References of "Tocquin, Pierre"
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See detailTranscriptomic analysis of Arabidopsis roots during flowering
D'Aloia, Maria ULg; Tocquin, Pierre ULg; Périlleux, Claire ULg

Poster (2010, February)

Contribution of the root system to the flowering process remains poorly studied. Part of the problem resides in its difficult isolation from the substrate, especially on adult plants. Taking advantage of ... [more ▼]

Contribution of the root system to the flowering process remains poorly studied. Part of the problem resides in its difficult isolation from the substrate, especially on adult plants. Taking advantage of an hydroponic device that allows synchronous growth and flowering of Arabidopsis thaliana (Tocquin et al., 2003), we performed global transcript profiling of roots during induction of flowering by a single long day (LD). Results were validated by real-time RT-PCR, and the expression patterns of selected probes were further analyzed in shoots and roots. Some of the genes that were identified in the microarray experiment were already known to be involved in the photoperiodic pathway of flowering in Arabidopsis, and hence were activated in both roots and shoots during the LD. These genes include, for example, components of light signaling or circadian machinery (e.g. GIGANTEA). Other genes providing new insights into the control of flowering at the whole plant level will be presented. Tocquin et al., (2003). BMC Plant Biology, 3: 2. [less ▲]

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See detailOptimization of the Production of the Amyloidogenic Variants of Human Lysozyme
Menzer, Linda ULg; Tocquin, Pierre ULg; Dony, Nicolas et al

Poster (2008, February 16)

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See detailVernalization-induced repression of FLOWERING LOCUS C stimulates flowering in Sinapis alba and enhances plant responsiveness to photoperiod.
D'Aloia, Maria ULg; Tocquin, Pierre ULg; Périlleux, Claire ULg

in New Phytologist (2008), 178(4), 755-65

Of the Brassicaceae, Sinapis alba has been intensively studied as a physiological model of induction of flowering by a single long day (LD), while molecular-genetic analyses of Arabidopsis thaliana have ... [more ▼]

Of the Brassicaceae, Sinapis alba has been intensively studied as a physiological model of induction of flowering by a single long day (LD), while molecular-genetic analyses of Arabidopsis thaliana have disclosed complex interactions between pathways controlling flowering in response to different environmental cues, such as photoperiod and vernalization. The vernalization process in S. alba was therefore analysed here. The coding sequence of S. alba SaFLC, which is orthologous to the A. thaliana floral repressor FLOWERING LOCUS C, was isolated and the transcript levels quantified in different conditions. Two-week-old seedlings grown in noninductive short days (SDs) were vernalized for 1-6 wk. Down-regulation of SaFLC was already marked after 1 wk of cold but 2 wk was needed for a significant acceleration of flowering. Flower buds were initiated during vernalization. When vernalization was stopped after 1 wk, repression of SaFLC was not stable but a significant increase in plant responsiveness to 16-h LDs was observed when LDs followed immediately after the cold treatment. These results suggest that vernalization does not only work when plants experience long exposure to cold during the winter: shorter cold periods might stimulate flowering of LD plants if they occur when photoperiod is increasing, such as in spring. [less ▲]

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See detailRapport final ARAPONIC - First spin-off n°315461
Tocquin, Pierre ULg; Périlleux, Claire ULg

Report (2007)

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See detailPlant-based production of human lysozyme mutants
Tocquin, Pierre ULg; Dumoulin, Mireille ULg; Dony, Nicolas ULg et al

Poster (2007)

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See detailAcclimation of Arabidopsis thaliana to long-term CO2 enrichment and nitrogen supply is basically a matter of growth rate adjustment
Tocquin, Pierre ULg; Ormenese, Sandra ULg; Pieltain, Alexandra ULg et al

in Physiologia Plantarum (2006), 128(4), 677-688

The long-term response of Arabidopsis thaliana to increasing CO2 was evaluated in plants grown in 800 mu l 1(-1) CO2 from sowing and maintained, in hydroponics, on three nitrogen supplies: "low," "medium ... [more ▼]

The long-term response of Arabidopsis thaliana to increasing CO2 was evaluated in plants grown in 800 mu l 1(-1) CO2 from sowing and maintained, in hydroponics, on three nitrogen supplies: "low," "medium" and "high." The global response to high CO2 and N-supply was evaluated by measuring growth parameters in parallel with photosynthetic activity, leaf carbohydrates, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) messenger RNA and protein, stomatal conductance (g(s)) and density. CO2 enrichment was found to stimulate biomass production, whatever the N-supply. This stimulation was transient on low N-supply and persisted throughout the whole vegetative growth only in high N-supply. Acclimation on low N-high CO2 was not associated with carbohydrate accumulation or with a strong reduction in Rubisco amount or activity. At high N-supply, growth stimulation by high CO2 was mainly because of the acceleration of leaf production and expansion while other parameters such as specific leaf area, root/shoot ratio and g, appeared to be correlated with total leaf area. Our results thus suggest that, in strictly controlled and stable growing conditions, acclimation of A. thaliana to longterm CO2 enrichment is mostly controlled by growth rate adjustment. [less ▲]

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See detailLeaf carbohydrate controls over Arabidopsis growth and response to elevated CO2: an experimentally based model
Rasse, Daniel; Tocquin, Pierre ULg

in New Phytologist (2006), 172(3), 500-513

Transient starch production is thought to strongly control plant growth and response to elevated CO2. We tested this hypothesis with an experimentally based mechanistic model in Arabidopsis thaliana ... [more ▼]

Transient starch production is thought to strongly control plant growth and response to elevated CO2. We tested this hypothesis with an experimentally based mechanistic model in Arabidopsis thaliana. Experiments were conducted on wild-type (WT) A. thaliana, starch-excess (sex1) and starchless (pgm) mutants under ambient and elevated CO2 conditions to determine parameters and validate the model. The model correctly predicted that mutant growth is approx. 20% of that in WT, and the absolute response of both mutants to elevated CO2 is an order of magnitude lower than in WT. For sex1, direct starch unavailability explained the growth responses. For pgm, we demonstrated experimentally that maintenance respiration is proportional to leaf soluble sugar concentration, which gave the necessary feedback mechanism on modelled growth. Our study suggests that the effects of sugar-starch cycling on growth can be explained by simple allocation processes, and the maximum rate of leaf growth (sink capacity) exerts a strong control over the response to elevated CO2 of herbaceous plants such as A. thaliana. [less ▲]

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See detailThe FLC-dependent vernalization pathway in Sinapis alba.
D'Aloia, Maria ULg; Tocquin, Pierre ULg; Périlleux, Claire ULg

in Comparative Biochemistry and Physiology. Part A, Physiology (2006), 143A

In many plants, flowering is promoted by a long exposure to cold, a process known as ‘vernalisation’. In Arabidopsis, the vernalisation pathway was shown to promote flowering via the repression of the ... [more ▼]

In many plants, flowering is promoted by a long exposure to cold, a process known as ‘vernalisation’. In Arabidopsis, the vernalisation pathway was shown to promote flowering via the repression of the FLOWERING LOCUS C (FLC) gene, which encodes a repressor of flowering. As far as we know, the genetical control of flowering is conserved among Brassicaceae, and we reported elsewhere cloning of flowering times genes of the photoperiodic pathway in Sinapis alba, based on sequence similarity with Arabidopsis. However, little is known about vernalisation in Sinapis. We therefore undertook a physiological and molecular study of this process. Plants of Sinapis were grown in non inductive short days and vernalised at 7°C, at the seedling stage. Vernalisation was found to accelerate flowering and an increasing effect was observed for vernalisation treatments longer than 2 weeks. We cloned an FLC-like sequence (SaFLC) by screening a cDNA library, and used it as a probe to perform expression analyses. We observed that SaFLC was almost completely repressed after 1 week of vernalisation, but repression was stable only after 2 weeks, which is consistent with the fact that 2-week is the minimal duration of vernalisation that promotes flowering. Hence the molecular mechanisms of vernalisation seem to be conserved in Sinapis and Arabidopsis. [less ▲]

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See detailContribution à l'étude des effets de l'enrichissement de l'atmosphère sur la croissance des plantes herbacées. Analyse et modélisation chez Arabidopsis thaliana.
Tocquin, Pierre ULg

Doctoral thesis (2005)

L’enrichissement en CO2 de l’atmosphère dû aux activités humaines est considéré comme la cause principale des perturbations climatiques actuelles ou 'global change'. Chez les plantes C3, on constate ... [more ▼]

L’enrichissement en CO2 de l’atmosphère dû aux activités humaines est considéré comme la cause principale des perturbations climatiques actuelles ou 'global change'. Chez les plantes C3, on constate généralement que l'enrichissement en CO2 provoque à court terme une stimulation de la photosynthèse. On peut donc s'attendre à ce que cette stimulation photosynthétique et la production supplémentaire de sucres qui en résulte agissent positivement sur la croissance des plantes. Cependant, il apparaît souvent que les plantes « s'acclimatent » à l'enrichissement en CO2 de sorte que l'effet positif sur la croissance est moindre que si la stimulation initiale était maintenue. Les sucres eux-mêmes pourraient contrôler cette acclimatation en exerçant un feed-back négatif sur la photosynthèse. Cela implique que lorsque la capacité de la plante à utiliser ce surplus des sucres est réduite, dans le cas d’une carence en azote par exemple, la réponse à l'enrichissement en CO2 peut également être affectée. Le but de notre travail était d’étudier et de modéliser les mécanismes qui contrôlent la réponse des plantes au CO2 en utilisant la plante modèle A. thaliana. Notre volonté était d’envisager, ensemble, les aspects physiologiques et moléculaires de cette réponse au niveau de la plante entière. Cela a nécessité la mise au point de deux équipements originaux. Le premier est un système de culture sur milieu liquide ou « hydroponique » permettant le contrôle et la manipulation de la disponibilité en éléments minéraux. Le second est un dispositif permettant la mesure des échanges gazeux d’une plante entière d’A. thaliana et la mesure de certains paramètres photosynthétiques en réponse à l’enrichissement en CO2. Dans un premier temps, nous avons étudié l’impact du doublement de la teneur en CO2, soit 800 ppm, sur la croissance, la photosynthèse et la production des sucres lorsqu’il est appliqué dès le semis. Nous avons comparé la réponse de plantes soumises à trois régimes azotés et observé que l’enrichissement en CO2 stimulait la croissance lorsque la disponibilité en azote n’est pas limitante. Bien que l’activité photosynthétique soit réduite chez les plantes carencées en azote, cette réduction ne semble pas, dans nos conditions expérimentales, être le résultat d’une répression contrôlée par les sucres. Nos résultats indiquent plutôt que, placées dans des conditions environnementales stables, les plantes ajustent leur vitesse de croissance afin de maintenir un équilibre entre leur capacité à produire et à utiliser les sucres. Dans une seconde approche, nous avons tenté de modéliser les mécanismes principaux qui sous-tendent la réponse d’A. thaliana à l’enrichissement en CO2. L’observation que la croissance de mutants incapables d’utiliser l’amidon comme réserve transitoire de sucres n’était pas stimulée par l’augmentation de la teneur en CO2 nous a incités à centrer ce modèle sur l’allocation des sucres et en particulier la synthèse d’amidon. Les fonctions qui constituent ce modèle ont été mesurées expérimentalement et certaines n’ont pu être obtenues que grâce à l’analyse de mutants du métabolisme de l’amidon. Nous avons montré que le modèle était capable de prédire la croissance d’A. thaliana et de mutants du métabolisme de l’amidon sous une teneur ambiante ou double en CO2, suggérant que la synthèse d’amidon pourrait avoir, chez A. thaliana, une importance cruciale dans la réponse à l’enrichissement en CO2. Par ailleurs, cette modélisation a mis également en évidence l’importance du paramètre « vitesse de croissance » dans la réponse au CO2 et renforce donc les conclusions de notre étude expérimentale. Les outils que nous avons développés nous ont permis d’étudier, globalement, la réponse d’A. thaliana à l’enrichissement en CO2 dans un environnement stable et contrôlé dès le semis. Les résultats que nous avons obtenus sont par certains aspects – absence d’accumulation de sucres et de répression de la Rubisco sous une atmosphère enrichie en CO2 – atypiques. Ils mettent en lumière l’importance que jouent les conditions expérimentales dans les études sur la réponse des plantes au CO2 et, en particulier, sur l’interprétation des résultats qui en découlent. En effet, nos observations remettent en question le rôle des sucres dans le contrôle de l’acclimatation de la photosynthèse au CO2. Elles valident cependant notre stratégie expérimentale et notamment l’utilisation d’Arabidopsis dans une approche visant à modéliser un processus complexe, tel que celui de la réponse à l’augmentation de la teneur atmosphérique en CO2. [less ▲]

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See detailDesign of a versatile device for measuring whole plant gas exchanges in Arabidopsis thaliana
Tocquin, Pierre ULg; Périlleux, Claire ULg

in New Phytologist (2004), 162(1), 223-229

Because of its small size and rosette growth habit, measuring gas exchanges in Arabidopsis thaliana is difficult with standard leaf cuvettes. Here, we designed a versatile system that is usable at the ... [more ▼]

Because of its small size and rosette growth habit, measuring gas exchanges in Arabidopsis thaliana is difficult with standard leaf cuvettes. Here, we designed a versatile system that is usable at the whole rosette level, as small as possible for fast and accurate measurements, but adaptable to plant size, and suitable for in situ measurements whatever the growing substrate of the plant. This cuvette is in two parts: the basic unit, which contains the sensors and is connected to the infra-red gas analyzer, and the clear chamber, where the rosette is enclosed. We made a set of three interchangeable chambers of different sizes to measure the rate of CO2 assimilation [A] of 26-, 33- and 40-d-old plants. The dependence of A to light irradiance and to intercellular CO2 concentration was recorded as typical response curves, which validate our device. Measurements were not only consistent in saturating conditions, but accurate CO2 exchange measurements in limiting conditions also reflected important physiological features related to plant ageing. [less ▲]

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See detailA novel high efficiency, low maintenance, hydroponic system for synchronous growth and flowering of Arabidopsis thaliana.
Tocquin, Pierre ULg; Corbesier, Laurent; Havelange, Andrée ULg et al

in BMC Plant Biology (2003), 3(2), 302003

Background: Arabidopsis thaliana is now the model organism for genetic and molecular plant studies, but growing conditions may still impair the significance and reproducibility of the experimental ... [more ▼]

Background: Arabidopsis thaliana is now the model organism for genetic and molecular plant studies, but growing conditions may still impair the significance and reproducibility of the experimental strategies developed. Besides the use of phytotronic cabinets, controlling plant nutrition may be critical and could be achieved in hydroponics. The availability of such a system would also greatly facilitate studies dealing with root development. However, because of its small size and rosette growth habit, Arabidopsis is hardly grown in standard hydroponic devices and the systems described in the last years are still difficult to transpose at a large scale. Our aim was to design and optimize an up-scalable device that would be adaptable to any experimental conditions. Results: An hydroponic system was designed for Arabidopsis, which is based on two units: a seed-holder and a 1-L tank with its cover. The original agar-containing seed-holder allows the plants to grow from sowing to seed set, without transplanting step and with minimal waste. The optimum nitrate supply was determined for vegetative growth, and the flowering response to photoperiod and vernalization was characterized to show the feasibility and reproducibility of experiments extending over the whole life cycle. How this equipment allowed to overcome experimental problems is illustrated by the analysis of developmental effects of nitrate reductase deficiency in nia1nia2 mutants. Conclusion: The hydroponic device described in this paper allows to drive small and large scale cultures of homogeneously growing Arabidopsis plants. Its major advantages are its flexibility, easy handling, fast maintenance and low cost. It should be suitable for many experimental purposes. [less ▲]

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