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Gating of water channels (aquaporins) in cortical cells of young corn roots by mechanical stimuli (pressure pulses): effects of ABA and of HgCl₂

Title data

Wan, Xianchong ; Steudle, Ernst ; Hartung, Wolfram:
Gating of water channels (aquaporins) in cortical cells of young corn roots by mechanical stimuli (pressure pulses): effects of ABA and of HgCl₂.
In: Journal of Experimental Botany. Vol. 55 (2004) Issue 396 . - pp. 411-422.
ISSN 1460-2431
DOI: https://doi.org/10.1093/jxb/erh051

Abstract in another language

Hydraulic properties (half-time of water exchange, T-1/2, and hydraulic conductivity, Lp; T-1/2 similar to 1/Lp) of individual cells in the cortex of young corn roots were measured using a cell pressure probe for up to 6 h to avoid variations between cells. When pulses of turgor pressure of different size were imposed, T-1/2 (Lp) responded differently depending on the size. Pulses of smaller than 0.1 MPa, which induced a small proportional water flow, caused no changes in T-1/2 (Lp). Medium-sized pulses of between 0.1 and 0.2 MPa caused an increase in T-1/2 (decrease in Lp) by a factor of 4 to 23. The effects caused by medium-sized pulses were reversible within 5-20 min. When larger pulses of more than 0.2 MPa were employed, changes were not reversible within 1-3 h, but could be reversed within 30 min in the presence of 500 nM of the stress hormone ABA. Cells with a short T-1/2 responded to the aquaporin blocker mercuric chloride (HgCl2). The treatment had no effect on cells which exhibited long T-1/2 following a mechanical inhibition by the large-pulse treatment. Step decreases in pressure resulted in the same inhibition as step increases. Hence, the treatment did not cause a stretch-inhibition of water channels and was independent of the directions of both pressure changes and water flows induced by them. It is concluded that inhibition is caused by the absolute value of intensities of water flow within the channels, which increased in proportion to the size of step changes in pressure. Probable mechanisms by which the mechanical stimuli are perceived are (i) the input of kinetic energy to the channel constriction (NPA motif of aquaporin) which may cause a conformational change of the channel protein (energy-input model) or (ii) the creation of tensions at the constriction analogous to Bernoulli's principle for macroscopic pores (cohesion-tension model). Estimated rates of water flow within the pores were a few hundred mum s(-1), which is too small to create sufficient tension. They were much smaller than those proposed for AQP1. Based on literature data of single-channel permeability of AQP1, a per channel energy input of 200 k(B)xT (k(B)=Boltzmann constant) was estimated for the energy-input model. This should be sufficient to initiate changes of protein conformation and an inactivation of channels. The data indicate different closed states which differ in the amount of distortion and the rates at which they relax back to the open state.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER33596
Institutions of the University: Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Biology > Chair Plant Ecology
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Biology
Research Institutions
Research Institutions > Research Centres
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 11 Sep 2015 06:34
Last Modified: 11 Sep 2015 06:34
URI: https://eref.uni-bayreuth.de/id/eprint/19253