The Experts below are selected from a list of 903 Experts worldwide ranked by ideXlab platform
Eddie Wisse - One of the best experts on this subject based on the ideXlab platform.
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antimycin a induced defenestration in rat hepatic sinusoidal endothelial cells
Hepatology, 2003Co-Authors: Filip Braet, Eddie Wisse, Michael Muller, Katrien Vekemans, David Le G CouteurAbstract:Liver sinusoidal endothelial cells (LSECs) possess fenestrae arranged in Sieve Plates. Hepatic endothelial fenestrae are open pores approximately 100 to 200 nm in diameter. Alterations in their number or diameter by hormones, xenobiotics, and diseases have important implications for hepatic microcirculation and function. Numerous reports of hepatotoxin-induced defenestration suggest that the cytoskeleton and the energy status of hepatic endothelial cells play a key role in the regulation of fenestrae. Therefore, we investigated the effect of antimycin A, an inhibitor of mitochondrial energy production, on the number of fenestrae in cultured LSECs using high-resolution microscopy and immunocytochemistry. Prolonged incubation (greater than 30 min) with antimycin A resulted in defenestrated cells and coincided with the appearance of F-actin dots, whereas the distribution of G-actin remained unchanged. Adenosine triphosphate (ATP) was depleted dramatically to less than 5% within 30 minutes within the LSECs. After treatment with antimycin A, unusual elevated fenestrated complexes were apparent, organized as a meshwork of anastomosing fenestrae at the center of and above the Sieve Plates. The position and appearance of these novel structures and their association with defenestration suggest that they are implicated in the process of defenestration. In conclusion, the results of experiments with antimycin A suggest that ATP is needed to maintain fenestrae and the underlying fenestrae-associated cytoskeleton rings that maintain fenestrae patency. Antimycin A-induced defenestration of LSECs is associated with the development of a structure in the Sieve plate that appears to be intrinsically involved in defenestration.
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drying cells for sem afm and tem by hexamethyldisilazane a study on hepatic endothelial cells
Journal of Microscopy, 1997Co-Authors: Filip Braet, R De Zanger, Eddie WisseAbstract:Critical point drying (CPD) is a common method of drying biological specimens for scanning electron microscopy (SEM). Drying by evaporation of hexamethyldisilazane (HMDS) has been described as a good alternative. This method, however, is infrequently used. Therefore, we reassessed HMDS drying. Cultured rat hepatic sinusoidal endothelial cells (LEC), possessing fragile fenestrae and Sieve Plates, were subjected to CPD and HMDS drying and evaluated in the scanning electron microscope, atomic force microscope (AFM) and transmission electron microscope (TEM). We observed no differences between the two methods regarding cellular ultrastructure. In contrast with CPD, HMDS drying takes only a few minutes, less effort, low costs for chemicals and requires no equipment. We conclude that HMDS-dried specimens have equal quality to CPD ones. Furthermore, the method also proved useful for drying whole-mount cells for TEM and AFM.
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structure and function of sinusoidal lining cells in the liver
Toxicologic Pathology, 1996Co-Authors: Eddie Wisse, Filip Braet, Dianzhong Luo, Ronald De Zanger, Danny Jans, Evelyne Crabbe, A N VermoesenAbstract:The hepatic sinusoid harbors 4 different cells: endothelial cells (100, 101), Kupffer cells (96, 102, 103), fat-storing cells (34, 51, 93), and pit cells (14, 107. 108). Each cell type has its own specific morphology and functions, and no transitional stages exist between the cells. These cells have the potential to proliferate locally, either in normal or in special conditions, that is, experiments or disease. Sinusoidal cells form a functional unit together with the parenchymal cells. Isolation protocols exist for all sinusoidal cells. Endothelial cells filter the fluids, exchanged between the sinusoid and the space of Disse through fenestrae (100), which measure 175 nm in diameter and are grouped in Sieve Plates. Fenestrae occupy 6-8% of the surface (106). No intact basal lamina is present under these cells (100). Various factors change the number and diameter of fenestrae [pressure, alcohol, serotonin, and nicotin; for a review, see Fraser et al (32)]. These changes mainly affect the passage of lipopr...
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structure and dynamics of the fenestrae associated cytoskeleton of rat liver sinusoidal endothelial cells
Hepatology, 1995Co-Authors: Filip Braet, Ronald De Zanger, Evelyne Crabbe, Marijke Baekeland, Patrick Van Der Smissen, Eddie WisseAbstract:This article describes the cytoskeleton associated with fenestrae and Sieve Plates of rat liver sinusoidal endothelial cells. Fenestrae control the exchange between the blood and parenchymal cells. We present evidence indicating that several agents that change the fenestrae and Sieve Plates also cause changes in the cytoskeleton. Cultured liver endothelial cells (LECs) were slightly fixed and treated with cytoskeleton extraction buffer. Detergent-extracted whole mounts of cultured cells were prepared for either scanning electron microscopy (SEM) or transmission electron microscopy (TEM). Extracted cells show an integral intricate cytoskeleton; Sieve Plates and fenestrae are delineated by cytoskeleton elements. Fenestrae are surrounded by a filamentous, fenestrae-associated cytoskeleton with a mean filament thickness of 16 nm. Sieve Plates are surrounded and delineated by microtubuli, which form a network together with additional branching cytoskeletal elements. The addition of ethanol to cultured cells enlarged the diameter for these fenestrae-associated cytoskeleton rings by 5%, whereas serotonin treatment reduced the diameter by 20%. These observations indicate that the fenestrae-associated cytoskeleton probably changes the size of fenestrae after different treatments. After treatment with cytochalasin B the number of fenestrae increased. However, cytochalasin B did not change the structure of the fenestrae-associated cytoskeleton ring, but disperses the microtubuli. In conclusion, LECs have a cytoskeleton that defines and supports Sieve Plates and fenestrae. Fenestrae-associated cytoskeleton is a dynamic structure and plays a role in maintaining and regulating the size of fenestrae after different treatments. Therefore, the fenestrae-associated cytoskeleton controls the important hepatic function of endothelial filtration.
Alexandra C U Furch - One of the best experts on this subject based on the ideXlab platform.
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interaction of xylem and phloem during exudation and wound occlusion in cucurbita maxima
Plant Cell and Environment, 2013Co-Authors: Matthias R Zimmermann, Jens B Hafke, Alexandra C U FurchAbstract:: Collection of cucurbit exudates from cut petioles has been a powerful tool for gaining knowledge on phloem sap composition without full notion of the complex exudation mechanism. Only few publications explicitly mentioned that exudates were collected from the basal side of the cut, which exudes more copiously than the apical side. This is surprising since only exudation from the apical side is supposedly driven by phloem pressure gradients. Composition of carbohydrates and pH values at both wounding sides are equal, whereas protein concentration is higher at the basal side. Apparently, exudation is far more complex than just the delivery of phloem sap. Xylem involvement is indicated by lower protein concentrations after elimination of root pressure. Moreover, dye was sucked into xylem vessels owing to relaxation of negative pressure after cutting. The lateral water efflux from the vessels increases turgor of surrounding cells including Sieve elements. Simultaneously, detached parietal proteins (PP1/PP2) induce occlusion of Sieve Plates and cover wound surface. If root pressure is strong enough, pure xylem sap can be collected after removal of the occlusion plug at the wound surface. The present findings provide a mechanism of sap exudation in Cucurbita maxima, in which the contribution of xylem water is integrated.
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aphid watery saliva counteracts Sieve tube occlusion a universal phenomenon
The Journal of Experimental Biology, 2009Co-Authors: Torsten Will, Alexandra C U Furch, Fred W Tjallingii, Sarah R Kornemann, Aart J. E. Van BelAbstract:Ca2+-binding proteins in the watery saliva of Megoura viciae counteract Ca2+-dependent occlusion of Sieve Plates in Vicia faba and so prevent the shut-down of food supply in response to stylet penetration. The question arises whether this interaction between aphid saliva and Sieve-element proteins is a universal phenomenon as inferred by the coincidence between Sieve-tube occlusion and salivation. For this purpose, leaf tips were burnt in a number of plant species from four different families to induce remote Sieve-plate occlusion. Resultant Sieve-plate occlusion in these plant species was counteracted by an abrupt switch of aphid behaviour. Each of the seven aphid species tested interrupted its feeding behaviour and started secreting watery saliva. The protein composition of watery saliva appeared strikingly different between aphid species with less than 50% overlap. Secretion of watery saliva seems to be a universal means to suppress Sieve-plate occlusion, although the protein composition of watery saliva seems to diverge between species.
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Sieve element ca2 channels as relay stations between remote stimuli and Sieve tube occlusion in vicia faba
The Plant Cell, 2009Co-Authors: Alexandra C U Furch, Aart J. E. Van Bel, Mark D Fricker, Hubert H Felle, Maike Fuchs, Jens B HafkeAbstract:Damage induces remote occlusion of Sieve tubes in Vicia faba by forisome dispersion, triggered during the passage of an electropotential wave (EPW). This study addresses the role of Ca2+ channels and cytosolic Ca2+ elevation as a link between EPWs and forisome dispersion. Ca2+ channel antagonists affect the initial phase of the EPW as well as the prolonged plateau phase. Resting levels of Sieve tube Ca2+ of ∼50 nM were independently estimated using Ca2+-selective electrodes and a Ca2+-sensitive dye. Transient changes in cytosolic Ca2+ were observed in phloem tissue in response to remote stimuli and showed profiles similar to those of EPWs. The measured elevation of Ca2+ in Sieve tubes was below the threshold necessary for forisome dispersion. Therefore, forisomes need to be associated with Ca2+ release sites. We found an association between forisomes and endoplasmic reticulum (ER) at Sieve Plates and pore-plasmodesma units where high-affinity binding of a fluorescent Ca2+ channel blocker mapped an increased density of Ca2+ channels. In conclusion, propagation of EPWs in response to remote stimuli is linked to forisome dispersion through transiently high levels of parietal Ca2+, release of which depends on both plasma membrane and ER Ca2+ channels.
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Sieve element Ca2+ channels as relay stations between remote stimuli and Sieve tube occlusion in Vicia faba.
'American Society of Plant Biologists (ASPB)', 2009Co-Authors: Alexandra C U Furch, Hubert H Felle, Aj ,van Bel, Fuchs M, Jens B HafkeAbstract:Damage induces remote occlusion of Sieve tubes in Vicia faba by forisome dispersion, triggered during the passage of an electropotential wave (EPW). This study addresses the role of Ca2+ channels and cytosolic Ca2+ elevation as a link between EPWs and forisome dispersion. Ca2+ channel antagonists affect the initial phase of the EPW as well as the prolonged plateau phase. Resting levels of Sieve tube Ca2+ of approximately 50 nM were independently estimated using Ca2+-selective electrodes and a Ca2+-sensitive dye. Transient changes in cytosolic Ca2+ were observed in phloem tissue in response to remote stimuli and showed profiles similar to those of EPWs. The measured elevation of Ca2+ in Sieve tubes was below the threshold necessary for forisome dispersion. Therefore, forisomes need to be associated with Ca2+ release sites. We found an association between forisomes and endoplasmic reticulum (ER) at Sieve Plates and pore-plasmodesma units where high-affinity binding of a fluorescent Ca2+ channel blocker mapped an increased density of Ca2+ channels. In conclusion, propagation of EPWs in response to remote stimuli is linked to forisome dispersion through transiently high levels of parietal Ca2+, release of which depends on both plasma membrane and ER Ca2+ channels
Filip Braet - One of the best experts on this subject based on the ideXlab platform.
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antimycin a induced defenestration in rat hepatic sinusoidal endothelial cells
Hepatology, 2003Co-Authors: Filip Braet, Eddie Wisse, Michael Muller, Katrien Vekemans, David Le G CouteurAbstract:Liver sinusoidal endothelial cells (LSECs) possess fenestrae arranged in Sieve Plates. Hepatic endothelial fenestrae are open pores approximately 100 to 200 nm in diameter. Alterations in their number or diameter by hormones, xenobiotics, and diseases have important implications for hepatic microcirculation and function. Numerous reports of hepatotoxin-induced defenestration suggest that the cytoskeleton and the energy status of hepatic endothelial cells play a key role in the regulation of fenestrae. Therefore, we investigated the effect of antimycin A, an inhibitor of mitochondrial energy production, on the number of fenestrae in cultured LSECs using high-resolution microscopy and immunocytochemistry. Prolonged incubation (greater than 30 min) with antimycin A resulted in defenestrated cells and coincided with the appearance of F-actin dots, whereas the distribution of G-actin remained unchanged. Adenosine triphosphate (ATP) was depleted dramatically to less than 5% within 30 minutes within the LSECs. After treatment with antimycin A, unusual elevated fenestrated complexes were apparent, organized as a meshwork of anastomosing fenestrae at the center of and above the Sieve Plates. The position and appearance of these novel structures and their association with defenestration suggest that they are implicated in the process of defenestration. In conclusion, the results of experiments with antimycin A suggest that ATP is needed to maintain fenestrae and the underlying fenestrae-associated cytoskeleton rings that maintain fenestrae patency. Antimycin A-induced defenestration of LSECs is associated with the development of a structure in the Sieve plate that appears to be intrinsically involved in defenestration.
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drying cells for sem afm and tem by hexamethyldisilazane a study on hepatic endothelial cells
Journal of Microscopy, 1997Co-Authors: Filip Braet, R De Zanger, Eddie WisseAbstract:Critical point drying (CPD) is a common method of drying biological specimens for scanning electron microscopy (SEM). Drying by evaporation of hexamethyldisilazane (HMDS) has been described as a good alternative. This method, however, is infrequently used. Therefore, we reassessed HMDS drying. Cultured rat hepatic sinusoidal endothelial cells (LEC), possessing fragile fenestrae and Sieve Plates, were subjected to CPD and HMDS drying and evaluated in the scanning electron microscope, atomic force microscope (AFM) and transmission electron microscope (TEM). We observed no differences between the two methods regarding cellular ultrastructure. In contrast with CPD, HMDS drying takes only a few minutes, less effort, low costs for chemicals and requires no equipment. We conclude that HMDS-dried specimens have equal quality to CPD ones. Furthermore, the method also proved useful for drying whole-mount cells for TEM and AFM.
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structure and function of sinusoidal lining cells in the liver
Toxicologic Pathology, 1996Co-Authors: Eddie Wisse, Filip Braet, Dianzhong Luo, Ronald De Zanger, Danny Jans, Evelyne Crabbe, A N VermoesenAbstract:The hepatic sinusoid harbors 4 different cells: endothelial cells (100, 101), Kupffer cells (96, 102, 103), fat-storing cells (34, 51, 93), and pit cells (14, 107. 108). Each cell type has its own specific morphology and functions, and no transitional stages exist between the cells. These cells have the potential to proliferate locally, either in normal or in special conditions, that is, experiments or disease. Sinusoidal cells form a functional unit together with the parenchymal cells. Isolation protocols exist for all sinusoidal cells. Endothelial cells filter the fluids, exchanged between the sinusoid and the space of Disse through fenestrae (100), which measure 175 nm in diameter and are grouped in Sieve Plates. Fenestrae occupy 6-8% of the surface (106). No intact basal lamina is present under these cells (100). Various factors change the number and diameter of fenestrae [pressure, alcohol, serotonin, and nicotin; for a review, see Fraser et al (32)]. These changes mainly affect the passage of lipopr...
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structure and dynamics of the fenestrae associated cytoskeleton of rat liver sinusoidal endothelial cells
Hepatology, 1995Co-Authors: Filip Braet, Ronald De Zanger, Evelyne Crabbe, Marijke Baekeland, Patrick Van Der Smissen, Eddie WisseAbstract:This article describes the cytoskeleton associated with fenestrae and Sieve Plates of rat liver sinusoidal endothelial cells. Fenestrae control the exchange between the blood and parenchymal cells. We present evidence indicating that several agents that change the fenestrae and Sieve Plates also cause changes in the cytoskeleton. Cultured liver endothelial cells (LECs) were slightly fixed and treated with cytoskeleton extraction buffer. Detergent-extracted whole mounts of cultured cells were prepared for either scanning electron microscopy (SEM) or transmission electron microscopy (TEM). Extracted cells show an integral intricate cytoskeleton; Sieve Plates and fenestrae are delineated by cytoskeleton elements. Fenestrae are surrounded by a filamentous, fenestrae-associated cytoskeleton with a mean filament thickness of 16 nm. Sieve Plates are surrounded and delineated by microtubuli, which form a network together with additional branching cytoskeletal elements. The addition of ethanol to cultured cells enlarged the diameter for these fenestrae-associated cytoskeleton rings by 5%, whereas serotonin treatment reduced the diameter by 20%. These observations indicate that the fenestrae-associated cytoskeleton probably changes the size of fenestrae after different treatments. After treatment with cytochalasin B the number of fenestrae increased. However, cytochalasin B did not change the structure of the fenestrae-associated cytoskeleton ring, but disperses the microtubuli. In conclusion, LECs have a cytoskeleton that defines and supports Sieve Plates and fenestrae. Fenestrae-associated cytoskeleton is a dynamic structure and plays a role in maintaining and regulating the size of fenestrae after different treatments. Therefore, the fenestrae-associated cytoskeleton controls the important hepatic function of endothelial filtration.
Michael Knoblauch - One of the best experts on this subject based on the ideXlab platform.
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In situ microscopy reveals reversible cell wall swelling in kelp Sieve tubes: one mechanism for turgor generation and flow control?
Plant Cell and Environment, 2016Co-Authors: Jan Knoblauch, Sarah Tepler Drobnitch, Winfried S Peters, Michael KnoblauchAbstract:Kelps, brown algae (Phaeophyceae) of the order Laminariales, possess Sieve tubes for the symplasmic long-distance transport of photoassimilates that are evolutionarily unrelated but structurally similar to the tubes in the phloem of vascular plants. We visualized Sieve tube structure and wound responses in fully functional, intact Bull Kelp (Nereocystis luetkeana [K. Mertens] Postels & Ruprecht 1840). In injured tubes, apparent slime plugs formed but were unlikely to cause Sieve tube occlusion as they assembled at the downstream side of Sieve Plates. Cell walls expanded massively in the radial direction, reducing the volume of the wounded Sieve elements by up to 90%. Ultrastructural examination showed that a layer of the immediate cell wall characterized by circumferential cellulose fibrils was responsible for swelling, and suggested that alginates, abundant gelatinous polymers of the cell wall matrix, were involved. Wall swelling was rapid, reversible, and depended on intracellular pressure, as demonstrated by pressure-injection of silicon oil. Our results revive the concept of turgor generation and buffering by swelling cell walls, which had fallen into oblivion over the last century. Because Sieve tube transport is pressure-driven and controlled physically by tube diameter, a regulatory role of wall swelling in photoassimilate distribution is implied in kelps.
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Modeling the Hydrodynamics of Phloem Sieve Plates
Frontiers in plant science, 2012Co-Authors: Kaare Hartvig Jensen, Michael Knoblauch, Daniel L. Mullendore, Noel Michele Holbrook, Tomas Bohr, Henrik BruusAbstract:Sieve Plates have an enormous impact on the efficiency of the phloem vascular system of plants, responsible for the distribution of photosynthetic products. These thin Plates, which separate neighboring phloem cells, are perforated by a large number of tiny Sieve pores and are believed to play a crucial role in protecting the phloem sap from intruding animals by blocking flow when the phloem cell is damaged. The resistance to the flow of viscous sap in the phloem vascular system is strongly affected by the presence of the Sieve Plates, but the hydrodynamics of the flow through them remains poorly understood. We propose a theoretical model for quantifying the effect of Sieve Plates on the phloem in the plant, thus unifying and improving previous work in the field. Numerical simulations of the flow in real and idealized phloem channels verify our model, and anatomical data from 19 plant species are investigated. We find that the Sieve plate resistance is correlated to the cell lumen resistance, and that the Sieve plate and the lumen contribute almost equally to the total hydraulic resistance of the phloem translocation pathway.
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Sieve tube geometry in relation to phloem flow
The Plant Cell, 2010Co-Authors: Daniel L. Mullendore, Carel W Windt, Henk Van As, Michael KnoblauchAbstract:Sieve elements are one of the least understood cell types in plants. Translocation velocities and volume flow to supply sinks with photoassimilates greatly depend on the geometry of the microfluidic Sieve tube system and especially on the anatomy of Sieve Plates and Sieve plate pores. Several models for phloem translocation have been developed, but appropriate data on the geometry of pores, Plates, Sieve elements, and flow parameters are lacking. We developed a method to clear cells from cytoplasmic constituents to image cell walls by scanning electron microscopy. This method allows high-resolution measurements of Sieve element and Sieve plate geometries. Sieve tube‐specific conductivity and its reduction by callose deposition after injury was calculated for green bean (Phaseolus vulgaris), bamboo (Phyllostachys nuda), squash (Cucurbita maxima), castor bean (Ricinus communis), and tomato (Solanum lycopersicum). Phloem sap velocity measurements by magnetic resonance imaging velocimetry indicate that higher conductivity is not accompanied by a higher velocity. Studies on the temporal development of callose show that small Sieve plate pores might be occluded by callose within minutes, but plants containing Sieve tubes with large pores need additional mechanisms.
Jens B Hafke - One of the best experts on this subject based on the ideXlab platform.
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interaction of xylem and phloem during exudation and wound occlusion in cucurbita maxima
Plant Cell and Environment, 2013Co-Authors: Matthias R Zimmermann, Jens B Hafke, Alexandra C U FurchAbstract:: Collection of cucurbit exudates from cut petioles has been a powerful tool for gaining knowledge on phloem sap composition without full notion of the complex exudation mechanism. Only few publications explicitly mentioned that exudates were collected from the basal side of the cut, which exudes more copiously than the apical side. This is surprising since only exudation from the apical side is supposedly driven by phloem pressure gradients. Composition of carbohydrates and pH values at both wounding sides are equal, whereas protein concentration is higher at the basal side. Apparently, exudation is far more complex than just the delivery of phloem sap. Xylem involvement is indicated by lower protein concentrations after elimination of root pressure. Moreover, dye was sucked into xylem vessels owing to relaxation of negative pressure after cutting. The lateral water efflux from the vessels increases turgor of surrounding cells including Sieve elements. Simultaneously, detached parietal proteins (PP1/PP2) induce occlusion of Sieve Plates and cover wound surface. If root pressure is strong enough, pure xylem sap can be collected after removal of the occlusion plug at the wound surface. The present findings provide a mechanism of sap exudation in Cucurbita maxima, in which the contribution of xylem water is integrated.
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Sieve element ca2 channels as relay stations between remote stimuli and Sieve tube occlusion in vicia faba
The Plant Cell, 2009Co-Authors: Alexandra C U Furch, Aart J. E. Van Bel, Mark D Fricker, Hubert H Felle, Maike Fuchs, Jens B HafkeAbstract:Damage induces remote occlusion of Sieve tubes in Vicia faba by forisome dispersion, triggered during the passage of an electropotential wave (EPW). This study addresses the role of Ca2+ channels and cytosolic Ca2+ elevation as a link between EPWs and forisome dispersion. Ca2+ channel antagonists affect the initial phase of the EPW as well as the prolonged plateau phase. Resting levels of Sieve tube Ca2+ of ∼50 nM were independently estimated using Ca2+-selective electrodes and a Ca2+-sensitive dye. Transient changes in cytosolic Ca2+ were observed in phloem tissue in response to remote stimuli and showed profiles similar to those of EPWs. The measured elevation of Ca2+ in Sieve tubes was below the threshold necessary for forisome dispersion. Therefore, forisomes need to be associated with Ca2+ release sites. We found an association between forisomes and endoplasmic reticulum (ER) at Sieve Plates and pore-plasmodesma units where high-affinity binding of a fluorescent Ca2+ channel blocker mapped an increased density of Ca2+ channels. In conclusion, propagation of EPWs in response to remote stimuli is linked to forisome dispersion through transiently high levels of parietal Ca2+, release of which depends on both plasma membrane and ER Ca2+ channels.
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Sieve element Ca2+ channels as relay stations between remote stimuli and Sieve tube occlusion in Vicia faba.
'American Society of Plant Biologists (ASPB)', 2009Co-Authors: Alexandra C U Furch, Hubert H Felle, Aj ,van Bel, Fuchs M, Jens B HafkeAbstract:Damage induces remote occlusion of Sieve tubes in Vicia faba by forisome dispersion, triggered during the passage of an electropotential wave (EPW). This study addresses the role of Ca2+ channels and cytosolic Ca2+ elevation as a link between EPWs and forisome dispersion. Ca2+ channel antagonists affect the initial phase of the EPW as well as the prolonged plateau phase. Resting levels of Sieve tube Ca2+ of approximately 50 nM were independently estimated using Ca2+-selective electrodes and a Ca2+-sensitive dye. Transient changes in cytosolic Ca2+ were observed in phloem tissue in response to remote stimuli and showed profiles similar to those of EPWs. The measured elevation of Ca2+ in Sieve tubes was below the threshold necessary for forisome dispersion. Therefore, forisomes need to be associated with Ca2+ release sites. We found an association between forisomes and endoplasmic reticulum (ER) at Sieve Plates and pore-plasmodesma units where high-affinity binding of a fluorescent Ca2+ channel blocker mapped an increased density of Ca2+ channels. In conclusion, propagation of EPWs in response to remote stimuli is linked to forisome dispersion through transiently high levels of parietal Ca2+, release of which depends on both plasma membrane and ER Ca2+ channels