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Dumbliauskas E.,Conventionne Avec Luniversite Of Strasbourg | Lechner E.,Conventionne Avec Luniversite Of Strasbourg | Jaciubek M.,University of Zürich | Berr A.,Conventionne Avec Luniversite Of Strasbourg | And 9 more authors.
EMBO Journal | Year: 2011

Protein ubiquitylation regulates a broad variety of biological processes in all eukaryotes. Recent work identified a novel class of cullin-containing ubiquitin ligases (E3s) composed of CUL4, DDB1, and one WD40 protein, believed to act as a substrate receptor. Strikingly, CUL4-based E3 ligases (CRL4s) have important functions at the chromatin level, including responses to DNA damage in metazoans and plants and, in fission yeast, in heterochromatin silencing. Among putative CRL4 receptors we identified MULTICOPY SUPPRESSOR OF IRA1 (MSI1), which belongs to an evolutionary conserved protein family. MSI1-like proteins contribute to different protein complexes, including the epigenetic regulatory Polycomb repressive complex 2 (PRC2). Here, we provide evidence that Arabidopsis MSI1 physically interacts with DDB1A and is part of a multimeric protein complex including CUL4. CUL4 and DDB1 loss-of-function lead to embryo lethality. Interestingly, as in fis class mutants, cul4 mutants exhibit autonomous endosperm initiation and loss of parental imprinting of MEDEA, a target gene of the Arabidopsis PRC2 complex. In addition, after pollination both MEDEA transcript and protein accumulate in a cul4 mutant background. Overall, our work provides the first evidence of a physical and functional link between a CRL4 E3 ligase and a PRC2 complex, thus indicating a novel role of ubiquitylation in the repression of gene expression. © 2011 European Molecular Biology Organization | All Rights Reserved.


Lechner E.,Conventionne Avec Luniversite Of Strasbourg | Leonhardt N.,CEA Cadarache Center | Eisler H.,Conventionne Avec Luniversite Of Strasbourg | Eisler H.,BioSolutions GmbH | And 5 more authors.
Developmental Cell | Year: 2011

Being sessile organisms, plants need rapid and finely tuned signaling pathways to adapt their growth and survival over their immediate and often adverse environment. Abscisic acid (ABA) is a plant hormone crucial for both biotic and abiotic stress responses. In this study, we highlight a function of six Arabidopsis MATH-BTB proteins in ABA signaling. MATH-BTB proteins act as substrate-binding adaptors for the Cullin3-based ubiquitin E3 ligase. Our genetic and biochemical experiments demonstrate that the MATH-BTB proteins directly interact with and target for proteasomal degradation the class I homeobox-leucine zipper (HD-ZIP) transcription factor ATHB6, which was previously identified as a negative regulator of ABA responses. Reducing CUL3 BPM function leads to higher ATHB6 protein accumulation, reducing plant growth and fertility, and affects stomatal behavior and responses to ABA. We further demonstrate that ABA negatively regulates ATHB6 protein turnover, a situation reminiscent to ABI5, another transcription factor involved in ABA signaling. © 2011 Elsevier Inc.


Marrocco K.,Conventionne Avec Luniversite Of Strasbourg | Bergdoll M.,Conventionne Avec Luniversite Of Strasbourg | Achard P.,Conventionne Avec Luniversite Of Strasbourg | Criqui M.-C.,Conventionne Avec Luniversite Of Strasbourg | Genschik P.,Conventionne Avec Luniversite Of Strasbourg
Current Opinion in Plant Biology | Year: 2010

Ubiquitin-mediated proteolysis is one of the key mechanisms underlying cell cycle control in all eukaryotes. This is achieved by the action of ubiquitin ligases (E3s), which remove both negative and positive regulators of the cell cycle. Though our current understanding of the plant cell cycle has improved a lot these recent years, the identity of the E3s regulating it and their mode of action is still in its infancy. Nevertheless, recent research in Arabidopsis revealed some novel findings in this area. Thus the anaphase promoting complex/cyclosome (APC/C) not only controls mitotic events, but is also important in post-mitotic cells for normal plant development and cell differentiation. Moreover conserved and novel E3s were identified that target cyclin-dependent kinase inhibitors at different plant developmental stages. Finally, environmental constrains and stress hormones negatively impact on the cell cycle by processes that also include E3s. © 2010 Elsevier Ltd.


Genschik P.,Conventionne Avec Luniversite Of Strasbourg | Genschik P.,CNRS Biochemistry and Plant Molecular Physiology Laboratory | Marrocco K.,CNRS Biochemistry and Plant Molecular Physiology Laboratory | Bach L.,CNRS Biochemistry and Plant Molecular Physiology Laboratory | And 2 more authors.
Journal of Experimental Botany | Year: 2014

Plant growth control has become a major focus due to economic reasons and results from a balance of cell proliferation in meristems and cell elongation that occurs during differentiation. Research on plant cell proliferation over the last two decades has revealed that the basic cell-cycle machinery is conserved between human and plants, although specificities exist. While many regulatory circuits control each step of the cell cycle, the ubiquitin proteasome system (UPS) appears in fungi and metazoans as a major player. In particular, the UPS promotes irreversible proteolysis of a set of regulatory proteins absolutely required for cell-cycle phase transitions. Not unexpectedly, work over the last decade has brought the UPS to the forefront of plant cell-cycle research. In this review, we will summarize our knowledge of the function of the UPS in the mitotic cycle and in endoreduplication, and also in meiosis in higher plants. © The Author 2013.


Daviere J.-M.,Conventionne Avec Luniversite Of Strasbourg | Wild M.,Conventionne Avec Luniversite Of Strasbourg | Regnault T.,Conventionne Avec Luniversite Of Strasbourg | Baumberger N.,Conventionne Avec Luniversite Of Strasbourg | And 4 more authors.
Current Biology | Year: 2014

Regulation of plant height, one of the most important agronomic traits, is the focus of intensive research for improving crop performance [1]. Stem elongation takes place as a result of repeated cell divisions and subsequent elongation of cells produced by apical and intercalary meristems. The gibberellin (GA) phytohormones have long been known to control stem and internodal elongation by stimulating the degradation of nuclear growth-repressing DELLA proteins; however, the mechanism allowing GA-responsive growth is only slowly emerging [2]. Here, we show that DELLAs directly regulate the activity of the plant-specific class I TCP transcription factor family, key regulators of cell proliferation [3]. Our results demonstrate that class I TCP factors directly bind the promoters of core cell-cycle genes in Arabidopsis inflorescence shoot apices while DELLAs block TCP function by binding to their DNA-recognition domain. GAs antagonize such repression by promoting DELLA destruction and therefore cause a concomitant accumulation of TCP factors on promoters of cell-cycle genes. Consistent with this model, the quadruple mutant tcp8 tcp14 tcp15 tcp22 exhibits severe dwarfism and reduced responsiveness to GA action. Altogether, we conclude that GA-regulated DELLA-TCP interactions in inflorescence shoot apex provide a novel mechanism to control plant height. © 2014 Elsevier Ltd.


Wild M.,Conventionne Avec Luniversite Of Strasbourg | Achard P.,Conventionne Avec Luniversite Of Strasbourg
Plant Signaling and Behavior | Year: 2013

Gibberellins (GA) are phytohormones controlling major aspects of plant lifecycle including seed germination, growth and flower development. GA signaling is also involved in resistance to adverse conditions, thus providing a mechanism for environmentally responsive growth regulation. We recently characterized the function of a core component of the GA signal transduction pathway: RGL3. RGL3 belongs to the DELLA family of negative GA response regulators. Jasmonate (JA) rapidly induces RGL3 expression, which in turn enhances the expression of JA-responsive genes by inhibiting the activity of key repressors of JA signaling, the JAZ proteins. JA and ethylene (ET) are well known to play synergistic roles in plant disease resistance. Accordingly, we showed that RGL3 regulates plant defense responses by modulating JA/ET-mediated defense signaling pathway. © 2013 Landes Bioscience.


Masoud K.,Conventionne Avec Luniversite Of Strasbourg | Herzog E.,Conventionne Avec Luniversite Of Strasbourg | Chaboute M.-E.,Conventionne Avec Luniversite Of Strasbourg | Schmit A.-C.,Conventionne Avec Luniversite Of Strasbourg
Plant Journal | Year: 2013

The microtubular cytoskeleton plays a major role in cellular organization and proliferation. The first step in construction of a microtubule is microtubule nucleation. Individual microtubules then participate in organization of more complex microtubule arrays. A strong body of evidence suggests that the underlying molecular mechanisms involve protein complexes that are conserved among eukaryotes. However, plant cell specificities, mainly characterized by the presence of a cell wall and the absence of centrosomes, must be taken into account to understand their mitotic processes. The goal of this review is to summarize and discuss current knowledge regarding the mechanisms involved in plant spindle assembly during early mitotic events. The functions of the proteins currently characterized at microtubule nucleation sites and involved in spindle assembly are considered during cell-cycle progression from G 2 phase to metaphase. © 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.


Derrien B.,Conventionne Avec Luniversite Of Strasbourg | Genschik P.,Conventionne Avec Luniversite Of Strasbourg | Genschik P.,CNRS Biochemistry and Plant Molecular Physiology Laboratory
Frontiers in Plant Science | Year: 2014

RNA silencing has become a major focus of molecular and biomedical research in the last decade. This mechanism, which is conserved in most eukaryotes, has been extensively studied and is associated to various pathways implicated in the regulation of development, in the control of transposition events, heterochromatin maintenance and also playing a role in defense against viruses. Despite of its importance, the regulation of the RNA silencing machinery itself remains still poorly explored. Recently several reports in both plants and metazoans revealed that key components of RNA silencing, such as RNA-induced silencing complex component ARGONAUTE proteins, but also the endonuclease Dicer are subjected to proteasomal and autophagic pathways. Here we will review these post-translational proteolytic regulations with a special emphasis on plant research and also discuss their functional relevance. © 2014 Derrien and Genschik.


Batzenschlager M.,Conventionne Avec Luniversite Of Strasbourg | Herzog E.,Conventionne Avec Luniversite Of Strasbourg | Houlne G.,Conventionne Avec Luniversite Of Strasbourg | Schmit A.-C.,Conventionne Avec Luniversite Of Strasbourg | Chaboute M.-E.,Conventionne Avec Luniversite Of Strasbourg
Frontiers in Plant Science | Year: 2014

The functional organization of the nuclear envelope (NE) is only just emerging in plants with the recent characterization of NE protein complexes and their molecular links to the actin cytoskeleton. The NE also plays a role in microtubule nucleation by recruiting γ-Tubulin Complexes (γ-TuCs) which contribute to the establishment of a robust mitotic spindle. γ-tubulin Complex Protein 3 (GCP3)-interacting proteins (GIPs) have been identified recently as integral components of γ-TuCs. GIPs have been conserved throughout evolution and are also named MZT1 (mitotic-spindle organizing protein 1). This review focuses on recent data investigating the role of GIP/MZT1 at the NE, including insights from the study of GIP partners. It also uncovers new functions for GIP/MZT1 during interphase and highlights a current view of NE-associated components which are critical for nuclear shaping during both cell division and differentiation. © 2014 Batzenschlager, Herzog, Houlné, Schmit and Chabouté.


Wild M.,Conventionne Avec Luniversite Of Strasbourg | Daviere J.-M.,Conventionne Avec Luniversite Of Strasbourg | Cheminant S.,Conventionne Avec Luniversite Of Strasbourg | Regnault T.,Conventionne Avec Luniversite Of Strasbourg | And 5 more authors.
Plant Cell | Year: 2012

Gibberellins (GAs) are plant hormones involved in the regulation of plant growth in response to endogenous and environmental signals. GA promotes growth by stimulating the degradation of nuclear growth-repressing DELLA proteins. In Arabidopsis thaliana, DELLAs consist of a small family of five proteins that display distinct but also overlapping functions in repressing GA responses. This study reveals that DELLA RGA-LIKE3 (RGL3) protein is essential to fully enhance the jasmonate (JA)-mediated responses. We show that JA rapidly induces RGL3 expression in a CORONATINE INSENSITIVE1 (COI1)- and JASMONATE INSENSITIVE1 (JIN1/MYC2)-dependent manner. In addition, we demonstrate that MYC2 binds directly to RGL3 promoter. Furthermore, we show that RGL3 (like the other DELLAs) interacts with JA ZIM-domain (JAZ) proteins, key repressors of JA signaling. These findings suggest that JA/MYC2-dependent accumulation of RGL3 represses JAZ activity, which in turn enhances the expression of JA-responsive genes. Accordingly, we show that induction of primary JA-responsive genes is reduced in the rgl3-5 mutant and enhanced in transgenic lines overexpressing RGL3. Hence, RGL3 positively regulates JA-mediated resistance to the necrotroph Botrytis cinerea and susceptibility to the hemibiotroph Pseudomonas syringae. We propose that JA-mediated induction of RGL3 expression is of adaptive significance and might represent a recent functional diversification of the DELLAs. © 2012 American Society of Plant Biologists. All rights reserved.

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