Le rôle des collectivités territoriales dans l’adaptation des enjeux environnementaux globaux à l’échelle locale

Les enjeux environnementaux tels qu’ils sont définis par les politiques publiques aboutissent à des aménagements dans l’espace rural, confrontant les sociétés locales à une transformation de leur environnement immédiat. L’objectif de cet article est de montrer le processus par lequel les enjeux globaux, tels que la lutte contre le changement climatique et la protection de la biodiversité, sont convertis à une échelle locale à travers l’action des structures politiques locales (municipalité, communauté de communes, etc.). La réception de ces aménagements, déterminant leur nature, est liée à deux facteurs principaux : la structure de la société locale et le degré d’adaptabilité du projet en fonction des objectifs attribués au débat public.Cette communication repose sur un travail de terrain où différents aménagements ont été comparés (deux parcs éoliens et deux itinéraires pédestres). Dans tous les cas, il a été observé que le débat public a été organisé par les structures politiques locales pour adapter les dispositifs en fonction de la stratification de la société locale et des enjeux du pouvoir local.Environmental stakes, as defined by public policies, result in developments in rural space, confronting local societies to transformations of their close environment. The article aims at explaining the process through which global stakes, such as the struggle against climatic change and the protection of biodiversity, are converted into local stakes through the action of local political structures. Two main factors determine the perception of these stakes by the population : the structure of local societies, and the degree of adaptability of these developments.The communication is based on the comparison of different developments (two Aeolian parks and two pedestrian paths). In all cases, the public debate has been organised by local political structures to adapt the developments to the stratification of local societies and to the local power stakes

A proteção da floresta amazônica: políticas de Estado, percepção dos atores e gestão dos espaços locais

Analisar como as políticas públicas socioambientais dirigidas à região amazônica são percebidas pela população local e quais tipos de resultados têm sido produzidos na gestão do território local são as problemáticas orientadoras de nossas reflexões. O primeiro aspecto a ser analisado é a noção de sustentabilidade do meio ambiente, difundida especialmente pelos segmentos ambientalistas e os atores governamentais que realizam as políticas ambientais, procurando ressaltar a relação com a idéia de desenvolvimento sustentável como uma categoria de discurso ou uma categoria de análise. O segundo grupo de reflexões abordará a durabilidade pela conversão, explorando a participação de atores como a Prefeitura de Parauapebas, a repetidora local da televisão (TV Liberal) e a Emater. Atores que constituem parte de uma rede de relações da Cooperativa Mista dos Produtores Rurais da Região de Carajás – COOPER. As ponderações finais trazem à tona a compreensão do importante papel que estes atores têm e ressalta ainda o vínculo bastante forte com modelos vindos do exterior por meio de financiamentos e da presença de atores exteriores. Ao mesmo tempo, procura-se verificar como a gestão dos espaços locais se beneficiam (ou se ressentem) das idéias recebidas. A análise enfoca o vínculo entre os diferentes parceiros – a Prefeitura, os agricultores, por meio da COOPER, os Ministérios da Agricultura e o de Meio Ambiente e, por seu intermédio, o G8 e a União Européia

La durabilité des exploitations laitières : rôle du territoire dans leur fonctionnement en Ille-et-Vilaine

L'objectif de cet article est de montrer comment le territoire interfère dans la conduite des élevages laitiers. Le territoire est considéré comme un ensemble de ressources mobilisées à travers les réseaux de relation tissés par chaque exploitant. Dans cette perspective, les différents types d'élevage traduisent l'existence de différentes formes de construction des ressources territoriales. Pour montrer cela, dans une première étape, quatre types d'élevage ont été identifiés à partir d'une enquête sur des élevages laitiers. Puis, les formes de construction des ressources ont été analysées pour chaque modèle. Il ressort de cette approche que les ressources territoriales d'un élevage varient dans l'espace en fonction de son degré d'intensification et du modèle professionnel adopté par l'exploitant, faisant reposer la durabilité de la production sur des dynamiques différentes

La fabrication des paysages par les éleveurs laitiers : le cas de l'Ille-et-Vilaine

Les paysages agricoles sont analysés à partir de leur perception et de leur construction par les agriculteurs. Ils ont été envisagés comme des cadres de vie, résultant de dynamiques naturelles et de pratiques humaines. La variabilité des comportements paysagers des agriculteurs a été analysée en fonction du modèle de développement agricole adopté par l'exploitant, des caractéristiques de son système d'élevage, et cela, à l'échelle de l'exploitation. Les données ont été recueillies lors d'entretiens semi-directifs auprès d'un échantillon de 54 élevages laitiers d'Ille-et-Vilaine qui se sont déroulés en 2007 et 2009. Deux types de relation aux paysages agricoles ont été dégagés en fonction, principalement, du modèle de production adopté par l'éleveur. Le premier correspond aux éleveurs adhérant à un modèle " production " plus intensif pour lesquels la notion de paysage agricole renvoie avant tout aux contraintes productives de l'élevage et des parcelles agricoles. Pour les agriculteurs qui développent un modèle plus autonome, même si le paysage agricole est avant tout défini à partir des contraintes productives, d'autres ordres de contraintes sont davantage pris en compte comme les aspects esthétiques

The yeast ribosome synthesis factor Emg1 is a novel member of the superfamily of alpha/beta knot fold methyltransferases

Emg1 was previously shown to be required for maturation of the 18S rRNA and biogenesis of the 40S ribosomal subunit. Here we report the determination of the crystal structure of Emg1 at 2 Å resolution in complex with the methyl donor, S-adenosyl-methionine (SAM). This structure identifies Emg1 as a novel member of the alpha/beta knot fold methyltransferase (SPOUT) superfamily. In addition to the conserved SPOUT core, Emg1 has two unique domains that form an extended surface, which we predict to be involved in binding of RNA substrates. A point mutation within a basic patch on this surface almost completely abolished RNA binding in vitro. Three point mutations designed to disrupt the interaction of Emg1 with SAM each caused>100-fold reduction in SAM binding in vitro. Expression of only Emg1 with these mutations could support growth and apparently normal ribosome biogenesis in strains genetically depleted of Emg1. We conclude that the catalytic activity of Emg1 is not essential and that the presence of the protein is both necessary and sufficient for ribosome biogenesis

La COOPER, son pari sur la fruiticulture et le commerce solidaire pour une agriculture familiale plus durable...

La COOPER (coopérative mixte des producteurs ruraux de Carajás) commercialise des pulpes de fruits congelées produites par de petits agriculteurs. Elle est née de la rencontre de trois associations à la recherche de débouchés pour leurs productions fruitières. Elle est aujourd'hui un acteur important de sa région d'origine

Structural investigations of the regio- and enantioselectivity of lipases

Although lipases are widely applied for the stereospecific resolution of racemic mixtures of esters, the atomic details of the factors that are responsible for their stereospecificity are largely obscure. We determined the X-ray structures of Pseudomonas cepacia lipase in complex with two enantiopure triglyceride analogues, that closely mimic natural substrates. This allowed an unambiguous view of how the two wings of the boomerang-shaped active site accommodate the acyl and alcohol parts of the triglyceride. The binding groove for the hydrophobic sn-3 fatty acid chain is large and hydrophobic. The cleft for the alcohol moiety is divided in two parts, one tightly binding the sn-2 acyl chain with hydrophilic and hydrophobic interactions, the other more weakly binding the sn-1 fatty acid. The enantioselectivity of Pseudomonas cepacia lipase seems therefore to be predominantly determined by the size and interactions of the sn-2 chain and by the size of the sn-3 chain.

Molecular determinants of the DprA−RecA interaction for nucleation on ssDNA

International audienceNatural transformation is a major mechanism of horizontal gene transfer in bacteria that depends on DNA recombination. RecA is central to the homologous recombination pathway, catalyzing DNA strand invasion and homology search. DprA was shown to be a key binding partner of RecA acting as a specific mediator for its loading on the incoming exogenous ssDNA. Although the 3D structures of both RecA and DprA have been solved, the mechanisms underlying their cross-talk remained elusive. By combining molecular docking simulations and experimental validation, we identified a region on RecA, buried at its self-assembly interface and involving three basic residues that contact an acidic triad of DprA previously shown to be crucial for the interaction. At the core of these patches, DprA M238 and RecA F230 are involved in the interaction. The other DprA binding regions of RecA could involve the N-terminal ␣-helix and a DNA-binding region. Our data favor a model of DprA acting as a cap of the RecA filament, involving a DprA−RecA interplay at two levels: their own oligomeric states and their respective interaction with DNA. Our model forms the basis for a mech-anistic explanation of how DprA can act as a mediator for the loading of RecA on ssDNA

Crystal structures of the Gon7/Pcc1 and Bud32/Cgi121 complexes provide a model for the complete yeast KEOPS complex.

International audienceThe yeast KEOPS protein complex comprising Kae1, Bud32, Cgi121, Pcc1 and Gon7 is responsible for the essential tRNA threonylcarbamoyladenosine (t(6)A) modification. Deletion of genes coding for the KEOPS subunits also affects telomere elongation and transcriptional regulation. In the present work, the crystal structure of Bud32/Cgi121 in complex with ADP revealed that ADP is bound in the catalytic site of Bud32 in a canonical manner characteristic of Protein Kinase A (PKA) family proteins. We found that Gon7 forms a stable heterodimer with Pcc1 and report the crystal structure of the Pcc1-Gon7 heterodimer. Gon7 interacts with the same Pcc1 region engaged in the archaeal Pcc1 homodimer. We further show that yeast KEOPS, unlike its archaeal counterpart, exists as a heteropentamer in which Gon7, Pcc1, Kae1, Bud32 and Cgi121 also adopt a linear arrangement. We constructed a model of yeast KEOPS that provides structural insight into the role of Gon7. The model also revealed the presence of a highly positively charged crater surrounding the entrance of Kae1 that likely binds tRNA

The crystal structure of Trz1, the long form RNase Z from yeast.

tRNAs are synthesized as precursor RNAs that have to undergo processing steps to become functional. Yeast Trz1 is a key endoribonuclease involved in the 3΄ maturation of tRNAs in all domains of life. It is a member of the β-lactamase family of RNases, characterized by an HxHxDH sequence motif involved in coordination of catalytic Zn-ions. The RNase Z family consists of two subfamilies: the short (250-400 residues) and the long forms (about double in size). Short form RNase Z enzymes act as homodimers: one subunit embraces tRNA with a protruding arm, while the other provides the catalytic site. The long form is thought to contain two fused β-lactamase domains within a single polypeptide. Only structures of short form RNase Z enzymes are known. Here we present the 3.1 Å crystal structure of the long-form Trz1 from Saccharomyces cerevisiae. Trz1 is organized into two β-lactamase domains connected by a long linker. The N-terminal domain has lost its catalytic residues, but retains the long flexible arm that is important for tRNA binding, while it is the other way around in the C-terminal domain. Trz1 likely evolved from a duplication and fusion of the gene encoding the monomeric short form RNase Z