La quadrature des agricultures familiales : instruire et dépasser les controverses

Cet article est la conclusion du dossier de la revue Tiers Monde (en 2 tomes, l'un paru en décembre 2014, l'autre en mars 2015) consacré aux Agricultures familiales, une thématique-clé de 2014, avec l’Année internationale de l’agriculture familiale.International audienceCet article est la conclusion du dossier de la revue Tiers Monde (en 2 tomes, l'un paru en décembre 2014, l'autre en mars 2015) consacré aux Agricultures familiales, une thématique-clé de 2014, avec l’Année internationale de l’agriculture familiale

Le front pionnier agro-désertique égyptien, par-delà rural et ruralité ?

Depuis le milieu du XXe siècle, les périphéries désertiques égyptiennes sont devenues le lieu de projection de l'avenir de l'agriculture nationale. Une véritable frontière agro-désertique a émergé, se déplaçant à des rythmes inégaux au cours des six dernières décennies. Cet article se propose d'éclairer la nature des nouveaux territoires agro-désertiques égyptiens et de comprendre en quoi ils interrogent les catégories de rural et de ruralité. La question du rapport au territoire de la nouvelle agriculture et de ses acteurs est posée, ceci depuis les parcelles de petits paysans au sein de villages créés ex-nihilo jusqu'aux exploitations agro-capitalistes contemporaines, parfois distantes de plusieurs centaines de kilomètres des principaux espaces de peuplement. Faut-il s'affranchir du concept de ruralité pour rendre compte des espaces du front pionnier égyptien ? Comment penser l'agricole sans rural et quelles catégories construire pour caractériser ces néo-territoires agro-désertiques ?Since the middle of the 20th century, desert margins have become the place where the future of the Egyptian agriculture is projected, both by the state and by international institutions. This article sheds light on the nature of the new agro-desert territories and shows how the frontier questions the very categories of rural and rurality. We discuss how this expanding agricultural sector and its diversity of stakeholders (from small peasants to large companies) are spatially embedded in desert areas. To what extent the analysis of the Egyptian agricultural frontier should go beyond the concept of rurality? What socio-spatial categories should be used and built to characterize the new territories

Entre delta du Nil et désert, front pionnier agricole et recomposition territoriale en Egypte

Territoires d'entre-deux, conquis sur le désert et situés au contact des espaces deltaïques, les terres nouvelles des marges du Delta du Nil sont emblématiques des modalités contemporaines d'extension du territoire utile égyptien. Longtemps confinés à la vallée, le peuplement et les activités économiques, notamment agricoles, tendent à conquérir les espaces désertiques environnants, encouragés par les différents gouvernements, surtout depuis les années 1950-60. Considérées comme un réservoir de potentialités, offrant à l'économie et à la population égyptiennes une échappatoire aux fortes densités, à l'extension urbaine et à la pollution caractéristiques de la vallée, les terres désertiques constituent de véritables laboratoires territoriaux à l'échelle nationale. En témoignent les marges occidentales du Delta, dont la conquête agricole s'est accélérée depuis le milieu des années 1980. Territoires soumis à de fortes contraintes, mais aussi lieux d'innovation et miroir des mutations de l'agriculture égyptienne, ces espaces situés en marge du Delta sont des territoires en construction, caractérisés par des modes de production et d'organisation territoriale nouveaux, mais aussi par une différenciation socio-économique très forte. Façonnés par des flux de diverses origines, ces espaces d'entre-deux témoignent d’une redéfinition des territoires ruraux égyptiens et d’une recomposition des relations entre acteurs, tant en termes d'inégalités, de conflits que de partenariats potentiels.Desert land reclamation for agricultural expansion has been used as a tool by the different political regimes since the 1950s to solve some of the sharpest problems in Egypt : the proclaimed lack of arable land in a context of fast population growth, the fragmentation of land in the Nile Valley and Delta, unemployment, rural poverty, and even the pollution of the old lands (Mitchell, 1995). Located between the fertile and populated areas of the Nile Delta and the vast areas of arid lands, new lands reclaimed on the desert have experienced a fast expansion of agricultural activities, with the emergence of an agri-capitalist sector, dominated by some large companies since the mid-1980s (Dixon, 2013). However, part of the new reclaimed lands have also been dedicated to the settlement of small-holders through governmental programmes. The purpose of this paper is to study the Western margins of the Nile Delta through the notion of “in-betweenness”. If the new lands are partly shaped by their interactions with the neighbouring territories, they are also characterized by specific internal dynamics, contributing to the emergence of a new agricultural sector and new Egyptian rural territories, as well as highlighting a process of socio-economic differentiation

Epithelial-mesenchymal transitions: the importance of changing cell state in development and disease

The events that convert adherent epithelial cells into individual migratory cells that can invade the extracellular matrix are known collectively as epithelial-mesenchymal transition (EMT). Throughout evolution, the capacity of cells to switch between these two cellular states has been fundamental in the generation of complex body patterns. Here, we review the EMT events that build the embryo and further discuss two prototypical processes governed by EMT in amniotes: gastrulation and neural crest formation. Cells undergo EMT to migrate and colonize distant territories. Not surprisingly, this is also the mechanism used by cancer cells to disperse throughout the body

The Oct4 homologue PouV and Nanog regulate pluripotency in chicken embryonic stem cells

International audienceEmbryonic stem cells ( ESC) have been isolated from pregastrulation mammalian embryos. The maintenance of their pluripotency and ability to self- renew has been shown to be governed by the transcription factors Oct4 ( Pou5f1) and Nanog. Oct4 appears to control cell- fate decisions of ESC in vitro and the choice between embryonic and trophectoderm cell fates in vivo. In nonmammalian vertebrates, the existence and functions of these factors are still under debate, although the identification of the zebrafish pou2 ( spg; pou5f1) and Xenopus Pou91 ( XlPou91) genes, which have important roles in maintaining uncommitted putative stem cell populations during early development, has suggested that these factors have common functions in all vertebrates. Using chicken ESC ( cESC), which display similar properties of pluripotency and long- term self- renewal to mammalian ESC, we demonstrated the existence of an avian homologue of Oct4 that we call chicken PouV ( cPouV). We established that cPouV and the chicken Nanog gene are required for the maintenance of pluripotency and self- renewal of cESC. These findings show that the mechanisms by which Oct4 and Nanog regulate pluripotency and self- renewal are not exclusive to mammal

A recording photoelastic stress meter

An instrument for automatically making photoelastic measurements of stress is described. It may be used for recording transient stresses at a point or for scanning spatial stress distributions. Its use is illustrated by an application entailing the measurement of transient thermal stresses in a viscoelastic material.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43936/1/11340_2006_Article_BF02327237.pd

Mathematical models of morphogen gradients and their effects on gene expression

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Identification of transcriptional regulatory variants in pig duodenum, liver, and muscle tissues

Background In humans and livestock species, genome-wide association studies (GWAS) have been applied to study the association between variants distributed across the genome and a phenotype of interest. To discover genetic polymorphisms affecting the duodenum, liver, and muscle transcriptomes of 300 pigs from 3 different breeds (Duroc, Landrace, and Large White), we performed expression GWAS between 25,315,878 polymorphisms and the expression of 13,891 genes in duodenum, 12,748 genes in liver, and 11,617 genes in muscle. Results More than 9.68 × 1011 association tests were performed, yielding 14,096,080 significantly associated variants, which were grouped in 26,414 expression quantitative trait locus (eQTL) regions. Over 56% of the variants were within 1 Mb of their associated gene. In addition to the 100-kb region upstream of the transcription start site, we identified the importance of the 100-kb region downstream of the 3′UTR for gene regulation, as most of the cis-regulatory variants were located within these 2 regions. We also observed 39,874 hotspot regulatory polymorphisms associated with the expression of 10 or more genes that could modify the protein structure or the expression of a regulator gene. In addition, 2 motifs (5′-GATCCNGYGTTGCYG-3′ and a poly(A) sequence) were enriched across the 3 tissues within the neighboring sequences of the most significant single-nucleotide polymorphisms in each cis-eQTL region. Conclusions The 14 million significant associations obtained in this study are publicly available and have enabled the identification of expression-associated cis-, trans-, and hotspot regulatory variants within and across tissues, thus shedding light on the molecular mechanisms of regulatory variations that shape end-trait phenotypes.info:eu-repo/semantics/publishedVersio

Characterization of 3D genomic interactions in fetal pig muscle

Genome sequence alone is not sufficient to explain the overall coordination of nuclear activity in a particular tissue. The nuclear organisation and genomic long-range intra- and inter-chromosomal interactions play an important role in the regulation of gene expression and the activation of tissue- specific gene networks. Here we present an overview of the pig genome architecture in muscle at two late developmental stages. The muscle maturation process occurs between the 90th day and the end of gestation (114 days), a key period for survival at birth. To characterise this period we profiled chromatin interactions genome-wide with in situ Hi-C (High Throughput Chromosome Conformation Capture) in muscle samples collected at 90 and 110 days of gestation, specific moments where a drastic change in gene expression has been reported. About 200 million read pairs per library were generated (3 replicates per condition). This allowed: (a) the design of an experimental Hi-C protocol optimized for frozen fetal tissues, (b) the first Hi-C contact heatmaps in fetal porcine muscle cells, and (c) to profile Topologically Associated Domains (TADs) defined as genomic domains with high levels of chromatin interactions. Using the new assembly version Sus scrofa v11, we could map 82% of the Hi-C reads on the reference genome. After filtering, 49% of valid read pairs were used to infer the genomic interactions in both developmental stages. In addition, ChIP-seq experiments were performed to map the binding of the structural protein CTCF, known to regulate genome structure by promoting interactions between genes and distal enhancers. The Hi-C and ChIP-seq data were analysed in combination with the results of a previous transcriptome analysis, focusing on the hun-dreds of genes that were reported as differentially expressed during muscle maturation. We will report the observed general differences between both developmental stages in terms of transcription and structure

The endogenous retrovirus ENS-1 provides active binding sites for transcription factors in embryonic stem cells that specify extra embryonic tissue

<p>Abstract</p> <p>Background</p> <p>Long terminal repeats (LTR) from endogenous retroviruses (ERV) are source of binding sites for transcription factors which affect the host regulatory networks in different cell types, including pluripotent cells. The embryonic epiblast is made of pluripotent cells that are subjected to opposite transcriptional regulatory networks to give rise to distinct embryonic and extraembryonic lineages. To assess the transcriptional contribution of ERV to early developmental processes, we have characterized <it>in vitro </it>and <it>in vivo </it>the regulation of ENS-1, a host adopted and developmentally regulated ERV that is expressed in chick embryonic stem cells.</p> <p>Results</p> <p>We show that <it>Ens-1 </it>LTR activity is controlled by two transcriptional pathways that drive pluripotent cells to alternative developmental fates. Indeed, both Nanog that maintains pluripotency and Gata4 that induces differentiation toward extraembryonic endoderm independently activate the LTR. Ets coactivators are required to support Gata factors' activity thus preventing inappropriate activation before epigenetic silencing occurs during differentiation. Consistent with their expression patterns during chick embryonic development, Gata4, Nanog and Ets1 are recruited on the LTR in embryonic stem cells; in the epiblast the complementary expression of Nanog and Gata/Ets correlates with the <it>Ens-1 </it>gene expression pattern; and Ens-1 transcripts are also detected in the hypoblast, an extraembryonic tissue expressing Gata4 and Ets2, but not Nanog. Accordingly, over expression of Gata4 in embryos induces an ectopic expression of <it>Ens-1</it>.</p> <p>Conclusion</p> <p>Our results show that <it>Ens-1 </it>LTR have co-opted conditions required for the emergence of extraembryonic tissues from pluripotent epiblasts cells. By providing pluripotent cells with intact binding sites for Gata, Nanog, or both, <it>Ens-1 </it>LTR may promote distinct transcriptional networks in embryonic stem cells subpopulations and prime the separation between embryonic and extraembryonic fates.</p