EurekaMag.com logo
+ Site Statistics
References:
53,623,987
Abstracts:
29,492,080
+ Search Articles
+ Subscribe to Site Feeds
EurekaMag Most Shared ContentMost Shared
EurekaMag PDF Full Text ContentPDF Full Text
+ PDF Full Text
Request PDF Full TextRequest PDF Full Text
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter
Follow on LinkedInFollow on LinkedIn

+ Translate

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



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



Journal of Experimental Botany 55(396): 411-422



Hydraulic properties (half-time of water exchange, T1/2, and hydraulic conductivity, Lp; T1/2 [similar] 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, T1/2 (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 T1/2 (Lp). Medium-sized pulses of between 0.1 and 0.2 MPa caused an increase in T1/2 (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 T1/2 responded to the aquaporin blocker mercuric chloride (HgCl2). The treatment had no effect on cells which exhibited long T1/2 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 mm 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 kB [times] T (kB=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. Reprinted by permission of the publisher.

(PDF same-day service: $19.90)

Accession: 004171815

Download citation: RISBibTeXText

PMID: 14739264

DOI: 10.1093/jxb/erh051



Related references

Gating of water channels in cortical cells of young corn roots by mechanical stimuli Effects of ABA and of HgCl2. Journal of Experimental Botany 55(396): 411-422, February, 2004

Oxidative gating of water channels (aquaporins) in corn roots. Plant, Cell and Environment 29(4): 459-470, 2006

Water permeability and reflection coefficient of the outer part of young rice roots are differently affected by closure of water channels (aquaporins) or blockage of apoplastic pores. Journal of Experimental Botany 55(396): 433-447, 2004

Oxidative gating of water channels (aquaporins) in Chara by hydroxyl radicals. Plant Cell and Environment 27(9): 1184-1195, 2004

A cohesion/tension mechanism explains the gating of water channels (aquaporins) in Chara internodes by high concentration. Journal of Experimental Botany 55(396): 449-461, 2004

Hydraulic conductivity and aquaporins of cortical cells in gravitropically bending roots of Pisum sativum L. Plant Production Science 8(5): 515-524, 2005

HgCl2, an inhibitor of aquaporins, enhances root water-pumping activity. Doklady Biological Sciences 421: 262-265, 2008

Transient variations of water transfer induced by HgCl2 in excised roots of young maize plants: New data on the inhibition process. Australian Journal of Plant Physiology 28(12): 1175-1186, 2001

Inhibition of water channels by HgCl2 in intact wheat root cells. Plant Physiology 120(3): 849-858, 1999

Effects of water storage in the stele on measurements of the hydraulics of young roots of corn and barley. New Phytologist 184(3): 631-643, 2010

Different blocking effects of HgCl2 and NaCl on aquaporins of pepper plants. Journal of Plant Physiology 160(12): 1487-1492, 2004

Differential sensitivities of water diffusion in maize root cortex and stele to HgCl2-induced blockade of aquaporins. Russian Journal Of Plant Physiology: 3, 328-332, 2008

Mechanical gating of transduction channels in otic hair cells. Biophysical Journalpart 2: 411a, 1988

Low temperature and mechanical stresses differently gate aquaporins of root cortical cells of chilling-sensitive cucumber and -resistant figleaf gourd. Plant cell and environment 28(9): 1191-1202, 2005