Expression of catalytic mutants of the mtDNA helicase Twinkle and polymerase POLG causes distinct replication stalling phenotypes.

The mechanism of mitochondrial DNA replication is a subject of intense debate. One model proposes a strand-asynchronous replication in which both strands of the circular genome are replicated semi-independently while the other model proposes both a bidirectional coupled leading- and lagging-strand synthesis mode and a unidirectional mode in which the lagging-strand is initially laid-down as RNA by an unknown mechanism (RITOLS mode). Both the strand-asynchronous and RITOLS model have in common a delayed synthesis of the DNA-lagging strand. Mitochondrial DNA is replicated by a limited set of proteins including DNA polymerase gamma (POLG) and the helicase Twinkle. Here, we report the effects of expression of various catalytically deficient mutants of POLG1 and Twinkle in human cell culture. Both groups of mutants reduced mitochondrial DNA copy number by severe replication stalling. However, the analysis showed that while induction of POLG1 mutants still displayed delayed lagging-strand synthesis, Twinkle-induced stalling resulted in maturated, essentially fully double-stranded DNA intermediates. In the latter case, limited inhibition of POLG with dideoxycytidine restored the delay between leading- and lagging-strand synthesis. The observed cause-effect relationship suggests that Twinkle-induced stalling increases lagging-strand initiation events and/or maturation mimicking conventional strand-coupled replication

Evaluation of the impact of weather variability on a Net Zero Energy Building: advantage of sensitivity analysis for performance guarantee

Global sensitivity analysis associated with uncertainty analysis evaluates the robustness of a physical system and prioritises measurement and/or modelling efforts. The uncertainty analysis evaluates a confidence interval, whereas the sensitivity analysis quantifies the accountability of each uncertain input on the dispersion of the output. These statistical methods are usually used to account for the variability of the static inputs, which are constant regarding the evolution of the system, for example the physical properties of the materials modelled. Dynamic inputs however, i.e. parameters that are variable over time, are rarely taken into account in the statistical analyses because of the difficulty managing correlations between the inputs in stochastic methods. Yet, the system’s boundary conditions, such as meteorological input, are decisive for the evaluation of the behaviour of the building system. This paper aims at quantifying the influence of six meteorological variables as well as 39 static inputs on the dynamic thermal behaviour of a net zero energy building. To do so, a method that stochastically generates consistent meteorological data is used and is adapted to the purpose of global sensitivity analysis. The results show a high dispersion of the cooling requirements, for which the direct solar radiation, the albedo and the window solar factor can be held accountable. Thus the variability of solar resources and their interaction with the building have the greatest impact on the performance of the building. The variability of meteorological data needs to be considered to evaluate confidence intervals on energy performance. Furthermore, the impact of static parameters should not be overlooked, because their influence may remain significant. The considerable influence of the albedo and solar factor on the results of the present case study also shed light on the importance of assessing its value on site

Projet Référentiel Plancton de la Baie de Calvi : II. Diversité de l’écosystème planctonique de la Baie de Calvi

Ce rapport présente la diversité de l’écosystème planctonique de la Baie de Calvi. Le premier chapitre rappelle les principales définitions utilisées en écologie planctonique. La suite du texte présente les grands groupes planctoniques rencontrés en Baie de Calvi, leurs principales caractéristiques morphologiques et les grandes lignes de leur écologie. Le texte est illustré de photographies originales de microphytoplancton et de zooplancton de la Baie réalisées à STARESO par les auteurs

Hydrodynamical and ecosystem processes in ice-covered seas of the Southern and Northern Hemispheres

peer reviewedPreface of the 30th International Liège Colloquium on Ocean Hydrodynamics Liège, Belgium (May 4–8 1998) : Hydrodynamical and ecosystem processes in ice-covered seas of the Southern and Northern Hemispheres. Issue of JMS edited by Anne Goffart and Jean-Henri Hecq

Perspectives d'amélioration du conseil prévisionnel de fertilisation azotée à la parcelle en Wallonie par l'utilisation du logiciel AzoFert®

Prospects for improving the provisional nitrogen fertilization recommendation at field scale in Wallonia using the AzoFert® software. The French software AzoFert® for nitrogen fertilization recommendation is currently under adaptation and validation for soil and climatic conditions in Wallonia by the CRA-W within the INTERREG IV project "SUN" (Sustainable Use of Nitrogen). This adaptation has raised the need for a change of values in the parameter tables and catalogs relating to meadow residues, crop residues, catch crop practices, crops, organic amendments and soil type. Data from 25 trials of increasing nitrogen fertilizer rates conducted by CRA-W between 1996 and 2011 in cereal, potato and vegetable crops located on loam and sandy loam soil were used to validate the AzoFert® software adapted for Wallonia. The difference between nitrogen rates recommended on the one hand by AzoFert® or Azobil® (software currently used in the reference lab for Nitrate [Requasud] at CRA-W) and the optimal dose of nitrogen fertilizer assessed in each trial on the other hand shows that, in most cases, AzoFert® gives a recommendation closer to the optimum than Azobil®. The nitrogen uptake measured in the plants collected in the unfertilized control plot also shows a higher correlation with nitrogen supply from the soil assessed by AzoFert® than for plants assessed by Azobil®. The more accurate estimate of the mineralization of organic sources, probably linked to the dynamic soil nitrogen supply approach integrated into AzoFert®, may explain the gain in the greater accuracy of the AzoFert® recommendation in comparison with that of Azobil®

Les cultures intermédiaires pièges à nitrate (CIPAN) et engrais verts : protection de l'environnement et intérêt agronomique

Autumn cover crops and green manures: environment protection and agronomic interest. Due to the evolution of the environmental policy, practice of green manure cropping has been replaced by autumn cover crops in order to take up nitrate residues of the soil. These crops (mustard, phacelia, rye-grass, rye) show a high ability to take up N (sometimes more than 100 kg N.ha-1), leading to a decreasing threat for nitrate leaching. Such an ability is however related to species, but also to cropping practices mainly sowing date. Subsequent mineralization (measured with labeling 15N technic) of this organic-green manure-N, influenced by physical and chemical characteristics of the ploughed biomass, seems however limited (less than 45% of N ploughed in the soil) and does not lead obviously to a reduction of the N advice for the following crop. Nevertheless, stocking of organic N and C in the soil is expected to have a beneficial long-term effect on both mineralization (providing more N) and soil humus content leading to improve structural properties of soil