102 research outputs found
Nitrate transport and signalling
No full textTimes Cited: 134 Miller, Anthony/B-5139-2008; ORSEL, Mathilde/C-5435-2009 Miller, Anthony/0000-0003-0572-7607; ORSEL, Mathilde/0000-0002-0837-6796 International Symposium on Nitrogen Nutrition in Plants Jul 27-31, 2007 Lancaster Univ, Lancaster, ENGLAND 146International audiencePhysiological measurements of nitrate (NO3-) uptake by roots have defined two systems of high and low affinity uptake. In Arabidopsis, genes encoding both of these two uptake systems have been identified. Most is known about the high affinity transport system (HATS) and its regulation and yet measurements of soil NO3- show that it is more often available in the low affinity range above 1 mM concentration. Several different regulatory mechanisms have been identified for AtNRT2.1, one of the membrane transporters encoding HATS; these include feedback regulation of expression, a second component protein requirement for membrane targeting and phosphorylation, possibly leading to degradation of the protein. These various changes in the protein may be important for a second function in sensing NO3- availability at the surface of the root. Another transporter protein, AtNRT1.1 also has a role in NO3- sensing that, like AtNRT2.1, is independent of their transport function. From the range of concentrations present in the soil it is proposed that the NO3- -inducible part of HATS functions chiefly as a sensor for root NO3- availability. Two other key NO3- transport steps for efficient nitrogen use by crops, efflux across membranes and vacuolar storage and remobilization, are discussed. Genes encoding vacuolar transporters have been isolated and these are important for manipulating storage pools in crops, but the efflux system is yet to be identified. Consideration is given to how well our molecular and physiological knowledge can be integrated as well to some key questions and opportunities for the future
The Arabidopsis ATNRT2.7 nitrate transporter controls nitrate content in seeds
No full textTimes Cited: 72 Miller, Anthony/B-5139-2008; ORSEL, Mathilde/C-5435-2009; Chardon, Fabien/G-4826-2013 Miller, Anthony/0000-0003-0572-7607; ORSEL, Mathilde/0000-0002-0837-6796; Chardon, Fabien/0000-0001-7909-3884 83International audienceIn higher plants, nitrate is taken up by root cells where Arabidopsis thaliana NITRATE TRANSPORTER2.1 (ATNRT2.1) chiefly acts as the high-affinity nitrate uptake system. Nitrate taken up by the roots can then be translocated from the root to the leaves and the seeds. In this work, the function of the ATNRT2.7 gene, one of the seven members of the NRT2 family in Arabidopsis, was investigated. High expression of the gene was detected in reproductive organs and peaked in dry seeds. beta-Glucuronidase or green fluorescent protein reporter gene expression driven by the ATNRT2.7 promoter confirmed this organ specificity. We assessed the capacity of ATNRT2.7 to transport nitrate in Xenopus laevis oocytes or when it is expressed ectopically in mutant plants deficient in nitrate transport. We measured the impact of an ATNRT2.7 mutation and found no difference from the wild type during vegetative development. By contrast, seed nitrate content was affected by overexpression of ATNRT2.7 or a mutation in the gene. Finally, we showed that this nitrate transporter protein was localized to the vacuolar membrane. Our results demonstrate that ATNRT2.7 plays a specific role in nitrate accumulation in the seed
High quality integrated LiNbO3 acousto-optic platform for visible light spectrum
No full textThe laser's invention, which produced a coherent light source, has accelerated the development of acousto-optic platforms (AlN, GaN, Quartz, LiNbO3) for many practical applications such as beam steering, signal processing, and intensity modulation. The recent integration of on-chip acousto-optic devices with photonic integrated circuits lead to many different acousto-optic devices such as efficient microwave converters, optical isolators, and wavelength scale acousto-optic frequency shifters, which were not realizable before. However, all of these devices target the 1550 nm optical wavelength or mid IR spectrum, and there is no integrated acousto-optic platform for visible wavelengths to the best of our knowledge. This thesis proposes that a LiNbO3 platform can produce a high acousto-optic coupling rate that can be used as a microwave to optical conversion. To have high coupling, we utilized LiNbO3's ultra-high electromechanical coupling for S0 lamb wave mode excitation. We employed LiNbO3's ultra-low optical loss as an interaction enhancement between light and sound for our resonator structures. Our results revealed that intra-band/inter-band optical scattering in LiNbO3 is strongly enhanced by its large piezoelectric, photoelastic, and electro-optic coefficients leading to efficient sideband generation.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2023-05-01The student, Ogulcan Orsel, accepted the attached license on 2021-04-26 at 13:12.The student, Ogulcan Orsel, submitted this Thesis for approval on 2021-04-26 at 13:22.This Thesis was approved for publication on 2021-04-28 at 11:17.DSpace SAF Submission Ingestion Package generated from Vireo submission #16559 on 2021-09-16 at 20:14:19Made available in DSpace on 2021-09-17T04:06:53Z (GMT). No. of bitstreams: 2
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Previous issue date: 2021-04-28Embargo set by: Seth Robbins for item 118704
Lift date: 2023-09-17T04:07:01Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemAuthor requested closed access (OA after 2yrs) in Vireo ETD systemLimite
Power Modelling and Optimisation of a Communication bus for Small Satellite Missions
No full textAerospace EngineeringSpace Engineerin
Towards a better understanding of dormancy in sweet cherry floral buds using molecular and epigenetic approaches
No full textLe réchauffement climatique est déjà une réalité et une hausse des températures de 2 à 4°C est attendue d’ici 2050. Pour les espèces fruitières, un des impacts les plus notables dus au changement climatique a été observé pour la phénologie de la floraison et les dates de maturation des fruits. En effet, la phénologie de la floraison est sous la dépendance directe d’une sortie adéquate de dormance des bourgeons, largement contrôlée par la température. Au cours de mon projet de thèse, des approches physiologiques, moléculaires et transcriptomiques ont été combinées afin d’analyser finement la réponse à la température chez différentes variétés de cerisier ayant des dates de sortie de dormance et de floraison différentes. Les analyses du transcriptome par le biais de RNA-seq ont permis d’obtenir une liste de gènes marqueurs impliqués dans la progression de la dormance et pourront être utilisés comme outil pour l’aide à la décision afin d’estimer le statut de dormance des arbres.Ce qui est particulièrement important pour les producteurs qui ont besoin de connaitre un interval temps précis pour appliquer des produits de levée de dormance. Des quantifications de phytohormones ont révélé l’importance de l’acide abscissique et de ses catabolites dans l’induction et la maintenance de la dormance. En complément de l’étude transcriptomique,une approche épigénétique a été faite sur des bourgeons floraux de cerisier. Nous avons trouvé que la sortie de dormance était associée à certaines marques histones comme la méthylation et l’acétylation des histones. L’impact agronomique de ce projet sera d’apporter une meilleure connaissance des gènes et des mécanismes impliqués dans la dormance dans le but de créer de nouvelles variétés adaptées aux futures conditions climatiques en France et dans plusieurs régions du monde.Plants are sessile organisms and must adapt their physiology to seasonal changes tosubsist over time. Their ability to perceive and respond to changes in temperature is a keydeterminant of their survival. For perennial plants, this is especially important becauseflowering occurs in the next season and reproductive structures can be exposed to hightemperature fluctuations, particularly low winter temperatures. One of the strategies tosurvive under low temperatures is a period of dormancy. In sweet cherry (Prunus avium L.),which is a perennial fruit tree belonging to the Rosaceae family, dormancy is mainly inducedby low temperatures. However, the mean surface temperature of the earth is increasing andthis climatic change may have serious negative consequences on dormancy release,potentially resulting in lower cherry production. Despite the effect of temperature ondormancy and bud break, the molecular events regulating these processes are still poorlyunderstood. We performed transcriptomic analysis on flower buds of different cherry cultivarsdisplaying contrasting flowering times to identify genes involved in dormancy regulation. Atime-course spanning the entire bud development until flowering was performed to explorespecific biological processes. A list of marker genes associated with dormancy progressionwas identified and can be used as a decision-making tool to estimate the dormancy status ofbuds. This is particularly relevant for growers who need to know the optimal timing to applydormancy release products. Phytohormone quantifications have revealed that abscisic acidand its catabolites play an important role in the induction and maintenance of dormancy. Inaddition, we investigated potential epigenetic mechanisms regulating dormancy using ChIPseqand epigenetic drugs. We found that histone deacetylation is involved in bud break aswell as repressive and active histone marks such as H3K27me3 and H3K4me3, respectively.These results provide a source of information to create predictive models, which will bepowerful tools to assist breeding strategies
Towards a better understanding of dormancy in sweet cherry floral buds using molecular and epigenetic approaches
No full textLe réchauffement climatique est déjà une réalité et une hausse des températures de 2 à 4°C est attendue d’ici 2050. Pour les espèces fruitières, un des impacts les plus notables dus au changement climatique a été observé pour la phénologie de la floraison et les dates de maturation des fruits. En effet, la phénologie de la floraison est sous la dépendance directe d’une sortie adéquate de dormance des bourgeons, largement contrôlée par la température. Au cours de mon projet de thèse, des approches physiologiques, moléculaires et transcriptomiques ont été combinées afin d’analyser finement la réponse à la température chez différentes variétés de cerisier ayant des dates de sortie de dormance et de floraison différentes. Les analyses du transcriptome par le biais de RNA-seq ont permis d’obtenir une liste de gènes marqueurs impliqués dans la progression de la dormance et pourront être utilisés comme outil pour l’aide à la décision afin d’estimer le statut de dormance des arbres.Ce qui est particulièrement important pour les producteurs qui ont besoin de connaitre un interval temps précis pour appliquer des produits de levée de dormance. Des quantifications de phytohormones ont révélé l’importance de l’acide abscissique et de ses catabolites dans l’induction et la maintenance de la dormance. En complément de l’étude transcriptomique,une approche épigénétique a été faite sur des bourgeons floraux de cerisier. Nous avons trouvé que la sortie de dormance était associée à certaines marques histones comme la méthylation et l’acétylation des histones. L’impact agronomique de ce projet sera d’apporter une meilleure connaissance des gènes et des mécanismes impliqués dans la dormance dans le but de créer de nouvelles variétés adaptées aux futures conditions climatiques en France et dans plusieurs régions du monde.Plants are sessile organisms and must adapt their physiology to seasonal changes tosubsist over time. Their ability to perceive and respond to changes in temperature is a keydeterminant of their survival. For perennial plants, this is especially important becauseflowering occurs in the next season and reproductive structures can be exposed to hightemperature fluctuations, particularly low winter temperatures. One of the strategies tosurvive under low temperatures is a period of dormancy. In sweet cherry (Prunus avium L.),which is a perennial fruit tree belonging to the Rosaceae family, dormancy is mainly inducedby low temperatures. However, the mean surface temperature of the earth is increasing andthis climatic change may have serious negative consequences on dormancy release,potentially resulting in lower cherry production. Despite the effect of temperature ondormancy and bud break, the molecular events regulating these processes are still poorlyunderstood. We performed transcriptomic analysis on flower buds of different cherry cultivarsdisplaying contrasting flowering times to identify genes involved in dormancy regulation. Atime-course spanning the entire bud development until flowering was performed to explorespecific biological processes. A list of marker genes associated with dormancy progressionwas identified and can be used as a decision-making tool to estimate the dormancy status ofbuds. This is particularly relevant for growers who need to know the optimal timing to applydormancy release products. Phytohormone quantifications have revealed that abscisic acidand its catabolites play an important role in the induction and maintenance of dormancy. Inaddition, we investigated potential epigenetic mechanisms regulating dormancy using ChIPseqand epigenetic drugs. We found that histone deacetylation is involved in bud break aswell as repressive and active histone marks such as H3K27me3 and H3K4me3, respectively.These results provide a source of information to create predictive models, which will bepowerful tools to assist breeding strategies
Leaf nitrogen remobilisation for plant development and grain filling
No full textInternational audienceA major challenge of modern agriculture is to reduce the excessive input of fertilisers and, at the same time, to improve grain quality without affecting yield. One way to achieve this goal is to improve plant nitrogen economy through manipulating nitrogen recycling, and especially nitrogen remobilisation, from senescing plant organs. In this review, the contribution of nitrogen remobilisation efficiency (NRE) to global nitrogen use efficiency (NUE), and tools dedicated to the determination of NRE are described. An overall examination of the physiological, metabolic and genetic aspects of nitrogen remobilisation is presented
Analysis of the NRT2 Nitrate Transporter Family in Arabidopsis. Structure and Gene Expression
No full textAbstract
Nitrate is an essential element for plant growth, both as a primary nutrient in the nitrogen assimilation pathway and as an important signal for plant development. The uptake of nitrate from the soil and its translocation throughout the plant has been the subject of intensive physiological and molecular studies. Using a reverse genetic approach, the AtNRT2.1 gene has been shown to be involved in the inducible component of the high-affinity nitrate transport system in Arabidopsis. The Arabidopsis Genome Initiative has released nearly the whole genome sequence of Arabidopsis, allowing the identification of a small NRT2 multigene family in this species. Thus, we investigated the phylogenetic relationship between NRT2 proteins belonging to several kingdoms and compared the structure of the different members of the Arabidopsis family. We analyzed, by semiquantitative reverse transcriptase-polymerase chain reaction, the expression pattern of each gene depending on plant organ and development or nutritional status, and compared the relative level of each gene by real-time polymerase chain reaction. We also evaluated the significance of each paralog on the basis of the relative levels of gene expression. The results are discussed in relation with distinct roles for the individual members of the AtNRT2 family.</jats:p
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