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Osmotically evoked shrinking of guard-cell protoplasts causes vesicular retrieval of plasma membrane into the cytoplasm.

Kubitscheck, U. and Homann, Ulrike and Thiel, Gerhard (2000):
Osmotically evoked shrinking of guard-cell protoplasts causes vesicular retrieval of plasma membrane into the cytoplasm.
In: Planta, pp. 423-31, 210, (3), ISSN 0032-0935, [Article]

Abstract

The dye FM1-43 was used alone or in combination with measurements of the membrane capacitance (Cm) to monitor membrane changes in protoplasts from Vicia faba L. guard cells. Confocal images of protoplasts incubated with FM1-43 (10 microM) at constant ambient osmotic pressure (pi omicron) revealed in confocal images a slow internalisation of FM1-43-labelled membrane into the cytoplasm. As a result of this process the relative fluorescence intensity of the cell interior (fFM,i) increased with reference to the total fluorescence (fFM,t) by 7.4 x 10(-4) min(-1). This steady internalisation of dye suggests the occurrence of constitutive endocytosis under constant osmotic pressure. Steady internalisation of FM1-43 labelled membrane caused a prominent staining of a ring-like structure located beneath the plasma membrane. Abrupt elevation of pi omicron by 200 mosmol kg(-1) caused, over the first minutes of incubation, a rapid internalisation of FM1-43 fluorescence into the cytoplasm concomitant with a decrease in cell perimeter. Within the first 5 min the cell perimeter decreased by 7.9%. Over the same time fFM,i/fFM,t increased by 0.13, reflecting internalisation of fluorescent label into the cytoplasm. Combined measurements of Cm and total fluorescence of a protoplast (fFM,p) showed that an increase in pi omicron evoked a decrease in Cm but no change in fFM,p. This means that surface contraction of the protoplast is due to retrieval of excess membrane from the plasma membrane and internalisation into the cytoplasm. Further inspection of confocal images revealed that protoplast shrinking was only occasionally associated with internalisation of giant vesicles (median diameter 2.7 microm) with FM 1-43-labelled membrane. But, in all cases, osmotic contraction was correlated with a diffuse distribution of FM1-43 label throughout the cytoplasm. From this, we conclude that endocytosis of small vesicles into the cytoplasm is the obligatory process by which cells accommodate an osmotically driven decrease in membrane surface area.

Item Type: Article
Erschienen: 2000
Creators: Kubitscheck, U. and Homann, Ulrike and Thiel, Gerhard
Title: Osmotically evoked shrinking of guard-cell protoplasts causes vesicular retrieval of plasma membrane into the cytoplasm.
Language: English
Abstract:

The dye FM1-43 was used alone or in combination with measurements of the membrane capacitance (Cm) to monitor membrane changes in protoplasts from Vicia faba L. guard cells. Confocal images of protoplasts incubated with FM1-43 (10 microM) at constant ambient osmotic pressure (pi omicron) revealed in confocal images a slow internalisation of FM1-43-labelled membrane into the cytoplasm. As a result of this process the relative fluorescence intensity of the cell interior (fFM,i) increased with reference to the total fluorescence (fFM,t) by 7.4 x 10(-4) min(-1). This steady internalisation of dye suggests the occurrence of constitutive endocytosis under constant osmotic pressure. Steady internalisation of FM1-43 labelled membrane caused a prominent staining of a ring-like structure located beneath the plasma membrane. Abrupt elevation of pi omicron by 200 mosmol kg(-1) caused, over the first minutes of incubation, a rapid internalisation of FM1-43 fluorescence into the cytoplasm concomitant with a decrease in cell perimeter. Within the first 5 min the cell perimeter decreased by 7.9%. Over the same time fFM,i/fFM,t increased by 0.13, reflecting internalisation of fluorescent label into the cytoplasm. Combined measurements of Cm and total fluorescence of a protoplast (fFM,p) showed that an increase in pi omicron evoked a decrease in Cm but no change in fFM,p. This means that surface contraction of the protoplast is due to retrieval of excess membrane from the plasma membrane and internalisation into the cytoplasm. Further inspection of confocal images revealed that protoplast shrinking was only occasionally associated with internalisation of giant vesicles (median diameter 2.7 microm) with FM 1-43-labelled membrane. But, in all cases, osmotic contraction was correlated with a diffuse distribution of FM1-43 label throughout the cytoplasm. From this, we conclude that endocytosis of small vesicles into the cytoplasm is the obligatory process by which cells accommodate an osmotically driven decrease in membrane surface area.

Journal or Publication Title: Planta
Volume: 210
Number: 3
Divisions: 10 Department of Biology
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10 Department of Biology > Plant Membrane Biophysics
10 Department of Biology > Plant Cell Biology
Date Deposited: 22 Jun 2011 07:38
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