The shoot apical meristem: the dynamics of a stable structure

Traas, Jan; Vernoux, Teva

doi:10.1098/rstb.2002.1091

Cited by 47 publications

(30 citation statements)

References 91 publications

(102 reference statements)

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“…Meristems are dynamic structures, in which mitosis continuously replenishes cells that are depleted by differentiation (Traas and Vernoux, 2002). The SAM undergoes several distinct changes of identity during development of flowering plants (Pidkowich et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

INCOMPOSITA: a MADS-box gene controlling prophyll development and floral meristem identity inAntirrhinum

et al. 2004

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INCOMPOSITA (INCO) is a MADS-box transcription factor and member of the functionally diverse StMADS11 clade of the MADS-box family. The most conspicuous feature of inco mutant flowers are prophylls initiated prior to first whorl sepals at lateral positions of the flower primordium. The developing prophylls physically interfere with subsequent floral organ development that results in aberrant floral architecture. INCO, which is controlled by SQUAMOSA, prevents prophyll formation in the wild type, a role that is novel among MADS-box proteins, and we discuss evolutionary implications of this function. Overexpression of INCO or SVP, a structurally related Arabidopsis MADS-box gene involved in the negative control of Arabidopsis flowering time,conditions delayed flowering in transgenic plants, suggesting that SVP and INCO have functions in common. Enhanced flowering of squamosa mutants in the inco mutant background corroborates this potential role of INCO as a floral repressor in Antirrhinum. One further,hitherto hidden, role of INCO is the positive control of Antirrhinumfloral meristem identity. This is revealed by genetic interactions between inco and mutants of FLORICAULA, a gene that controls the inflorescence to floral transition, together with SQUAMOSA. The complex regulatory and combinatorial relations between INCO, FLORICAULA and SQUAMOSA are summarised in a model that integrates observations from molecular studies as well as analyses of expression patterns and genetic interactions.

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Section: Introductionmentioning

confidence: 99%

INCOMPOSITA: a MADS-box gene controlling prophyll development and floral meristem identity inAntirrhinum

et al. 2004

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“…Its epidermal and subepidermal cells are organized into layers with very few cells moving between layers (2,3). When these cells expand they do so laterally, pushing other cells toward the periphery of the meristem.…”

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Analysis of cell division patterns in the Arabidopsis shoot apical meristem

Shapiro

Tobin

Mjolsness

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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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.cell division | computer modeling | live imaging | Arabidopsis T he Arabidopsis shoot apical meristem (SAM) is a structure at the tip of the shoot that is responsible for generating almost all of the above-ground tissue of the plant (1). Its epidermal and subepidermal cells are organized into layers with very few cells moving between layers (2, 3). When these cells expand they do so laterally, pushing other cells toward the periphery of the meristem. Division in these cells is anticlinal such that each layer remains one cell thick. The underlying mechanism determining the location of new cell walls is unknown but the qualitative properties of meristematic cell division are well documented (4-8). Perhaps the best known summary is Errera's rule, derived following observations of soap bubble formation. In the modern interpretation, the plane of division corresponds to the shortest path that will halve the mother cell. Errera, in fact, wrote that the wall would be a surface "mit constanter mittlerer Krümmung (= Minimalfläche) [with constant mean curvature (= minimal area)]" (4). Because this does not specify a location for the new cell wall, more recent authors have added to this that the mother cell divides evenly (9, 10). With this modification, Errera's rule is easily quantifiable.A second observation is Hofmeister's rule: New cell walls usually form in a plane normal to the principal axis of cell elongation (5). This rule is more difficult to quantify, because the principal axis of cell elongation is often confused with the direction of growth. Cells are asymmetrical and hence a principal direction of cell elongation can easily be calculated (e.g., the principal axis of inertia or principal component of a segmentation). The assumption is often made that because the cell is more elongated in one direction...

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“…The growth of the SAM results from cell enlargement and divisions. These processes are coordinated in such a way that the meristem summit forms a dome with a steady shape (6). Cells are continuously advected away from the tip, and their average size remains roughly constant in time and space (7).…”

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confidence: 99%

Turning a plant tissue into a living cell froth through isotropic growth

Corson

Hamant

Bohn

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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The forms resulting from growth processes are highly sensitive to the nature of the driving impetus, and to the local properties of the medium, in particular, its isotropy or anisotropy. In turn, these local properties can be organized by growth. Here, we consider a growing plant tissue, the shoot apical meristem of Arabidopsis thaliana. In plants, the resistance of the cell wall to the growing internal turgor pressure is the main factor shaping the cells and the tissues. It is well established that the physical properties of the walls depend on the oriented deposition of the cellulose microfibrils in the extracellular matrix or cell wall; this order is correlated to the highly oriented cortical array of microtubules attached to the inner side of the plasma membrane. We used oryzalin to depolymerize microtubules and analyzed its influence on the growing meristem. This had no short-term effect, but it had a profound impact on the cell anisotropy and the resulting tissue growth. The geometry of the cells became similar to that of bubbles in a soap froth. At a multicellular scale, this switch to a local isotropy induced growth into spherical structures. A theoretical model is presented in which a cellular structure grows through the plastic yielding of its walls under turgor pressure. The simulations reproduce the geometrical properties of a normal tissue if cell division is included. If not, a "cell froth" very similar to that observed experimentally is obtained. Our results suggest strong physical constraints on the mechanisms of growth regulation.shoot apical meristem | turgor regulation | microtubules | development | modeling

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The shoot apical meristem: the dynamics of a stable structure

Cited by 47 publications

References 91 publications

INCOMPOSITA: a MADS-box gene controlling prophyll development and floral meristem identity inAntirrhinum

INCOMPOSITA: a MADS-box gene controlling prophyll development and floral meristem identity inAntirrhinum

Analysis of cell division patterns in the Arabidopsis shoot apical meristem

Turning a plant tissue into a living cell froth through isotropic growth

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