Using genotyping-by-sequencing to understand Musa diversity : [P449]

This project is part of a larger effort to apply genomics technologies to assess genetic diversity and to advance genetic improvement efforts in Musa (banana and plantain), a major staple food crop in the developing world. Most cultivated varieties of bananas result from intra- or inter-specific crosses of the wild diploid species, Musa acuminata (A genome) and Musa balbisiana (B genome). Somaclonal mutation and human selection has resulted in current day bananas with a wide morphological diversity. The Cavendish (AAA) subgroups are believed to have derived from an individual unique initial genotype, and similarly for the subgroup plantain (AAB). However, little or no genetic diversity can be detected within these groups using conventional molecular markers such as RFLP, SSR, DArT. To assess genetic diversity with an improved resolution, we have selected 65 accessions with diploid and triploid combinations of the A and/or B genomes including AAB plantains and AAA Cavendish, and cultivated or wild Musa accessions from the core collection at the Global Musa Genomics Consortium (GMGC) (http://www.musagenomics.org). We have used a high-throughput reduced representation genome sequencing approach - genotyping-by-sequencing (GBS) to obtain high density sequence markers. Genotypes are determined for each diploid and triploid accession, and dissimilarity computed across all accessions. We will discuss the value of GBS markers to characterize the genetic diversity of individual Musa subgroups with high resolution. This work is funded by the USAID linkage funds. (Texte intégral

An extremal model for amorphous media plasticity

An extremal model for the plasticity of amorphous materials is studied in a simple two-dimensional anti-plane geometry. The steady-state is analyzed through numerical simulations. Long-range spatial and temporal correlations in local slip events are shown to develop, leading to non-trivial and highly anisotropic scaling laws. In particular, the plastic strain is shown to statistically concentrate over a region which tends to align perpendicular to the displacement gradient. By construction, the model can be seen as giving rise to a depinning transition, the threshold of which (i.e. the macroscopic yield stress) also reveal scaling properties reflecting the localization of the activity.Comment: 4 pages, 5 figure

Applications of liquid chromatography coupled to mass spectrometry-based metabolomics in clinical chemistry and toxicology: A review.

International audienceThe metabolome is the set of small molecular mass organic compounds found in a given biological media. It includes all organic substances naturally occurring from the metabolism of the studied living organism, except biological polymers, but also xenobiotics and their biotransformation products. The metabolic fingerprints of biofluids obtained by mass spectrometry (MS) or nuclear magnetic resonance (NMR)-based methods contain a few hundreds to thousands of signals related to both genetic and environmental contributions. Metabolomics, which refers to the untargeted quantitative or semi-quantitative analysis of the metabolome, is a promising tool for biomarker discovery. Although proof-of-concept studies by metabolomics-based approaches in the field of toxicology and clinical chemistry have initially been performed using NMR, the use of liquid chromatography hyphenated to mass spectrometry (LC/MS) has increased over the recent years, providing complementary results to those obtained with other approaches. This paper reviews and comments the input of LC/MS in this field. We describe here the overall process of analysis, review some seminal papers in the field and discuss the perspectives of metabolomics for the biomonitoring of exposure and diagnosis of diseases

Comment on “The biosphere: A homogeniser of Pb-isotope signals” by C. Reimann, B. Flem, A. Arnoldussen, P. Englmaier, T.E. Finne, F. Koller and Ø. Nordgulen

Reimann et al. (2008) recently published a study on Pb-isotope signature along a 120 km long transect cutting the city of Oslo. Based on concentration but also isotope data, they misinterpret Pb concentration of the biosphere in rural places and explain these large enrichments of Pb as being due to natural processes. The study ignores numerous previous studies either on local, regional or global scales (see reviews by Shotyk and Le Roux, 2005 and Callender, 2003, and references therein), which clearly demonstrate that anthropogenic Pb emitted in the atmosphere from different sources (leaded gasoline, coal burning, metallurgy, etc.) was and is dispersed worldwide. The study also ignores work on Norway by the Steinnes and colleagues group (Harmens et al., 2008, Steinnes et al., 2005a, Steinnes et al., 2005b and Åberg et al., 2004), and measurements and modelling by the EMEP network (www.emep.int/, EMEP, 2005). The study also neglects numerous works on preanthropogenic Pb deposition rate and isotopic signature using continental archives of atmospheric deposition like peat bogs (Shotyk et al., 1998, Klaminder et al., 2003, Kylander et al., 2005 and Le Roux et al., 2005). These studies have shown that preanthropogenic Pb atmospheric deposition rate and its Pb isotopic signature is regionally defined, but also that those signals are negligible compared to past 2 ka and recent Pb atmospheric fluxes (Table 1)