Molecular characterisation of the serine acetyltransferase gene-family from 'Arabidopsis thaliana'

Formation of L-cysteine, from L-serine and sulphide, represents the principal route of Sulphur incorporation into organic compounds in living organisms. Cysteine biosynthesis in plants is achieved by two enzymes, serine acetyltransferase (SAT) and 0-acetylserine (thiol) lyase (OASTL), which form a cysteine synthase complex. Three novel cDNA species, Sat-52, Sat-53 and Sat-106, encoding SAT isoforms from A. thaliana were isolated from a collection of cDNAs previously cloned by functional complementation of the E. coli cysE mutant strain JM15, which is defective in serine acetyltransferase. Deduced amino acid sequence analysis suggests that Sat-52 encodes a putatively mitochondrial isoform whilst Sat-53 and Sat-106 encode proteins with cytoplasmic locations. Sequence information derived from the Arabidopsis Genome Initiative allows mapping of Sat-52, Sat-53 and Sat-106 genes to locations on chromosomes V, I and II respectively. A fourth SAT cDNA from A. thaliana, Sat-1, was cloned prior to the work detailed here and encodes a putatively plastidic isoform of the enzyme. Southern hybridisation against digested genomic DNA suggests that each SAT gene is represented by a single copy in the A. thaliana genome. DNA probes specific to the SAT gene-family members were designed and used in various studies to examine expression of SAT genes. Northern blotting and hybridisation was used to determine transcript distribution between root, leaf, stem, flower and silique tissues and to study the expression of the gene-family in response to sulphate and nitrate nutrition. Spatial distribution of Sat-52 and Sat- 53 transcript in root, leaf and stem tissue was also examined by in situ hybridisation using specific riboprobes. Both genes are highly expressed in leaf trichomes. The Sat-52 transcript was also localised to the vascular- bundles of root, leaf and stem tissue. The isoforms encoded by Sat-52 and Sat-53 are hypothesised to have specific roles in these cell-types

The CGIAR’s Challenge Program Experiences: A Critical Analysis

This document has been prepared by staff of the four Challenge Programs (CPs) established by the CGIAR in 2002-2004 as a contribution to the first meeting of the Consortium Planning Team (CPT) with the Alliance Executive and Deputy Executive (17-20 February 2009)

Computer-Supported Collaborative Production

This paper proposes the concept of collaborative production as a focus of concern within the general area of collaborative work. We position the concept with respect to McGrath's framework for small group dynamics and the more familiar collaboration processes of awareness, coordination, and communication (McGrath 1991). After reviewing research issues and computer-based support for these interacting aspects of collaboration, we turn to a discussion of implications for how to design improved support for collaborative production. We illustrate both the challenges of collaborative production and our design implications with a collaborative map-updating scenario drawn from the work domain of geographical information systems

An End-User Development Perspective on State-of-the-Art Web Development Tools

We reviewed and analyzed nine commercially available web development tools from the perspective of suitability for end-user development to compare and contrast alternative and best-of-breed approaches for particular problem areas within web application development (Getting Started, Workflow, Level of Abstraction, Layout, Database, Application Logic, Testing and Debugging, Learning and Scaling, Security, Collaboration, and Deployment). End-user development involves the creation of dynamic websites with support for features like authentication, conditional display, and searching/sorting by casual web developers who have some experience creating static websites but little or no programming knowledge. We found that current tools do not lack functionality, but rather have a variety of problems in ease of use for end users who are nonprogrammers. In particular, while many tools offer wizards and other features designed to facilitate specific aspects of end-user development, none of the tools that we reviewed supports a holistic approach to web application development. We discuss the implications of these problems and conclude with recommendations for the design of improved web development tools that would lower the entry barrier into web programming

An Interstellar Conduction Front Within a Wolf-Rayet Ring Nebula Observed with the GHRS

With the High Resolution Spectrograph aboard the Hubble Space Telescope we obtained high signal-to-noise (S/N > 200 - 600 per 17 km/s resolution element) spectra of narrow absorption lines toward the Wolf-Rayet star HD 50896. The ring nebula S308 that surrounds this star is thought to be caused by a pressure-driven bubble bounded by circumstellar gas (most likely from a red supergiant or luminous blue variable progenitor) pushed aside by a strong stellar wind. Our observation has shown for the first time that blueshifted (approximately 70 km/s relative to the star) absorption components of C IV and N V arise in a conduction front between the hot interior of the bubble and the cold shell of swept-up material. These lines set limits on models of the conduction front. Nitrogen in the shell appears to be overabundant by a factor ~10. The P Cygni profiles of N V and C IV are variable, possibly due to a suspected binary companion to HD 50896.Comment: 32 pages, Latex, to appear in the Astrophysical Journal, April, 199

Non-invasive MR imaging of inflammation in a patient with both asymptomatic carotid atheroma and an abdominal aortic aneurysm: a case report.

Inflammation is a recognized risk factor for the vulnerable atherosclerotic plaque. USPIO-enhanced MRI imaging is a promising non-invasive method to identify high-risk atheromatous plaque inflammation in vivo in humans, in which areas of focal signal loss on MR images have been shown to correspond to the location of activated macrophages, typically at the shoulder regions of the plaque. This is the first report in humans describing simultaneous USPIO uptake within atheroma in two different arterial territories and again emphasises that atherosclerosis is a truly systemic disease. With further work, USPIO-enhanced MR imaging may be useful in identifying inflamed vulnerable atheromatous plaques in vivo, so refining patient selection for intervention and allowing appropriate early aggressive pharmacotherapy to prevent plaque rupture.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Quasi-Periodic Occultation by a Precessing Accretion Disk and Other Variabilities of SMC X-1

We have investigated the variability of the binary X-ray pulsar, SMC X-1, in data from several X-ray observatories. We confirm the ~60-day cyclic variation of the X-ray flux in the long-term monitoring data from the RXTE and CGRO observatories. X-ray light curves and spectra from the ROSAT, Ginga, and ASCA observatories show that the uneclipsed flux varies by as much as a factor of twenty between a high-flux state when 0.71 second pulses are present and a low-flux state when pulses are absent. In contrast, during eclipses when the X-rays consist of radiation scattered from circumsource matter, the fluxes and spectra in the high and low states are approximately the same. These observations prove that the low state of SMC X-1 is not caused by a reduction in the intrinsic luminosity of the source, or a spectral redistribution thereof, but rather by a quasi-periodic blockage of the line of sight, most likely by a precessing tilted accretion disk. In each of two observations in the midst of low states a brief increase in the X-ray flux and reappearance of 0.71 second pulses occurred near orbital phase 0.2. These brief increases result from an opening of the line of sight to the pulsar that may be caused by wobble in the precessing accretion disk. The records of spin up of the neutron star and decay of the binary orbit are extended during 1991-1996 by pulse-timing analysis of ROSAT, ASCA, and RXTE PCA data. The pulse profiles in various energy ranges from 0.1 to >21 keV are well represented as a combination of a pencil beam and a fan beam. Finally, there is a marked difference between the power spectra of random fluctuations in the high-state data from the RXTE PCA below and above 3.4 keV. Deviation from the fitted power law around 0.06 Hz may be QPO.Comment: Accepted to ApJ. 33 pages including 11 figure

Towards novel difluorinated sugar mimetrics; syntheses and conformational analyses of highly-functionalised difluorinated cyclooctenones

Highly-functionalised difluorinated cyclooctenones were synthesised from trifluoroethanol using either metallated difluoroenol acetal or carbamate chemistry, followed by a [2,3]-Wittig rearrangement or aldol reaction. Efficient RCM reactions afforded the title compounds which showed rather restricted fluxional behaviour by VT 19F NMR. Topological characterisation by molecular modelling and NOESY/ROESY experiments offered a number of challenges, but allowed the identification of two favoured boat-chair conformers which interconverted by pseudorotation with relatively large activation barriers

Co-ordinated expression of amino acid metabolism in response to N and S deficiency during wheat grain filling

Increasing demands for productivity together with environmental concerns about fertilizer use dictate that the future sustainability of agricultural systems will depend on improving fertilizer use efficiency. Characterization of the biological processes responsible for efficient fertilizer use will provide tools for crop improvement under reduced inputs. Transcriptomic and metabolomic approaches were used to study the impact of nitrogen (N) and sulphur (S) deficiency on N and S remobilization from senescing canopy tissues during grain filling in winter wheat (Triticum aestivum). Canopy tissue N was remobilized effectively to the grain after anthesis. S was less readily remobilized. Nuclear magnetic resonance (NMR) metabolite profiling revealed significant effects of suboptimal N or S supply in leaves but not in developing grain. Analysis of amino acid pools in the grain and leaves revealed a strategy whereby amino acid biosynthesis switches to the production of glutamine during grain filling. Glutamine accumulated in the first 7 d of grain development, prior to conversion to other amino acids and protein in the subsequent 21 d. Transcriptome analysis indicated that a down-regulation of the terminal steps in many amino acid biosynthetic pathways occurs to control pools of amino acids during leaf senescence. Grain N and S contents increased in parallel after anthesis and were not significantly affected by S deficiency, despite a suboptimal N:S ratio at final harvest. N deficiency resulted in much slower accumulation of grain N and S and lower final concentrations, indicating that vegetative tissue N has a greater control of the timing and extent of nutrient remobilization than S