Academic literature on the topic 'Méristèmes racinaires'
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Journal articles on the topic "Méristèmes racinaires"
Brulfert, Annie. "Le méristème racinaire, modèle pour l'étude du cycle cellulaire et de ses contrôles." Bulletin de la Société Botanique de France. Actualités Botaniques 132, no. 1 (January 1985): 35–47. http://dx.doi.org/10.1080/01811789.1985.10826711.
Full textBenbadis, M. C., M. Delage, and G. Daouse. "Effet stimulant de la poly-D-lysine sur l'entrée en mitose de cellules G2 du méristème racinaire d'Allium sativum." Canadian Journal of Botany 63, no. 1 (January 1, 1985): 155–62. http://dx.doi.org/10.1139/b85-018.
Full textDissertations / Theses on the topic "Méristèmes racinaires"
Hugues, Alice. "Epigenetic regulation of root cell differentiation by the Polycomb Repressive Complex 2 in Arabidopsis thaliana." Electronic Thesis or Diss., Lyon, École normale supérieure, 2024. http://www.theses.fr/2024ENSL0005.
Full textCell differentiation, the process that refers to the transition of stem cells to mature cells, is a morphogenetic process resulting in phenotypic changes at the cellular scale. It relies on a profound remodeling of cells transcriptome. Transcription activation and repression are the result of the intertwined activity of both transcription factors and chromatin-modifying complexes that define local chromatin states by depositing post-translational modifications on histone tails, thereby preventing or facilitating the transcription machinery to bind promoters and other regulatory elements. Polycomb Repressive Complex 2 (PRC2) is a chromatin-modifying complex that catalyses the tri-methylation of lysine 27 of histone 3 (H3K27me3) which deposition is associated with repressive chromatin and transcriptional silencing in eukaryotes. Loss of PRC2 activity deeply impacts developmental processes in plants and metazoans, impairing the orchestration of developmental programs in space and in time, at both cellular and tissular scales.My doctoral project aimed at deciphering the role of PRC2 in regulating transcription during the establishment of cell types during post-embryonic development, using the root of Arabidopsis thaliana as model.By integrating both publicly available and original epigenomic and transcriptomic data at the single cell resolution, I dissected the transcriptional response of PRC2-regulated genes all along the differentiation of several root cell types. These analyses first showed that the transcriptional regulation by PRC2 is for the most part cell type-specific and subsequently that the differential expression of PRC2 target genes is a signature of cell types. Moreover, we found that PRC2-regulated genes are dynamically expressed during cell differentiation and that transcriptional changes occur by waves at key stages in the differentiation of each cell type. The second part of this project seeked to establish a direct causal link between PRC2 activity, the resulting transcriptional regulations and the acquisition of cell identities in A. thaliana primary and lateral roots using a reverse genetics approach. We implemented an inducible gene editing system to knock-out FIE, a gene encoding for a core PRC2 subunit, in a cell type- and developmental stage-specific manner. Using this method, we provide the first evidence of causality between PRC2 activity and its involvement in the homeostasis of root cell differentiation during the post-embryonic development of A. thaliana. Preliminary results showed that FIE knock-out after germination phenocopies classical PRC2 mutants, highlighting the role of PRC2 in both guiding root differentiation and maintaining the indeterminacy and the longitudinal patterning of root meristems to support continuous root growth. Taken together, our results shed new lights into the role of chromatin regulation by PRC2 in the transcriptional control of cell differentiation
Parizot, Boris. "Etude d'un déterminant de l'architecture racinaire chez Arabidopsis thaliana : l'identité des cellules du péricycle associées aux pôles de xylème." Aix-Marseille 2, 2007. http://theses.univ-amu.fr.lama.univ-amu.fr/2007AIX22087.pdf.
Full textLateral root initiation is a major determinant of root architecture. This work characterizes the pericycle cell layer from which the lateral roots emerge in the dicotyledonous plants. Up to now this layer has always been regarded, in accordance with the outer tissue layers, as one uniform concentric layer. This is in contrast with the diarch organization of the internal vascular tissues. Taken together our data from the analysis of marker lines, genetic screen and transcriptome study show that the pericycle is a heterogeneous cell layer with two populations of cells. We propose a model in which the vascular tissues and their associated pericycle are determined early, is dependent upon a common genetic pathway but which can differentiate, at least, independently. We therefore modify the classic vision of the pericycle cells following a bilateral organization and being intimately associated with their adjacent associated vascular tissues
Rebouillat, Julia. "Étude cellulaire et moléculaire du développement racinaire chez le riz (Oryza sativa L. Cv Nipponbare) : criblage et caractérisation d'une collection de lignées d'insertion enhancer trap Gal4-UAS-GFP." Montpellier 2, 2006. http://www.theses.fr/2006MON20063.
Full textRice is one of the world's most important food crops. Increased production is essential to ensure the food security and economic stability of many countries. Crop improvement is therefore essential to achieve an increase in rice production. The root system allows the plant to access mineral and water resources and an accurate knowledge of its development is crucial. In this study, we were interested in root development at the cellular and molecular level. First of all, we revisited the steps in the establishment of the root system, focusing on cell fate at the root apical meristem in rice, comparing it with the well-described process in Arabidopsis thaliana, the model plant for dicotyledons. This comparison highlights the major differences in structure and function between the two model plants, underlining the importance of studying in greater detail the process of establishing the underground structures of rice. Next, we established a collection of Gal4-UAS-GFP enhancer trap lines that express GFP in specific root cells, tissues and organs. These lines expressing various cellular markers can be used for various developmental and physiological studies. In addition, we refined the method of screening these lines. Observation of roots in vivo, using a two-photonic microscope, allows their internal cell structure to be visualised down to 200µm and facilitates the precise location of cellular markers. Finally, we initiated the study of two mutants which i) express GFP in their meristematic zones and ii) show a root and/or shoot phenotype that suggests an anomaly in the functioning of their meristems
Willaume, Magali. "Influences de diverses opérations de taille et de la croissance rythmique sur le développement racinaire de jeunes chênes blancs (Quercus pubescens)." Avignon, 2005. http://www.theses.fr/2005AVIG0316.
Full textTo better understand influence of pruning on roots, the pattern of development of the root system of Quercus pubescens was explored in relation to shoot periodical development and various contrasted defoliation treatments (ablations of mature leaves, cotyledons or young developing leaves). Oak seedlings were grown in rhizotrons for dynamic measurements of root morphological responses, or in pots to compare root growth with dynamics of carbohydrate content in different parts of the root system, and auxin content in apical segments. On control seedlings, we noticed during expansion of the leaves of the second flush a transient decrease in taproot elongation, a concomitant decrease in taproot apical diameter and a stronger decrease in lateral root elongation, showing that root growth in young oak trees is actually sensitive to rhythmic growth. Soluble sugar in apical segments was also reduced during second flush expansion, and increased again after the end of aerial growth. Branching was relatively constant after the end of the first flush development. Starch content in cotyledons decreased regularly. Ablation of source organs (mature leaves or cotyledons) amplified the decrease of root growth concomitant with leaf expansion and caused a large decrease in branching density. A large proportion of lateral roots exhibited delayed emergence. Development of primordia was more affected than initiation. When both cotyledons and mature leaves had been removed, growth decrease was enhanced and density of primordia reduced. Soluble sugar content in apices decreased drastically and starch storage in root basal segment was totally emptied 5 days after defoliation, showing a strong shortage in carbohydrates. Soluble sugar content recovered after the end of aerial growth, suggesting a dense recirculation of sugar in plant. No supplementary recourse to starch content in cotyledons was noticeable. In contrast, continuous ablation of sink organs (young leaves) had no significant effect on the root development pattern and maintained at first elongation and branching characteristics, before gradual and slight decrease in lateral root. Apical sugar content was also maintained and starch storage in basal root segments improved. As important auxin sources have been removed in this treatment, a limitation in auxin could have occurred. However, even if auxin apical contents tended to be reduced, no treatment had a significant effect on auxin content. The parallel between pattern of apical sugar content and root growth pattern, and the strong correlations between hexose content in the root apex and its growth rate support the hypothesis of a major control of growth through carbohydrate availability in the root response to periodic growth and defoliation treatments
Chen, Gwennaëlle. "Rôles de polygalacturonases (PG) dans le développement racinaire, chez Arabidopsis thaliana." Thesis, Amiens, 2018. http://www.theses.fr/2018AMIE0022/document.
Full textPlant cell wall structure is modified to control its stiffness or flexibility according to plant’s requirements. The cell wall is a complex structure, composed of cellulose, hemicelluloses and pectins. Pectin modifications during cellular elongation are not very well characterized. In this context, the aim of this project is to study the roles of two polygalacturonases (PG) in the root development on the model plant A. thaliana. PG are homogalacturonans (HG) degradation enzymes, HG being the major pectic component of the primary cell wall. This degradation would lead to a local parietal relaxation, allowing anisotropic growth of the cells. Our results show that the two studied PG, named PG ROOT APICAL MERISTEM (PG RAM) and PG ROOT (PG R), are expressed in complementary areas of the root, either in the root apical meristem (PG RAM) or in the elongated and differenciated root tissues (PG R). Furthermore, the over-expression of PG R results in longer etiolated hypocotyls and increases root density when compared to wild-type, demonstrating its function in root development and in cell elongation. Finally, we demonstrated that expression of these two PG genes is under the control of PLETHORA (PLT) family transcription factors, by differentially ways
Poulain, Jérôme Matthias. "Étude du rôle de gènes contrôlant le cycle cellulaire au cours du développement racinaire de Cichorium intybus L. : isoolement et caractérisation d'une cycline mitotique de type B de chicorée." Lille 1, 2003. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2003/50376-2003-199-200.pdf.
Full textBettembourg, Mathilde. "Caractérisation de récepteurs à activité kinase impliqués dans la mise en place de l'architecture racinaire chez le riz." Thesis, Montpellier, SupAgro, 2016. http://www.theses.fr/2016NSAM0026.
Full textRoots have two major roles. The first one is to uptake water and nutrients and the second one is to anchor plants into the ground. Identifying the genes responsible for the establishment of tissues and architecture of the root system is essential to improve rice varieties subject to increasingly frequent and numerous abiotic stresses due to climate change. During my PhD, I undertook a functional analysis of the DEFECTIVE IN OUTER CELL LAYER SPECIFICATION (DOCS1) gene which belongs to the Leucine-Rich Repeat Receptor-Like Kinase (LRR-RLK) family. These proteins are composed of two main domains: an extra-cytoplasmic domain containing LRR repeats and a cytoplasmic kinase domain. A mutant of this gene, named c68, carries a nonsense mutation in the kinase domain. The c68 mutant plants show several phenotypes: increased sensitivity to aluminum, reduced number and size of root hairs, and layers of external tissues with exodermis/epidermis mixed identity. The first chapter of the thesis focuses on the joint study of knockout CRISPRs lines of the DOCS1 gene and c68. Our results showed that the c68 and CRISPRs mutants displayed the same phenotypes: sensitivity to aluminum, defects in root hairs and mixed identity of external tissues. These results suggested that in the c68 mutant, either the DOCS1 protein was not functional, or the protein was not translated. Our phenotypic analyses also showed that all mutants exhibited impaired gravity responses at different development stages. At 3 days, a delay of response to gravity was observed during the first hour after gravistimulation. Mutant seedlings also had defects in an auxin transporter localization. At 40 days, we observed that the root cone angle of mutant plants was more open than that of wild-type plants. Two genes associated with auxin and several QTLs have been identified as contributing to this phenotype in rice. In the rest of our study, we therefore tried to identify new QTLs and genes involved in this morphological phenotype by a genome-wide association study in two Indica and Japonica panels. All accessions of the bulu ecotype from Indonesia and three South Asian temperate japonica had a very open root cone angle. Using a mixed model associated with a resampling technique, 55 QTLs were detected. The analysis of the underlying or neighbor (+/- 50kb) genes identified 539 genes, including 6 LRR-RLK, 5 genes related to auxin and 5 genes with a function validated in root development or architecture. A complementary approach by classical genetic mapping is proposed to identify genes involved in the mutation(s) involved in very open root cone angle. Prospective research lines are also presented to determine if the root cone angle phenotype , induced by DOCS1 or by newly identified genes, is linked with disruption of auxin fluxes
Bizet, François. "Division et élongation cellulaire dans l'apex de la racine : diversité de réponses au déficit hydrique." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0258/document.
Full textRegulation of root growth is a crucial capacity of plants for acclimatization to environmental stresses. At cell scale, this regulation is controlled through cell division and cell elongation but respective importance of these processes and interactions between them are still poorly known. Notably, the cell production activity of the root apical meristem (RAM) is often excluded. During this thesis, spatial analyses of growth along the root apex were coupled with temporal analyses of cell trajectories in order to decipher the links between cell division and cell elongation. This required the setup of a system for phenotyping root growth at a high spatiotemporal resolution which was applied to study the growth of roots from an euramerican poplar (Populus deltoides × Populus nigra) in response to different environmental stresses (osmotic stress or mechanical impedance). An important variability of root growth rate between individuals as well as individual cyclic variations of growth along time were observed despite tightly controlled environmental conditions. Use of this variability coupled with quantification of the RAM activity led us to a better understanding of the importance of the cell production rate for sustaining root growth. This work analyses a new spatiotemporal scale of growth variability poorly considered. Widely applicable to others scientific questioning, temporal analyses of cell fate once produced in the RAM is also discussed for non-steady growth conditions