Molecular mechanisms and regulation of plant ion channels

Plant ion channel activities are rapidly modulated in response to several e nvironmental and endogenous stimuli. Electrophysiological as well as pharma cological studies provide strong evidence that ion channels are essential f or the induction of specific cellular responses and that they are themselve s subject to regulation by a variety of cellular factors. Genes anal cDNAs of several plant ion channels have been identified in recent years giving a ccess to molecular mechanisms of such regulatory processes. Cloned inwardly rectifying potassium channels have been investigated in various heterologo us expression systems. Two other ion channel classes, namely members of the 'two-pore' K+ channel family as well as of the anion-conducting chloride c hannel (CIC) family, have been cloned, but a direct link to corresponding p lasma membrane or endomembrane ion channel conductances has not been demons trated yet. Analysis of cellular expression patterns of plant ion channel g enes in combination with transgenic approaches now gives access to a detail ed ex planta/in planta correlation of channel function, as has recently bee n demonstrated for proteins of the K-in(+) channel family. This review summ arizes current knowledge on molecular structures and some features of struc ture-function relationships of plant ion channels.