Activities of cell wall degrading enzymes in autolyzing cultures of three Fusarium culmorum isolates: growth-promoting, deleterious and pathogenic to rye (Secale cereale)

Release of cell wall degrading enzymes, CWDE, (glucanases, chitinases, xylanases, endocellulases, exocellulases, pectinases and polygalacturonases) was compared for three Fusarium culmorum isolates, two nonpathogenic rhizosphere isolates (a plant growth promoting [PGPF] and a deleterious [DRMO]) and one root pathogen, grown on media supplemented with one of these C sources: glucose, chitin, plant (rye root) and fungal (Fusarium) cell wall. The degree of autolysis determined after 42 d in the medium containing glucose was 15% for PGPF and DRMO and 20% for pathogenic isolate. The organic compounds added to the growth medium differentially affected the activity of the individual enzymes released by the particular isolates. The activities of xylanases and endocellulases released to the plant cell wall-amended medium by the PGPF isolate were significantly lower than the activities of these enzymes released by the DRMO and the pathogenic isolates. The activity of pectinases was repressed by glucose. The activities of acidic hydrolases were greater than those of alkaline hydrolases. Principal component analysis revealed that the activities of the CWDE found in the supernatants of the autolyzing F. culmorum cultures could be clustered into two distinct groups. One group included pectinase, exocellulase and polygalacturonase and all the remaining tested hydrolases in the other, suggesting that enzymes from either group might act in synergy during cell wall degradation. The differences in the activities of the individual CWDE released to the culture by the particular isolates are considered to be one of the key factors responsible for the observed types of plant-fungal interactions.     

Burrowing by badgers (Meles meles) and foxes (Vulpes vulpes) changes soil conditions and vegetation in a European temperate forest

This study examined the effects of burrow digging and habitation by the European badger (Meles meles) and the red fox (Vulpes vulpes) on soil properties and the plant community. The vegetation of control plots located in a similar but undisturbed habitat was compared with that of 18 burrow plots established at badger setts (N = 9) and fox dens (N = 9) in a lowland forest area in Poland. Soil physicochemical properties at different disturbance levels (mounds, intermounds and reference areas) were also investigated. The animals altered nutrient availability in the burrow plots considerably by excavating material from deep soil horizons that were less acidic and higher in K, Ca, Mg and available P but poorer in C and N. The effect was stronger for the badger, probably because it displaced larger amounts of material and disturbed wider areas. The activity of the two carnivores induced similar changes in plant communities. They increased herbaceous species richness and caused a shift in the herbaceous species composition: versus the control plots, the burrow plots contained more fugitive species (short-living plants typical for disturbed environments), among which ruderal forbs, including nutrient-demanding species, dominated. The carnivores also increased the species richness of fleshy-fruited shrubs and trees. The primary reason for this was probably not burrowing but endozoochorous seed dispersal. Overall, the results indicate that the badger setts and fox dens differ significantly from the forest matrix in terms of soil and vegetation parameters, and that they contribute to habitat heterogeneity and biological diversity.     

Platypus globin genes and flanking loci suggest a new insertional model for beta-globin evolution in birds and mammals

Background  

Vertebrate alpha (α)- and beta (β)-globin gene families exemplify the way in which genomes evolve to produce functional complexity. From tandem duplication of a single globin locus, the α- and β-globin clusters expanded, and then were separated onto different chromosomes. The previous finding of a fossil β-globin gene (ω) in the marsupial α-cluster, however, suggested that duplication of the α-β cluster onto two chromosomes, followed by lineage-specific gene loss and duplication, produced paralogous α- and β-globin clusters in birds and mammals. Here we analyse genomic data from an egg-laying monotreme mammal, the platypus (Ornithorhynchus anatinus), to explore haemoglobin evolution at the stem of the mammalian radiation.     

Colonization of root tissues and protection against Fusarium wilt of rye (Secale cereale) by nonpathogenic rhizosphere strains of Fusarium culmorum

Colonization of rye (Secale cereale) tissues by nonpathogenic rhizosphere Fusarium culmorum isolates DEMFc2 and DEMFc5 and a pathogenic strain DEMFc37, and their effect on plant fresh weight were studied in pot experiments. Both rhizosphere isolates colonized the epidermis and the cortex but were not found in vessels, while the pathogen colonized all three layers of root cells. The numbers of pathogen CFU isolated from plant tissues were much higher than those of the rhizosphere isolates in spite of the same number of macroconidia used as inoculum (1 × 10⁵ g⁻¹ of soil). Inoculation of seedlings with DEMFc2 resulted in a 20% increase, with DEMFc5 in more than a 20% reduction, and with DEMFc37 in a 38% reduction of shoot fresh weight of 14-day-old plants. Pre-colonization of plants with (either of) the rhizosphere isolates and subsequent inoculation with the pathogen resulted in plant weights the same as those observed in plants inoculated with the rhizosphere strain alone. The disease severity index for shoots of plants pre-colonized with DEMFc2 was reduced from class 4 (86% diseased plants) observed for plants inoculated with the pathogen alone to class 2 (average of 8% diseased plants) when pre-treated with the rhizosphere strain. The CFU number of the pathogen isolated from the interior of roots of plants pre-colonized with the rhizosphere isolates was as low as 10% of the number isolated from plants inoculated with the pathogen alone. A study of in vitro interactions between the rhizosphere isolates and the pathogen suggests that changes in plant colonization by the pathogen and its effect on fresh weight of plants pre-colonized with the rhizosphere isolates were not connected with inhibition of its growth by a direct action of the rhizosphere isolates. The results suggest that strain DEMFc2 can be considered as a potential biocontrol agent.     

Hierarchical analysis of variation in the mitochondrial 16S rRNA gene among Hymenoptera

Nucleotide sequences from a 434-bp region of the 16S rRNA gene were analyzed for 65 taxa of Hymenoptera (ants, bees, wasps, parasitoid wasps, sawflies) to examine the patterns of variation within the gene fragment and the taxonomic levels for which it shows maximum utility in phylogeny estimation. A hierarchical approach was adopted in the study through comparison of levels of sequence variation among taxa at different taxonomic levels. As previously reported for many holometabolous insects, the 16S data reported here for Hymenoptera are highly AT-rich and exhibit strong site-to-site variation in substitution rate. More precise estimates of the shape parameter (alpha) of the gamma distribution and the proportion of invariant sites were obtained in this study by employing a reference phylogeny and utilizing maximum-likelihood estimation. The effectiveness of this approach to recovering expected phylogenies of selected hymenopteran taxa has been tested against the use of maximum parsimony. This study finds that the 16S gene is most informative for phylogenetic analysis at two different levels: among closely related species or populations, and among tribes, subfamilies, and families. Maximization of the phylogenetic signal extracted from the 16S gene at higher taxonomic levels may require consideration of the base composition bias and the site-to-site rate variation in a maximum-likelihood framework.      

A high-throughput microscale method to release N-linked oligosaccharides from glycoproteins for matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis

This report describes a convenient method for the rapid and efficient release of N-linked oligosaccharides from low microgram amounts of glycoproteins. A 96-well MultiScreen assay system containing a polyvinylidene difluoride (PVDF) membrane is employed to immobilize glycoproteins for subsequent enzymatic deglycosylation. Recombinant tissue-type plasminogen activator (rt-PA) is used to demonstrate the deglycosylation of 0.1-50 micrograms of a glycoprotein. This method enabled the recovery of a sufficient amount of N-linked oligosaccharides released enzymatically with peptide N-glycosidase F (PNGaseF) from as little as 0.5 microgram rt-PA for subsequent analysis by matrix-assisted laser desorption/ionization time-of-flight (MALDI- TOF) mass spectrometry. The immobilization of rt-PA to the PVDF membrane did not sterically inhibit the PNGaseF-mediated release of oligosaccharides from rt-PA as determined by tryptic mapping experiments. Comparison of the oligosaccharides released from 50 micrograms of rt-PA by either the 96-well plate method or by a standard solution digestion procedure showed no significant differences in the profiles obtained by high-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Both neutral and sialylated oligosaccharide standards spiked into wells were recovered equally as determined by HPAEC-PAD. One advantage of this approach is that reduction and alkylation can be performed on submicrogram amounts of glycoproteins with easy removal of reagents prior to PNGaseF digestion. In addition, this method allows 60 glycoprotein samples to be deglycosylated in 1 day with MALDI-TOF or HPAEC-PAD analysis being performed on the following day.      

Stent implantation through a self-expanding stent

Jailing of a side-branch is a known complication of stent implantation, and makes access to the side-branch difficult, especially if the stent is of the self-expanding type. Although plain balloon angioplasty is feasible for the jailed side-branches, the use of newer devices (a stent, Rotablation or atherectomy) has not been described. We describe a novel way of treating a side-branch jailed by a self-expanding stent by using stent implantation through the strut of a self-expanding stent.