EXPRESSION, EVOLUTION AND GENOMIC COMPLEXITY OF POTASSIUM-ION CHANNELGENES OF ARABIDOPSIS-THALIANA

Potassium ion (K+) channels are of major importance in several functio nally diverse processes in plant physiology, including K+ transport, m embrane potential control, osmoregulation, and stomatal movement. In a nimals, K+ channels are encoded by multigene families and are differen tially expressed during development. Little is known about the genomic organisation, expression or evolution of plant K+ channels. We report here, the partial sequence of a putative K+ channel cDNA from Arabido psis (KAT2) showing sequence homology to previously identified voltage -gated K+ channel genes KAT1 and AKT1, and which hybridises to a singl e 2.1 kb mRNA in leaves. The existence of KAT2, together with numerous similar sequences identified by Southern blot analyses, suggest that K+ channels in Arabidopsis are encoded by multiple genes. Southern blo t data also suggest that KAT and AKT homologs are present in many othe r plant species. Analysis of the expression pattern of KAT1, KAT2 and AKT1 demonstrate a tissue-specific regulation of K+ channel genes in p lants.