French Roadmap for complex Systems 2008-2009

This second issue of the French Complex Systems Roadmap is the outcome of the Entretiens de Cargese 2008, an interdisciplinary brainstorming session organized over one week in 2008, jointly by RNSC, ISC-PIF and IXXI. It capitalizes on the first roadmap and gathers contributions of more than 70 scientists from major French institutions. The aim of this roadmap is to foster the coordination of the complex systems community on focused topics and questions, as well as to present contributions and challenges in the complex systems sciences and complexity science to the public, political and industrial spheres

Etude de la regulation de l'expression des genes de la voie de biosynthese de l'auxine d'Agrobacterium rhizogenes

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 82107 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Epigenetic control by plant polycomb proteins: new perspectives and emerging roles in stress response

In eukaryotes, cell-fate determination, differentiation and developmental programs require precise spatial and temporal control of gene expression. Polycomb group (PcG) proteins are key transcriptional regulators in these mechanisms. Research over the past decade has demonstrated the significance of the Polycomb system in establishing silent chromatin states and perpetuating them through cell divisions. PcG-mediated gene silencing is a fundamental and conserved mechanism employed by both plants and animals. In plants these proteins maintain cell identity and imprinting and control important developmental transitions, hence having agronomical impacts.In this chapter, we discuss the impact of Polycomb regulation in controlling epigenetic states in plants. We highlight recent reports on the role of long non-coding RNAs as PcG cofactors and the involvement of PcG complexes in stress responses. Indeed, how plants respond to environmental stresses by modifying expression of the genome is a challenge in plant biology, and unexplored links between stress response and PcG regulation are promising

Génétique moléculaire des plantes

National audienc

A reporter gene under the control of tms or aux promoters is differentially expressed in tobacco and barley protoplasts

International audienc

Green chromatin dynamics in Zurich: meeting summary based on the European Workshop on Plant Chromatin 2009 in Zurich, Switzerland

International audienceIn September 2009, the 1(st) European Workshop on Plant Chromatin took place in Zurich, Switzerland. The workshop covered a variety of chromatin related topics, including the mechanisms of Polycomb group protein function, long-range interactions of regulatory elements, genome-wide reconfiguration of epigenetic marks during gametogenesis and protection of chromosomal ends by epigenetic marks. Some of the highlights of this meeting are summarized in this report

Green chromatin dynamics in Zurich: meeting summary based on the European Workshop on Plant Chromatin 2009 in Zurich, Switzerland

International audienceIn September 2009, the 1(st) European Workshop on Plant Chromatin took place in Zurich, Switzerland. The workshop covered a variety of chromatin related topics, including the mechanisms of Polycomb group protein function, long-range interactions of regulatory elements, genome-wide reconfiguration of epigenetic marks during gametogenesis and protection of chromosomal ends by epigenetic marks. Some of the highlights of this meeting are summarized in this report

Diversification of photoperiodic response patterns in a collection of early-flowering mutants of arabidopsis

Many plant species exhibit seasonal variation of flowering time in response to daylength. Arabidopsis (Arabidopsis thaliana) flowers earlier under long days (LDs) than under short days (SDs). This quantitative response to photoperiod is characterized by two parameters, the critical photoperiod (Pc), below which there is a delay in flowering, and the ceiling photoperiod (Pce), below which there is no further delay. Thus Pc and Pce define the thresholds beyond which maximum LD and SD responses are observed, respectively. We studied the quantitative response to photoperiod in 49 mutants selected for early flowering in SDs. Nine of these mutants exhibited normal Pce and Pc, showing that their precocious phenotype was not linked to abnormal measurement of daylength. However, we observed broad diversification in the patterns of quantitative responses in the other mutants. To identify factors involved in abnormal measurement of daylength, we analyzed the association of these various patterns with morphogenetic and rhythmic defects. A high proportion of mutants with altered Pce exhibited abnormal hypocotyl elongation in the dark and altered circadian periods of leaf movements. This suggested that the circadian clock and negative regulators of photomorphogenesis may contribute to the specification of SD responses. In contrast, altered Pc correlated with abnormal hypocotyl elongation in the light and reduced photosynthetic light-input requirements for bolting. This indicated that LD responses may be specified by positive elements of light signal transduction pathways and by regulators of resource allocation. Furthermore, the frequency of circadian defects in mutants with normal photoperiodic responses suggested that the circadian clock may regulate the number of leaves independently of its effect on daylength perception

Identification and expression of two oxytocin/vasopressin-related peptides in the cuttlefish Sepia officinalis

International audienceTwo novel members of the oxytocin/vasopressin superfamily have been identified in the cephalopod Sepia officinalis. Oxytocin/vasopressin gene sequences were cloned by Race PCR. The two precursors we identified exhibit the classical organization of OT/VP superfamily precursors: a signal peptide followed by a nonapeptide and a neurophysin domain. The neurophysin domain is entirely conserved for the cuttlefish precursors, but the nonapeptides and the signal peptides differ. The first nonapeptide, called sepiatocin, is highly homologous to Octopus vulgaris octopressin. The second nonapeptide, called pro-sepiatocin, shows sequence homologies with a Crustacean oxytocin/vasopressin-like peptide identified in Daphnia culex and with a novel form of oxytocin described in New World monkeys. The expression of pro-sepiatocin is restricted to the supraesophageal and subesophageal masses of the brain whereas sepiatocin is expressed in the entire central nervous system. Sepiatocin, as described for octopressin, modulates the contractile activity of several muscles such as penis, oviduct and vena cava muscles; this suggests its involvement in reproduction and blood circulation. Pro-sepiatocin is released in the hemolymph; it is a neurohormone able to target numerous peripheral organs

Architecture nucléaire : modélisation spatiale et application à la compréhension des mécanismes de différenciation

National audienc