Isolation and Characterization of Novel BTB Domain Protein Encoding Genes from Fungal Grass Endophytes

Pasture grasses belonging to the Pooideae sub-family of the Poaceae family frequently host symbiotic fungal endophytes. These include the sexual Epichloë species and the anamorphic asexual Neotyphodium species, which are thought to have evolved from Epichloë species either by the direct loss of sexual reproduction or by interspecific hybridisation. The two key temperate pasture grasses, tall fescue (Festuca arundinacea Schreb) and perennial ryegrass (Lolium perenne L.) interact with the fungal endophytes N. coenophialum and N. lolii, respectively. Large insert genomic DNA libraries are valuable resources for the discovery and isolation of genes and their regulatory sequences, for physical mapping, map-based cloning of target genes as well as for whole genome sequencing. BTB (Bric-a-brac, tram-track, broad complex) domains are highly conserved motifs of 120 amino acids in length. The domains are rich in hydrophobic amino acids, and mediate protein-protein interaction that lead to homomeric dimerisation and in some cases heteromeric dimerisation of a large number of functionally diverse proteins. The presence of BTB domains defines a large family of genes involved in various biological processes, such as the regulation of transcription, DNA binding activity and structural organisation of macromolecular structures. Genes encoding BTB domain proteins (BDP) have previously been described in viruses, yeasts, plants, nematodes, insects, fish and mammals. However, BDP genes have not as yet been described for filamentous fungi

Endophyte ASTRA: a Web-Based Resource for Neotyphodium and Epichloë EST Analysis

Large-scale gene discovery has led to the production of 13,964 expressed sequence tags (ESTs) collectively from the grass endophytes Neotyphodium coenophialum, N. lolii and Epichloë festucae

Hallmark of quantum skipping in energy filtered lensless scanning electron microscopy

We simulate the electronic system of ejected electrons arising when a tip, positioned few 10 amp; 8201;nm away from a surface, is operated in the field emission regime. We find that, by repeated quantum reflections quantum skipping , electrons produced at the nanoscale primary site are able to reach the macroscopic environment surrounding the tip surface region. We observe the hallmark of quantum skipping in an energy filtered experiment that detects the spin of the ejected electron

Influence of Heat Treatment on Defect Structures in Single-Crystalline Blade Roots Studied by X-ray Topography and Positron Annihilation Lifetime Spectroscopy

Single-crystalline superalloy CMSX-4 is studied in the as-cast state and after heat treatment, with material being taken from turbine blade castings. The effect of the heat treatment on the defect structure of the root area near the selector/root connection is emphasized. Multiscale analysis is performed to correlate results obtained by X-ray topography and positron annihilation lifetime spectroscopy (PALS). Electron microscopy observations were also carried out to characterize the inhomogeneity in dendritic structure. The X-ray topography was used to compare defects of the misorientation nature, occurring in as-cast and treated states. The type and concentration of defects before and after heat treatment in different root areas were determined using the PALS method, which enables voids, mono-vacancies, and dislocations to be taken into account. In this way, differences in the concentration of defects caused by heat treatment are rationalized

Subcellular concentrations of sugar alcohols and sugars in relation to phloem translocation in Plantago major, Plantago maritima, Prunus persica, and Apium graveolens

Sugar and sugar alcohol concentrations were analyzed in subcellular compartments of mesophyll cells, in the apoplast, and in the phloem sap of leaves of Plantago major (common plantain), Plantago maritima (sea plantain), Prunus persica (peach) and Apium graveolens (celery). In addition to sucrose, common plantain, sea plantain, and peach also translocated substantial amounts of sorbitol, whereas celery translocated mannitol as well. Sucrose was always present in vacuole and cytosol of mesophyll cells, whereas sorbitol and mannitol were found in vacuole, stroma, and cytosol in all cases except for sea plantain. The concentration of sorbitol, mannitol and sucrose in phloem sap was 2- to 40-fold higher than that in the cytosol of mesophyll cells. Apoplastic carbohydrate concentrations in all species tested were in the low millimolar range versus high millimolar concentrations in symplastic compartments. Therefore, the concentration ratios between the apoplast and the phloem were very strong, ranging between 20- to 100-fold for sorbitol and mannitol, and between 200- and 2000-fold for sucrose. The woody species, peach, showed the smallest concentration ratios between the cytosol of mesophyll cells and the phloem as well as between the apoplast and the phloem, suggesting a mixture of apoplastic and symplastic phloem loading, in contrast to the herbal plant species (common plantain, sea plantain, celery) which likely exhibit an active loading mode for sorbitol and mannitol as well as sucrose from the apoplast into the phloem

Rad51 Polymerization Reveals a New Chromatin Remodeling Mechanism

Rad51 protein is a well known protagonist of homologous recombination in eukaryotic cells. Rad51 polymerization on single-stranded DNA and its role in presynaptic filament formation have been extensively documented. Rad51 polymerizes also on double-stranded DNA but the significance of this filament formation remains unclear. We explored the behavior of Saccharomyces cerevisiae Rad51 on dsDNA and the influence of nucleosomes on Rad51 polymerization mechanism to investigate its putative role in chromatin accessibility to recombination machinery. We combined biochemical approaches, transmission electron microscopy (TEM) and atomic force microscopy (AFM) for analysis of the effects of the Rad51 filament on chromatinized templates. Quantitative analyses clearly demonstrated the occurrence of chromatin remodeling during nucleoprotein filament formation. During Rad51 polymerization, recombinase proteins moved all the nucleosomal arrays in front of the progressing filament. This polymerization process had a powerful remodeling effect, as Rad51 destabilized the nucleosomes along considerable stretches of DNA. Similar behavior was observed with RecA. Thus, recombinase polymerization is a powerful mechanism of chromatin remodeling. These remarkable features open up new possibilities for understanding DNA recombination and reveal new types of ATP-dependent chromatin dynamics

THE RATE OF DECOMPOSITION OF NITROGEN PENTOXIDE AT MODERATELY LOW PRESSURE

Introduction. - At moderately high pressures, the decomposition of gaseous nitrogen pentoxide was shown by the original work of Daniels and Johnston [1] to be homogeneous and of the first order and this has been completely confirmed by the work of subsequent investigators [2]. At low pressures, however, there has been a striking lack of agreement as to the rate of decomposition of this substance. Hirst and Rideal [3], Hibben [4], and Loomis and Smith [5] have all tried to follow the rate of the decomposition at low pressures by freezing out the nitrogen oxides during the course of the reaction and measuring the pressure of the oxygen which had been formed. Working at initial pressures in the range 0.035-1.450 mm. of mercury Hirst and Rideal report that the specific rate of decomposition becomes greater at low pressures, the increase in rate being appreciable at 0.25 mm. and several fold at their lowest pressures. Hibben, on the other hand, working in the pressure range 0.03 to 0.18 mm. finds throughout the same specific rate of decomposition as at high pressures. Loomis and Smith, however, conclude that the method used in all three sets of experiments is unreliable, since, in the first place, they find that appreciable amounts of oxygen can be occluded and carried down with the condensed oxides of nitrogen, and in the second place, find that nitrogen pentoxide is appreciably adsorbed on the surface of pyrex glass. More recently Sprenger [6] has attempted to follow the rate of decomposition by pressure measurements made with a quartz fibre gauge. Working in the range 0.01 to 0.05 mm. pressure, he comes to the extraordinary conclusion that the nitrogen pentoxide decomposes at approximately its high-pressure rate when it is first introduced into the reaction flask, and later, with a considerable fraction of the original nitrogen pentoxide still remaining, it ceases to decompose at all. Finally, Rice, Urey and Washburne [7] report that preliminary measure ments made by Miss E. Wilson show that the specific rate of decomposition of nitrogen pentoxide falls below the high-pressure rate even at pressures of several millimeters. Since the low-pressure rate of homogeneous gas reactions is of great theoretical interest, especially in connection with the theory of activation by collision as developed by Rice and Ramsperger [8] and by Kassel [9], further work on the low-pressure rate of decomposition of nitrogen pentoxide seems desirable in view of the almost complete lack of agreement in the results described above