Kinetic transcriptomic approach revealed metabolic pathways and genotoxic-related changes implied in the Arabidopsis response to ionising radiations

Plants exposed to ionising radiation (IR) have to face direct and indirect (oxidative stress) deleterious effects whose intensity depends on the dose applied and led to differential genome regulation. Transcriptomic analyses were conducted with CATMA microarray technology on Arabidopsis thaliana plantlets, 2 and 26 h after exposure to the IR doses 10 Gy and 40 Gy. 10 Gy treatment seemed to enhance antioxidative compound biosynthetic pathways whereas the 40 Gy dose up-regulated ROS-scavenging enzyme genes. Transcriptomic data also highlighted a differential regulation of chloroplast constituent genes depending on the IR dose, 10 Gy stimulating and 40 Gy down-regulating. This probable 40 Gy decrease of photosynthesis could help for the limitation of ROS production and may be coupled with programmed cell death (PCD)/senescence phenomena. Comparisons with previous transcriptomic studies on plants exposed to a 100 Gy dose revealed 60 dose-dependent up-regulated genes, including notably cell cycle checkpoints to allow DNA repairing phenomena. Furthermore, the alteration of some cellular structure related gene expression corroborated a probable mitotic arrest after 40 Gy. Finally, numerous heat-shock protein and chaperonin genes, known to protect proteins against stress-dependent dysfunction, were up-regulated after IR exposure

On Embeddability of Buses in Point Sets

Set membership of points in the plane can be visualized by connecting corresponding points via graphical features, like paths, trees, polygons, ellipses. In this paper we study the \emph{bus embeddability problem} (BEP): given a set of colored points we ask whether there exists a planar realization with one horizontal straight-line segment per color, called bus, such that all points with the same color are connected with vertical line segments to their bus. We present an ILP and an FPT algorithm for the general problem. For restricted versions of this problem, such as when the relative order of buses is predefined, or when a bus must be placed above all its points, we provide efficient algorithms. We show that another restricted version of the problem can be solved using 2-stack pushall sorting. On the negative side we prove the NP-completeness of a special case of BEP.Comment: 19 pages, 9 figures, conference version at GD 201

Carbon Dynamics, Development and Stress Responses in Arabidopsis: Involvement of the APL4 Subunit of ADP-Glucose Pyrophosphorylase (Starch Synthesis)

An Arabidopsis thaliana T-DNA insertional mutant was identified and characterized for enhanced tolerance to the singlet-oxygen-generating herbicide atrazine in comparison to wild-type. This enhanced atrazine tolerance mutant was shown to be affected in the promoter structure and in the regulation of expression of the APL4 isoform of ADP-glucose pyrophosphorylase, a key enzyme of the starch biosynthesis pathway, thus resulting in decrease of APL4 mRNA levels. The impact of this regulatory mutation was confirmed by the analysis of an independent T-DNA insertional mutant also affected in the promoter of the APL4 gene. The resulting tissue-specific modifications of carbon partitioning in plantlets and the effects on plantlet growth and stress tolerance point out to specific and non-redundant roles of APL4 in root carbon dynamics, shoot-root relationships and sink regulations of photosynthesis. Given the effects of exogenous sugar treatments and of endogenous sugar levels on atrazine tolerance in wild-type Arabidopsis plantlets, atrazine tolerance of this apl4 mutant is discussed in terms of perception of carbon status and of investment of sugar allocation in xenobiotic and oxidative stress responses

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Proteomics to unravel mechanisms of nanoparticle toxicity

International audienc

Proteomics to unravel mechanisms of nanoparticle toxicity

International audienc

Colloidal and chemical stability of iron oxides nanoparticles in aqueous solution

International audienceEither used as nano-carriers in blood, depolluting agents in groundwaters or in soils, engineered iron nanoparticles are prone to a growing interest that explains their multiple uses as well as their increasing industrial production. The very small size of iron oxide nanoparticles (IONPs) having at least one space dimension <100nm gives rise to some exceptional physicochemical properties that ensue from their high reactivity. In environmental and agricultural fields, where IONPs could be particularly used, this reactivity is directly related to their colloidal stability which is of prime interest regarding groundwater- or soil-remediation, allowing IONPs to reach their target. NPs stability in aqueous environments depends on many parameters including the environmental conditions (pH, temperature, soil solution chemistry and ionic strength), NPs concentration, as well as NPs intrinsic and surficial characteristics. In this context, experimentations were investigated to assess the effects of pH, surface modifications and NPs intrinsic physicochemical properties (size, morphology and surface area (SA)) on their colloidal and chemical stability.In a primary step, nm-sized Fe3O4-NPs and ɣ-Fe2O3-NPs were synthesized and their surface were then coated with HA and PC (Phosphatidylcholines) to model natural surface modification. In a second step, these IONPS were characterized with TEM, XRD, FT-IR and BET. Fe(II)/Fe(III) ratio measurements have been conducted on Fe3O4-NPs in aerobic conditions to assess the oxidation kinetics of magnetite to maghemite. Then, the effect of pH on the colloidal stability of these bare-IONPs and surface modified Fe3O4-NPs was studied in a pH range from 3 to 7.5. The results evidenced that pH played a key role in driving IONPs colloidal stability as pH changes affected the size distribution (SD) of all the IONPs investigated, leading at least to two SD configurations: IONPs were either stable or aggregated depending of the closeness of the pH regards to their respective pHzpc. Surface coatings with HA and PC induced surface chemical modifications, which shifted the pHzpc of bare magnetite and modified the ensuing pH-dependent SD through electrosteric interactions. HA turned out to be much more effective than PC in enhancing IONPs colloidal stability as it promoted smaller sized aggregates and widened magnetite pH-stability range (pH=4 to 7.5). The rapid transformation of magnetite into maghemite (five days) resulted in the loss of Fe(II) from its chemical structure and increased magnetite-NPs SA. Maghemite also displayed a higher sensitivity to pH than magnetite and the oxidized NPs formed almost exclusively μm-scaled aggregates in acidic medium (pH=3, 4 and 5). The colloidal stability of magnetite at acidic pH would thus likely be hindered in aerobic environments because of its rapid oxidation into maghemite which lead to higher aggregation at most pH values

Evaluation of functional SiO2 nanoparticles toxicity by a 3D culture model

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