Unite de Recherche en Genomique Vegetale

Évry, France

Unite de Recherche en Genomique Vegetale

Évry, France
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Brodersen P.,French National Center for Scientific Research | Brodersen P.,Copenhagen University | Sakvarelidze-Achard L.,French National Center for Scientific Research | Schaller H.,French National Center for Scientific Research | And 6 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2012

Plant and metazoan microRNAs (miRNAs) guide ARGONAUTE (AGO) protein complexes to regulate expression of complementary RNAs via base pairing. In the plant Arabidopsis thaliana, the main miRNA effector is AGO1, but few other factors required for miRNA activity are known. Here, we isolate the genes defined by the previously described miRNA action deficient (mad) mutants, mad3 and mad4. Both genes encode enzymes involved in isoprenoid biosynthesis. MAD3 encodes 3-hydroxy-3-methylglutaryl CoA reductase (HMG1), which functions in the initial C 5 building block biogenesis that precedes isoprenoidmetabolism.HMG1 is a key regulatory enzyme that controls the amounts of isoprenoid end products. MAD4 encodes sterol C-8 isomerase (HYDRA1) that acts downstream in dedicated sterol biosynthesis. Using yeast complementation assays and in planta application of lovastatin, a competitive inhibitor of HMG1, we show that defects in HMG1 catalytic activity are sufficient to inhibit miRNA activity. Many isoprenoid derivatives are indispensable structural and signaling components, and especially sterols are essential membrane constituents. Accordingly, we provide evidence that AGO1 is a peripheral membrane protein. Moreover, specific hypomorphic mutant alleles of AGO1 display compromised membrane association and AGO1-membrane interaction is reduced upon knockdown of HMG1/MAD3. These results suggest a possible basis for the requirement of isoprenoid biosynthesis for the activity of plant miRNAs, and unravel mechanistic features shared with their metazoan counterparts.


Tivendale N.D.,University of Tasmania | Davidson S.E.,University of Tasmania | Davies N.W.,University of Tasmania | Smith J.A.,University of Tasmania | And 10 more authors.
Plant Physiology | Year: 2012

Seeds of several agriculturally important legumes are rich sources of the only halogenated plant hormone, 4-chloroindole-3-acetic acid. However, the biosynthesis of this auxin is poorly understood. Here, we show that in pea (Pisum sativum) seeds, 4-chloroindole-3-acetic acid is synthesized via the novel intermediate 4-chloroindole-3-pyruvic acid, which is produced from 4-chlorotryptophan by two aminotransferases, TRYPTOPHAN AMINOTRANSFERASE RELATED1 and TRYPTOPHAN AMINOTRANSFERASE RELATED2. We characterize a tar2 mutant, obtained by Targeting Induced Local Lesions in Genomes, the seeds of which contain dramatically reduced 4-chloroindole-3-acetic acid levels as they mature. We also show that the widespread auxin, indole-3-acetic acid, is synthesized by a parallel pathway in pea. © 2012 American Society of Plant Biologists. All Rights Reserved.


Reymond M.C.,CNRS Laboratory of Plant Reproduction and Development | Brunoud G.,CNRS Laboratory of Plant Reproduction and Development | Chauvet A.,CNRS Laboratory of Plant Reproduction and Development | Martinez-Garcia J.F.,Catalan Institution for Research and Advanced Studies | And 4 more authors.
Plant Cell | Year: 2012

A key innovation of flowering plants is the female reproductive organ, the carpel. Here, we show that a mechanism that regulates carpel margin development in the model flowering plant Arabidopsis thaliana was recruited from light-regulated processes. This recruitment followed the loss from the basic helix-loop-helix transcription factor SPATULA (SPT) of a domain previously responsible for its negative regulation by phytochrome. We propose that the loss of this domain was a prerequisite for the light-independent expression in female reproductive tissues of a genetic module that also promotes shade avoidance responses in vegetative organs. Striking evidence for this proposition is provided by the restoration of wild-type carpel development to spt mutants by low red/far-red light ratios, simulating vegetation shade, which we show to occur via phytochrome B, PHYTOCHROME INTERACTING FACTOR4 (PIF4), and PIF5. Our data illustrate the potential of modular evolutionary events to generate rapid morphological change and thereby provide a molecular basis for neo-Darwinian theories that describe this nongradualist phenomenon. Furthermore, the effects shown here of light quality perception on carpel development lead us to speculate on the potential role of light-regulated mechanisms in plant organs that, like the carpel, form within the shade of surrounding tissues. © American Society of Plant Biologists. All rights reserved.


Degrave A.,French National Institute for Agricultural Research | Degrave A.,University Pierre and Marie Curie | Degrave A.,Agro ParisTech | Moreau M.,French National Institute for Agricultural Research | And 19 more authors.
Molecular Plant Pathology | Year: 2013

The type III effector DspA/E is an essential pathogenicity factor of the phytopathogenic bacterium Erwinia amylovora. We showed that DspA/E was required for transient bacterial growth in nonhost Arabidopsis thaliana leaves, as an E. amylovora dspA/E mutant was unable to grow. We expressed DspA/E in A. thaliana transgenic plants under the control of an oestradiol-inducible promoter, and found that DspA/E expressed inplanta restored the growth of a dspA/E mutant. DspA/E expression in these transgenic plants led to the modulation by at least two-fold of the expression of 384 genes, mostly induced (324 genes). Both induced and repressed genes contained high proportions of defence genes. DspA/E expression ultimately resulted in plant cell death without requiring a functional salicylic acid signalling pathway. Analysis of A. thaliana transgenic seedlings expressing a green fluorescent protein (GFP):DspA/E fusion indicated that the fusion protein could only be detected in a few cells per seedling, suggesting the degradation or absence of accumulation of DspA/E in plant cells. Consistently, we found that DspA/E repressed plant protein synthesis when injected by E. amylovora or when expressed in transgenic plants. Thus, we conclude that DspA/E is toxic to A. thaliana: it promotes modifications, among which the repression of protein synthesis could be determinant in the facilitation of necrosis and bacterial growth. © 2013 BSPP AND JOHN WILEY & SONS LTD.


Fernandez-Calvino L.,CSIC - Biological Research Center | Osorio S.,Max Planck Institute of Molecular Plant Physiology | Osorio S.,University of Malaga | Luisa Hernandez M.,CSIC - Instituto de la Grasa | And 8 more authors.
Plant Physiology | Year: 2014

During compatible virus infections, plants respond by reprogramming gene expression and metabolite content. While gene expression studies are profuse, our knowledge of the metabolic changes that occur in the presence of the virus is limited. Here, we combine gene expression and metabolite profiling in Arabidopsis (Arabidopsis thaliana) infected with Tobacco rattle virus (TRV) in order to investigate the influence of primary metabolism on virus infection. Our results revealed that primary metabolism is reconfigured in many ways during TRV infection, as reflected by significant changes in the levels of sugars and amino acids. Multivariate data analysis revealed that these alterations were particularly conspicuous at the time points of maximal accumulation of TRV, although infection time was the dominant source of variance during the process. Furthermore, TRV caused changes in lipid and fatty acid composition in infected leaves. We found that several Arabidopsis mutants deficient in branched-chain amino acid catabolism or fatty acid metabolism possessed altered susceptibility to TRV. Finally, we showed that increments in the putrescine content in TRV-infected plants correlated with enhanced tolerance to freezing stress in TRV-infected plants and that impairment of putrescine biosynthesis promoted virus multiplication. Our results thus provide an interesting overview for a better understanding of the relationship between primary metabolism and virus infection. © 2014 American Society of Plant Biologists. All rights reserved.


Jammes F.,French National Center for Scientific Research | Jammes F.,Pomona College | Leonhardt N.,Institute Of Biologie Environnementale Et Of Biotechnologie | Tran D.,French National Center for Scientific Research | And 11 more authors.
Plant Journal | Year: 2014

Faced with declining soil-water potential, plants synthesize abscisic acid (ABA), which then triggers stomatal closure to conserve tissue moisture. Closed stomates, however, also create several physiological dilemmas. Among these, the large CO2 influx required for net photosynthesis will be disrupted. Depleting CO2 in the plant will in turn bias stomatal opening by suppressing ABA sensitivity, which then aggravates transpiration further. We have investigated the molecular basis of how C3 plants resolve this H 2O-CO2 conflicting priority created by stomatal closure. Here, we have identified in Arabidopsis thaliana an early drought-induced spermidine spermine-N1-acetyltransferase homolog, which can slow ABA-mediated stomatal closure. Evidence from genetic, biochemical and physiological analyses has revealed that this protein does so by acetylating the metabolite 1,3-diaminopropane (DAP), thereby turning on the latter's intrinsic activity. Acetylated DAP triggers plasma membrane electrical and ion transport properties in an opposite way to those by ABA. Thus in adapting to low soil-water availability, acetyl-DAP could refrain stomates from complete closure to sustain CO2 diffusion to photosynthetic tissues. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.


Moreau M.,French National Institute for Agricultural Research | Moreau M.,University Pierre and Marie Curie | Moreau M.,Agro ParisTech | Degrave A.,French National Institute for Agricultural Research | And 16 more authors.
Molecular Plant-Microbe Interactions | Year: 2012

Erwinia amylovora causes fire blight in rosaceous plants. In nonhost Arabidopsis thaliana, E. amylovora triggers necrotic symptoms associated with transient bacterial multiplication, suggesting either that A. thaliana lacks a susceptibility factor or that it actively restricts E. amylovora growth. Inhibiting plant protein synthesis at the time of infection led to an increase in necrosis and bacterial multiplication and reduced callose deposition, indicating that A. thaliana requires active protein synthesis to restrict E. amylovora growth. Analysis of the callose synthase- deficient pmr4-1 mutant indicated that lack of callose deposition alone did not lead to increased sensitivity to E. amylovora. Transcriptome analysis revealed that approximately 20% of the genes induced following E. amylovora infection are related to defense and signaling. Analysis of mutants affected in NDR1 and EDS1, two main components of the defense-gene activation observed, revealed that E. amylovora multiplied ten times more in the eds1-2 mutant than in the wild type but not in the ndr1-1 mutant. Analysis of mutants affected in three WRKY transcription factors showing EDS1-dependent activation identified WRKY46 and WRKY54 as positive regulators and WRKY70 as a negative regulator of defense against E. amylovora. Altogether, we show that EDS1 is a positive regulator of nonhost resistance against E. amylovora in A. thaliana and hypothesize that it controls the production of several effective defenses against E. amylovora through the action of WRKY46 and WRKY54, while WRKY70 acts as a negative regulator. © 2012 The American Phytopathological Society.


Jay F.,University of Strasbourg | Jay F.,ETH Zurich | Wang Y.,Helmholtz Center for Environmental Research | Yu A.,Unite de Recherche en Genomique Vegetale | And 10 more authors.
PLoS Pathogens | Year: 2011

In Arabidopsis, micro (mi)RNAs and trans-acting (ta-si)RNAs synthesized directly or indirectly through the DICER-LIKE-1 (DCL1) ribonuclease have roles in patterning and hormonal responses, while DCL2,3,4-dependent small-interfering (si)RNAs are mainly involved in silencing of transposable elements and antiviral defense. Viral suppressors of RNA silencing (VSRs) produced by phytoviruses to counter plant defense may perturb plant developmental programs because of the collision of their inhibitory effects with the regulatory action of endogenous miRNAs and ta-siRNAs. This could explain the similar developmental aberrations displayed by Arabidopsis miRNA/ta-siRNA pathway mutants, including dcl1, and by some VSR-expressing plants. Nonetheless, the molecular bases for these morphological aberrations have remained mysterious, and their contribution to viral disease symptoms/virulence unexplored. The extent of VSR inhibitory actions to other types of endogenous small RNAs remains also unclear. Here, we present an in-depth analysis of transgenic Arabidopsis expressing constitutively HcPro, P19 and P15, three unrelated VSRs. We show that VSR expression has comparable, yet modest effects on known miRNA and ta-siRNA target RNA levels, similar to those observed using an hypomorphic dcl1 mutation. However, by combining results of transcriptome studies with deep-sequencing data from immuno-precipitated small RNAs, additional, novel endogenous targets of miRNA and ta-siRNA were identified, unraveling an unsuspected complexity in the origin and scope-of-action of these molecules. Other stringent analyses pinpointed misregulation of the miR167 target AUXIN RESPONSE FACTOR 8 (ARF8) as a major cause for the developmental aberrations exhibited by VSR transgenic plants, but also for the phenotypes induced during normal viral infection caused by the HcPro-encoding Turnip mosaic virus (TuMV). Neither RNA silencing, its suppression by VSRs, nor the virulence/accumulation of TuMV was altered by mutations in ARF8. These findings have important implications for our understanding of viral disease symptoms and small RNA-directed regulation of plant growth/development. © 2011 Jay, et al.


PubMed | University of Tübingen, Justus Liebig University, French National Institute for Agricultural Research and Unite de Recherche en Genomique Vegetale
Type: | Journal: Frontiers in microbiology | Year: 2014

Salmonella is one of the most prominent causes of food poisoning and growing evidence indicates that contaminated fruits and vegetables are an increasing concern for human health. Successful infection demands the suppression of the host immune system, which is often achieved via injection of bacterial effector proteins into host cells. In this report we present the function of Salmonella effector protein in plant cell, supporting the new concept of trans-kingdom competence of this bacterium. We screened a range of Salmonella Typhimurium effector proteins for interference with plant immunity. Among these, the phosphothreonine lyase SpvC attenuated the induction of immunity-related genes when present in plant cells. Using in vitro and in vivo systems we show that this effector protein interacts with and dephosphorylates activated Arabidopsis Mitogen-activated Protein Kinase 6 (MPK6), thereby inhibiting defense signaling. Moreover, the requirement of Salmonella SpvC was shown by the decreased proliferation of the spvC mutant in Arabidopsis plants. These results suggest that some Salmonella effector proteins could have a conserved function during proliferation in different hosts. The fact that Salmonella and other Enterobacteriaceae use plants as hosts strongly suggests that plants represent a much larger reservoir for animal pathogens than so far estimated.


Hudik E.,University Paris - Sud | Hudik E.,King Abdullah University of Science and Technology | Yoshioka Y.,Nagoya University | Domenichini S.,University Paris - Sud | And 12 more authors.
Plant Physiology | Year: 2014

The majority of research on cell cycle regulation is focused on the nuclear events that govern the replication and segregation of the genome between the two daughter cells. However, eukaryotic cells contain several compartmentalized organelles with specialized functions, and coordination among these organelles is required for proper cell cycle progression, as evidenced by the isolation of several mutants in which both organelle function and overall plant development were affected. To investigate how chloroplast dysfunction affects the cell cycle, we analyzed the crumpled leaf (crl) mutant of Arabidopsis (Arabidopsis thaliana), which is deficient for a chloroplastic protein and displays particularly severe developmental defects. In the crl mutant, we reveal that cell cycle regulation is altered drastically and that meristematic cells prematurely enter differentiation, leading to reduced plant stature and early endoreduplication in the leaves. This response is due to the repression of several key cell cycle regulators as well as constitutive activation of stress-response genes, among them the cell cycle inhibitor SIAMESE-RELATED5. One unique feature of the crl mutant is that it produces aplastidic cells in several organs, including the root tip. By investigating the consequence of the absence of plastids on cell cycle progression, we showed that nuclear DNA replication occurs in aplastidic cells in the root tip, which opens future research prospects regarding the dialogue between plastids and the nucleus during cell cycle regulation in higher plants. © 2014 American Society of Plant Biologists. All Rights Reserved.

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