Potassium uptake bg higher plants is the result of high- or low-affinity transport accomplished by different sets of transporters. Although K+ channels were thought to mediate low-affinity uptake only, the molecular mechanism of the high-affinity, proton dependent K+ uptake system is still scant. Taking advantage of the high current resolution of the patch-clamp technique when applied to the small Arabidopsis thaliana guard cells densely packed with voltage-dependent K+ channels, we could directly record channels working in the concentration range of high-affinity K+ uptake systems. Here we show that the K+ channel KAT1 expressed in Arabidopsis guard cells and yeast is capable of mediating potassium uptake from media containing as little as 10 mu M of external K+, Upon reduction of the external K+ content to the micromolar level the voltage dependence of the channel remained unaffected, indicating that this channel type represents a voltage sensor rather than a kif-sensing valve. This behavior results in K+ release through K+ uptake channels whenever the Nernst potential is negative to the activation threshold of the channel. In contrast to the H+-coupled K+ symport shown to account for high-affinity K+ uptake in roots, pH-dependent K+ uptake into guard cells is a result of a shift in the voltage dependence of the K+ channel. We conclude that plant K+ channels activated by acid pH may play an essential role in K+ uptake even from dilute solutions.
%0 Journal Article
%1 RN1234
%A Brüggemann, L.
%A Dietrich, P.
%A Becker, D.
%A Dreyer, I.
%A Palme, K.
%A Hedrich, R.
%D 1999
%J Proceedings of the National Academy of Sciences of the United States of America
%K myOwn potassium uptake
%N 6
%P 3298-3302
%R DOI 10.1073/pnas.96.6.3298
%T Channel-mediated high-affinity K
uptake into guard cells from
%U /brokenurl#<Go to ISI>://WOS:000079224500132
%V 96
%X Potassium uptake bg higher plants is the result of high- or low-affinity transport accomplished by different sets of transporters. Although K+ channels were thought to mediate low-affinity uptake only, the molecular mechanism of the high-affinity, proton dependent K+ uptake system is still scant. Taking advantage of the high current resolution of the patch-clamp technique when applied to the small Arabidopsis thaliana guard cells densely packed with voltage-dependent K+ channels, we could directly record channels working in the concentration range of high-affinity K+ uptake systems. Here we show that the K+ channel KAT1 expressed in Arabidopsis guard cells and yeast is capable of mediating potassium uptake from media containing as little as 10 mu M of external K+, Upon reduction of the external K+ content to the micromolar level the voltage dependence of the channel remained unaffected, indicating that this channel type represents a voltage sensor rather than a kif-sensing valve. This behavior results in K+ release through K+ uptake channels whenever the Nernst potential is negative to the activation threshold of the channel. In contrast to the H+-coupled K+ symport shown to account for high-affinity K+ uptake in roots, pH-dependent K+ uptake into guard cells is a result of a shift in the voltage dependence of the K+ channel. We conclude that plant K+ channels activated by acid pH may play an essential role in K+ uptake even from dilute solutions.
@article{RN1234,
abstract = {Potassium uptake bg higher plants is the result of high- or low-affinity transport accomplished by different sets of transporters. Although K+ channels were thought to mediate low-affinity uptake only, the molecular mechanism of the high-affinity, proton dependent K+ uptake system is still scant. Taking advantage of the high current resolution of the patch-clamp technique when applied to the small Arabidopsis thaliana guard cells densely packed with voltage-dependent K+ channels, we could directly record channels working in the concentration range of high-affinity K+ uptake systems. Here we show that the K+ channel KAT1 expressed in Arabidopsis guard cells and yeast is capable of mediating potassium uptake from media containing as little as 10 mu M of external K+, Upon reduction of the external K+ content to the micromolar level the voltage dependence of the channel remained unaffected, indicating that this channel type represents a voltage sensor rather than a kif-sensing valve. This behavior results in K+ release through K+ uptake channels whenever the Nernst potential is negative to the activation threshold of the channel. In contrast to the H+-coupled K+ symport shown to account for high-affinity K+ uptake in roots, pH-dependent K+ uptake into guard cells is a result of a shift in the voltage dependence of the K+ channel. We conclude that plant K+ channels activated by acid pH may play an essential role in K+ uptake even from dilute solutions.},
added-at = {2024-02-14T14:38:32.000+0100},
author = {Brüggemann, L. and Dietrich, P. and Becker, D. and Dreyer, I. and Palme, K. and Hedrich, R.},
biburl = {https://www.bibsonomy.org/bibtex/2f790a320977a517a1a309143878abf95/rainerhedrich_2},
doi = {DOI 10.1073/pnas.96.6.3298},
interhash = {849f6f7a1e50285e1bc9b0b6bf6d41ba},
intrahash = {f790a320977a517a1a309143878abf95},
issn = {0027-8424},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
keywords = {myOwn potassium uptake},
note = {177rh
Times Cited:57
Cited References Count:34},
number = 6,
pages = {3298-3302},
timestamp = {2024-02-14T14:38:32.000+0100},
title = {Channel-mediated high-affinity K
uptake into guard cells from},
type = {Journal Article},
url = {/brokenurl#<Go to ISI>://WOS:000079224500132},
volume = 96,
year = 1999
}