A life course perspective on social and family formation transitions to adulthood of young men and women in Mexico

This research examines the trajectories that young men and women in Mexico experienced during their transition to adulthood in the 1980s and 1990s. The study, particularly, considers two groups of significant markers of adulthood: social transitions (leaving education, entry into the labour force, parental home leaving), and family formation transitions (first sex, first partnership, and first birth). The thesis investigates the ways that these transitions were experienced among Mexican youth: first, by establishing the main interactions between social transitions and family formation transitions to adulthood; and second, by providing evidence of the main trajectories followed by young men and women in their passage to adulthood from a life course perspective. Applying Event History techniques to retrospective data from the 2000 Mexican National Youth Survey, results show that young men and women experienced different patterns of trajectories in their transit to adulthood marked by a strong gender component. While young men showed a lag between the experience of social and family formation transitions characterized by work-oriented trajectories, young women often experienced almost simultaneous occurrence of social and family formation transitions leading to predominantly family-oriented trajectories to adulthood. Differences between urban and rural respondents were also found to be significant. Another conclusion of the study is that many young people found great difficulty in obtaining their first job after leaving education, leading to high unemployment. Despite the lack of employment opportunities for Mexican young people, family formation transitions were not substantially postponed until later ages unlike many developed nations. The findings also confirm the importance of education on the experience of transitions to adulthood. The study shows the need to restructure the Mexican educational system to enable young people to work and study simultaneously, without having to leave education immediately after entering the labour force. These findings highlight the need to strengthen and reinforce current education policies to stimulate labour force participation of young women

Identification de signaux audio par appariement de chaînes

Le fingerprint audio est un court résumé d'un document audio calculé à partir des propriétés du signal. Comme l'empreinte digitale humaine, le fingerprint audio permet d'identifier un document audio parmi un lot de candidats sans en déduire aucune autre caractéristique. Dans cet article, nous proposons une méthode d'extraction de fingerprint basée sur une nouvelle méthode de segmentation adaptative du signal. La combinaison d'une méthode d'appariement de chaîne avec un pré-filtrage par q-grams permet d'identifier un extrait audio inconnu et de décider si cet extrait est une version dérivée d'un fingerprint préalablement calculé et stocké ou si aucun fingerprint de la base de donnée de correspond à l'extrait d'entrée

Dissecting new genetic components of salinity tolerance in two-row spring barley at the vegetative and reproductive stages

Soil salinity imposes an agricultural and economic burden that may be alleviated by identifying the components of salinity tolerance in barley, a major crop and the most salt tolerant cereal. To improve our understanding of these components, we evaluated a diversity panel of 377 two-row spring barley cultivars during both the vegetative, in a controlled environment, and the reproductive stages, in the field. In the controlled environment, a high-throughput phenotyping platform was used to assess the growth-related traits under both control and saline conditions. In the field, the agronomic traits were measured from plots irrigated with either fresh or saline water. Association mapping for the different components of salinity tolerance enabled us to detect previously known associations, such as HvHKT1;5. Using an "interaction model", which took into account the interaction between treatment (control and salt) and genetic markers, we identified several loci associated with yield components related to salinity tolerance. We also observed that the two developmental stages did not share genetic regions associated with the components of salinity tolerance, suggesting that different mechanisms play distinct roles throughout the barley life cycle. Our association analysis revealed that genetically defined regions containing known flowering genes (Vrn-H3, Vrn-H1, and HvNAM-1) were responsive to salt stress. We identified a salt-responsive locus (7H, 128.35 cM) that was associated with grain number per ear, and suggest a gene encoding a vacuolar H+-translocating pyrophosphatase, HVP1, as a candidate. We also found a new QTL on chromosome 3H (139.22 cM), which was significant for ear number per plant, and a locus on chromosome 2H (141.87 cM), previously identified using a nested association mapping population, which associated with a yield component and interacted with salinity stress. Our study is the first to evaluate a barley diversity panel for salinity stress under both controlled and field conditions, allowing us to identify contributions from new components of salinity tolerance which could be used for marker-assisted selection when breeding for marginal and saline regions

The Genome Sequence of the Wild Tomato Solanum pimpinellifolium Provides Insights Into Salinity Tolerance

Solanum pimpinellifolium, a wild relative of cultivated tomato, offers a wealth of breeding potential for desirable traits such as tolerance to abiotic and biotic stresses. Here, we report the genome assembly and annotation of S. pimpinellifolium ‘LA0480.’ Moreover, we present phenotypic data from one field experiment that demonstrate a greater salinity tolerance for fruit- and yield-related traits in S. pimpinellifolium compared with cultivated tomato. The ‘LA0480’ genome assembly size (811 Mb) and the number of annotated genes (25,970) are within the range observed for other sequenced tomato species. We developed and utilized the Dragon Eukaryotic Analyses Platform (DEAP) to functionally annotate the ‘LA0480’ protein-coding genes. Additionally, we used DEAP to compare protein function between S. pimpinellifolium and cultivated tomato. Our data suggest enrichment in genes involved in biotic and abiotic stress responses. To understand the genomic basis for these differences in S. pimpinellifolium and S. lycopersicum, we analyzed 15 genes that have previously been shown to mediate salinity tolerance in plants. We show that S. pimpinellifolium has a higher copy number of the inositol-3-phosphate synthase and phosphatase genes, which are both key enzymes in the production of inositol and its derivatives. Moreover, our analysis indicates that changes occurring in the inositol phosphate pathway may contribute to the observed higher salinity tolerance in ‘LA0480.’ Altogether, our work provides essential resources to understand and unlock the genetic and breeding potential of S. pimpinellifolium, and to discover the genomic basis underlying its environmental robustness

Les diatomees du lac de maar du Bouchet (Massif-Central, France) : reconstruction du paleoenvironnement depuis les 120 derniers millenaires

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Heterochromatin as a pluripotency marker : comparison between in vivo (mammals embryos) and in vitro (stem cells) models

A la suite de la fécondation, le génome embryonnaire subit différents remodelages épigénétiques et structuraux, nécessaires à son activation. Ces différents remaniements se poursuivent tout au long du développement, alors que l’embryon progresse de l’état de totipotence vers la pluripotence et la différentiation. La pluripotence est un état complexe et transitoire au cours duquel les cellules à l’origine du futur organisme progressent d’un état « naïf » vers un état « amorcé ». L'émergence et l'évolution de la pluripotence s'accompagnent notamment de changements dans la distribution de la méthylation de l'ADN et des modifications post-traductionnelles des histones. De précédents travaux avaient mis en évidence que le profil épigénétique de l’hétérochromatine péricentromérique permet de discriminer les cellules murines pluripotentes naïves et amorcées in vitro. Notamment, H3K27me3 est retrouvée aux chromocentres des mESCs naïves tandis qu'elle est absente des chromocentres des mEpiSCs amorcées. Ainsi, ce projet avait pour objectifs de (i) décrire le profil épigénétique des chromocentres au cours du développement précoce murin, (ii) identifier les acteurs qui participent à l’apposition de H3K27me3 aux chromocentres, et (iii) déterminer si ces mêmes caractéristiques épigénétiques sont conservées aux chromocentres du blastocyste bovin et/ou dans les ESCs bovines.Nous avons montré que, dans l’embryon murin, H3K27me3 s’accumule aux chromocentres dès leur formation au stade 2-cellules et y est maintenue au cours du développement pré-implantation. De façon intéressante, la distribution de H3K27me3 semble être liée à la maturation du lignage pluripotent puisque le profil de H3K27me3 change au moment de la ségrégation de l’épiblaste naïf par rapport à l'endoderme primitif. Dans l’embryon post-implantation, H3K27me3 n'est plus présente aux chromocentres quel que soit le lignage, y compris l’épiblaste pluripotent amorcé. Nous avons pu souligner des différences entre la situation in vivo – où le profil de H3K27me3 est homogène dans l’ensemble des cellules de l’épiblaste – et ce qui avait été décrit in vitro dans les mESCs. Enfin, il a été mis en évidence que la présence de H3K27me3 aux chromocentres n’est pas impliquée dans le contrôle transcriptionnel des séquences péricentromériques puisque leur transcription tend à diminuer au cours du développement, indépendamment de la présence de H3K27me3.Cette étude s’est également intéressée aux protéines EZH2 et BEND3, pour déterminer leurs implications respectives dans l’apposition de H3K27me3. Nous avons montré qu'EZH2 se localise en périphérie des chromocentres dès leur formation, conjointement à l’enrichissement progressif en H3K27me3 ; alors que BEND3 ne semble interagir avec les chromocentres qu’à partir du stade 8-cellules – suggérant que BEND3 n’est pas l’élément principal de recrutement d’EZH2 aux chromocentres dans l’embryon –. Ainsi, dans l’embryon pré-implantation et dans les mESCs non mutantes, la présence de BEND3 aux chromocentres n’est pas couplée à la présence de H3K27me3 – contrairement aux observations faites pour EZH2 dont le changement de distribution dans l’embryon précède le changement de localisation de H3K27me3 aux chromocentres –. A l’aide d’une approche par siRNA ciblant les transcrits EZH2 ou les transcrits BEND3, il a été mis en évidence que ni la forte diminution de BEND3, ni celle d‘EZH2, n’impactent la localisation de H3K27me3 aux chromocentres ou la transcription des séquences péricentromériques.Enfin, cette étude montre que H3K27me3 se localise en périphérie des chromocentres du blastocyste bovin. Cependant le profil de H3K27me3 ne semble pas évoluer avec la progression de l’état de pluripotence, contrairement à ce qui a été décrit pour le modèle murin. Ces résultats ont permis de mettre en évidence que la localisation de H3K27me3 au niveau des chromocentres semble être une caractéristique du développement embryonnaire précoce quel que soit l'espèce.Following fertilization, the embryonic genome undergoes various epigenetic and structural remodelings, essential for its activation. These various changes proceed further throughout development, as the embryo progresses from totipotency to pluripotency and differentiation. Pluripotency is a complex and transient state in which the cells that will later give rise to the future organism progress from a "naïve" to a "primed" state. The rise and progression of pluripotency is accompanied by changes in the distribution of DNA methylation and post-translational histones modifications. Previous work highlighted that the epigenetic profile of pericentromeric heterochromatin discriminates naive from primed murine pluripotent cells in vitro. Notably, H3K27me3, is found at the chromocenters of naive mESCs while this epigenetic mark is absent from the chromocenters of primed mEpiSCs. Thus, the objectives of this project were to (i) describe the epigenetic profile of chromocenters during early murine development, (ii) identify which actors are implied in the apposition of H3K27me3 to chromocenters, and (iii) determine whether these same epigenetic features are preserved at chromocenters of bovine blastocysts and/or in bovine ESCs.We showed that, in mouse embryo, H3K27me3 accumulates at the chromocenters from their formation at the 2-cell stage and is then maintained during pre-implantation development. Interestingly, the distribution of H3K27me3 seems to be related to the maturation of the pluripotent lineage since the profile of H3K27me3 changes upon segregation of the naive epiblast from the primitive endoderm. In the post-implantation embryo, H3K27me3 is not anymore at chromocenters whatever the lineages including the primed pluripotent epiblast. We were able to highlight important differences between the embryos in vivo - where the profile of H3K27me3 is homogeneous in all epiblast cells - and what was described in vitro in mESCs. Finally, we showed that the presence of H3K27me3 at chromocenters is not involved in the transcriptional control of pericentromeric sequences since their transcription tends to decrease during development, independently of the presence of H3K27me3.This study also focused on EZH2 and BEND3 proteins to assess their involvement in H3K27me3 apposition. We found that EZH2 localizes to the periphery of the chromocenters from their clustering, in conjunction with the progressive enrichment of H3K27me3; whereas BEND3 appears to interact with chromocenters only from the 8-cell stage onwards - suggesting that BEND3 is not the main driver of EZH2 recruitment to chromocenters in the embryo -. Similarly, in the pre-implantation embryo and in mESCs, the location of BEND3 at chromocenters does not correlate with the presence of H3K27me3 - in contrast to EZH2 whose change in distribution in the embryo precedes the change in localization of H3K27me3 at chromocenters -. Using a siRNA approach targeting either EZH2 or BEND3 transcripts, we showed that neither the strong reduction of BEND3, nor that of EZH2 influences the localization of H3K27me3 at chromocenters or the transcription of pericentromeric sequences.Finally, this study highlights that H3K27me3 is found at the chromocenters periphery in bovine blastocyst, although the profile of H3K27me3 at chromocenters seems not to evolve with the progression of pluripotency. These results highlighted similarities between species, where the localization of H3K27me3 at the chromocenters appears to be a feature of early embryonic development