The plant K+ channel KAT1 shows some similarity to animal voltage-gated channels of the Shaker superfamily. Contrary to these animal counterparts, this plant channel is inwardly rectifying, being gated upon hyperpolarization. Different levels of expression of KAT1 in Xenopus oocytes could be obtained by increasing the amount of injected cRNA. The resulting KAT1 gating and sensitivity to external caesium were significantly changed. Similar findings have been published regarding animal voltage-gated channels. The present data show that plant channels may also undergo modification of their activity upon modification of their level of expression.