Publications by authors named "Adeline Berger"

28 Publications

  • Page 1 of 1

An Model of Human Retinal Detachment Reveals Successive Death Pathway Activations.

Front Neurosci 2020 26;14:571293. Epub 2020 Nov 26.

Department of Ophthalmology, University of Lausanne, Jules-Gonin Eye Hospital, Fondation Asile des Aveugles, Lausanne, Switzerland.

Purpose: was to create an model of human retinal detachment (RD) to study the mechanisms of photoreceptor death.

Methods: Human retinas were obtained through eye globe donations for research purposes and cultivated as explants. Cell death was investigated in retinas with (control) and without retinal pigment epithelium (RPE) cells to mimic RD. Tissues were studied at different time points and immunohistological analyses for TUNEL, Cleaved caspase3, AIF, CDK4 and the epigenetic mark H3K27me3 were performed. Human and monkey eye globes with retinal detachment served as controls.

Results: The number of TUNEL-positive cells, compared between 1 and 7 days, increased with time in both retinas with RPE (from 1.2 ± 0.46 to 8 ± 0.89, = 4) and without RPE (from 2.6 ± 0.73 to 16.3 ± 1.27, < 0.014). In the group without RPE, cell death peaked at day 3 ( = 0.014) and was high until day 7. Almost no Cleaved-Caspase3 signal was observed, whereas a transient augmentation at day 3 of AIF-positive cells was observed to be about 10-fold in comparison to the control group ( = 2). Few CDK4-positive cells were found in both groups, but significantly more in the RD group at day 7 (1.8 ± 0.24 vs. 4.7 ± 0.58, = 0.014). The H3K27me3 mark increased by 7-fold after 5 days in the RD group ( = 0.014) and slightly decreased at day 7 and was also observed to be markedly increased in human and monkey detached retina samples.

Conclusion: AIF expression coincides with the first peak of cell death, whereas the H3K27me3 mark increases during the cell death plateau, suggesting that photoreceptor death is induced by different successive pathways after RD. This model should permit the identification of neuroprotective drugs with clinical relevance.
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http://dx.doi.org/10.3389/fnins.2020.571293DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7726250PMC
November 2020

ABSCISIC ACID-DEFICIENT4 Has an Essential Function in Both cis-Violaxanthin and cis-Neoxanthin Synthesis.

Plant Physiol 2020 11 3;184(3):1303-1316. Epub 2020 Sep 3.

Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, 78000, Versailles, France

Abscisic acid (ABA), a plant hormone synthesized from carotenoids, functions in seed germination and abiotic stress responses. ABA is derived from the cleavage of 9-cis-isomers of violaxanthin and neoxanthin, which are oxygenated carotenoids, also called xanthophylls. Although genes encoding enzymes responsible for most steps of the ABA biosynthesis pathway have been identified, enzymatic reactions leading to the production of these cis-isomers from trans-violaxanthin remain poorly understood. Two mutants that lack trans- and cis-neoxanthin, tomato () () and Arabidopsis () (), were identified previously, but only exhibited ABA-deficient phenotypes. No enzymatic activity was detected for ABA4 and NXD1 proteins, and their exact function remained unknown. To further investigate ABA4 and NXD1 function in Arabidopsis, we compared phenotypes of single and double mutants, and analyzed the effect of ABA4 overexpression on ABA and carotenoid accumulation in wild-type and mutant backgrounds. We provide convergent evidence that ABA4 is not only required for the formation of trans- and 9'-cis-neoxanthin from trans-violaxanthin, but also controls 9-cis-violaxanthin accumulation. While produces high amounts of 9-cis-violaxanthin and ABA, exhibits reduced levels in both leaves and seeds. Furthermore, ABA4 constitutive expression in increases both 9-cis-violaxanthin and ABA accumulation. Subcellular localization of NXD1 protein in transient expression assays suggests that production of the NXD1-derived factor required for neoxanthin synthesis takes place in the cytosol. Finally, we postulate that ABA4, with additional unknown cofactor(s), is required for, or contributes to, trans-to-cis violaxanthin isomerase activity, producing both cis-xanthophyll precursors of ABA.
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http://dx.doi.org/10.1104/pp.20.00947DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7608147PMC
November 2020

Pharmacological disruption of the Notch transcription factor complex.

Proc Natl Acad Sci U S A 2020 07 29;117(28):16292-16301. Epub 2020 Jun 29.

Swiss Institute for Experimental Cancer Research, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland;

Notch pathway signaling is implicated in several human cancers. Aberrant activation and mutations of Notch signaling components are linked to tumor initiation, maintenance, and resistance to cancer therapy. Several strategies, such as monoclonal antibodies against Notch ligands and receptors, as well as small-molecule γ-secretase inhibitors (GSIs), have been developed to interfere with Notch receptor activation at proximal points in the pathway. However, the use of drug-like small molecules to target the downstream mediators of Notch signaling, the Notch transcription activation complex, remains largely unexplored. Here, we report the discovery of an orally active small-molecule inhibitor (termed CB-103) of the Notch transcription activation complex. We show that CB-103 inhibits Notch signaling in primary human T cell acute lymphoblastic leukemia and other Notch-dependent human tumor cell lines, and concomitantly induces cell cycle arrest and apoptosis, thereby impairing proliferation, including in GSI-resistant human tumor cell lines with chromosomal translocations and rearrangements in Notch genes. CB-103 produces Notch loss-of-function phenotypes in flies and mice and inhibits the growth of human breast cancer and leukemia xenografts, notably without causing the dose-limiting intestinal toxicity associated with other Notch inhibitors. Thus, we describe a pharmacological strategy that interferes with Notch signaling by disrupting the Notch transcription complex and shows therapeutic potential for treating Notch-driven cancers.
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http://dx.doi.org/10.1073/pnas.1922606117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7368267PMC
July 2020

Natural Variation Reveals a Key Role for Rhamnogalacturonan I in Seed Outer Mucilage and Underlying Genes.

Plant Physiol 2019 12 7;181(4):1498-1518. Epub 2019 Oct 7.

Institut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, Centre National de la Recherche Scientifique, Université Paris-Saclay, RD10, 78026 Versailles cedex, France

On imbibition, Arabidopsis () seeds release polysaccharides from their epidermal cells that form a two-layered hydrogel, termed mucilage. Analysis of a publicly available data set of outer seed mucilage traits of over 300 accessions showed little natural variation in composition. This mucilage is almost exclusively made up of rhamnogalacturonan I (RGI), highlighting the importance of this pectin for outer mucilage function. In a genome-wide association study, observed variations in polymer amount and macromolecular characteristics were linked to several genome polymorphisms, indicating the complexity of their genetic regulation. Natural variants with high molar mass were associated with a gene encoding a putative glycosyltransferase called MUCILAGE-RELATED70 (MUCI70). insertion mutants produced many short RGI polymers that were highly substituted with xylan, confirming that polymorphism in this gene can affect RGI polymer size. A second gene encoding a putative copper amine oxidase of clade 1a (CuAOα1) was associated with natural variation in the amount of RGI present in the outer mucilage layer; mutants validated its role in pectin production. As the mutant phenotype is unique, with RGI production only impaired for outer mucilage, this indicates that CuAOα1 contributes to a further mechanism controlling mucilage synthesis.
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http://dx.doi.org/10.1104/pp.19.00763DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6878024PMC
December 2019

N-Myc-mediated epigenetic reprogramming drives lineage plasticity in advanced prostate cancer.

J Clin Invest 2019 07 1;129(9):3924-3940. Epub 2019 Jul 1.

Department of Pathology and Laboratory Medicine.

Despite recent therapeutic advances, prostate cancer remains a leading cause of cancer-related death. A subset of castration resistant prostate cancers become androgen receptor (AR) signaling-independent and develop neuroendocrine prostate cancer (NEPC) features through lineage plasticity. These NEPC tumors, associated with aggressive disease and poor prognosis, are driven, in part, by aberrant expression of N-Myc, through mechanisms that remain unclear. Integrative analysis of the N-Myc transcriptome, cistrome and interactome using in vivo, in vitro and ex vivo models (including patient-derived organoids) identified a lineage switch towards a neural identity associated with epigenetic reprogramming. N-Myc and known AR-co-factors (e.g., FOXA1 and HOXB13) overlapped, independently of AR, at genomic loci implicated in neural lineage specification. Moreover, histone marks specifically associated with lineage-defining genes were reprogrammed by N-Myc. We also demonstrated that the N-Myc-induced molecular program accurately classifies our cohort of patients with advanced prostate cancer. Finally, we revealed the potential for EZH2 inhibition to reverse the N-Myc-induced suppression of epithelial lineage genes. Altogether, our data provide insights on how N-Myc regulates lineage plasticity and epigenetic reprogramming associated with lineage-specification. The N-Myc signature we defined could also help predict the evolution of prostate cancer and thus better guide the choice of future therapeutic strategies.
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http://dx.doi.org/10.1172/JCI127961DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6715370PMC
July 2019

Characterization of the ERG-regulated Kinome in Prostate Cancer Identifies TNIK as a Potential Therapeutic Target.

Neoplasia 2019 04 20;21(4):389-400. Epub 2019 Mar 20.

Cancer Program, Biomedicine Discovery Institute, Monash University, Victoria, Australia; Department of Biochemistry and Molecular Biology, Monash University, Victoria, Australia. Electronic address:

Approximately 50% of prostate cancers harbor the TMPRSS2:ERG fusion, resulting in elevated expression of the ERG transcription factor. Despite the identification of this subclass of prostate cancers, no personalized therapeutic strategies have achieved clinical implementation. Kinases are attractive therapeutic targets as signaling networks are commonly perturbed in cancers. The impact of elevated ERG expression on kinase signaling networks in prostate cancer has not been investigated. Resolution of this issue may identify novel therapeutic approaches for ERG-positive prostate cancers. In this study, we used quantitative mass spectrometry-based kinomic profiling to identify ERG-mediated changes to cellular signaling networks. We identified 76 kinases that were differentially expressed and/or phosphorylated in DU145 cells engineered to express ERG. In particular, the Traf2 and Nck-interacting kinase (TNIK) was markedly upregulated and phosphorylated on multiple sites upon ERG overexpression. Importantly, TNIK has not previously been implicated in prostate cancer. To validate the clinical relevance of these findings, we characterized expression of TNIK and TNIK phosphorylated at serine 764 (pS764) in a localized prostate cancer patient cohort and showed that nuclear enrichment of TNIK (pS764) was significantly positively correlated with ERG expression. Moreover, TNIK protein levels were dependent upon ERG expression in VCaP cells and primary cells established from a prostate cancer patient-derived xenograft. Furthermore, reduction of TNIK expression and activity by silencing TNIK expression or using the TNIK inhibitor NCB-0846 reduced cell viability, colony formation and anchorage independent growth. Therefore, TNIK represents a novel and actionable therapeutic target for ERG-positive prostate cancers that could be exploited to develop new treatments for these patients.
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http://dx.doi.org/10.1016/j.neo.2019.02.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6426874PMC
April 2019

Autophagy controls resource allocation and protein storage accumulation in Arabidopsis seeds.

J Exp Bot 2018 03;69(6):1403-1414

Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, Versailles, France.

Autophagy is essential for nutrient recycling and plays a fundamental role in seed production and grain filling in plants. Autophagy participates in nitrogen remobilization at the whole-plant level, and the seeds of autophagy mutants present abnormal C and N contents relative to wild-type (WT) plants. It is well known that autophagy (ATG) genes are induced in leaves during senescence; however, expression of such genes in seeds has not yet been reported. In this study we show that most of the ATG genes are induced during seed maturation in Arabidopsis siliques. Promoter-ATG8f::UIDA and promoter-ATG8f::GFP fusions showed the strong expression of ATG8f in the phloem companion cells of pericarps and the funiculus, and in the embryo. Expression was especially strong at the late stages of development. The presence of many GFP-ATG8 pre-autophagosomal structures and autophagosomes confirmed the presence of autophagic activity in WT seed embryos. Seeds of atg5 and WT plants grown under low- or high-nitrate conditions were analysed. Nitrate-independent phenotypes were found with higher seed abortion in atg5 and early browing, higher total protein concentrations in the viable seeds of this mutant as compared to the WT. The higher total protein accumulation in atg5 viable seeds was significant from early developmental stages onwards. In addition, relatively low and early accumulation of 12S globulins were found in atg5 seeds. These features led us to the conclusion that atg5 seed development is accelerated and that the protein storage deposition pathway is somehow abnormal or incomplete.
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http://dx.doi.org/10.1093/jxb/ery012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6018931PMC
March 2018

Identification of novel prostate cancer drivers using RegNetDriver: a framework for integration of genetic and epigenetic alterations with tissue-specific regulatory network.

Genome Biol 2017 07 27;18(1):141. Epub 2017 Jul 27.

Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, 10065, USA.

We report a novel computational method, RegNetDriver, to identify tumorigenic drivers using the combined effects of coding and non-coding single nucleotide variants, structural variants, and DNA methylation changes in the DNase I hypersensitivity based regulatory network. Integration of multi-omics data from 521 prostate tumor samples indicated a stronger regulatory impact of structural variants, as they affect more transcription factor hubs in the tissue-specific network. Moreover, crosstalk between transcription factor hub expression modulated by structural variants and methylation levels likely leads to the differential expression of target genes. We report known prostate tumor regulatory drivers and nominate novel transcription factors (ERF, CREB3L1, and POU2F2), which are supported by functional validation.
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http://dx.doi.org/10.1186/s13059-017-1266-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5530464PMC
July 2017

N-Myc Induces an EZH2-Mediated Transcriptional Program Driving Neuroendocrine Prostate Cancer.

Cancer Cell 2016 10;30(4):563-577

Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY 10065, USA; Meyer Cancer Center, Weill Cornell Medicine, New York, NY 10065, USA; Englander Institute for Precision Medicine, New York-Presbyterian Hospital, Weill Cornell Medicine, New York, NY 10065, USA. Electronic address:

The transition from castration-resistant prostate adenocarcinoma (CRPC) to neuroendocrine prostate cancer (NEPC) has emerged as an important mechanism of treatment resistance. NEPC is associated with overexpression and gene amplification of MYCN (encoding N-Myc). N-Myc is an established oncogene in several rare pediatric tumors, but its role in prostate cancer progression is not well established. Integrating a genetically engineered mouse model and human prostate cancer transcriptome data, we show that N-Myc overexpression leads to the development of poorly differentiated, invasive prostate cancer that is molecularly similar to human NEPC. This includes an abrogation of androgen receptor signaling and induction of Polycomb Repressive Complex 2 signaling. Altogether, our data establishes N-Myc as an oncogenic driver of NEPC.
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http://dx.doi.org/10.1016/j.ccell.2016.09.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5540451PMC
October 2016

mRNA trans-splicing in gene therapy for genetic diseases.

Wiley Interdiscip Rev RNA 2016 07 28;7(4):487-98. Epub 2016 Mar 28.

Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Département des Sciences du Vivant (DSV), Institut d'Imagerie Biomédicale (I2BM), Molecular Imaging Research Center (MIRCen), Fontenay-aux-Roses, France.

Spliceosome-mediated RNA trans-splicing, or SMaRT, is a promising strategy to design innovative gene therapy solutions for currently intractable genetic diseases. SMaRT relies on the correction of mutations at the post-transcriptional level by modifying the mRNA sequence. To achieve this, an exogenous RNA is introduced into the target cell, usually by means of gene transfer, to induce a splice event in trans between the exogenous RNA and the target endogenous pre-mRNA. This produces a chimeric mRNA composed partly of exons of the latter, and partly of exons of the former, encoding a sequence free of mutations. The principal challenge of SMaRT technology is to achieve a reaction as complete as possible, i.e., resulting in 100% repairing of the endogenous mRNA target. The proof of concept of SMaRT feasibility has already been established in several models of genetic diseases caused by recessive mutations. In such cases, in fact, the repair of only a portion of the mutant mRNA pool may be sufficient to obtain a significant therapeutic effect. However in the case of dominant mutations, the target cell must be freed from the majority of mutant mRNA copies, requiring a highly efficient trans-splicing reaction. This likely explains why only a few examples of SMaRT approaches targeting dominant mutations are reported in the literature. In this review, we explain in details the mechanism of trans-splicing, review the different strategies that are under evaluation to lead to efficient trans-splicing, and discuss the advantages and limitations of SMaRT. WIREs RNA 2016, 7:487-498. doi: 10.1002/wrna.1347 For further resources related to this article, please visit the WIREs website.
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http://dx.doi.org/10.1002/wrna.1347DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5071737PMC
July 2016

Xylans Provide the Structural Driving Force for Mucilage Adhesion to the Arabidopsis Seed Coat.

Plant Physiol 2016 05 15;171(1):165-78. Epub 2016 Mar 15.

INRA, UR 1268 Biopolymères Interactions Assemblages, F-44316 Nantes, France (M.-C.R., M.-J.C., J.V.); andInstitut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, CNRS, Université Paris-Saclay, RD10, 78026 Versailles cedex, France (J.T., A.B., C.S., F.G., L.B., H.M.N.)

Arabidopsis (Arabidopsis thaliana) seed coat epidermal cells produce large amounts of mucilage that is released upon imbibition. This mucilage is structured into two domains: an outer diffuse layer that can be easily removed by agitation and an inner layer that remains attached to the outer seed coat. Both layers are composed primarily of pectic rhamnogalacturonan I (RG-I), the inner layer also containing rays of cellulose that extend from the top of each columella. Perturbation in cellulosic ray formation has systematically been associated with a redistribution of pectic mucilage from the inner to the outer layer, in agreement with cellulose-pectin interactions, the nature of which remained unknown. Here, by analyzing the outer layer composition of a series of mutant alleles, a tight proportionality of xylose, galacturonic acid, and rhamnose was evidenced, except for mucilage modified5-1 (mum5-1; a mutant showing a redistribution of mucilage pectin from the inner adherent layer to the outer soluble one), for which the rhamnose-xylose ratio was increased drastically. Biochemical and in vitro binding assay data demonstrated that xylan chains are attached to RG-I chains and mediate the adsorption of mucilage to cellulose microfibrils. mum5-1 mucilage exhibited very weak adsorption to cellulose. MUM5 was identified as a putative xylosyl transferase recently characterized as MUCI21. Together, these findings suggest that the binding affinity of xylose ramifications on RG-I to a cellulose scaffold is one of the factors involved in the formation of the adherent mucilage layer.
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http://dx.doi.org/10.1104/pp.16.00211DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4854713PMC
May 2016

Xyloglucan Metabolism Differentially Impacts the Cell Wall Characteristics of the Endosperm and Embryo during Arabidopsis Seed Germination.

Plant Physiol 2016 Mar 29;170(3):1367-80. Epub 2016 Jan 29.

Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, RD10, F-78026 Versailles, France

Cell wall remodeling is an essential mechanism for the regulation of plant growth and architecture, and xyloglucans (XyGs), the major hemicellulose, are often considered as spacers of cellulose microfibrils during growth. In the seed, the activity of cell wall enzymes plays a critical role in germination by enabling embryo cell expansion leading to radicle protrusion, as well as endosperm weakening prior to its rupture. A screen for Arabidopsis (Arabidopsis thaliana) mutants affected in the hormonal control of germination identified a mutant, xyl1, able to germinate on paclobutrazol, an inhibitor of gibberellin biosynthesis. This mutant also exhibited reduced dormancy and increased resistance to high temperature. The XYL1 locus encodes an α-xylosidase required for XyG maturation through the trimming of Xyl. The xyl1 mutant phenotypes were associated with modifications to endosperm cell wall composition that likely impact on its resistance, as further demonstrated by the restoration of normal germination characteristics by endosperm-specific XYL1 expression. The absence of phenotypes in mutants defective for other glycosidases, which trim Gal or Fuc, suggests that XYL1 plays the major role in this process. Finally, the decreased XyG abundance in hypocotyl longitudinal cell walls of germinating embryos indicates a potential role in cell wall loosening and anisotropic growth together with pectin de-methylesterification.
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http://dx.doi.org/10.1104/pp.15.01312DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4775114PMC
March 2016

Deciphering the molecular basis of invasiveness in Sdhb-deficient cells.

Oncotarget 2015 Oct;6(32):32955-65

INSERM, UMR970, Paris Cardiovascular Research Centre, F-75015 Paris, France.

Metastatic pheochromocytomas and paragangliomas (PPGL) are malignant neuroendocrine tumors frequently associated with germline mutations in the SDHB gene. SDHB-mutated PPGL display a hypermethylator phenotype associated with hallmarks of epithelial-to-mesenchymal transition (EMT). In the present study, we report the characterization of a unique model of Sdhb knockout in mouse chromaffin cells. Sdhb deficient cells exhibit a metastatic phenotype as highlighted by increased individual cell migration (characterized by faster motility and increased persistence) as well as high invasive and adhesion abilities. This phenotype is associated with the modulation of Twist1, Twist2, Tcf3, Snai1, N-cadherin or Krt19 expression, reflecting an EMT-like reprogramming of cells. Krt19 is epigenetically silenced in Sdhb-deficient cells and re-expressed after treatment by the demethylating agent decitabine. Krt19 rescue by lentiviral transduction in Sdhb-deficient cells and Krt19 inhibition by RNA interference in wild-type cells were performed. Both studies revealed the involvement of KRT19 in the invasive phenotype by modulating collective and individual migration and cell/extra-cellular matrix adhesion properties. These findings underline the role of hypermethylation and EMT in the in vitro acquisition of metastatic properties, following SDHB loss of function.
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http://dx.doi.org/10.18632/oncotarget.5106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4741742PMC
October 2015

MUCILAGE-RELATED10 Produces Galactoglucomannan That Maintains Pectin and Cellulose Architecture in Arabidopsis Seed Mucilage.

Plant Physiol 2015 Sep 28;169(1):403-20. Epub 2015 Jul 28.

Institute for Biosciences and Geosciences (Plant Sciences), Forschungszentrum Jülich, 52425 Juelich, Germany (C.V., M.H.-W.S., B.U., M.G.);Institute for Botany and Molecular Genetics, BioEconomy Science Center, RWTH Aachen University, 52056 Aachen, Germany (C.V., M.H.-W.S., B.Y., B.U.);Institut National de la Recherche Agronomique and AgroParisTech, Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, ERL Centre National de la Recherche Scientifique 3559, Saclay Plant Sciences, F-78026 Versailles, France (A.B., H.M.N.);Joint BioEnergy Institute and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94702 (B.E., H.V.S.); andDepartment of Plant and Microbial Biology, University of California, Berkeley, California 94720 (H.V.S.).

Plants invest a lot of their resources into the production of an extracellular matrix built of polysaccharides. While the composition of the cell wall is relatively well characterized, the functions of the individual polymers and the enzymes that catalyze their biosynthesis remain poorly understood. We exploited the Arabidopsis (Arabidopsis thaliana) seed coat epidermis (SCE) to study cell wall synthesis. SCE cells produce mucilage, a specialized secondary wall that is rich in pectin, at a precise stage of development. A coexpression search for MUCILAGE-RELATED (MUCI) genes identified MUCI10 as a key determinant of mucilage properties. MUCI10 is closely related to a fenugreek (Trigonella foenumgraecum) enzyme that has in vitro galactomannan α-1,6-galactosyltransferase activity. Our detailed analysis of the muci10 mutants demonstrates that mucilage contains highly branched galactoglucomannan (GGM) rather than unbranched glucomannan. MUCI10 likely decorates glucomannan, synthesized by CELLULOSE SYNTHASE-LIKE A2, with galactose residues in vivo. The degree of galactosylation is essential for the synthesis of the GGM backbone, the structure of cellulose, mucilage density, as well as the adherence of pectin. We propose that GGM scaffolds control mucilage architecture along with cellulosic rays and show that Arabidopsis SCE cells represent an excellent model in which to study the synthesis and function of GGM. Arabidopsis natural varieties with defects similar to muci10 mutants may reveal additional genes involved in GGM synthesis. Since GGM is the most abundant hemicellulose in the secondary walls of gymnosperms, understanding its biosynthesis may facilitate improvements in the production of valuable commodities from softwoods.
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http://dx.doi.org/10.1104/pp.15.00851DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4577422PMC
September 2015

Repair of rhodopsin mRNA by spliceosome-mediated RNA trans-splicing: a new approach for autosomal dominant retinitis pigmentosa.

Mol Ther 2015 May 26;23(5):918-930. Epub 2015 Jan 26.

Centre de recherche Institut de la Vision, Sorbonne Universités, Université Pierre et Marie Curie UM80, INSERM U968, and CNRS UMR 7210, Paris, France; Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Département des Sciences du Vivant (DSV), Institut d'Imagerie Biomédicale (I2BM), MIRCen, Fontenay-aux-Roses, France; Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud, Université Paris-Saclay, UMR9199, Neurodegenerative Diseases Laboratory, Fontenay-aux-Roses, France. Electronic address:

The promising clinical results obtained for ocular gene therapy in recent years have paved the way for gene supplementation to treat recessively inherited forms of retinal degeneration. The situation is more complex for dominant mutations, as the toxic mutant gene product must be removed. We used spliceosome-mediated RNA trans-splicing as a strategy for repairing the transcript of the rhodopsin gene, the gene most frequently mutated in autosomal dominant retinitis pigmentosa. We tested 17 different molecules targeting the pre-mRNA intron 1, by transient transfection of HEK-293T cells, with subsequent trans-splicing quantification at the transcript level. We found that the targeting of some parts of the intron promoted trans-splicing more efficiently than the targeting of other areas, and that trans-splicing rate could be increased by modifying the replacement sequence. We then developed cell lines stably expressing the rhodopsin gene, for the assessment of phenotypic criteria relevant to the pathogenesis of retinitis pigmentosa. Using this model, we showed that trans-splicing restored the correct localization of the protein to the plasma membrane. Finally, we tested our best candidate by AAV gene transfer in a mouse model of retinitis pigmentosa that expresses a mutant allele of the human rhodopsin gene, and demonstrated the feasibility of trans-splicing in vivo. This work paves the way for trans-splicing gene therapy to treat retinitis pigmentosa due to rhodopsin gene mutation and, more generally, for the treatment of genetic diseases with dominant transmission.
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http://dx.doi.org/10.1038/mt.2015.11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4427870PMC
May 2015

Alterations of iron distribution in Arabidopsis tissues infected by Dickeya dadantii.

Mol Plant Pathol 2015 Jun 27;16(5):521-8. Epub 2015 Feb 27.

AgroParisTech, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant Sciences, RD10, F-78026, Versailles, France; Sorbonne Universités, UPMC, Université Paris 06, UFR927, F-75005, Paris, France.

Dickeya dadantii is a plant-pathogenic enterobacterium responsible for plant soft rot disease in a wide range of hosts, including the model plant Arabidopsis thaliana. Iron distribution in infected A. thaliana was investigated at the cellular scale using the Perls'-diaminobenzidine-H2 O2 (PDH) method. Iron visualization during infection reveals a loss of iron from cellular compartments and plant cell walls. During symptom progression, two distinct zones are clearly visible: a macerated zone displaying weak iron content and a healthy zone displaying strong iron content. Immunolabelling of cell wall methylated pectin shows that pectin degradation is correlated with iron release from cell walls, indicating a strong relationship between cell wall integrity and iron in plant tissues. Using a D. dadantii lipopolysaccharide antibody, we show that bacteria are restricted to the infected tissue, and that they accumulate iron in planta. In conclusion, weak iron content is strictly correlated with bacterial cell localization in the infected tissues, indicating a crucial role of this element during the interaction. This is the first report of iron localization at the cellular level during a plant-microbe interaction and shows that PDH is a method of choice in this type of investigation.
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http://dx.doi.org/10.1111/mpp.12208DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6638429PMC
June 2015

Spectral-domain optical coherence tomography of the rodent eye: highlighting layers of the outer retina using signal averaging and comparison with histology.

PLoS One 2014 2;9(5):e96494. Epub 2014 May 2.

Inserm, U 968, Paris, France; UPMC Univ Paris 06, UMR_S 968, Institut de la Vision, Paris, France; CEA, DSV, I2BM, Molecular Imaging Research Center (MIRCen), Fontenay-aux-Roses, France; CNRS, CEA URA 2210, Fontenay-aux-Roses, France.

Spectral-Domain Optical Coherence Tomography (SD-OCT) is a widely used method to observe retinal layers and follow pathological events in human. Recently, this technique has been adapted for animal imaging. This non-invasive technology brings a cross-sectional visualization of the retina, which permits to observe precisely each layer. There is a clear expansion of the use of this imaging modality in rodents, thus, a precise characterization of the different outer retinal layers observed by SD-OCT is now necessary to make the most of this technology. The identification of the inner strata until the outer nuclear layer has already been clearly established, while the attribution of the layers observed by SD-OCT to the structures corresponding to photoreceptors segments and retinal pigment epithelium is much more questionable. To progress in the understanding of experimental SD-OCT imaging, we developed a method for averaging SD-OCT data to generate a mean image allowing to better delineate layers in the retina of pigmented and albino strains of mice and rats. It allowed us to locate precisely the interface between photoreceptors and retinal pigment epithelium and to identify unambiguously four layers corresponding to the inner and outer parts of photoreceptors segments. We show that the thickness of the various layers can be measured as accurately in vivo on SD-OCT images, than post-mortem by a morphometric analysis of histological sections. We applied SD-OCT to different models and demonstrated that it allows analysis of focal or diffuse retinal pathological processes such as mutation-dependent damages or light-driven modification of photoreceptors. Moreover, we report a new method of combined use of SD-OCT and integration to quantify laser-induced choroidal neovascularization. In conclusion, we clearly demonstrated that SD-OCT represents a valuable tool for imaging the rodent retina that is at least as accurate as histology, non-invasive and allows longitudinal follow-up of the same animal.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0096494PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4008571PMC
June 2015

Local evolution of seed flotation in Arabidopsis.

PLoS Genet 2014 Mar 13;10(3):e1004221. Epub 2014 Mar 13.

INRA, Institut Jean-Pierre Bourgin, UMR1318, Saclay Plant Sciences, Versailles, France; AgroParisTech, Institut Jean-Pierre Bourgin, UMR1318, Saclay Plant Sciences, Versailles, France.

Arabidopsis seeds rapidly release hydrophilic polysaccharides from the seed coat on imbibition. These form a heavy mucilage layer around the seed that makes it sink in water. Fourteen natural Arabidopsis variants from central Asia and Scandinavia were identified with seeds that have modified mucilage release and float. Four of these have a novel mucilage phenotype with almost none of the released mucilage adhering to the seed and the absence of cellulose microfibrils. Mucilage release was modified in the variants by ten independent causal mutations in four different loci. Seven distinct mutations affected one locus, coding the MUM2 β-D-galactosidase, and represent a striking example of allelic heterogeneity. The modification of mucilage release has thus evolved a number of times independently in two restricted geographical zones. All the natural mutants identified still accumulated mucilage polysaccharides in seed coat epidermal cells. Using nuclear magnetic resonance (NMR) relaxometry their production and retention was shown to reduce water mobility into internal seed tissues during imbibition, which would help to maintain seed buoyancy. Surprisingly, despite released mucilage being an excellent hydrogel it did not increase the rate of water uptake by internal seed tissues and is more likely to play a role in retaining water around the seed.
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http://dx.doi.org/10.1371/journal.pgen.1004221DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3953066PMC
March 2014

Understanding polysaccharide production and properties using seed coat mutants: future perspectives for the exploitation of natural variants.

Ann Bot 2014 Oct 7;114(6):1251-63. Epub 2014 Mar 7.

INRA, UR 1268 Biopolymères Interactions Assemblages, F-44316 Nantes, France.

Background: The epidermal cells of the seed coat of certain species accumulate polysaccharides during seed development for cell wall reinforcement or release on imbibition to form mucilage. Seed-coat epidermal cells show natural variation in their structure and mucilage production, which could explain the diverse ecophysiological roles proposed for the latter. Arabidopsis mucilage mutants have proved to be an important tool for the identification of genes involved in the production of seed-coat polysaccharides.

Scope: This review documents genes that have been characterized as playing a role in the differentiation of the epidermal cells of the arabidopsis seed coat, the natural variability in polysaccharide features of these cells and the physiological roles attributed to seed mucilage.

Conclusions: Seed-coat epidermal cells are an excellent model for the study of polysaccharide metabolism and properties. Intra- and interspecies natural variation in the differentiation of these epidermal cells is an under-exploited resource for such studies and promises to play an important part in improving our knowledge of polysaccharide production and ecophysiological function.
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http://dx.doi.org/10.1093/aob/mcu011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4195541PMC
October 2014

Specialization of oleosins in oil body dynamics during seed development in Arabidopsis seeds.

Plant Physiol 2014 Apr 10;164(4):1866-78. Epub 2014 Feb 10.

Institut National de la Recherche Agronomique, Unité Mixte de Recherche 1318, AgroParisTech, and Equipe de Recherche Labellisée 3559 Centre National de la Recherche Scientifique, Institut Jean-Pierre Bourgin, F-78026 Versailles cedex, France.

Oil bodies (OBs) are seed-specific lipid storage organelles that allow the accumulation of neutral lipids that sustain plantlet development after the onset of germination. OBs are covered with specific proteins embedded in a single layer of phospholipids. Using fluorescent dyes and confocal microscopy, we monitored the dynamics of OBs in living Arabidopsis (Arabidopsis thaliana) embryos at different stages of development. Analyses were carried out with different genotypes: the wild type and three mutants affected in the accumulation of various oleosins (OLE1, OLE2, and OLE4), three major OB proteins. Image acquisition was followed by a detailed statistical analysis of OB size and distribution during seed development in the four dimensions (x, y, z, and t). Our results indicate that OB size increases sharply during seed maturation, in part by OB fusion, and then decreases until the end of the maturation process. In single, double, and triple mutant backgrounds, the size and spatial distribution of OBs are modified, affecting in turn the total lipid content, which suggests that the oleosins studied have specific functions in the dynamics of lipid accumulation.
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http://dx.doi.org/10.1104/pp.113.233262DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3982749PMC
April 2014

Regulation of flavonoid biosynthesis involves an unexpected complex transcriptional regulation of TT8 expression, in Arabidopsis.

New Phytol 2013 Apr 12;198(1):59-70. Epub 2013 Feb 12.

INRA, Institut Jean-Pierre Bourgin, Saclay Plant Sciences, UMR1318, RD10, F-78026, Versailles, France.

TT8/bHLH042 is a key regulator of anthocyanins and proanthocyanidins (PAs) biosynthesis in Arabidopsis thaliana. TT8 transcriptional activity has been studied extensively, and relies on its ability to form, with several R2R3-MYB and TTG1 (WD-Repeat protein), different MYB-bHLH-WDR (MBW) protein complexes. By contrast, little is known on how TT8 expression is itself regulated. Transcriptional regulation of TT8 expression was studied using molecular, genetic and biochemical approaches. Functional dissection of the TT8 promoter revealed its modular structure. Two modules were found to specifically drive TT8 promoter activity in PA- and anthocyanin-accumulating cells, by differentially integrating the signals issued from different regulators, in a spatio-temporal manner. Interestingly, this regulation involves at least six different MBW complexes, and an unpredicted positive feedback regulatory loop between TT8 and TTG2. Moreover, the results suggest that some putative new regulators remain to be discovered. Finally, specific cis-regulatory elements through which TT8 expression is regulated were identified and characterized. Together, these results provide a molecular model consistent with the specific and highly regulated expression of TT8. They shed new light into the transcriptional regulation of flavonoid biosynthesis and provide new clues and tools for further investigation in Arabidopsis and other plant species.
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http://dx.doi.org/10.1111/nph.12142DOI Listing
April 2013

PECTIN METHYLESTERASE INHIBITOR6 promotes Arabidopsis mucilage release by limiting methylesterification of homogalacturonan in seed coat epidermal cells.

Plant Cell 2013 Jan 29;25(1):308-23. Epub 2013 Jan 29.

Institut National de la Recherche Agronomique, Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318, Saclay Plant Sciences, F-78026 Versailles, France.

Imbibed seeds of the Arabidopsis thaliana accession Djarly are affected in mucilage release from seed coat epidermal cells. The impaired locus was identified as a pectin methylesterase inhibitor gene, PECTIN METHYLESTERASE INHIBITOR6 (PMEI6), specifically expressed in seed coat epidermal cells at the time when mucilage polysaccharides are accumulated. This spatio-temporal regulation appears to be modulated by GLABRA2 and LEUNIG HOMOLOG/MUCILAGE MODIFIED1, as expression of PMEI6 is reduced in mutants of these transcription regulators. In pmei6, mucilage release was delayed and outer cell walls of epidermal cells did not fragment. Pectin methylesterases (PMEs) demethylate homogalacturonan (HG), and the majority of HG found in wild-type mucilage was in fact derived from outer cell wall fragments. This correlated with the absence of methylesterified HG labeling in pmei6, whereas transgenic plants expressing the PMEI6 coding sequence under the control of the 35S promoter had increased labeling of cell wall fragments. Activity tests on seeds from pmei6 and 35S:PMEI6 transgenic plants showed that PMEI6 inhibits endogenous PME activities, in agreement with reduced overall methylesterification of mucilage fractions and demucilaged seeds. Another regulator of PME activity in seed coat epidermal cells, the subtilisin-like Ser protease SBT1.7, acts on different PMEs, as a pmei6 sbt1.7 mutant showed an additive phenotype.
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http://dx.doi.org/10.1105/tpc.112.106575DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3584544PMC
January 2013

γ-Aminobutyric acid transaminase deficiency impairs central carbon metabolism and leads to cell wall defects during salt stress in Arabidopsis roots.

Plant Cell Environ 2013 May 29;36(5):1009-18. Epub 2012 Nov 29.

IGEPP, UMR1349 INRA, Université de Rennes 1, F-35653, Le Rheu, France.

Environmental constraints challenge cell homeostasis and thus require a tight regulation of metabolic activity. We have previously reported that the γ-aminobutyric acid (GABA) metabolism is crucial for Arabidopsis salt tolerance as revealed by the NaCl hypersensitivity of the GABA transaminase (GABA-T, At3g22200) gaba-t/pop2-1 mutant. In this study, we demonstrate that GABA-T deficiency during salt stress causes root and hypocotyl developmental defects and alterations of cell wall composition. A comparative genome-wide transcriptional analysis revealed that expression levels of genes involved in carbon metabolism, particularly sucrose and starch catabolism, were found to increase upon the loss of GABA-T function under salt stress conditions. Consistent with the altered mutant cell wall composition, a number of cell wall-related genes were also found differentially expressed. A targeted quantitative analysis of primary metabolites revealed that glutamate (GABA precursor) accumulated while succinate (the final product of GABA metabolism) significantly decreased in mutant roots after 1 d of NaCl treatment. Furthermore, sugar concentration was twofold reduced in gaba-t/pop2-1 mutant roots compared with wild type. Together, our results provide strong evidence that GABA metabolism is a major route for succinate production in roots and identify GABA as a major player of central carbon adjustment during salt stress.
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http://dx.doi.org/10.1111/pce.12033DOI Listing
May 2013

Epoxycarotenoid cleavage by NCED5 fine-tunes ABA accumulation and affects seed dormancy and drought tolerance with other NCED family members.

Plant J 2012 May 6;70(3):501-12. Epub 2012 Feb 6.

Institut Jean-Pierre Bourgin, UMR1318, INRA, AgroParisTech, F-78026 Versailles Cedex, France.

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.
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http://dx.doi.org/10.1111/j.1365-313X.2011.04887.xDOI Listing
May 2012

Assessment of human Nter and Cter BRCA1 mutations using growth and localization assays in yeast.

Hum Mutat 2011 Dec 20;32(12):1470-80. Epub 2011 Oct 20.

Institut Curie, Centre de Recherche, 26 rue d'Ulm, Paris, France.

A large number of missense mutations have been identified within the tumor suppressor gene BRCA1. Most of them, called "variants of unknown significance" (VUS), cannot be classified as pathogenic or neutral by genetic methods, which complicates their cancer risk assessment. Functional assays have been developed to circumvent this uncertainty. They aim to determine how VUS impact the BRCA1 protein structure or function, thereby giving an indication of their potential to cause cancer. So far, three relevant assays have been designed in yeast and used on large sets of variants. However, they are limited to variants mapped in restricted domains of BRCA1. One of them, the small colony phenotype (SCP) assay, monitors the BRCA1-dependent growth of yeast colonies that increases with pathogenic but not neutral mutations positioned in the Cter region. Here, we extend this assay to the Nter part of BRCA1. We also designed a new assay, called the "yeast localization phenotype (YLP) assay," based on the accumulation of BRCA1 in a single inclusion body in the yeast nucleus. This phenotype is altered by variants positioned both in the Nter and Cter regions. Together, these assays provide new perspectives for the functional assessment of BRCA1 mutations in yeast.
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http://dx.doi.org/10.1002/humu.21608DOI Listing
December 2011

CESA5 is required for the synthesis of cellulose with a role in structuring the adherent mucilage of Arabidopsis seeds.

Plant Physiol 2011 Aug 24;156(4):1725-39. Epub 2011 Jun 24.

Institut Jean-Pierre Bourgin, UMR 1318, INRA, AgroParisTech, F-78026 Versailles Cedex, France.

Imbibed Arabidopsis (Arabidopsis thaliana) seeds are encapsulated by mucilage that is formed of hydrated polysaccharides released from seed coat epidermal cells. The mucilage is structured with water-soluble and adherent layers, with cellulose present uniquely in an inner domain of the latter. Using a reverse-genetic approach to identify the cellulose synthases (CESAs) that produce mucilage cellulose, cesa5 mutants were shown to be required for the correct formation of these layers. Expression of CESA5 in the seed coat was specific to epidermal cells and coincided with the accumulation of mucilage polysaccharides in their apoplast. Analysis of sugar composition showed that although total sugar composition or amounts were unchanged, their partition between layers was different in the mutant, with redistribution from adherent to water-soluble mucilage. The macromolecular characteristics of the water-soluble mucilage were also modified. In accordance with a role for CESA5 in mucilage cellulose synthesis, crystalline cellulose contents were reduced in mutant seeds and birefringent microfibrils were absent from adherent mucilage. Although the mucilage-modified5 mutant showed similar defects to cesa5 in the distribution of sugar components between water-soluble and adherent mucilage, labeling of residual adherent mucilage indicated that cesa5 contained less cellulose and less pectin methyl esterification. Together, the results demonstrate that CESA5 plays a major and essential role in cellulose production in seed mucilage, which is critical for the establishment of mucilage structured in layers and domains.
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http://dx.doi.org/10.1104/pp.111.179077DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3149949PMC
August 2011

PII is induced by WRINKLED1 and fine-tunes fatty acid composition in seeds of Arabidopsis thaliana.

Plant J 2010 Oct 16;64(2):291-303. Epub 2010 Sep 16.

Institut Jean-Pierre Bourgin, Unité Mixte de Recherche 1318 INRA-AgroParisTech, INRA Centre de Versailles-Grignon, Route de Saint-Cyr (RD10), Versailles Cedex, France.

The PII protein is an integrator of central metabolism and energy levels. In Arabidopsis, allosteric sensing of cellular energy and carbon levels alters the ability of PII to interact with target enzymes such as N-acetyl-l-glutamate kinase and heteromeric acetyl-coenzyme A carboxylase, thereby modulating the biological activity of these plastidial ATP- and carbon-consuming enzymes. A quantitative reverse transcriptase-polymerase chain reaction approach revealed a threefold induction of the AtGLB1 gene (At4g01900) encoding PII during early seed maturation. The activity of the AtGLB1 promoter was consistent with this pattern. A complementary set of molecular and genetic analyses showed that WRINKLED1, a transcription factor known to induce glycolytic and fatty acid biosynthetic genes at the onset of seed maturation, directly controls AtGLB1 expression. Immunoblot analyses and immunolocalization experiments using anti-PII antibodies established that PII protein levels faithfully reflected AtGLB1 mRNA accumulation. At the subcellular level, PII was observed in plastids of maturing embryos. To further investigate the function of PII in seeds, comprehensive functional analyses of two pII mutant alleles were carried out. A transient increase in fatty acid production was observed in mutant seeds at a time when PII protein content was found to be maximal in wild-type seeds. Moreover, minor though statistically significant modifications of the fatty acid composition were measured in pII seeds, which exhibited decreased amounts of modified (elongated, desaturated) fatty acid species. The results obtained outline a role for PII in the fine tuning of fatty acid biosynthesis and partitioning in seeds.
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http://dx.doi.org/10.1111/j.1365-313X.2010.04332.xDOI Listing
October 2010

Premature arrest of the male flower meristem precedes sexual dimorphism in the dioecious plant Silene latifolia.

Proc Natl Acad Sci U S A 2006 Dec 28;103(49):18854-9. Epub 2006 Nov 28.

Laboratoire Reproduction et Développement des Plantes, UMR5667, CNRS/ Institut National de la Recherche Agronomique, Ecole Normale Supérieure de Lyon, Universite Lyon 1, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.

Most dioecious plant species are believed to derive from hermaphrodite ancestors. The regulatory pathways that have been modified during evolution of the hermaphrodite ancestors and led to the emergence of dioecious species still remain unknown. Silene latifolia is a dioecious plant species harboring XY sex chromosomes. To identify the molecular mechanisms involved in female organ suppression in male flowers of S. latifolia, we looked for genes potentially involved in the establishment of floral organ and whorl boundaries. We identified homologs of Arabidopsis thaliana SHOOTMERISTEMLESS (STM) and CUP SHAPED COTYLEDON (CUC) 1 and CUC2 genes in S. latifolia. Our phylogenetic analyses suggest that we identified true orthologs for both types of genes. Detailed expression analyses showed a conserved expression pattern for these genes between S. latifolia and A. thaliana, suggesting a conserved function of the corresponding proteins. Comparative in situ hybridization experiments between male, female, and hermaphrodite individuals reveal that these genes show a male-specific pattern of expression before any morphological difference become apparent. Our results make SlSTM and SlCUC strong candidates for being involved in sex determination in S. latifolia.
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http://dx.doi.org/10.1073/pnas.0606622103DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1693751PMC
December 2006