Miedema Henk, Demidchik Vadim, Véry Anne-Aliénor, Bothwell John H F, Brownlee Colin, Davies Julia M
Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
Marine Biological Association, Citadel Hill, Plymouth PL1 2PB, UK.
New Phytol. 2008 Jul;179(2):378-385. doi: 10.1111/j.1469-8137.2008.02465.x.
Calcium (Ca2+)-permeable plasma membrane ion channels are critical to root hair elongation and signalling. Arabidopsis thaliana root hair plasma membrane contains a hyperpolarization-activated Ca2+ channel (HACC) conductance. Here, the co-residence of HACC with a depolarization-activated Ca2+ channel (DACC) conductance has been investigated. Whole-cell patch-clamping of apical plasma membrane has been used to study Ca2+ conductances and reveal the negative slope conductance typical of DACCs. Specific voltage protocols, Ba(2+)-permeation and inhibition by the cation channel blocker Gd3+ have been used to identify the DACC conductance. The Gd3+ sensitive DACC conductance was identified in only a minority of cells. DACC activity was quickly masked by the development of the HACC conductance. However, in the period between the disappearance of the negative slope conductance and the predominance of HACC, DACC activity could still be detected. A DACC conductance coexists with HACC in the root hair apical plasma membrane and could provide Ca2+ influx over a wide voltage range, consistent with a role in signalling.
钙离子（Ca2+）通透的质膜离子通道对根毛伸长和信号传导至关重要。拟南芥根毛质膜含有一种超极化激活的Ca2+通道（HACC）电导。在此，研究了HACC与去极化激活的Ca2+通道（DACC）电导的共定位情况。利用根尖质膜的全细胞膜片钳技术研究Ca2+电导，并揭示DACC典型的负斜率电导。采用特定的电压方案、Ba(2+)通透以及阳离子通道阻滞剂Gd3+的抑制作用来鉴定DACC电导。仅在少数细胞中鉴定出对Gd3+敏感的DACC电导。DACC活性很快被HACC电导的发展所掩盖。然而，在负斜率电导消失与HACC占主导之间的时间段内，仍可检测到DACC活性。DACC电导与HACC在根毛根尖质膜中共存，并可在较宽的电压范围内提供Ca2+内流，这与信号传导中的作用一致。
