Geomagnetic Dipole Changes and Upwelling/Downwelling at the Top of the Earth's Core

The convective state of the top of Earth's outer core is still under debate. Conflicting evidence from seismology and geomagnetism provides arguments for and against a thick stably stratified layer below the core-mantle boundary. Mineral physics and cooling scenarios of the core favor a stratified layer. However, a non-zero secular variation of the total geomagnetic energy on the core-mantle boundary is evidence for the presence of radial motions extending to the top of the core. We compare the secular variation of the total geomagnetic energy with the secular variation of the geomagnetic dipole intensity and tilt. We demonstrate that both the level of cancellations of the sources and sinks of the dipole intensity secular variation, as well as the level of cancellations of the sources and sinks of the dipole tilt secular variation, are either larger than or comparable to the level of cancellations of the sources and sinks of the total geomagnetic energy secular variation on the core-mantle boundary, indicating that the latter is numerically significant hence upwelling/downwelling reach the top of the core. Radial motions below the core-mantle boundary are either evidence for no stratified layer or to its penetration by various dynamical mechanisms, most notably lateral heterogeneity of core-mantle boundary heat flux

Construction of two genetic linkage maps in cultivated tetraploid alfalfa (Medicago sativa) using microsatellite and AFLP markers

BACKGROUND: Alfalfa (Medicago sativa) is a major forage crop. The genetic progress is slow in this legume species because of its autotetraploidy and allogamy. The genetic structure of this species makes the construction of genetic maps difficult. To reach this objective, and to be able to detect QTLs in segregating populations, we used the available codominant microsatellite markers (SSRs), most of them identified in the model legume Medicago truncatula from EST database. A genetic map was constructed with AFLP and SSR markers using specific mapping procedures for autotetraploids. The tetrasomic inheritance was analysed in an alfalfa mapping population. RESULTS: We have demonstrated that 80% of primer pairs defined on each side of SSR motifs in M. truncatula EST database amplify with the alfalfa DNA. Using a F1 mapping population of 168 individuals produced from the cross of 2 heterozygous parental plants from Magali and Mercedes cultivars, we obtained 599 AFLP markers and 107 SSR loci. All but 3 SSR loci showed a clear tetrasomic inheritance. For most of the SSR loci, the double-reduction was not significant. For the other loci no specific genotypes were produced, so the significant double-reduction could arise from segregation distortion. For each parent, the genetic map contained 8 groups of four homologous chromosomes. The lengths of the maps were 2649 and 3045 cM, with an average distance of 7.6 and 9.0 cM between markers, for Magali and Mercedes parents, respectively. Using only the SSR markers, we built a composite map covering 709 cM. CONCLUSIONS: Compared to diploid alfalfa genetic maps, our maps cover about 88–100% of the genome and are close to saturation. The inheritance of the codominant markers (SSR) and the pattern of linkage repulsions between markers within each homology group are consistent with the hypothesis of a tetrasomic meiosis in alfalfa. Except for 2 out of 107 SSR markers, we found a similar order of markers on the chromosomes between the tetraploid alfalfa and M. truncatula genomes indicating a high level of colinearity between these two species. These maps will be a valuable tool for alfalfa breeding and are being used to locate QTLs

The molecular genetic linkage map of the model legume Medicago truncatula: an essential tool for comparative legume genomics and the isolation of agronomically important genes

BACKGROUND: The legume Medicago truncatula has emerged as a model plant for the molecular and genetic dissection of various plant processes involved in rhizobial, mycorrhizal and pathogenic plant-microbe interactions. Aiming to develop essential tools for such genetic approaches, we have established the first genetic map of this species. Two parental homozygous lines were selected from the cultivar Jemalong and from the Algerian natural population (DZA315) on the basis of their molecular and phenotypic polymorphism. RESULTS: An F2 segregating population of 124 individuals between these two lines was obtained using an efficient manual crossing technique established for M. truncatula and was used to construct a genetic map. This map spans 1225 cM (average 470 kb/cM) and comprises 289 markers including RAPD, AFLP, known genes and isoenzymes arranged in 8 linkage groups (2n = 16). Markers are uniformly distributed throughout the map and segregation distortion is limited to only 3 linkage groups. By mapping a number of common markers, the eight linkage groups are shown to be homologous to those of diploid alfalfa (M. sativa), implying a good level of macrosynteny between the two genomes. Using this M. truncatula map and the derived F3 populations, we were able to map the Mtsym6 symbiotic gene on linkage group 8 and the SPC gene, responsible for the direction of pod coiling, on linkage group 7. CONCLUSIONS: These results demonstrate that Medicago truncatula is amenable to diploid genetic analysis and they open the way to map-based cloning of symbiotic or other agronomically-important genes using this model plant

QTL analysis of seed germination and pre-emergence growth at extreme temperatures in Medicago truncatula

Enhancing the knowledge on the genetic basis of germination and heterotrophic growth at extreme temperatures is of major importance for improving crop establishment. A quantitative trait loci (QTL) analysis was carried out at sub- and supra-optimal temperatures at these early stages in the model Legume Medicago truncatula. On the basis of an ecophysiological model framework, two populations of recombinant inbred lines were chosen for the contrasting behaviours of parental lines: LR5 at sub-optimal temperatures (5 or 10°C) and LR4 at a supra-optimal temperature (20°C). Seed masses were measured in all lines. For LR5, germination rates and hypocotyl growth were measured by hand, whereas for LR4, imbibition and germination rates as well as early embryonic axis growth were measured using an automated image capture and analysis device. QTLs were found for all traits. The phenotyping framework we defined for measuring variables, distinguished stages and enabled identification of distinct QTLs for seed mass (chromosomes 1, 5, 7 and 8), imbibition (chromosome 4), germination (chromosomes 3, 5, 7 and 8) and heterotrophic growth (chromosomes 1, 2, 3 and 8). The three QTL identified for hypocotyl length at sub-optimal temperature explained the largest part of the phenotypic variation (60% together). One digenic interaction was found for hypocotyl width at sub-optimal temperature and the loci involved were linked to additive QTLs for hypocotyl elongation at low temperature. Together with working on a model plant, this approach facilitated the identification of genes specific to each stage that could provide reliable markers for assisting selection and improving crop establishment. With this aim in view, an initial set of putative candidate genes was identified in the light of the role of abscissic acid/gibberellin balance in regulating germination at high temperatures (e.g. ABI4, ABI5), the molecular cascade in response to cold stress (e.g. CBF1, ICE1) and hypotheses on changes in cell elongation (e.g. GASA1, AtEXPA11) with changes in temperatures based on studies at the whole plant scale

Disseminated and circulating tumor cells in gastrointestinal oncology.

International audienceCirculating (CTCs) and disseminated tumor cells (DTCs) are two different steps in the metastatic process. Several recent techniques have allowed detection of these cells in patients, and have generated many results using different isolation techniques in small cohorts. Herein, we review the detection results and their clinical consequence in esophageal, gastric, pancreatic, colorectal, and liver carcinomas, and discuss their possible applications as new biomarkers

26th Annual Computational Neuroscience Meeting (CNS*2017): Part 3 - Meeting Abstracts - Antwerp, Belgium. 15–20 July 2017

This work was produced as part of the activities of FAPESP Research,\ud Disseminations and Innovation Center for Neuromathematics (grant\ud 2013/07699-0, S. Paulo Research Foundation). NLK is supported by a\ud FAPESP postdoctoral fellowship (grant 2016/03855-5). ACR is partially\ud supported by a CNPq fellowship (grant 306251/2014-0)

Étude de la spécificité d'hôte pour la nodulation et la fixation de l'azote dans la symbiose Sinorhizobium-Medicago truncatula (identification de nouveaux gènes)

Dans l'objectif de rechercher du polymorphisme symbiotique, nous avons inoculé des lignées naturelles de Medicago truncatula avec des souches sauvages de Sinorhizobium meliloti. Ainsi, nous avons ainsi mis en évidence un important polymorphisme de nodulation et de fixation de l'azote. Deux polymorphismes ont fait l'objet d'une étude détaillée. M. truncatula DZA315.16 inoculée avec S. meliloti cc2020 aboutit à une interaction spécifique incompatible de type non-nodulant (Nod-). Le phénotype Nod- présente des déformations et courbures des poils absorbants, une absence des cordons d'infection et des divisions des cellules du cortex. Ce phénotype est sous le contrôle de deux gènes, Mtsym4 et Mtsym5 seraient impliqués dans la perception des facteurs Nod. S. meliloti A145 induit chez M. truncatula Jemalong 6 de petits nodules blancs non-fixateurs (Fix-). L'analyse cytologique a révélé une dégénérescence progressive du méristème et des cellules du nodule, la présence de cordons d'infection trapus et autofluorescents suggérant des réactions de défense et enfin à un stade tardif la fermeture de l'endoderme nodulaire. Le phénotype Fix- est sous le contrôle d'un gène récessif Mtsym6,cartographié sur le groupe de liaison huit de la carte génétique de M. truncatula. Les expériences de greffe ont montré que les phénotypes Nod- et Fix- sont sous le contrôle des parties racinaires de la plante.notre travail via l'analyse des interactions de spécificité de nodulation et de fixation de l'azote nous a permis de faire un parallèle avec les interactions gène par gène. L'implication des réactions de défense dans les phénotypes observés, pose la question de la place de la symbiose dans les relations plantes-microorganismes.TOULOUSE-ENSAT-Documentation (315552324) / SudocSudocFranceF

Magnetic to magnetic and kinetic to magnetic energy transfers at the top of the Earth's core

International audienc

Geomagnetic Dipole Changes and Upwelling/Downwelling at the Top of the Earth's Core

International audienceThe convective state of the top of Earth's outer core is still under debate. Conflicting evidence from seismology and geomagnetism provides arguments for and against a thick stably stratified layer below the core-mantle boundary. Mineral physics and cooling scenarios of the core favor a stratified layer. However, a non-zero secular variation of the total geomagnetic energy on the core-mantle boundary is evidence for the presence of radial motions extending to the top of the core. We compare the secular variation of the total geomagnetic energy with the secular variation of the geomagnetic dipole intensity and tilt. We demonstrate that both the level of cancellations of the sources and sinks of the dipole intensity secular variation, as well as the level of cancellations of the sources and sinks of the dipole tilt secular variation, are either larger than or comparable to the level of cancellations of the sources and sinks of the total geomagnetic energy secular variation on the core-mantle boundary, indicating that the latter is numerically significant hence upwelling/downwelling reach the top of the core. Radial motions below the core-mantle boundary are either evidence for no stratified layer or to its penetration by various dynamical mechanisms, most notably lateral heterogeneity of core-mantle boundary heat flux