A Microscale Technique for Gas Chromatography-Mass Spectrometry Measurements of Picogram Amounts of Indole-3-Acetic Acid in Plant Tissues

Edlund, Agneta; Eklöf, Staffan; Sundberg, Birgitta; Moritz, Thomas; Sandberg, Göran

doi:10.1104/pp.108.3.1043

Cited by 195 publications

(170 citation statements)

References 18 publications

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“…The magnitude of the serotonin gradient predicted from our model matches well with the reported auxin gradients, which are thought to be approximately 10-fold (Edlund et al, 1995;Uggla et al, 1996). We also compared the gradient with another likely morphogen (although one which is not GJC-related): retinoic acid.…”

Section: Comparison To Other Morphogen Gradientssupporting

confidence: 76%

Mathematical model of morphogen electrophoresis through gap junctions

Esser

Smith

Weaver

et al. 2006

Developmental Dynamics

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Gap junctional communication is important for embryonic morphogenesis. However, the factors regulating the spatial properties of small molecule signal flows through gap junctions remain poorly understood. Recent data on gap junctions, ion transporters, and serotonin during left-right patterning suggest a specific model: the net unidirectional transfer of small molecules through long-range gap junctional paths driven by an electrophoretic mechanism. However, this concept has only been discussed qualitatively, and it is not known whether such a mechanism can actually establish a gradient within physiological constraints. We review the existing functional data and develop a mathematical model of the flow of serotonin through the early Xenopus embryo under an electrophoretic force generated by ion pumps. Through computer simulation of this process using realistic parameters, we explored quantitatively the dynamics of morphogen movement through gap junctions, confirming the plausibility of the proposed electrophoretic mechanism, which generates a considerable gradient in the available time frame. The model made several testable predictions and revealed properties of robustness, cellular gradients of serotonin, and the dependence of the gradient on several developmental constants. This work quantitatively supports the plausibility of electrophoretic control of morphogen movement through gap junctions during early left-right patterning. This conceptual framework for modeling gap junctional signaling-an epigenetic patterning mechanism of wide relevance in biological regulation-suggests numerous experimental approaches in other patterning systems.

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Section: Comparison To Other Morphogen Gradientssupporting

confidence: 76%

Mathematical model of morphogen electrophoresis through gap junctions

Esser

Smith

Weaver

et al. 2006

Developmental Dynamics

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“…To provide additional evidence that auxin did accumulate in the central part of the meristem, we extended our analysis to gas chromatography and mass spectrometry (GCMS) (20,21). Because a normal wild-type meristem was too small to perform this type of analysis, we decided to use the clavata3 (clv3) mutant.…”

Section: And Supporting Text)mentioning

confidence: 99%

Computer simulations reveal properties of the cell-cell signaling network at the shoot apex in Arabidopsis

Reuille¹,

Bohn-Courseau²,

Ljung³

et al. 2006

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

324

289

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The active transport of the plant hormone auxin plays a major role in the initiation of organs at the shoot apex. Polar localized membrane proteins of the PIN1 family facilitate this transport, and recent observations suggest that auxin maxima created by these proteins are at the basis of organ initiation. This hypothesis is based on the visual, qualitative characterization of the complex distribution patterns of the PIN1 protein in Arabidopsis. To take these analyses further, we investigated the properties of the patterns using computational modeling. The simulations reveal previously undescribed properties of PIN1 distribution. In particular, they suggest an important role for the meristem summit in the distribution of auxin. We confirm these predictions by further experimentation and propose a detailed model for the dynamics of auxin fluxes at the shoot apex.auxin ͉ modeling ͉ shoot meristem T here is strong evidence that active auxin transport, generated by influx and efflux carriers, creates patterns of auxin distribution at the shoot apex. This distribution is, in turn, interpreted in terms of differential growth and cell differentiation (1-3). In Arabidopsis, AUX1, a putative influx transporter (4), is mainly located in the surface layer (L1) of the shoot apical meristem (2) (Fig. 1A). Interestingly, the protein seems to be homogeneously distributed in plasma membranes of the individual cells. Therefore, it has been proposed that AUX1 helps to restrict auxin to these layers, although additional mechanisms may be required (5). The efflux facilitator PIN1 also is localized in the surface layers of the meristem, but in contrast to AUX1 it is often localized on certain anticlinal sides of the cells only. Because neighboring cells often show coherent PIN1 positioning, it was proposed that PIN1 is responsible for directed hormone flows within the meristem L1 layer (Fig. 1 A). In particular, careful immunological studies have revealed that the membranes carrying PIN1 are preferentially oriented toward the incipient primordia, suggesting auxin transport toward the young organs (2, 3).Together, the observations so far suggest a dynamic scenario where auxin is transported to the meristem from basally localized tissues via the L1 layer. At the meristem surface, auxin is redistributed and accumulates at particular sites where it will induce the initiation of new organs. This accumulation subsequently leads to the activation of transport in the provascular tissues causing an inward directed flow (Fig. 1B). The young organ is thus transformed into an auxin sink, which depletes its surroundings from auxin and prevents the formation of new primordia in its vicinity.Although this scenario is relatively straightforward, the previous observations leave a number of questions open. First, it is not clear at all why auxin should start to accumulate at the site where a primordium will be initiated. Second, the immunolabelings reveal a very complex distribution of PIN1 proteins (Fig. 2). As a result, the interpretation of these...

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“…The root pieces were dissected in a humidified environment to prevent desiccation, weighed, and frozen in liquid nitrogen. Quantitative measurements of endogenous IAA were performed on 0.5 to 1 mg of pooled root segments by mass spectrometry (Edlund et al, 1995). Calculation of isotopic dilution was based on the addition of 13 C 6 -IAA (50 pg/mg tissue).…”

Section: Indoleacetic Acid Quantificationmentioning

confidence: 99%

Auxin Transport Promotes Arabidopsis Lateral Root Initiation

et al. 2001

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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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A Microscale Technique for Gas Chromatography-Mass Spectrometry Measurements of Picogram Amounts of Indole-3-Acetic Acid in Plant Tissues

Cited by 195 publications

References 18 publications

Mathematical model of morphogen electrophoresis through gap junctions

Mathematical model of morphogen electrophoresis through gap junctions

Computer simulations reveal properties of the cell-cell signaling network at the shoot apex in Arabidopsis

Auxin Transport Promotes Arabidopsis Lateral Root Initiation

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