title: Two voltage-dependent calcium channels co-exist in the apical plasma membrane of Arabidopsis thaliana root hairs.
abstract: 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.
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
authors.forename: Henk
authors.initials: H
authors.lastname: Miedema
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
authors.forename: Vadim
authors.initials: V
authors.lastname: Demidchik
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
authors.forename: Anne-Aliénor
authors.initials: AA
authors.lastname: Véry
authors.affiliation: Marine Biological Association, Citadel Hill, Plymouth PL1 2PB, UK.
authors.forename: John H F
authors.initials: JHF
authors.lastname: Bothwell
authors.affiliation: Marine Biological Association, Citadel Hill, Plymouth PL1 2PB, UK.
authors.forename: Colin
authors.initials: C
authors.lastname: Brownlee
authors.affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
authors.forename: Julia M
authors.initials: JM
authors.lastname: Davies
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D004594:Electrophysiology; D005682:Gadolinium; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D008564:Membrane Potentials; D018517:Plant Roots / Q000166:cytology* / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D005682:Gadolinium; D002118:Calcium