1,721,007 research outputs found
Visualising xylem vessels connections formed one year after grafting with different techniques
No full textGrapevine grafting is an important technique in viticulture and the formation of vascular connections between the scion and rootstock is essential for successful grafting. This study investigates the three-dimensional (3D) structure of the graft interface produced by commonly used techniques, namely, the omega, full cleft, cleft, and Whip and Tongue.
X-ray micro-computed tomography was used to determine anatomy of the graft union based on tissue x-ray density and functional xylem vessels were labelled with the contrast agent. The total volume of the graft interface, the volume of air spaces/necrotic tissues and the distribution of functional xylem vessels was studied.
Functional xylem vessels connect the scion and the rootstock in all grafting types, but in some grafts, this connection is not continuous around the entire circumference of the graft interface. We found that the proportion of air spaces/necrotic tissues relative to the graft interface volume was not affected by grafting type. Omega grafts were found to be more compact, with shorter graft interfaces and as a consequence a smaller absolute volume of air spaces/necrotic tissues at the graft interface.
By combining 3D morphological and functional analysis, this study presents a step forward in addressing the questions facing modern viticulture
Nitrate as a signal in Arabidopsis
No full textThis thesis describes an investigation of nitrate signalling in Arabidopsis thaliana leaf cells. The expression and activity of nitrate transporters and assimilatory enzymes are under complex regulation by mechanisms that are not yet fully understood. Experiments were designed to investigate the relationships between cytosolic ion activity changes and the regulation of nitrate transporters and assimilatory enzymes.Two different approaches were used. Firstly, cytosolic ion activity changes were measured under light-dark transitions, treatment known to affect the regulation of nitrate transporters and assimilatory enzymes. These changes were initially studied using ion-selective microelectrodes. Light-dark transitions were shown to cause changes in cytosolic nitrate activity in mesophyll cells. Dark treatment caused an increase in cytosolic nitrate activity, light treatment a decrease. Plants without functional nitrate reductase (NR) did not show such changes and a higher constant level of cytosolic nitrate activity was observed compared with wild type, suggesting that NR activity has a role in cytosolic nitrate activity changes. These results are consistent with a signalling role for cytosolic nitrate activity in the regulation of nitrate transporters and assimilatory enzymes. The role of NR in influencing cytosolic pH was investigated using pH-selective microelectrodes. The microelectrode measurements were extremely difficult and time consuming so as an alternative pH-indicator dyes were tested but were not distributed in the cytosol of mesophyll cells.The second approach involved the use of nitrate-inducible luciferase reporter plants. A photomultiplier tube/fibre optic cable system was developed and used to quantify luminescence from these plants. A low-light imaging camera was also used. Both systems showed that the reporter plants provided were unsuitable for the study of nitrate-induction. Alternative nitrate-inducible reporter plants were produced, which were shown to be nitrate-inducible and suitable for nitrate-induction studies.The results presented provide supporting evidence for the hypothesis that NR-dependent changes in cytosolic nitrate activity may function as signals in Arabidopsis mesophyll cells.</p
Untargeted metabolomics raw data
No full textSemi-polar compounds were extracted, including primary and secondary metabolites, using automated high-throughput ethanol extraction procedures at the MetaboHUB-Bordeaux Metabolome (https://metabolome.u-bordeaux.fr/) from 35 mg of fresh powder, following previously established protocols (Luna et al., 2020). All samples were randomised and injected alternately with extraction blanks (prepared without plant material and used to rule out potential contaminants detected by untargeted metabolomics), and 13 Quality control samples that were prepared by mixing 10 µL from each sample. Quality control samples were injected every 8 runs and used for the correction of signal drift during the analytical batch, and the calculation of coefficients of variation for each metabolomic feature so only the most robust ones are retained for chemometrics (Broadhurst et al., 2018).
Untargeted analysis was performed on a UHPLC Vanquish (Thermo Fisher Scientific) coupled to a Q-Exactive Plus mass spectrometer (Thermo Fisher Scientific). One µL of sample was injected on a Phenomenex Luna® Omega Polar C18 column (50 x 2.1 mm, 1.6 µm) at 40°C and a gradient of solvent A (milliQ water – 0.1 % formic acid) and solvent B (acetonitrile – 0.1% formic acid) with a flow of 0.5 mL min-1 was used. The gradient elution was set as follows: 0-11.5 min: 1-40% solvent B; 11.5-12.5 min: 40-95% solvent B; 12.5-14 min: 95% solvent B; 14.5-16 min: 1% solvent B.
The mass spectrometry data was acquired in negative polarity at 140.000 FWHM resolution with an automatic gain target at 3e6 and maximum IT of 100 ms. The source conditions were as follow: Spray voltage: 3000 V; Sheath gas: 45 a.u; Auxiliary gas: 15 a.u; Capillary temperature: 320°C; Probe heater temperature: 250°C; S-lens RF level: 100. The experiments were in full scan (mass range: 70-1050 m/z) – data depending MS2 with top three precursors and normalized collision energies of 15, 30, 45 using a dynamic exclusion of 5 s
Targeted metabolomics data
No full textThe chemicals, standards and extraction protocol used as the same as given in Loupit et al. (2022) The analysis protocol was the same as described by Loupit et al. (2020) with some modifications and a different column (Agilent ZORBAX RRHD SB-C18 (2.1 mm x 100 mm, 1.8 μm)).
Loupit G, Prigent S, Franc C, De Revel G, Richard T, Cookson SJ, Fonayet JV. 2020. Polyphenol Profiles of Just Pruned Grapevine Canes from Wild Vitis Accessions and Vitis vinifera Cultivars. Journal of Agricultural and Food Chemistry 68, 13397-13407.
Loupit G, Prigent S, Prodhomme D, Spilmont AS, Hilbert G, Franc C, de Revel G, Ollat N, Valls Fonayet J, Cookson SJ. 2022. Identifying early metabolite markers of successful graft union formation in grapevine Horticultural Research 9, uhab070
Understanding graft union formation and graft incompatibility in grapevine
No full textLe greffage est une technique largement utilisée en horticulture. Cette pratique ancestrale permet, par l'association de deux tissus issus de deux plantes différentes, de former une plante unique avec les avantages agronomiques des génotypes du greffon et du porte-greffe. Le greffage de la vigne est l'un des meilleurs exemples de lutte antiparasitaire durable et respectueuse de l'environnement, car les porte-greffes utilisés offrent naturellement une résistance au Phylloxéra, un insecte s’attaquant principalement aux racines. Cependant, les combinaisons greffon/porte-greffe utilisées aujourd'hui diffèrent dans leur compatibilité de greffe, c'est-à-dire dans leur capacité à former une union de greffe fonctionnelle et durable. Il y a donc beaucoup d'intérêt à utiliser de nouveaux porte-greffes pour adapter la vigne au changement climatique, mais la compatibilité de greffe est une condition préalable essentielle.Mon doctorat a eu pour but d’approfondir notre compréhension des changements moléculaires et métaboliques sous-jacents à la formation de l'union de greffe, et d’identifier des marqueurs précoces d’incompatibilité de greffe chez la vigne. Avant ce travail de thèse, il n'y avait pas eu d'étude approfondie des gènes différentiellement exprimés lors du greffage chez des espèces pérennes, et nous avions que très peu de connaissances sur les changements métaboliques. Au cours de mon travail, nous avons réalisé une étude approfondie de l'expression des gènes pour identifier des gènes différentiellement exprimés en réponse au greffage, et nous avons caractérisé les changements spatio-temporels de plusieurs métabolites secondaires. Cela nous a permis d'identifier des gènes répondant à la blessure et au greffage ainsi que des gènes répondant au greffage lorsque deux espèces de vigne différentes sont greffées ensemble. La caractérisation spatio-temporelle de l'accumulation de métabolites secondaires à l'interface de greffe a montré que le parenchyme endommagé produit des stilbènes et qu’ils s'oligomérisaient avec le temps. De plus, nous avons utilisé des modèles de prédiction pour identifier des marqueurs métaboliques précoces d'une incompatibilité de greffe, en vue de prédire le taux de réussite au greffage.Grafting is a technique widely used in horticulture. This ancestral tool makes it possible, by the combination of two tissues from two different plants, to form a single plant with the agronomical advantages of the scion and the rootstock genotypes. Grapevine grafting is one of the best examples of sustainable and environmentally friendly pest control as the rootstocks used naturally provide resistance to Phylloxera, a root insect pest. However, scion/rootstocks combinations used today differ in their graft compatibility, i.e. differ in their ability to form a functional and long-lasting graft union. There is much interest in using new rootstocks to adapt grapevine to climate change, but high graft compatibility is an essential prerequisite.My Ph.D. thesis aimed to further our understanding of molecular and metabolic changes underlying graft union formation and to identify early markers of poor graft compatibility in grapevine. Prior to this thesis, there had been no comprehensive study of genes differentially expressed during graft union formation in perennial species, and we have little knowledge of metabolite changes occurring during grafting. During my work, we did a comprehensive gene expression study to identify genes differently expressed in response to grafting and we characterised the spatiotemporal changes in secondary metabolite concentrations. This allowed us to identify genes responding to wounding and grafting as well as genes responding to grafting when two different grapevine species are grafted together. The spatiotemporal characterisation of metabolite accumulation at the graft interface showed that damaged parenchyma tissue produces stilbenes and that these compounds oligomerize over time. In addition, we used prediction models to identify early secondary metabolite markers of graft incompatibility, with the view to predict early grafting success
Metabolic responses of early developing sugar beet plant to heat stress
No full textLa betterave sucrière est la deuxième plante en termes de production de sucre avec 19,6% du sucre produit dans le monde entre 2015 et 2016, derrière la canne à sucre. Cultivée dans les zones tempérées comme le nord de la France et la Belgique, elle est sensible au stress thermique modéré. En effet, une augmentation de 1°C de la température moyenne entraîne une perte de rendement de 29%. Dans le cadre du réchauffement climatique et afin de fournir aux agriculteurs des variétés ayant une meilleure résistance à la chaleur, la compréhension des réponses de la betterave sucrière au stress hyperthermique est nécessaire. Pour cela, une étude des réponses physiologiques et métaboliques a été effectuée avec trois hybrides : un hybride de type sucré avec 18% de sucre dans sa racine, un hybride de type lourd avec un meilleur rendement que la moyenne mais avec seulement 17% de sucre dans sa racine, et un hybride dit « résistant » au stress hyperthermique, ayant le meilleur rendement aux champs avec des températures plus élevées. Alors que la photosynthèse nette n’était pas modifiée en condition de stress, une croissance plus rapide de la rosette a été observée aux stades jeunes pour les trois hybrides. Une approche de modélisation suggère qu’une croissance de la rosette plus rapide contrecarre les effets du stress hyperthermique sur la production racinaire. Cette hypothèse est confirmée par le fait que l’hybride le plus performant a la croissance foliaire la plus rapide. Le stress hyperthermique provoque une forte diminution du stockage transitoire du carbone dans les feuilles matures. Dans les feuilles en cours de développement, le stockage transitoire du carbone, dont la moitié sous forme d’amidon, était seulement maintenu chez l’hybride le plus performant. Un calcul intégrant les besoins en carbone de la croissance foliaire suggère que ce maintien contribue significativement au maintien du rendement chez cet hybride. Par ailleurs, un marqueur putatif de la sensibilité au stress hyperthermique a été identifié lors de cette étude. Au final ce travail a permis de mieux comprendre comment la betterave sucrière répond à l’élévation de la température et ainsi proposer de nouvelles stratégies pour l’amélioration de cette espèce.Sugar beet is the second largest sugar-producing crop, with 19.6% of the sugar produced in the world between 2015 and 2016, behind sugarcane. Cultivated in temperate zones like the north of France and Belgium, it is sensitive to moderate thermal stress. Indeed, an increase of 1°C in the average temperature leads to a loss of efficiency of 29%. In the context of global warming and in order to provide farmers with varieties with better resistance to heat, an understanding of sugar beet responses to hyperthermic stress is necessary. For this, a study of physiological and metabolic responses was carried out with three hybrids: a sweet-type hybrid with 18% sugar in the root, a heavy-type hybrid with a better yield than average but with only 17% sugar in the root, and a so-called "resistant" hybrid, which has the best yield at higher temperatures. While net photosynthesis was not altered in stress conditions, more rapid growth of the rosette was observed at the young stages for all three hybrids. A modeling approach suggests that faster rosette growth counteracts the effects of hyperthermic stress on root production. This hypothesis was confirmed by the fact that the best performing hybrid had the fastest shoot growth. Hyperthermic stress caused a significant decrease in transient carbon storage in mature leaves. In developing leaves, transient storage of carbon, half as starch, was only maintained in the best performing hybrid. A calculation incorporating the carbon requirement of foliar growth suggests that this maintenance contributes significantly to the maintenance of yield in this hybrid. In addition, a putative marker of hyperthermic stress sensitivity was identified in this study. In the end, this work provides a better understanding of how sugar beet responds to the rise in temperature, thus proposing new strategies for the improvement of this species
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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