Variability and ecology of the alpine dwarf shrub community Loiseleurio-Cetrarietum

Summary Variation in the dwarf shrub community Loiseleurio-Cetrarietum from Mt. Patscherkofel, Austria, was investigated using polar ordination, principal component analysis, hierarchical cluster analysis, and multiple correlation analysis. Comparison was made with existing data (relevé tables) from the Alps. In addition to phytosociological methods the canopy structure and the morphological variability of the dominant species Loiseleuria procumbens were studied. The result of the namerical phytosociological analyses yield 3 clusters representing: 1) A dense Loiseleuria carpet, 2) a Loiseleuria carpet damaged by erosion and 3) an open Loiseleuria community on skeletal soils. The first two communities can be combined as one type because of their canopy structure in the form of dense intertwined individual plants and because of the morphological uniformity of Loiseleuria, although in the second group there are species growing on erosion gaps and showing close floristic connections to the third group. The comparison of 140 relevés from the Alps proves that the Loiseleurio-Cetrarietum is characterized only by the dominance of Loiseleuria procumbens while the abundantly occurring lichens change in their species composition along the gradient of wind, and elevation. The open Loiseleuria community at the most extreme habitats (cluster 3) is regarded as a new association. Not only floristic but also physiognomical, morphological and ecophysiological evidence led to this conclusion. The name Gymnomitrio-Loiseleurietum (ass. prov.) is proposed. This plant community shows floristic and ecological correlations to the Diapensia-Loiseleuria-Cesiolichen community known from Scandinavia.Nomenclature of species follows Ehrendorfer (1973) (vascular plants), Poelt (1974) (lichens) and Gams (1973) (mosses).For PCA, hierarchical cluster analysis, and multiple correlation analysis, computer programs from the data bank system (AFO-data) of the Alpine Forschungsstelle Obergurgl, Austria were used. I am indebted to Dr. S. Pamer and P. Moser for their invaluable help. For polar ordination a separate program was developed (language: Simula, author: Dr. G. Knecht). I am also indebted to Dr. H. Hilscher for the translation of the text.     

The impact of trampling by tourists on a high altitudinal grassland in the Tyrolean Alps,Austria

The long term effect of tourist trampling on a high altitudinal grassland (Caricion curvulae) in the Tyrolean Alps was investigated.Even under slight trampling the frequency of sensitive species decreases. The most sensitive species were found to be fruticose lichens, followed by mosses, some forbs and broadleaved grasses. Tolerant to trampling are the dominant species Carex curvula, and Ligusticum mutellina, which do not disappear completely even at a tourist frequency of 150 tourists per metre per day. Trampling increases soil bulk density moderately but has no marked effect on the soil water content.Comparison with high alpine sedge heath vegetation in North America shows a surprising uniformity of this vegetation type in response to trampling and also indicates that the common generalisation that alpine ecosystems are fragile and sensitive to disturbance does not hold true in this context. Furthermore these results represent evidence against the theory that ecosystems with low diversity are much more sensitive to arteficial impact than ecosystems with high diversity. However, if even the most resistant plants which are the dominant sedges are destroyed completely the rate of recovery is very low and may last for a long time. In the case of Carex curvula this is supported by the fact that it has very low seed production and grows mainly vegetatively. The rate of spread of the rhizome system of this species is 8 mm in 10 years. Similar figures may apply for the sedge species dominating in the alpine vegetation of North America. Thus fragility of this vegetation in regard to trampling does not mean low tolerance but low regeneration.Nomenclature of species follows Ehrendorfer (1973) for vascular plants and Poelt (1974) for lichens.The PCA calculations were done at the Computer laboratory of the University of Wales during a post doctoral stay at the School of Plant Biology in Bangor, U.K. I would like to record my thanks to Prof. Dr. P. Greig-Smith for fruitful discussions and reading the draft.     

Altering the surface properties of baculovirus Autographa californica NPV by insertional mutagenesis of the envelope protein gp64.

The envelope protein gp64 of the baculovirus Autographa californica nuclear polyhedrosis virus is essential for viral entry into insect cells, as the glycoprotein both mediates pH-dependent membrane fusion and binds to host cell receptors. Surface modification of baculovirus particles by genetic engineering of gp64 has been demonstrated by various strategies and thus has become an important and powerful tool in molecular biology. To improve further the presentation of peptides on the surface of baculovirus particles, several insertion sites within the gp64 envelope protein were selected by their theoretical maximum surface probability and investigated for efficient peptide presentation. The ELDKWA peptide of the gp41 of HIV-1, specific for the human mAb 2F5, was inserted into 17 different positions of the glycoprotein gp64. Propagation of viruses was successful in 13 cases, mutagenesis at four positions did not result in production of intact virus particles. Western blotting, FACS analysis and ELISA were used for characterization of the different binding properties of the mutants. Insertion of this peptide into the native envelope protein resulted in high avidity display on the surface of baculovirus particles. This approach offers the possibility of effective modification of surface properties in regard to host range specificity and antigen display.     

Genetic structure of the vairone Telestes souffia in the eastern part of Lake Constance, central Europe

Examination of the genetic structure of the vairone Telestes souffia based on 10 nuclear markers (microsatellites) revealed little-to-moderate genetic differentiation between geographically adjacent populations in the eastern part of Lake Constance in central Europe. Results emphasize the critically endangered status of this freshwater fish in the upper Rhine River system.     

Expression and characterization of the first snail-derived UDP-N-acetyl-α-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase

UDP-GalNAc:polypeptide GalNAc transferase (ppGalNAcT; EC 2.4.1.41) catalyzes the first step in mucin-type O-glycosylation. To date, several members of this large enzyme family have been analyzed in detail. In this study we present cloning, expression and characterization of the first representative of this type of glycosyltransferase from mollusk origin, namely from Biomphalaria glabrata. The full length sequence of the respective gene was obtained by screening of a cDNA library using homology-based PCR. The entire gene codes for a protein consisting of 600 amino acids comprising the features of a typical type II membrane protein containing a cytoplasmic tail at the N-terminus, a transmembrane and a catalytic domain as well as a ricin-like motif at the C-terminus. Sequence comparison with ppGalNAcTs from various species revealed high similarities in terms of structural architecture. The enzyme is O-glycosylated but does not have any putative N-glycosylation sites. All four tested acceptor peptides were functional substrates, with Muc2 being the best one. Further biochemical parameters tested, confirmed a close relationship to the family of yet known ppGalNAcTs.     

Enhancement of solubility in <Emphasis Type="Italic">Escherichia coli</Emphasis> and purification of an aminotransferase from <Emphasis Type="Italic">Sphingopyxis</Emphasis> sp. MTA144 for deamination of hydrolyzed fumonisin B<Subscript>1</Subscript>

Background  

Fumonisin B₁ is a cancerogenic mycotoxin produced by Fusarium verticillioides and other fungi. Sphingopyxis sp. MTA144 can degrade fumonisin B₁, and a key enzyme in the catabolic pathway is an aminotransferase which removes the C2-amino group from hydrolyzed fumonisin B₁. In order to study this aminotransferase with respect to a possible future application in enzymatic fumonisin detoxification, we attempted expression of the corresponding fumI gene in E. coli and purification of the enzyme. Since the aminotransferase initially accumulated in inclusion bodies, we compared the effects of induction level, host strain, expression temperature, solubility enhancers and a fusion partner on enzyme solubility and activity.     

Baculovirus surface display: construction and screening of a eukaryotic epitope library.

The baculovirus expression system was utilized to serve as a tool for ligand selection, demonstrating the applicability of the system to the generation and screening of eukaryotic expression libraries. The HIV-1-gp41 epitope 'ELDKWA', specific for the neutralizing human mAb 2F5, was inserted into the antigenic site B of influenza virus hemagglutinin and expressed on the surface of baculovirus infected insect cells. In order to improve the antigenicity of the epitope within the hemagglutinin, and therefore enhance the specific binding of 2F5, we inserted three additional, random amino acids adjacent to the epitope. This pool of hemagglutinin genes was directly cloned into the baculovirus Ac-omega. To identify distinct proteins displayed on the cellular surface, we developed a screening protocol to select for specific binding capacity of individual viral clones. Using fluorescence activated cell sorting (FACS) we isolated a baculovirus clone displaying the epitope with markedly increased binding capacity out of a pool of 8000 variants in only one sorting step. Binding properties of the identified ligand were examined by FACS performing a competition assay.     

Rational Vector Design for Efficient Non-viral Gene Delivery: Challenges Facing the Use of Plasmid DNA

Although non-viral gene delivery is a very straightforward technology, there are currently no FDA-approved gene medicinal products available. Therefore, improving potency, safety, and efficiency of current plasmid DNA vectors will be a major task for the near future. This article will provide an overview on factors influencing production yield and quality as well as safety issues that emerge from the vector design itself. Special focus will be on generating bacterial pDNA vectors by circumventing the use of antibiotic resistance genes, to generate safer gene medicinal products as well as smaller, more efficient DNA vectors.     

Baculovirus display strategies: Emerging tools for eukaryotic libraries and gene delivery.

Recombinant baculoviruses have been extensively used as vectors for abundant expression of a large variety of foreign proteins in insect cell cultures. The appeal of the system lies essentially in easy cloning techniques and virus propagation combined with the eukaryotic post-translational modification machinery of the insect cell. Recently, a novel molecular biology tool was established by the development of baculovirus surface display, using different strategies for presentation of foreign peptides and proteins on the surface of budded virions. This eukaryotic display system enables presentation of large complex proteins on the surface of baculovirus particles and has thereby become a versatile system in molecular biology. Surface display strategies play an important role, as they may be used to enhance the efficiency and specificity of viral binding and entry to mammalian cells. In addition, baculovirus surface display vectors have been engineered to contain mammalian promoter elements designed for gene delivery both in vitro and in vivo. Moreover, baculovirus capsid display has recently been developed; this holds promise for intracellular targeting of the viral capsid and subsequent cytosolic delivery of desired protein moieties. Finally, the viruses can accommodate large insertions of foreign DNA and replicate only in insect cells. Together, these are attributes that are very likely to make them important tools in functional genomics and proteomics.