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See detailWhat we have learned about the physiology of in vitro adventitious rooting of woody plants and how it relates to improvements in the practice
Kevers, Claire ULg; Hausman, Jean-françois; Faivre-Rampant, Odile et al

in Niemi, Karoliina (Ed.) Adventitious root formation of forest trees and horticultural plants - from genes to applications (2009)

Natural auxins and synthetic analogs are the most powerful exogenous stimulators of adventitious rooting of ligneous as well as for herbaceous cuttings. For several years we have investigated the ... [more ▼]

Natural auxins and synthetic analogs are the most powerful exogenous stimulators of adventitious rooting of ligneous as well as for herbaceous cuttings. For several years we have investigated the physiology of rooting, including the metabolism of endogenous auxins and their molecular mechanisms of action. Our work has resulted in discoveries leading to practical strategies allowing faster and improved rooting of cuttings from shoots raised in vitro, and subsequently resulting in roots better adapted for acclimatization and to overcome so-called (apparent) recalcitrance-to-rooting of some species. In this chapter we describe: (i) how variation in auxin treatments during rooting can be used to regulate the endogenous levels of auxins; (ii) the importance of not maintaining auxin treatment throughout the whole rooting process, thereby the endogenous auxin level itself not always being high; (iii) the division of the organogenetic process into at least three main rooting interdependent phases, i.e. induction, initiation, and expression, with different durations depending on the species and with different requirements for each phase, and (iv) how polyamines, even if less effective from outside, and their metabolism are as important as auxins in the rooting process. We will also describe how cross-talk between hormones, manipulations with related genes and mutants, and some similarities between the induction of rooting and evocation of flowering, offer new tools for further progress in the field. [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 detailOptimisation of Panax ginseng liquid cell cultures for biomass accumulation and ginsenoside production.
Kevers, Claire ULg; Bare, Gislain; Gaspar, Thomas ULg et al

in HVOSLEF-EIDE, Anne Kathrine; PREIL, Walter (Eds.) Liquid Culture Systems for in vitro Plant Propagation (2005)

Solid calli and derived liquid cell cultures were initiated from one-year-old roots of Panax ginseng CA Meyer. Half-strength Murashige and Skoog medium supplemented classically with an auxin and a ... [more ▼]

Solid calli and derived liquid cell cultures were initiated from one-year-old roots of Panax ginseng CA Meyer. Half-strength Murashige and Skoog medium supplemented classically with an auxin and a cytokinin did not appear favourable for biomass accumulation nor for a high ginsenoside content. Changes in the levels of mineral nutrients, sucrose and growth regulators were preliminary investigated here to improve growth and ginsenoside production in liquid cultures. The hypothesis that ginseng cells released growth inhibitors in the medium was not supported by the results obtained in experiments involving frequent transfers to fresh growth medium [less ▲]

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See detailHyperhydricity of Prunus avium shoots cultured on gelrite: a controlled stress response
Franck, Thierry ULg; Kevers, Claire ULg; Gaspar, Thomas ULg et al

in Plant Physiology & Biochemistry (2004), 42(6), 519-527

Hyperhydricity is a physiological disorder frequently affecting shoots vegetatively propagated in vitro. Hyperhydric shoots are characterised by a translucent aspect due to a chlorophyll deficiency, a not ... [more ▼]

Hyperhydricity is a physiological disorder frequently affecting shoots vegetatively propagated in vitro. Hyperhydric shoots are characterised by a translucent aspect due to a chlorophyll deficiency, a not very developed cell wall and a high water content. Hyperhydricity of Prunus avium shoots was expressed in vitro in one multiplication cycle by replacing the gelling agent agar (normal shoots: NS) by gelrite (hyperhydric shoots: HS). P. avium shoots evolving towards the hyperhydric state produced higher amounts of ethylene, polyamines (PAs) and proline, which are substances considered as stress markers. A higher activity of glutathione peroxidase (GPX; EC 1.11.1.9), involved in organic hydroperoxide elimination, suggested an increased production of these compounds in HS. The unchanged free fatty acid composition indicated no HS membrane damages compared to NS. The ploidy level of HS nuclei was not affected, but the bigger size and the lower percentage of nuclei during the S phase suggested a slowing down of the cell cycle. The results argued for a stress response of the HS, but no signs of oxidative damages of lipid membrane and nucleus were observed. The discussion points out paradoxical results in a classical analysis of stress and suggests an alternative way of defense mechanisms in HS, involving homeostatic regulation and controlled degradation processes to maintain integrity and vital functions of the cell. (C) 2004 Elsevier SAS. All rights reserved. [less ▲]

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See detailEffect of NaCl and mannitol iso-osmotic stresses on proline and free polyamine levels in embryogenic Fraxinus angustifolia callus
Tonon, Giustino; Kevers, Claire ULg; Faivre-Rampant, Odile et al

in Journal of Plant Physiology (2004), 161(6), 701-708

With the aim to differentiate the ionic and osmotic components of salt stress, short and long-term changes in free polyamines and proline induced by iso-osmotic concentrations of NaCl (0.1 mol/L and 0 ... [more ▼]

With the aim to differentiate the ionic and osmotic components of salt stress, short and long-term changes in free polyamines and proline induced by iso-osmotic concentrations of NaCl (0.1 mol/L and 0.2mol/L) and mannitol (0.2mol/L and 0.4mol/L) were determined in Fraxinus angustifolia callus. The peculiarities of the short-term responses were: i) a very early (30 min) and temporary increase in Putrescine (Pu) and Spermine (Spm) as a consequence of salt treatment, and ii) a continuous accumulation of Spermidine (Spd) and Spm in response to mannitol. The changes of Proline (Pro) were quite limited both in the short and in the long term, and generally occurred later than Polyamine (PAs) changes took place, suggesting a regulatory mechanism of PAs metabolism on Pro biosynthesis. In the long-term, no drastic accumulations of Pro or PAs in response to NaCl and mannitol were observed, suggesting that their physiological role is unlikely to be that of osmo-compatible solutes in this plant system. The salt induced a higher callus growth inhibition effect than did mannitol and this inhibition was associated with the reduction of endogenous levels of PAs, especially Pu. However, while a diverging time course was observed under lethal salt concentration (0.2 mol/L NaCl), a high parallelism in the endogenous changes of Pro and Pu was observed under all non-lethal conditions (control - 0.2 and 0.4 mol/L mannitol - 0.1 mol/L NaCl). Therefore the synchronous changes of Pro and Pu can be considered as a physiological trait associated with cell survival. These results indicate a strong metabolic co-ordination between PAs and Pro pathways and suggest that the metabolic fluxes through these pathways start competing only when the stress level is high enough to be lethal for cells. [less ▲]

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See detailHyperhydricity of micropropagated shoots: a typically stress-induced change of physiological state
Kevers, Claire ULg; Franck, Thierry ULg; Strasser, Reto et al

in Plant Cell, Tissue & Organ Culture (2004), 77(2), 181-191

Hyperhydricity of micropropagated shoots, formerly called vitrification, undoubtedly results from growth and culture conditions, subjectively reputated as stressing factors: wounding, infiltration of soft ... [more ▼]

Hyperhydricity of micropropagated shoots, formerly called vitrification, undoubtedly results from growth and culture conditions, subjectively reputated as stressing factors: wounding, infiltration of soft culture medium, generally of a high ionic strength, rich in nitrogen and in growth regulators in a special balance, in a humid and gaseous confined atmosphere. Stress is (objectively) defined as a disruption of homeostasis resulting from a constraint escaping the usual flexibility of metabolism. It induces another temporary (reversible) or definitive (irreversible) thermodynamic physiological state. The state-change concept developed by Strasser (1988) and Strasser and Tsimilli-Michael (2001) is applicable to the phenomenon of hyperhydricity. An appraisal of the redox capacities of hyperhydrated shoots together with a study of some enzymic activities that catalyse pentose phosphate and glycolytic pathways has indeed shown that such shoots have evolved towards a temporary state of lower differentiation or a juvenile state with a sufficient activity to survive and to defend themselves. [less ▲]

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See detailWood formation in in vitro propagated walnut shoots in relation with root formation and development
Kevers, Claire ULg; Bisbis, Badia; Crèvecoeur, Michèle et al

in Acta Botanica Gallica : Bulletin de la Société Botanique de France (2004), 151(1), 45-53

Lignification and xylem cell multiplication for wood formation were examined in in vitro propagated walnut shoot cuttings after transfer on an auxin-containing rooting medium for one week and subsequently ... [more ▼]

Lignification and xylem cell multiplication for wood formation were examined in in vitro propagated walnut shoot cuttings after transfer on an auxin-containing rooting medium for one week and subsequently during root development in vermiculite in the absence of growth regulators. Lignification in the shoot stems started immediately after the exogenous auxin treatment which implied changes in peroxidase activity and in free IAA levels. Sustained lignification required the completion of the following rooting phases. The lignin was exclusively located in xylem cells, the number of which increased with the number of developing roots. The mutual interactions between the aerial parts of the plants and their roots are discussed. [less ▲]

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See detailComparative titration of ginsenosides by different techniques in commercial ginseng products and callus cultures
Kevers, Claire ULg; Jacques, Philippe; Gaspar, Thomas ULg et al

in Journal of Chromatographic Science (2004), 42(10, Nov-Dec), 554-558

The ginsenoside content of different ginseng species (Panax ginseng, P. quinquefolium, and P. vietnamensis) from different sources (roots from field-grown plants or from in vitro cultures, cells from ... [more ▼]

The ginsenoside content of different ginseng species (Panax ginseng, P. quinquefolium, and P. vietnamensis) from different sources (roots from field-grown plants or from in vitro cultures, cells from solid calluses or from liquid cultures, commercial powders, and suspensions) is evaluated by means of a new high-performance thin-layer chromatography (HPTLC) technique combining an automatic TLC sampler and scanner. The results are compared with those obtained through more classical gross spectrometric and high-performance liquid chromatography (HPLC) techniques. HPTLC and HPLC allow the separation and estimation of the different ginsenosides. For this, HPTLC is faster and simpler than HPLC. Both techniques determine less amounts of ginsenosides than spectrophotometry, which displays overestimated values caused by light absorption by contaminating osides. In vitro cultured cells and roots contain the same ginsenosides as those produced by their mother plants, although at quite lower levels. The culture media also accumulates ginsenosides. [less ▲]

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See detailSynthesis and activity of another seleniated auxin: 2,4-dichlorophenylselenoacetic acid
Tadino, Vincent; Faez, Juan Mareque; Christiaens, Léon ULg et al

in Plant Growth Regulation (2003), 40(3), 197-200

The synthesis of 2,4-dichlorophenylselenoacetic acid (2,4-D-Se) may be completed in three steps starting from 2,4-dichloroaniline. The selenium is inserted in the molecule by reaction of a diazonium salt ... [more ▼]

The synthesis of 2,4-dichlorophenylselenoacetic acid (2,4-D-Se) may be completed in three steps starting from 2,4-dichloroaniline. The selenium is inserted in the molecule by reaction of a diazonium salt with potassium selenocyanate. 2,4-D-Se has been tested as an auxin in several bioassays including the regeneration of somatic embryos, adventitious root formation and the associated temporary increase of endogenous auxins at the induction phase, and callus formation, and compared with the natural auxin indoleacetic acid (IAA), the classical synthetic auxin(s) naphthaleneacetic acid (NAA) and/or 2,4-dichlorophenoxyacetic acid (2,4-D), and with the synthetic seleniated IAA, 3-(benzo[b] selenienyl) acetic acid, BSAA. These biological assays classified 2,4-D-Se together with BSAA among the most powerful synthetic auxins. The role of selenium is briefly discussed. [less ▲]

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See detailRooting blockage in the tobacco rac mutant occurs at the initiation phase, and induces diversion to xylem differentiation
Faivre-Rampant, Odile; D'Angeli, S.; Falasca, G. et al

in Plant Biosystems (2003), 137(2), 163-174

The rac mutant of Nicotiana tabacum L. cv. Xanthii is impaired in adventitious root formation. The objective of the present study was to determine whether or not the root induction phase occurs in the rac ... [more ▼]

The rac mutant of Nicotiana tabacum L. cv. Xanthii is impaired in adventitious root formation. The objective of the present study was to determine whether or not the root induction phase occurs in the rac mutant, and if so, to determine what causes the induced cells to become incapable of organising root primordia. To this end, rac and wild-type shoots were cultured in vitro for 7 days under conditions suitable for obtaining roots in the wild-type (i.e., exposure to 5 muM indole-3-butyric acid for 4 h, and then transfer to hormone-free medium), and then histologically and biochemically analysed during culture. The variations in peroxidase activity, and in cellular levels of auxins and polyamines revealed that the induction phase occurs in rac shoots, although it lasts longer than in the wild-type ones. Furthermore, both auxin and polyamines were consistently higher in rac shoots compared to the wild-type. After induction, auxin and putrescine levels abruptly decreased in the wild-type shoots, whereas they decreased much more slowly in the rac mutant. The histological analysis of the wild-type shoots showed that the abrupt decrease in auxin and polyamine levels were correlated with a normal initiation phase. In fact, wild-type shoots showed cell divisions in the procambium already at day 2, resulting in the formation of root primordia at day 4, and in root emergence between days 5 and 7. In rac shoots, despite the fact that the procambium cells were activated to undergo cell division, the initiation phase was highly perturbed, and the procambial cells developed tracheary elements instead of adventitious roots. The different morphogenic responses of the two genotypes are discussed in the light of the differences in auxin content after the induction phase. [less ▲]

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See detailRestart of lignification in micropropagated walnut shoots coincides with rooting induction
Bisbis, Badia; Kevers, Claire ULg; Crèvecoeur, Michèle et al

in Biologia Plantarum (2003), 47(1), 1-5

The lignin content of walnut shoots did not change during in vitro shoot Multiplication. Lignin content started to increase as soon as shoots were passed to a rooting medium with auxin. Exogenous auxin ... [more ▼]

The lignin content of walnut shoots did not change during in vitro shoot Multiplication. Lignin content started to increase as soon as shoots were passed to a rooting medium with auxin. Exogenous auxin (applied for rooting) Caused a transient elevation of the endogenous free indoleacetic acid (IAA) content with a Simultaneous decrease of peroxidase activity. These events typically marked the completion of the rooting inductive phase (before any visible histological event. that is before the cell divisions beginnin- the rootin- initiation phase). This meant that either the given exogenous auxin or the endogenous IAA has served as signal for the stimulation of lignification. Continued increase of lignification in the shoots required completion of root formation; this increase indeed was slown down when root emergence did not occur. It was further shown that lionification varied conversely to the content of the Soluble Phenol Content. itself apparently being related to the activity of phenylalanine ammonia-lyase activity. [less ▲]

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See detailChanging concepts in plant hormone action
Gaspar, Thomas ULg; Kevers, Claire ULg; Faivre-Rampant, Odile et al

in In Vitro Cellular & Developmental Biology-Plant (2003), 39(2, MAR-APR), 85-106

A plant hormone is not, in the classic animal sense, a chemical synthesized in one organ, transported to a second organ to exert a chemical action to control a physiological event. Any phytohormone can be ... [more ▼]

A plant hormone is not, in the classic animal sense, a chemical synthesized in one organ, transported to a second organ to exert a chemical action to control a physiological event. Any phytohormone can be synthesized everywhere and can influence different growth and development processes at different places. The concept of physiological activity under hormonal control cannot be dissociated from changes in concentrations at the site of action, from spatial differences and changes in the tissue's sensitivity to the compound, from its transport and its metabolism, from balances and interactions with the other phytohormones, or in their metabolic relationships, and in their signaling pathways as well. Secondary messengers are also involved. Hormonal involvement in physiological processes can appear through several distinct manifestations (as environmental sensors, homeostatic regulators and spatio-temporal synchronizers, resource allocators, biotime adjusters, etc.), dependent on or integrated with the primary biochemical pathways. The time has also passed for the hypothesized 'specific' developmental hormones, rhizocaline, caulocaline, and florigen: root, stem, and flower formation result from a sequential control of specific events at the right places through a coordinated control by electrical signals, the known phytohormones and nonspecific molecules of primary and secondary metabolism, and involve both cytoplasmic and apoplastic compartments. These contemporary views are examined in this review. [less ▲]

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See detailHow hyperhydric shoots try to survive
Franck, Thierry ULg; Kevers, Claire ULg; Gaspar, Thomas ULg et al

in Free Radical Research (2003), 37(Suppl. 1), 74-74

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See detailThe beneficial role of different auxins and polyamines at successive stages of somatic embryo formation and development of Panax ginseng in vitro
Kevers, Claire ULg; Gaspar, Thomas ULg; Dommes, Jacques ULg

in Plant Cell, Tissue & Organ Culture (2002), 70(2), 181-188

The production of viable plantlets via somatic embryogenesis in Panax ginseng requires different culture media corresponding to successive developmental stages. The effects of several auxins and ... [more ▼]

The production of viable plantlets via somatic embryogenesis in Panax ginseng requires different culture media corresponding to successive developmental stages. The effects of several auxins and polyamines have been tested at various steps. Multiplication of the embryogenic root-derived callus has been optimized on half-strength MS medium supplemented with 3-(benzo[b]selenyl)acetic acid (BSAA, a synthetic auxin) and kinetin; exogenously applied polyamines were deleterious at this stage, causing browning of the callus, diminished capacity of embryo initiation, and an increased tendency to hyperhydricity. BSAA again appeared to be the most favourable auxin at the initiation stage, but here its action was reinforced by the presence of polyamines, spermidine being the most efficient. Among the auxin needed at the next step, i.e., for the regeneration of embryos, the two seleniated auxins BSAA and seleniated 2,4-dichlorophenoxyacetic acid (2,4-D-Se) were the more efficient. For the harmonious development of plantlets, i.e., the simultaneous outgrowth of shoots and roots, the polyamines were favourable, with a greater efficiency for spermine. [less ▲]

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See detailConcepts in plant stress physiology. Application to plant tissue cultures
Gaspar, Thomas ULg; Franck, Thierry ULg; Bisbis, Badia et al

in Plant Growth Regulation (2002), 37(3), 263-285

Because the term stress is used, most often subjectively, with various meanings, this paper first attempts to clarify the physiological definition, and the appropriate terms as responses in different ... [more ▼]

Because the term stress is used, most often subjectively, with various meanings, this paper first attempts to clarify the physiological definition, and the appropriate terms as responses in different situations. The flexibility of normal metabolism allows the development of responses to environmental changes which fluctuate regularly and predictably over daily and seasonal cycles. Thus every deviation of a factor from its optimum does not necessarily result in stress. Stress begins with a constraint or with highly unpredictable fluctuations imposed on regular metabolic patterns that cause bodily injury, disease, or aberrant physiology. Stress is the altered physiological condition caused by factors that tend to alter an equilibrium. Strain is any physical and/or chemical change produced by a stress, i.e. every established condition, which forces a system away from its thermodynamic optimal state. The paper secondly summarises the Strasser's state-change concept which is precisely that suboptimality is the driving force for acclimation (genotype level) or adaptation (population level) to stress. The paper continues with the actual knowledge on the mechanisms of stress recognition and cell signalling. Briefly: plasma membranes are the sensors of environmental changes; phytohormones and second messengers are the transducers of information from membranes to metabolism; carbon balance is the master integrator of plant response; betwixt and between, some genes are expressed more strongly, whereas others are repressed. Reactive oxygen species play key roles in up- and down-regulation of metabolism and structure. The paper shows finally that the above concepts can be applied to plant tissue cultures where the accumulating physiological and genetical deviations (from a normal plant behaviour) are related to the stressing conditions of the in vitro culture media and of the confined environment. The hyperhydrated state of shoots and the cancerous state of cells, both induced under conditions of stress in in vitro cultures, are identified and detailed, because they perfectly illustrate the stress-induced state-change concept. It is concluded that stress responses include either pathologies or adaptive advantages. Stress may thus contain both destructive and constructive elements: it is a selection factor as well as a driving force for improved resistance and adaptive evolution. [less ▲]

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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 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 detailChanges in peroxidase activity, and level of phenolic compounds during light-induced plantlet regeneration from Eucalyptus camaldulensis Dehn. nodes in vitro
Arezki, Ouoimare; Boxus, Philippe; Kevers, Claire ULg et al

in Plant Growth Regulation (2001), 33(3), 215-219

Node cultures of Eucalyptus camaldulensis Dehn in Petri dishes in vitro under darkness in the presence of an auxin developed meristematic agglomerates (4 to 6 diameter), i.e. dense shoot clusters in which ... [more ▼]

Node cultures of Eucalyptus camaldulensis Dehn in Petri dishes in vitro under darkness in the presence of an auxin developed meristematic agglomerates (4 to 6 diameter), i.e. dense shoot clusters in which outgrowth of numerous successive buds is limited. Similar cultures under a 16 photoperiod produced small green plantlets with reduced leaves often presenting white hypertrophied lenticels and very short roots crowning the stem bases. The use of half-litre glass vials under light allowed direct development of well-developed rooted plantlets, either in the presence of the same auxin or in the presence of a cytokinin. Light favoured an increase in phenolic compounds and a reverse variation of peroxidase activity during the culture cycles. These aspects are discussed in terms of a possible regulation of the endogenous auxin level through a light control of peroxidase activity and the level of phenolic compounds. [less ▲]

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