Functional expression and characterization of a plant K+ channel gene in a plant cell model.
To express and characterize the function of a plant ion channel gene in plant cells, it is necessary to establish a model system that lacks the endogenous channel activity and can be genetically transformed. Patch-clamp techniques were used to survey voltage-dependent K+ channel activities in different cell types of tobacco plants. Interestingly, mesophyll cells lacked the inward K+ current found in guard cells. A transgene containing the inward K+ channel gene KAT1 from Arabidopsis was constructed and expressed in the mesophyll cells of transgenic tobacco plants. Expression of the KAT1 gene produced a large voltage-dependent inward current across the plasma membrane of mesophyll protoplasts. The KAT1 current was carried by K+ and activated at voltage more negative than -100 mV. This K+ current had a single-channel conductance of 6-10 pS and was highly sensitive to TEA, Cs+ and Ba2+. This study represents the first example in which a plant ion channel gene is functionally expressed and studied in plant cells. Tobacco mesophyll cells will provide a useful model for functional characterization of inward K+ channel genes from higher plants.
Department of Plant and Microbial Biology, University of California, Berkeley 94720, USA.
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D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D017343:Genes, Plant; D017136:Ion Transport; D008564:Membrane Potentials; D008957:Models, Genetic; D018408:Patch-Clamp Techniques; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D015221:Potassium Channels / Q000235:genetics*; D011523:Protoplasts / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism
D015221:Potassium Channels