Tesis sobre el tema "Root meristems"
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Lyndon, Robert Frank. "Growth and development of the root and shoot apical meristems". Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/15238.
Texto completoTalboys, Peter James. "Hormonal regulation of stem cell maintenance in root meristems of Arabidopsis thaliana". Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.574619.
Texto completoPlum, Sara A. "Manipulation of sources and sinks of grasses : growth, photosynthesis and root exudation". Thesis, Bangor University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389504.
Texto completoHugues, 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.
Texto completoCell 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
Rodrigues, Maria Aurineide. "Sinalização no ganho de competência para a conversão de meristemas apicais radiculares de Catasetum fimbriatum em gemas caulinares". Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/41/41132/tde-28012009-101737/.
Texto completoDuring this research work, it was noticed that competence acquisition for the conversion of Catasetum fimbriatum root tips into buds was related to the plant ageing. This process seems to be coupled with the establishment of the determinate root growth and with the cessation in the activity and structural re-organization of the root apical meristem (RAM). Young and non-competent root tips showed a closed RAM architecture, and the ageing process stimulated the establishment of an open organization in the RAM, as indicated by a higher level of differentiation and a predominance of parenchymatic cells in the old root apices. These alterations were concomitant with the modifications on the characteristics and functions of quiescent center (QC). In agreement with these observations, the competence acquisition to the conversion of the MAR into buds was linked to a series of metabolic alterations, which probably play a role in this process. Based on the data obtained, it was observed that the endogenous levels of important components of the cell division progression, such as auxins, cytokinins and the reduced forms of ascorbate and glutathione showed a tendency of decrease during the root ageing. On the other hand, during this same period, the content of some hormones involved in signalling events of stress conditions or cellular differentiation, such as ethylene, abscisic acid and gibberellins exhibited a pattern of increase. The relative concentrations of important second messengers, such as nitric oxide and cytosolic calcium also displayed a marked increased in the RAM region during the ageing. Additionally, it was noticed that the auxin polar transport represents an important positional signal for the maintenance of the RAM characteristics and functions, once treatments that blocked the transport of this hormone promoted the MAR competence acquisition even in young plants, although, the conversion process did not complete while the root tips were maintained attached to the plants. The treatment of young plants with ethylene, on the contrary, caused similar effects; however, besides inducing the competence, this hormone also promoted the RAM conversion into buds via the elevation in the endogenous levels of cytokinins. The treatment of young root tips with different types of cytokinins indicated that iP-type cytokinins (iP and iPR) were more closely associated to the preservation of the root characteristics, while the Z-type cytokinins (Z and ZR) showed a higher importance when the root characteristics were lost. Furthermore, the treatment of young root apices with compounds that cause alterations in the cellular redox status indicated that the oxidative stress stimulated the competence acquisition for the RAM conversion into buds. This same tendency was observed with the application of relatively high concentrations of compounds that induce elevations in the levels of nitric oxide and cytosolic calcium in the tissues. The analyses carried out during the first hours after the isolation of partially competent root apices indicated that the detachment of the root tips from the original plants accelerated the morphological modifications that naturally occur at advanced stages of ageing. During this same period, it was observed a rapid decrease in the endogenous levels of cytokinins (specially of the iP-type), leading to a predominance of the Z-type cytokinins during the first day after the isolation of the explants, which coincided with the alteration of the RAM architecture from the intermediate-open type to the completely open type. After the first day of isolation, the progress in the root apices modifications resulted in the establishment of the shoot meristem, which was accompanied by an elevation in the endogenous levels of cytokinins and ascorbate. Therefore, advanced stages of root ageing, as well the isolation of the partially competent root apices, seem to increase the competence for the RAM conversion into buds via similar morphological and physiological changes in the root apices. These alterations involved the loss of the root characteristics, which possibly resulted from modifications in the control of the QC on the development of the other cells in the RAM. These events in the QC represent a sine qua non condition for the completion of the MAR competence acquisition, which is affected by the intensity of the perturbations on the control of the RAM organization. Therefore, the conversion of root apical meristem of C. fimbriatum into buds probably results from the formation of a new group of cells in the region of the QC of the altered RAM. These cells seem to be competent to respond to different stimulus that would directionate them to a new developmental route that, in this case, consists in the establishment of a shoot meristem.
Costa, Mayra Camargo Andrade. "Desenvolvimento de Setaria viridis com ênfase no estabelecimento do meristema radicular". Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/64/64133/tde-07032019-141238/.
Texto completoSetaria viridis is a very important grass in studies of plant development, due to some characteristics that make it an excellent proposed model organism for monocotyledonous plants with C4 metabolism. To be widely used in studies that aim to understand plant functioning and development, as well as the molecular mechanisms that modulate it, it is essential that aspects of its development be unraveled. In this context, the characterization of the root meristem and structures present in the early stages of germination is also important to understand how the emergence of different root types occurs in grasses. Moreover, to correlate the environmental and endogenous factors involved in the choice of different architectures of root systems in grasses. Furthermore, the characterization of the development of floral structures in Setaria viridis is important, since it brings information that can contribute to the efficiency of methodologies of genetic transformation for the species. The present work characterized morphologically the root development during the initial stages of germination and the floral development of Setaria. In addition, it sought to establish a relationship between the emergences of different types of roots (primary and adventitious) with different light conditions in in vitro cultures
Moreno-Ortega, Beatriz. "Instabilité développementale chez les racines latérales du maïs : une analyse multi-échelle". Thesis, Montpellier, SupAgro, 2016. http://www.theses.fr/2016NSAM0022/document.
Texto completoIn the perspective of a second Green Revolution, aiming, unlike the first one, to enhance yields of crops in a low fertility context, the strategies used by plants for an optimal uptake of soil nutrients are at the core of the problem. To solve it and identify ideal breeds among the genetic diversity of crops, plant root systems, their development and their architecture, are called upon to play the leading role. The variability among secondary roots appears as a crucial feature for the optimality of soil exploration and acquisition of mobile and immobile resources, but this phenomenon remains poorly understood. The work presented in this thesis focuses on the lateral roots of maize (Zea mays L.) and attempts to unravel the processes at the origin of intrinsic variations in lateral root development. It relies notably on the phenotyping of individual lateral roots at an unprecedented scale, tracking the daily growth of thousands of them at a high spatial resolution, in order to characterize precisely the spatio-temporal variations existing both between and within root individuals. Individual growth rate profiles were analyzed with a statistical model that identified three main temporal trends in growth rates leading to the definition of three lateral root classes with contrasted growth rates and growth duration. Differences in lateral root diameter at root emergence (originating at the primordium stage) were likely to condition the followed growth trend but did not seem enough to entirely determine lateral root fate. Lastly, these lateral root classes were randomly distributed along the primary root, suggesting that there is no local inhibition or stimulation between neighbouring lateral roots. In order to explain the origin of the observed differences in growth behaviour, we complemented our study with a multi-scale characterization of groups of lateral roots with contrasted growth at a cellular, anatomical and molecular level. A particular focus is set on the analysis of cell length profiles in lateral root apices for which we introduced a segmentation model to identify developmental zones. Using this method, we evidenced strong modulations in the length of the division and elongation zones that could be closely related to variations in lateral root growth. The regulatory role of auxin on the balance between cellular proliferation and elongation processes is demonstrated through the analysis of mutant lines. Ultimately, variations in lateral root growth are traced back to the allocation of carbon assimilates and the transport capacity of the root, suggesting that a feedback control loop mechanism could play a determinant role in the setting out of contrasted lateral root growth trends
Silva, Thaís Cristina Ribeiro da. "Cellular and molecular mechanisms underlying root sucker formation in Arabidopsis lyrata". Universidade Federal de Viçosa, 2017. http://www.locus.ufv.br/handle/123456789/16347.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico
A organogênese de brotos a partir de raízes (rootsuckers) permite a propagação vegetativa daArabidopsis lyrata, o parente mais próximo daArabidopsis thaliana. Utilizando um sistema in vitro, o presente estudo objetivou compreender melhor a propagação vegetativa nessa espécie modelo A. lyrata, no que se refere ao desenvolvimento morfológico de suckers, à capacidade de propagação vegetativa em diferentes condições de crescimento in vitro e à identificação de genes potencialmente envolvidos na formação do meristema apical dos brotos.O surgimentodos suckers ocorreu após 30 dias, mais freqüentemente na região axilar das raízes laterais. Os cortes transversais das raízes mostraram uma estrutura primária típica diarca e após cerca de 25 dias, pode-se observar o crescimento secundário da raiz, como indicado pela formação do câmbio. Conclui-se que a emergência do sucker assemelha-se à iniciação das raízes laterais a partir do periciclo, tecido que dá origem ao câmbio vascular durante o crescimento secundário. Em relação às condições de crescimento in vitro, a força total no meio MS induziu o maior número de suckers por planta, seguido por alta concentração de sacarose (3%).Exposição à luz e privação de sacarose não são estritamente necessários para a formação de suckers. Nossos dados também revelaram que a auxina promove a formação dos brotos. Máximas de auxina vascular são necessários para desencadear a iniciação da raiz lateral, sugerindo que a formação de suckers promovida por auxina ocorre provavelmente por mecanismos semelhantes. A avaliação de diferentes genes relacionados a meristema apical, demonstram que o gene STM pode ser um marcador para distinguir as células responsáveis pela formação de suckers. Arabidopsis lyrata provou ser um excelente modelo para estudos de organogênese em raíz e posteriores estudos usando esse sistema de reproduçãopara detectar marcadores epigenéticos através das várias gerações de propagação clonal.
Shoot organogenesis from roots (root suckers) allows vegetative propagation of Arabidopsis lyrata, the closest relative of Arabidopsis thaliana, in addition to sexual propagation and is an important trait associated with the root system. Using an in vitro system, we aimed to better understand the vegetative propagation in the model species A. lyrata, in what regards the morphological development of root suckers, the ability of vegetative propagation in different in vitro growth conditions, and identifying genes potentially involved in the formation of the new shoot apical meristem.Root sucker appearanceoccurred after30 days,most frequently in the axils of lateral roots. Root cross-sections showed a typical diarch primary structure and after 25 days, secondary root growth could be observed, as indicated by formation of the cambium. According to our data,root sucker emergence resembles the initiation of lateral roots from the pericycle, the tissue that gives rise to the vascular cambium during secondary growth. Regarding the in vitro growth conditions, full strength of MS induced the highest number of root suckers per plant, followed 3% of sucrose. However, light exposure and sucrose deprivation are not strictly required for sucker formation. Our data also revealed that auxin promotes root suckering. Vascular auxin response maxima are required to trigger lateral root initiation, suggesting that auxin- promoted sucker formation likely occurs by similar mechanisms. The evaluation of different shoot apical meristem related genes, suggests that the STM gene can be a potential marker to identify cells responsible in driving sucker formation. Arabidopsis lyrata proved to be an excellent model for further studies using root suckers, for example to study epigenetic marks throughout generations of clonal propagation.
Truskina, Jekaterina. "The role of auxin in cell differentiation in meristems". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEN033/document.
Texto completoAuxin regulates plant growth and development through the transcription factors of the AUXIN RESPONSE FACTOR (ARF) gene family. Most notably in Arabidopsis thaliana ARF5, 6, 7, 8 and 19 activate expression of target genes in response to auxin. These five ARF activators control both variable and overlapping processes during plant development including regulation of growth at the root and the shoot apical meristems, lateral root and axillary shoot formation. Each of the five ARF activators shows unique tissue-specific expression patterns in the root and the shoot associated with their distinct functions. This tissue-specific expression is likely derived from the differences in the control of ARF activator transcription. In this study the upstream regulators of ARF5, 6, 7, 8 and 19 transcription were identified. This was achieved by utilizing a high-throughput yeast one-hybrid (Y1H) method. The transient protoplast assay revealed that each ARF activator is controlled by specific transcriptional regulators and that the majority of these regulators are repressors of ARF transcription in planta. Mutants of the regulatory transcription factors were utilized to additionally investigate the interactions in planta. These mutants display auxin-related developmental phenotypes in the root and the shoot including alternations in growth kinetics, emergence of lateral organs, responses to auxin and altered expression of ARF activators. Furthermore, this study additionally focuses on cross-talk between the auxin and cytokinin signaling pathways and its role in root and shoot development. One of the interactions identified in the Y1H screen is a repression of ARF7 by CRF10, a member of the Cytokinin Response Factors gene family. The importance of this interaction in maintaining architecture of the root apical meristem, in leaf senescence and in the phototropic response to blue light in hypocotyls is studied
Chen, Gwennaëlle. "Rôles de polygalacturonases (PG) dans le développement racinaire, chez Arabidopsis thaliana". Thesis, Amiens, 2018. http://www.theses.fr/2018AMIE0022/document.
Texto completoPlant 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
Rea, Robert W. "The co-ordination of cell division and cell expansion in the root meristem of Arabidopsis thaliana". Thesis, University of York, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273897.
Texto completoBroad, Ronan Charles. "Investigating aberrant cell separation in sloughy, an Arabidopsis thaliana mutant allelic to schizoriza". Thesis, University of Canterbury. Biological Sciences, 2014. http://hdl.handle.net/10092/10278.
Texto completoKidd, A. D. "Studies on DNA replication and the cell cycle in the root meristem of fifteen monocotyledonous angiosperms of heterogeneous DNA C values". Thesis, Bucks New University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376419.
Texto completoCouzigou, Jean-malo. "Characterization of MtNOOT and PsCOCH genes in Medicago truncatula and Pisum sativum : two versatile regulators of plant development recruited for symbiotic nodule identity". Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112354.
Texto completoLegume plants are able to house intracellularly soil bacteria collectively called rhizobia. This symbiotic process takes place in a new organ generally formed on the host roots, the nodule. This interaction allows atmospheric nitrogen fixation to the benefit of the plant by using the bacterial nitrogenase activity. Despite an exhaustive description of molecular determinants of this interaction allowing partners recognition, intracellular accommodation and early nodule organogenesis, less is known about cell lineage and identity of the nodule morphogenetic pathway which is thought to represent a recent acquisition during Angiosperms evolution. Nodules from model legumes such as Medicago truncatula or Pisum sativum are described as indeterminate because of the persistence of a distal meristem. The noot (nodule-root) and coch (coch) mutants, in M. truncatula and P. sativum respectively, develop ectopic roots from the nodule vasculature, suggesting that roots and symbiotic nodules are more closely related than previously admitted based on their anatomical comparison. Moreover, the meristematic activity is strongly modified in noot and coch nodules that harbor numerous and enlarged lobes. We showed that NOOT and COCH are orthologs to AtBLADE-ON-PETIOLE1 and 2 redundant transcriptional activators that represent key regulators of versatile plant developmental processes in Arabidopsis thaliana. Because of the conservation of biological functions controlled by NOOT, BOPs and COCH proteins, in particular the regulation of leaf and floral morphologies, abscission zones formation and inflorescence architecture, we proposed that such functions are inherited from a NBCLs (NOOT BOP COCH LIKE) ancestral gene. Our studies of hormonal and genetic determinants of the root meristem in noot and wild-type nodules as well as the characterization of nodule-to-root homeosis have highlighted important parallels between nodule peripheral tissues and roots. We thus propose a model of nodule vascular unit maintenance by the NOOT-dependent repression of a co-opted root morphogenetic program
Bettembourg, 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.
Texto completoRoots 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.
Texto completoRegulation 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
Goswami, Rituparna. "Characterization of the nuclear envelope mechano- transduction in Arabidopsis : from supracellular stress to chromatin remodeling". Thesis, Strasbourg, 2020. http://www.theses.fr/2020STRAJ102.
Texto completoPlant cells sense and respond to external mechanical stimuli such as touch or wind, and to internal mechanical stimuli, such as turgor pressure and cell wall tension. In this study I have demonstrated that the nuclear shape and mechanics are impacted upon hyperosmotic stress in a reversible manner and are correlated with gene expression. To identify the molecular bases of this response, we have investigated different mutants. First the GIP proteins are at the nexus between cytoskeleton, nuclear envelope, and chromatin. We found that the gip1gip2 mutant defects exhibits a constitutive hyperosmotic nuclear response and is already primed to resist hyperosmotic stress. As a more exploratory work, I also analysed the contribution of the nucleoskeleton (crwn1 mutant) and cell wall (eli1 mutant) on nucleus behaviour in response to hyperosmotic stress. Our study opens the path to nuclear mechanotransduction in plants, while also offering several prospects for future research in this area
Benešová, Šárka. "Vývojová terminace aktivity apikálního meristému kořene". Master's thesis, 2016. http://www.nusl.cz/ntk/nusl-351460.
Texto completoBIANCUCCI, MARCO. "Proline Affects Root Meristem Size In Arabidopsis thaliana". Doctoral thesis, 2016. http://hdl.handle.net/11573/889348.
Texto completoThe Arabidopsis thaliana root growt relies on the activity of the root meristematic zone . The size of root meristem is regulated by the plant hormones auxin, cytokinin and gibberellin, which control a short regulatory circuit converging on the gene SHY2. By regulating SHY2, plant hormones control the ratio between cell division and cell differentiation. In a previus work we reported that root elongation in Arabidopsis is promoted by micromolar concentrations of exogenous proline. In order to verify whether a proline-deficient mutant is hampered in root growth, we analyzed the length, relative to wild type, of roots from the proline-deficient mutant p5cs1 p5cs2/P5CS2. Our analyses display that the p5cs1 p5cs2/P5CS2 mutant is characterized by shorter roots, and smaller meristems than wild type. These preliminary data suggest that proline can modulate root meristem size and, in turn, root growth. To evaluate this hypothesis we used a combination of genetic, pharmacological and molecular analyses, and showed that proline specifically affects root growth by modulating the size of the root meristem. The effects of proline on meristem size are parallel to, and independent from, hormonal pathways, and do not involve the expression of genes controlling cell differentiation at the transition zone (SHY2). On the contrary, proline appears to control cell division in early stages of postembryonic root development, as shown by the expression of the G2/M-specific CYCLINB1;1 gene and the G1/S-specific CYCLIND3;1 gene The overall data suggest that proline can modulate the size of root meristematic zone in Arabidopsis likely controlling cell division and, in turn, the ratio between cell division and cell differentiation.
Valdes, Manuel. "Cell Fate Specification and the Regulation of RNA-dependent DNA Methylation in the Arabidopsis Root Meristem". Diss., 2016. http://hdl.handle.net/10161/12266.
Texto completoThe Arabidopsis root apical meristem (RAM) is a complex tissue capable of generating all the cell types that ultimately make up the root. The work presented in this thesis takes advantage of the versatility of high-throughput sequencing to address two independent questions about the root meristem. Although a lot of information is known regarding the cell fate decisions that occur at the RAM, cortex specification and differentiation remain poorly understood. In the first part of this thesis, I used an ethylmethanesulfonate (EMS) mutagenized marker line to perform a forward genetics screen. The goal of this screen was to identify novel genes involved in the specification and differentiation of the cortex tissue. Mapping analysis from the results obtained in this screen revealed a new allele of BRASSINOSTEROID4 with abnormal marker expression in the cortex tissue. Although this allele proved to be non-cortex specific, this project highlights new technology that allows mapping of EMS-generated mutations without the need to map-cross or back-cross. In the second part of this thesis, using fluorescence activated cell sorting (FACS) coupled with high throughput sequencing, my collaborators and I generated single-base resolution whole genome DNA methylomes, mRNA transcriptomes, and smallRNA transcriptomes for six different populations of cell types in the Arabidopsis root meristem. We were able to discover that the columella is hypermethylated in the CHH context within transposable elements. This hypermethylation is accompanied by upregulation of the RNA-dependent DNA methylation pathway (RdDM), including higher levels of 24-nt silencing RNAs (siRNAs). In summary, our studies demonstrate the versatility of high-throughput sequencing as a method for identifying single mutations or to perform complex comparative genomic analyses.
Dissertation
Eyles, Rodney Peter. "microRNA involvement in root organ formation and function in Medicago truncatula". Phd thesis, 2014. http://hdl.handle.net/1885/101496.
Texto completoZhu, Jian Hua y 朱建華. "Studies on mitosis, karyotype and ultrastructure of root tip meristem of keteleeria davidiana var formosana and amentotaxus formosana". Thesis, 1995. http://ndltd.ncl.edu.tw/handle/05228581673155718297.
Texto completoPitchay, Dharmalingam S. "Impact of 11 elemental nutrient deficiencies on shoot and root growth, and foliar analysis standards of 13 ornamental taxa with emphasis on Ca and B control of root apical meristem development". 2002. http://www.lib.ncsu.edu/theses/available/etd-09162002-154007/unrestricted/etd.pdf.
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