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Excretion and folding of plasmalemma function to accommodate alterations in guard cell volume during stomatal closure in Vicia faba L.

Li B, Liu G, Deng Y, Xie M, Feng Z, Sun M, Zhao Y, Liang L, Ding N, Jia W - J. Exp. Bot. (2010)

Bottom Line: Stomatal movement results in large and repetitive changes in cell volume and consequently surface area.Additionally, an unknown structure was found at the interface between the plasmalemma and cell walls, especially in those areas of the cell where extensive folding occurred, suggesting that plasmalemma turnover is possibly associated with an interaction between the plasmalemma and cell walls.Collectively, the results strongly indicate that excretion and folding of the plasmalemma are critical for the accommodation of the cell volume alterations during stomatal movement.

View Article: PubMed Central - PubMed

Affiliation: College of Agronomy and Biotechnology, China Agricultural University, Beijing, China.

ABSTRACT
Stomatal movement results in large and repetitive changes in cell volume and consequently surface area. While endocytosis has been extensively studied and is thought to be a major mechanism for accommodating the volume changes as evidenced mainly by fluorescent labelling and confocal imaging, studies at the ultrastructural level in intact guard cells of stomata regulated by natural factors have never been reported. Here, it is reported that excretion and folding of the plasmalemma are critical for accommodating the volume alterations in intact guard cells in Vicia faba L. Using transmission electron microscopy in combination with laser confocal microscopy, it was observed that in fully opened stomata the plasmalemma was smooth and tightly adhered to the cell walls while a whole large vacuole appeared in the cell. In the closed stomata, besides vacuole fragmentation, endocytosis of the tonoplast rather than the plasmalemma commonly occurred. Importantly, in stomata where pore closure was induced by circadian rhythm or CO(2), numerous tiny vesicles were found outside the plasmalemma and, moreover, extensive folding of the plasmalemma could also be found in some regions of the cells. Additionally, an unknown structure was found at the interface between the plasmalemma and cell walls, especially in those areas of the cell where extensive folding occurred, suggesting that plasmalemma turnover is possibly associated with an interaction between the plasmalemma and cell walls. Collectively, the results strongly indicate that excretion and folding of the plasmalemma are critical for the accommodation of the cell volume alterations during stomatal movement.

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Related in: MedlinePlus

Confocal images of successive sections of stomata labelled by FM1-43. Guard cell pairs of stomata were labelled by FM1-43 and the imaging was performed as described in the Materials and methods. (A–E) Successive sections. Only ventral plasmalemma is clearly labelled. Note that many brightly labelled tiny spots appear in the plasmalemma in D and E.
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fig5: Confocal images of successive sections of stomata labelled by FM1-43. Guard cell pairs of stomata were labelled by FM1-43 and the imaging was performed as described in the Materials and methods. (A–E) Successive sections. Only ventral plasmalemma is clearly labelled. Note that many brightly labelled tiny spots appear in the plasmalemma in D and E.

Mentions: The osmiophilic bodies, as observed by electron microscopy (Figs 1–3), have never been described before in guard cells. In view of their possible roles in stomatal movement or membrane turnover, their possible chemical nature was characterized further. Guard cells contain numerous lipid bodies in the cytoplasm; based on their structural features, the osmiophilic bodies look somewhat like lipid bodies, although they are much smaller. To understand their chemical properties, guard cells were labelled with fluorescent styryl dye, and investigated with confocal microscopy. Consistent with the observations using electron microscopy, in fully opened stomata the FM1-43-labelled plasmalemma was quite smooth and taught (Fig. 4A). However, in the closed stomata, while no endocytotic vesicles were clearly observed, the labelled plasmalemma became thick and folded in the ventral areas, and, simultaneously, numerous masses of fluorescence appeared outside the plasmalemma (Fig. 4B), which strongly suggests that processes of membrane folding, extrusion, and excretion occurred. As shown in Fig. 4, in normal cases it was not possible to find any fluorescent labels for the osmiophilic bodies. However, when successive sections were examined, it was observed that some brightly labelled spots appeared in the plasmalemma, suggesting that the osmiophilic bodies can be labelled by FM1-43 (Fig. 5C, E). Because lipid bodies could not be labelled by styryl dyes (Meckel et al., 2004), these osmiophilic bodies cannot be lipid bodies, and they are more likely to contain materials with similar properties to plasmalemma.


Excretion and folding of plasmalemma function to accommodate alterations in guard cell volume during stomatal closure in Vicia faba L.

Li B, Liu G, Deng Y, Xie M, Feng Z, Sun M, Zhao Y, Liang L, Ding N, Jia W - J. Exp. Bot. (2010)

Confocal images of successive sections of stomata labelled by FM1-43. Guard cell pairs of stomata were labelled by FM1-43 and the imaging was performed as described in the Materials and methods. (A–E) Successive sections. Only ventral plasmalemma is clearly labelled. Note that many brightly labelled tiny spots appear in the plasmalemma in D and E.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2921211&req=5

fig5: Confocal images of successive sections of stomata labelled by FM1-43. Guard cell pairs of stomata were labelled by FM1-43 and the imaging was performed as described in the Materials and methods. (A–E) Successive sections. Only ventral plasmalemma is clearly labelled. Note that many brightly labelled tiny spots appear in the plasmalemma in D and E.
Mentions: The osmiophilic bodies, as observed by electron microscopy (Figs 1–3), have never been described before in guard cells. In view of their possible roles in stomatal movement or membrane turnover, their possible chemical nature was characterized further. Guard cells contain numerous lipid bodies in the cytoplasm; based on their structural features, the osmiophilic bodies look somewhat like lipid bodies, although they are much smaller. To understand their chemical properties, guard cells were labelled with fluorescent styryl dye, and investigated with confocal microscopy. Consistent with the observations using electron microscopy, in fully opened stomata the FM1-43-labelled plasmalemma was quite smooth and taught (Fig. 4A). However, in the closed stomata, while no endocytotic vesicles were clearly observed, the labelled plasmalemma became thick and folded in the ventral areas, and, simultaneously, numerous masses of fluorescence appeared outside the plasmalemma (Fig. 4B), which strongly suggests that processes of membrane folding, extrusion, and excretion occurred. As shown in Fig. 4, in normal cases it was not possible to find any fluorescent labels for the osmiophilic bodies. However, when successive sections were examined, it was observed that some brightly labelled spots appeared in the plasmalemma, suggesting that the osmiophilic bodies can be labelled by FM1-43 (Fig. 5C, E). Because lipid bodies could not be labelled by styryl dyes (Meckel et al., 2004), these osmiophilic bodies cannot be lipid bodies, and they are more likely to contain materials with similar properties to plasmalemma.

Bottom Line: Stomatal movement results in large and repetitive changes in cell volume and consequently surface area.Additionally, an unknown structure was found at the interface between the plasmalemma and cell walls, especially in those areas of the cell where extensive folding occurred, suggesting that plasmalemma turnover is possibly associated with an interaction between the plasmalemma and cell walls.Collectively, the results strongly indicate that excretion and folding of the plasmalemma are critical for the accommodation of the cell volume alterations during stomatal movement.

View Article: PubMed Central - PubMed

Affiliation: College of Agronomy and Biotechnology, China Agricultural University, Beijing, China.

ABSTRACT
Stomatal movement results in large and repetitive changes in cell volume and consequently surface area. While endocytosis has been extensively studied and is thought to be a major mechanism for accommodating the volume changes as evidenced mainly by fluorescent labelling and confocal imaging, studies at the ultrastructural level in intact guard cells of stomata regulated by natural factors have never been reported. Here, it is reported that excretion and folding of the plasmalemma are critical for accommodating the volume alterations in intact guard cells in Vicia faba L. Using transmission electron microscopy in combination with laser confocal microscopy, it was observed that in fully opened stomata the plasmalemma was smooth and tightly adhered to the cell walls while a whole large vacuole appeared in the cell. In the closed stomata, besides vacuole fragmentation, endocytosis of the tonoplast rather than the plasmalemma commonly occurred. Importantly, in stomata where pore closure was induced by circadian rhythm or CO(2), numerous tiny vesicles were found outside the plasmalemma and, moreover, extensive folding of the plasmalemma could also be found in some regions of the cells. Additionally, an unknown structure was found at the interface between the plasmalemma and cell walls, especially in those areas of the cell where extensive folding occurred, suggesting that plasmalemma turnover is possibly associated with an interaction between the plasmalemma and cell walls. Collectively, the results strongly indicate that excretion and folding of the plasmalemma are critical for the accommodation of the cell volume alterations during stomatal movement.

Show MeSH
Related in: MedlinePlus