotovora subspecies betavasculorum, also known as E. betavasculorum and Pectobacterium betavasculorum, is a soil bacterium that has the capacity to cause root rot necrosis of sugarbeets. The qualitatively different pathogenicity exhibited by the virulent E. carotovora strain and two avirulent strains, a Citrobacter sp. and an Enterobacter cloacae, was examined using digital analysis of photographic evidence of necrosis as well as for carbohydrate, ethane, and ethylene release compared with uninoculated potato tuber slices. Visual scoring of necrosis was superior to digital analysis of photographs. The release of carbohydrates and ethane from potato tuber slices inoculated with the soft rot necrosis-causing Erwinia was significantly greater than that of potato tuber slices that had not been inoculated or that had been inoculated with the nonpathogenic E. cloacae and Citrobacter sp. strains. Interestingly, ethylene production from potato slices left uninoculated or inoculated with the nonpathogenic Citrobacter strain was 5- to 10-fold higher than with potato slices inoculated with the pathogenic Erwinia strain. These findings suggest that (1) carbohydrate release might be a useful measure of the degree of pathogenesis, or relative virulence; and that (2) bacterial suppression of ethylene formation may be a critical step in root rot disease formation.     

Inheritance of the<Emphasis Type="Italic"> Md-ACS1</Emphasis> gene and its relationship to fruit softening in apple (<Emphasis Type="Italic">Malus</Emphasis> ×<Emphasis Type="Italic"> domestica</Emphasis> Borkh.)

The 1-aminocyclopropane-1-carboxylic acid synthase (ACS) gene is a member of the ACS gene family that is involved in apple (Malus × domestica Borkh.) fruit ripening. Presence of an allele (Md-ACS1-2) of this gene is associated with low internal ethylene concentration in some apple cultivars. In this study, inheritance of Md-ACS1 was determined for 50 apple cultivars/advanced selections and 101 F₁ seedlings from five populations. Following this, the softening pattern of apples stored at 20°C for up to 40 days was examined using 35 fruiting cultivars/selections of defined Md-ACS1 status. Md-ACS1 is inherited in a Mendelian fashion and was found to be linked to fruit softening. Maturity season of genotypes also significantly affected fruit softening. Late-season genotypes in the Md-ACS1-2/2 class had the slowest rate of softening, while early-season Md-ACS1-1/1 genotypes had the most rapid softening rate. The implications of these results are discussed in relation to parental selection and breeding for storage ability in apple.Communicated by H. Nybom     

Laccase-catalyzed carbon–nitrogen bond formation: coupling and derivatization of unprotected <Emphasis Type="SmallCaps">l</Emphasis>-phenylalanine with different <Emphasis Type="Italic">para</Emphasis>-hydroquinones

Unprotected l-phenylalanine was derivatized by an innovative enzymatic method by means of laccases from Pycnoporus cinnabarinus and Myceliophthora thermophila. During the incubation of l-phenylalanine with para-hydroquinones using laccase as biocatalyst, one or two main products were formed. Dependent on the substitution grade of the hydroquinones mono- and diaminated products were detected. Differences of the used laccases are discussed. The described reactions are of interest for the derivatization of amino acids and a synthesis of pharmacological-active amino acid structures in the field of white biotechnology.     

Regeneration of transformed verbena (<Emphasis Type="Italic">Verbena </Emphasis>× <Emphasis Type="Italic">hybrida</Emphasis>) by <Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis>

Verbena (Verbena x hybrida), an important floricultural species, was successfully regenerated from stem segments on Murashige and Skoog's basal medium supplemented with thidiazuron and indole-3-acetic acid. A transformation system was developed using cvs. Temari Scarlet, Temari Sakura, Tapien Rose and TP-P2. Agrobacterium tumefaciens strain Agl0 harboring the sGFP gene was infected into stem segments. Transformation efficiency was improved by evaluating and manipulating the age of the plant material, the concentration of kanamycin in the medium during selection, and the length of the culture period in the dark. After 2-3 months of culture on the selection medium, GFP-positive shoots were obtained in all four of the cultivars tested. These shoots were successfully acclimated and set flowers within 2-3 months in a greenhouse. GFP was expressed in all of the organs including the floral parts. Stable genomic transformation was confirmed by Southern blot analysis. No morphological differences were observed between the transformed plants and their host plants.