Spindle Assembly Checkpoint Protein Dynamics Reveal Conserved and Unsuspected Roles in Plant Cell Division

Background: In eukaryotes, the spindle assembly checkpoint (SAC) ensures that chromosomes undergoing mitosis do not segregate until they are properly attached to the microtubules of the spindle. Methodology/Principal Findings: We investigated the mechanism underlying this surveillance mechanism in plants, by characterising the orthogolous SAC proteins BUBR1, BUB3 and MAD2 from Arabidopsis. We showed that the cell cycle-regulated BUBR1, BUB3.1 and MAD2 proteins interacted physically with each other. Furthermore, BUBR1 and MAD2 interacted specifically at chromocenters. Following SAC activation by global defects in spindle assembly, these three interacting partners localised to unattached kinetochores. In addition, in cases of 'wait anaphase', plant SAC proteins were associated with both kinetochores and kinetochore microtubules. Unexpectedly, BUB3.1 was also found in the phragmoplast midline during the final step of cell division in plants. Conclusions/Significance: We conclude that plant BUBR1, BUB3.1 and MAD2 proteins may have the SAC protein functions conserved from yeast to humans. The association of BUB3.1 with both unattached kinetochore and phragmoplast suggests that in plant, BUB3.1 may have other roles beyond the spindle assembly checkpoint itself. Finally, this study of the SAC dynamics pinpoints uncharacterised roles of this surveillance mechanism in plant cell division

Inhibition of IL-10 Production by Maternal Antibodies against Group B Streptococcus GAPDH Confers Immunity to Offspring by Favoring Neutrophil Recruitment

Group B Streptococcus (GBS) is the leading cause of neonatal pneumonia, septicemia, and meningitis. We have previously shown that in adult mice GBS glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is an extracellular virulence factor that induces production of the immunosuppressive cytokine interleukin-10 (IL-10) by the host early upon bacterial infection. Here, we investigate whether immunity to neonatal GBS infection could be achieved through maternal vaccination against bacterial GAPDH. Female BALB/c mice were immunized with rGAPDH and the progeny was infected with a lethal inoculum of GBS strains. Neonatal mice born from mothers immunized with rGAPDH were protected against infection with GBS strains, including the ST-17 highly virulent clone. A similar protective effect was observed in newborns passively immunized with anti-rGAPDH IgG antibodies, or F(ab')2 fragments, indicating that protection achieved with rGAPDH vaccination is independent of opsonophagocytic killing of bacteria. Protection against lethal GBS infection through rGAPDH maternal vaccination was due to neutralization of IL-10 production soon after infection. Consequently, IL-10 deficient (IL-10−/−) mice pups were as resistant to GBS infection as pups born from vaccinated mothers. We observed that protection was correlated with increased neutrophil trafficking to infected organs. Thus, anti-rGAPDH or anti-IL-10R treatment of mice pups before GBS infection resulted in increased neutrophil numbers and lower bacterial load in infected organs, as compared to newborn mice treated with the respective control antibodies. We showed that mothers immunized with rGAPDH produce neutralizing antibodies that are sufficient to decrease IL-10 production and induce neutrophil recruitment into infected tissues in newborn mice. These results uncover a novel mechanism for GBS virulence in a neonatal host that could be neutralized by vaccination or immunotherapy. As GBS GAPDH is a structurally conserved enzyme that is metabolically essential for bacterial growth in media containing glucose as the sole carbon source (i.e., the blood), this protein constitutes a powerful candidate for the development of a human vaccine against this pathogen

THEORETICAL STUDY OF HIGH INJECTION EFFECTS IN EBIC MEASUREMENTS OF GRAIN BOUNDARY RECOMBINATION VELOCITY IN SILICON

The presence of carriers in the grain boundary (GB) space charge is taken into account in solving numerically Poisson's equation. This allows one, by using a schematic description of electron excitation, to investigate the theoretical behaviour of the GB recombination velocity, measured by EBIC, in high injection conditions

Study of a set of micrometeorites from Antarctica using magnetic and ESR methods coupled with micro-XRF

International audienceA collection of iron-rich micrometeorites from Antarctica have been investigated using electron spin resonance (ESR) and conventional magnetic methods to establish a complete magnetic codification of their specific characteristics. Due to the high selectivity of the ESR, the spectra show that the amount and nature of the magnetic impurities contained in these tiny-sized samples, mainly Ni and Cr ions, significantly modify their ESR responses. This result provides a criterion, the Ni/Cr content (identified by spectroscopy), useful for a faithful classification of this class of extraterrestrial particles with close magnetic properties. We attempt to separate the contribution of the different magnetic ions in the ESR response. This method can be easily extended to other magnetic impurities. (c) 2008 Elsevier B.V. All rights reserved

Exercice inter-laboratoire pour la mesure de la concentration massique des PM10 dans l'air ambiant

National audienceThe 1996 European directive on ambient has implemented regulatory monitoring of the PM10 mass concentration. The EN 12341 standard describes the European reference method (gravimetry). Any other method having demonstrated its equivalence to this reference can be carried out. France uses the Partisol Plus (TEI) as its national gravimetry reference method. For monitoring, the French networks (AASQA) use MP 101 RST radiometry Gauge (Environnement SA) and microbalance TEOM-FDMS (TEI). The European commission asked for a feed-back from the field. As a consequence, JRC Ispra is having a tour, sharing two weeks intercomparison exercises with each member country. Such a campaign has been carried out in France in March 2008. Participants have been JRC Ispra, the French National Laboratory (INERIS and EMD), and the Paris local Network (AIRPARIF). Results will be presented and commentedLa surveillance à travers l'Europe de la concentration massique des PM10 dans l'air ambiant extérieur a été rendue obligatoire par la directive Cadre de 1996 et la directive Fille associée de 1999. La méthode de référence à appliquer par les Etats Membres a été définie : il s'agit de la méthode manuelle gravimétrique décrite en détail dans la norme EN 12341. Toute technique alternative est jugée recevable sous réserve d'une démonstration d'équivalence par rapport à la méthode de référence. Lors des exercices d'équivalence nationaux, le dispositif français utilise le préleveur séquentiel sur filtres à bas débit Partisol Plus comme méthode gravimétrique de référence. En ce qui concerne la surveillance quotidienne des PM10, les AASQA utilisent la jauge radiométrique MP101M RST (société Environnement SA) et la microbalance TEOM-FDMS (société TEI). La Commission Européenne a souhaité disposer de données permettant de comparer la manière avec laquelle les différents pays membres assurent cette surveillance quotidienne. De ce fait, le JRC Ispra a entrepris un " tour d'Europe " consistant à mener, dans chaque pays membre, un exercice d'intercomparaison de deux semaines. Un tel exercice a été mené en France en mars 2008, impliquant d'un part le JRC, et d'autre part à la fois un représentant local du pays d'accueil (ici, AIRPARIF, réseau de surveillance de l'Ile de France), et le laboratoire national de référence (ici le LCSQA / INERIS et LCSQA / EMD). Les résultats obtenus seront présentés et commentés