Arabidopsis Phyllotaxis Is Controlled by the Methyl-Esterification Status of Cell-Wall Pectins

SummaryPlant organs are produced from meristems in a characteristic pattern. This pattern, referred to as phyllotaxis, is thought to be generated by local gradients of an information molecule, auxin [1–6]. Some studies propose a key role for the mechanical properties of the cell walls in the control of organ outgrowth [7–12]. A major cell-wall component is the linear α-1-4-linked D-GalAp pectic polysaccharide homogalacturonan (HG), which plays a key role in cell-to-cell cohesion [13, 14]. HG is deposited in the cell wall in a highly (70%–80%) methyl-esterified form and is subsequently de-methyl-esterified by pectin methyl-esterases (PME, EC 3.1.1.11). PME activity is itself regulated by endogenous PME inhibitor (PMEI) proteins [15]. PME action modulates cell-wall-matrix properties and plays a role in the control of cell growth [16–18]. Here, we show that the formation of flower primordia in the Arabidopsis shoot apical meristem is accompanied by the de-methyl-esterification of pectic polysaccharides in the cell walls. In addition, experimental perturbation of the methyl-esterification status of pectins within the meristem dramatically alters the phyllotactic pattern. These results demonstrate that regulated de-methyl-esterification of pectins is a key event in the outgrowth of primordia and possibly also in phyllotactic patterning

Effets de l'ozone et du dioxyde de carbone sur le système de détoxification et les protéines thylakoïdales des chloroplastes de germinations d'Epicéa

Notice présente dans BelInra (https://belinra.inra.fr/gestion/catalog.php?categ=isbd&id=180660)il s'agit d'un type de produit dont les métadonnées ne correspondent pas aux métadonnées attendues dans les autres types de produit : DISSERTATIONEffets de l'ozone et du dioxyde de carbone sur le système de détoxification et les protéines thylakoïdales des chloroplastes de germinations d'Epicé

Changes in Rubisco and Rubisco activase gene expression and polypeptide content in Pinus halepensis M. subjected to ozone and drought

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Arabidopsis PME17 Activity can be Controlled by Pectin Methylesterase Inhibitor4

International audienceThe degree of methylesterification (DM) of homogalacturonans (HGs), the main constituent of pectins in Arabidopsis thaliana, can be modified by pectin methylesterases (PMEs). Regulation of PME activity occurs through interaction with PME inhibitors (PMEIs) and subtilases (SBTs). Considering the size of the gene families encoding PMEs, PMEIs and SBTs, it is highly likely that specific pairs mediate localized changes in pectin structure with consequences on cell wall rheology and plant development. We previously reported that PME17, a group 2 PME expressed in root, could be processed by SBT3.5, a co-expressed subtilisin-like serine protease, to mediate changes in pectin properties and root growth. Here, we further report that a PMEI, PMEI4, is co-expressed with PME17 and is likely to regulate its activity. This sheds new light on the possible interplay of specific PMEs, PMEIs and SBTs in the fine-tuning of pectin structure

Elevated CO2 does not ameliorate effects of ozone on carbon allocation in Pinus halepensis and Betula pendula in symbiosis with Paxillus involutus

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Carbon fixation in Pinus halepensis submitted to ozone. Opposite response of ribulose-1,5-bisphosphate carboxylase/oxygenase and phosphoenolpyruvate carboxylase

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Substrate specificity of plant and fungi pectin methylesterases: Identification of novel inhibitors of PMEs

This work was supported by a grant from the Conseil Regional de Picardie, France and the European Regional Development Fund (PECTINHIB project) through a studentship awarded to ML' and from the Agence National de la Recherche (GALAPAGOS project, ANR-12-BSV5-0001International audiencePectin methylesterases (PMEs) play a central role in pectin remodeling during plant development. They are also present in phytopathogens such as bacteria and fungi. We investigated the substrate specificity and pH dependence of plant and fungi PMEs using tailor-made pectic substrates. For this purpose, we used two plant PMEs (from orange peel: Citrus sinensis and from Arabidopsis thaliana) and one fungal PME (from Botrytis cinerea). We showed that plant and fungi PMEs differed in their substrate specificity and pH dependence, and that there were some differences between plant PMEs. We further investigated the inhibition of these enzyme activities using characterized polyphenols such as catechins and tannic acid. We showed that PMEs differed in their sensitivity to chemical compounds. In particular, fungal PME was not sensitive to inhibition. Finally, we screened for novel chemical inhibitors of PMEs using a chemical library of similar to 3600 compounds. We identified a hundred new inhibitors of plant PMEs, but none had an effect on the fungal enzyme. This study sheds new light on the specificity of pectin methylesterases and provides new tools to modulate their activity. (C) 2015 Elsevier B.V. All rights reserved

Involvement of pectin methylesterase during imbibition and germination of Arabidopsis pollen grain

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Lactose derivatives as potential inhibitors of pectin methylesterases

International audienceThe discovery of molecules that can inhibit the action of phytopathogens is essential to find alternative to current pesticides. Pectin methylesterases (PME), enzymes that fine-tune the degree of methylesterification of plant cell wall pectins, play a key role in the pathogenicity of fungi or bacteria. Here we report the synthesis of new lactoside derivatives and their analysis as potential PME inhibitors using three plants and one fungal PME. Because of its structure, abundance and reduced cost, lactose was chosen as a case study. Lactoside derivatives were obtained by TEMPO-mediated oxidation of methyl lactoside, followed by an esterification procedure. Three derivatives were synthesized: sodium (methyl-lactosid)uronate, methyl (methyl-lactosid)uronate and butyl (methyl-lactosid)uronate. The inhibition of the plant and pathogen enzyme activities by lactoside derivatives was measured in vitro, showing the importance of the substitution on lactose: methyl (methyl-lactosid)uronate was more efficient than butyl (methyl-lactosid)uronate. These results were confirmed by docking analysis showing the difference in the interaction between lactoside derivatives and PME proteins. In conclusion, this study identified novel inhibitors of pectin remodeling enzymes

Cell wall compositional modifications of Miscanthus ecotypes in response to cold acclimation

International audienceMiscanthus, a potential energy crop grass, can be damaged by late frost when shoots emerge too early in the spring and during the first winter after planting. The effects of cold acclimation on cell wall composition were investigated in a frost-sensitive clone of Miscanthus x giganteus compared to frost-tolerant clone, Miscanthus sinensis August Feder, and an intermediate frost-tolerant clone, M. sinensis Goliath. Cellulose and lignin contents were higher in M. x giganteus than in the M. sinensis genotypes. In ambient temperature controls, each clone displayed different glucuronoarabinoxylan (GAX) contents and degree of arabinose substitution on the xylan backbone. During cold acclimation, an increase in (1 -> 3),(1 -> 4)-beta-D-glucan content was observed in all genotypes. Uronic acid level increased in the frost sensitive genotype but decreased in the frost tolerant genotypes in response to cold. In all clones, major changes in cell wall composition were observed with modifications in phenylalanine ammonia-lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD) activities in both non- and cold-acclimated experiments. A large increase in CAD activity under cold stress was displayed in each clone, but it was largest in the frost-tolerant clone, M. sinensis August Feder. The marked increase in PAL activity observed in the frost-tolerant clones under cold acclimation, suggests a reorientation of the products towards the phenylpropanoid pathway or aromatic synthesis. How changes in cell wall physical properties can impact frost tolerance is discussed. (C) 2012 Elsevier Ltd. All rights reserved