Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Inward and outward K+-selective currents in the plasma membrane of protoplasts from maize root cortex and stele
AU - Roberts, Stephen K.
AU - Tester, Mark
PY - 1995/12
Y1 - 1995/12
N2 - In an attempt to understand the processes mediating ion transport within the root, the patch clamp technique was applied to protoplasts isolated from the cortex and stele of maize roots and their plasma membrane conductances investigated. In the whole-cell configuration, membrane hyperpolarization induced a slowly activating inwardly rectifying conductance in most protoplasts isolated from the root cortex. In contrast, most protoplasts isolated from the stele contained a slowly activating outwardly rectifying conductance upon plasma membrane depolarization. The reversal potential of the inward current indicated that it was primarily due to the movement of K+; the outwardly rectifying conductance was comparatively less selective for K+. Membrane hyperpolarization beyond a threshold of about -70 mV induced inward currents. When E(K) was set negative of this threshold, inward currents activated negative of E(K) and no outward currents were observed positive of E(K) Outward currents in the stelar protoplasts activated at potentials positive of -85 mV. However, when E(K) was set positive of -85 mV a small inward current was also observed at potentials negative (and slightly positive) of the equilibrium potential for Kf. Inwardly and outwardly rectifying Kf channels were observed in outside-out patches from the plasma membrane of cortical and stelar cells, respectively Characterization of these channels showed that they were likely to be responsible for the macroscopic 'whole-cell' currents. Inward and outward currents were affected differently by various Kt channel blockers (TEA(+), Ba2+ and Cs+). In addition, Ca2+ above 1 mM partially blocked the inward current in a voltage-dependent manner but had little effect on the outward current. It is suggested that the inwardly rectifying conductance identified in protoplasts isolated from the cortex probably represents an important component of the low-affinity K+ uptake mechanism (mechanism II) identified in intact roots. The outwardly rectifying conductance identified in protoplasts isolated from the stele could play a role in the release of cations into the xylem vessels for transport to the shoot.
AB - In an attempt to understand the processes mediating ion transport within the root, the patch clamp technique was applied to protoplasts isolated from the cortex and stele of maize roots and their plasma membrane conductances investigated. In the whole-cell configuration, membrane hyperpolarization induced a slowly activating inwardly rectifying conductance in most protoplasts isolated from the root cortex. In contrast, most protoplasts isolated from the stele contained a slowly activating outwardly rectifying conductance upon plasma membrane depolarization. The reversal potential of the inward current indicated that it was primarily due to the movement of K+; the outwardly rectifying conductance was comparatively less selective for K+. Membrane hyperpolarization beyond a threshold of about -70 mV induced inward currents. When E(K) was set negative of this threshold, inward currents activated negative of E(K) and no outward currents were observed positive of E(K) Outward currents in the stelar protoplasts activated at potentials positive of -85 mV. However, when E(K) was set positive of -85 mV a small inward current was also observed at potentials negative (and slightly positive) of the equilibrium potential for Kf. Inwardly and outwardly rectifying Kf channels were observed in outside-out patches from the plasma membrane of cortical and stelar cells, respectively Characterization of these channels showed that they were likely to be responsible for the macroscopic 'whole-cell' currents. Inward and outward currents were affected differently by various Kt channel blockers (TEA(+), Ba2+ and Cs+). In addition, Ca2+ above 1 mM partially blocked the inward current in a voltage-dependent manner but had little effect on the outward current. It is suggested that the inwardly rectifying conductance identified in protoplasts isolated from the cortex probably represents an important component of the low-affinity K+ uptake mechanism (mechanism II) identified in intact roots. The outwardly rectifying conductance identified in protoplasts isolated from the stele could play a role in the release of cations into the xylem vessels for transport to the shoot.
KW - CELL-SUSPENSION CULTURES
KW - PATCH CLAMP EXPERIMENTS
KW - GUARD-CELLS
KW - POTASSIUM-TRANSPORT
KW - WHOLE-CELL
KW - VICIA-FABA
KW - ION CHANNELS
KW - CORN ROOTS
KW - DEPENDENCE
KW - VOLTAGE
U2 - 10.1046/j.1365-313X.1995.8060811.x
DO - 10.1046/j.1365-313X.1995.8060811.x
M3 - Journal article
VL - 8
SP - 811
EP - 825
JO - Plant Journal
JF - Plant Journal
SN - 0960-7412
IS - 6
ER -