In Ovo Olfactory Experience Influences Post‐hatch Feeding Behaviour in Young Chickens

In several mammalian species, prenatal exposure to odours can elicit later positive consummatory behaviour in response to substrates bearing that odorant. In birds, the sense of smell has been considerably underestimated, and very little is known about the effects of early sensory experience on the regulation of feeding behaviour. We tested the hypothesis that the feeding behaviour of the domestic chicken could be regulated by olfactory learning during the embryonic life. To that end, chicken embryos were exposed to an olfactory stimulus (blend of essential oil of orange and nature identical vanillin) from embryonic day (ED) 12 to ED20, and chicks were tested between 4 and 9 d of age. In short‐term choice tests, at day 4 and 5, chickens previously exposed to a low concentration (LC) of the olfactory stimulus spent a higher proportion of time eating a familiar or an unfamiliar food bearing the olfactory stimulus compared to non‐exposed control chickens. Conversely, chickens previously exposed to a high concentration (HC) of the olfactory stimulus were found to avoid all foods bearing the olfactory stimulus. On a 24‐ h time scale at day 7–8, LC and HC birds, but not controls, ingest significantly less familiar food containing the olfactory stimulus. This result indicated a long‐term effect of the early olfactory experience on feeding preferences. We demonstrated that chickens can utilize information from their pre‐hatch chemosensory environment to guide their later feeding behaviour. A pre‐hatch effect of the intensity of odour signals in the regulation of feeding behaviour is reported here for the first time.     

Phosphatidylinositol-4,5-bisphosphate promotes budding yeast septin filament assembly and organization

Septins are a conserved family of GTP-binding proteins that assemble into symmetric linear heterooligomeric complexes, which in turn are able to polymerize into apolar filaments and higher-order structures. In budding yeast (Saccharomyces cerevisiae) and other eukaryotes, proper septin organization is essential for processes that involve membrane remodeling, such as the execution of cytokinesis. In yeast, four septin subunits form a Cdc11-Cdc12-Cdc3-Cdc10-Cdc10-Cdc3-Cdc12-Cdc11 heterooctameric rod that polymerizes into filaments thought to form a collar around the bud neck in close contact with the inner surface of the plasma membrane. To explore septin-membrane interactions, we examined the effect of lipid monolayers on septin organization at the ultrastructural level using electron microscopy. Using this methodology, we have acquired new insights into the potential effect of septin-membrane interactions on filament assembly and, more specifically, on the role of phosphoinositides. Our studies demonstrate that budding yeast septins interact specifically with phosphatidylinositol-4,5-bisphosphate (PIP2) and indicate that the N terminus of Cdc10 makes a major contribution to the interaction of septin filaments with PIP2. Furthermore, we found that the presence of PIP2 promotes filament polymerization and organization on monolayers, even under conditions that prevent filament formation in solution or for mutants that prevent filament formation in solution. In the extreme case of septin complexes lacking the normally terminal subunit Cdc11 or the normally central Cdc10 doublet, the combination of the PIP2-containing monolayer and nucleotide permitted filament formation in vitro via atypical Cdc12-Cdc12 and Cdc3-Cdc3 interactions, respectively.     

Fluorescent sperm marking to improve the fight against the pest insect Ceratitis capitata (Wiedemann; Diptera: Tephritidae)

The Sterile Insect Technique (SIT) involving area-wide release of mass-reared and sterilized pest insects has proven successful to reduce, control and eradicate economically important pest species, such as the Mediterranean fruit fly (medfly). For the efficient application, effective monitoring to assess the number and mating success of the released medflies is essential. Here, we report sperm-specific marking systems based on the spermatogenesis-specific Ceratitis capitata beta2-tubulin (Ccbeta2t) promoter. Fluorescent sperm can be isolated from testes or spermathecae. The marking does not cause general disadvantages in preliminary laboratory competitiveness assays. Therefore, transgenic sperm marking could serve as a major improvement for monitoring medfly SIT programs. The use of such harmless transgenic markers will serve as an ideal initial condition to transfer insect transgenesis technology from the laboratory to field applications. Moreover, effective and easily recognizable sperm marking will make novel studies possible on medfly reproductive biology which will help to further improve SIT programs.     

Murine Nod1 but not its human orthologue mediates innate immune detection of tracheal cytotoxin

Tracheal cytotoxin (TCT) was originally described as the minimal effector that was able to reproduce the cytotoxic response of Bordetella pertussis on ciliated epithelial cells. This molecule triggers pleiotropic effects such as immune stimulation or slow-wave sleep modulation. Further characterization identified TCT as a specific diaminopimelic acid (DAP)-containing muropeptide, GlcNAc-(anhydro)MurNAc-L-Ala-D-Glu-mesoDAP-D-Ala. Here, we show that the biological activity of TCT depends on Nod1, an intracellular sensor of bacterial peptidoglycan. However, Nod1-dependent detection of TCT was found to be host specific, as human Nod1 (hNod1) poorly detected TCT, whereas mouse Nod1 (mNod1) did so efficiently. More generally, hNod1 required a tripeptide (L-Ala-D-Glu-mesoDAP) for efficient sensing of peptidoglycan, whereas mNod1 detected a tetrapeptide structure (L-Ala-D-Glu-mesoDAP-D-Ala). In murine macrophages, TCT stimulated cytokine secretion and NO production through Nod1. Finally, in vivo, injection of the tetrapeptide structure in mice triggered a transient yet strong release of cytokines into the bloodstream and the maturation of macrophages, in a Nod1-dependent manner. This study thereby identifies Nod1 as the long sought after sensor of TCT in mammals.     

A novel technique to evaluate interactions between Saccharomyces cerevisiae cell wall and mycotoxins: application to zearalenone

Three models based on sigmoidal plotting were tested for their ability to describe zearalenone adsorption on Saccharomyces cerevisiae cell walls in vitro. All three models closely fitted the experimental data, but Hill's equation gave the most accurate parameters, and provided information on the physical and chemical mechanisms involved in the adsorption of mycotoxin on yeast cell walls.     

A model for an early stage of tomato fruit development: cell multiplication and cessation of the cell proliferative activity

Changes in cell number during the early period of tomato fruit development were analysed by means of a deterministic model of cell multiplication. The period commenced at the seed stage with one theoretical cell undergoing intensive cell division, and ended when the cell number became nearly constant. The model takes into consideration the proliferative activity of the fruit cell population which, a few days before flower anthesis, begins to decrease progressively after each mitotic cycle. Model parameters, namely the time at which proliferative activity diminishes, its rate of decrease and the length of the cell cycle, were estimated by fitting the model to observed cell population dynamics in tomato fruits growing in three different positions on the truss. It is hypothesized that the molecular mechanism responsible for the cessation of mitosis in growing fruits is associated with shortening of telomeric ends of nuclear DNA, as suggested previously for other growing cell populations.     

Localization of the Insertion Site and Pathotype Determination of the Locus of Enterocyte Effacement of Shiga Toxin-Producing Escherichia coli Strains

Of 220 Shiga toxin-producing Escherichia coli (STEC) strains collected in central France from healthy cattle, food samples, and asymptomatic children, 12 possessed the eae gene included in the locus of enterocyte effacement (LEE) pathogenicity island. Based on gene typing, we observed 7 different eae espA espB tir pathotypes among the 12 STEC strains and described the new espAβv variant. As previously observed, the O157 serogroup is associated with eaeγ, O26 is associated with eaeβ, and O103 is associated with eae. However, the unexpected eaeζ allele was detected in 5 of the 12 isolates. PCR amplification and pulsed-field gel electrophoresis using the I-CeuI endonuclease followed by Southern hybridization indicated that the LEE was inserted in the vicinity of the selC (three isolates), pheU (two isolates), or pheV (six isolates) tRNA gene. Six isolates harbored two or three of these tRNA loci altered by the insertion of integrase genes (CP4-int and/or int-phe), suggesting the insertion of additional foreign DNA fragments at these sites. In spite of great genetic diversity of LEE pathotypes and LEE insertion sites, bovine strains harbor alleles of LEE genes that are frequently found in clinical STEC strains isolated from outbreaks and sporadic cases around the world, underscoring the potential risk of the bovine strains on human health.     

Direct evidence that toll-like receptor 9 (TLR9) functionally binds plasmid DNA by specific cytosine-phosphate-guanine motif recognition

Cytosine-phosphate-guanine (CpG) motifs in bacterial DNA are known to activate the mammalian immune system, and this activation is thought to depend on the Toll-like receptor 9 (TLR9) signaling pathway. Previous studies strongly suggested that TLR9 is involved as the specific receptor for CpG motifs but did not provide direct evidence of their interaction. In this study, we demonstrate for the first time that murine TLR9 binds an unmethylated CpG-containing plasmid. This interaction is sequence-specific and is influenced by the methylation status of the plasmid. Furthermore, we demonstrate that this interaction leads to the activation of the NF-kappaB pathway in mTLR9-expressing cells. Our results provide a molecular basis for the interaction between CpG-DNA and TLR9.     

Comprehensive conformational study of key interactions involved in zearalenone complexation with beta-D-glucans

The beta-D-glucans from the cell wall of Saccharomyces cerevisiae have shown in vitro affinity for zearalenone. For this reason, their utilization as dietary adsorbent, to reduce the bioavailability of zearalenone, is of practical interest. Our study used powerful devices to elucidate the spatial conformation and molecular sites of interaction between ZEN and beta-D-glucans. In this respect, 1H NMR spectroscopy implicated the hydroxyl groups of the phenol moiety of zearalenone in the complexation by laminarin, a pure beta-(1,3)-D-glucan. X-ray diffraction determined that laminarin displays the conformation of a single-helix with six beta-D-glucopyranose residues per turn. At this stage, molecular modeling was useful to locate the interaction sites and to propose highly probable complexes of zearalenone with laminarin fragment. Interestingly, the beta-(1,3)-D-glucan chain favors a very stable intra-helical association with zearalenone, nicely stabilized by beta-(1,6)-D-glucans side chains. Both hydrogen bonds and van der Waals interactions were precisely identified in the complex and could thus be proposed as driving interactions to monitor the association between the two molecules.