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See detailInvolvement of polyamines in the adventitious rooting of micropropagated shoots of the apple rootstock MM106
Naija, Sélima; Elloumi, Nadhra; Ammar, Saida et al

in In Vitro Cellular & Developmental Biology-Plant (2009), 45

Apple rootstock MM106 shoots, raised in vitro, rooted at 96.7% after culture on a medium supplemented with an auxin for 5 d in darkness followed by culture on a second medium without growth regulators for ... [more ▼]

Apple rootstock MM106 shoots, raised in vitro, rooted at 96.7% after culture on a medium supplemented with an auxin for 5 d in darkness followed by culture on a second medium without growth regulators for 25 d in light. In control conditions (in absence of auxin in the first medium), these shoots did not root. Putrescine (PUT), spermidine (SPD), cyclohexylamine (CHA), and aminoguanidine (AG) enhanced rooting when applied during the first d of culture in the absence of IBA; on the contrary, α-difluoromethylornithine (DFMO) added to the first medium with IBA inhibited rooting. The endogenous levels of indole 3-acetic acid (IAA) and indole 3-acetylaspartic acid (IAAsp) increased up to a maximum concentration at days 2 and 3, respectively, in initial rooting conditions. PUT, when added with IBA, did not affect the typical IAA and IAAsp increase; when applied alone, it provoked an increase of their levels. Similar results were recorded with CHA. SPD, AG, and DFMO did not induce an increase of IAA and IAAsp in nonrooting conditions. The levels of endogenous PUT increased to a maximum at day 2 in rooting conditions; it was slightly affected by exogenous PUT and CHA application but reduced by SPD, AG, and DFMO. In rooting conditions, if the first medium was supplemented with SPD or AG, a small increase in peroxidase activity was observed, similar to that obtained with PUT treatment. The present work indicates an involvement of polyamines in the control of rooting and an interaction with auxins during the physiological phase of rooting. The consequence of this relationship was a different rooting expression, according especially to the content of these regulators in the culture medium. [less ▲]

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See detailComparative antioxidant capacities of phenolic compounds measured by various tests
Tabart, Jessica ULg; Kevers, Claire ULg; Pincemail, Joël ULg et al

in Food Chemistry (2009), 113

The purpose of this study was to compare the antioxidant capacities of standard compounds (phenolic compounds, ascorbic acid, and glutathione) as measured by various assays. Five methods were selected so ... [more ▼]

The purpose of this study was to compare the antioxidant capacities of standard compounds (phenolic compounds, ascorbic acid, and glutathione) as measured by various assays. Five methods were selected so as to span a diversity of technical approaches: TEAC (radical 2,2′-azino-bis(3-ethylbenzothiazoline)-6 sulphonic acid), DPPH (radical 2,2-diphenyl-1-picryhydrazyl used to measure reducing capacity), ORAC (oxygen radical scavenging capacity), red blood cell haemolysis (protection of biological sample), and ESR (electron spin resonance for direct free radical evaluation). Most compounds showed significant differences in free radical scavenging activity according to the method used. Of the 25 tested compounds, only a few, such as myricetin and gallocatechin, gave comparable activities in the various tests. To standardise reporting on antioxidant capacity, it is proposed to use a weighted mean of the values obtained using the DPPH, ORAC, resistance to haemolysis, and ESR assays. This strategy was used to test the antioxidant capacity of several beverages. The highest antioxidant capacity was observed for red wine, followed by green tea, orange juice, grape juice, vegetable juice, and apple juice. [less ▲]

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See detailProteomic and enzymatic response of poplar to cadmium stress
Kieffer, Pol; Schröder, Peter; Dommes, Jacques ULg et al

in Journal of Proteomics (2009), 72

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See detailCharacterization and Cloning of Chitin Deacetylases from Rhizopus Circinans
Gauthier, Carole ULg; Clerisse, Fabienne ULg; Dommes, Jacques ULg et al

in Protein Expression & Purification (2008), 59

Chitin deacetylase catalyzes hydrolysis of the acetamido groups of N-acetylglucosamine of chitin in fungal cell walls. Here a chitin deacetylase secreted by Rhizopus circinans was purified to homogeneity ... [more ▼]

Chitin deacetylase catalyzes hydrolysis of the acetamido groups of N-acetylglucosamine of chitin in fungal cell walls. Here a chitin deacetylase secreted by Rhizopus circinans was purified to homogeneity and partially characterized. The enzyme exhibits an apparent molecular weight of approximately 75kDa. At 37 degrees C it shows optimal activity at pH 5.5-6. Its pH stability and thermal stability are good. Mn(2+) and Mg(2+) slightly enhance the activity of the enzyme and Cu(2+) strongly inhibits it. An R. circinans cDNA library was constructed and screened with a homologous probe synthesized by RT-PCR or with synthetic primers derived from the N-terminal amino-acid sequence of the native purified chitin deacetylase. Three chitin deacetylase cDNAs (RC, D2, and I3/2) were isolated from the cDNA library and sequenced. These cDNAs exhibit features characteristic of chitin deacetylase sequences: the presence of a polysaccharide deacetylase domain, a metal-binding triad, the conserved catalytic residues, and high homology with various chitin deacetylase genes. The cDNAs were cloned in a Pichia pastoris expression system and produced as polyhistidine-tagged proteins. Only one recombinant enzyme (called RC) was active under the tested conditions. It was purified to homogeneity in a single step and further characterized. The protein showed an apparent molecular mass of approximately 75kDa and, like the native enzyme, showed optimal activity at pH 5.5-6 at 37 degrees C. It was strongly inhibited by Cu(2+). The isolation of several chitin deacetylase cDNAs from the same microorganism is discussed. [less ▲]

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See detailSystemic resistance induction in tomato by Pseudomonas putida BTP1: investigation of defense pathways.
Mariutto, M.; Duby, Franceline ULg; Ongena, Marc ULg et al

in Journal of Plant Pathology [=JPP] (2008), 90

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See detailSystemic resistance and lipoxygenase-related defence response induced in tomato by Pseudomonas putida strain BTP1.
Akram, Adam; Ongena, MARC ULg; Duby, Franceline et al

in BMC Plant Biology (2008), 8

BACKGROUND: Previous studies showed the ability of Pseudomonas putida strain BTP1 to promote induced systemic resistance (ISR) in different host plants. Since ISR is long-lasting and not conducive for ... [more ▼]

BACKGROUND: Previous studies showed the ability of Pseudomonas putida strain BTP1 to promote induced systemic resistance (ISR) in different host plants. Since ISR is long-lasting and not conducive for development of resistance of the targeted pathogen, this phenomenon can take part of disease control strategies. However, in spite of the numerous examples of ISR induced by PGPR in plants, only a few biochemical studies have associated the protective effect with specific host metabolic changes. RESULTS: In this study, we showed the protective effect of this bacterium in tomato against Botrytis cinerea. Following treatment by P. putida BTP1, analyses of acid-hydrolyzed leaf extracts showed an accumulation of antifungal material after pathogen infection. The fungitoxic compounds thus mainly accumulate as conjugates from which active aglycones may be liberated through the activity of hydrolytic enzymes. These results suggest that strain BTP1 can elicit systemic phytoalexin accumulation in tomato as one defence mechanism. On another hand, we have shown that key enzymes of the lipoxygenase pathway are stimulated in plants treated with the bacteria as compared with control plants. Interestingly, this stimulation is observed only after pathogen challenge in agreement with the priming concept almost invariably associated with the ISR phenomenon. CONCLUSION: Through the demonstration of phytoalexin accumulation and LOX pathway stimulation in tomato, this work provides new insights into the diversity of defence mechanisms that are inducible by non-pathogenic bacteria in the context of ISR. [less ▲]

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See detailQuantitative changes in protein expression of cadmium-exposed poplar plants
Kieffer, Pol; Dommes, Jacques ULg; Hoffmann, Lucien et al

in Proteomics (2008), 8

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See detailAxillary proliferation and tuberisation of Dioscorea cayenensis-D-rotundata complex
Ovono, Paul O; Kevers, Claire ULg; Dommes, Jacques ULg

in Plant Cell, Tissue & Organ Culture (2007), 91(2), 107-114

Yams (Dioscorea spp) are tuber crops used as staple food in Africa because of their nutritional value. However agronomic constraints, phytosanitary problems and the lack of good healthy planting material ... [more ▼]

Yams (Dioscorea spp) are tuber crops used as staple food in Africa because of their nutritional value. However agronomic constraints, phytosanitary problems and the lack of good healthy planting material restrict their production. In contrast to the inefficiency of traditional method of planting, tissue culture techniques allow to increase the multiplication and the rapid production of pathogen- free plant material. This work was undertaken to provide farmers in African countries with healthy microplants and microtubers as seeds. In vitro nodal segments of two varieties of local yams D. cayenensis-D. rotundata complex (cv.'Singo', cv. 'Singou' and cv. 'Gnidou') were micropropagated on the modified medium of Murashige and Skoog. The morphogenesis, the growth of microplants and microtuber formation have been found to be controlled by external factors that act individually and synergistically. Addition of kinetin (2 mg l(-1)) to the culture media could reduce multiplication rate (node number) of some clones. An increase of the sucrose concentration from 3% to 5% induced no change in the multiplication and tuberisation parameters. An important reduction of the multiplication (shoot number, height and node number) and the tuberisation (tuber number and length) was observed with 8% sucrose. Multiplication (shoot and node number) was increased in the presence of jasmonic acid (10 mu M). JA also induced an increase of tuber number in the absence of Kin. Multiplication of yam by in vitro growth of nodal segments is a way for rapid clonal multiplication and could allow solving the problem of lack of seed material faced by farmers. This method could also be used for multiplication of elite cultivars, independently of the growing season. [less ▲]

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See detailEvolution of antioxidant capacity during storage of selected fruits and vegetables
Kevers, Claire ULg; Falkowski, Michael; Tabart, Jessica et al

in Journal of Agricultural and Food Chemistry (2007), 55(21), 8596-8603

Interest in the consumption of fresh fruits and vegetables is, to a large extent, due to its content of bioactive nutrients and their importance as dietary antioxidants. Among all of the selected fruits ... [more ▼]

Interest in the consumption of fresh fruits and vegetables is, to a large extent, due to its content of bioactive nutrients and their importance as dietary antioxidants. Among all of the selected fruits and vegetables, strawberries and black grapes have relatively high antioxidant capacities associated with high contents of total phenolic compounds, ascorbic acid, and flavonols. More interesting, the results of this study indicated that in most fruits and vegetables storage did not affect negatively the antioxidant capacity. Better, in some cases, an increase of the antioxidant capacity was observed in the days following their purchase, accompanied by an increase in phenolic compounds. In general, fruits and vegetables visually spoil before any significant antioxidant capacity loss occurs except in banana and broccoli. When ascorbic acid or flavonoids (aglycons of flavonols and anthocyanins) were concerned, the conclusions were similar. Their content was generally stable during storage. [less ▲]

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See detailBeneficial use of lignosulfonates in in vitro plant cultures: stimulation of growth, of multiplication and of rooting
Docquier, Sarah; Kevers, Claire ULg; Lambe, Pascal et al

in Plant Cell, Tissue & Organ Culture (2007), 90(3), 285-291

Lignosulfonates (LIGNs), low-cost by-products from the paper industry, are already commercialized as fertilizers; they stimulate both vegetative and reproductive growths and fructification. LIGNs have ... [more ▼]

Lignosulfonates (LIGNs), low-cost by-products from the paper industry, are already commercialized as fertilizers; they stimulate both vegetative and reproductive growths and fructification. LIGNs have been tested in in vitro cultures and here too, they improve shoot growth and vigor, and rooting of various plant materials. This study aimed at to extend the in vitro application of LIGNs at different developmental stages in order to increase the productivity of systems generating vitroplants. The present results showed the beneficial effects of various LIGN applications on growth of a tropical orchid, Phalaenopsis, multiplication of Saint-paulia ionantha and rooting of poplar and Sequoiadendron sempervirens shoot cuttings. One of the most interesting observations was the stimulating effect of Ca-chelated LIGN on growth of Phalaenopsis and on rooting of Sequoiadendron. The significant and reproducible effects of LIGNs at several steps of micropropagation of different plant materials represent a potential tool improve quality without embarrassing side-effects. [less ▲]

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See detailConditioning Panax vietnamensis cell mass production in bioreactors
Jacques, Philippe; Kevers, Claire ULg; Gaspar, Thomas et al

in Acta Botanica Gallica : Bulletin de la Société Botanique de France (2007), 154

The influence of lighting conditions, culture volume and four different auxins (indoleacetic acid (IAA), indolebutyric acid (IBA), 2,4-dichlorophenoxyacetic acid (2,4-D) or 3-(benzo[b]selenyl)acetic acid ... [more ▼]

The influence of lighting conditions, culture volume and four different auxins (indoleacetic acid (IAA), indolebutyric acid (IBA), 2,4-dichlorophenoxyacetic acid (2,4-D) or 3-(benzo[b]selenyl)acetic acid (BSAA)) on Panax vietnamensis cell growth was evaluated in flasks. The highest biomass productivity was observed under continuous light and in the presence of IBA (0.36 g DW l(-1) d(-1)) or BSAA (0.5 g DW l(-1) d(-1)). Cultures in bioreactors were performed with these two auxins. The final biomass concentration was 107 g FW l(-1) and 373 g FW l(-1) in the presence of IBA or BSAA, respectively. [less ▲]

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See detailThe systemic resistance induced in tomato by a non-pathogenic Pseudomonas strain is associated with the stimulation of the lipoxygenase pathway
Adam, Akram; Duby, Franceline ULg; Ongena, MARC ULg et al

in Bulletin OILB/SROP = IOBC/WPRS Bulletin (2007), 30

Root treatment by the non-pathogenic Pseudomonas putida strain BTP1 reduced by 34% the disease caused by Botrytis cinerea on tomato leaves. This induced systemic resistance phenomenon is associated both ... [more ▼]

Root treatment by the non-pathogenic Pseudomonas putida strain BTP1 reduced by 34% the disease caused by Botrytis cinerea on tomato leaves. This induced systemic resistance phenomenon is associated both with the accumulation of fungitoxic material and with the stimulation of the lipoxygenase pathway in infected leaves. More precisely, we observed a consistent change in the expression of a new tomloxF gene in the leaves from BTP1-treated plants as far as the pathogen is introduced. This suggests that the roots were primed and reacted locally to colonization by bacteria and that defense-related gene expression is turned on systemically upon pathogen perception [less ▲]

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See detailOptimisation of extraction of phenolics and antioxidants from black currant leaves and buds and of stability during storage
Tabart, Jessica ULg; Kevers, Claire ULg; Sipel, Arnaud ULg et al

in Food Chemistry (2007), 105(3), 1268-1275

Health benefits of a diet rich in fruits and vegetables are attributed in part to their contents of phenolics and other antioxidant compounds. In this research, the extraction of phenolics and antioxidant ... [more ▼]

Health benefits of a diet rich in fruits and vegetables are attributed in part to their contents of phenolics and other antioxidant compounds. In this research, the extraction of phenolics and antioxidant compounds from black currant was optimised for different plant organs. The extraction solvent affected yield: aqueous acetone was better than methanol and acetate or glycine buffer. In aqueous buffer, maximum yields of total phenolics and antioxidant activities were obtained at pH 3. Extraction from lyophilised materials yielded extracts with higher phenolic contents and antioxidant activities. Stability of extracts made with acetate or glycine buffer was limited while the use of a mixture of acetone/acetic acid/water for extraction allowed a high phenolic content and antioxidant capacity in dry extract to be maintained for several months. This type of extract could be incorporated in functional food, beverage or dietary supplement. (c) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailAntioxidant capacity of black currant varies with organ, season, and cultivar
Tabart, Jessica; Kevers, Claire ULg; Pincemail, Joël ULg et al

in Journal of Agricultural and Food Chemistry (2006), 54(17), 6271-6276

Small berries such as black currant constitute one of the important sources of potential health-promoting phytochemicals because these fruits are rich sources of compounds with high antioxidant properties ... [more ▼]

Small berries such as black currant constitute one of the important sources of potential health-promoting phytochemicals because these fruits are rich sources of compounds with high antioxidant properties. In this work, antioxidant capacities of different parts (buds, leaves, fruits) of various black currant cultivars were compared throughout the growing season with the aim to prepare extracts with high antioxidant capacity. Buds (opened, at the end of March) and leaves (in June) had a higher content in phenolics and antioxidants than fully ripened berries (in July) and the best yield (per branch) was obtained with the leaves collected in June due to their higher biomass. The differences observed among the eight cultivars tested were small. Concerning flavonols, quercetin was dominant in all organs and cultivars, myricetin varied widely among the cultivars, and kampferol was very low. [less ▲]

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See detailA late blight resistant potato plant overexpresses a gene coding for alpha-galactosidase upon infection by Phytophthora infestans
Evers, Danièle; Ghislain, Marc; Hoffmann, Lucien et al

in Biologia Plantarum (2006), 50(2), 265-271

Late blight of potato, caused by Phytophthora infestans was studied by using a resistant clone of potato on one side and a susceptible clone on the other side. A gene coding putatively for an alpha ... [more ▼]

Late blight of potato, caused by Phytophthora infestans was studied by using a resistant clone of potato on one side and a susceptible clone on the other side. A gene coding putatively for an alpha-galactosidase has been isolated by mRNA reverse transcription polymerase chain reaction differential display and was shown to be differentially expressed between the resistant and the susceptible clone. alpha-Galactosidases catalyse the hydrolysis of alpha-1,6 linked alpha-galactose residues from oligosaccharides and it could be shown in the present work that raffinose content decreases at 30 h after infection by P. infestans in the resistant clone. [less ▲]

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See detailTwo PR-1 loci detected in the native cultivated potato Solanum phureja appear differentially expressed upon challenge by late blight
Evers, Danièle; Schweitzer, C.; Nicot, N. et al

in Physiological and Molecular Plant Pathology (2006), 67(3-5, SEP-OCT), 155-163

Plant pathogenesis-related proteins are toxic to invading pathogens. Among them, the Subfamily PR-1 represents low-molecular weight proteins of unknown biochemical function. Here, we describe the cloning ... [more ▼]

Plant pathogenesis-related proteins are toxic to invading pathogens. Among them, the Subfamily PR-1 represents low-molecular weight proteins of unknown biochemical function. Here, we describe the cloning and isolation of two PR-1 genes (PR-1b1 (GenBank accession no. SPH493450) and PR-1b2 (SPH493451)) that encode predicted basic proteins. We isolated them from Solanum phureja, a native Andean potato with horizontal resistance to late blight, caused by the oomycete Phytoplithora infestans. We demonstrate that the PR-1 genes belong to a small multigene family with an estimated copy number of 4-6 with one of them located oil chromosome IX as determined by genetic mapping. The expression of PR-1 genes was different in late blight resistant and Susceptible genotypes. Therefore, we propose that both PR-1 genes may play a role in horizontal late blight resistance of S. phureja. (c) 2006 Elsevier Ltd. All rights reserved. [less ▲]

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