ABCG transporters export cutin precursors for the formation of the plant cuticle

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Imaging cell interactions with native and crosslinked polyelectrolyte multilayers

The adhesion of primary chondrocytes to polyelectrolyte multilayer films, made of poly(l-lysine) (PLL) and hyaluronan (HA), was investigated for native and crosslinked films, either ending by PLL or HA. Crosslinking the film was achieved by means of a water-soluble carbodiimide in combination with N-hydroxysulfosuccinimide. The adhesion of macrophages and primary chondrocytes was investigated by microscopical techniques (optical, confocal, and atomic), providing useful information on the cell/film interface. Native films were found to be nonadhesive for the, primary chondrocytes, but could be degraded by macrophages, as could be visualized by confocal laser scanning microscopy after film labeling. Confocal microscopy images show that these films can be deformed by the condrocytes and that PLL diffuses at the chondrocyte membrane. In contrast, the cells adhered and proliferated well on the crosslinked films, which were not degraded by the macrophages. These results were confirmed by a MTT test over a 6-d period and by atomic force microscopy observations. We thus prove that chemical crosslinking can dramatically change cell adhesion properties, the cells being more stably anchored on the crosslinked films. Both authors kcontributed equally.     

The Contribution of Non-catalytic Carbohydrate Binding Modules to the Activity of Lytic Polysaccharide Monooxygenases

Lignocellulosic biomass is a sustainable industrial substrate. Copper-dependent lytic polysaccharide monooxygenases (LPMOs) contribute to the degradation of lignocellulose and increase the efficiency of biofuel production. LPMOs can contain non-catalytic carbohydrate binding modules (CBMs), but their role in the activity of these enzymes is poorly understood. Here we explored the importance of CBMs in LPMO function. The family 2a CBMs of two monooxygenases, CfLPMO10 and TbLPMO10 from Cellulomonas fimi and Thermobispora bispora, respectively, were deleted and/or replaced with CBMs from other proteins. The data showed that the CBMs could potentiate and, surprisingly, inhibit LPMO activity, and that these effects were both enzyme-specific and substrate-specific. Removing the natural CBM or introducing CtCBM3a, from the Clostridium thermocellum cellulosome scaffoldin CipA, almost abolished the catalytic activity of the LPMOs against the cellulosic substrates. The deleterious effect of CBM removal likely reflects the importance of prolonged presentation of the enzyme on the surface of the substrate for efficient catalytic activity, as only LPMOs appended to CBMs bound tightly to cellulose. The negative impact of CtCBM3a is in sharp contrast with the capacity of this binding module to potentiate the activity of a range of glycoside hydrolases including cellulases. The deletion of the endogenous CBM from CfLPMO10 or the introduction of a family 10 CBM from Cellvibrio japonicus LPMO10B into TbLPMO10 influenced the quantity of non-oxidized products generated, demonstrating that CBMs can modulate the mode of action of LPMOs. This study demonstrates that engineered LPMO-CBM hybrids can display enhanced industrially relevant oxygenations.     

Anti-cetuximab IgE ELISA for identification of patients at a high risk of cetuximab-induced anaphylaxis

Cetuximab, a chimeric mouse-human IgG1 monoclonal antibody against the epidermal growth factor receptor, has proven effective in the treatment of metastatic colorectal cancer and squamous cell carcinoma of the head and neck. However, a high incidence of immediate hypersensitivity reactions (HSR) to cetuximab after the first infusion has been observed. We have developed a test for identification of patients likely to show treatment-related HSR to cetuximab. An enzyme-linked immunosorbent assay (ELISA) for detecting anti-cetuximab IgEs was developed and tested on serum samples collected from cancer patients before start of cetuximab treatment, and from healthy blood donors. Similar levels of anti-cetuximab IgE were detected in pre-treatment patient sera (24/92, 26.1%) and sera from healthy blood donors (33/117, 28.2%). HSR were observed in 14 out of the 92 patients (15.2%), and 8 of these (57.1%) were grade 3–4. Anti-cetuximab IgEs were detected in 7/8 of the patients (87.5%) with severe HSRs as compared with 14/78 patients (17.9%) with no HSR (p = 0.0002). Predictive value of the anti-cetuximab IgE test for HSR events of grades 3–4 was calculated using Receiver Operating Characteristics analysis. With a cut-off value of 29 arbitrary units for the anti-cetuximab IgE, the ELISA test showed a sensitivity of 87.5%, specificity of 82.1%, positive predictive value of 33.3% and negative predictive value of 98.5%. Anti-cetuximab IgE ELISA detection could be a valuable tool to help the physician anticipate an anaphylaxis episode following cetuximab infusion and opt for a suitable alternative treatment.Key words: anti-cetuximab antibodies, ELISA, hypersensitivity, therapeutic monoclonal antibody, ROC     

Molecular Variability and Evolution of the Pectate Lyase (<Emphasis Type="Italic">pel</Emphasis>-2) Parasitism Gene in Cyst Nematodes Parasitizing Different <Emphasis Type="Italic">Solanaceous</Emphasis> Plants

While pectate lyases are major parasitism factors in plant-parasitic nematodes, there is little information on the variability of these genes within species and their utility as pathotype or host range molecular markers. We have analysed polymorphisms of pectate lyase 2 (pel-2) gene, which degrades the unesterified polygalacturonate (pectate) of the host cell-wall, in the genus Globodera. Molecular variability of the pel-2 gene and the predicted protein was evaluated in populations of G. rostochiensis, G. pallida, G. “mexicana” and G. tabacum. Seventy eight pel-2 sequences were obtained and aligned. Point mutations were observed at 373 positions, 57% of these affect the coding part of the gene and produce 129 aa replacements. The observed polymorphism does not correlate either to the pathotypes proposed in potato cyst nematodes (PCN) or the subspecies described in tobacco cyst nematodes. The trees reveal a topology different from the admitted species topology as G. rostochiensis and G. pallida sequences are more similar to each other than to G. tabacum. Species-specific sites, potentially applicable for identification, and sites distinguishing PCN from tobacco cyst nematodes, were identified. As both G. rostochiensis and G. pallida display the same host range, but distinct from G. tabacum, which cannot parasitize potato plants, it is tempting to speculate that pel-2 genes polymorphism may be implicated in this adaptation, a view supported by the fact that no active pectate lyase 2 was found in G. “mexicana”, a close relative of G. pallida that is unable to develop on cultivated potato varieties.     

Trends in tuna carbon isotopes suggest global changes in pelagic phytoplankton communities

Considerable uncertainty remains over how increasing atmospheric CO₂ and anthropogenic climate changes are affecting open‐ocean marine ecosystems from phytoplankton to top predators. Biological time series data are thus urgently needed for the world's oceans. Here, we use the carbon stable isotope composition of tuna to provide a first insight into the existence of global trends in complex ecosystem dynamics and changes in the oceanic carbon cycle. From 2000 to 2015, considerable declines in δ¹³C values of 0.8‰–2.5‰ were observed across three tuna species sampled globally, with more substantial changes in the Pacific Ocean compared to the Atlantic and Indian Oceans. Tuna recorded not only the Suess effect, that is, fossil fuel‐derived and isotopically light carbon being incorporated into marine ecosystems, but also recorded profound changes at the base of marine food webs. We suggest a global shift in phytoplankton community structure, for example, a reduction in ¹³C‐rich phytoplankton such as diatoms, and/or a change in phytoplankton physiology during this period, although this does not rule out other concomitant changes at higher levels in the food webs. Our study establishes tuna δ¹³C values as a candidate essential ocean variable to assess complex ecosystem responses to climate change at regional to global scales and over decadal timescales. Finally, this time series will be invaluable in calibrating and validating global earth system models to project changes in marine biota.     

Scaling laws of ambush predator ‘waiting’ behaviour are tuned to a common ecology

The decisions animals make about how long to wait between activities can determine the success of diverse behaviours such as foraging, group formation or risk avoidance. Remarkably, for diverse animal species, including humans, spontaneous patterns of waiting times show random ‘burstiness’ that appears scale-invariant across a broad set of scales. However, a general theory linking this phenomenon across the animal kingdom currently lacks an ecological basis. Here, we demonstrate from tracking the activities of 15 sympatric predator species (cephalopods, sharks, skates and teleosts) under natural and controlled conditions that bursty waiting times are an intrinsic spontaneous behaviour well approximated by heavy-tailed (power-law) models over data ranges up to four orders of magnitude. Scaling exponents quantifying ratios of frequent short to rare very long waits are species-specific, being determined by traits such as foraging mode (active versus ambush predation), body size and prey preference. A stochastic–deterministic decision model reproduced the empirical waiting time scaling and species-specific exponents, indicating that apparently complex scaling can emerge from simple decisions. Results indicate temporal power-law scaling is a behavioural ‘rule of thumb’ that is tuned to species’ ecological traits, implying a common pattern may have naturally evolved that optimizes move–wait decisions in less predictable natural environments.     

Non Digestible Oligosaccharides Modulate the Gut Microbiota to Control the Development of Leukemia and Associated Cachexia in Mice

We tested the hypothesis that changing the gut microbiota using pectic oligosaccharides (POS) or inulin (INU) differently modulates the progression of leukemia and related metabolic disorders. Mice were transplanted with Bcr-Abl-transfected proB lymphocytes mimicking leukemia and received either POS or INU in their diet (5%) for 2 weeks. Combination of pyrosequencing, PCR-DGGE and qPCR analyses of the 16S rRNA gene revealed that POS decreased microbial diversity and richness of caecal microbiota whereas it increased Bifidobacterium spp., Roseburia spp. and Bacteroides spp. (affecting specifically B. dorei) to a higher extent than INU. INU supplementation increased the portal SCFA propionate and butyrate, and decreased cancer cell invasion in the liver. POS treatment did not affect hepatic cancer cell invasion, but was more efficient than INU to decrease the metabolic alterations. Indeed, POS better than INU delayed anorexia linked to cancer progression. In addition, POS treatment increased acetate in the caecal content, changed the fatty acid profile inside adipose tissue and counteracted the induction of markers controlling β-oxidation, thereby hampering fat mass loss. Non digestible carbohydrates with prebiotic properties may constitute a new nutritional strategy to modulate gut microbiota with positive consequences on cancer progression and associated cachexia.     

An european pupil project linked to the scientific aims of the experiment AQUARIUS-XENOPUS on the taxi Soyuz flight Andromede to ISS

The German-French biological experiment AQUARIUS-XENOPUS which flew on the Soyuz flight Andromede to the International Space Station ISS (launched October 21, 2001 in Baikonour/Kazakhstan) was extended by an outreach project. Pupils of class 10 to 12 from Ulm/D and Nancy-Tomblaine/F studied swimming behavior of Xenopus tadpoles on ground. They were instructed to perform all experimental steps following the protocol of similar video recordings on ISS. After the flight, they evaluated the kinetics of swimming of both ground controls and space animals. The pupil project included theoretical components to introduce them to the field of gravitational biology. One feature of the project was the exchange of ideas between pupils by meetings which took place in Ulm (June 2001), Nancy (February 2002) and Paris (May 2002). We consider our approach as a successful way to include young people in space experiments on a cheap cost level and to bring ideas of gravitational biology into the curricula of European schools.