Fine structure of the plasmodesm

López-Sáez, J. F.; Giménez-Martín, G.; Risueño, María Carmen

doi:10.1007/bf01247912

Cited by 72 publications

(17 citation statements)

References 6 publications

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“…The ER has often been noted to be in association with plasmodesmata (e.g. 16), where it gives rise to the desmotubule during cell plate formation (13). MacRobbie (21) (29).…”

Section: Resultsmentioning

confidence: 99%

Sodium Transport and Compartmentation in Spergularia marina

Lazof

Cheeseman²

1986

Plant Physiol.

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ABSTRACrIn this paper, a combination of tracer uptake, efflux, and pulse-chase techniques is applied to the problem of compartmentation of Na ' (4Nal) in the roots of intact, midvegetative Spergularia marina (L.) Griseb. plants. An approach is presented for conducting useful compartmental analysis when it is known that the assumptions required for staightforward interpretations of influx and efflux studies are invalid. Linear rates of 2'Na' accumulation in both roots and shoots were attained within at most a few minutes following the start of labeling. Shoot 2'Na contents equaled root contents within about 20 minutes. Analysis of root accumulation rates, and compartmental and pulse-chase efflux studies indicated that the unidirectional flux rates involved were at least an order of magnitude greater than linear rates of root and shoot accumulation. These rapid fluxes involved only a small portion of the total root Na' (about 1%). The results suggest the existence of a small symplastic compartment, distinct from the 'bulk cytoplasm,' rapidly exchanging with the medium, and responsible for delivery of Na to the xylem. The physical identity of this compartment and its physiological significance are discussed with respect to precedents in the literature.The ultimate significance of the study of root level ion transport and compartmentation in higher plants lies in the understanding of the dual role of roots as organs of ion absorption, with physiological needs of their own, and as organs responsible for nutrient resource partitioning within the whole plant. Analysis of the transport processes has been facilitated by the use of isotope techniques which allow increased resolution ofion movements with respect to both time and a large background of nontransported ions.The There has, to our knowledge, never been a consideration of the requirements for interpretable use of isotopes in transport studies using whole plants under conditions in which one could be assured that unidirectional influx was not being measured, and in which the arrangement of compartments was demonstrably not serial. In this paper we will present such a consideration, showing in particular that by combining influx and compartmental efflux techniques, each of which in itself is theoretically invalid under these circumstances, with pulse-chase studies, it is possible to characterize the compartmentation accounting for the observed ion fluxes and the partitioning between root and shoot. We will present results obtained using intact, vegetative Spergularia marina plants growing on 0.2 x sea water medium in solution culture. The particular virtues of this system have been discussed elsewhere in detail (5,6). For the present purposes, we will restrict our consideration to sodium uptake, accumulation, and translocation because of its relatively straightforward transport characteristics. MATERIALS AND METHODSSpergularia marina (L.) Griseb. seeds were collected from plants growing in our growth chambers and were germinated, transferred to solution cultur...

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“…The ER has often been noted to be in association with plasmodesmata (e.g. 16), where it gives rise to the desmotubule during cell plate formation (13). MacRobbie (21) (29).…”

Section: Resultsmentioning

confidence: 99%

Sodium Transport and Compartmentation in Spergularia marina

Lazof

Cheeseman²

1986

Plant Physiol.

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“…A consensus appears to exist that the desmotubule is connected to the ER. Lopez-Saez et al (1966) and Overall et al (1982) postulated that the desmotubule comprises a membrane channel composed of strands of ER threading through the cell wall at sites of plasmodesmata insertion, whereas a recent model proposed by Tilney et al (1991) suggests a protein-rich rod that resembles a cytoskeletal element. lnherent in the lipid tubule model (Lopez-Saez et al, 1966;Overall et al, 1982) is the idea of a physical continuity of ER membrane between cells, suggesting a potential pathway for lipophilic molecules and possibly membrane-associated proteins.…”

Section: Dlscusslonmentioning

confidence: 99%

“…Lopez-Saez et al (1966) and Overall et al (1982) postulated that the desmotubule comprises a membrane channel composed of strands of ER threading through the cell wall at sites of plasmodesmata insertion, whereas a recent model proposed by Tilney et al (1991) suggests a protein-rich rod that resembles a cytoskeletal element. lnherent in the lipid tubule model (Lopez-Saez et al, 1966;Overall et al, 1982) is the idea of a physical continuity of ER membrane between cells, suggesting a potential pathway for lipophilic molecules and possibly membrane-associated proteins. Utilizing the techniques of confocal microscopy and FRAP, an effort was initiated to test whether lipids and/or phospholipids were capable of membrane-mediated diffusion across the cell wall barrier between cells, and whether such a possible transport pathway was mediated by the plasmalemma, the ER, or both.…”

Section: Dlscusslonmentioning

confidence: 99%

“…lncorporated within this plasmalemma-delimited gap is the dominant transwall structural component of plasmodesmata called the desmotubule (Robards, 1976). Considerable efforts utilizing transmission electron microscopy have been dedicated to elucidating the structure and composition of the desmotubule (Lopez-Saez et al, 1966;Robards, 1968;Overall et al, 1982;Robards and Lucas, 1990), but as pointed out by Tilney et al (1991), the interpretations of structure "have changed repeatedly backwards and forwards." Suggestions for organization have varied between descriptions of a lipid-containing tubule connected to endoplasmic reticulum (ER) (Lopez-Saez et al, ' To whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

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Endoplasmic Reticulum Forms a Dynamic Continuum for Lipid Diffusion between Contiguous Soybean Root Cells.

1993

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lntercellular communication between plant cells for low molecular weight hydrophilic molecules occurs through plasmodesmata. These tubular structures are embedded in the plant cell wall in association with the plasmalemma and endoplasmic reticulum (ER). Transmission electron microscopy has provided strong evidence to support the view that both the ER and plasmalemma are structurally continuous across the wall at these sltes. In experiments to be described, the technique of fluorescence redistribution after photobleaching was used to examine the lateral mobility and intercellular transport capability of a number of fluorescent lipid and phospholipid analogs. These probes were shown by confocal fluorescence microscopy to partition in either the ER or plasmalemma. Results from these measurements provide evidente for cell communication between contiguous cells for probes localized predominantly in the ER. In contrast, no detectable intercellular communication was obsenred for probes residing exclusively in the plasmalemma. It was of particular interest to note that when 1-acyl-2-(N-4-nitrobenzod-oxa-l,3-diazole)aminoacylphosphatidylchoIine was utilized as a potential reporter molecule for phospholipids in the plasmalemma, it was quickly degraded to l-acyI-2-(N-4-nitrobenzo-P-oxa-l,3-diarole)aminoacyldiglyceride (NBD-DAG), which then appeared predominantly localized to the ER and nuclear envelope. This endogenously synthesized NBD-DAG was found to be capable of transfer between cells, as was exogenously incorporated NBD-DAG. Results from these investigations provide support for the following conclusions: (1) ER, but apparently not the plasmalemma, can form dynamic communication pathways for lipids across the cell wall between connecting plant cells; (2) the plasmodesmata appear to form a barrier for lipid diffusion through the plasmalemma; and (3) lipid signaling molecules such as diacylglycerol are capable of transfer between contiguous plant cells through the ER. These observations speak to issues of plant cell autonomy for lipid synthesis and mechanisms of intercellular signaling and communication.

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“…Subsequent work (Dawes et al 1961) described "a concentration of fine plasmodesmata" between cells of Helmintho cladia. The resolution of these illustrations does not permit a comparison between "plasmodesmata" of Helminthocladia and those of higher plants (Lopez-Saez et al 1966, Esau et al 1966, Robards 1968. Ramus (1969) observed a series of flattened vesicles in the aperture of the cell wall of Pseudogloiophloea when pit connections begin to form.…”

Section: Introductionmentioning

confidence: 99%

Observations on the Developmental Morphology and Fine Structure of Pit Connections in Red Algae

Hawkins

1972

CYTOLOGIA

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Fine structure of the plasmodesm

Cited by 72 publications

References 6 publications

Sodium Transport and Compartmentation in Spergularia marina

Sodium Transport and Compartmentation in Spergularia marina

Endoplasmic Reticulum Forms a Dynamic Continuum for Lipid Diffusion between Contiguous Soybean Root Cells.

Observations on the Developmental Morphology and Fine Structure of Pit Connections in Red Algae

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