Pollen distribution at elevations above 1000 m inSwitzerland

In Switzerland the concentration of allergenic pollendecreases with increasing elevation of the samplingsite of the Swiss pollen measuring network. The aim ofthis study was, to compare the pollen concentrationsof five different localities in the Swiss Alps and inthe Jura mountains, to get an idea of the differencesin the pollen abundance in altitudes above 1000 m. Theinvestigated localities are: La Chaux-de-Fonds(1040 m), Wiesen (1420 m), Davos (1600 m), Samedan(1705 m) and Gütsch (2287 m). These pollen sumswere compared to the Swiss plateau (Basel 273 m).Basel, La Chaux-de-Fonds and Wiesen show clearlyhigher pollen values than Davos, Samedan andGütsch. Pollen concentrations of Corylus,Alnus glutinosa-type and Fraxinus arereduced with increasing altitude and are only a smallproblem for allergies above 1000 m. Betulapollen are also reduced in the higher localities, butthere still occur many days with high pollenconcentrations. Especially Betula pollen frommedium range transport can play an important role forallergies in higher localities. The total grass pollensum does not decrease up to an altitude of 1500 m. Thegrass pollen concentration depends more on factorslike composition of the local grassland, land use andwind situation.Pollen concentrations at higher elevations isinfluenced by the local vegetation, a reduced pollenproduction, land use, topography, exposition, windvelocity and wind direction. These factors modify thepollen concentration considerably. Due to the complextopography of the Prealps and Alps, it is thereforenot possible to propose a general rule of pollenreduction with increasing altitude.     

CXCR7 expression disrupts endothelial cell homeostasis and causes ligand-dependent invasion

The homeostatic function of endothelial cells (EC) is critical for a number of physiological processes including vascular integrity, immunity, and wound healing. Indeed, vascular abnormalities resulting from EC dysfunction contribute to the development and spread of malignancies. The alternative SDF-1/CXCL12 receptor CXCR7 is frequently and specifically highly expressed in tumor-associated vessels. In this study, we investigate whether CXCR7 contributes to vascular dysfunction by specifically examining the effect of CXCR7 expression on EC barrier function and motility. We demonstrate that CXCR7 expression in EC results in redistribution of CD31/PECAM-1 and loss of contact inhibition. Moreover, CXCR7+ EC are deficient in barrier formation. We show that CXCR7-mediated motility has no influence on angiogenesis but contributes to another motile process, the invasion of CXCR7+ EC into ligand-rich niches. These results identify CXCR7 as a novel manipulator of EC barrier function via alteration of PECAM-1 homophilic junctions. As such, aberrant expression of CXCR7 in the vasculature has the potential to disrupt vascular homeostasis and could contribute to vascular dysfunction in cancer systems.     

Why only tetraploid Solidago gigantea (Asteraceae) became invasive: a common garden comparison of ploidy levels

Many studies have compared the growth of plants from native and invasive populations, but few have considered the role of ploidy. In its native range in North America, Solidago gigantea Aiton (Asteraceae) occurs as a diploid, tetraploid and hexaploid, with considerable habitat differentiation and geographic separation amongst these ploidy levels. In the introduced range in Europe, however, only tetraploid populations are known. We investigated the growth performance and life history characteristics of plants from 12 European and 24 North American (12 diploid, 12 tetraploid) populations in a common garden experiment involving two nutrient and two calcium treatments. Twelve plants per population were grown in pots for two seasons. We measured 24 traits related to leaf nutrients, plant size, biomass production and phenology as well as sexual and vegetative reproduction. Native diploid plants had a higher specific leaf area and higher leaf nutrient concentrations than native tetraploids, but tetraploids produced many more shoots and rhizomes. Diploids grown with additional calcium produced less biomass, whereas tetraploids were not affected. European plants were less likely to flower and produced smaller capitulescences than North American tetraploids, but biomass production and shoot and rhizome number did not differ. We conclude that a knowledge of ploidy level is essential in comparative studies of invasive and native populations. While clonal growth is important for the invasion success of tetraploid S. gigantea, its potential was not acquired by adaptation after introduction but by evolutionary processes in the native range.     

p28, A Novel ERGIC/cis Golgi Protein, Required for Golgi Ribbon Formation

The mammalian Golgi apparatus consists of individual cisternae that are stacked in a polarized manner to form the compact zones of the Golgi. Several stacks are linked to form a ribbon via dynamic lateral bridges. The determinants required for maintaining the characteristic Golgi structure are incompletely understood. Here, we have characterized p28, a new γ-subfamily member of p24 membrane proteins. p28 localized to endoplasmic reticulum-Golgi intermediate compartment (ERGIC) and cis Golgi and accumulated in the ERGIC upon Brefeldin A treatment, typical for a protein cycling in the early secretory pathway. p28 interacted with a subset of p24 proteins. Its depletion by small interfering RNA (siRNA) led to fragmentation of the Golgi without affecting the overall organization of microtubules but considerably reducing the amount of acetylated tubulin. The distribution of COPI and tethers, including GM130, was not affected. At the ultrastructural level, the Golgi fragments appeared as mini-stacks with apparently unchanged cis - trans topology. Golgi fragmentation did not impair anterograde or retrograde traffic. Fluorescence recovery after photobleaching (FRAP) experiments revealed that silencing p28 prevents protein exchange between Golgi stacks during reassembly after Brefeldin A-induced Golgi breakdown. These results show that the formation of a Golgi ribbon requires the structural membrane protein p28 in addition to previously identified SNAREs, coat proteins and tethers.     

Proteome analysis of fungal and bacterial involvement in leaf litter decomposition

Fungi and bacteria are key players in the decomposition of leaf litter, but their individual contributions to the process and their interactions are still poorly known. We combined semi‐quantitative proteome analyses (1‐D PAGE‐LC‐MS/MS) with qualitative and quantitative analyses of extracellular degradative enzyme activities to unravel the respective roles of a fungus and a bacterium during litter decomposition. Two model organisms, a mesophilic Gram‐negative bacterium (Pectobacterium carotovorum) and an ascomycete (Aspergillus nidulans), were grown in both, pure culture and co‐culture on minimal medium containing either glucose or beech leaf litter as sole carbon source. P. carotovorum grew best in co‐culture with the fungus, whereas growth of A. nidulans was significantly reduced when the bacterium was present. This observation suggests that P. carotovorum has only limited capabilities to degrade leaf litter and profits from the degradation products of A. nidulans at the expense of fungal growth. In accordance with this interpretation, our proteome analysis revealed that most of the extracellular biodegradative enzymes (i.e. proteases, pectinases, and cellulases) in the cultures with beech litter were expressed by the fungus, the bacterium producing only low levels of pectinases.     

The effect of oligonucleotide microarray data pre-processing on the analysis of patient-cohort studies

Background  

Intensity values measured by Affymetrix microarrays have to be both normalized, to be able to compare different microarrays by removing non-biological variation, and summarized, generating the final probe set expression values. Various pre-processing techniques, such as dChip, GCRMA, RMA and MAS have been developed for this purpose. This study assesses the effect of applying different pre-processing methods on the results of analyses of large Affymetrix datasets. By focusing on practical applications of microarray-based research, this study provides insight into the relevance of pre-processing procedures to biology-oriented researchers.     

Altitudinal distribution of alien plant species in the Swiss Alps

In summer 2003 we recorded the presence and abundance of alien plant species at 232 sites (107 railway stations and 125 road sites) along mountain passes in the Swiss Alps. The altitudinal distribution of species was related to the current abundance of the species in Switzerland and time since introduction. A total of 155 alien taxa were recorded. Numbers of species per site declined exponentially with altitude, and only a few species were found in the alpine zone (>2000 m). In contrast, species richness among comparable native taxa appeared to be nearly independent of altitude over the range investigated. Maximum altitude reached by alien species was related positively to both total area occupied in Switzerland and to time since introduction. A comparison of the results with earlier records suggests that many species, particularly those previously restricted to low or intermediate altitudes, have advanced their altitudinal limits over the past few decades. Various hypotheses are presented to explain the declining abundance of alien species with altitude: low-altitude filter effects, low propagule pressure, and genetic swamping of peripheral populations at higher altitudes. However, at present we do not have sufficient evidence to determine the relative importance of these effects. We conclude that invasion into mountain areas such as the Swiss Alps tends to proceed rather slowly, though the process may be accelerated by climatic warming. For this reason, further research to investigate the processes determining how plants invade mountain areas is urgently needed. And more generally, investigations into the distribution of alien species along strong altitudinal gradients may provide valuable insights into the mechanisms driving the spread of alien organisms.     

Plant functional group composition and large‐scale species richness in European agricultural landscapes

Question: Which are the plant functional groups responding most clearly to agricultural disturbances? Which are the relative roles of habitat availability, landscape configuration and agricultural land use intensity in affecting the functional composition and diversity of vascular plants in agricultural landscapes? Location: 25 agricultural landscape areas in seven European countries. Methods: We examined the plant species richness and abundance in 4 km × 4 km landscape study sites. The plant functional group classification was derived from the BIOLFLOR database. Factorial decomposition of functional groups was applied. Results: Natural habitat availability and low land use intensity supported the abundance and richness of perennials, sedges, pteridophytes and high nature quality indicator species. The abundance of clonal species, C and S strategists was also correlated with habitat area. An increasing density of field edges explained a decrease in richness of high nature quality species and an increase in richness of annual graminoids. Intensive agriculture enhanced the richness of annuals and low nature quality species. Conclusions: Habitat patch availability and habitat quality are the main drivers of functional group composition and plant species richness in European agricultural landscapes. Linear elements do not compensate for the loss of habitats, as they mostly support disturbance tolerant generalist species. In order to conserve vascular plant species diversity in agricultural landscapes, the protection and enlargement of existing patches of (semi‐) natural habitats appears to be more effective than relying on the rescue effect of linear elements. This should be done in combination with appropriate agricultural management techniques to limit the effect of agrochemicals to the fields.     

The terminally redundant, nonpermuted genome of Listeria bacteriophage A511: a model for the SPO1-like myoviruses of gram-positive bacteria

Only little information on a particular class of myoviruses, the SPO1-like bacteriophages infecting low-G+C-content, gram-positive host bacteria (Firmicutes), is available. We present the genome analysis and molecular characterization of the large, virulent, broad-host-range Listeria phage A511. A511 contains a unit (informational) genome of 134,494 bp, encompassing 190 putative open reading frames (ORFs) and 16 tRNA genes, organized in a modular fashion common among the Caudovirales. Electron microscopy, enzymatic fragmentation analyses, and sequencing revealed that the A511 DNA molecule contains linear terminal repeats of a total of 3,125 bp, encompassing nine small putative ORFs. This particular genome structure explains why A511 is unable to perform general transduction. A511 features significant sequence homologies to Listeria phage P100 and other morphologically related phages infecting Firmicutes such as Staphylococcus phage K and Lactobacillus phage LP65. Equivalent but more-extensive terminal repeats also exist in phages P100 (approximately 6 kb) and K (approximately 20 kb). High-resolution electron microscopy revealed, for the first time, the presence of long tail fibers organized in a sixfold symmetry in these viruses. Mass spectrometry-based peptide fingerprinting permitted assignment of individual proteins to A511 structural components. On the basis of the data available for A511 and relatives, we propose that SPO1-like myoviruses are characterized by (i) their infection of gram-positive, low-G+C-content bacteria; (ii) a wide host range within the host bacterial genus and a strictly virulent lifestyle; (iii) similar morphology, sequence relatedness, and collinearity of the phage genome organization; and (iv) large double-stranded DNA genomes featuring nonpermuted terminal repeats of various sizes.     

Crystal Structure of an Anti-Ang2 CrossFab Demonstrates Complete Structural and Functional Integrity of the Variable Domain

Bispecific antibodies are considered as a promising class of future biotherapeutic molecules. They comprise binding specificities for two different antigens, which may provide additive or synergistic modes of action. There is a wide variety of design alternatives for such bispecific antibodies, including the “CrossMab” format. CrossMabs contain a domain crossover in one of the antigen-binding (Fab) parts, together with the “knobs-and-holes” approach, to enforce the correct assembly of four different polypeptide chains into an IgG-like bispecific antibody. We determined the crystal structure of a hAng-2-binding Fab in its crossed and uncrossed form and show that C_H1-C_L-domain crossover does not induce significant perturbations of the structure and has no detectable influence on target binding.