Jean Vidal
University of Paris
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Trends in Plant Science | 1997
Jean Vidal; Raymond Chollet
PEP carboxylase is of paramount importance in plant metabolism, and is one of only a few enzymes known to undergo regulatory phosphorylation in the living plant. In illuminated leaves of C 4 species, a complex light-signal transduction cascade occurs, which possibly involves cross-talk between the two neighboring photosynthetic cell types. This process upregulates the activity of a Ca 2+ -independent, substrate-specific protein-Ser/Thr kinase, and thereby increases the phosphorylation state of the photosynthesis-related, C 4 PEP carboxylase isoform. This reversible covalent modification is superimposed on the opposing regulation of PEP carboxylase by carboxylic acids and phosphorylated metabolites, and is critical for the coordination and functioning of C 4 photosynthesis. The general occurrence of PEP carboxylase-kinase and the conserved N-terminal phosphorylation domain of the various plant PEP carboxylase isoforms support the hypothesis that similar regulatory mechanisms are functional in the diverse physiological contexts involving this enzyme.
Plant Science | 1994
Loïc Lepiniec; Jean Vidal; Raymond Chollet; Pierre Gadal; Claude Crétin
Abstract Plant phosphoenolpyruvate carboxylase (EC 4.1.1.31; PEPC) is encoded by a small multigene family in which the expression of each member is controlled individually by exogenous (light, environmental) and/or endogenous (hormonal and developmental) stimuli. The involvement of putative trans-actig factors and consensus cis-elements of promoters in the specific transcriptional regulation of the PEPC genes is discussed. At the post-translational level, the regulatory strategy of the plant enzyme is mainly to offset the negative effect of the feedback inhibitor, L-malate, the end-product of the oxaloacetate reduction. All plant PEPC-forms are under positive and negative allosteric control by metabolite effectors and possess a consensus phosphorylation site containing a target serine residue near their N-terminus (e.g. Ser8 in C4 PEPC from sorghum). In C4 and Crassulacean acid metabolism (CAM) plants, a complex signal-transduction chain activates a Ca2+-independent protein-serine kinase responsible for regulatory phosphorylation of PEPC. A more thorough understanding of the functional and regulatory properties of the bacterial and C4 enzymes has emerged by exploiting recombinant proteins and site-directed mutagenesis. In these newly opened areas, PEPC offers one of the best characterized paradigms of plant signaling. Finally, some emerging ideas on the evolution and phylogenetic relationships of the various PEPC isoforms are presented.
FEBS Letters | 1978
Jean-Pierre Jacquot; Jean Vidal; Pierre Gadal; Peter Schürmann
Thioredoxin, a small molecular weight protein, functioning as hydrogen carrier in DNA synthesis has recently been identified to be an indispensable factor in the light activation of certain regulatory enzymes of plant chloroplasts [l] . In the presence of thioredoxin and ferredoxin-thioredoxin reductase, photochemically-reduced ferredoxin is able to activate enzymeglike NADP malate dehydrogenase [2] and fructose 1,6-bisphosphatase (FBPase) [3] , both enzymes restricted to the chloroplasts [3,4]. In vitro reduced ferredoxin and ferredoxin-thioredoxin reductase can be replaced by the non-physiological sulfhydryl reagent dithiothreitol (DTT), thus eliminating the need for light, but not the need for thioredoxin [3,5,6] . During our efforts to isolate and purify thioredoxin from different plant species (spinach, sorghum and French beans) and plant materials (leaves and roots) we have realized that there are several forms of thioredoxin which are specific for the activation of either NADP malate dehydrogenase or FBPase. Similar findings have recently been reported by [7] . We describe here a simple method for the separation of different forms of thioredoxin which is applicable to various plant materials. In addition our results indicate that the different forms of thioredoxin are enzyme specific. However a given form of thioredoxin isolated from one plant species can activate the respective enzyme isolated from another plant species and vice versa.
Functional Plant Biology | 2004
Annick Moing; Mickaël Maucourt; Christel Renaud; Monique Gaudillère; Renaud Brouquisse; Bénédicte Lebouteiller; Aurélie Gousset-Dupont; Jean Vidal; David Granot; Béatrice Denoyes-Rothan; Estelle Lerceteau-Köhler; Dominique Rolin
Metabolic profiling by 1-dimensional (1-D) 1H-nuclear magnetic resonance (NMR) was tested for absolute quantification of soluble sugars, organic acids, amino acids and some secondary metabolites in fruit, roots and leaves. The metabolite responsible for each peak of the 1H-NMR spectra was identified from spectra of pure compounds. Peak identity was confirmed by the addition of a small amount of commercially-available pure substance. 1H-NMR spectra acquisition was automated. 1H-NMR absolute quantification was performed with a synthesised electronic reference signal and validated by comparison with enzymatic or HPLC analyses; the correlation coefficients between 1H-NMR data and enzymatic or HPLC data were highly significant. Depending on the species and tissues, 14-17 metabolites could be quantified with 15-25 min acquisition time. The detection limit was approximately 1-9 µg in the NMR tube, depending on the compound. Quantitative data were used for (1) a genetic study of strawberry fruit quality, (2) a functional study of tomato transformants overexpressing hexokinase and (3) a study of Arabidopsis phosphoenolpyruvate carboxylase transformants with several lines showing decreased activity of the enzyme. Biochemical phenotyping of the fruits of a strawberry offspring allowed the detection of quantitative trait loci (QTL) controlling fruit quality. Comparison of the roots of wild types and hexokinase tomato transformants using principal component analysis of metabolic profiles revealed that environmental factors, i.e. culture conditions, can significantly modify the metabolic status of plants and thus hide or emphasise the expression of a given genetic background. The decrease in phosphoenolpyruvate carboxylase activity (up to 75%) in Arabidopsis transformants impacted on the metabolic profiles without compromising plant growth, thus supporting the idea that the enzyme has a low influence on the carbon flux through the anaplerotic pathway.
The Plant Cell | 1996
Nathalie Giglioli-Guivarc'h; Jean-Noël Pierre; Spencer Brown; Raymond Chollet; Jean Vidal; Pierre Gadal
Phosphoenolpyruvate carboxylase (PEPC) was characterized in extracts from C4 mesophyll protoplasts isolated from Digitaria sanguinalis leaves and shown to display the structural, functional, and regulatory properties typical of a C4 PEPC. In situ increases in the apparent phosphorylation state of the enzyme and the activity of its Ca2+-independent protein-serine kinase were induced by light plus NH4Cl or methylamine. The photosynthesis-related metabolite 3-phosphoglycerate (3-PGA) was used as a substitute for the weak base in these experiments. The early effects of light plus the weak base or 3-PGA treatment were alkalinization of protoplast cytosolic pH, shown by fluorescence cytometry, and calcium mobilization from vacuoles, as suggested by the use of the calcium channel blockers TMB-8 and verapamil. The increases in PEPC kinase activity and the apparent phosphorylation state of PEPC also were blocked in situ by the electron transport and ATP synthesis inhibitors DCMU and gramicidin, respectively, the calcium/calmodulin antagonists W7, W5, and compound 48/80, and the cytosolic protein synthesis inhibitor cycloheximide. These results suggest that the production of ATP and/or NADPH by the illuminated mesophyll chloroplast is required for the activation of the transduction pathway, which presumably includes an upstream Ca2+-dependent protein kinase and a cytosolic protein synthesis event. The collective data support the view that the C4 PEPC light transduction pathway is contained entirely within the mesophyll cell and imply cross-talk between the mesophyll and bundle sheath cells in the form of the photosynthetic metabolite 3-PGA.
Proceedings of the National Academy of Sciences of the United States of America | 2010
Ana Belen Feria Bourrellier; Benoît Valot; Alain Guillot; F. Ambard-Bretteville; Jean Vidal; Michael Hodges
The PII protein is a signal integrator involved in the regulation of nitrogen metabolism in bacteria and plants. Upon sensing of cellular carbon and energy availability, PII conveys the signal by interacting with target proteins, thereby modulating their biological activity. Plant PII is located to plastids; therefore, to identify new PII target proteins, PII-affinity chromatography of soluble extracts from Arabidopsis leaf chloroplasts was performed. Several proteins were retained only when Mg-ATP was present in the binding medium and they were specifically released from the resin by application of a 2-oxoglutarate-containing elution buffer. Mass spectroscopy of SDS/PAGE-resolved protein bands identified the biotin carboxyl carrier protein subunits of the plastidial acetyl-CoA carboxylase (ACCase) and three other proteins containing a similar biotin/lipoyl-binding motif as putative PII targets. ACCase is a key enzyme initiating the synthesis of fatty acids in plastids. In in vitro reconstituted assays supplemented with exogenous ATP, recombinant Arabidopsis PII inhibited chloroplastic ACCase activity, and this was completely reversed in the presence of 2-oxoglutarate, pyruvate, or oxaloacetate. The inhibitory effect was PII-dose-dependent and appeared to be PII-specific because ACCase activity was not altered in the presence of other tested proteins. PII decreased the Vmax of the ACCase reaction without altering the Km for acetyl-CoA. These data show that PII function has evolved between bacterial and plant systems to control the carbon metabolism pathway of fatty acid synthesis in plastids.
Proceedings of the National Academy of Sciences of the United States of America | 1991
Jin-an Jiao; Cristina Echevarría; Jean Vidal; Raymond Chollet
Maize leaf phosphoenolpyruvate carboxylase [PEPC; orthophosphate:oxaloacetate carboxy-lyase (phosphorylating), EC 4.1.1.31] protein-serine kinase (PEPC-PK) phosphorylates serine-15 of its target enzyme, thus leading to an increase in catalytic activity and a concomitant decrease in malate sensitivity of this cytoplasmic C4 photosynthesis enzyme in the light. We have recently demonstrated that the PEPC-PK activity in maize leaves is slowly, but strikingly, increased in the light and decreased in darkness. In this report, we provide evidence that cycloheximide, an inhibitor of cytoplasmic protein synthesis, when fed to detached leaves of C4 monocots (maize, sorghum) and dicots (Portulaca oleracea) in the dark or light, completely prevents the in vivo light activation of PEPC-PK activity regardless of whether the protein kinase activity is assessed in vivo or in vitro. In contrast, chloramphenicol, an inhibitor of protein synthesis in chloroplasts, has no effect on the light activation of maize PEPC-PK. Similarly, treatment with cycloheximide did not influence the light activation of other photosynthesis-related enzymes in maize, including cytoplasmic sucrose-phosphate synthase and chloroplast stromal NADPH-malate dehydrogenase and pyruvate, Pi dikinase. These and related results, in which detached maize leaves were treated simultaneously with cycloheximide and microcystin-LR, a potent in vivo and in vitro inhibitor of the PEPC type 2A protein phosphatase, indicate that short-term protein turnover of the PEPC-PK itself or some other essential component(s) (e.g., a putative protein that modifies this kinase activity) is one of the primary levels in the complex and unique regulatory cascade effecting the reversible light activation/seryl phosphorylation of PEPC in the mesophyll cytoplasm of C4 plants.
Plant Molecular Biology | 2002
Fabienne Corre-Menguy; Francisco Javier Cejudo; Christelle Mazubert; Jean Vidal; Christine Lelandais-Brière; Gisele A.M. Torres; A. Rode; Caroline Hartmann
A cDNA coding for phytocystatin, a protease inhibitor, was isolated from wheat embryos by differential display RT-PCR and the corresponding full-length cDNA (named WC5 for wheat cystatin gene 5) subsequently obtained by RACE. The deduced primary sequence of the protein suggests the presence of a 28 amino acid N-terminal signal sequence and a 100 amino acid mature protein containing the three consensus motifs known to interact with the active site of cysteine peptidases. Northern and western analysis revealed a spatio-temporal pattern of the cystatin gene expression during caryopse development. In the embryo, WC5 was only expressed during early embryogenesis whereas, in seed covering layers, WC5 expression was restricted to the maturation stage of grain development. In addition, immunolocalization experiments showed that cystatin accumulated in the aleurone layer of the maturating seed and in the parenchymal tissues of the embryo scutellum. A recombinant form of the wheat cystatin was shown to be able to inhibit peptidase activities present in whole seed protein extracts. In addition, immunological techniques allowed us to identify two putative target peptidases. The possible roles of the cystatin protein are discussed in relation with tissular localization and putative peptidase targets during seed maturation.
FEBS Letters | 1980
Jean Vidal; Guy Godbillon; Pierre Gadal
Since its discovery in 1953 [ 11, PEP carboxylase (orthophosphate:oxaloacetate carboxylase, EC 4.1 -1.3 1) has been the subject of numerous studies. Indeed, the carboxylase, which is ubiquitous among bacteria and plants, represents a means of incorporating inorganic carbon in a non-photosynthetic way. It has been implicated in numerous physiological roles such as, anaplerotic pathways [2], Cq photosynthesis and crassulacean acid metabolism [3,4], stomata1 aperture [5], ionic equilibrium in root cells [6], pH stat [7] and biological rhythms [8]. A number of isoenzymes of PEP carboxylase have been reported [9-l 31. Many experiments have been and are being performed on the functional and regulatory properties of the enzyme and on its localization in cells and tissues [ 141. We have been concerned with the purification of PEP carboxylase isoforms in bean and sorghum leaves and roots [ 15 ,161. Immunochemical techniques provide an efficient method for enzyme purification and localization; unfortunately such techniques usually result in the complete loss of biological activity. Here we describe a new and simple method based on the elution of an active, highly purified enzyme from an immunoadsorbent column.
Biochemical and Biophysical Research Communications | 1986
Jeanne Brulfert; Jean Vidal; P. Le Maréchal; Pierre Gadal; O. Queiroz; M. Kluge; I. Kruger
Day and night forms of phosphoenolpyruvate carboxylase (EC 4.1.1.31) (PEPC) were extracted from leaves of the CAM plants Kalanchoe daigremontiana, K. tubiflora and K. blossfeldiana previously fed with [32P] labelled phosphate solution. A one-step immunochemical purification followed by SDS polyacrylamide gel electrophoresis and autoradiography showed that, in all species, the night form of the enzyme was phosphorylated and not the day form. Limited acid hydrolysis of the night form and two-dimensional separation identified predominantly labelled phosphoserine and phosphothreonine. In vitro addition of exogenous acid phosphatase (EC 3.1.3.2) to desalted night form-containing extracts resulted within 30 min in a shift in PEPC enzymic properties similar to the in vivo changes from night to day form. It is suggested that phosphorylation-dephosphorylation of the enzyme could be the primary in vivo process which might explain the observed rhythmicity of enzymic properties.