title: Genes for calcium-permeable channels in the plasma membrane of plant root cells.
abstract: In plant cells, Ca(2+) is required for both structural and biophysical roles. In addition, changes in cytosolic Ca(2+) concentration ([Ca(2+)](cyt)) orchestrate responses to developmental and environmental signals. In many instances, [Ca(2+)](cyt) is increased by Ca(2+) influx across the plasma membrane through ion channels. Although the electrophysiological and biochemical characteristics of Ca(2+)-permeable channels in the plasma membrane of plant cells are well known, genes encoding putative Ca(2+)-permeable channels have only recently been identified. By comparing the tissue expression patterns and electrophysiology of Ca(2+)-permeable channels in the plasma membrane of root cells with those of genes encoding candidate plasma membrane Ca(2+) channels, the genetic counterparts of specific Ca(2+)-permeable channels can be deduced. Sequence homologies and the physiology of transgenic antisense plants suggest that the Arabidopsis AtTPC1 gene encodes a depolarisation-activated Ca(2+) channel. Members of the annexin gene family are likely to encode hyperpolarisation-activated Ca(2+) channels, based on their corresponding occurrence in secretory or elongating root cells, their inhibition by La(3+) and nifedipine, and their increased activity as [Ca(2+)](cyt) is raised. Based on their electrophysiology and tissue expression patterns, AtSKOR encodes a depolarisation-activated outward-rectifying (Ca(2+)-permeable) K(+) channel (KORC) in stelar cells and AtGORK is likely to encode a KORC in the plasma membrane of other Arabidopsis root cells. Two candidate gene families, of cyclic-nucleotide gated channels (CNGC) and ionotropic glutamate receptor (GLR) homologues, are proposed as the genetic correlates of voltage-independent cation (VIC) channels.
authors.affiliation: Department of Plant Genetics and Biotechnology, Horticulture Research International, Wellesbourne, CV35 9EF, Warwick, UK. philip-j.white@hri.ac.uk
authors.forename: Philip J
authors.initials: PJ
authors.lastname: White
authors.forename: Helen C
authors.initials: HC
authors.lastname: Bowen
authors.forename: Vadim
authors.initials: V
authors.lastname: Demidchik
authors.forename: Christopher
authors.initials: C
authors.lastname: Nichols
authors.forename: Julia M
authors.initials: JM
authors.lastname: Davies
mesh_terms: D000595:Amino Acid Sequence; D017302:Annexins / Q000737:chemistry / Q000378:metabolism; D015220:Calcium Channels / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D027682:Cation Transport Proteins; D002413:Cations, Divalent; D002462:Cell Membrane / Q000378:metabolism; D054815:Cyclic Nucleotide-Gated Cation Channels; D017343:Genes, Plant; D007473:Ion Channels / Q000378:metabolism; D008969:Molecular Sequence Data; D010940:Plant Proteins; D018517:Plant Roots / Q000166:cytology / Q000378:metabolism*; D015221:Potassium Channels / Q000145:classification / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D017302:Annexins; D015220:Calcium Channels; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D002413:Cations, Divalent; D054815:Cyclic Nucleotide-Gated Cation Channels; D007473:Ion Channels; C108683:LCT1 protein, Triticum aestivum; D010940:Plant Proteins; D015221:Potassium Channels