Natural occurrence of deoxynivalenol, 3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol,nivalenol, 4,7-dideoxynivalenol,and zearalenone in polish wheat

Three wheat samples collected in 1987 in Central Poland and naturally infected withFusarium spp were analyzed for the presence ofFusarium spp andFusarium toxins. Heads were separated into three fractions: kernels with visibleFusarium damage, healthy looking kernels, and chaff + rachis. The samples contained deoxynivalenol (2.0 – 40.0μg/g), nivalenol (O.O1μg/g), 4,7-dideoxynivalenol (0.10 – 0.15μg/g). 15-acetyldeoxynivalenol (0.10–2.00 μg/g), 3-acetyldeoxynivalenol (O/1Oμg/g), and zearalenone (0.01–2.00μg/g). This is the first report about 15 - acetyldeoxynivalenol in European wheat and the co-occurrence of 3 - acetyldeoxynivalenol and 15-acetyldeoxynivalenol in the same sample of contaminated cereals.     

2-Hydroxyglutaryl-CoA dehydratase from Fusobacterium nucleatum (subsp. nucleatum): an iron-sulfur flavoprotein

Anaerobically prepared cell-free extracts from Fusobacterium nucleatum contain 2-hydroxyglutaryl-CoA dehydratase with a specific activity of 20 nkat mg^-1. The enzyme was purified 24-fold to a specific activity of 480 nkat mg^-1 by anion exchange chromatography, gel filtration and chromatography on Blue-Sepharose. The activity of the purified enzyme was strictly dependent on the reductant Ti(III)citrate and stimulated 25-fold by 0.15 mM ATP and 5 mM MgCl₂. ATP is hydrolysed to ADP during incubation with 2-hydroxyglutaryl-CoA dehydratase in the presence or absence of the substrate. The enzyme is extremely sensitive towards oxygen and is inhibited by 10 M chloramphenicol, 10 M 2,4-dinitrophenol or 0.15 mM hydroxylamine. The pure enzyme consists of three subunits (49 kDa), (39 kDa) and (24 kDa) in approximately equal amounts. In this respect the enzyme differs from the related 2-hydroxy-glutaryl-CoA dehydratase from Acidaminococcus fermentans and lactyl-CoA dehydratase from Clostridium propionicum both of which are composed of only two subunits with sizes comparable to those of and but require an additional protein for activity. The relative molecular mass of the native enzyme of about 100 kDa suggests a trimeric -structure. The homogeneous enzyme contains riboflavin (0.5 mol/112 kDa), iron and sulfur (3.5 mol/112 kDa each). Polyclonal antibodies directed against the 2-hydroxyglutaryl-CoA dehydratase from A. fermentans did not crossreact with cell free extracts or purified dehydratase from F. nucleatum. A comparison of the N-terminal amino acid sequences of the dehydratase subunits from A. fermentans and F. nucleatum, however, showed some similarities in the -subunits.Non-standard abbreviations DTT dithiothreitol - PAGE polyaccrylamide gel electrophoresis - VIS visible     

Multiple duplications of yeast hexose transport genes in response to selection in a glucose-limited environment

When microbes evolve in a continuous, nutrient-limited environment, natural selection can be predicted to favor genetic changes that give cells greater access to limiting substrate. We analyzed a population of baker's yeast that underwent 450 generations of glucose-limited growth. Relative to the strain used as the inoculum, the predominant cell type at the end of this experiment sustains growth at significantly lower steady-state glucose concentrations and demonstrates markedly enhanced cell yield per mole glucose, significantly enhanced high-affinity glucose transport, and greater relative fitness in pairwise competition. These changes are correlated with increased levels of mRNA hybridizing to probe generated from the hexose transport locus HXT6. Further analysis of the evolved strain reveals the existence of multiple tandem duplications involving two highly similar, high- affinity hexose transport loci, HXT6 and HXT7. Selection appears to have favored changes that result in the formation of more than three chimeric genes derived from the upstream promoter of the HXT7 gene and the coding sequence of HXT6. We propose a genetic mechanism to account for these changes and speculate as to their adaptive significance in the context of gene duplication as a common response of microorganisms to nutrient limitation.      

Response of a Sphagnum bog plant community to elevated CO2 and N supply

The factors determining herbaceous canopy architecture are poorlyunderstood, especially in natural and semi-natural plant communities. Inthis study, we tested three main hypotheses: (1) the structure of herbaceouscanopies can be explained by the vertical distribution of functional groupsdefined by leaf width and the presence/absence of leaves on upright stem;(2) the degree of canopy stratification is greater in habitats that experiencelower spatial heterogeneity in the supply of light (i.e., grasslands as opposedto forest herb layers); and (3) there is significant variation among specieswithin a growth-form, with respect to their vertical position in thecanopy. We used plant foliage height distribution data from 14 grassland and 13forest herbaceous communities to test these hypotheses. A general linear mixedmodel was applied to specify the proportions of total variance in the foliageheight, accounted for by the fixed effects of plants' basicgrowth-form properties (growth-form) and community type(forest/grassland), and by the random effects of sampling site, samplingpoint, and individual species. We were also interested in the correlation ofthedegree of the stratification with various community characteristics(productivity, other canopy properties, species richness, variation ofspecies' traits) and light availability. There was some evidence ofoverall canopy stratification according toplant growth-form, since plants with leafy stem were locatedsignificantly higher. However, such a pattern of two more or less distinctlayers (grasses + upright forbs and rosette forbs) occurred withconsistency only in grasslands (greater homogeneity in light). Thebetween-species variation within a growth-form was a highlysignificant predictor of canopy vertical structure in the 27 communities. Theproportion of total observed variance, explainable throughspecies-specific effects, was comparable to that caused bybetween-site differences. The effect of community horizontal pattern wasless obvious, but still significant. The site by site analysis revealed thatthe degree to which horizontalpatchiness explained variation in vertical canopy structure was negativelyrelated to the relative importance of species-specific effects, showingthat small between-species differences lead to a more obviouswithin-community horizontal pattern, and vice versa. The upper bound ofthe degree of foliage stratification, according to growth-form, wasrelated to the variability of species light requirements and to relative (tocommunity pool size) richness, indicating that certain aspects of canopyarchitecture might be explained through community species composition anddiversity pattern.     

Towards an integrated perspective of biological conservation and ecological restoration

Biological conservation and ecological restoration differ in their motivations, objectives, and dominant concepts. These differences translate into a dichotomy between the two disciplines in academia, which we illustrate through a review of the scientific literature. Conversely, in practice, conservation and restoration are part of an environmental management continuum and are often used as complementary tools. While we found an increasing transdisciplinary trend in the literature, there is much room for improvement. Optimized implementation of conservation and restoration actions is critical for addressing the increasing pressures of global change and we propose steps to better integrate the two disciplines.     

Focal adhesion kinase signaling controls cyclic tensile strain enhanced collagen I-induced osteogenic differentiation of human mesenchymal stem cells

Focal adhesion kinase (FAK) is a key integrator of integrin-mediated signals from the extracellular matrix to the cytoskeleton and downstream signaling molecules. FAK is activated by phosphorylation at specific tyrosine residues, which then stimulate downstream signaling including the ERK1/2 pathway, leading to a variety of cellular responses. In this study, we examined the effects of FAK point mutations at tyrosine residues (Y397, Y925, Y861, and Y576/7) on osteogenic differentiation of human mesenchymal stem cells exposed to collagen I and cyclic tensile strain. Our results demonstrate that FAK signaling emanating from Y397, Y925, and to a lesser extent Y576/7, but not from Y861, controls osteogenic differentiation through an ERK1/2 pathway, as measured by expression levels of key osteogenesis marker genes and subsequent matrix mineralization. These data indicate that FAK is a critical decision maker in extracellular matrix/strain-enhanced osteogenic differentiation.     

Animated life cycles of fungi and plants with spores for teaching

The conveyance of knowledge of the life cycles performed by fungi and plants with spores is a challenge for teaching in university education. The life cycles of fungi, in particular, can be very complex and difficult to understand. This paper presents the development and implementation of a German and English educational software program, including seven animated life cycles of fungi, two animated developments of fungal meiosporangia, and two examples each for ferns, mosses, and algae (cryptogams). We could show that the use of the software supported the study of fungi and spore-producing plants. It was possible to identify attributes of usability that contributed to a high quality of the educational material in concrete teaching situations. Notably, an easy handling of the software and an appropriate amount of information per animation step are crucial. In addition to the didactic insights, the conversations between the animation designers and the mycologist on correct details of developmental processes in the animations lead to interesting questions concerning cell biology. Some of the resulting open questions are at the edge of currently available knowledge, e.g. concerning the transformation of a plasmodium into a high number of small fruiting bodies in myxomycetes or the dikaryotisation of monokaryotic hyphae after spermatisation in rust fungi.