Mechano‐perception in <i>Chara</i> cells: the influence of salinity and calcium on touch‐activated receptor potentials, action potentials and ion transport

Shepherd, Virginia A.; Beilby, Mary J.; Khazaaly, Sabah Al; Shimmen, Teruo

doi:10.1111/j.1365-3040.2008.01866.x

Cited by 45 publications

(47 citation statements)

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“…reached certain level of depolarization after application of those compounds. As proposed by V. Sheperd and colleagues [18], this repetitive firing resembles the onset of a critical instability where a time-ordered structure (repetitive firing) emerged after ramping currents to the excitation threshold. Namely, increased background conductance combined with loss of proton pump activity caused gradual depolarization of cell membrane potential to AP threshold.…”

Section: The Effect Of Acetylcholine On Single Action Potentialmentioning

confidence: 90%

The combined effect of Cd2+ and ACh on action potentials of Nitellopsis obtusa cells

et al. 2009

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Abstract:Interrelations between the action of acetylcholine (ACh) and cadmium ions (Cd 2+ ) on bioelectrogenesis of Nitellopsis obtusa cells were investigated. We analyzed repetitively triggered action potentials (AP), their reproducibility, shape and dynamics of membrane potential after AP induction. ACh significantly increased membrane permeability only at high concentrations (1 mM and 5 mM). Repolarisation level of action potential after the first stimulus was much more positive in all cells treated with ACh as compared to the control. Differences of membrane potentials between points just before the first and the second stimuli were 23.4±.0 mV (control); 40.4±5.9 mV (1 mM ACh solution) and 57.7 ± 8.5 mV (5 mM ACh solution). Cd 2+ at 20 μM concentration was examined as a possible inhibitor of acetylcholinesterase (AChE) in vivo. We found that cadmium strengthens depolarizing effect of acetylcholine after the first stimulus. The highest velocity of AP repolarization was reduced after ACh application and Cd 2+ strengthened this effect. There were no differences in dynamics of membrane potential after repetitively triggered action potentials in ACh or ACh and Cd 2+ solutions. This shows that cadmium in small concentration acts as inhibitor of acetylcholinesterase.

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Section: The Effect Of Acetylcholine On Single Action Potentialmentioning

confidence: 90%

The combined effect of Cd2+ and ACh on action potentials of Nitellopsis obtusa cells

et al. 2009

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“…In plasmolysed cells, the membrane loses connection with the cell wall and this might explain the lack of sensitivity. Shepherd et al (2002Shepherd et al ( , 2008 speculated that reduced turgor (before plasmolysis) and greater sensitivity to stimulation is part of a defensive mechanism that isolates injured cells from the rest of the plant. This is discussed in greater detail in Sect.…”

Section: Ea Eb Ec a B Cmentioning

confidence: 99%

“…The authors also tracked the movement of the stimulator and found "surface relaxation" following the strike or its withdrawal. (Shimmen 1997b Shepherd et al (2001) investigated the effect of decreased turgor on both RPDs and mechanically induced APs. The turgor covered the range from 0.6 MPa to 0.24 MPa.…”

Section: Ea Eb Ec a B Cmentioning

confidence: 99%

“…3.3.3. Shepherd et al (2008) compared the response to mechanical stimulation in cells exposed to 100 mM NaCl APW with either 0.1 mM Ca 2+ or 1.0 mM Ca 2+ to controls in APW and 180 mM sorbitol APW. The effect of the Ca ++ concentration was included, because increased Ca 2+ /Na + ratio reduces the impact of salinity in land plants (Cramer 2002) and Characeae (Whittington and Smith 1992).…”

Section: Ea Eb Ec a B Cmentioning

confidence: 99%

“…These experiments suggest that lowering cell turgor increases sensitivity to mechano-stimulation. Shepherd et al (2001) analysed the mechanical stimulation in terms of forces on the cell wall and adjacent plasma membrane. For the same force, the deformation in less turgid cells will be greater, activating more channels and increasing the RPD amplitude.…”

Section: Ea Eb Ec a B Cmentioning

confidence: 99%

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Electrophysiology of the Detached Cell Under Stress

Beilby

Casanova

2013

The Physiology of Characean Cells

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This chapter summarises the research on characean detached cells, subjected to calibrated and primarily abiotic types of stress. Responses to touch, wounding, voltage clamp to both depolarised and hyperpolarised potential difference (PD) levels and to osmotic and saline stress are described. Both salt-tolerant and saltsensitive Characeae have been investigated under osmotic and saline stress. Many of the cell responses involve an increase in cytoplasmic calcium concentration. However, the manner of calcium increase is specific to different stressors: mechanical stimulation opens stretch-activated (SA) channels on internal stores, depolarisation to excitation threshold opens IP 6 -activated channels on internal stores, hypo-osmotic stress opens SA channels on internal stores and possibly the vacuole, hyperpolarisation opens channels on the plasma membrane. The increase in the calcium concentration in the cytoplasm opens calcium-activated chloride channels on the plasma membrane (and possibly the tonoplast), leading to an outflow of chloride and depolarisation that can take a form of receptor potential (RPD), action potential (AP) or variation potential (VP). From all these responses, the AP fits the role of a signal: its form is relatively constant and it can propagate speedily from cell to cell. The responses to hyperosmotic and saline stress show interesting differences between salt-tolerant and salt-sensitive Characeae. In salt-tolerant Characeae, the proton pump is activated by both a decrease in turgor and an increase in salinity. The activation by turgor decrease is transient as turgor is regulated, while activation by salt is permanent and graded according to salt concentration. The turgor sensors may be located at the ends of nodal cells. In salt-sensitive Characeae, on the other hand, non-plasmolysing turgor decrease elicits no change in pump activity, while an increase in salinity shuts down the pump and opens H + /OH À channels, depolarising the membrane PD further. Spontaneous APs with long durations and opening of outward rectifying channels lead to a loss of potassium and death. Both salt-sensitive and salt-tolerant Characeae employ Na + /H + antiporter to remove Na + from the cytoplasmic compartment under saline stress and the water channels on the plasma membrane are closed by high osmolarity.

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Studying Plant Salt Tolerance with the Voltage Clamp Technique

Chen

Eisenach

et al. 2012

Methods in Molecular Biology

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Voltage clamp is one of the key techniques for the dissection, identification, and monitoring of ion transporters in plant cells. Voltage clamp-based research work on salinity stress in plants enables the characterization of many plant ATP-dependent pumps, ion channels, and ion-coupled carriers through heterologous expression in Xenopus laevis oocytes and in vivo measurements in salt-tolerant and salt-sensitive giant green algae such as Chara and many plant species. We have modified and developed a reliable set of procedures for voltage clamp analysis in intact guard cells and root epidermal cells from Arabidopsis thaliana with potentially broad applications in the salinity response of plants. These procedures greatly extend the duration of measurements and scope for analysis of the predominant K(+) and anion channels.

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Mechano‐perception in Chara cells: the influence of salinity and calcium on touch‐activated receptor potentials, action potentials and ion transport

Cited by 45 publications

References 77 publications

The combined effect of Cd2+ and ACh on action potentials of Nitellopsis obtusa cells

The combined effect of Cd2+ and ACh on action potentials of Nitellopsis obtusa cells

Electrophysiology of the Detached Cell Under Stress

Studying Plant Salt Tolerance with the Voltage Clamp Technique

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