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This study describes an in vivo inhibition of dental plaque growth after peroxidase-generated hypoiodite (OI-) mouth-washes. After giving up ail other usual hygiene procedures nine healthy volunteers washed their mouth using 10 ml of the mouth-wash [H2O2 (0.005%), Kl (50 mM) and lactoperoxidase (0.04%)] three times a day for 1 minute for 3 days. The initial oxidation power of this mixture represented 430 ±11 µM oxidised cysteine (n=6), dropping down to 87 ± 6 µM after the solution was spat out (n=5). A saline solution served as a negative control, and a 0.2% chlorhexidine digluconate solution as a positive control. Proximal dental plaque between mandibular canine and lateral incisor (left and right) was collected after 3 days using standardized sterile toothpicks, then analysed for ATP and protein content. ATP concentrations dropped to 49% of the control values after OI- rinsing, and to 9% after chlorhexidine rinsing while the protein content dropped to 48% for OI- versus 31 % for chlorhexidine. However, when considering the ATP content per protein µg, only the decrease to 6% of the initial value in the chlorhexidine testing was significant while the drop to 81% for the OI- testings was not significant. This study points out a negative effect of OI- on plaque growth in vivo., Cette étude décrit l’inhibition de la croissance in vivo de la plaque dentaire après traitement à l’aide d’un bain de bouche contenant de la peroxydase et produisant de l’hypoiodite (OI-). Neuf personnes ont utilisé ce rinçage pendant une minute, 3 fois par jour pendant 3 jours, cependant qu’elles cessaient toute autre pratique d’hygiène bucco-dentaire; une solution saline servant de contrôle négatif et une solution de chlorhexidine de contrôle positif. Des échantillons de plaque interproximale furent prélevés de manière standardisée à l’aide de cure-dents stériles et leur contenu en ATP et en protéines furent mesurés. Les concentrations en ATP après traitement à l’OI- ne représentaient plus que 49% des valeurs des contrôles négatifs; le traitement à la chlorhexidine 31%. Le rapport ATP/masse protéique est fortement abaissé après traitement à la chlorhexidine (6%) mais se maintient à 85% de la valeur témoin après traitement à l’OI-.

We have investigated by the avidin-biotin peroxidase technique a wide variety of recognized cellular antigens in paraffin sections of both normal and pathological material which have been previously stained with hematoxylin and eosin. The intensity of peroxidase reaction was adequate to permit the diagnosis and the background of the immunoreaction minimal. This technique therefore, appears useful either for retrospective analysis of cellular antigens or when limited unstained material is available., Nous avons étudié, au moyen de l’immunoperoxydase, la présence de nombreux marqueurs cellulaires sur des coupes en paraffine de tissus normaux et pathologiques, colorés préalablement avec l’hématoxylineéosine.L’intensité de la réaction était tout à fait adéquate pour permettre le diagnostic avec un moindre background. Cette technique apparaît donc très utile pour des analyses rétrospectives de certains antigènes cellulaires, ou lorsque le matériel enrobé en paraffine est disponible en quantité limitée.

Trametes versicolor is a wood-inhabiting agaricomycete known for its ability to cause strong white-rot decay on hardwood and for its high tolerance of phenolic compounds. The goal of the present work was to gain insights into the molecular biology and biochemistry of the heme-including class II and dye-decolorizing peroxidases secreted by this fungus. Proteomic analysis of the secretome of T. versicolor BRFM 1218 grown on oak wood revealed a set of 200 secreted proteins, among which were the dye-decolorizing peroxidase Tv DyP1 and the versatile peroxidase Tv VP2. Both peroxidases were heterologously produced in Escherichia coli , biochemically characterized, and tested for the ability to oxidize complex substrates. Both peroxidases were found to be active against several substrates under acidic conditions, and Tv DyP1 was very stable over a relatively large pH range of 2.0 to 6.0, while Tv VP2 was more stable at pH 5.0 to 6.0 only. The thermostability of both enzymes was also tested, and Tv DyP1 was globally found to be more stable than Tv VP2. After 180 min of incubation at temperatures ranging from 30 to 50°C, the activity of Tv VP2 drastically decreased, with 10 to 30% of the initial activity retained. Under the same conditions, Tv DyP1 retained 20 to 80% of its enzyme activity. The two proteins were catalytically characterized, and Tv VP2 was shown to accept a wider range of reducing substrates than Tv DyP1. Furthermore, both enzymes were found to be active against two flavonoids, quercetin and catechin, found in oak wood, with Tv VP2 displaying more rapid oxidation of the two compounds. They were tested for the ability to decolorize five industrial dyes, and Tv VP2 presented a greater ability to oxidize and decolorize the dye substrates than Tv DyP1. IMPORTANCE Trametes versicolor is a wood-inhabiting agaricomycete known for its ability to cause strong white-rot decay on hardwood and for its high tolerance of phenolic compounds. Among white-rot fungi, the basidiomycete T. versicolor has been extensively studied for its ability to degrade wood, specifically lignin, thanks to an extracellular oxidative enzymatic system. The corresponding oxidative system was previously studied in several works for classical lignin and manganese peroxidases, and in this study, two new components of the oxidative system of T. versicolor , one dye-decolorizing peroxidase and one versatile peroxidase, were biochemically characterized in depth and compared to other fungal peroxidases.

The level of hydrogen peroxide (H 2 O 2 ) in plants signalizes the induction of several genes, including that of ascorbate peroxidase (APX-EC 1.11.1.11). APX isoenzymes play a central role in the elimination of intracellular H 2 O 2 and contribute to plant responses to diverse stresses. During the infection process in Theobroma cacao by Moniliophthora perniciosa oxidative stress is generated and the APX action recruited from the plant. The present work aimed to characterize the T. cacao APX involved in the molecular interaction of T. cacao – M. perniciosa . The peroxidase activity was analyzed in protein extracts from cocoa plants infected by M. perniciosa and showed the induction of peroxidases like APX in resistant cocoa plants. The cytosolic protein of T. cacao (GenBank: ABR68691.2 ) was phylogenetically analyzed in relation to other peroxidases from the cocoa genome and eight genes encoding APX proteins with conserved domains were also analyzed. The cDNA from cytosolic APX was cloned in pET28a and the recombinant protein expressed and purified (r Tc -cAPX). The secondary structure of the protein was analyzed by Circular Dichroism (CD) displaying high proportion of α-helices when folded. The enzymatic assay shows stable activity using ascorbate and guaiacol as an electron donor for H 2 O 2 reduction. The pH 7.5 is the optimum for enzyme activity. Chromatographic analysis suggests that r Tc -cAPX is a homodimer in solution. Results indicate that the r Tc -cAPX is correctly folded, stable and biochemically active. The purified r Tc -cAPX presented biotechnological potential and is adequate for future structural and functional studies.

Rphq2 , a minor gene for partial resistance to Puccinia hordei , was physically mapped in a 188 kbp introgression with suppressed recombination between haplotypes of rphq2 and Rphq2 barley cultivars. Partial and non-host resistances to rust fungi in barley (Hordeum vulgare) may be based on pathogen-associated molecular pattern (PAMP)-triggered immunity. Understanding partial resistance may help to understand non-host resistance, and vice versa. We constructed two non-gridded BAC libraries from cultivar Vada and line SusPtrit. Vada is immune to non-adapted Puccinia rust fungi, and partially resistant to P. hordei. SusPtrit is susceptible to several non-adapted rust fungi, and has been used for mapping QTLs for non-host and partial resistance. The BAC libraries help to identify genes determining the natural variation for partial and non-host resistances of barley to rust fungi. A major-effect QTL, Rphq2, for partial resistance to P. hordei was mapped in a complete Vada and an incomplete SusPtrit contig. The physical distance between the markers flanking Rphq2 was 195 Kbp in Vada and at least 226 Kbp in SusPtrit. This marker interval was predicted to contain 12 genes in either accession, of which only five genes were in common. The haplotypes represented by Vada and SusPtrit were found in 57 and 43 %, respectively, of a 194 barley accessions panel. The lack of homology between the two haplotypes probably explains the suppression of recombination in the Rphq2 area and limit further genetic resolution in fine mapping. The possible candidate genes for Rphq2 encode peroxidases, kinases and a member of seven-in-absentia protein family. This result suggests that Rphq2 does not belong to the NB-LRR gene family and does not resemble any of the partial resistance genes cloned previously.

Contact: nawel.achir@supagro.inra.fr. Fax: 133-467-617055; International audience; The kinetics of trans-beta-carotene and trans-lutein degradation were individually investigated in palm olein and Vegetaline (R), at four temperatures ranging from 120 to 180 degrees C. HPLC-DAD analysis was carried out to monitor trans and cis carotenoid variations over the heating time at each temperature. In both oils, initial trans-beta-carotene and trans-lutein degradation rates increased with temperature. Trans-lutein was found to degrade at a slower rate than trans-beta-carotene, suggesting a higher thermal resistance. The isomers identified were 13-cis- and 9-cis-beta-carotene, and 13-cis-, 9-cis-, 13'-cis-, and 9'-cis-lutein. In spite of the higher number of lutein cis isomers, their total amount was lower than that of beta-carotene cis isomers. Trans and cis carotenoids were involved in degradation reactions at rates that increased with temperature. All degradation rates were generally found to be lower in Vegetaline (R) than in palm olein. These results were explained by the initial composition of the two oils and especially their peroxide and vitamin E contents.

The effect of heterocyclic substance spirocarbon and pyrrolopyrimidinedione derivatives was studied on the hemoglobin ligand forms dynamics (RHb, HbO2, HbCO, SHb, MetHb), its basic stability, methemoglobin peroxidase activity and spectrophotometric characteristics of CNMetHb-Coomassi G-250 in the healthy donors’ blood. It was shown that spirocarbon causes a slight HbO2 decrease. In the experiments with pyrrolopyrimidindion derivatives the everage HbO2 values are in the range of control. There was carried out an analysis of HbO2, MetHb, CNMetHb electron spectra and the electron spectra of the complexes CNMetHb-Coomassi G-250. It was testified that spirocarbon causes a certain increase of basic stable hemoglobin and decrease of peroxydase activity. The pyrrolopyrimidinedione derivatives result in increasing of methemoglobin peroxydase activity in the tested samples.

At the industrial scale, the chemical Prileshajev reaction is currently the only method applied to produce epoxidized plant oils. Using enzymes could be an alternative way allowing an environmentally benign and more selective epoxidation reaction. P450 monooxygenases, diiron-center oxygenases, lipoxygenases, peroxygenases, and hydrolases performing perhydrolysis are enzyme classes involved in free fatty acid and glyceride epoxidation. After a brief description of these biocatalysts, this review focuses on the chemo-enzymatic epoxidation of unsaturated fatty acyd chains, where a lipase-catalyzed peroxy acid formation is followed by an uncatalyzed “self-epoxidation”. The molecular bases of lipase-catalyzed perhydrolysis as well as the different parameters influencing the epoxidation reaction are reviewed and described in details.

The antibacterial activity of the lactoperoxidase system (LPS) on the growth of Xanthomonas campestris, the causal agent of bacterial black spot in mangoes, Botryodiplodia theobromae, the causal agent of stem-end rot disease in mangoes, and Colletotrichum gloeosporioides, the causal agent of anthracnose disease in mangoes, was determined during culture at 30 degrees C and at several pH values (4.5, 5.5, and 6.5). When the results of using the LPS were compared with those from control cultures without the LPS reagents, the growth of the three microorganisms was totally inhibited in all of the conditions tested. Viability tests enumerating cultivable cells of X. campestris showed that the LPS had a bactericidal effect, whatever the pH value. This effect is faster at pH 5.5, corroborating the results reported in the literature (optimal pH for the LPS efficiency). Further, we proved that hydrogen peroxide alone had little inhibition effect on the growth of the microorganisms studied. This compound is essentially used to convert thiocyanate into hypothiocyanate during the lactoperoxidase reaction. The potential of the LPS for the postharvest treatment of the fruits for controlling microbial diseases was thus demonstrated. Nevertheless, further studies are needed on fresh fruits before envisaging any application.

The overall objective of this research was to find a new way to valorize rye bran, by producing a gellifier from the enzymatic solubilization of arabinoxylans (AX). The effects of three pure endo-xylanases from Aspergillus niger (Xyl-1), Talaromyces emersonii (Xyl-2), and Bacillus subtilis (Xyl-3) and of Grindamyl S100 (GS100), a commercial enzyme preparation containing a Xyl-1 type endo-xylanase, were tested on rye bran to study the solubilization of water-unextractable arabinoxylans (WUAX). Eight different extrusion-treated rye brans were also used as substrates to find the best physical treatment to facilitate enzymatic arabinoxylan (AX) solubilization. Arabinoxylans were better solubilized from the bran extruded at high temperature using Xyl-3. This enzyme was then tested in combination with pure (1,4)-beta-d-arabinoxylan arabinofuranohydrolase (AXH) and endo-beta-d-glucanase or ferulic acid esterase (FAE), from A. niger. Only beta-glucanase in combination with Xyl-3 improved the AX extraction, but it did not have a marked effect on the viscosity of the extracts. Xyl-3 was then tested on a high-shear-treated rye bran, and results were compared to those obtained with the high-temperature-extruded rye bran. The high-shear treatment did not improve the bran AX enzymatic solubilization. The combination of FAE with Xyl-1 or Xyl-3 did not improve the AX extraction from untreated and high-shear-treated rye bran. Finally, to study the gelation capacity of the enzymatically solubilized AX, the effect of the hydrogen peroxide/horseradish peroxidase (H(2)O(2)/POD) was tested on the Xyl-3 high-temperature-extruded bran extracts. Solubilized AX did not gel in the presence of the oxidizing system.

Colour and texture are important features of amala, a traditional thick paste obtained from dry yam flour. Tubers from eight yam cultivars were blanched at 65 °C for 20 min and dried at 40 °C for 5 days to test biochemical, thermal and pasting changes occurring during traditional yam flour processing. Blanching reduced peroxidase activity and drying reduced polyphenoloxidase activity, but total phenol content and the brown index of flour and of amala increased dramatically during the latter operations. The brown index of amala was significantly correlated with the total phenol content of the flour (r=0.84) and the peroxidase activity of the fresh tubers (r=0.75). Amylose content and starch gelatinization enthalpy remained stable. For all cultivars, drying significantly increased the onset gelatinization temperature, suggesting the occurrence of starch annealing. The latter leads to a reduction in swelling power and solubility during pasting, and hence to a lower paste viscosity.

An increase in peroxidase activity is a common response of plants to various stresses, especially to infection by pathogens. It seemed interesting to study the effects of symbiotic fungi of fodder grasses on the peroxidase activity of their hosts. The peroxidase activity of tall fescue cv. Clarine artificially infected with Neotyphodium coenophialum or with e-endophytes from other hosts (N. lolii and LpTG-2 from Lolium perenne, Epicbloë festucae from Festuca gigantea or Koeleria cristata, Epichloë bromicola from Bromus erectus) was generally either lower or not significantly different from that of the non-infected control. Similar results were obtained with perennial ryegrass cv. Vigor artificially infected with different e-endophytes. In contrast, artificial infection of both grasses with Gliocladium-like fungi belonging to the group of p-endophytes provoked an increase in peroxidase activity. These results suggest that p-endophytes can be considered as parasites while e-endophytes, which are not able to trigger a non-specific host defence response, are really mutualistic. (© 1999 Inra/Éditions scientifiques et médicales Elsevier SAS.), Les plantes stressées (ou attaquées par un pathogène) montrent généralement une augmentation de leur activité peroxydasique. Il a semblé intéressant d’observer l’effet de différents champignons endophytes des graminées sur l’activité peroxydasique de la fétuque élevée (var. Clarine) et du ray-grass anglais (var. Vigor). Clarine, artificiellement inoculée par Neotyphodium coenophialum ou par des e-endophytes isolés d’autres graminées (N. lolii et LpTG-2 de Lolium perenne, Epichloë festucae de Festuca gigantea et de Koeleria cristata, Epichloë bromicola de Bromus erectus) montre généralement une activité peroxydasique inférieure ou comparable à celle du témoin. Des résultats similaires ont été obtenus pour Vigor. En revanche, l’inoculation par un champignon Gliocladium-like, qui appartient au groupe des pendophytes, entraîne une augmentation significative de l’activité peroxydasique sur les deux espèces-hôtes. Ces résultats suggèrent le caractère quasi-parasitaire des p-endophytes, tandis que les e-endophytes se comporteraient plutôt comme des symbiotes dont la présence ne déclenche pas l’augmentation de l’activité peroxydasique. (© 1999 Inra/Éditions scientifiques et médicales Elsevier SAS.)

9 páginas, 8 figuras, 2 tablas -- PAGS nros. 303-311, The modification and generation of new biomolecules intended to give higher molecular-mass species for biotechnological purposes, can be achieved by enzymatic cross-linking. The versatile peroxidase (VP) from Pleurotus eryngii is a high redox-potential enzyme with oxidative activity on a wide variety of substrates. In this study, VP was successfully used to catalyze the polymerization of low molecular mass compounds, such as lignans and peptides, as well as larger macromolecules, such as protein and complex polysaccharides. Different analytical, spectroscopic, and rheological techniques were used to determine structural changes and/or variations of the physicochemical properties of the reaction products. The lignans secoisolariciresinol and hydroxymatairesinol were condensed by VP forming up to 8 unit polymers in the presence of organic co-solvents and Mn2+. Moreover, 11 unit of the peptides YIGSR and VYV were homogeneously cross-linked. The heterogeneous cross-linking of one unit of the peptide YIGSR and several lignan units was also achieved. VP could also induce gelation of feruloylated arabinoxylan and the polymerization of β-casein. These results demonstrate the efficacy of VP to catalyze homo- and hetero-condensation reactions, and reveal its potential exploitation for polymerizing different types of compounds, This work has been carried out with funding from the EU FP7 project “Peroxicats” (KBBE-2010-4-265397), the Spanish Ministry of Science and Innovation (BIO2009-08446, PRI-PIBAR-2011-1402), and the project “Lignin Fibre” financed by the Academy of Finland (Grant number 133091)

Les peroxyrédoxines (PRXs) forment une famille de peroxydases communes à tous les organismes vivants et ubiquitaires dans la cellule. Leur particularité provient d’un ou deux résidus cystéines accomplissant un cycle d’oxydo-réduction à l’aide d’un donneur d’électron. Ces protéines thiols sensibles au potentiel redox sont impliquées dans le mécanisme de détoxification du H2O2, une molécule oxydante induite lors de situations de stress. Les PRXs pourraient être induites par le stress et régulées par phosphorylation. En effet, des expérimentations in vitro ont démontré que la nucléoside diphosphate kinase 1 (NDPK1) a la capacité de phosphoryler une PRX cytosolique de pomme de terre. Ce mémoire décrit les travaux expérimentaux effectués pour caractériser la fonction de la PRX. Pour cela, le clonage d’une isoforme a été effectué, suivi d’une caractérisation biochimique et d’une étude d’expression de la protéine. Les données de séquençage révèlent qu’il s’agit d’une PRX de type II phylogénétiquement liée aux PRXs cytosoliques. L’ADNc codant pour cette peroxyrédoxine (PRX1) a été cloné chez Solanum chacoense. Une protéine recombinante portant une étiquette (6xHis) en N-terminale a été produite. Des essais enzymatiques ont confirmé la fonction antioxydante de la protéine recombinante et un anticorps polyclonal a été généré chez le lapin puis utilisé en conjonction avec un anticorps anti-NDPK1 pour déterminer les patrons d’expression généraux de ces protéines chez Solanum lycopersicum et Solanum tuberosum lors de situations de stress. Les données démontrent que les deux protéines sont généralement co-exprimées mais pas co-régulées et que la PRX1 est induite en certaines situations de stress., The peroxiredoxins (PRXs) are a recently discovered family of peroxidases found in all organisms and ubiquitous in the cell. An important particularity of these proteins is the presence of one or two active cysteines that accomplish an oxydo-reduction cycle with an electron donor. The PRXs are sensitive to the redox potential and are implicated in the detoxification of the H2O2, an oxidante molecule induced in stress situations. The PRXs should be induced in stress situations and regulated by phosphorylation. Indeed, in vitro experimentations have shown that the NDPK1 can phosphorylate a cytosolic PRX isoform of the potato. This dissertation describes the experimentation made to acquire a preliminary understanding of the function of the PRX. For this purpose, we cloned a PRX isoform, followed by a biochemical characterization and expression studies of the protein. The sequencing data shown a type II PRX phylogenetically related to the cytosolic isoforms. The cDNA of this peroxiredoxin (PRX1) has been cloned in Solanum chacoense. The recombinant protein produced had a N-terminal (6xHis) tag. Enzymatic assays confirmed the antioxidant activity of the recombinant protein and a polyclonal antibody has been generated from the rabbit. This antibody was used in conjunction with an antibody anti-NDPK1 to determine the general expression patterns of those proteins during stresses in Solanum lycopersicum and Solanum tuberosum. The results obtained showed that the two proteins are generally co-expressed but not co-regulated. Obvious experimental facts displayed an induction of the PRX1 in biotic and abiotic stresses situations.

Plant phenolics have drawn increasing attention due to their potential nutritional benefits. Although the basic reactions of the phenolics biosynthetic pathways in plants have been intensively analyzed, the regulation of their accumulation and flux through the pathway is not that well established. The aim of this study was to use a strawberry (Fragaria × ananassa) microarray to investigate gene expression patterns associated with the accumulation of phenylpropanoids, flavonoids, and anthocyanins in strawberry fruit. An examination of the transcriptome, coupled with metabolite profiling data from different commercial varieties, was undertaken to identify genes whose expression correlated with altered phenolics composition. Seventeen comparative microarray analyses revealed 15 genes that were differentially (more than 200-fold) expressed in phenolics-rich versus phenolics-poor varieties. The results were validated by heterologous expression of the peroxidase FaPRX27 gene, which showed the highest altered expression level (more than 900-fold). The encoded protein was functionally characterized and is assumed to be involved in lignin formation during strawberry fruit ripening. Quantitative trait locus analysis indicated that the genomic region of FaPRX27 is associated with the fruit color trait. Down-regulation of the CHALCONE SYNTHASE gene and concomitant induction of FaPRX27 expression diverted the flux from anthocyanins to lignin. The results highlight the competition of the different phenolics pathways for their common precursors. The list of the 15 candidates provides new genes that are likely to impact polyphenol accumulation in strawberry fruit and could be used to develop molecular markers to select phenolics-rich germplasm., This work was supported by PLANT-KBBE FraGenomics, by the Euroinvestigacion Subprogram from PLANT_KBBE Call, provided by the Spanish Science and Technology Ministry (grant no. EUI2008–03770 to A.M.), by the Centre CONSOLIDER on Agrigenomics and the Xarxa de Referencia en Biotecnología of the Generalitat de Catalunya, and by the Deutsche Forschungsgemeinschaft (grant no. SCHW634/14 to S.-Y.Y. and W.S.).

The influence of a water deficit was investigated on in vitro plantlets from the rubber tree (Hevea brasiliensis) clone PB 260. The Fraction of Transpirable Soil Water (FTSW) was used to identify three levels of water deficit. Transpiration and stomatal conductance decreased for a FTSW of 0.4 while fluorescence appeared more stable. Proline and ascorbate contents increased from the same level of water deficit. Antioxidant enzyme activities were more stable than glutathione reductase activity, which dramatically increased in line with the water deficit to peak at 0.12 UI/mg for a FTSW of 0.2. When plants were rehydrated, enzyme activities decreased. The accumulation of proline for the lowest FTSW suggested water stress. Antioxidant systems did not play a predominant role for this genotype.

Le traitement au froid en post-récolte (TPR) des ananas (Ananas comosus. (L). M) destiné à ralentir la sénescence des fruits, induit " le brunissement interne de l'ananas " (BI). Afin d'étudier des gènes susceptibles de discriminer les variétés résistantes, une comparaison entre des fruits frais ou soumis au TPR a été réalisée pour 4 variétés d'ananas différant par leur résistance au BI. D'après les résultats, en réponse au TPR l'absence de symptômes de BI est associée à une " résistance membranaire " et à une faible activité de la polyphenol oxydase. L'étude de l'activité de la phénylalanine ammonia-lyase et de l'ascorbate peroxidase a révélé que le froid induit une stimulation de l'activité de ces enzymes chez une variété sensible au BI. L'étude du catabolisme protéique a montré que la résistance des fruits au BI était liée : à la sous-expression du gène d'une protéase à cystéine, et à une sur-expression de gènes codant une cystatine et une protéase à acide aspartique, dont l'ADNc a été caractérisé et cloné pour la première fois chez l'ananas. L'expression différentielle de ces gènes indique qu'ils pourraient être utilisés pour le criblage par PCR de variétés dans les programmes d'améliorations de l'ananas pour la résistance au BI.

Pineapple internal browning (IB) is a chilling injury that produces enzymatic browning associated with flesh translucency. Pineapple biodiversity allowed the investigation of how polyphenol oxidase (PPO) and peroxidase (POD) activities with their different isoforms are involved in the IB mechanism. Fruits of four varieties that expressed IB symptoms differently, Smooth Cayenne (SCay) and the hybrids MD2, Flhoran 41 (Flh 41), and Flhoran 53 (Flh 53), were stressed by cold. The susceptible varieties showed classical brown spots but different patterns of IB, whereas MD2 and controls showed no IB. Enzymatic activities were measured on fruit protein extracts and PPO and POD isoforms separated on mini-gels (PhastSystem). Only PPO activity was significantly enhanced in the presence of IB. Up to six PPO isoforms were identified in the susceptible varieties. PPO was barely detectable in the nonsusceptible variety MD2 and in controls. The number of PPO isoforms and the total PPO activity after chilling are varietal characteristics.

Introduction. Mature green vanilla pods accumulate 4-O-(3-methoxy-benzaldehyde)-β- D-glucoside (glucovanillin), which, upon hydrolysis by an endogenous β-glucosidase, liberates vanillin, the major aroma component of vanilla. Little is known on the spatial distribution of aroma-generating phenolics, and the enzymes responsible for their liberation (β-glucosidase) and oxidation (peroxidase). We report here quantitative data with respect to these three components in relation to the anatomy of the pod. Furthermore, the spatial progression of oxidation is shown. Materials and methods. Mature green vanilla pods were analyzed for their contents of phenolics (HPLC), and β-glucosidase and per- oxidase activities by spectrophotometric techniques using p-nitrophenyl glucoside and vanillin as sub- strates, respectively. Lipids were examined under fluorescence microscopy after Nile red staining. Oxidation development was observed on transverse slices of pods. Results and discussion. Phenolics, and β-glucosidase and peroxidase activities showed gradients of increasing-decreasing concentrations from the stem to the blossom end of pods. The β-glucosidase activity is distributed in between the pla- centae, mesocarp, and trichomes in a ( 7/2/1 ) proportion while that of peroxidase shows a (38 / 1) ratio inthe mesocarp and placentae, and was absent from trichomes. Oxidation begins from the blossom end in the placentae, progressively invading the mesocarp and moving towards the stem end. Con- clusion. The green mature vanilla pod is spatially heterogeneous for its phenolics, and β-glucosidase and peroxidase activities, its placentae playing an important role in the liberation of vanillin and its sub- sequent oxidation. France / Vanilla planifolia / Orchidaceae / vanilla / β-glucosidase / peroxidase / glucovanillin / vanillin / lipids / oxidation / gradient / mesocarp / placentae / trichomes / xylem

Diplôme : Dr. d'Université; Le lin est une angiosperme annuelle dicotylédone connue pour ses fibres cellulosiques longues aux propriétés remarquables. Ces fibres se distinguent des cellules du bois par leur faible teneur en lignine et la distribution de ce polymère au sein des couches pariétales formant la fibre. Afin de mieux comprendre les facteurs contrôlant le taux de lignine dans les différents tissus de lin, nous avons entrepris une étude détaillée de la lignification au moyen d?approches microscopiques et biochimiques. Dans un premier temps, nos travaux ont souligné des similarités (lignine gaïacyle, liaisons condensées, détection du motif dibenzodioxocine et de la coniférine) entre la lignine de lin et celle des conifères. Une approche biochimique a montré que l?activité oxydasique majeure dépendrait des peroxydases. La partielle purification et des caractérisations initiales (électrophorèses natives, IEF, affinité de substrat) des peroxydases pariétales ont mis en évidence des différences importantes entre les isoformes du xylème, et celles des tissus externes (riches en fibres) de la tige. L?utilisation du chlorure de cérium a permis de préciser la distribution subcellulaire de l?H2O2 (catalyseur de polymérisation) dans la tige du lin au stade floraison. Dans les fibres longues, l?H2O2 n?a pu être détecté que dans la région médiane de la tige. En revanche l?H2O2 était présente dans toutes les cellules du xylème examinées. Des observations en ESEM et en microscopie confocale suggèrent que les fibres longues de lin forment un réseau dense qui limite la pénétration de protéines. L?ensemble de ces résultats souligne les différences entre le xylème et fibres longues pouvant expliquer en partie la faible lignification des fibres externes.. The angiosperm flax is an annual dicotyledon grown for its cellulose-rich bast fibres that show interesting properties. These fibres are characterized by a low lignin level in the different layers of the fibre cell wall that distinguishes them from xylem cells. In order to obtain a better understanding of the factors controlling lignin levels in different flax stem tissues we have undertaken a detailed study of lignification using microscopic and biochemical approaches. Initial results underlined similarities (guaiacyl lignin, condensed bonds, presence of dibenzodioxocine and coniferin) between flax lignin and that of conifers. A biochemical approach showed that the major oxidase activity was provided by peroxidases. Partial purification and initial characterization (native electrophoresis, IEF, substrate affinities) of cell wall peroxidases indicated important differences between the isoforms present in xylem and outer (fibre-rich) stem tissues. The use of cesium chloride allowed us to determine the cellular locations of H2O2 (polymerisation catalyst) in flax stems at the flowering stage. In bast fibres, H2O2 was only detected in the median region of the stem. In contrast H2O2 was observed in all xylem cells examined. Observation by ESEM and confocal microscopy suggested that the cell walls of flax bast fibres form a dense network that limits protein penetration. Altogether, these results highlight a number of differences between flax xylem and bast fibres that could partially explain the low lignification of the external bast fibres

Bayoud, caused by #Fusarium oxysporum# f. sp.# albedinis# (Foa), is the most damaging disease of date palm in Morocco. In the present study we have investigated the effect of jasmonic acid (JA) on two defencerelated enzymes, namely peroxidases (POX) and polyphenoloxidases (PPO) in date palm seedlings root. Our data show that exogenous application of JA at a concentration of 50 [mu]M increased the activity of both enzymes. The increase of POX activity in the presence of JAwas much more important than that observed following infection with the pathogen. As compared to untreated plants, PPO activity was 2.2 and 1.3 times higher in BSTN and JHL cultivars respectively. In addition, PAGE analysis revealed increased band intensity of the major constitutive isoforms of POX and PPO in both JA-treated and Foa-treated seedlings. Close examination of symptomatic and asymptomatic plants showed that root tissues of symptomatic plants were massively colonized by Foa. Also, disease development in these plants appeared to involve a marked degradation of the host cell walls early during the process of pathogen invasion. In contrast, the presence of Foa in asymptomatic plants induced limited necrotic lesions (hypersensitive-reaction like lesions) that were probably involved in reducing the progression of the pathogen. Together, our findings indicate that JA is capable of enhancing date palm root resistance to infection by Foa via the activation of defence-related enzymes such as PPO and POX.

The evolution of cyanide content and colour were monitored during the processing of lafu, traditional flour and improved flour from five cassava cultivars from Benin. In addition, the total phenol, polyphenoloxidase (PPO), peroxydase (POD) and linamarase activities were assessed. The processing of cassava in lafu and improved flour proved superior for producing safe and white non-fermented and fermented cassava flours with total cyanide mean values of 16.6 and 11.4 mg HCN/kg, db and DE values of 9.2 and 12.1, respectively. Detoxification appeared to be only linked to processing, in particular to the size reduction level of cassava roots, regardless of the initial cyanide level and the linamarase activity of the fresh roots. Cassava flour yellowness was closely linked to the phenol content (r = 0.95) that decreased after steeping and pressing. The PPO and POD activities did not appear to be linked to flour discoloration.

A postharvest treatment based on citric acid and chitosan was tested on two litchi cultivars of different provenance. Its effects on the activities of polyphenol oxidase (PPO), peroxidase (POD) and anthocyanase and on the anthocyanin content of the pericarp were measured as factors responsible for pericarp browning. The red colour of the pericarp was measured during storage of the fruit. The major anthocyanins present in both cultivars were cyanidin-3-rutinoside and cyanidin-3-glucoside. Although the concentration of cyanidin-3-rutinoside was 64% lower in the cultivar Kwai may (Guiwei) than in Wai chee (Huaizhi), this component represented more than 90% of total anthocyanins in both cultivars. The activity of PPO was six times greater in Kwai may than in Wai chee and the activity of POD was 30-times greater. The activity of POD was greater than that of PPO in both cultivars. The two cultivars, which differ in anthocyanin and oxidative enzyme compositions, responded differently to the acid and chitosan treatment, with the result that the red colour of Kwai may was better preserved during storage than that of Wai chee. This technique could be a future replacement for current sulphur treatments used to treat litchis transported by sea.

L'étude des activités enzymatiques exprimées lors de la croissance du champignon de pourriture blanche Trametes versicolor sur milieu malt agar en présence des éprouvettes du hêtre Fagus sylvatica été réalisée. Le processus de dégradation du bois se déroule en deux phases. La première phase est caractérisée par une production d'activités laccases et peroxydases couplées à la dégradation de la lignine. La seconde phase correspond à la production d'activités hydrolytiques impliquées dans la dégradation des polysaccharides. Au début du processus de colonisation du bois, on observe une production d'activités laccases responsables de la dégradation des extractibles du bois, en particulier la catéchine qui est un des composés facilement identifiables dans les extraits du hêtre. La présence d'un biocide comme le propiconazole provoque une forte induction d'activités chitinases lors du stade initial de la colonisation du bois. L'utilisation d'inhibiteurs de chitinases tels que la caféine permet de réduire la quantité du biocide nécessaire pour protéger le bois. La caféine et le rouge congo, un autre agent capable de perturber la mise en place des parois cellulaires du champignon ont un effet additif sur l'inhibition de la croissance de T. versicolor lorsqu'ils sont associés avec le biocide. L'application des méthodes mises en place dans le cadre de notre étude au cas de la dégradation du bois de hêtre traité thermiquement a permis de mettre en évidence l'effet de ce type de traitement sur l'expression des activités enzymatiques expliquant en partie les raisons de l'augmentation de la durabilité du bois suite au traitement thermique., The study of enzymatic activities expressed during growth of the white rot fungus T. versicolor on malt agar medium in the presence of beech (Fagus sylvatica) wood chips was investigated. The process of wood degradation was divided in two stages. The first stage was characterized by the production of laccases and peroxidases activities. The second stage was characterized by production of carbohydrates hydrolyzing activities. At the beginning of wood colonization process, the production of laccases activities was correlated with degradation of wood acetonic extractives as catechin, which was easily identified in the beech extracts. The presence of a biocide like propiconazole is responsible of the induction of a strong chitinases activity at the beginning of the colonization process. Utilisation of caffeine, a chitinases inhibitor, in the presence of propiconazole allowed to reduce the quantity of biocide necessary to prevent wood from fungal degradation. Similarly, congo red, another cell wall perturbing agent, presented additive effect on inhibition of the fungal growth when associated to propiconazole. The application of the methods developed in this study to the case of heat treated beech wood highlighted the effect of this treatment on the expression of enzymatic activities during wood degradation process explaining in great part the improvement of durability observed after heat treatment.

International audience; The role of the ‘peroxidase-oxidase’ reaction (catalytic formation of H2O2 by O2 activation), now well-known but seldom discussed, is recalled with respect to biochemical studies on lignin polymerisation and emphasis on the physico-chemical mechanisms of pattern formation and of molecular organisation during the synthesis of lignin model compounds (DHP). The corresponding processes of supramolecular assembly involving oligolignols interactions are related to more fundamental kinetic and thermodynamic mechanisms of cooperative inter- and intra-molecular binding reactions of polymer ligands, through interfacial- and template-constrained polymerisation. Finally, viewing synthetic and natural lignified structures as ‘open systems far from equilibrium’, typically self-organized by nucleation processes and by the formation of ‘dissipative structures’, as previously illustrated in this journal (Cellulose Chem. Technol., 2005, 39, pp. 341-367), the so-called ‘random’ process of lignification is tentatively described in terms of intra- and intermolecular cooperative non-covalent and covalent ‘binding’ and of hydrophobic ‘solvatation’. Here, the somehow controversial word ‘random’ refers to the pre-existence of elementary (i.e. atomic, molecular and polymer) structured building-blocks and to the absence of pre-formed systemic (i.e. supramolecular assemblies) organization.

Submitted by (lucia.rodrigues@ufrpe.br) on 2017-03-27T15:29:57Z No. of bitstreams: 1 Tereza Cristina de Assis.pdf: 813581 bytes, checksum: 8b96b058018eb3373d6a748191e4e45c (MD5) Made available in DSpace on 2017-03-27T15:29:57Z (GMT). No. of bitstreams: 1 Tereza Cristina de Assis.pdf: 813581 bytes, checksum: 8b96b058018eb3373d6a748191e4e45c (MD5) Previous issue date: 2006-02-23 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES The expressive increase in production of tropical flowers in Pernambuco indicates the State rising interest in ornamentals. This study had the objectives of: 1) screening plant parasitic nematodes in Zingiberales (Etlingera elatior, Zingiber spectabilis, Alpinia purpurata, Musa coccinea, Tapeinoquilos ananassae e Heliconia spp.) producing areas of Pernambuco, 2) predicting number of samples for nematodes monitoring at different acceptable error levels, 3) studying the effect of resistance abiotic inductors on nematode comunity associated with plant roots and soil, 4) evaluating enzymes activity in E. elatior, and 5) evaluating enzymes production in A. purpurata infected with Meloidogyne incognita. Samples (soil and roots of nematode parasited plants) were collected in producing areas from 2002 to 2004. Populational density of plant parasitic nematodes were evaluated and used to predict number of samples for monitoring. The study of induction resistance was carried out in one and two years old plants of a commercial area, fromSeptember to December in 2005. Acibenzolar-S-methyl (ASM), potassium silicate and neem cake were used as inductors, being analyzed free living and plant parasitic nematodes population density, area under nematode population density curve (AUNPDC), reproduction factor (RF), diameter of plant stem, β-1,3-glucanase and peroxidase activity. Enzymatic activity of esterase, phosphatase and peroxydase was evaluated in A. purpurata infected with M. incognita. Pratylenhus sp., Rotylenchulus sp., Meloidogyne spp., Helicotylenchus sp. and Criconemella sp. were frequents in most of samples. Symptoms of root-knot nematodes were verified in 100 % of the growing areas, being levels of Meloidogyne spp. considered high, up to 375 nematodes per 300 cm3 soil and 6090 nematodes per 20 g of roots, considering different areas and hosts. Among Meloidogyne species, M. incognita, M. arenaria and M. javanica were detected. Data analysis indicatedthat at least 11, 20, 10, 18 and 10 samples per area are recommended for monitoring the genus Pratylenchus, Rotylenchulus, Meloidogyne, Helicotylenchus and Criconemella, respectively, at 20 % error. The associations M. arenaria with E. elatior, Rotylenchulus sp. with A. purpurata, Heliconia spp. and M. coccinia, and Criconemella sp. with A. purpurata consisted of the first occurrence report in Pernambuco, Brazil. ASM was the best resistance inductor, reducing M. incognita population density, AUNPDC and FR with results similar to the nematicide control, but with no influence on free living nematodes in soil. Fitotoxic symptoms were not verified in any treatment. The action of ASM seems to be more related with peroxidases production than the β-1,3-glucanases activity in the plant. Among all of the inductors evaluated, ASM was the most effective inducing resistance against M. incognita in E. elatior. Enzymatic production was higher in A. purpurataparasited than in the controls. The acid phosphatase activity was high in contrast with the low esterase and peroxydase activity expressed in parasited plants. O aumento expressivo na área plantada com ornamentais tropicais em Pernambuco reflete o crescente interesse pela floricultura no Estado. Este estudo teve por objetivos: 1) realizar levantamento de fitonematóides em áreas produtoras de Zingiberales em Pernambuco, 2) estimar o número de amostras recomendado para monitoramento, 3) avaliar os efeitos de indutores abióticos de resistência sobre a nematofauna associada à rizosfera, 4) avaliar a atividade de enzimas em plantas de bastão do imperador (Etlingera elatior), 5) analisar a produção de enzimas em plantas de alpínia (Alpinia purpurata) sob parasitismo de Meloidogyne incognita. No período de 2002 a 2004, foram visitadas 10 áreas produtoras de Zingiberales ornamentais (Etlingera elatior, Zingiber spectabilis, Alpinia purpurata, Musa coccinea, Tapeinochilos ananassae e Heliconia spp.), no estado de Pernambuco. Em cada propriedade, foram coletadas raízes de plantas parasitadas por fitonematóides e solo da rizosfera. Após processamento das amostras, foram determinadas as densidades populacionais dos gênerosde nematóides presentes e estimado o número recomendado de amostras para monitoramento, considerando diferentes níveis de erro aceitável. O estudo com indutores foi desenvolvido em plantio comercial, com plantas cultivadas por um e dois anos, no período de setembro a dezembro de 2005. Acibenzolar-S-metil (ASM), silicato de potássio e torta de nim foram utilizados como indutores. Foram analisadas a densidade populacional de nematóides parasitos e de vida livre, curva de densidade populacional dos nematóides, área abaixo da curva da densidade populacional(AACDP), fator de reprodução (FR), diâmetro do pecíolo e atividade das enzimas β-1,3-glucanase e peroxidase. No estudo de enzimas em plantas de alpínia, sob parasitismo de M. incognita foram determinadas as atividades da esterase, fosfatase ácida e peroxidase. No levantamento, constatou-se ocorrência freqüente dos gêneros: Pratylenhus, Rotylenchulus,Meloidogyne, Helicotylenchus e Criconemella. Sintomas da meloidoginose foram constatados em 100 % das áreas de plantio, com os níveis populacionais médios de Meloidogyne spp. elevados, alcançando 375 espécimes/300 cm3 de solo e 6090 espécimes/20 g de raízes, considerando diferentes hospedeiros e áreas. Entre as espécies de Meloidogyne foram detectadas M. incognita, M. arenaria e M. javanica. As estimativas do número de amostras indicaram que pelo menos 11, 20, 10, 18 e 10 amostras por área são recomendadas para monitoramento dos gêneros Pratylenchus, Rotylenchulus, Meloidogyne, Helicotylenchus e Criconemella, respectivamente, considerando um nível de erro de 20 %. As associações M. arenaria com E. elatior, Rotylenchulus sp. com A. purpurata, Heliconia spp. e M. coccinia, e Criconemella sp. com A. purpurata constituíram os primeiros relatos da ocorrência em Pernambuco. ASM reduziu a densidade populacional, AACDP e FR de M. incognita, apresentando resultados semelhantes aos obtidos pelo nematicida, destacando-se dos demais tratamentos, sem no entanto influenciar negativamente as populações de outros nematóides presentes no solo. Não foram verificados sintomas de fitotoxidez em nenhum dos tratamentos realizados. A ação do ASM mostrou-se mais relacionada com a produção de peroxidases do que com a atividade de β-1,3-glucanases em plantas de bastão do imperador. A produção de enzimas foi maior em A. purpurata parasitada do que na testemunha. A maior atividade foi verificada pela enzima fosfatase ácida, enquanto esterase e peroxidase expressaram fraca atividade em plantas parasitadas.

Impacts of mild and severe water constraints were investigated on leaf protein content and activities of superoxide dismutase (SOD), catalase and peroxidase in young cuttings of two Populus deltoides × nigra clones, 'Luisa_Avanzo' and 'Dorskamp', known to differ in their level of drought tolerance. Expanding and mature leaves were analyzed separately. The effect of water deficit on enzymatic antioxidant system depended on both clone and leaf development stage. For 'Dorskamp', which presents an higher drought tolerance than 'Luisa_Avanzo', activities of SOD and catalase increased in response to the severe water deficit in mature leaves only. For 'Luisa_Avanzo', peroxidase activity increased in response to the mild water deficit in expanding leaves merely. For both clones, three different SOD isoforms, Mn-SOD, Fe-SOD and Cu/Zn-SOD were detected in various amounts depending on drought intensity., Impact de la sécheresse et du stade de développement des feuilles sur les systèmes antioxydants enzymatiques de deux clones de Populus deltoides × nigra. L'impact de sécheresses modérée et sévère sur le contenu en protéines des feuilles et sur les activités de la dismutase de superoxyde (SOD), de la catalase et de la peroxydase a été étudié chez de jeunes boutures de deux clones de Populus deltoides × nigra, 'Luisa_Avanzo' et 'Dorskamp', connus pour présenter des niveaux différents de tolérance au déficit hydrique. Les feuilles en croissance et matures ont été analysées séparément. La réponse à la sécheresse des systèmes de protection enzymatiques était différente selon le clone et le stade de développement des feuilles étudiées. Pour le clone 'Dorskamp', réputé plus tolérant que 'Luisa_Avanzo' à la sécheresse, les activités de la SOD et de la catalase augmentaient dans les feuilles matures en réponse à un déficit hydrique sévère. Pour le clone 'Luisa_Avanzo', l'activité de la peroxydase augmentait essentiellement dans les feuilles en croissance en réponse à une sécheresse modérée. Pour les deux clones, trois isoformes différentes de la SOD, la Mn-SOD, la Fe-SOD et la Cu/Zn-SOD ont été détectées en quantités variables chez les deux clones en fonction de l'intensité de la contrainte hydrique.

Les peroxydases de classe III sont des protéines présentes dans toutes les plantes terrestres. Lors de ce travail de thèse, une attention particulière a été portée sur deux peroxydases chez "Arabidopsis thaliana" : AtPrx33 et AtPrx34. Cette étude a permis de définir plusieurs fonctions pour les deux peroxydases : élongation des cellules de racines, différentiation des tissus et régulation des niveaux d'auxine "in planta". Dans une deuxième partie, des études phylogénétiques ont été conduites sur les peroxydases de classe III, mais aussi sur la superfamille entière des peroxydases dites "de plantes, bactéries et champignons". Suite à ces analyses, plusieurs modèles sont proposés afin d'expliquer, en particulier, l'apparition de la classe III chez les plantes terrestres, ainsi que de l'ancêtre de la superfamille chez les bactéries et une forme ancestrale de cellule eucaryote.

This study was undertaken to follow the kinetics of polyphenoloxidase (PPO), peroxidase (POD), and phenolic compounds during yam blanching at different temperatures and after drying and to identify by high-performance liquid chromatography (HPLC) the main phenolic compounds present in yam products. PPO activity was 50% higher in nonprocessed freeze-dried Florido (Dioscorea alata) than in nonprocessed freeze-dried Deba (Dioscorea rotundata). It decreased progressively during blanching. Forty-five percent of PPO activity remained after 50 min of blanching at 60 or 65 degrees C, whereas the POD activity dropped sharply to less than 20% of the initial activity after 10 min of blanching, whatever the blanching temperature. No anthocyanidins could be detected by HPLC at 520 nm in nonprocessed freeze-dried yam. Flavanols with a maximum absorption wavelength (lambda(max)) at 280 nm and cinnamic acid compounds with 320 nm lambda(max) were detected. Catechin was identified as the major flavanol with concentrations ranging from 0.26 to 0.41 microM g(-)(1) depending on cultivar. One cinnamic compound, ferulic acid, was identified and assessed in both cultivars (0.03-0.04 microM g(-)(1)). Total phenol, flavanol, and cinnamic contents decreased during blanching independently of temperature whereas some unresolved peaks were detected by HPLC in dried product. The latter was probably due to the consumption of coloring precursors and the appearance of polymerized or complex colored products.

The lactoperoxidase system (LPS) was evaluated for the prevention of postharvest diseases caused by Xanthomonas campestris, Botryodiplodia theobromae, and Colletotrichum gloeosporioides in 'Keitt' and 'Kent' mangoes. The LPS treatment significantly reduced the disease development on both cultivars after storage at 12 degrees C for 2 weeks, which was followed by a ripening at 25 degrees C. The LPS treatment did not alter the sensory quality of mango fruits (color, firmness, titrable acidity, and total soluble solids) when compared to untreated fruits. The LPS thus presents good potential alternative to the chemical fungicides traditionally used to improve the shelf life of mangoes.

11 pages, 4 figures, 4 tables.-- PMID: 15257762 [PubMed].-- PMCID: PMC509238., [Background] Polymorphisms were investigated within the ZmPox3 maize peroxidase gene, possibly involved in lignin biosynthesis because of its colocalization with a cluster of QTL related to lignin content and cell wall digestibility. The purpose of this study was to identify, on the basis of 37 maize lines chosen for their varying degrees of cell wall digestibility and representative of temperate regions germplasm, ZmPox3 haplotypes or individual polymorphisms possibly associated with digestibility., [Results] Numerous haplotypes with high diversity were identified. Frequency of nucleotide changes was high with on average one SNP every 57 bp. Nucleotide diversity was not equally distributed among site categories: the estimated π was on average eight times higher for silent sites than for non-synonymous sites. Numerous sites were in linkage disequilibrium that decayed with increasing physical distance. A zmPox3 mutant allele, carrying an insertion of a transposable element in the second exon, was found in lines derived from the early flint inbred line, F7. This element possesses many structural features of miniature inverted-repeat transposable elements (MITE). The mutant allele encodes a truncated protein lacking important functional sites. An ANOVA performed with a subset of 31 maize lines indicated that the transposable element was significantly associated with cell wall digestibility. This association was confirmed using an additional set of 25 flint lines related to F7. Moreover, RT-PCR experiments revealed a decreased amount of corresponding mRNA in plants with the MITE insertion., [Conclusion] These results showed that ZmPox3 could possibly be involved in monolignol polymerisation, and that a deficiency in ZmPox3 peroxidase activity seemingly has a negative effect on cell wall digestibility. Also, genetic diversity analyses of ZmPox3 indicated that this peroxidase could be a relevant target for grass digestibility improvement using specific allele introgressions., This work was supported by grants from the Genoplante maize program, coordinated by Alain Charcosset (INRA Le Moulon) and Alain Murigneux (Biogemma, Les Cézeaux).