Jean-Claude Mollet

Scopus Publications

Additive and Specific Effects of Elicitor Treatments on the Metabolic Profile of Arabidopsis thaliana
Lisa Cabre, Lun Jing, Moffat Makechemu, Kylhan Heluin, Sarah El Khamlichi, Jérôme Leprince, Marie Christine Kiefer-Meyer, Sylvain Pluchon, Jean-Claude Mollet, Cyril Zipfel,et al.
Scientific Societies
Several elicitors of plant defense have been identified and numerous efforts to use them in the field have been made. Exogenous elicitor treatments mimic the in planta activation of pattern-triggered immunity (PTI), which relies on the perception of pathogen-associated molecular patterns (PAMPs) such as bacterial flg22 or fungal chitins. Early transcriptional responses to distinct PAMPs are mostly overlapping, regardless of the elicitor being used. However, it remains poorly known if the same patterns are observed for metabolites and proteins produced later during PTI. In addition, little is known about the impact of a combination of elicitors on PTI and the level of induced resistance to pathogens. Here, we monitored Arabidopsis thaliana resistance to the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 ( Pto DC3000) following application of flg22 and chitosan elicitors, used individually or in combination. A slight, but not statistically significant increase in induced resistance was observed when the elicitors were applied together when compared with individual treatments. We investigated the effect of these treatments on the metabolome by using an untargeted analysis. We found that the combination of flg22 and chitosan impacted a higher number of metabolites and deregulated specific metabolic pathways compared with the elicitors individually. These results contribute to a better understanding of plant responses to elicitors, which might help better rationalize their use in the field. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Subcellular localization of core beta(1,2)-xylosylated N-glycoproteins in the green microalgae Chlamydomonas reinhardtii
M. Ropitaux, S. Bernard, I. Boulogne, D. Goux, J.-C. Mollet, P. Lerouge, M. Bardor, and N. Mati-Baouche
Elsevier BV

The Light-Controlled Release of 2-fluoro-l-fucose, an Inhibitor of the Root Cell Elongation, from a nitrobenzyl-caged Derivative
Mathieu Carlier, Thomas Poisson, Jean-Claude Mollet, Patrice Lerouge, Cyrille Sabot, and Arnaud Lehner
MDPI AG
Glycan metabolic engineering is a powerful tool for studying the glycosylation in living plant cells. The use of modified monosaccharides such as deoxy or fluorine-containing glycosides has been reported as a powerful pharmacological approach for studying the carbohydrate metabolism. 1,3,4-tri-O-acetyl-2-fluoro-l-fucose (2F-Fuc) is a potent inhibitor of the plant cell elongation. After feeding plant seedlings with 2F-Fuc, this monosaccharide derivative is deacetylated and converted by the endogenous metabolic machinery into the corresponding nucleotide-sugar, which then efficiently inhibits Golgi-localized fucosyltransferases. Among plant cell wall polymers, defects in the fucosylation of the pectic rhamnogalacturonan-II cause a decrease in RG-II dimerization, which in turn induce the arrest of the cell elongation. In order to perform the inhibition of the cell elongation process in a spatio-temporal manner, we synthesized a caged 3,4-di-O-acetyl-1-hydroxy-2-fluoro-l-fucose (1-OH-2F-Fuc) derivative carrying a photolabile ortho-nitrobenzyl alcohol function at the anomeric position: 3,4-di-O-acetyl-1-ortho-nitrobenzyl-2-fluoro-l-fucose (2F-Fuc-NB). The photorelease of the trapped 1-OH-2F-Fuc was performed under a 365 nm LED illumination. We demonstrated that the in planta elimination by photoexcitation of the photolabile group releases free 2F-Fuc in plant cells, which in turn inhibits in a dose-dependent manner and, reversibly, the root cell elongation.

Pollen viability, longevity, and function in angiosperms: key drivers and prospects for improvement
Rasha Althiab-Almasaud, Eve Teyssier, Christian Chervin, Mark A. Johnson, and Jean-Claude Mollet
Springer Science and Business Media LLC

Rapid evolution of pollen and pistil traits as a response to sexual selection in the post-pollination phase of mating
Jeanne Tonnabel, Pascal Cosette, Arnaud Lehner, Jean-Claude Mollet, Mohamed Amine Ben Mlouka, Lucija Grladinovic, Patrice David, and John R. Pannell
Elsevier BV

Dynamic imaging of cell wall polysaccharides by metabolic click-mediated labeling of pectins in living elongating cells
Marc Ropitaux, Quentin Hays, Aurélie Baron, Laura Fourmois, Isabelle Boulogne, Boris Vauzeilles, Patrice Lerouge, Jean‐Claude Mollet, and Arnaud Lehner
Wiley
Investigation of protein tracking in living plant cells has became a routine experiment with the emergence of reporter genes encoding fluorescent tags. Unfortunately, this imaging strategy is not applicable to glycans because their synthesis is not directly encoded by the genome. Indeed, complex glycans result from sequential additions and/or removals of monosaccharides by the glycosyltransferases and glycosidases of the cell's biosynthetic machinery. To date, the imaging of cell wall polymers mainly relies on the use of antibodies or dyes that exhibit variable specificities. However, as immunolocalisation typically requires sample fixation, it does not provide access to the dynamics of living cells. The development of click chemistry in plant cell wall biology offers an alternative for live-cell labelling. It consists of the incorporation of a carbohydrate containing a bio-orthogonal chemical reporter into the target polysaccharide using the endogenous biosynthetic machinery of the cell. Once synthesized and deposited in the cell wall, the polysaccharide containing the analogue monosaccharide is covalently coupled to an exogenous fluorescent probe. Here, we developed a metabolic-click labelling approach which allows the imaging of cell wall polysaccharides in living and elongating cells without affecting cell viability. The protocol was established using the pollen tube, a useful model to follow cell wall dynamics due to its fast and tip-polarized growth, but was also successfully tested on Arabidopsis root cells and root hairs. This method offers the possibility of imaging metabolically incorporated sugars of viable and elongating cells, allowing the study of the long-term dynamics of labelled extracellular polysaccharides.

The cell wall pectic rhamnogalacturonan II, an enigma in plant glycobiology
Patrice Lerouge, Mathieu Carlier, Jean-Claude Mollet, and Arnaud Lehner
Royal Society of Chemistry

Two Carbohydrate-Based Natural Extracts Stimulate in vitro Pollen Germination and Pollen Tube Growth of Tomato Under Cold Temperatures
Ferdousse Laggoun, Nusrat Ali, Sabine Tourneur, Grégoire Prudent, Bruno Gügi, Marie-Christine Kiefer-Meyer, Alain Mareck, Florence Cruz, Jean-Claude Yvin, Eric Nguema-Ona,et al.
Frontiers Media SA
To date, it is widely accepted by the scientific community that many agricultural regions will experience more extreme temperature fluctuations. These stresses will undoubtedly impact crop production, particularly fruit and seed yields. In fact, pollination is considered as one of the most temperature-sensitive phases of plant development and until now, except for the time-consuming and costly processes of genetic breeding, there is no immediate alternative to address this issue. In this work, we used a multidisciplinary approach using physiological, biochemical, and molecular techniques for studying the effects of two carbohydrate-based natural activators on in vitro tomato pollen germination and pollen tube growth cultured in vitro under cold conditions. Under mild and strong cold temperatures, these two carbohydrate-based compounds significantly enhanced pollen germination and pollen tube growth. The two biostimulants did not induce significant changes in the classical molecular markers implicated in pollen tube growth. Neither the number of callose plugs nor the CALLOSE SYNTHASE genes expression were significantly different between the control and the biostimulated pollen tubes when pollens were cultivated under cold conditions. PECTIN METHYLESTERASE (PME) activities were also similar but a basic PME isoform was not produced or inactive in pollen grown at 8°C. Nevertheless, NADPH oxidase (RBOH) gene expression was correlated with a higher number of viable pollen tubes in biostimulated pollen tubes compared to the control. Our results showed that the two carbohydrate-based products were able to reduce in vitro the effect of cold temperatures on tomato pollen tube growth and at least for one of them to modulate reactive oxygen species production.

Ethylene signaling modulates tomato pollen tube growth through modifications of cell wall remodeling and calcium gradient
Rasha Althiab‐Almasaud, Yi Chen, Elie Maza, Anis Djari, Pierre Frasse, Jean‐Claude Mollet, Christian Mazars, Elisabeth Jamet, and Christian Chervin
Wiley
Ethylene modulates plant developmental processes including flower development. Previous studies have suggested ethylene participation in pollen tube (PT) elongation, and both ethylene production and perception seem critical at fertilization time. The full gene set regulated by ethylene during PT growth is unknown. To study this, we used various EThylene Receptors (ETRs) tomato mutants: etr3-ko, a loss-of-function (LOF) mutant; and NR (Never Ripe), a gain of function (GOF) mutant. The etr3-ko PTs grew faster than its wild type, WT. Oppositely, NR PT elongation was slower than its wild type, and PTs displayed larger diameters. ETR mutations created feedbacks on ethylene production. Furthermore, the ethylene treatment of germinating pollen grains increased PT length in etr-ko mutants and WT, but not in NR. Treatments with the ethylene perception inhibitor, 1-MCP, decreased PT length in etr-ko mutants and wild types, but had no effect on NR. This confirmed that ethylene regulates PT growth. The comparison of PT transcriptomes in LOF and GOF mutants, etr3-ko and NR, both mutated on the ETR3 gene, revealed that ethylene perception has major impacts on cell wall- and calcium-related genes as confirmed by microscopic observations showing a modified distribution of the methylesterified homogalacturonan pectic motif and of calcium load. Our results establish links between PT growth, ethylene, calcium and cell wall metabolisms, and also constitute a transcriptomic resource.

The Scope for Postmating Sexual Selection in Plants
Jeanne Tonnabel, Patrice David, Tim Janicke, Arnaud Lehner, Jean-Claude Mollet, John R. Pannell, and Mathilde Dufay
Elsevier BV

Effect of a Bacillus subtilis strain on flax protection against Fusarium oxysporum and its impact on the root and stem cell walls
Aline Planchon, Gaëlle Durambur, Jean‐Baptiste Besnier, Carole Plasson, Bruno Gügi, Sophie Bernard, Annabelle Mérieau, Jean‐Paul Trouvé, Caroline Dubois, Karine Laval,et al.
Wiley
In Normandy, flax is a plant of important economic interest because of its fibers. Fusarium oxysporum, a telluric fungus, is responsible for the major losses in crop yield and fiber quality. Several methods are currently used to limit the use of phytochemicals on crops. One of them is the use of Plant Growth Promoting Rhizobacteria (PGPR) occurring naturally in the rhizosphere. PGPR are known to act as local antagonists to soil-borne pathogens and to enhance plant resistance by eliciting the Induced Systemic Resistance (ISR). In this study, we first investigated the cell wall modifications occurring in roots and stems after inoculation with the fungus in two flax varieties. First, we showed that both varieties displayed different cell wall organization and that rapid modifications occurred in roots and stems after inoculation. Then, we demonstrated the efficiency of a Bacillus subtilis strain to limit Fusarium wilt on both varieties with a better efficiency for one of them. Finally, thermo-gravimetry was used to highlight that B. subtilis induced modifications of the stem properties, supporting a reinforcement of the cell walls. Our findings suggest that the efficiency and the mode of action of the PGPR B. subtilis is likely to be flax variety-dependent. This article is protected by copyright. All rights reserved.

Identification of two compounds able to improve flax resistance towards Fusarium oxysporum infection
Rim Jaber, Aline Planchon, Elodie Mathieu-Rivet, Marie-Christine Kiefer-Meyer, Abderrakib Zahid, Carole Plasson, Olivier Pamlard, Sandra Beaupierre, Jean-Paul Trouvé, Catherine Guillou,et al.
Elsevier BV

The exogenous application of AtPGLR, an endo-polygalacturonase, triggers pollen tube burst and repair
Ludivine Hocq, Sophie Guinand, Olivier Habrylo, Aline Voxeur, Wafae Tabi, Josip Safran, Françoise Fournet, Jean‐Marc Domon, Jean‐Claude Mollet, Serge Pilard,et al.
Wiley
Plant cell wall remodeling plays a key role in the control of cell elongation and differentiation. In particular, the fine-tuning of the degree of methylesterification of pectins was previously reported to control developmental processes as diverse as pollen germination, pollen tube elongation, primordia emergence or dark-grown hypocotyl elongation. How pectin degradation can modulate plant development has however remained elusive. Here, we report the characterization of a polygalacturonase (PG), AtPGLR, which gene is highly expressed at the onset of lateral root emergence in Arabidopsis. Due to gene compensation mechanisms, mutant approaches failed to determine the involvement of AtPGLR in plant growth. To overcome this issue, AtPGLR has been expressed heterologously in the yeast Pichia pastoris and biochemically characterized. We showed that AtPGLR is an endo-PG that preferentially releases non-methylesterified oligogalacturonides of short degree of polymerization (<8) at acidic pH. The application of the purified recombinant protein on Amaryllis pollen tubes, an excellent model to study cell wall remodeling at acidic pH, induced abnormal pollen tubes or cytoplasmic leakage in the sub-apical dome of the pollen tube tip, where non-methylesterified pectin epitopes are detected. Those leaks could either be repaired by new β-glucan deposits (mostly callose) in the cell wall or promoted dramatic burst of the pollen tube. Our work presents the full biochemical characterization of an Arabidopsis PG and highlights the importance of pectin integrity in pollen tube elongation.

A chemical screen identifies two novel small compounds that alter Arabidopsis thaliana pollen tube growth
Ferdousse Laggoun, Flavien Dardelle, Jérémy Dehors, Denis Falconet, Azeddine Driouich, Christophe Rochais, Patrick Dallemagne, Arnaud Lehner, and Jean-Claude Mollet
Springer Science and Business Media LLC

Evolution of cell wall polymers in tip-growing land plant gametophytes: Composition, distribution, functional aspects and their remodeling
Jérémy Dehors, Alain Mareck, Marie-Christine Kiefer-Meyer, Laurence Menu-Bouaouiche, Arnaud Lehner, and Jean-Claude Mollet
Frontiers Media SA
During evolution of land plants, the first colonizing species presented leafy-dominant gametophytes, found in non-vascular plants (bryophytes). Today, bryophytes include liverworts, mosses, and hornworts. In the first seedless vascular plants (lycophytes), the sporophytic stage of life started to be predominant. In the seed producing plants, gymnosperms and angiosperms , the gametophytic stage is restricted to reproduction. In mosses and ferns, the haploid spores germinate and form a protonema, which develops into a leafy gametophyte producing rhizoids for anchorage, water and nutrient uptakes. The basal gymnosperms (cycads and Ginkgo) reproduce by zooidogamy. Their pollen grains develop a multi-branched pollen tube that penetrates the nucellus and releases flagellated sperm cells that swim to the egg cell. The pollen grain of other gymnosperms (conifers and gnetophytes) as well as angiosperms germinates and produces a pollen tube that directly delivers the sperm cells to the ovule (siphonogamy). These different gametophytes, which are short or long-lived structures, share a common tip-growing mode of cell expansion. Tip-growth requires a massive cell wall deposition to promote cell elongation, but also a tight spatial and temporal control of the cell wall remodeling in order to modulate the mechanical properties of the cell wall. The growth rate of these cells is very variable depending on the structure and the species, ranging from very slow (protonemata, rhizoids, and some gymnosperm pollen tubes), to a slow to fast-growth in other gymnosperms and angiosperms. In addition, the structural diversity of the female counterparts in angiosperms (dry, semi-dry vs wet stigmas, short vs long, solid vs hollow styles) will impact the speed and efficiency of sperm delivery. As the evolution and diversity of the cell wall polysaccharides accompanied the diversification of cell wall structural proteins and remodeling enzymes, this review focuses on our current knowledge on the biochemistry, the distribution and remodeling of the main cell wall polymers (including cellulose, hemicelluloses, pectins, callose, arabinogalactan-proteins and extensins), during the tip-expansion of gametophytes from bryophytes, pteridophytes (lycophytes and monilophytes), gymnosperms and the monocot and eudicot angiosperms.

Desiccation tolerance in plants: Structural characterization of the cell wall hemicellulosic polysaccharides in three Selaginella species
Barbara Plancot, Bruno Gügi, Jean-Claude Mollet, Corinne Loutelier-Bourhis, Sharathchandra Ramasandra Govind, Patrice Lerouge, Marie-Laure Follet-Gueye, Maïté Vicré, Carlos Alfonso, Eric Nguema-Ona,et al.
Elsevier BV

TBL10 is required for O-acetylation of pectic rhamnogalacturonan-I in Arabidopsis thaliana
Maria Stranne, Yanfang Ren, Lorenzo Fimognari, Devon Birdseye, Jingwei Yan, Muriel Bardor, Jean‐Claude Mollet, Takanori Komatsu, Jun Kikuchi, Henrik V. Scheller,et al.
Wiley
O-Acetylated pectins are abundant in the primary cell wall of plants and growing evidence suggests they have important roles in plant cell growth and interaction with the environment. Despite their importance, genes required for O-acetylation of pectins are still largely unknown. In this study, we showed that TRICHOME BIREFRINGENCE LIKE 10 (AT3G06080) is involved in O-acetylation of pectins in Arabidopsis (Arabidopsis thaliana). The activity of the TBL10 promoter was strong in tissues where pectins are highly abundant (e.g. leaves). Two homozygous knock-out mutants of Arabidopsis, tbl10-1 and tbl10-2, were isolated and shown to exhibit reduced levels of wall-bound acetyl esters, equivalent of ~50% of the wild-type level in pectin-enriched fractions derived from leaves. Further fractionation revealed that the degree of acetylation of the pectin rhamnogalacturonan-I (RG-I) was reduced in the tbl10 mutant compared to the wild type, whereas the pectin homogalacturonan (HG) was unaffected. The degrees of acetylation in hemicelluloses (i.e. xyloglucan, xylan and mannan) were indistinguishable between the tbl10 mutants and the wild type. The mutant plants contained normal trichomes in leaves and exhibited a similar level of susceptibility to the phytopathogenic microorganisms Pseudomonas syringae pv. tomato DC3000 and Botrytis cinerea; while they displayed enhanced tolerance to drought. These results indicate that TBL10 is required for O-acetylation of RG-I, possibly as an acetyltransferase, and suggest that O-acetylated RG-I plays a role in abiotic stress responses in Arabidopsis.

Holaphyllamine, a steroid, is able to induce defense responses in Arabidopsis thaliana and increases resistance against bacterial infection
Abderrakib Zahid, Rim Jaber, Ferdousse Laggoun, Arnaud Lehner, Isabelle Remy-Jouet, Olivier Pamlard, Sandra Beaupierre, Jérome Leprince, Marie-Laure Follet-Gueye, Maïté Vicré-Gibouin,et al.
Springer Science and Business Media LLC

AtPME3, a ubiquitous cell wall pectin methylesterase of Arabidopsis thaliana, alters the metabolism of cruciferin seed storage proteins during post-germinative growth of seedlings
Stéphanie Guénin, Julie Hardouin, Florence Paynel, Kerstin Müller, Gaëlle Mongelard, Azeddine Driouich, Patrice Lerouge, Allison R. Kermode, Arnaud Lehner, Jean-Claude Mollet,et al.
Oxford University Press (OUP)
&NA; AtPME3 (At3g14310) is a ubiquitous cell wall pectin methylesterase. Atpme3‐1 loss‐of‐function mutants exhibited distinct phenotypes from the wild type (WT), and were characterized by earlier germination and reduction of root hair production. These phenotypical traits were correlated with the accumulation of a 21.5‐kDa protein in the different organs of 4‐day‐old Atpme3‐1 seedlings grown in the dark, as well as in 6‐week‐old mutant plants. Microarray analysis showed significant down‐regulation of the genes encoding several pectin‐degrading enzymes and enzymes involved in lipid and protein metabolism in the hypocotyl of 4‐day‐old dark grown mutant seedlings. Accordingly, there was a decrease in proteolytic activity of the mutant as compared with the WT. Among the genes specifying seed storage proteins, two encoding CRUCIFERINS were up‐regulated. Additional analysis by RT‐qPCR showed an overexpression of four CRUCIFERIN genes in the mutant Atpme3‐1, in which precursors of the &agr;‐ and &bgr;‐subunits of CRUCIFERIN accumulated. Together, these results provide evidence for a link between AtPME3, present in the cell wall, and CRUCIFERIN metabolism that occurs in vacuoles.

Combined experimental and computational approaches reveal distinct pH dependence of pectin Methylesterase Inhibitors
Ludivine Hocq, Fabien Sénéchal, Valérie Lefebvre, Arnaud Lehner, Jean-Marc Domon, Jean-Claude Mollet, Jérémy Dehors, Karine Pageau, Paulo Marcelo, François Guérineau,et al.
Oxford University Press (OUP)
The pH dependence of PMEI, proteins that fine-tune the activity of pectin methylesterases, can be predicted by molecular dynamics simulation and validated in vitro and on pollen tube development. The fine-tuning of the degree of methylesterification of cell wall pectin is a key to regulating cell elongation and ultimately the shape of the plant body. Pectin methylesterification is spatiotemporally controlled by pectin methylesterases (PMEs; 66 members in Arabidopsis [Arabidopsis thaliana]). The comparably large number of proteinaceous pectin methylesterase inhibitors (PMEIs; 76 members in Arabidopsis) questions the specificity of the PME-PMEI interaction and the functional role of such abundance. To understand the difference, or redundancy, between PMEIs, we used molecular dynamics (MD) simulations to predict the behavior of two PMEIs that are coexpressed and have distinct effects on plant development: AtPMEI4 and AtPMEI9. Simulations revealed the structural determinants of the pH dependence for the interaction of these inhibitors with AtPME3, a major PME expressed in roots. Key residues that are likely to play a role in the pH dependence were identified. The predictions obtained from MD simulations were confirmed in vitro, showing that AtPMEI9 is a stronger, less pH-independent inhibitor compared with AtPMEI4. Using pollen tubes as a developmental model, we showed that these biochemical differences have a biological significance. Application of purified proteins at pH ranges in which PMEI inhibition differed between AtPMEI4 and AtPMEI9 had distinct consequences on pollen tube elongation. Therefore, MD simulations have proven to be a powerful tool to predict functional diversity between PMEIs, allowing the discovery of a strategy that may be used by PMEIs to inhibit PMEs in different microenvironmental conditions and paving the way to identify the specific role of PMEI diversity in muro.

UUAT1 is a golgi-localized UDP-uronic acid transporter that modulates the polysaccharide composition of arabidopsis seed mucilage
Susana Saez-Aguayo, Carsten Rautengarten, Henry Temple, Dayan Sanhueza, Troy Ejsmentewicz, Omar Sandoval-Ibañez, Daniela Doñas, Juan Pablo Parra-Rojas, Berit Ebert, Arnaud Lehner,et al.
Oxford University Press (OUP)
Screening of Arabidopsis mutants with altered seed mucilage allowed identification of UUAT1, a Golgi-localized protein that transports UDP-glucuronic acid and plays a role in the biosynthesis of pectin. UDP-glucuronic acid (UDP-GlcA) is the precursor of many plant cell wall polysaccharides and is required for production of seed mucilage. Following synthesis in the cytosol, it is transported into the lumen of the Golgi apparatus, where it is converted to UDP-galacturonic acid (UDP-GalA), UDP-arabinose, and UDP-xylose. To identify the Golgi-localized UDP-GlcA transporter, we screened Arabidopsis thaliana mutants in genes coding for putative nucleotide sugar transporters for altered seed mucilage, a structure rich in the GalA-containing polysaccharide rhamnogalacturonan I. As a result, we identified UUAT1, which encodes a Golgi-localized protein that transports UDP-GlcA and UDP-GalA in vitro. The seed coat of uuat1 mutants had less GalA, rhamnose, and xylose in the soluble mucilage, and the distal cell walls had decreased arabinan content. Cell walls of other organs and cells had lower arabinose levels in roots and pollen tubes, but no differences were observed in GalA or xylose contents. Furthermore, the GlcA content of glucuronoxylan in the stem was not affected in the mutant. Interestingly, the degree of homogalacturonan methylation increased in uuat1. These results suggest that this UDP-GlcA transporter plays a key role defining the seed mucilage sugar composition and that its absence produces pleiotropic effects in this component of the plant extracellular matrix.

Salicylic Acid Regulates Pollen Tip Growth through an NPR3/NPR4-Independent Pathway
Duoyan Rong, Nan Luo, Jean Claude Mollet, Xuanming Liu, and Zhenbiao Yang
Elsevier BV

Two tomato GDP-D-mannose epimerase isoforms involved in ascorbate biosynthesis play specific roles in cell wall biosynthesis and development
Louise Mounet-Gilbert, Marie Dumont, Carine Ferrand, Céline Bournonville, Antoine Monier, Joana Jorly, Martine Lemaire-Chamley, Kentaro Mori, Isabelle Atienza, Michel Hernould,et al.
Oxford University Press (OUP)
Highlight The two tomato GDP-D-mannose epimerase isoforms play specific roles in cell wall biosynthesis and plant development but participate similarly in ascorbate biosynthesis.

Plant cell wall imaging by metabolic click-mediated labelling of rhamnogalacturonan II using azido 3-deoxy- d -manno-oct-2-ulosonic acid
Marie Dumont, Arnaud Lehner, Boris Vauzeilles, Julien Malassis, Alan Marchant, Kevin Smyth, Bruno Linclau, Aurélie Baron, Jordi Mas Pons, Charles T. Anderson,et al.
Wiley
In plants, 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) is a monosaccharide that is only found in the cell wall pectin, rhamnogalacturonan-II (RG-II). Incubation of 4-day-old light-grown Arabidopsis seedlings or tobacco BY-2 cells with 8-azido 8-deoxy Kdo (Kdo-N3 ) followed by coupling to an alkyne-containing fluorescent probe resulted in the specific in muro labelling of RG-II through a copper-catalysed azide-alkyne cycloaddition reaction. CMP-Kdo synthetase inhibition and competition assays showing that Kdo and D-Ara, a precursor of Kdo, but not L-Ara, inhibit incorporation of Kdo-N3 demonstrated that incorporation of Kdo-N3 occurs in RG-II through the endogenous biosynthetic machinery of the cell. Co-localisation of Kdo-N3 labelling with the cellulose-binding dye calcofluor white demonstrated that RG-II exists throughout the primary cell wall. Additionally, after incubating plants with Kdo-N3 and an alkynated derivative of L-fucose that incorporates into rhamnogalacturonan I, co-localised fluorescence was observed in the cell wall in the elongation zone of the root. Finally, pulse labelling experiments demonstrated that metabolic click-mediated labelling with Kdo-N3 provides an efficient method to study the synthesis and redistribution of RG-II during root growth.

Inhibition of fucosylation of cell wall components by 2-fluoro 2-deoxy- l -fucose induces defects in root cell elongation
Marie Dumont, Arnaud Lehner, Muriel Bardor, Carole Burel, Boris Vauzeilles, Olivier Lerouxel, Charles T. Anderson, Jean‐Claude Mollet, and Patrice Lerouge
Wiley
Screening of commercially available fluoro monosaccharides as putative growth inhibitors in Arabidopsis thaliana revealed that 2-fluoro 2-l-fucose (2F-Fuc) reduces root growth at micromolar concentrations. The inability of 2F-Fuc to affect an Atfkgp mutant that is defective in the fucose salvage pathway indicates that 2F-Fuc must be converted to its cognate GDP nucleotide sugar in order to inhibit root growth. Chemical analysis of cell wall polysaccharides and glycoproteins demonstrated that fucosylation of xyloglucans and of N-linked glycans is fully inhibited by 10 μm 2F-Fuc in Arabidopsis seedling roots, but genetic evidence indicates that these alterations are not responsible for the inhibition of root development by 2F-Fuc. Inhibition of fucosylation of cell wall polysaccharides also affected pectic rhamnogalacturonan-II (RG-II). At low concentrations, 2F-Fuc induced a decrease in RG-II dimerization. Both RG-II dimerization and root growth were partially restored in 2F-Fuc-treated seedlings by addition of boric acid, suggesting that the growth phenotype caused by 2F-Fuc was due to a deficiency of RG-II dimerization. Closer investigation of the 2F-Fuc-induced growth phenotype demonstrated that cell division is not affected by 2F-Fuc treatments. In contrast, the inhibitor suppressed elongation of root cells and promoted the emergence of adventitious roots. This study further emphasizes the importance of RG-II in cell elongation and the utility of glycosyltransferase inhibitors as new tools for studying the functions of cell wall polysaccharides in plant development. Moreover, supplementation experiments with borate suggest that the function of boron in plants might not be restricted to RG-II cross-linking, but that it might also be a signal molecule in the cell wall integrity-sensing mechanism.

Jean-Claude Mollet

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