|
|
||||||||
|
Plant Physiology Preview Published on June 23, 2006; 10.1104/pp.106.082388
Received April 19, 2006 Extracellular Ca2+ ameliorates NaCl-induced K+ loss from Arabidopsis root and leaf cells by controlling plasma membrane K+-permeable channels
School of Agricultural Sciences, University of Tasmania, Hobart, Tasmania 7001, Australia * Corresponding author; email: Sergey.Shabala{at}utas.edu.au.
Calcium can ameliorate Na+ toxicity in plants by decreasing Na+ influx through non-selective cation channels (NSCC). Here, we show that elevated external [Ca2+] also inhibits Na+-induced K+ efflux through outwardly directed K+-permeable channels. MIFE and patch clamp techniques were used to characterise K+ fluxes from Arabidopsis root mature epidermis and leaf mesophyll under various Ca2+/Na+ ratios. NaCl-induced K+ efflux was not related to the osmotic component of the salt stress, it was inhibited by the K+ channel blocker TEA+, not mediated by inwardly directed K+ channels (tested in the akt1 mutant), and resulted in a significant decrease in cytosolic K+ content. NaCl-induced K+ efflux was partially inhibited by 1 mM Ca2+ and fully prevented by 10 mM Ca2+. This ameliorative effect was at least partially attributed to a less dramatic NaCl-induced membrane depolarisation under high Ca2+ conditions. Patch clamp experiments (whole-cell mode) have demonstrated that two populations of Ca2+-sensitive K+ efflux channels exist in protoplasts isolated from the mature epidermis of Arabidopsis root and leaf mesophyll cells. The instantaneously activating K+ efflux channels showed weak voltage-dependence and insensitivity to external and internal Na+. Another population of K+ efflux channels was slowly activating, steeply rectifying and highly sensitive to Na+. K+ efflux channels in roots and leaves showed different Ca2+ and Na+ sensitivities, suggesting that these organs may employ different strategies to withstand salinity. Our results suggest a new mechanism of Ca2+ action on salt toxicity in plants - the amelioration of K+ loss from the cell - by regulating (both directly and indirectly) K+ efflux channels.
This article has been cited by other articles:
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
| ASPB Publications | PLANT PHYSIOLOGY | THE PLANT CELL | |
|---|---|---|---|