Institute Jean Pierre Bourgin

Versailles, France

Institute Jean Pierre Bourgin

Versailles, France
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Pribat A.,University of Bordeaux 1 | Sormani R.,University of Bordeaux 1 | Sormani R.,Institute Jean Pierre Bourgin | Rousseau-Gueutin M.,University of Bordeaux 1 | And 9 more authors.
Biochemical Journal | Year: 2012

PTEN (phosphatase and tensin homologue deleted on chromosome ten) proteins are dual phosphatases with both protein and phosphoinositide phosphatase activity. Theymodulate signalling pathways controlling growth, metabolism and apoptosis in animals and are implied in several human diseases. In the present paper we describe a novel class of PTEN proteins in plants, termed PTEN2, which comprises the AtPTEN (Arabidopsis PTEN) 2a and AtPTEN2b proteins in Arabidopsis. Both display low in vitro tyrosine phosphatase activity. In addition, AtPTEN2a actively dephosphorylates in vitro the 3′phosphate group of PI3P (phosphatidylinositol 3-phosphate), PI(3,4)P 2 (phosphatidylinositol 3,4-bisphosphate) and PI(3,5)P 2(phosphatidylinositol 3,5-bisphosphate). In contrast with animal PTENs, PI(3,4,5)P 3 (phosphatidylinositol 3,4,5-trisphosphate) is a poor substrate. Site-directed mutagenesis of AtPTEN2a and molecular modelling of protein-phosphoinositide interactions indicated that substitutions at the PTEN2 core catalytic site of the Lys 267 and Gly 268 residues found in animals, which are critical for animal PTENactivity, by Met 267 and Ala 268 found in the eudicot PTEN2 are responsible for changes in substrate specificity. Remarkably, the AtPTEN2a protein also displays strong binding activity for PA (phosphatidic acid), a major lipid second messenger in plants. Promoter::GUS (β-glucuronidase) fusion, transcript and protein analyses further showed the transcriptional regulation of the ubiquitously expressed AtPTEN2a and AtPTEN2b by salt and osmotic stress. The results of the present study suggest a function for this novel class of plant PTEN proteins as an effector of lipid signalling in plants. ©The Authors Journal compilation © 2012 Biochemical Society.

Dobler R.,University of Tübingen | Rogell B.,Monash University | Budar F.,French National Institute for Agricultural Research | Budar F.,Institute Jean Pierre Bourgin | Dowling D.K.,Monash University
Journal of Evolutionary Biology | Year: 2014

Genetic variation in cytoplasmic genomes (i.e. the mitochondrial genome in animals, and the combined mitochondrial and chloroplast genomes in plants) was traditionally assumed to accumulate under a neutral equilibrium model. This view has, however, come under increasing challenge from studies that have experimentally linked cytoplasmic genetic effects to the expression of life history phenotypes. Such results suggest that genetic variance located within the cytoplasm might be of evolutionary importance and potentially involved in shaping population evolutionary trajectories. As a step towards assessing this assertion, here we conduct a formal meta-analytic review to quantitatively assess the extent to which cytoplasmic genetic effects contribute to phenotypic expression across animal and plant kingdoms. We report that cytoplasmic effect sizes are generally moderate in size and associated with variation across a range of factors. Specifically, cytoplasmic effects on morphological traits are generally larger than those on life history or metabolic traits. Cytoplasmic effect sizes estimated at the between-species scale (via interspecies mix-and-matching of cytoplasmic and nuclear genomes) are larger than those at the within-species scale. Furthermore, cytoplasmic effects tied to epistatic interactions with the nuclear genome tend to be stronger than additive cytoplasmic effects, at least when restricting the data set to gonochorous animal species. Our results thus confirm that cytoplasmic genetic variation is commonly tied to phenotypic expression across plants and animals, implicate the cytoplasmic-nuclear interaction as a key unit on which natural selection acts and generally suggest that the genetic variation that lies within the cytoplasm is likely to be entwined in adaptive evolutionary processes. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

Haigler C.H.,North Carolina State University | Grimson M.J.,Texas Tech University | Grimson M.J.,W L Gore and Associates | Gervais J.,MINES ParisTech | And 5 more authors.
PLoS ONE | Year: 2014

The remarkable mechanical strength of cellulose reflects the arrangement of multiple b-1,4-linked glucan chains in a paracrystalline fibril. During plant cellulose biosynthesis, a multimeric cellulose synthesis complex (CSC) moves within the plane of the plasma membrane as many glucan chains are synthesized from the same end and in close proximity. Many questions remain about the mechanism of cellulose fibril assembly, for example must multiple catalytic subunits within one CSC polymerize cellulose at the same rate? How does the cellulose fibril bend to align horizontally with the cell wall? Here we used mathematical modeling to investigate the interactions between glucan chains immediately after extrusion on the plasma membrane surface. Molecular dynamics simulations on groups of six glucans, each originating from a position approximating its extrusion site, revealed initial formation of an uncrystallized aggregate of chains from which a protofibril arose spontaneously through a ratchet mechanism involving hydrogen bonds and van der Waals interactions between glucose monomers. Consistent with the predictions from the model, freeze-fracture transmission electron microscopy using improved methods revealed a hemispherical accumulation of material at points of origination of apparent cellulose fibrils on the external surface of the plasma membrane where rosette-type CSCs were also observed. Together the data support the possibility that a zone of uncrystallized chains on the plasma membrane surface buffers the predicted variable rates of cellulose polymerization from multiple catalytic subunits within the CSC and acts as a flexible hinge allowing the horizontal alignment of the crystalline cellulose fibrils relative to the cell wall. © 2014 Haigler et al.

Massonnet C.,Montpellier SupAgro | Massonnet C.,University of Lorraine | Tisne S.,Montpellier SupAgro | Tisne S.,Institute Jean Pierre Bourgin | And 7 more authors.
Plant Physiology | Year: 2011

Enormous progress has been achieved understanding the molecular mechanisms regulating endoreduplication. By contrast, how this process is coordinated with the cell cycle or cell expansion and contributes to overall growth in multicellular systems remains unclear. A holistic approach was used here to give insight into the functional links between endoreduplication, cell division, cell expansion, and whole growth in the Arabidopsis (Arabidopsis thaliana) leaf. Correlative analyses, quantitative genetics, and structural equation modeling were applied to a large data set issued from the multiscale phenotyping of 200 genotypes, including both genetically modified lines and recombinant inbred lines. All results support the conclusion that endoreduplication in leaf cells could be controlled by leaf growth itself. More generally, leaf growth could act as a "hub" that drives cell division, cell expansion, and endoreduplication in parallel. In many cases, this strategy allows compensations that stabilize leaf area even when one of the underlying cellular processes is limiting. © 2011 American Society of Plant Biologists. All Rights Reserved.

Aubert A.,French National Center for Scientific Research | Marion J.,French National Center for Scientific Research | Boulogne C.,French National Center for Scientific Research | Bourge M.,French National Center for Scientific Research | And 4 more authors.
Plant Journal | Year: 2011

Sphingolipids play an essential role in the functioning of the secretory pathway in eukaryotic organisms. Their importance in the functional organization of plant cells has not been studied in any detail before. The sphingolipid synthesis inhibitor fumonisin B1 (FB1), a mycotoxin acting as a specific inhibitor of ceramide synthase, was tested for its effects on cell growth, cell polarity, cell shape, cell cycle and on the ultrastructure of BY2 cells. We used cell lines expressing different GFP-tagged markers for plant cell compartments, as well as a Golgi marker fused to the photoconvertible protein Kaede. Light and electron microscopy, combined with flow cytometry, were applied to analyse the morphodynamics and architecture of compartments of the secretory pathway. The results indicate that FB1 treatment had severe effects on cell growth and cell shape, and induced a delay in cell division processes. The cell changes were accompanied by the formation of the endoplasmic reticulum (ER)-derived tubular aggregates (FB1-induced compartments), together with an inhibition of cargo transport from the ER to the Golgi apparatus. A change in polar localization of the auxin transporter PIN1 was also observed, but endocytic processes were little affected. Electron microscopy studies confirmed that molecular FB1 targets were distinct from brefeldin A (BFA) targets. We propose that the reported effects of inhibition of ceramide biosynthesis reflect the importance of sphingolipids during cell growth and establishment of cell polarity in higher plant cells, notably through their contribution to the functional organization of the ER or its differentiation into distinct compartments. © 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd.

Schaefer D.G.,Institute Jean Pierre Bourgin | Schaefer D.G.,University of Neuchatel | Delacote F.,Institute Jean Pierre Bourgin | Delacote F.,French National Center for Scientific Research | And 7 more authors.
DNA Repair | Year: 2010

Gene targeting (GT) is a major tool for basic and applied research during which the transforming DNA, which shares sequence homology with a chromosomal target, integrates at the corresponding locus by homologous recombination (HR). In eukaryotes, GT recruits enzymes from the HR-mediated double strand break repair pathway. Different mechanisms of HR have been described which depend on the Rad52 epistasis group of genes, but which specific mechanism is used by the cell for GT remains unclear. In Saccharomyces cerevisiae, the RAD52 protein is essential for GT, and the RAD51 protein plays a minor role. In filamentous fungi and animal cells, however, GT depends on RAD51 and is weakly affected by suppression of RAD52. Genetic evidence also indicates that the non-homologous end-joining pathway of DSB repair has a negative impact on GT efficiencies, but how the balance between these two pathways is controlled is poorly understood. Here, we have examined the role of RAD51 in the only plant that exhibits high GT frequencies, the model bryophyte Physcomitrella patens. Our results show that the two RAD51 proteins have partially redundant functions in the maintenance of genome integrity and resistance to ionizing radiation. Furthermore, we demonstrate that loss of function of the two RAD51 proteins completely abolishes GT and strongly increases illegitimate integration rates in this moss. These findings demonstrate for the first time in plant the critical role of RAD51 in controlling the balance between targeted and random integration events observed upon transgenesis, and confirm that P. patens is a particularly interesting tool for studying GT in higher eukaryotes. © 2010 Elsevier B.V. All rights reserved.

Frey A.,Institute Jean Pierre Bourgin | Effroy D.,Institute Jean Pierre Bourgin | Lefebvre V.,Institute Jean Pierre Bourgin | Lefebvre V.,University of Picardie Jules Verne | And 7 more authors.
Plant Journal | Year: 2012

Carotenoid cleavage, catalyzed by the 9-cis-epoxycarotenoid dioxygenase (NCED) constitutes a key step in the regulation of ABA biosynthesis. In Arabidopsis, this enzyme is encoded by five genes. NCED3 has been shown to play a major role in the regulation of ABA synthesis in response to water deficit, whereas NCED6 and NCED9 have been shown to be essential for the ABA production in the embryo and endosperm that imposes dormancy. Reporter gene analysis was carried out to determine the spatiotemporal pattern of NCED5 and NCED9 gene expression. GUS activity from the NCED5 promoter was detected in both the embryo and endosperm of developing seeds with maximal staining after mid-development. NCED9 expression was found at early stages in the testa outer integument layer 1, and after mid-development in epidermal cells of the embryo, but not in the endosperm. In accordance with its temporal- and tissue-specific expression, the phenotypic analysis of nced5 nced6 nced9 triple mutant showed the involvement of the NCED5 gene, together with NCED6 and NCED9, in the induction of seed dormancy. In contrast to nced6 and nced9, however, nced5 mutation did not affect the gibberellin required for germination. In vegetative tissues, combining nced5 and nced3 mutations reduced vegetative growth, increased water loss upon dehydration, and decreased ABA levels under both normal and stressed conditions, as compared with nced3. NCED5 thus contributes, together with NCED3, to ABA production affecting plant growth and water stress tolerance. © 2011 Blackwell Publishing Ltd.

Silveira A.B.,University of Campinas | Trontin C.,Institute Jean Pierre Bourgin | Cortijo S.,French Institute of Health and Medical Research | Barau J.,University of Campinas | And 4 more authors.
PLoS Genetics | Year: 2013

Epigenetic variation, such as heritable changes of DNA methylation, can affect gene expression and thus phenotypes, but examples of natural epimutations are few and little is known about their stability and frequency in nature. Here, we report that the gene Qua-Quine Starch (QQS) of Arabidopsis thaliana, which is involved in starch metabolism and that originated de novo recently, is subject to frequent epigenetic variation in nature. Specifically, we show that expression of this gene varies considerably among natural accessions as well as within populations directly sampled from the wild, and we demonstrate that this variation correlates negatively with the DNA methylation level of repeated sequences located within the 5′end of the gene. Furthermore, we provide extensive evidence that DNA methylation and expression variants can be inherited for several generations and are not linked to DNA sequence changes. Taken together, these observations provide a first indication that de novo originated genes might be particularly prone to epigenetic variation in their initial stages of formation. © 2013 Silveira et al.

Cifuentes M.,Institute Jean Pierre Bourgin | Garcia-Aguero V.,Technical University of Madrid | Benavente E.,Technical University of Madrid
Cytogenetic and Genome Research | Year: 2010

Homoeologous metaphase I (MI) associations in hybrids between durum wheat and its wild allotetraploid relatives Aegilops neglecta, Ae. triuncialis and Ae. ventricosa have been characterized by a genomic in situ hybridization procedure that allows simultaneous discrimination of A, B and wild species genomes. Earlier results in equivalent hybrids with the wild species Ae. cylindrica and Ae. geniculata have also been considered to comparatively assay the MI pairing pattern of the durum wheat × Aegilops interspecific combinations more likely to occur in nature. The general picture can be drawn as follows. A and B wheat genomes pair with each other less than the 2 wild constituent genomes do in any of the hybrid combinations examined. Interspecific wheat-wild associations account for 60-70% of total MI pairing in all hybrids, except in that derived from Ae. triuncialis, but the A genome is always the wheat partner most frequently involved in MI pairing with the wild homoeologues. Hybrids with Ae. cylindrica, Ae. geniculata and Ae. ventricosa showed similar reduced levels of MI association and virtually identical MI pairing patterns. However, certain recurrent differences were found when the pattern of homoeologous pairing of hybrids from either Ae. triuncialis or Ae. neglecta was contrasted to that observed in the other durum wheat hybrid combinations. In the former case, a remarkable preferential pairing between the wild species constituent genomes Ut and Ct seems to be the reason, whereas a general promotion of homoeologous pairing, qualitatively similar to that observed under the effect of the ph1c mutation, appears to occur in the hybrid with Ae. neglecta. It is further discussed whether the results reported here can be extrapolated to the corresponding bread wheat hybrid combinations. Copyright © 2010 S. Karger AG, Basel.

Chardon F.,Institute Jean Pierre Bourgin | Barthelemy J.,Institute Jean Pierre Bourgin | Daniel-Vedele F.,Institute Jean Pierre Bourgin | Masclaux-Daubresse C.,Institute Jean Pierre Bourgin
Journal of Experimental Botany | Year: 2010

Eighteen accessions of Arabidopsis thaliana were grown with low (N-) and high (N+) nitrogen supply. N uptake was monitored by feeding plants with 15N-enriched nutritive solution over 24h. Biomass [fresh matter (FM) and dry matter (DM)], N concentration (N%), and 15N content were monitored and computed to determine the nitrogen use efficiency (NUE) and nitrogen uptake efficiency (NupE). NUE has been estimated as the ratio between biomass and N concentration (DM/N%) and NupE as the concentration of 15N in plants [μg (g-1 DM)]. Accession traits were analysed to detect common and individual genotype features. The genetic variation in NUE at high N input was mainly explained by variation in N uptake. Even though plants managed N uptake and N metabolism differently under N+ and N-, NUE was similar in these two conditions, showing that NUE was exclusively genetically determined. Hierarchical classification revealed that the physiological classes arising were similar under N-and N+. Both wasteful and efficient genotypes were detected. Three extreme genotypes, Col-0, Bur-0, and Tsu-0, were noted. Bur-0 and Tsu-0 exhibited high NUE and large biomass. Col-0 showed the reverse: low NUE and low biomass. Bur-0 appeared poorly tolerant of a high N supply. The present data will facilitate the choice of Arabidopsis accessions as parents of recombinant inbred line populations suitable for the mapping of quantitiative trait loci related to NUE, NupE, and N storage capacity. © 2010 The Author(s).

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