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Tom Beeckman - One of the best experts on this subject based on the ideXlab platform.
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Lateral Root formation and nutrients: nitrogen in the spotlight.
Plant physiology, 2021Co-Authors: Pierre-mathieu Pélissier, Hans Motte, Tom BeeckmanAbstract:Lateral Roots are important to forage for nutrients due to their ability to increase the uptake area of a Root system. Hence, it comes as no surprise that Lateral Root formation is affected by nutrients or nutrient starvation, and as such contributes to the Root system plasticity. Understanding the molecular mechanisms regulating Root adaptation dynamics towards nutrient availability is useful to optimize plant nutrient use efficiency. There is at present a profound, though still evolving, knowledge on Lateral Root pathways. Here, we aimed to review the intersection with nutrient signaling pathways to give an update on the regulation of Lateral Root development by nutrients, with a particular focus on nitrogen. Remarkably, it is for most nutrients not clear how Lateral Root formation is controlled. Only for nitrogen, one of the most dominant nutrients in the control of Lateral Root formation, the crosstalk with multiple key signals determining Lateral Root development is clearly shown. In this update, we first present a general overview of the current knowledge of how nutrients affect Lateral Root formation, followed by a deeper discussion on how nitrogen signaling pathways act on different Lateral Root-mediating mechanisms for which multiple recent studies yield insights.
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Peptide-receptor signaling controls Lateral Root development
Plant physiology, 2019Co-Authors: Joris Jourquin, Hidehiro Fukaki, Tom BeeckmanAbstract:Lateral Root development progresses through different steps with, the peptides and receptors involved in each of these steps triggering downstream mechanisms upon peptide perception.
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Dynamic control of Lateral Root positioning.
Current opinion in plant biology, 2016Co-Authors: Barbara K. Möller, Wei Xuan, Tom BeeckmanAbstract:In dicot Root systems, Lateral Roots are in general regularly spaced along the longitudinal axis of the primary Root to facilitate water and nutrient uptake. Recently, recurrent programmed cell death in the Root cap of the growing Root has been implicated in Lateral Root spacing. The Root cap contains an auxin source that modulates Lateral Root patterning. Periodic release of auxin by dying Root cap cells seems to trigger Lateral Root specification at regular intervals. However, it is currently unclear through which molecular mechanisms auxin restricts Lateral Root specification to specific cells along the longitudinal and radial axes of the Root, or how environmental signals impact this process.
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RALFL34 regulates formative cell divisions in Arabidopsis pericycle during Lateral Root initiation
Journal of experimental botany, 2016Co-Authors: Evan Murphy, Tatsuaki Goh, Lisa Van Den Broeck, Zhefeng Lin, Priya Ramakrishna, Brigitte Van De Cotte, Allison Gaudinier, Daniel Slane, Tom BeeckmanAbstract:In plants, many signalling molecules, such as phytohormones, miRNAs, transcription factors, and small signalling peptides, drive growth and development. However, very few small signalling peptides have been shown to be necessary for Lateral Root development. Here, we describe the role of the peptide RALFL34 during early events in Lateral Root development, and demonstrate its specific importance in orchestrating formative cell divisions in the pericycle. Our results further suggest that this small signalling peptide acts on the transcriptional cascade leading to a new Lateral Root upstream of GATA23, an important player in Lateral Root formation. In addition, we describe a role for ETHYLENE RESPONSE FACTORs (ERFs) in regulating RALFL34 expression. Taken together, we put forward RALFL34 as a new, important player in Lateral Root initiation.
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Lateral Root Inducible System in Arabidopsis and Maize.
Journal of visualized experiments : JoVE, 2016Co-Authors: Hanne Crombez, Tom Beeckman, Hans Motte, Ianto Roberts, Nick Vangheluwe, Leentje Jansen, Boris ParizotAbstract:Lateral Root development contributes significantly to the Root system, and hence is crucial for plant growth. The study of Lateral Root initiation is however tedious, because it occurs only in a few cells inside the Root and in an unpredictable manner. To circumvent this problem, a Lateral Root Inducible System (LRIS) has been developed. By treating seedlings consecutively with an auxin transport inhibitor and a synthetic auxin, highly controlled Lateral Root initiation occurs synchronously in the primary Root, allowing abundant sampling of a desired developmental stage. The LRIS has first been developed for Arabidopsis thaliana, but can be applied to other plants as well. Accordingly, it has been adapted for use in maize (Zea mays). A detailed overview of the different steps of the LRIS in both plants is given. The combination of this system with comparative transcriptomics made it possible to identify functional homologs of Arabidopsis Lateral Root initiation genes in other species as illustrated here for the CYCLIN B1;1 (CYCB1;1) cell cycle gene in maize. Finally, the principles that need to be taken into account when an LRIS is developed for other plant species are discussed.
Laurent Laplaze - One of the best experts on this subject based on the ideXlab platform.
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Quiescent center initiation in the Arabidopsis Lateral Root primordia is dependent on the SCARECROW transcription factor
Development (Cambridge England), 2016Co-Authors: Tatsuaki Goh, Darren M. Wells, Laurent Laplaze, Dolf Weijers, Hidehiro Fukaki, Kamal Swarup, Koichi Toyokura, Mayuko Yamamoto, Tetsuro Mimura, Malcolm J BennettAbstract:Lateral Root formation is an important determinant of Root system architecture. In Arabidopsis, Lateral Roots originate from pericycle cells, which undergo a program of morphogenesis to generate a new Lateral Root meristem. Despite its importance for Root meristem organization, the onset of quiescent center (QC) formation during Lateral Root morphogenesis remains unclear. Here, we used live 3D confocal imaging to monitor cell organization and identity acquisition during Lateral Root development. Our dynamic observations revealed an early morphogenesis phase and a late meristem formation phase as proposed in the bi-phasic growth model. Establishment of Lateral Root QCs coincided with this developmental phase transition. QC precursor cells originated from the outer layer of stage II Lateral Root primordia, within which the SCARECROW (SCR) transcription factor was specifically expressed. Disrupting SCR function abolished periclinal divisions in this Lateral Root primordia cell layer and perturbed the formation of QC precursor cells. We conclude that de novo QC establishment in Lateral Root primordia operates via SCR-mediated formative cell division and coincides with the developmental phase transition.
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Lateral Root development in Arabidopsis: fifty shades of auxin
Trends in plant science, 2013Co-Authors: Julien Lavenus, Mikael Lucas, Tom Beeckman, Malcolm J Bennett, Ianto Roberts, Tatsuaki Goh, Soazig Guyomarc'h, Ive De Smet, Hidehiro Fukaki, Laurent LaplazeAbstract:The developmental plasticity of the Root system represents a key adaptive trait enabling plants to cope with abiotic stresses such as drought and is therefore important in the current context of global changes. Root branching through Lateral Root formation is an important component of the adaptability of the Root system to its environment. Our understanding of the mechanisms controlling Lateral Root development has progressed tremendously in recent years through research in the model plant Arabidopsis thaliana (Arabidopsis). These studies have revealed that the phytohormone auxin acts as a common integrator to many endogenous and environmental signals regulating Lateral Root formation. Here, we review what has been learnt about the myriad roles of auxin during Lateral Root formation in Arabidopsis.
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Arabidopsis Lateral Root development: an emerging story.
Trends in Plant Science, 2009Co-Authors: Benjamin Peret, Eva Benkova, Ranjan Swarup, Ilda Casimiro, Tom Beeckman, Laurent Laplaze, Bert De Rybel, Malcolm J BennettAbstract:Lateral Root formation is a major determinant of Root systems architecture. The degree of Root branching impacts the efficiency of water uptake, acquisition of nutrients and anchorage by plants. Understanding the regulation of Lateral Root development is therefore of vital agronomic importance. The molecular and cellular basis of Lateral Root formation has been most extensively studied in the plant model Arabidopsis thaliana (Arabidopsis). Significant progress has recently been made in identifying many new Arabidopsis genes that regulate Lateral Root initiation, patterning and emergence processes. We review how these studies have revealed that the plant hormone auxin represents a common signal that integrates these distinct yet interconnected developmental processes.
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auxin fluxes in the Root apex co regulate gravitropism and Lateral Root initiation
Journal of Experimental Botany, 2008Co-Authors: Christophe Godin, Mikael Lucas, Christian Jayallemand, Laurent LaplazeAbstract:Root architecture plays an important role in water and nutrient acquisition and in the ability of the plant to adapt to the soil. Lateral Root development is the main determinant of the shape of the Root system and is controlled by external factors such as nutrient concentration. Here it is shown that Lateral Root initiation and Root gravitropism, two processes that are regulated by auxin, are co-regulated in Arabidopsis. A mathematical model was generated that can predict the effects of gravistimulations on Lateral Root initiation density and suggests that Lateral Root initiation is controlled by an inhibitory fields mechanism. Moreover, gene transactivation experiments suggest a mechanism involving a single auxin transport route for both responses. Finally, co-regulation may offer a selective advantage by optimizing soil exploration as supported by a simple quantitative analysis.
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Cytokinins Act Directly on Lateral Root Founder Cells to Inhibit Root Initiation
The Plant cell, 2007Co-Authors: Laurent Laplaze, Eva Benkova, Ranjan Swarup, Ilda Casimiro, Steffen Vanneste, Boris Parizot, Lies Maes, Dolf Weijers, Vanessa Calvo, Maria Begoña Herrera-rodriguezAbstract:In Arabidopsis thaliana, Lateral Roots are formed from Root pericycle cells adjacent to the xylem poles. Lateral Root development is regulated antagonistically by the plant hormones auxin and cytokinin. While a great deal is known about how auxin promotes Lateral Root development, the mechanism of cytokinin repression is still unclear. Elevating cytokinin levels was observed to disrupt Lateral Root initiation and the regular pattern of divisions that characterizes Lateral Root development in Arabidopsis. To identify the stage of Lateral Root development that is sensitive to cytokinins, we targeted the expression of the Agrobacterium tumefaciens cytokinin biosynthesis enzyme isopentenyltransferase to either xylem-pole pericycle cells or young Lateral Root primordia using GAL4-GFP enhancer trap lines. Transactivation experiments revealed that xylem-pole pericycle cells are sensitive to cytokinins, whereas young Lateral Root primordia are not. This effect is physiologically significant because transactivation of the Arabidopsis cytokinin degrading enzyme cytokinin oxidase 1 in Lateral Root founder cells results in increased Lateral Root formation. We observed that cytokinins perturb the expression of PIN genes in Lateral Root founder cells and prevent the formation of an auxin gradient that is required to pattern Lateral Root primordia.
Ilda Casimiro - One of the best experts on this subject based on the ideXlab platform.
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The Emerging Role of Reactive Oxygen Species Signaling during Lateral Root Development
Plant physiology, 2014Co-Authors: Concepción Manzano, Pedro J. Casero, Ilda Casimiro, Tom Beeckman, Bert De Rybel, Mercedes Pallero-baena, Beata Orman-ligeza, Gert Van Isterdael, Xavier Draye, Juan Carlos Del PozoAbstract:Overall Root architecture is the combined result of primary and Lateral Root growth and is influenced by both intrinsic genetic programs and external signals. One of the main questions for Root biologists is how plants control the number of Lateral Root primordia and their emergence through the main Root. We recently identified S-phase kinase-associated protein2 (SKP2B) as a new early marker for Lateral Root development. Here, we took advantage of its specific expression pattern in Arabidopsis (Arabidopsis thaliana) in a cell-sorting and transcriptomic approach to generate a Lateral Root-specific cell sorting SKP2B data set that represents the endogenous genetic developmental program. We first validated this data set by showing that many of the identified genes have a function during Root growth or Lateral Root development. Importantly, genes encoding peroxidases were highly represented in our data set. Thus, we next focused on this class of enzymes and showed, using genetic and chemical inhibitor studies, that peroxidase activity and reactive oxygen species signaling are specifically required during Lateral Root emergence but, intriguingly, not for primordium specification itself.
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auxin regulates aquaporin function to facilitate Lateral Root emergence
Nature Cell Biology, 2012Co-Authors: Benjamin Peret, Olivier Postaire, Olivier Da Ines, Ilda Casimiro, Mikael Lucas, Darren M. Wells, Leah R Band, Jin Zhao, Guowei Li, Laure LazzeriniAbstract:Bennett and colleagues find that auxin modulates water uptake in Arabidopsis Roots by negatively regulating the expression of water channel aquaporins to allow Lateral Root emergence. The functional importance of aquaporins is supported by a mathematical model that shows delayed Lateral Root emergence when aquaporin levels are perturbed, as well as by the effects observed after aquaporin overexpression or mutation.
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Auxin regulates aquaporin function to facilitate Lateral Root emergence.
Nature Cell Biology, 2012Co-Authors: Ute Voß, Benjamin Peret, Olivier Postaire, Olivier Da Ines, Ilda Casimiro, Mikael Lucas, Leah R Band, Jin Zhao, Doan-trung Luu, Darren M. WellsAbstract:Aquaporins are membrane channels that facilitate water movement across cell membranes. In plants, aquaporins contribute to water relations. Here, we establish a new link between aquaporin-dependent tissue hydraulics and auxin-regulated Root development in Arabidopsis thaliana. We report that most aquaporin genes are repressed during Lateral Root formation and by exogenous auxin treatment. Auxin reduces Root hydraulic conductivity both at the cell and whole-organ levels. The highly expressed aquaporin PIP2;1 is progressively excluded from the site of the auxin response maximum in Lateral Root primordia (LRP) whilst being maintained at their base and underlying vascular tissues. Modelling predicts that the positive and negative perturbations of PIP2;1 expression alter water flow into LRP, thereby slowing Lateral Root emergence (LRE). Consistent with this mechanism, pip2;1 mutants and PIP2;1-overexpressing lines exhibit delayed LRE. We conclude that auxin promotes LRE by regulating the spatial and temporal distribution of aquaporin-dependent Root tissue water transport.
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Analyzing Lateral Root development: how to move forward.
The Plant cell, 2012Co-Authors: Ive De Smet, Ilda Casimiro, Boris Parizot, Marta Laskowski, Frank Hochholdinger, Philip J White, A Glyn Bengough, Renze Heidstra, Lionel Dupuy, Marc LepetitAbstract:Roots are important to plants for a wide variety of processes, including nutrient and water uptake, anchoring and mechanical support, storage functions, and as the major interface between the plant and various biotic and abiotic factors in the soil environment. Therefore, understanding the development and architecture of Roots holds potential for the manipulation of Root traits to improve the productivity and sustainability of agricultural systems and to better understand and manage natural ecosystems. While Lateral Root development is a traceable process along the primary Root and different stages can be found along this longitudinal axis of time and development, Root system architecture is complex and difficult to quantify. Here, we comment on assays to describe Lateral Root phenotypes and propose ways to move forward regarding the description of Root system architecture, also considering crops and the environment.
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Arabidopsis Lateral Root development: an emerging story.
Trends in Plant Science, 2009Co-Authors: Benjamin Peret, Eva Benkova, Ranjan Swarup, Ilda Casimiro, Tom Beeckman, Laurent Laplaze, Bert De Rybel, Malcolm J BennettAbstract:Lateral Root formation is a major determinant of Root systems architecture. The degree of Root branching impacts the efficiency of water uptake, acquisition of nutrients and anchorage by plants. Understanding the regulation of Lateral Root development is therefore of vital agronomic importance. The molecular and cellular basis of Lateral Root formation has been most extensively studied in the plant model Arabidopsis thaliana (Arabidopsis). Significant progress has recently been made in identifying many new Arabidopsis genes that regulate Lateral Root initiation, patterning and emergence processes. We review how these studies have revealed that the plant hormone auxin represents a common signal that integrates these distinct yet interconnected developmental processes.
Ive De Smet - One of the best experts on this subject based on the ideXlab platform.
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Lateral Root development in Arabidopsis: fifty shades of auxin
Trends in plant science, 2013Co-Authors: Julien Lavenus, Mikael Lucas, Tom Beeckman, Malcolm J Bennett, Ianto Roberts, Tatsuaki Goh, Soazig Guyomarc'h, Ive De Smet, Hidehiro Fukaki, Laurent LaplazeAbstract:The developmental plasticity of the Root system represents a key adaptive trait enabling plants to cope with abiotic stresses such as drought and is therefore important in the current context of global changes. Root branching through Lateral Root formation is an important component of the adaptability of the Root system to its environment. Our understanding of the mechanisms controlling Lateral Root development has progressed tremendously in recent years through research in the model plant Arabidopsis thaliana (Arabidopsis). These studies have revealed that the phytohormone auxin acts as a common integrator to many endogenous and environmental signals regulating Lateral Root formation. Here, we review what has been learnt about the myriad roles of auxin during Lateral Root formation in Arabidopsis.
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Analyzing Lateral Root development: how to move forward.
The Plant cell, 2012Co-Authors: Ive De Smet, Ilda Casimiro, Boris Parizot, Marta Laskowski, Frank Hochholdinger, Philip J White, A Glyn Bengough, Renze Heidstra, Lionel Dupuy, Marc LepetitAbstract:Roots are important to plants for a wide variety of processes, including nutrient and water uptake, anchoring and mechanical support, storage functions, and as the major interface between the plant and various biotic and abiotic factors in the soil environment. Therefore, understanding the development and architecture of Roots holds potential for the manipulation of Root traits to improve the productivity and sustainability of agricultural systems and to better understand and manage natural ecosystems. While Lateral Root development is a traceable process along the primary Root and different stages can be found along this longitudinal axis of time and development, Root system architecture is complex and difficult to quantify. Here, we comment on assays to describe Lateral Root phenotypes and propose ways to move forward regarding the description of Root system architecture, also considering crops and the environment.
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Lateral Root initiation: one step at a time
The New phytologist, 2011Co-Authors: Ive De SmetAbstract:Plant growth relies heavily on a Root system that is hidden belowground, which develops post-embryonically through the formation of Lateral Roots. The de novo formation of Lateral Root organs requires tightly coordinated asymmetric cell division of a limited number of pericycle cells located at the xylem pole. This typically involves the formation of founder cells, followed by a number of cellular changes until the cells divide and give rise to two unequally sized daughter cells. Over the past few years, our knowledge of the regulatory mechanisms behind Lateral Root initiation has increased dramatically. Here, I will summarize these recent advances, focusing on the prominent role of auxin and cell cycle activity, and elaborating on the three key steps of pericycle cell priming, founder cell establishment and asymmetric cell division. Taken together, recent findings suggest a tentative model in which successive auxin response modules are crucial for Lateral Root initiation, and additional factors provide more layers of control.
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The auxin influx carrier LAX3 promotes Lateral Root emergence.
Nature Cell Biology, 2008Co-Authors: Kamal Swarup, Eva Benkova, Ranjan Swarup, Benjamin Peret, Ilda Casimiro, Ive De Smet, Yaodong Yang, Geraint Parry, Erik Nielsen, Steffen VannesteAbstract:Lateral Roots originate deep within the parental Root from a small number of founder cells at the periphery of vascular tissues and must emerge through intervening layers of tissues. We describe how the hormone auxin, which originates from the developing Lateral Root, acts as a local inductive signal which re-programmes adjacent cells. Auxin induces the expression of a previously uncharacterized auxin influx carrier LAX3 in cortical and epidermal cells directly overlaying new primordia. Increased LAX3 activity reinforces the auxin-dependent induction of a selection of cell-wall-remodelling enzymes, which are likely to promote cell separation in advance of developing Lateral Root primordia.
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Auxin-dependent regulation of Lateral Root positioning in the basal meristem of Arabidopsis.
Development (Cambridge England), 2007Co-Authors: Ive De Smet, Ranjan Swarup, Ilda Casimiro, Laurent Laplaze, Bert De Rybel, Steffen Vanneste, Dominique Audenaert, Takuya Tetsumura, Nicolas Frei Dit Frey, Mirande NaudtsAbstract:In plants, the developmental mechanisms that regulate the positioning of Lateral organs along the primary Root are currently unknown. We present evidence on how Lateral Root initiation is controlled in a spatiotemporal manner in the model plant Arabidopsis thaliana. First, Lateral Roots are spaced along the main axis in a regular left-right alternating pattern that correlates with gravity-induced waving and depends on AUX1, an auxin influx carrier essential for gravitropic response. Second, we found evidence that the priming of pericycle cells for Lateral Root initiation might take place in the basal meristem, correlating with elevated auxin sensitivity in this part of the Root. This local auxin responsiveness oscillates with peaks of expression at regular intervals of 15 hours. Each peak in the auxin-reporter maximum correlates with the formation of a consecutive Lateral Root. Third, auxin signaling in the basal meristem triggers pericycle cells for Lateral Root initiation prior to the action of INDOLE-3-ACETIC ACID14 (SOLITARY Root).
Pedro J. Casero - One of the best experts on this subject based on the ideXlab platform.
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The Emerging Role of Reactive Oxygen Species Signaling during Lateral Root Development
Plant physiology, 2014Co-Authors: Concepción Manzano, Pedro J. Casero, Ilda Casimiro, Tom Beeckman, Bert De Rybel, Mercedes Pallero-baena, Beata Orman-ligeza, Gert Van Isterdael, Xavier Draye, Juan Carlos Del PozoAbstract:Overall Root architecture is the combined result of primary and Lateral Root growth and is influenced by both intrinsic genetic programs and external signals. One of the main questions for Root biologists is how plants control the number of Lateral Root primordia and their emergence through the main Root. We recently identified S-phase kinase-associated protein2 (SKP2B) as a new early marker for Lateral Root development. Here, we took advantage of its specific expression pattern in Arabidopsis (Arabidopsis thaliana) in a cell-sorting and transcriptomic approach to generate a Lateral Root-specific cell sorting SKP2B data set that represents the endogenous genetic developmental program. We first validated this data set by showing that many of the identified genes have a function during Root growth or Lateral Root development. Importantly, genes encoding peroxidases were highly represented in our data set. Thus, we next focused on this class of enzymes and showed, using genetic and chemical inhibitor studies, that peroxidase activity and reactive oxygen species signaling are specifically required during Lateral Root emergence but, intriguingly, not for primordium specification itself.
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Auxin Transport Promotes Arabidopsis Lateral Root Initiation
The Plant Cell, 2001Co-Authors: Ilda Casimiro, Sandra Dhooge, Neil Graham, Alan Marchant, Rishikesh P Bhalerao, Ranjan Swarup, Göran Sandberg, Dirk Inze, Tom Beeckman, Pedro J. CaseroAbstract:Lateral Root development in Arabidopsis provides a model for the study of hormonal signals that regulate postembryonic organogenesis in higher plants. Lateral Roots originate from pairs of pericycle cells, in several cell files positioned opposite the xylem pole, that initiate a series of asymmetric, transverse divisions. The auxin transport inhibitor N-1-naphthylphthalamic acid (NPA) arrests Lateral Root development by blocking the first transverse division(s). We investigated the basis of NPA action by using a cell-specific reporter to demonstrate that xylem pole pericycle cells retain their identity in the presence of the auxin transport inhibitor. However, NPA causes indoleacetic acid (IAA) to accumulate in the Root apex while reducing levels in basal tissues critical for Lateral Root initiation. This pattern of IAA redistribution is consistent with NPA blocking basipetal IAA movement from the Root tip. Characterization of Lateral Root development in the shoot meristemless1 mutant demonstrates that Root basipetal and leaf acropetal auxin transport activities are required during the initiation and emergence phases, respectively, of Lateral Root development.
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Lateral Root development in a woody plant, Quercus suber L. (cork oak)
Canadian Journal of Botany, 2000Co-Authors: Dolors Verdaguer, Pedro J. Casero, Marisa MolinasAbstract:The distribution and the ontogenesis of Lateral Roots have been investigated in the Mediterranean woody species Quercus suber L. (cork oak). Lateral Roots arose in protoxylem-based ranks and a tendency to clumping was observed. Three stages are distinguished in Lateral Root primordium development. Lateral Root primordia are derived mainly from pericycle cells. The endodermis contributed to the initial Lateral Root development, forming an endodermal cover that sloughs off with Lateral Root emergence. The unemerged Lateral Roots show an incipient layered Root meristem; this meristem can be classified as a closed type meristem. Primary vascular connection takes place with the xylem strand opposite the Lateral Root primordium and the two adjacent phloem strands. Primary vascular connector elements are derived from pericyclic derivative cells. Vascular parenchyma cells contribute mainly in the development of the cambium and the subsequent secondary xylem and phloem connector elements. The secondary vascular elements of the Lateral Root and parent Root differentiate in continuity. Vascular connection is discussed in relation to the Root vascular plexus described in monocotyledonous and in some herbaceous dicotyledonous plants. An endodermis with suberized lamellae is continuous between the Lateral and parent Root in emerged Lateral Roots.Key words: Lateral Root, development pattern, apical Lateral Root meristem, Root vascular connection, Quercus suber L.
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Lateral Root development in a woody plant, Quercus suber L. (cork oak).
Canadian Journal of Botany, 2000Co-Authors: Dolors Verdaguer, Pedro J. Casero, Marisa MolinasAbstract:The distribution and the ontogenesis of Lateral Roots have been investigated in the Mediterranean woody species Quercus suber L. (cork oak). Lateral Roots arose in protoxylem-based ranks and a tendency to clumping was observed. Three stages are distinguished in Lateral Root primordium development. Lateral Root primordia are derived mainly from pericycle cells. The endodermis contributed to the initial Lateral Root development, forming an endodermal cover that sloughs off with Lateral Root emergence. The unemerged Lateral Roots show an incipient layered Root meristem; this meristem can be classified as a closed type meristem. Primary vascular connection takes place with the xylem strand opposite the Lateral Root primordium and the two adjacent phloem strands. Primary vascular connector elements are derived from pericyclic derivative cells. Vascular parenchyma cells contribute mainly in the development of the cambium and the subsequent secondary xylem and phloem connector elements. The secondary vascular el...
