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See detailA specific role for spermidine in the initiation phase of somatic embryogenesis in Panax ginseng CA Meyer
Monteiro, Marta; Kevers, Claire ULg; Dommes, Jacques ULg et al

in Plant Cell, Tissue & Organ Culture (2002), 68(3), 225-232

Somatic embryogenesis of Panax ginseng CA Meyer was initiated from suspension aggregates of an embryogenic callus, in a liquid medium consisting of half strength Murashige and Skoog (1962) supplemented ... [more ▼]

Somatic embryogenesis of Panax ginseng CA Meyer was initiated from suspension aggregates of an embryogenic callus, in a liquid medium consisting of half strength Murashige and Skoog (1962) supplemented with the synthetic auxin benzoselenienyl-3 acetic acid. The addition of spermidine to this initiation medium significantly increased the production of somatic embryos. In this case, the total polyamine content of the embryogenic mass was higher than that of cultures without spermidine. At day 6 of the culture, a transient accumulation of free polyamines, mainly spermidine, was observed. After this peak, free and conjugated polyamines levels did not show significant variation nor did the polyamine oxidase activity. The results clearly demonstrated that spermidine supplied to the medium was oxidised by polyamine oxidase and partially metabolised into putrescine. The role of spermidine and its interaction with auxin in the initiation of the embryogenic process in Panax ginseng are discussed in relation to embryogenic potential. [less ▲]

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See detailStudy of bacterial determinants involved in the induction of systemic resistance in bean by Pseudomonas putida BTP1
Ongena, MARC ULg; Giger, A.; Jacques, P. et al

in European Journal of Plant Pathology (2002), 108(3), 187-196

The ability of Pseudomonas putida BTP1 to induce resistance in bean to Botrytis cinerea was demonstrated in soil experiments on plants pre-inoculated at the root level with the bacteria before challenge ... [more ▼]

The ability of Pseudomonas putida BTP1 to induce resistance in bean to Botrytis cinerea was demonstrated in soil experiments on plants pre-inoculated at the root level with the bacteria before challenge with the leaf pathogen. As a first step to characterize the molecules from BTP1 responsible for induction of systemic resistance in bean, heat-killed cells and supernatant from culture in an iron-limited medium were tested for their protective effect. Most of the resistance-eliciting activity of the strain was retained in the crude cell-free culture fluid. In vivo assays with samples from successive fractionation steps of the BTP1 supernatant led, (i) to the conclusion that salicylic acid, pyochelin and pyoverdin, previously identified as Pseudomonas determinants for induced systemic resistance (ISR), were not involved in systemic resistance triggered by BTP1, and (ii) to the isolation of fractions containing one main metabolite that retained most of the resistance-inducing activity in bean. Although this molecule remains to be structurally characterized, its isolation is an addition to the range of determinants from plant growth-promoting rhizobacteria (PGPR) known to stimulate plant defences. [less ▲]

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See detailBiosynthesis of peroxidases: a role as interplay between primary and hormonal metabolisms
Gaspar, Thomas ULg; Le Dily, Frédérique; Billard, Jean-Pierre et al

in Acosta, M.; Rodriguez-lopez, J.-N.; Pedreno, Maria-A (Eds.) Plant perodixases - Biochemistry and physiology - VI international plant peroxidase symposium Proceedings (2002)

Hyperhydric, fully habituated (growth independent from exogenous auxin and cytokinin), fully heterotrophic (achlorophyllous, dependent on sucrose supply, nevertheless able to fix CO2 non ... [more ▼]

Hyperhydric, fully habituated (growth independent from exogenous auxin and cytokinin), fully heterotrophic (achlorophyllous, dependent on sucrose supply, nevertheless able to fix CO2 non-photosynthetically) and non-organogenic (complete loss of any organogenic totipotency) sugarbeet cells in culture were characterized by a very low peroxidase activity, among other deficient heme compounds. This deficiency resulted from the lack of synthesis of the precursor aminolevulinic acid (ALA) through the chloroplastic Beale pathway; the low productive unusual ALA synthesis through the mitochondrial Shemin pathway (commonly used by animals and fungi) functioned but further at a limited rate due to inhibition of ALA-dehydratase by benzoic derivatives, predominant among the phenolic acids of these cells (compared to normal ones). A thorough investigation of the metabolic and hormonal functioning of these neoplastic cells showed that the above deviation originated from a disturbed nitrogen metabolism that diverted glutamate from the Kreb's cycle into polyamine (over) synthesis, which had also as consequence a low ethylene production. The Kreb's cycle could be replenished by oxaloacetate and malate deriving from the anaplerotic fixation of CO2 onto phosphoenolpyruvate. A privileged pentose phosphate pathway (PPP) allowed the formation of substrates for a non-limited biosynthesis of (endogenous) auxins and cytokinins. The PPP, through NAD(P)H formation, enhanced nitrogen metabolism, but also, together with a putative H2O2 accumulation (originated from high superoxide dismutase activity and high polyamine oxidation combined with low catalase activity), favoured the alternative respiratory pathway. These results not only illustrate a novel view of integration of hormonal metabolisms with the C and N primary and secondary ones but also allow to consider the biosynthesis of peroxidases in an interplay or mediating role between them. [less ▲]

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See detailCuttings of the non-rooting rac tobacco mutant overaccumulate phenolic compounds
Faivre-Rampant, Odile; Charpentier, Jean Paul; Kevers, Claire ULg et al

in Functional Plant Biology (2002), 29(1), 63-71

The auxin and phenolic contents, as well as phenylalanine ammonia-lyase (PAL) activity, were determined in in vitro cultured shoots of the recalcitrant-to-root rac mutant of tobacco, and compared with ... [more ▼]

The auxin and phenolic contents, as well as phenylalanine ammonia-lyase (PAL) activity, were determined in in vitro cultured shoots of the recalcitrant-to-root rac mutant of tobacco, and compared with wild-type shoots. The mutant and wild-type shoots showed similar auxin changes during the culture cycle, but with higher contents for the mutant. A transient peak of auxin (corresponding to the achievement of the rooting inductive phase) occurred at day 14 in both types of shoots, but earlier in the basal parts of the wild-type stems. The rac shoots contained more phenolics, corresponding with an increased PAL activity. The most abundant phenolic compound found in the two types of tobacco was chlorogenic acid, which was more abundant in the rac shoots. Rutin was also detected at a higher concentration in the mutant shoots. Basal parts of wild-type shoots treated with 10(-3) chlorogenic acid reacted by accumulating auxins and, unlike untreated controls, did not form adventitious roots. The relationships between those biochemical analyses in relation to the growth limitation of the rac mutant, and the inhibition of its root development, are discussed. [less ▲]

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See detailAuxins in the biology of roots
Gaspar, Thomas ULg; Faivre-Rampant, Odile; Kevers, Claire ULg et al

in Waisel, Yoav; Eshel, Amram; Kafkafi, Uzi (Eds.) Auxins in the biology of roots (2002)

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See detailIsolation of new metabolites from Pseudomonas putida involved in plant resistance induction
Ongena, Marc ULg; Budzikiewicz, H.; Jacques, Ph. et al

Poster (2001, September)

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See detailModified hormonal balance in rooting-recalcitrant rac mutant tobacco shoots
Faivre-Rampant, Odile; Kevers, Claire ULg; Dommes, Jacques ULg et al

in Plant Biosystems (2001), 135(1), 85-93

The rooting-recalcitrant rac tobacco mutant has been multiplied in vitro via outgrowth of axillary buds in parallel to the DS wild-type. The mutant shoots grew at a lower rate and did not root whatever ... [more ▼]

The rooting-recalcitrant rac tobacco mutant has been multiplied in vitro via outgrowth of axillary buds in parallel to the DS wild-type. The mutant shoots grew at a lower rate and did not root whatever the treatments, whereas the wild-type shoots rooted spontaneously during the culture cycle without auxin treatment. The mutant and wild-type shoots showed similar peroxidase variations along the culture cycle (21 days) but with higher levels of activity for the rac mutant: minimum peroxidase activity occurrey at day 14 in whole shoots of both tobacco genotypes, but already at day 7 in the basal parts of the stems (where roots appear) of the wild-type tobacco, while it was delayed in the mutant. Free and conjugated auxin and polyamine levels were also determined in whole shoots and basal parts of the stems. The rac mutant was characterised by higher auxin and polyamine contents. A peak of auxins and polyamines appeared at day 14 in the whole shoots whatever the tobacco genotype. This peak was delayed in the basal parts of the rac stems compared to the wild-type ones. The mutant shoots contained higher levels of benzyladenine and isopentenyladenosine at the end of the culture cycle, whereas zeatin riboside was more abundant in wild-type shoots. In response to increasing concentrations of indole-3-butyric acid (IBA) and 1-naphthaleneacetic acid (NAA), only the wild-type shoots responded by an increase in growth rate followed by inhibition at high concentrations. The rac shoot responses were very low or nonexistent. Peroxidase activity was also measured in E basal parts of tobacco stems grown in the presence of IBA. Results suggest growth inhibition related to auxin accumulation, possibly combined with elevated putrescine content. Second, rooting induction seems to take place in both tobacco genotypes; however, the process of root formation is blocked in the mutant. The lack of initiation and expression phases of rooting in relation to auxin content in the mutant is discussed. [less ▲]

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See detailAre hyperhydric shoots of Prunus avium L. energy deficient?
Franck, Thierry ULg; Gaspar, Thomas ULg; Kevers, Claire ULg et al

in Plant Science (2001), 160(6), 1145-1151

The content of oxidized and reduced pyridine nucleotides and some enzymatic activities of the oxidative pentose phosphate and glycolytic pathways were compared in normal (NS, growing on agar) and ... [more ▼]

The content of oxidized and reduced pyridine nucleotides and some enzymatic activities of the oxidative pentose phosphate and glycolytic pathways were compared in normal (NS, growing on agar) and hyperhydric (HS, growing on gelrite) shoots of Prunus avium L. after 4 weeks of in vitro culture. The chlorophyll fluorescence from leaves and the redox capacity or the plasma membrane (reduction of exogenously added ferricyanide) of both types of shoots were recorded. The pool of oxidized and reduced pyridine nucleotides was lower in HS th;ln in NS. These results suggested a reduced metabolism of HS in comparison to normal ones. This hypothesis was also supported by other observations. First, chlorophyll fluorescence measurements showed a lower chlorophyll content and a slight reduction of the photosynthetic capacity in HS. Second, the low activity of some enzymes of oxidative pentose phosphate pathway (OPP) and glycolysis indicated a decline of these biochemical pathways in HS with the consequence of a reduced production of chemical energy in the form of NAD(P)H and ATP. Finally, the lower reduction of ferricyanide by I-IS suggested a lower rate of redox reactions at the level of the plasma membrane of these shoots in comparison to NS. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved. [less ▲]

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See detailSomatic embryogenesis of Panax ginseng in liquid cultures: a role for polyamines and their metabolic pathways
Kevers, Claire ULg; Le Gal, Nathalie; Monteiro, Marta et al

in Plant Growth Regulation (2000), 31(3), 209-214

A callus with embryogenic capacity was generated from root sections of Panax ginseng and used as an inoculum source for embryogenic liquid cultures in a three-step process: - a suspension culture of cell ... [more ▼]

A callus with embryogenic capacity was generated from root sections of Panax ginseng and used as an inoculum source for embryogenic liquid cultures in a three-step process: - a suspension culture of cell aggregates in the presence of an auxin/cytokinin mixture, - an induction medium containing auxin only (for 5 to 30 days), - a regeneration medium containing cytokinin only (for one month). Up to 25 embryos were recovered per 2.5 g of aggregates in these conditions. Incorporation of polyamines or their precursors arginine and ornithine into either the induction or regeneration media increased the number of embryos produced by up to 4 times. Inhibitors of both biosynthesis and biodegradation of polyamines reduced the number of embryos. These results support earlier findings of the role of polyamines in the process of somatic embryogenesis. The success of these liquid cultures opens up the possibility of producing somatic embryos of Panax ginseng in bioreactors. [less ▲]

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See detailIntegrating phytohormone metabolism and action with primary biochemical pathways. II. Interrelationships between disturbed nitrogen and carbon metabolism and changes in hormonal concentrations and sensitivities in tissue cultures
Gaspar, Thomas ULg; Bisbis, Badia; Kevers, Claire ULg et al

in Greppin, Hubert; Penel, Claude; Broughton, Walter (Eds.) et al Integrated Plant Systems (2000)

The paper begins with a review of the concept of neoplastic progressions in plant tissue cultures, with the progressive acquisition of (a relative) independence to the hormones auxins and cytokinins. It ... [more ▼]

The paper begins with a review of the concept of neoplastic progressions in plant tissue cultures, with the progressive acquisition of (a relative) independence to the hormones auxins and cytokinins. It takes advantage of the deviations of carbon and nitrogen metabolisms shown in these particular cases, to illustrate the interdependence with the metabolisms of the hormones (and increased sensitivities to) polyamines and ethylene. These results provide additional examples of the changing concepts in hormonology. [less ▲]

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See detailIntegrating phytohormone metabolism and action with primary biochemical pathways. I. Interrelationships between auxins, cytokinins, ethylene and polyamines in growth and development processes
Gaspar, Thomas ULg; Kevers, Claire ULg; Hausman, Jean-François et al

in Greppin, Hubert; Penel, Claude; Broughton, Walter (Eds.) et al Integrated Plant Systems (2000)

The paper begins with a review of the phytohormone (plant hormone) concept vs the sense of the mammalian hormones. The term "plant growth regulators" including new naturally occurring substances is ... [more ▼]

The paper begins with a review of the phytohormone (plant hormone) concept vs the sense of the mammalian hormones. The term "plant growth regulators" including new naturally occurring substances is discussed in regard to their effects on both growth and development processes, and possible different mechanisms of action in two different physiological directions. Mutual interactions between auxins, cytokinins, ethylene and polyamines are examined in several growth and development processes, showing the complexity of approach of the hormonal actions in plants . The indissociability of some hormonal relationships, and their obligatory integration with primary biochemical pathways is finally shown. [less ▲]

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See detailThe recalcitrance to rooting of the micropropagated shoots of the rac tobacco mutant: Implications of polyamines and of the polyamine metabolism
Faivre-Rampant, Odile; Kevers, Claire ULg; Dommes, Jacques ULg et al

in Plant Physiology & Biochemistry (2000), 38(6), 441-448

Rooting of wild-type tobacco (Nicotiana tabacum cv. Xanthi) shoots raised in vitro was promoted by polyamines in the absence of any other growth regulator and was inhibited by two inhibitors of polyamine ... [more ▼]

Rooting of wild-type tobacco (Nicotiana tabacum cv. Xanthi) shoots raised in vitro was promoted by polyamines in the absence of any other growth regulator and was inhibited by two inhibitors of polyamine metabolism. The auxin insensitive and recalcitrant to rooting rac mutant shoots did not respond to the same treatments. The activities of arginine decarboxylase (ADC), ornithine decarboxylase (ODC), diamine oxidase (DAO), polyamine oxidase (PAO) and transglutaminases (TGases), and the titres of free and conjugated polyamines were estimated in the whole shoots and the basal parts of the stems of both tobaccos in the course of multiplication in vitro. The rac shoots grew at a lower rate. The wild-type rooted from the 7th day without special treatment. During the second week of culture, the shoots of both tobaccos were actively growing and showed an increase in ADC, ODC, DAO, PAO and TGase activities. Afterwards all these activities declined. These changes were concomitant with an increase in the polyamine contents (free and conjugated). Biosynthesis and oxidation of polyamines apparently occurred simultaneously and seemed directly correlated. In the basal part of the mutant stems however, the accumulation of free and conjugated putrescine as well as the transient increase in biosynthetic enzyme activities were delayed compared to the wild-type. These results are discussed in relation to growth behaviour and to root formation. (C) 2000 Editions scientifiques et medicales Elsevier SAS. [less ▲]

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See detailLoss of plant organogenic totipotency in the course of in vitro neoplastic progression
Gaspar, Thomas ULg; Kevers, Claire ULg; Bisbis, Badia et al

in In Vitro Cellular & Developmental Biology-Plant (2000), 36(3), 171-181

The aptitude for organogenesis from normal hormone-dependent cultures very commonly decreases as the tissues are serially subcultured. The reasons for the loss of regenerative ability may vary under ... [more ▼]

The aptitude for organogenesis from normal hormone-dependent cultures very commonly decreases as the tissues are serially subcultured. The reasons for the loss of regenerative ability may vary under different circumstances: genetic variation in the cell population, epigenetic changes, disappearance of an organogenesis-promoting substance, etc. The same reasons may be evoked for the progressive and eventually irreversible loss of organogenic totipotency in the course of neoplastic progressions from hormone-independent tumors and hyperhydric teratomas to cancers. As in animal cells, plant cells at the end of a neoplastic progression have probably undergone several independent genetic accidents with cumulative effects. They indeed are characterized by atypical biochemical cycles from which they are apparently unable to escape. The metabolic changes are probably not the primary defects that cause cancer, rather they may allow the cells to survive. How these changes, namely an oxidative stress, affect organogenesis is not known. The literature focuses on somatic mutations and epigenetic changes that cause aberrant regulation of cell cycle genes and their machinery. [less ▲]

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See detailInteractions between polyamine and ethylene metabolisms in a hormone autonomous sugarbeet callus
Bisbis, Badia; Kevers, Claire ULg; Dommes, Jacques ULg et al

in Journal of Plant Physiology (2000), 157(1), 24-30

In a fully habituated non-organogenic sugarbeet callus (HNO) overproducing polyamines and underproducing ethylene (in comparison with its normal hormone-dependent counterpart), the question raised about a ... [more ▼]

In a fully habituated non-organogenic sugarbeet callus (HNO) overproducing polyamines and underproducing ethylene (in comparison with its normal hormone-dependent counterpart), the question raised about a possible competition between these two metabolites for their common precursor, S-adenosyl-methionine (SAM). The experimental strategy consisted in determining the effects of exogenous polyamines and inhibitors of polyamine biosynthetic pathway on growth, polyamine accumulation and ethylene production. Exogenous putrescine or spermidine decreased polyamine contents and ethylene production. Inhibitors of the diamine putrescine biosynthesis, DFMO and DFMA, induced a reduction of both polyamine content and ethylene production with an increase of HNO callus growth. However, when a mixture of the two inhibitors was used, an increase of ethylene production was observed without any effect on growth. The inhibitors of spermidine synthase (CHA) and of SAM decarboxylase (MGBG) also decreased polyamine content and ethylene production with different effects on growth according to the concentrations used. The combination of the two inhibitors (CHA + MGBG) increased ethylene production of the HNO callus. The effect of growth regulators (auxin and cytokinin) on growth and ethylene production of HNO callus is also discussed. These results suggest that polyamines affect directly the ethylene biosynthesis. In the absence of an exogenous hormonal control, the lower ethylene metabolism of HNO callus could not be explained by a competition with polyamines for their common precursor. [less ▲]

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See detailFlow cytometry estimation of nuclear size and ploidy level of habituated calli of sugar beet
Kevers, Claire ULg; Greimers, Roland ULg; Franck, Thierry ULg et al

in Biologia Plantarum (1999), 42(3), 321-332

A fully habituated (auxin- and cytokinin-independent) self-regenerating (organogenic) sugar beet cell line (HO) and a fully habituated non-organogenic one (HNO) derived from the former one, were analyzed ... [more ▼]

A fully habituated (auxin- and cytokinin-independent) self-regenerating (organogenic) sugar beet cell line (HO) and a fully habituated non-organogenic one (HNO) derived from the former one, were analyzed as to their nuclear size and DNA content. Flow cytometry and image analysis were used and cells of certified diploid leaves of the same sugar beet strain served as controls. The HNO cells had been shown previously to have many characteristics of cancerous cells. The analyses made on leaves and HNO cells indicated the presence of only one population of cycling cells. In HO cells. two cycling populations were detected: the first one had the same DNA content as the leaves while the second one contained two fold more DNA than the first population. HNO cells showed the higher nuclear size and DNA content. HNO cells also showed evidence of aneuploidy. Thus, nuclear size, DNA content and ploidy level increase together with the neoplasic progression to culminate in HNO cells with the loss of organogenic totipotency. [less ▲]

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See detailDetection of Nucleic Acids in the Attomole Range Using Polybiotinylated Oligonucleotide Probes
Zecchini, Vincent; Caucheteux, Danièle; Gretry, Jeau et al

in BioTechniques (1995), 19(2), 286-90

This article describes the optimization of the hybridization signal obtained with biotinylated oligonucleotides. Optimal number and positions of biotin moieties on a 33-base oligonucleotide probe were ... [more ▼]

This article describes the optimization of the hybridization signal obtained with biotinylated oligonucleotides. Optimal number and positions of biotin moieties on a 33-base oligonucleotide probe were determined. The quality of avidin-peroxidase conjugate and the choice of chromogenic substrate influenced detection sensitivity. A signal amplification method was also developed for avidin enzymatic conjugates. These improvements allowed the detection of less than 0.02 fmol of target DNA. [less ▲]

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See detailIdentification of Clostridium tyrobutyricum and related species using sugar fermentation, organic acid formation and DNA probes based on 16S rRNA sequences
Klijn, N.; Bovie, C.; Dommes, Jacques ULg et al

in Systematic and Applied Microbiology (1994), 17(2), 249-256

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See detailDiurnal Rhythmicity in the Pattern of Mrnas in the Leaves of Sinapis Alba
Cremer, Frédéric ULg; Dommes, Jacques ULg; Van de Walle, Claude ULg et al

in Plant Physiology (1990), 94(4), 1590-1597

Previous studies have shown that certain specific leaf mRNAs exhibit a diurnal rhythmicity in their quantity in higher plants. To determine whether this situation is restricted to a few mRNAs, or affects ... [more ▼]

Previous studies have shown that certain specific leaf mRNAs exhibit a diurnal rhythmicity in their quantity in higher plants. To determine whether this situation is restricted to a few mRNAs, or affects a large number, we have used in vitro translation and two-dimensional polyacrylamide gel electrophoresis to analyze the mRNA complement in leaves of Sinapis alba at different times during an 8-hour/16-hour day/night cycle. A method for the visual analysis of two-dimensional polyacrylamide gel electrophoresis was also developed. This method selected, at each sampling time, spots that were significant. It then selected, between two sampling times, intensity changes that were significant at the 0.02 confidence level. During a day/night cycle, complex rhythmic changes affected about 10% of the mRNAs. Nineteen different rhythm patterns were found. These 19 patterns fell into four main classes: mRNAs that increase during the light period and decrease during the dark, mRNAs that increase and then decrease during the light period, mRNAs that decrease during the light period and increase during the dark period, and mRNAs that increase and then decrease during the dark period. [less ▲]

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