The <Emphasis Type=Italic>Dunaliella salina</Emphasis> organelle genomes: large sequences,inflated with intronic and intergenic DNA

Background  

Dunaliella salina Teodoresco, a unicellular, halophilic green alga belonging to the Chlorophyceae, is among the most industrially important microalgae. This is because D. salina can produce massive amounts of β-carotene, which can be collected for commercial purposes, and because of its potential as a feedstock for biofuels production. Although the biochemistry and physiology of D. salina have been studied in great detail, virtually nothing is known about the genomes it carries, especially those within its mitochondrion and plastid. This study presents the complete mitochondrial and plastid genome sequences of D. salina and compares them with those of the model green algae Chlamydomonas reinhardtii and Volvox carteri.     

Cell adhesion to fibrillin-1 molecules and microfibrils is mediated by alpha 5 beta 1 and alpha v beta 3 integrins

Fibrillins are the major glycoprotein components of microfibrils that form a template for tropoelastin during elastic fibrillogenesis. We have examined cell adhesion to assembled purified microfibrils, and its molecular basis. Human dermal fibroblasts exhibited Arg-Gly-Asp and cation-dependent adhesion to microfibrils and recombinant fibrillin-1 protein fragments. Strong integrin alpha 5 beta 1 interactions with fibrillin ligands were identified, but integrin alpha v beta 3 also contributed to cell adhesion. Fluorescence-activated cell sorting analysis confirmed the presence of abundant alpha 5 beta 1 and some alpha v beta 3 receptors on these cells. Adhesion to microfibrils and to Arg-Gly-Asp containing fibrillin-1 protein fragments induced signaling events that led to cell spreading, altered cytoskeletal organization, and enhanced extracellular fibrillin-1 deposition. Differences in cell shape when plated on fibrillin or fibronectin implied substrate-specific alpha 5 beta 1-mediated cellular responses. An Arg-Gly-Asp-independent cell adhesion sequence was also identified within fibrillin-1. Adhesion and spreading of smooth muscle cells on fibrillin ligands was enhanced by antibody-induced beta1 integrin activation. A375-SM melanoma cells bound Arg-Gly-Asp-containing fibrillin-1 protein fragments mainly through alpha v beta 3, whereas HT1080 cells used mainly alpha 5 beta 1. This study has shown that fibrillin microfibrils mediate cell adhesion, that alpha 5 beta 1 and alpha v beta 3 are both important but cell-specific fibrillin-1 receptors, and that cellular interactions with fibrillin-1 influence cell behavior.     

Effect of pre-exhaustion exercise on lower-extremity muscle activation during a leg press exercise

The purpose of this study was to investigate the effect of pre-exhaustion exercise on lower-extremity muscle activation during a leg press exercise. Pre-exhaustion exercise, a technique frequently used by weight trainers, involves combining a single-joint exercise immediately followed by a related multijoint exercise (e.g., a knee extension exercise followed by a leg press exercise). Seventeen healthy male subjects performed 1 set of a leg press exercise with and without pre-exhaustion exercise, which consisted of 1 set of a knee extension exercise. Both exercises were performed at a load of 10 repetitions maximum (10 RM). Electromyography (EMG) was recorded from the rectus femoris, vastus lateralis, and gluteus maximus muscles simultaneously during the leg press exercise. The number of repetitions of the leg press exercise performed by subjects with and without pre-exhaustion exercise was also documented. The activation of the rectus femoris and the vastus lateralis muscles during the leg press exercise was significantly less when subjects were pre-exhausted (p < 0.05). No significant EMG change was observed for the gluteus maximus muscle. When in a pre-exhausted state, subjects performed significantly (p < 0.001) less repetitions of the leg press exercise. Our findings do not support the popular belief of weight trainers that performing pre-exhaustion exercise is more effective in order to enhance muscle activity compared with regular weight training. Conversely, pre-exhaustion exercise may have disadvantageous effects on performance, such as decreased muscle activity and reduction in strength, during multijoint exercise.     

Bioactive lipopeptides of ice-nucleating snow bacterium Pseudomonas syringae strain 31R1

The production of secondary metabolite lipopeptides by ice-nucleating Pseudomonas syringae strain 31R1 was investigated. Pseudomonas syringae strain 31R1 is a rifampicin-resistant derivative of P. syringae no. 31 used for the commercial production of snow. It is shown that P. syringae strain 31R1 produces antifungal lipodepsipeptides, syringomycins E and G, and, in addition, a novel and unique lipopeptide, peptin31. Spectroscopic and spectrometric analyses revealed that peptin31 is a linear undecalipopeptide with sequence identities to N- and C-terminal portions but lacking 11 amino acids of known lipodepsipeptide syringopeptin SPPhv. Peptin31 displayed antifungal activities against Rhodotorula pilimanae, Rhizoctonia solani, and Trichoderma harzianum and also hemolytic and antibacterial activities. Extracts of P. syringae strain 31R1 grown in medium with chloride were fungicidal, but not when grown without chloride. The latter extracts lacked peptin 31 and contained des-chloro forms of syringomycins E and G with low antifungal activities. Thus, the three lipopeptides account for the fungicidal properties of P. syringae 31R1 extracts. The occurrence of these bioactive metabolites should be considered when P. syringae no. 31 and its derivatives are used in products for making artificial snow.     

Manipulation of trait expression and pollination regime reveals the adaptive significance of spur length

Understanding the mechanisms of adaptive population differentiation requires that both the functional and adaptive significance of divergent traits are characterized in contrasting environments. Here, we (a) determined the effects of floral spur length on pollen removal and receipt using plants with artificial spurs representing the species-wide variation in length, and (b) quantified pollinator-mediated selection on spur length and three traits contributing to floral display in two populations each of the short-spurred and the long-spurred ecotype of the orchid Platanthera bifolia. Both pollen receipt and removal reached a maximum at 28–29 mm long spurs in a short-spurred population visited by short-tongued moths. In contrast, pollen receipt increased linearly across the tested range (4–52 mm) and pollen removal was unrelated to spur length in a long-spurred population predominantly visited by a long-tongued moth. The experimentally documented effects on pollen transfer were not reflected in pollinator-mediated selection through female fitness or pollen removal indicating that the natural within-population variation in spur length was insufficient to result in detectable variation in pollen limitation. Our study illustrates how combining trait manipulation with analysis of causes and strength of phenotypic selection can illuminate the functional and adaptive significance of trait expression when trait variation is limited.     

Stereoelectronic properties of metalloenzymes. 10. a refined model that mimics the type II copper(II) site in galactose oxidase2

A number of copper(II) complexes of tridentate ligands with various donor atoms have been studied in an attempt to duplicate the unusual reactivity patterns and accompanying spectral changes of the copper(II) center in galactose oxidase. Results indicate that in order to match the optical and electron spin resonance spectral change observed upon CN^? binding by the enzyme, an equatorial, negative ligand must be displaced in a small molecule model. The crystal and molecular structure of the best model complex was solved by a single crystal X-ray diffraction study. The compound, monoacetato-1,3-bis(2-(4-methyl-pyridyl)imino)isoindolatocopper(II), crystallizes in the centro-symmetric triclinic space group Pī with a = 7.392(3) Å, b = 13.782(5) Å, c = 23.422(12) Å, α = 92.08(3)°, β = 104.11(5)°, γ = 109.98(4)°, V = 2156(1) ų, d(obsd.)(calc.)=(1.43)(1.44) g/cm^?3 for mol wt of 466.7 and Z = 4. Diffraction data were collected with a Syntex Pl diffractometer using graphite-monochromatized Cu radiation (λ = 1.5418 Å). The copper atoms were located from a Patterson synthesis; all other nonhydrogen atoms were located via difference. Fourier techniques, and hydrogen atoms were placed in calculated positions. Final refinement resulted in discrepancy indices of R = 0.089 and “Goodness to Fit” = 3.68 for all 3608 reflections having (I) ? 3σ(I) (5°<2θ<100°). There are two unique molecules in the asymmetric unit that are monomeric and well separated. The geometry around the copper atom is approximately square pyramidal, with the coordination sphere derived from three nitrogens of the tridentate ligand, one oxygen from the acetate unit, and an oxygen atom of a water molecule occupying an axial position. The structure is surprising both in that an axial water molecule is present and that the remaining four ligand atoms to the copper atom are rather distorted from a planar configuration. The plane defined by the copper, N5, and N3 atoms intersects the plane defined by the copper, Nl, and Ol, atoms forming a “twist angle” of 25.0° (0.0° would be ideal for a planar inner coordination sphere). The stereoelectronics of the inner coordination spheres of the type II Cu(II) enzymes galactose oxidase and superoxide dismutase are discussed and appropriate comparisons are made with emphasis on the origin of spectral changes observed upon anion binding.     

Structural homology between elongation factors EF-Tu from Bacillus stearothermophilus and Escherichia coli in the binding site for aminoacyl-tRNA

Elongation factor EF-Tu (Mr approximately equal to 50 000) and elongation factor EF-G (Mr approximately equal to 78 000) were isolated from Bacillus stearothermophilus in a homogeneous form. The ability of EF-Tu to participate in protein synthesis is rapidly inactivated by N-tosyl-L-phenyl-alanylchloromethane (Tos-PheCH2Cl). EF-Tu X GTP is more susceptible to the inhibition by Tos-PheCH2Cl than is EF-Tu X GDP. Tos-PheCH2Cl forms a covalent equimolar complex with the factor by reacting with a cysteine residue in its molecule. The labelling of EF-Tu by the reagent irreversibly destroys its ability to bind aminoacyl-tRNA, which in turn protects the protein from this inactivation. This indicates that the modification of EF-Tu by Tos-PheCH2Cl occurs at the aminoacyl-tRNA binding site of the protein. To identify and characterize the site of aminoacyl-tRNA binding in EF-Tu, the factor was labelled with [14C]Tos-PheCH2Cl, digested with trypsin, the resulting peptides were separated by high-performance liquid chromatography and the sequence of the radioactive peptide was determined. The peptide has identical structure with an Escherichia coli EF-Tu tryptic peptide comprising the residues 75-89 and the Tos-PheCH2Cl-reactive cysteine at position 81 [Jonák, J., Petersen, T. E., Clark, B. F. C. and Rychlík, I. (1982) FEBS Lett. 150, 485-488]. Experiments on photo-oxidation of EF-Tu by visible light in the presence of rose bengal dye showed that there are apparently two histidine residues in elongation factor Tu from B. stearothermophilus which are essential for the interaction with aminoacyl-tRNA. This is clearly reminiscent of a similar situation in E. coli EF-Tu [Jonák, J., Petersen, T. E., Meloun, B. and Rychlík, I. (1984) Eur. J. Biochem. 144, 295-303]. Our results provide further evidence for the conserved nature of the site of aminoacyl-tRNA binding in elongation factor EF-Tu and show that Tos-PheCH2Cl reagent might be a favourable tool for the identification of the site in the structure of prokaryotic EF-Tus.     

The invertebrate fauna of a physically modified urban river

The typical urban river is affected by various factors relating to water quality problems, physical habitat modification (for flood prevention) and flashy flows. These restrict macroinvertebrate biodiversity such that a few tolerant taxa may dominate and more sensitive organisms may be completely absent. This paper presents the findings of a year long, macroinvertebrate survey of an urban river catchment and investigates the effects of physical habitat modification on macroinvertebrates using various analytical tools. It is demonstrated that considerable variation in invertebrate species, abundance, diversity and tolerance exists between different urban rivers, sites on the same river and individual sites at different sampling times. Analysis of paired sites with similar water quality, but contrasting physical habitat, indicates that less modified sites support a slightly higher quality macroinvertebrate fauna (defined by biotic score and beta diversity) than heavily engineered sites. It is concluded that water quality is the primary limiting factor of invertebrate biodiversity in the heavily urbanized River Tame catchment. The removal of heavy engineering structures may facilitate improvements to invertebrate fauna in urban rivers only in conjunction with improvements to water quality.     

Entoloma subgen. Pouzaromyces (Basidiomycetes, Agaricales) in Norway

Six taxa, representing five species of Entoloma (Fr.) Kumm. subgen. Pouzaromyces (Pilat) Moser emend. Noordel. are described from Norway, of which four are new to the country, viz., E. dysthales (Peck) Sacc, E. dysthaloides Noordel., E. araneosum (Quel.) Moser i.fulvostrigosum (Berk. & Br.) Noordel., and E. versatilis (Fr.) Moser.     

PLUNC: a multifunctional surfactant of the airways

PLUNC (palate, lung and nasal epithelium clone) protein is an abundant secretory product of epithelia throughout the mammalian conducting airways. Despite its homology with the innate immune defence molecules BPI (bactericidal/permeability-increasing protein) and LBP (lipopolysaccharide-binding protein), it has been difficult to define the functions of PLUNC. Based on its marked hydrophobicity and expression pattern, we hypothesized that PLUNC is an airway surfactant. We found that purified recombinant human PLUNC exhibited potent surfactant activity by several different measures, and experiments with airway epithelial cell lines and primary cultures indicate that native PLUNC makes a significant contribution to the overall surface tension in airway epithelial secretions. Interestingly, we also found that physiologically relevant concentrations of PLUNC-inhibited Pseudomonas aeruginosa biofilm formation in vitro without acting directly as a bactericide. This finding suggests that PLUNC protein may inhibit biofilm formation by airway pathogens, perhaps through its dispersant properties. Our data, along with reports from other groups on activity against some airway pathogens, expand on an emerging picture of PLUNC as a multifunctional protein, which plays a novel role in airway defences at the air/liquid interface.