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Atsushi Sakai - One of the best experts on this subject based on the ideXlab platform.
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allelopathic effects of volatile monoterpenoids produced by salvia leucophylla inhibition of cell proliferation and dna synthesis in the root Apical Meristem of brassica campestris seedlings
Journal of Chemical Ecology, 2005Co-Authors: Nami Nishida, Satoshi Tamotsu, Noriko Nagata, Chieko Saito, Atsushi SakaiAbstract:Salvia leucophylla, a shrub observed in coastal south California, produces several volatile monoterpenoids (camphor, 1,8-cineole, beta-pinene, alpha-pinene, and camphene) that potentially act as allelochemicals. The effects of these were examined using Brassica campestris as the test plant. Camphor, 1,8-cineole, and beta-pinene inhibited germination of B. campestris seeds at high concentrations, whereas alpha-pinene and camphene did not. Root growth was inhibited by all five monoterpenoids in a dose-dependent manner, but hypocotyl growth was largely unaffected. The monoterpenoids did not alter the sizes of matured cells in either hypocotyls or roots, indicating that cell expansion is relatively insensitive to these compounds. They did not decrease the mitotic index in the shoot Apical region, but specifically lowered mitotic index in the root Apical Meristem. Moreover, morphological and biochemical analyses on the incorporation of 5-bromo-2'-deoxyuridine into DNA demonstrated that the monoterpenoids inhibit both cell-nuclear and organelle DNA synthesis in the root Apical Meristem. These results suggest that the monoterpenoids produced by S. leucophylla could interfere with the growth of other plants in its vicinity through inhibition of cell proliferation in the root Apical Meristem.
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allelopathic effects of volatile monoterpenoids produced by salvia leucophylla inhibition of cell proliferation and dna synthesis in the root Apical Meristem of brassica campestris seedlings
Journal of Chemical Ecology, 2005Co-Authors: Nami Nishida, Satoshi Tamotsu, Noriko Nagata, Chieko Saito, Atsushi SakaiAbstract:Salvia leucophylla, a shrub observed in coastal south California, produces several volatile monoterpenoids (camphor, 1,8-cineole, β-pinene, α-pinene, and camphene) that potentially act as allelochemicals. The effects of these were examined using Brassica campestris as the test plant. Camphor, 1,8-cineole, and β-pinene inhibited germination of B. campestris seeds at high concentrations, whereas α-pinene and camphene did not. Root growth was inhibited by all five monoterpenoids in a dose-dependent manner, but hypocotyl growth was largely unaffected. The monoterpenoids did not alter the sizes of matured cells in either hypocotyls or roots, indicating that cell expansion is relatively insensitive to these compounds. They did not decrease the mitotic index in the shoot Apical region, but specifically lowered mitotic index in the root Apical Meristem. Moreover, morphological and biochemical analyses on the incorporation of 5-bromo-2′-deoxyuridine into DNA demonstrated that the monoterpenoids inhibit both cell-nuclear and organelle DNA synthesis in the root Apical Meristem. These results suggest that the monoterpenoids produced by S. leucophylla could interfere with the growth of other plants in its vicinity through inhibition of cell proliferation in the root Apical Meristem.
Jennifer C Fletcher - One of the best experts on this subject based on the ideXlab platform.
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shoot Apical Meristem form and function
Current Topics in Developmental Biology, 2010Co-Authors: Ji Hyung Jun, Jennifer C FletcherAbstract:The shoot Apical Meristem (SAM) generates above-ground aerial organs throughout the lifespan of higher plants. In order to fulfill this function, the Meristem must maintain a balance between the self-renewal of a reservoir of central stem cells and organ initiation from peripheral cells. The activity of the pluripotent stem cell population in the SAM is dynamically controlled by complex, overlapping signaling networks that include the feedback regulation of Meristem maintenance genes and the signaling of plant hormones. Organ initiation likewise requires the function of multifactor gene regulatory networks, as well as instructive cues from the plant hormone auxin and reciprocal signals from the shoot Meristem. Floral Meristems (FMs) are products of the reproductive SAM that sustains a transient stem cell reservoir for flower formation. Regulation of FM activity involves both feedback loops shared with the SAM and floral-specific factors. Recent studies have rapidly advanced our understanding of SAM function by adopting newly developed molecular and computational techniques. These advances are becoming integrated with data from traditional molecular genetics methodologies to develop a framework for understanding the central principles of SAM function.
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stem cell regulation in the arabidopsis shoot Apical Meristem
Current Opinion in Plant Biology, 2005Co-Authors: Leor Eshed Williams, Jennifer C FletcherAbstract:The aerial structure of higher plants is generated dynamically throughout the life cycle through the activity of stem cells that are located at the growing shoot tip, the Apical Meristem. The stem cells continuously divide to renew themselves and provide cells for leaf, stem and flower formation. Stem cell maintenance is governed by intercellular communication between the Apical stem cells and the underlying organizing centre. Recent advances have been made in understanding the mechanisms that induce shoot stem cell identity, and that control the position and size of the organizing centre. Elements such as chromatin remodeling factors, transcription factors and microRNAs are newly implicated in these regulatory processes. These advances provide a framework for our understanding of how signals are integrated to specify and position the stem cell niche in the shoot Apical Meristem.
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shoot Apical Meristem maintenance the art of a dynamic balance
Trends in Plant Science, 2003Co-Authors: Cristel C Carles, Jennifer C FletcherAbstract:The aerial structure of higher plants derives from cells at the tip of the stem, in the shoot Apical Meristem (SAM). Throughout the life of a plant, the SAM produces stem tissues and lateral organs, and also regenerates itself. For correct growth, the plant must maintain a constant flow of cells through the Meristem, where the input of dividing pluripotent stem cells offsets the output of differentiating cells. This flow depends on extracellular signaling within the SAM, governed by a spatial regulatory feedback loop that maintains a reservoir of stem cells, and on factors that prevent Meristem cells from differentiating prematurely. The terminating floral Meristem incorporates the spatial regulation scheme into a temporal regulation pathway involving flower patterning factors.
Jan Traas - One of the best experts on this subject based on the ideXlab platform.
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Systems analysis of shoot Apical Meristem growth and development: integrating hormonal and mechanical signaling
The Plant cell, 2012Co-Authors: James Murray, Angharad Jones, Christophe Godin, Jan TraasAbstract:The shoot Apical Meristem (SAM) is a small population of stem cells that continuously generates organs and tissues. This review covers our current understanding of organ initiation by the SAM in Arabidopsis thaliana. Meristem function and maintenance involves two major hormones, cytokinins and auxins. Cytokinins appear to play a major role in Meristem maintenance and in controlling Meristematic properties, such as cell proliferation. Self-organizing transport processes, which are still only partially understood, lead to the patterned accumulation of auxin at particular positions, where organs will grow out. A major downstream target of auxin-mediated growth regulation is the cell wall, which is a determinant for both growth rates and growth distribution, but feedbacks with metabolism and the synthetic capacity of the cytoplasm are crucial as well. Recent work has also pointed at a potential role of mechanical signals in growth coordination, but the precise mechanisms at work remain to be elucidated.
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Auxin at the shoot Apical Meristem
Cold Spring Harbor Perspectives in Biology, 2010Co-Authors: Teva Vernoux, Fabrice Besnard, Jan TraasAbstract:Plants continuously generate new tissues and organs through the activity of populations of undifferentiated stem cells, called Meristems. Here, we discuss the so-called shoot Apical Meristem (SAM), which generates all the aerial parts of the plant. It has been known for many years that auxin plays a central role in the functioning of this Meristem. Auxin is not homogeneously distributed at the SAM and it is thought that this distribution is interpreted in terms of differential gene expression and patterned growth. In this context, auxin transporters of the PIN and AUX families, creating auxin maxima and minima, are crucial regulators. However, auxin transport is not the only factor involved. Auxin biosynthesis genes also show specific, patterned activities, and local auxin synthesis appears to be essential for Meristem function as well. In addition, auxin perception and signal transduction defining the competence of cells to react to auxin, add further complexity to the issue. To unravel this intricate signaling network at the SAM, systems biology approaches, involving not only molecular genetics but also live imaging and computational modeling, have become increasingly important.
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cellular parameters of the shoot Apical Meristem in arabidopsis
The Plant Cell, 1998Co-Authors: Patrick Laufs, Olivier Grandjean, Claudia Jonak, Kien Kieu, Jan TraasAbstract:The shoot Apical Meristem (SAM) is a small group of dividing cells that generate all of the aerial parts of the plant. With the goal of providing a framework for the analysis of Arabidopsis Meristems at the cellular level, we performed a detailed morphometric study of actively growing inflorescence apices of the Landsberg erecta and Wassilewskija ecotypes. For this purpose, cell size, spatial distribution of mitotic cells, and the mitotic index were determined in a series of optical sections made with a confocal laser scanning microscope. The results allowed us to identify zones within the inflorescence SAM with different cell proliferation rates. In particular, we were able to define a central area that was four to six cells wide and had a low mitotic index. We used this technique to compare the Meristem of the wild type with the enlarged Meristems of two mutants, clavata3-1 (clv3-1) and mgoun2 (mgo2). One of the proposed functions of the CLV genes is to limit cell division rates in the center of the Meristem. Our data allowed us to reject this hypothesis, because the mitotic index was reduced in the inflorescence Meristem of the clv3-1 mutant. We also observed a large zone of slowly dividing cells in Meristems of clv3-1 seedlings. This zone was not detectable in the wild type. These results suggest that the central area is increased in size in the mutant Meristem, which is in line with the hypothesis that the CLV3 gene is necessary for the transition of cells from the central to the peripheral zone. Genetic and microscopic analyses suggest that mgo2 is impaired in the production of primordia, and we previously proposed that the increased size of the mgo2 Meristem could be due to an accumulation of cells at the periphery. Our morphometric analysis showed that mgo2 Meristems, in contrast to those of clv3-1, have an enlarged periphery with high cell proliferation rates. This confirms that clv3-1 and mgo2 lead to Meristem overgrowth by affecting different aspects of Meristem function.
Allan G. Rasmusson - One of the best experts on this subject based on the ideXlab platform.
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The antibiotic peptaibol alamethicin from Trichoderma permeabilises Arabidopsis root Apical Meristem and epidermis but is antagonised by cellulase-induced resistance to alamethicin.
BMC Plant Biology, 2018Co-Authors: Bradley R. Dotson, Dia Soltan, John Schmidt, Mariam Areskoug, Kenny Rabe, Corné Swart, Susanne Widell, Allan G. RasmussonAbstract:Trichoderma fungi live in the soil rhizosphere and are beneficial for plant growth and pathogen resistance. Several species and strains are currently used worldwide in co-cultivation with crops as a biocontrol alternative to chemical pesticides even though little is known about the exact mechanisms of the beneficial interaction. We earlier found alamethicin, a peptide antibiotic secreted by Trichoderma, to efficiently permeabilise cultured tobacco cells. However, pre-treatment with Trichoderma cellulase made the cells resistant to subsequent alamethicin, suggesting a potential mechanism for plant tolerance to Trichoderma, needed for mutualistic symbiosis. We here investigated intact sterile-grown Arabidopsis thaliana seedlings germinated in water or growth medium. These could be permeabilised by alamethicin but not if pretreated with cellulase. By following the fluorescence from the membrane-impermeable DNA-binding probe propidium iodide, we found alamethicin to mainly permeabilise root tips, especially the Apical Meristem and epidermis cells, but not the root cap and basal Meristem cells nor cortex cells. Alamethicin permeabilisation and cellulase-induced resistance were confirmed by developing a quantitative in situ assay based on NADP-isocitrate dehydrogenase accessibility. The combined assays also showed that hyperosmotic treatment after the cellulase pretreatment abolished the induced cellulase resistance. We here conclude the presence of cell-specific alamethicin permeabilisation, and cellulase-induced resistance to it, in root tip Apical Meristem and epidermis of the model organism A. thaliana. We suggest that contact between the plasma membrane and the cell wall is needed for the resistance to remain. Our results indicate a potential mode for the plant to avoid negative effects of alamethicin on plant growth and localises the point of potential damage and response. The results also open up for identification of plant genetic components essential for beneficial effects from Trichoderma on plants.
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The antibiotic peptaibol alamethicin from Trichoderma permeabilises Arabidopsis root Apical Meristem and epidermis but is antagonised by cellulase-induced resistance to alamethicin
BMC, 2018Co-Authors: Bradley R. Dotson, Dia Soltan, John Schmidt, Mariam Areskoug, Kenny Rabe, Corné Swart, Susanne Widell, Allan G. RasmussonAbstract:Abstract Background Trichoderma fungi live in the soil rhizosphere and are beneficial for plant growth and pathogen resistance. Several species and strains are currently used worldwide in co-cultivation with crops as a biocontrol alternative to chemical pesticides even though little is known about the exact mechanisms of the beneficial interaction. We earlier found alamethicin, a peptide antibiotic secreted by Trichoderma, to efficiently permeabilise cultured tobacco cells. However, pre-treatment with Trichoderma cellulase made the cells resistant to subsequent alamethicin, suggesting a potential mechanism for plant tolerance to Trichoderma, needed for mutualistic symbiosis. Results We here investigated intact sterile-grown Arabidopsis thaliana seedlings germinated in water or growth medium. These could be permeabilised by alamethicin but not if pretreated with cellulase. By following the fluorescence from the membrane-impermeable DNA-binding probe propidium iodide, we found alamethicin to mainly permeabilise root tips, especially the Apical Meristem and epidermis cells, but not the root cap and basal Meristem cells nor cortex cells. Alamethicin permeabilisation and cellulase-induced resistance were confirmed by developing a quantitative in situ assay based on NADP-isocitrate dehydrogenase accessibility. The combined assays also showed that hyperosmotic treatment after the cellulase pretreatment abolished the induced cellulase resistance. Conclusion We here conclude the presence of cell-specific alamethicin permeabilisation, and cellulase-induced resistance to it, in root tip Apical Meristem and epidermis of the model organism A. thaliana. We suggest that contact between the plasma membrane and the cell wall is needed for the resistance to remain. Our results indicate a potential mode for the plant to avoid negative effects of alamethicin on plant growth and localises the point of potential damage and response. The results also open up for identification of plant genetic components essential for beneficial effects from Trichoderma on plants
Elliot M. Meyerowitz - One of the best experts on this subject based on the ideXlab platform.
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primary wall cellulose synthase regulates shoot Apical Meristem mechanics and growth
Development, 2019Co-Authors: Arun Sampathkumar, Geoffrey O Wasteneys, Alexis Peaucelle, Miki Fujita, Christoph Schuster, Staffan Persson, Elliot M. MeyerowitzAbstract:How organisms attain their specific shapes and modify their growth patterns in response to environmental and chemical signals has been the subject of many investigations. Plant cells are at high turgor pressure and are surrounded by a rigid yet flexible cell wall, which is the primary determinant of plant growth and morphogenesis. Cellulose microfibrils, synthesized by plasma membrane-localized cellulose synthase complexes, are major tension-bearing components of the cell wall that mediate directional growth. Despite advances in understanding the genetic and biophysical regulation of morphogenesis, direct studies of cellulose biosynthesis and its impact on morphogenesis of different cell and tissue types are largely lacking. In this study, we took advantage of mutants of three primary cellulose synthase (CESA) genes that are involved in primary wall cellulose synthesis. Using field emission scanning electron microscopy, live cell imaging and biophysical measurements, we aimed to understand how the primary wall CESA complex acts during shoot Apical Meristem development. Our results indicate that cellulose biosynthesis impacts the mechanics and growth of the shoot Apical Meristem.
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analysis of cell division patterns in the arabidopsis shoot Apical Meristem
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Bruce E Shapiro, Cory Tobin, Eric Mjolsness, Elliot M. MeyerowitzAbstract:The stereotypic pattern of cell shapes in the Arabidopsis shoot Apical Meristem (SAM) suggests that strict rules govern the placement of new walls during cell division. When a cell in the SAM divides, a new wall is built that connects existing walls and divides the cytoplasm of the daughter cells. Because features that are determined by the placement of new walls such as cell size, shape, and number of neighbors are highly regular, rules must exist for maintaining such order. Here we present a quantitative model of these rules that incorporates different observed features of cell division. Each feature is incorporated into a “potential function” that contributes a single term to a total analog of potential energy. New cell walls are predicted to occur at locations where the potential function is minimized. Quantitative terms that represent the well-known historical rules of plant cell division, such as those given by Hofmeister, Errera, and Sachs are developed and evaluated against observed cell divisions in the epidermal layer (L1) of Arabidopsis thaliana SAM. The method is general enough to allow additional terms for nongeometric properties such as internal concentration gradients and mechanical tensile forces.
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the shoot Apical Meristem regulatory peptide clv3 does not activate innate immunity
The Plant Cell, 2012Co-Authors: Cecile Segonzac, Elliot M. Meyerowitz, Zachary L Nimchuk, Martina Beck, Paul T Tarr, Silke Robatzek, Cyril ZipfelAbstract:The Arabidopsis thaliana leucine-rich repeat receptor kinase FLAGELLIN SENSING2 (FLS2) is required for the recognition of bacterial flagellin in innate immunity. Recently, FLS2 was proposed to act as a multispecific receptor recognizing unrelated exogenous and endogenous peptide ligands, including CLAVATA3 (CLV3), a key regulator of shoot Meristem stem cell production. Here, we report experimental evidence demonstrating that FLS2 does not recognize CLV3 and that the shoot Apical Meristem is immune to bacteria independently of CLV3 perception.
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Segmenting the sepal and shoot Apical Meristem of Arabidopsis thaliana
2010 Annual International Conference of the IEEE Engineering in Medicine and Biology, 2010Co-Authors: Alexandre L. Cunha, Adrienne H. K. Roeder, Elliot M. MeyerowitzAbstract:We present methods for segmenting the sepal and shoot Apical Meristem of the Arabidopsis thaliana plant. We propose a mathematical morphology pipeline and a modified numerical scheme for the active contours without edges algorithm to extract the geometry and topology of plant cells imaged using confocal laser scanning microscopy. We demonstrate our methods in typical images used in the studies of cell endoreduplication and hormone transport and show that in practice they produce highly accurate results requiring little human intervention to cope with image aberrations.