Increased Expression of Vacuolar Aquaporin and H+-ATPase Related to Motor Cell Function in Mimosa pudica L

Fleurat‐Lessard, Pierrette; Frangne, Nathalie; Maeshima, Masayoshi; Ratajczak, Raphael; Bonnemain, Jean‐Louis; Martinoia, Enrico

doi:10.1104/pp.114.3.827

Cited by 118 publications

(102 citation statements)

References 27 publications

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“…In numerous cases, the degree of volume changes may even exceed those reported here. For example, in pulvinar motor cells of Mimosa pudica, the reported volume decreases were of about 25% (reversibility would then require a 30% volume increases; Fleurat-Lessard et al, 1997), and in guard cells volume changes were about 40% (Raschke and Dickerson, 1973;Franks et al, 2001). These changes can occur within seconds (cell shrinking in Mimosa) to tens of minutes (in guard cells or motor organs of other plants).…”

Section: Physiological Relevancementioning

confidence: 99%

Dynamic Changes in the Osmotic Water Permeability of Protoplast Plasma Membrane

2004

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The osmotic water permeability coefficient (P f ) of plasma membrane of maize (Zea mays) Black Mexican Sweet protoplasts changed dynamically during a hypoosmotic challenge, as revealed using a model-based computational approach. The bestfitting model had three free parameters: initial P f , P f rate-of-change (slope Pf ), and a delay, which were hypothesized to reflect changes in the number and/or activity of aquaporins in the plasma membrane. Remarkably, the swelling response was delayed 2 to 11 s after start of the noninstantaneous (but accounted for) bath flush. The P f during the delay was #1 mm s 21 . During the swelling period following the delay, P f changed dynamically: within the first 15 s P f either (1) increased gradually to approximately 8 mm s 21 (in the majority population of low-initial-P f cells) or (2) increased abruptly to 10 to 20 mm s 21 and then decreased gradually to 3 to 6 mm s 21 (in the minority population of high-initial-P f cells). We affirmed the validity of our computational approach by the ability to reproduce previously reported initial P f values (including the absence of delay) in control experiments on Xenopus oocytes expressing the maize aquaporin ZmPIP2;5. Although mercury did not affect the P f in swelling Black Mexican Sweet cells, phloretin, another aquaporin inhibitor, inhibited swelling in a predicted manner, prolonging the delay and slowing P f increase, thereby confirming the hypothesis that P f dynamics, delay included, reflected the varying activity of aquaporins.The regulation of plant aquaporins is becoming a focus of research in an increasing number of laboratories Tyerman et al., 2002). However, the reports on the regulation of the water permeability of plant cells are still relatively few, very likely reflecting the technical difficulties inherent in such measurements.In order to quantify the permeability of a plant cell to water, one of the approaches consists of isolating protoplasts and monitoring the initial rate of change of their volume upon an osmotic challenge. If the osmotic potential of the external solution is changed instantaneously, the osmotic water permeability (termed P f or P os ) can be deduced from the initial rate of volume relaxation (e.g. Zhang et al., 1990;Verkman, 2000). There are at least two problems with this approach: (1) even when an instantaneous change of solution is possible, a systematic error is introduced, causing an underestimate of P f because, already during the initial phase of protoplast swelling, the volume, the surface area, and the internal concentration of solutes do not remain constant; and (2) instantaneous bath perfusion has technical-and physiological-limitations: unlike animal cells, isolated plant cell protoplasts (the terms protoplast and cell will be used here interchangeably) do not stick well to the chamber floor and defeat attempts of rapid (let alone, instantaneous) solution flushes. Very fast external solution exchange has been achieved by immobilizing the protoplast with a suction micropipette (e.g. Ramah...

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Section: Physiological Relevancementioning

confidence: 99%

Dynamic Changes in the Osmotic Water Permeability of Protoplast Plasma Membrane

2004

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“…This rapid change can be accounted for by the shrinkage of tannin and colloidal vacuoles in the motor cells, which is caused by rapid loss of turgor pressure due to the efflux of K + and translocation of water. [1][2][3][4][5] The actin cytoskeleton is reported to be involved in the bending movement of Mimosa petioles. Treatment of the Mimosa motor organ with cytochalasin B (CB) and phalloidin, to interfere with the actin cytoskeleton, alters the ability of the main pulvinus to bend, which suggests that the rearrangement of actin is important for seismonastic movement.…”

Section: Introductionmentioning

confidence: 99%

Actin dynamics mediates the changes of calcium level during the pulvinus movement ofMimosa pudica

Yao¹,

Yuan³

2008

Plant Signaling & Behavior

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The bending movement of the pulvinus of Mimosa pudica is caused by a rapid change in volume of the abaxial motor cells, in response to various environmental stimuli. We investigated the relationship between the actin cytoskeleton and changes in the level of calcium during rapid contractile movement of the motor cells that was induced by electrical stimulation. The bending of the pulvinus was retarded by treatments with actin-affecting reagents and calcium channel inhibitors. The actin filaments in the motor cells were fragmented in response to electrical stimulation. Further investigations were performed using protoplasts from the motor cells of M. pudica pulvini. Calcium-channel inhibitors and EGTA had an inhibitory effect on contractile movement of the protoplasts. The level of calcium increased and became concentrated in the tannin vacuole after electrical stimulation. Ruthenium Red inhibited the increase in the level of calcium in the tannin vacuole and the contractile movement of the protoplasts. However, treatment with latrunculin A abolished the inhibitory effect of Ruthenium Red. Phalloidin inhibited the contractile movement and the increase in the level of calcium in the protoplasts. Our study demonstrates that depolymerization of the actin cytoskeleton in pulvinus motor cells in response to electrical signals results in increased levels of calcium.

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“…In the case of stomata, following Schroeder et al (1984) and Assmann et al (1985), we consider that for a spherical guard cell with initial radius R 0 ϭ 7 ϫ 10 Ϫ6 m, the flux of potassium ions responsible for stomatal movement is J s0 ϭ 2 ϫ 10 Ϫ7 mol m Ϫ2 s Ϫ1 . The osmolarity of the cell is not known, but even if we consider a cell with an osmolarity as low as 100 mOsmol, a significant change in V, for example 10%, could not occur in less than 100 s. In the case of M. pudica, the maximum currents measured on protoplasts from motor cells correspond to current densities that may be 10 times larger than those found in guard cells (Moran et al, 1990;Stoeckel and Takeda, 1995), but the volume of these cells decreases by up to 25% during leaflet closure (Fleurat-Lessard et al, 1997 However, according to the present data, a 10% volume change in a few seconds is difficult to explain by a fast uptake or release of K ϩ ions between the cell and its surroundings. We suggest another mechanism based on the hypothesis that molecular coupling between water and a solute species occurs in cellular membranes.…”

Section: Rt V Wmentioning

confidence: 99%

“…If water follows K ϩ flux by osmosis, then the rate of flux would determine the rate of volume change (Schroeder et al, 1984). This explanation is frequently used as a paradigm for other nyctinastic and seismonastic movements (Moran et al, 1990;Fleurat-Lessard et al, 1997;Moshelion and Moran, 2000). For example, in Mimosa pudica, the observed potassium exchanges and the nature of the anatomical structures of pulvinule and pulvinus have led to suggestions that movements are the result of modifications in the volume of motor cells at the base of each leaflet and leaf by a "lever" effect.…”

mentioning

confidence: 99%