Journal of Experimental Botany, Vol 50, 53-61, Copyright © 1999 by Oxford University Press
G Saalbach, G Natura, W Lein, P Buschmann, I Dahse, M Rohrbeck and F Nagy
Heterotrimeric GTPases (G-proteins) are implicated in many cellular
signalling processes. In plants, a function of a specific G-protein has
only recently been characterized. A cDNA clone encoding a G-protein
ARTICLES
The {alpha}-subunit of a heterotrimeric G-protein from tobacco, NtGP
1, functions in K+ channel regulation in mesophyll cells
Institute of Plant Genetics and Crop Plant Research, IPK, Corrensstrasse 3, D-06466 Gatersleben, Germany; Institute of Biochemistry and Biophysics, Friedrich-Schiller-University Jena, Philosophenweg 12, D-07743 Jena, Germany; Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, PO Box 521, H-6701 Szeged, Hungary; Present address: Riso National Laboratory, Plant and Biogeochemistry Department, Building 330, PO Box 49, DK-4000 Roskilde, Denmark; Corresponding author; Fax: +49 3641 949352; E-mail: b7dain@dagobert.rz.uni-jena.de
-subunit was isolated from tobacco
(Nicotiana tabacum L.). The deduced amino acid
sequence of this -subunit (NtGP1)
has 91% homology to GP1 from Arabidopsis
thaliana. Sequence comparisons with other plant G-proteins show
that these two -subunits belong to the only class of plant
G-proteins known to date. The NtGP1 cDNA was placed under the
control of the CaMV 35S promoter both in sense and antisense orientation.
These constructs were stably transformed into tobacco plants. As shown by
patch-clamp experiments, mesophyll protoplasts of transformed tobacco
plants over-expressing NtGP1 sense or antisense RNA exhibited
enhanced plasmalemma K+ conductances compared to the
wild type. By contrast, mesophyll protoplasts of transformed tobacco plants
expressing the cholera toxin A1-subunit, a G-protein activator, exhibited a
reduced plasmalemma K+ conductance. These results
indicate for the first time a role of a specific G-protein in the
regulation of K+ channels.Keywords:
G-protein, cloning, antisense, K+ channel
regulation, Nicotiana tabacum.
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