Molecular mechanisms and regulation of plant ion channels

have enlightened a large array of ion channels with highly divergent properties. These channels are present in various Plant ion channel activities are rapidly modulated in subcellular membranes, including the plasma membrane, response to several environmental and endogenous the tonoplast, plastidial and mitochondrial membranes, stimuli. Electrophysiological as well as pharmacoloand those of the endoplasmatic reticulum. Ion channels gical studies provide strong evidence that ion channels differ in terms of ion selectivity, rectification properties, are essential for the induction of specific cellular activation kinetics, and single channel conductances. responses and that they are themselves subject to Furthermore, they are subject to regulation by a variety regulation by a variety of cellular factors. Genes and of cellular factors, including second messengers, such as cDNAs of several plant ion channels have been identicytosolic calcium, pH, and nucleotides, and they interact fied in recent years giving access to molecular mechwith signalling proteins, which may include protein kinanisms of such regulatory processes. Cloned inwardly ases or phosphatases, cytoskeletal components, GTPrectifying potassium channels have been investigated binding proteins and 14-3-3 proteins (Schroeder and in various heterologous expression systems. Two other Hedrich, 1989; Blatt and Thiel, 1993; Nürnberger et al., ion channel classes, namely members of the ‘two-pore’ 1997; Zimmermann et al., 1999). K+ channel family as well as of the anion-conducting A major step forward towards the characterization of chloride channel (ClC) family, have been cloned, but plant ion channels was made by the molecular cloning of a direct link to corresponding plasma membrane or channel genes (or cDNAs), which was first reported in endomembrane ion channel conductances has not 1992. Employing a yeast complementation assay, two been demonstrated yet. Analysis of cellular expression groups independently isolated cDNAs for two types of patterns of plant ion channel genes in combination inwardly rectifying K+ channels ( KAT1, AKT1) from with transgenic approaches now gives access to a the model plant Arabidopsis thaliana (Anderson et al., detailed ex planta/in planta correlation of channel 1992; Sentenac et al., 1992). These cDNAs served as function, as has recently been demonstrated for prostarting material for the subsequent cloning of additional teins of the K+ in channel family. This review summarizes K+ channel genes from Arabidopsis, potato and other current knowledge on molecular structures and some plant species. The electrophysiological properties of the features of structure–function relationships of plant channels encoded by these genes were mostly analysed ion channels. via expression in non-green cells, including Xenopus laevis oocytes (Schachtman et al., 1992; Hoshi, 1995; Müller