Cell proliferation, cell shape, and microtubule and cellulose microfibril organization of tobacco BY-2 cells are not altered by exposure to near weightlessness in space

The microtubule cytoskeleton and the cell wall both play key roles in plant cell growth and division, determining the plant’s final stature. At near weightlessness, tubulin polymerizes into microtubules in vitro, but these microtubules do not self-organize in the ordered patterns observed at 1g. Likewise, at near weightlessness cortical microtubules in protoplasts have difficulty organizing into parallel arrays, which are required for proper plant cell elongation. However, intact plants do grow in space and therefore should have a normally functioning microtubule cytoskeleton. Since the main difference between protoplasts and plant cells in a tissue is the presence of a cell wall, we studied single, but walled, tobacco BY-2 suspension-cultured cells during an 8-day space-flight experiment on board of the Soyuz capsule and the International Space Station during the 12S mission (March–April 2006). We show that the cortical microtubule density, ordering and orientation in isolated walled plant cells are unaffected by near weightlessness, as are the orientation of the cellulose microfibrils, cell proliferation, and cell shape. Likely, tissue organization is not essential for the organization of these structures in space. When combined with the fact that many recovering protoplasts have an aberrant cortical microtubule cytoskeleton, the results suggest a role for the cell wall, or its production machinery, in structuring the microtubule cytoskeleto

Identifying core features of adaptive metabolic mechanisms for chronic heat stress attenuation contributing to systems robustness

The contribution of metabolism to heat stress may play a significant role in defining robustness and recovery of systems; either by providing the energy and metabolites required for cellular homeostasis, or through the generation of protective osmolytes. However, the mechanisms by which heat stress attenuation could be adapted through metabolic processes as a stabilizing strategy against thermal stress are still largely unclear. We address this issue through metabolomic and transcriptomic profiles for populations along a thermal cline where two seagrass species, Zostera marina and Zostera noltii, were found in close proximity. Significant changes captured by these profile comparisons could be detected, with a larger response magnitude observed in northern populations to heat stress. Sucrose, fructose, and myo-inositol were identified to be the most responsive of the 29 analyzed organic metabolites. Many key enzymes in the Calvin cycle, glycolysis and pentose phosphate pathways also showed significant differential expression. The reported comparison suggests that adaptive mechanisms are involved through metabolic pathways to dampen the impacts of heat stress, and interactions between the metabolome and proteome should be further investigated in systems biology to understand robust design features against abiotic stress

phot1 inhibition of ABCB19 primes lateral auxin fluxes in the shoot apex required for phototropism

It is well accepted that lateral redistribution of the phytohormone auxin underlies the bending of plant organs towards light. In monocots, photoreception occurs at the shoot tip above the region of differential growth. Despite more than a century of research, it is still unresolved how light regulates auxin distribution and where this occurs in dicots. Here, we establish a system in Arabidopsis thaliana to study hypocotyl phototropism in the absence of developmental events associated with seedling photomorphogenesis. We show that auxin redistribution to the epidermal sites of action occurs at and above the hypocotyl apex, not at the elongation zone. Within this region, we identify the auxin efflux transporter ATP-BINDING CASSETTE B19 (ABCB19) as a substrate target for the photoreceptor kinase PHOTOTROPIN 1 (phot1). Heterologous expression and physiological analyses indicate that phosphorylation of ABCB19 by phot1 inhibits its efflux activity, thereby increasing auxin levels in and above the hypocotyl apex to halt vertical growth and prime lateral fluxes that are subsequently channeled to the elongation zone by PIN-FORMED 3 (PIN3). Together, these results provide new insights into the roles of ABCB19 and PIN3 in establishing phototropic curvatures and demonstrate that the proximity of light perception and differential phototropic growth is conserved in angiosperm

A taxonomy of errors for information systems

We provide a full characterization of computational error states for information systems. The class of errors considered is general enough to include human rational processes, logical reasoning, scientific progress and data processing in some functional programming languages. The aim is to reach a full taxonomy of error states by analysing the recovery and processing of data. We conclude by presenting machine-readable checking and resolve algorithms

Propagation and termination steps in Rh-mediated carbene polymerisation using diazomethane

Rh-mediated carbene (co)polymerisation of diazomethane works best in the presence of Rh-III catalyst precursors, the use of which leads to a significant increase in polymer yield and molecular weight. Chain termination via beta-hydride elimination is severely suppressed for these species, although this process does still occur leading to unsaturated chain ends. Subsequent chain walking leading to the formation of branched polymers seems not to occur. Computational studies describing pathways for both chain propagation and chain termination using a (cycloocta-2,5-dien-1-yl)Rh-III(alkyl) species as a representative model for the active species revealed that chain propagation is favoured for these species, although beta-hydride elimination is still viable at the applied reaction temperatures. The computational studies are in excellent agreement with all experimental results, and further reveal that chain propagation via carbene insertion (leading to linear poly-methylene) occurs with a much lower energy barrier than insertion of 1-alkenes into either the Rh-H bond after beta-hydride elimination or into the Rh-C bond of the growing polymer chain (leading to branched polymers). These energetic differences conveniently explain why experimentally the formation of branches is not observed in (co) polymerisation reactions employing diazomethane. The formation of substantial amounts of low-M-w oligomers and dimers in the experimental reactions can be ascribed to the presence of (1,5-cyclooctadiene)Rh-I species in the reaction mixture, for which chain termination via beta-hydride elimination is clearly favoured over chain propagation. These two species stem from a non-selective catalyst activation process during which the catalyst precursors are in situ activated towards carbene polymerisation, and as such the results in this paper might contribute to further improvements of this reaction

On malfunctioning software

Artefacts do not always do what they are supposed to, due to a variety of reasons, including manufacturing problems, poor maintenance, and normal wear-and-tear. Since software is an artefact, it should be subject to malfunctioning in the same sense in which other artefacts can malfunction. Yet, whether software is on a par with other artefacts when it comes to malfunctioning crucially depends on the abstraction used in the analysis. We distinguish between “negative” and “positive” notions of malfunction. A negative malfunction, or dysfunction, occurs when an artefact token either does not (sometimes) or cannot (ever) do what it is supposed to. A positive malfunction, or misfunction, occurs when an artefact token may do what is supposed to but, at least occasionally, it also yields some unintended and undesirable effects. We argue that software, understood as type, may misfunction in some limited sense, but cannot dysfunction. Accordingly, one should distinguish software from other technical artefacts, in view of their design that makes dysfunction impossible for the former, while possible for the latter

THE IMPACT OF DIETARY PROTEIN OR AMINO ACID SUPPLEMENTATION ON MUSCLE MASS AND STRENGTH IN ELDERLY PEOPLE: INDIVIDUAL PARTICIPANT DATA AND META-ANALYSIS OF RCT’S

Objectives Increasing protein or amino acid intake has been promoted as a promising strategy to increase muscle mass and strength in elderly people, however, long-term intervention studies show inconsistent findings. Therefore, we aim to determine the impact of protein or amino acid supplementation compared to placebo on muscle mass and strength in older adults by combining the results from published trials in a metaanalysis and pooled individual participant data analysis. Design We searched Medline and Cochrane databases and performed a meta-analysis on eight available trials on the effect of protein or amino acid supplementation on muscle mass and strength in older adults. Furthermore, we pooled individual data of six of these randomized double-blind placebo-controlled trials. The main outcomes were change in lean body mass and change in muscle strength for both the meta-analysis and the pooled analysis. Results The meta-analysis of eight studies (n=557) showed no significant positive effects of protein or amino acid supplementation on lean body mass (mean difference: 0.014 kg: 95% CI -0.152; 0.18), leg press strength (mean difference: 2.26 kg: 95% CI -0.56; 5.08), leg extension strength (mean difference: 0.75 kg: 95% CI: -1.96, 3.47) or handgrip strength (mean difference: -0.002 kg: 95% CI -0.182; 0.179). Likewise, the pooled analysis showed no significant difference between protein and placebo treatment on lean body mass (n=412: p=0.78), leg press strength (n=121: p=0.50), leg extension strength (n=121: p=0.16) and handgrip strength (n=318: p=0.37). Conclusions There is currently no evidence to suggest that protein or amino acid supplementation without concomitant nutritional or exercise interventions increases muscle mass or strength in predominantly healthy elderly people